The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_subr.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)tcp_subr.c  8.2 (Berkeley) 5/24/95
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/10.2/sys/netinet/tcp_subr.c 285978 2015-07-28 19:59:04Z delphij $");
   34 
   35 #include "opt_compat.h"
   36 #include "opt_inet.h"
   37 #include "opt_inet6.h"
   38 #include "opt_ipsec.h"
   39 #include "opt_kdtrace.h"
   40 #include "opt_tcpdebug.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/callout.h>
   45 #include <sys/hhook.h>
   46 #include <sys/kernel.h>
   47 #include <sys/khelp.h>
   48 #include <sys/sysctl.h>
   49 #include <sys/jail.h>
   50 #include <sys/malloc.h>
   51 #include <sys/mbuf.h>
   52 #ifdef INET6
   53 #include <sys/domain.h>
   54 #endif
   55 #include <sys/priv.h>
   56 #include <sys/proc.h>
   57 #include <sys/sdt.h>
   58 #include <sys/socket.h>
   59 #include <sys/socketvar.h>
   60 #include <sys/protosw.h>
   61 #include <sys/random.h>
   62 
   63 #include <vm/uma.h>
   64 
   65 #include <net/route.h>
   66 #include <net/if.h>
   67 #include <net/vnet.h>
   68 
   69 #include <netinet/cc.h>
   70 #include <netinet/in.h>
   71 #include <netinet/in_kdtrace.h>
   72 #include <netinet/in_pcb.h>
   73 #include <netinet/in_systm.h>
   74 #include <netinet/in_var.h>
   75 #include <netinet/ip.h>
   76 #include <netinet/ip_icmp.h>
   77 #include <netinet/ip_var.h>
   78 #ifdef INET6
   79 #include <netinet/ip6.h>
   80 #include <netinet6/in6_pcb.h>
   81 #include <netinet6/ip6_var.h>
   82 #include <netinet6/scope6_var.h>
   83 #include <netinet6/nd6.h>
   84 #endif
   85 
   86 #include <netinet/tcp_fsm.h>
   87 #include <netinet/tcp_seq.h>
   88 #include <netinet/tcp_timer.h>
   89 #include <netinet/tcp_var.h>
   90 #include <netinet/tcp_syncache.h>
   91 #ifdef INET6
   92 #include <netinet6/tcp6_var.h>
   93 #endif
   94 #include <netinet/tcpip.h>
   95 #ifdef TCPDEBUG
   96 #include <netinet/tcp_debug.h>
   97 #endif
   98 #ifdef INET6
   99 #include <netinet6/ip6protosw.h>
  100 #endif
  101 #ifdef TCP_OFFLOAD
  102 #include <netinet/tcp_offload.h>
  103 #endif
  104 
  105 #ifdef IPSEC
  106 #include <netipsec/ipsec.h>
  107 #include <netipsec/xform.h>
  108 #ifdef INET6
  109 #include <netipsec/ipsec6.h>
  110 #endif
  111 #include <netipsec/key.h>
  112 #include <sys/syslog.h>
  113 #endif /*IPSEC*/
  114 
  115 #include <machine/in_cksum.h>
  116 #include <sys/md5.h>
  117 
  118 #include <security/mac/mac_framework.h>
  119 
  120 VNET_DEFINE(int, tcp_mssdflt) = TCP_MSS;
  121 #ifdef INET6
  122 VNET_DEFINE(int, tcp_v6mssdflt) = TCP6_MSS;
  123 #endif
  124 
  125 static int
  126 sysctl_net_inet_tcp_mss_check(SYSCTL_HANDLER_ARGS)
  127 {
  128         int error, new;
  129 
  130         new = V_tcp_mssdflt;
  131         error = sysctl_handle_int(oidp, &new, 0, req);
  132         if (error == 0 && req->newptr) {
  133                 if (new < TCP_MINMSS)
  134                         error = EINVAL;
  135                 else
  136                         V_tcp_mssdflt = new;
  137         }
  138         return (error);
  139 }
  140 
  141 SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,
  142     CTLTYPE_INT|CTLFLAG_RW, &VNET_NAME(tcp_mssdflt), 0,
  143     &sysctl_net_inet_tcp_mss_check, "I",
  144     "Default TCP Maximum Segment Size");
  145 
  146 #ifdef INET6
  147 static int
  148 sysctl_net_inet_tcp_mss_v6_check(SYSCTL_HANDLER_ARGS)
  149 {
  150         int error, new;
  151 
  152         new = V_tcp_v6mssdflt;
  153         error = sysctl_handle_int(oidp, &new, 0, req);
  154         if (error == 0 && req->newptr) {
  155                 if (new < TCP_MINMSS)
  156                         error = EINVAL;
  157                 else
  158                         V_tcp_v6mssdflt = new;
  159         }
  160         return (error);
  161 }
  162 
  163 SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
  164     CTLTYPE_INT|CTLFLAG_RW, &VNET_NAME(tcp_v6mssdflt), 0,
  165     &sysctl_net_inet_tcp_mss_v6_check, "I",
  166    "Default TCP Maximum Segment Size for IPv6");
  167 #endif /* INET6 */
  168 
  169 /*
  170  * Minimum MSS we accept and use. This prevents DoS attacks where
  171  * we are forced to a ridiculous low MSS like 20 and send hundreds
  172  * of packets instead of one. The effect scales with the available
  173  * bandwidth and quickly saturates the CPU and network interface
  174  * with packet generation and sending. Set to zero to disable MINMSS
  175  * checking. This setting prevents us from sending too small packets.
  176  */
  177 VNET_DEFINE(int, tcp_minmss) = TCP_MINMSS;
  178 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_RW,
  179      &VNET_NAME(tcp_minmss), 0,
  180     "Minimum TCP Maximum Segment Size");
  181 
  182 VNET_DEFINE(int, tcp_do_rfc1323) = 1;
  183 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
  184     &VNET_NAME(tcp_do_rfc1323), 0,
  185     "Enable rfc1323 (high performance TCP) extensions");
  186 
  187 static int      tcp_log_debug = 0;
  188 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
  189     &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
  190 
  191 static int      tcp_tcbhashsize = 0;
  192 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
  193     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
  194 
  195 static int      do_tcpdrain = 1;
  196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
  197     "Enable tcp_drain routine for extra help when low on mbufs");
  198 
  199 SYSCTL_VNET_UINT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
  200     &VNET_NAME(tcbinfo.ipi_count), 0, "Number of active PCBs");
  201 
  202 static VNET_DEFINE(int, icmp_may_rst) = 1;
  203 #define V_icmp_may_rst                  VNET(icmp_may_rst)
  204 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW,
  205     &VNET_NAME(icmp_may_rst), 0,
  206     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
  207 
  208 static VNET_DEFINE(int, tcp_isn_reseed_interval) = 0;
  209 #define V_tcp_isn_reseed_interval       VNET(tcp_isn_reseed_interval)
  210 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW,
  211     &VNET_NAME(tcp_isn_reseed_interval), 0,
  212     "Seconds between reseeding of ISN secret");
  213 
  214 static int      tcp_soreceive_stream = 0;
  215 SYSCTL_INT(_net_inet_tcp, OID_AUTO, soreceive_stream, CTLFLAG_RDTUN,
  216     &tcp_soreceive_stream, 0, "Using soreceive_stream for TCP sockets");
  217 
  218 #ifdef TCP_SIGNATURE
  219 static int      tcp_sig_checksigs = 1;
  220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, signature_verify_input, CTLFLAG_RW,
  221     &tcp_sig_checksigs, 0, "Verify RFC2385 digests on inbound traffic");
  222 #endif
  223 
  224 VNET_DEFINE(uma_zone_t, sack_hole_zone);
  225 #define V_sack_hole_zone                VNET(sack_hole_zone)
  226 
  227 VNET_DEFINE(struct hhook_head *, tcp_hhh[HHOOK_TCP_LAST+1]);
  228 
  229 static struct inpcb *tcp_notify(struct inpcb *, int);
  230 static struct inpcb *tcp_mtudisc_notify(struct inpcb *, int);
  231 static char *   tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th,
  232                     void *ip4hdr, const void *ip6hdr);
  233 static void     tcp_timer_discard(struct tcpcb *, uint32_t);
  234 
  235 /*
  236  * Target size of TCP PCB hash tables. Must be a power of two.
  237  *
  238  * Note that this can be overridden by the kernel environment
  239  * variable net.inet.tcp.tcbhashsize
  240  */
  241 #ifndef TCBHASHSIZE
  242 #define TCBHASHSIZE     0
  243 #endif
  244 
  245 /*
  246  * XXX
  247  * Callouts should be moved into struct tcp directly.  They are currently
  248  * separate because the tcpcb structure is exported to userland for sysctl
  249  * parsing purposes, which do not know about callouts.
  250  */
  251 struct tcpcb_mem {
  252         struct  tcpcb           tcb;
  253         struct  tcp_timer       tt;
  254         struct  cc_var          ccv;
  255         struct  osd             osd;
  256 };
  257 
  258 static VNET_DEFINE(uma_zone_t, tcpcb_zone);
  259 #define V_tcpcb_zone                    VNET(tcpcb_zone)
  260 
  261 MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
  262 static struct mtx isn_mtx;
  263 
  264 #define ISN_LOCK_INIT() mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
  265 #define ISN_LOCK()      mtx_lock(&isn_mtx)
  266 #define ISN_UNLOCK()    mtx_unlock(&isn_mtx)
  267 
  268 /*
  269  * TCP initialization.
  270  */
  271 static void
  272 tcp_zone_change(void *tag)
  273 {
  274 
  275         uma_zone_set_max(V_tcbinfo.ipi_zone, maxsockets);
  276         uma_zone_set_max(V_tcpcb_zone, maxsockets);
  277         tcp_tw_zone_change();
  278 }
  279 
  280 static int
  281 tcp_inpcb_init(void *mem, int size, int flags)
  282 {
  283         struct inpcb *inp = mem;
  284 
  285         INP_LOCK_INIT(inp, "inp", "tcpinp");
  286         return (0);
  287 }
  288 
  289 /*
  290  * Take a value and get the next power of 2 that doesn't overflow.
  291  * Used to size the tcp_inpcb hash buckets.
  292  */
  293 static int
  294 maketcp_hashsize(int size)
  295 {
  296         int hashsize;
  297 
  298         /*
  299          * auto tune.
  300          * get the next power of 2 higher than maxsockets.
  301          */
  302         hashsize = 1 << fls(size);
  303         /* catch overflow, and just go one power of 2 smaller */
  304         if (hashsize < size) {
  305                 hashsize = 1 << (fls(size) - 1);
  306         }
  307         return (hashsize);
  308 }
  309 
  310 void
  311 tcp_init(void)
  312 {
  313         const char *tcbhash_tuneable;
  314         int hashsize;
  315 
  316         tcbhash_tuneable = "net.inet.tcp.tcbhashsize";
  317 
  318         if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_IN,
  319             &V_tcp_hhh[HHOOK_TCP_EST_IN], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
  320                 printf("%s: WARNING: unable to register helper hook\n", __func__);
  321         if (hhook_head_register(HHOOK_TYPE_TCP, HHOOK_TCP_EST_OUT,
  322             &V_tcp_hhh[HHOOK_TCP_EST_OUT], HHOOK_NOWAIT|HHOOK_HEADISINVNET) != 0)
  323                 printf("%s: WARNING: unable to register helper hook\n", __func__);
  324 
  325         hashsize = TCBHASHSIZE;
  326         TUNABLE_INT_FETCH(tcbhash_tuneable, &hashsize);
  327         if (hashsize == 0) {
  328                 /*
  329                  * Auto tune the hash size based on maxsockets.
  330                  * A perfect hash would have a 1:1 mapping
  331                  * (hashsize = maxsockets) however it's been
  332                  * suggested that O(2) average is better.
  333                  */
  334                 hashsize = maketcp_hashsize(maxsockets / 4);
  335                 /*
  336                  * Our historical default is 512,
  337                  * do not autotune lower than this.
  338                  */
  339                 if (hashsize < 512)
  340                         hashsize = 512;
  341                 if (bootverbose)
  342                         printf("%s: %s auto tuned to %d\n", __func__,
  343                             tcbhash_tuneable, hashsize);
  344         }
  345         /*
  346          * We require a hashsize to be a power of two.
  347          * Previously if it was not a power of two we would just reset it
  348          * back to 512, which could be a nasty surprise if you did not notice
  349          * the error message.
  350          * Instead what we do is clip it to the closest power of two lower
  351          * than the specified hash value.
  352          */
  353         if (!powerof2(hashsize)) {
  354                 int oldhashsize = hashsize;
  355 
  356                 hashsize = maketcp_hashsize(hashsize);
  357                 /* prevent absurdly low value */
  358                 if (hashsize < 16)
  359                         hashsize = 16;
  360                 printf("%s: WARNING: TCB hash size not a power of 2, "
  361                     "clipped from %d to %d.\n", __func__, oldhashsize,
  362                     hashsize);
  363         }
  364         in_pcbinfo_init(&V_tcbinfo, "tcp", &V_tcb, hashsize, hashsize,
  365             "tcp_inpcb", tcp_inpcb_init, NULL, UMA_ZONE_NOFREE,
  366             IPI_HASHFIELDS_4TUPLE);
  367 
  368         /*
  369          * These have to be type stable for the benefit of the timers.
  370          */
  371         V_tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
  372             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  373         uma_zone_set_max(V_tcpcb_zone, maxsockets);
  374         uma_zone_set_warning(V_tcpcb_zone, "kern.ipc.maxsockets limit reached");
  375 
  376         tcp_tw_init();
  377         syncache_init();
  378         tcp_hc_init();
  379 
  380         TUNABLE_INT_FETCH("net.inet.tcp.sack.enable", &V_tcp_do_sack);
  381         V_sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
  382             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  383 
  384         /* Skip initialization of globals for non-default instances. */
  385         if (!IS_DEFAULT_VNET(curvnet))
  386                 return;
  387 
  388         tcp_reass_global_init();
  389 
  390         /* XXX virtualize those bellow? */
  391         tcp_delacktime = TCPTV_DELACK;
  392         tcp_keepinit = TCPTV_KEEP_INIT;
  393         tcp_keepidle = TCPTV_KEEP_IDLE;
  394         tcp_keepintvl = TCPTV_KEEPINTVL;
  395         tcp_maxpersistidle = TCPTV_KEEP_IDLE;
  396         tcp_msl = TCPTV_MSL;
  397         tcp_rexmit_min = TCPTV_MIN;
  398         if (tcp_rexmit_min < 1)
  399                 tcp_rexmit_min = 1;
  400         tcp_rexmit_slop = TCPTV_CPU_VAR;
  401         tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
  402         tcp_tcbhashsize = hashsize;
  403 
  404         TUNABLE_INT_FETCH("net.inet.tcp.soreceive_stream", &tcp_soreceive_stream);
  405         if (tcp_soreceive_stream) {
  406 #ifdef INET
  407                 tcp_usrreqs.pru_soreceive = soreceive_stream;
  408 #endif
  409 #ifdef INET6
  410                 tcp6_usrreqs.pru_soreceive = soreceive_stream;
  411 #endif /* INET6 */
  412         }
  413 
  414 #ifdef INET6
  415 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
  416 #else /* INET6 */
  417 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
  418 #endif /* INET6 */
  419         if (max_protohdr < TCP_MINPROTOHDR)
  420                 max_protohdr = TCP_MINPROTOHDR;
  421         if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
  422                 panic("tcp_init");
  423 #undef TCP_MINPROTOHDR
  424 
  425         ISN_LOCK_INIT();
  426         EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
  427                 SHUTDOWN_PRI_DEFAULT);
  428         EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
  429                 EVENTHANDLER_PRI_ANY);
  430 }
  431 
  432 #ifdef VIMAGE
  433 void
  434 tcp_destroy(void)
  435 {
  436 
  437         tcp_hc_destroy();
  438         syncache_destroy();
  439         tcp_tw_destroy();
  440         in_pcbinfo_destroy(&V_tcbinfo);
  441         uma_zdestroy(V_sack_hole_zone);
  442         uma_zdestroy(V_tcpcb_zone);
  443 }
  444 #endif
  445 
  446 void
  447 tcp_fini(void *xtp)
  448 {
  449 
  450 }
  451 
  452 /*
  453  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
  454  * tcp_template used to store this data in mbufs, but we now recopy it out
  455  * of the tcpcb each time to conserve mbufs.
  456  */
  457 void
  458 tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
  459 {
  460         struct tcphdr *th = (struct tcphdr *)tcp_ptr;
  461 
  462         INP_WLOCK_ASSERT(inp);
  463 
  464 #ifdef INET6
  465         if ((inp->inp_vflag & INP_IPV6) != 0) {
  466                 struct ip6_hdr *ip6;
  467 
  468                 ip6 = (struct ip6_hdr *)ip_ptr;
  469                 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
  470                         (inp->inp_flow & IPV6_FLOWINFO_MASK);
  471                 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
  472                         (IPV6_VERSION & IPV6_VERSION_MASK);
  473                 ip6->ip6_nxt = IPPROTO_TCP;
  474                 ip6->ip6_plen = htons(sizeof(struct tcphdr));
  475                 ip6->ip6_src = inp->in6p_laddr;
  476                 ip6->ip6_dst = inp->in6p_faddr;
  477         }
  478 #endif /* INET6 */
  479 #if defined(INET6) && defined(INET)
  480         else
  481 #endif
  482 #ifdef INET
  483         {
  484                 struct ip *ip;
  485 
  486                 ip = (struct ip *)ip_ptr;
  487                 ip->ip_v = IPVERSION;
  488                 ip->ip_hl = 5;
  489                 ip->ip_tos = inp->inp_ip_tos;
  490                 ip->ip_len = 0;
  491                 ip->ip_id = 0;
  492                 ip->ip_off = 0;
  493                 ip->ip_ttl = inp->inp_ip_ttl;
  494                 ip->ip_sum = 0;
  495                 ip->ip_p = IPPROTO_TCP;
  496                 ip->ip_src = inp->inp_laddr;
  497                 ip->ip_dst = inp->inp_faddr;
  498         }
  499 #endif /* INET */
  500         th->th_sport = inp->inp_lport;
  501         th->th_dport = inp->inp_fport;
  502         th->th_seq = 0;
  503         th->th_ack = 0;
  504         th->th_x2 = 0;
  505         th->th_off = 5;
  506         th->th_flags = 0;
  507         th->th_win = 0;
  508         th->th_urp = 0;
  509         th->th_sum = 0;         /* in_pseudo() is called later for ipv4 */
  510 }
  511 
  512 /*
  513  * Create template to be used to send tcp packets on a connection.
  514  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
  515  * use for this function is in keepalives, which use tcp_respond.
  516  */
  517 struct tcptemp *
  518 tcpip_maketemplate(struct inpcb *inp)
  519 {
  520         struct tcptemp *t;
  521 
  522         t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
  523         if (t == NULL)
  524                 return (NULL);
  525         tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
  526         return (t);
  527 }
  528 
  529 /*
  530  * Send a single message to the TCP at address specified by
  531  * the given TCP/IP header.  If m == NULL, then we make a copy
  532  * of the tcpiphdr at ti and send directly to the addressed host.
  533  * This is used to force keep alive messages out using the TCP
  534  * template for a connection.  If flags are given then we send
  535  * a message back to the TCP which originated the * segment ti,
  536  * and discard the mbuf containing it and any other attached mbufs.
  537  *
  538  * In any case the ack and sequence number of the transmitted
  539  * segment are as specified by the parameters.
  540  *
  541  * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
  542  */
  543 void
  544 tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
  545     tcp_seq ack, tcp_seq seq, int flags)
  546 {
  547         int tlen;
  548         int win = 0;
  549         struct ip *ip;
  550         struct tcphdr *nth;
  551 #ifdef INET6
  552         struct ip6_hdr *ip6;
  553         int isipv6;
  554 #endif /* INET6 */
  555         int ipflags = 0;
  556         struct inpcb *inp;
  557 
  558         KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
  559 
  560 #ifdef INET6
  561         isipv6 = ((struct ip *)ipgen)->ip_v == (IPV6_VERSION >> 4);
  562         ip6 = ipgen;
  563 #endif /* INET6 */
  564         ip = ipgen;
  565 
  566         if (tp != NULL) {
  567                 inp = tp->t_inpcb;
  568                 KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
  569                 INP_WLOCK_ASSERT(inp);
  570         } else
  571                 inp = NULL;
  572 
  573         if (tp != NULL) {
  574                 if (!(flags & TH_RST)) {
  575                         win = sbspace(&inp->inp_socket->so_rcv);
  576                         if (win > (long)TCP_MAXWIN << tp->rcv_scale)
  577                                 win = (long)TCP_MAXWIN << tp->rcv_scale;
  578                 }
  579         }
  580         if (m == NULL) {
  581                 m = m_gethdr(M_NOWAIT, MT_DATA);
  582                 if (m == NULL)
  583                         return;
  584                 tlen = 0;
  585                 m->m_data += max_linkhdr;
  586 #ifdef INET6
  587                 if (isipv6) {
  588                         bcopy((caddr_t)ip6, mtod(m, caddr_t),
  589                               sizeof(struct ip6_hdr));
  590                         ip6 = mtod(m, struct ip6_hdr *);
  591                         nth = (struct tcphdr *)(ip6 + 1);
  592                 } else
  593 #endif /* INET6 */
  594                 {
  595                         bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
  596                         ip = mtod(m, struct ip *);
  597                         nth = (struct tcphdr *)(ip + 1);
  598                 }
  599                 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
  600                 flags = TH_ACK;
  601         } else {
  602                 /*
  603                  *  reuse the mbuf. 
  604                  * XXX MRT We inherrit the FIB, which is lucky.
  605                  */
  606                 m_freem(m->m_next);
  607                 m->m_next = NULL;
  608                 m->m_data = (caddr_t)ipgen;
  609                 /* m_len is set later */
  610                 tlen = 0;
  611 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
  612 #ifdef INET6
  613                 if (isipv6) {
  614                         xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
  615                         nth = (struct tcphdr *)(ip6 + 1);
  616                 } else
  617 #endif /* INET6 */
  618                 {
  619                         xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
  620                         nth = (struct tcphdr *)(ip + 1);
  621                 }
  622                 if (th != nth) {
  623                         /*
  624                          * this is usually a case when an extension header
  625                          * exists between the IPv6 header and the
  626                          * TCP header.
  627                          */
  628                         nth->th_sport = th->th_sport;
  629                         nth->th_dport = th->th_dport;
  630                 }
  631                 xchg(nth->th_dport, nth->th_sport, uint16_t);
  632 #undef xchg
  633         }
  634 #ifdef INET6
  635         if (isipv6) {
  636                 ip6->ip6_flow = 0;
  637                 ip6->ip6_vfc = IPV6_VERSION;
  638                 ip6->ip6_nxt = IPPROTO_TCP;
  639                 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
  640                 ip6->ip6_plen = htons(tlen - sizeof(*ip6));
  641         }
  642 #endif
  643 #if defined(INET) && defined(INET6)
  644         else
  645 #endif
  646 #ifdef INET
  647         {
  648                 tlen += sizeof (struct tcpiphdr);
  649                 ip->ip_len = htons(tlen);
  650                 ip->ip_ttl = V_ip_defttl;
  651                 if (V_path_mtu_discovery)
  652                         ip->ip_off |= htons(IP_DF);
  653         }
  654 #endif
  655         m->m_len = tlen;
  656         m->m_pkthdr.len = tlen;
  657         m->m_pkthdr.rcvif = NULL;
  658 #ifdef MAC
  659         if (inp != NULL) {
  660                 /*
  661                  * Packet is associated with a socket, so allow the
  662                  * label of the response to reflect the socket label.
  663                  */
  664                 INP_WLOCK_ASSERT(inp);
  665                 mac_inpcb_create_mbuf(inp, m);
  666         } else {
  667                 /*
  668                  * Packet is not associated with a socket, so possibly
  669                  * update the label in place.
  670                  */
  671                 mac_netinet_tcp_reply(m);
  672         }
  673 #endif
  674         nth->th_seq = htonl(seq);
  675         nth->th_ack = htonl(ack);
  676         nth->th_x2 = 0;
  677         nth->th_off = sizeof (struct tcphdr) >> 2;
  678         nth->th_flags = flags;
  679         if (tp != NULL)
  680                 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
  681         else
  682                 nth->th_win = htons((u_short)win);
  683         nth->th_urp = 0;
  684 
  685         m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
  686 #ifdef INET6
  687         if (isipv6) {
  688                 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
  689                 nth->th_sum = in6_cksum_pseudo(ip6,
  690                     tlen - sizeof(struct ip6_hdr), IPPROTO_TCP, 0);
  691                 ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
  692                     NULL, NULL);
  693         }
  694 #endif /* INET6 */
  695 #if defined(INET6) && defined(INET)
  696         else
  697 #endif
  698 #ifdef INET
  699         {
  700                 m->m_pkthdr.csum_flags = CSUM_TCP;
  701                 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
  702                     htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
  703         }
  704 #endif /* INET */
  705 #ifdef TCPDEBUG
  706         if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
  707                 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
  708 #endif
  709         if (flags & TH_RST)
  710                 TCP_PROBE5(accept__refused, NULL, NULL, mtod(m, const char *),
  711                     tp, nth);
  712 
  713         TCP_PROBE5(send, NULL, tp, mtod(m, const char *), tp, nth);
  714 #ifdef INET6
  715         if (isipv6)
  716                 (void) ip6_output(m, NULL, NULL, ipflags, NULL, NULL, inp);
  717 #endif /* INET6 */
  718 #if defined(INET) && defined(INET6)
  719         else
  720 #endif
  721 #ifdef INET
  722                 (void) ip_output(m, NULL, NULL, ipflags, NULL, inp);
  723 #endif
  724 }
  725 
  726 /*
  727  * Create a new TCP control block, making an
  728  * empty reassembly queue and hooking it to the argument
  729  * protocol control block.  The `inp' parameter must have
  730  * come from the zone allocator set up in tcp_init().
  731  */
  732 struct tcpcb *
  733 tcp_newtcpcb(struct inpcb *inp)
  734 {
  735         struct tcpcb_mem *tm;
  736         struct tcpcb *tp;
  737 #ifdef INET6
  738         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  739 #endif /* INET6 */
  740 
  741         tm = uma_zalloc(V_tcpcb_zone, M_NOWAIT | M_ZERO);
  742         if (tm == NULL)
  743                 return (NULL);
  744         tp = &tm->tcb;
  745 
  746         /* Initialise cc_var struct for this tcpcb. */
  747         tp->ccv = &tm->ccv;
  748         tp->ccv->type = IPPROTO_TCP;
  749         tp->ccv->ccvc.tcp = tp;
  750 
  751         /*
  752          * Use the current system default CC algorithm.
  753          */
  754         CC_LIST_RLOCK();
  755         KASSERT(!STAILQ_EMPTY(&cc_list), ("cc_list is empty!"));
  756         CC_ALGO(tp) = CC_DEFAULT();
  757         CC_LIST_RUNLOCK();
  758 
  759         if (CC_ALGO(tp)->cb_init != NULL)
  760                 if (CC_ALGO(tp)->cb_init(tp->ccv) > 0) {
  761                         uma_zfree(V_tcpcb_zone, tm);
  762                         return (NULL);
  763                 }
  764 
  765         tp->osd = &tm->osd;
  766         if (khelp_init_osd(HELPER_CLASS_TCP, tp->osd)) {
  767                 uma_zfree(V_tcpcb_zone, tm);
  768                 return (NULL);
  769         }
  770 
  771 #ifdef VIMAGE
  772         tp->t_vnet = inp->inp_vnet;
  773 #endif
  774         tp->t_timers = &tm->tt;
  775         /*      LIST_INIT(&tp->t_segq); */      /* XXX covered by M_ZERO */
  776         tp->t_maxseg = tp->t_maxopd =
  777 #ifdef INET6
  778                 isipv6 ? V_tcp_v6mssdflt :
  779 #endif /* INET6 */
  780                 V_tcp_mssdflt;
  781 
  782         /* Set up our timeouts. */
  783         callout_init(&tp->t_timers->tt_rexmt, CALLOUT_MPSAFE);
  784         callout_init(&tp->t_timers->tt_persist, CALLOUT_MPSAFE);
  785         callout_init(&tp->t_timers->tt_keep, CALLOUT_MPSAFE);
  786         callout_init(&tp->t_timers->tt_2msl, CALLOUT_MPSAFE);
  787         callout_init(&tp->t_timers->tt_delack, CALLOUT_MPSAFE);
  788 
  789         if (V_tcp_do_rfc1323)
  790                 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
  791         if (V_tcp_do_sack)
  792                 tp->t_flags |= TF_SACK_PERMIT;
  793         TAILQ_INIT(&tp->snd_holes);
  794         /*
  795          * The tcpcb will hold a reference on its inpcb until tcp_discardcb()
  796          * is called.
  797          */
  798         in_pcbref(inp); /* Reference for tcpcb */
  799         tp->t_inpcb = inp;
  800 
  801         /*
  802          * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
  803          * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
  804          * reasonable initial retransmit time.
  805          */
  806         tp->t_srtt = TCPTV_SRTTBASE;
  807         tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
  808         tp->t_rttmin = tcp_rexmit_min;
  809         tp->t_rxtcur = TCPTV_RTOBASE;
  810         tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  811         tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  812         tp->t_rcvtime = ticks;
  813         /*
  814          * IPv4 TTL initialization is necessary for an IPv6 socket as well,
  815          * because the socket may be bound to an IPv6 wildcard address,
  816          * which may match an IPv4-mapped IPv6 address.
  817          */
  818         inp->inp_ip_ttl = V_ip_defttl;
  819         inp->inp_ppcb = tp;
  820         return (tp);            /* XXX */
  821 }
  822 
  823 /*
  824  * Switch the congestion control algorithm back to NewReno for any active
  825  * control blocks using an algorithm which is about to go away.
  826  * This ensures the CC framework can allow the unload to proceed without leaving
  827  * any dangling pointers which would trigger a panic.
  828  * Returning non-zero would inform the CC framework that something went wrong
  829  * and it would be unsafe to allow the unload to proceed. However, there is no
  830  * way for this to occur with this implementation so we always return zero.
  831  */
  832 int
  833 tcp_ccalgounload(struct cc_algo *unload_algo)
  834 {
  835         struct cc_algo *tmpalgo;
  836         struct inpcb *inp;
  837         struct tcpcb *tp;
  838         VNET_ITERATOR_DECL(vnet_iter);
  839 
  840         /*
  841          * Check all active control blocks across all network stacks and change
  842          * any that are using "unload_algo" back to NewReno. If "unload_algo"
  843          * requires cleanup code to be run, call it.
  844          */
  845         VNET_LIST_RLOCK();
  846         VNET_FOREACH(vnet_iter) {
  847                 CURVNET_SET(vnet_iter);
  848                 INP_INFO_RLOCK(&V_tcbinfo);
  849                 /*
  850                  * New connections already part way through being initialised
  851                  * with the CC algo we're removing will not race with this code
  852                  * because the INP_INFO_WLOCK is held during initialisation. We
  853                  * therefore don't enter the loop below until the connection
  854                  * list has stabilised.
  855                  */
  856                 LIST_FOREACH(inp, &V_tcb, inp_list) {
  857                         INP_WLOCK(inp);
  858                         /* Important to skip tcptw structs. */
  859                         if (!(inp->inp_flags & INP_TIMEWAIT) &&
  860                             (tp = intotcpcb(inp)) != NULL) {
  861                                 /*
  862                                  * By holding INP_WLOCK here, we are assured
  863                                  * that the connection is not currently
  864                                  * executing inside the CC module's functions
  865                                  * i.e. it is safe to make the switch back to
  866                                  * NewReno.
  867                                  */
  868                                 if (CC_ALGO(tp) == unload_algo) {
  869                                         tmpalgo = CC_ALGO(tp);
  870                                         /* NewReno does not require any init. */
  871                                         CC_ALGO(tp) = &newreno_cc_algo;
  872                                         if (tmpalgo->cb_destroy != NULL)
  873                                                 tmpalgo->cb_destroy(tp->ccv);
  874                                 }
  875                         }
  876                         INP_WUNLOCK(inp);
  877                 }
  878                 INP_INFO_RUNLOCK(&V_tcbinfo);
  879                 CURVNET_RESTORE();
  880         }
  881         VNET_LIST_RUNLOCK();
  882 
  883         return (0);
  884 }
  885 
  886 /*
  887  * Drop a TCP connection, reporting
  888  * the specified error.  If connection is synchronized,
  889  * then send a RST to peer.
  890  */
  891 struct tcpcb *
  892 tcp_drop(struct tcpcb *tp, int errno)
  893 {
  894         struct socket *so = tp->t_inpcb->inp_socket;
  895 
  896         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
  897         INP_WLOCK_ASSERT(tp->t_inpcb);
  898 
  899         if (TCPS_HAVERCVDSYN(tp->t_state)) {
  900                 tcp_state_change(tp, TCPS_CLOSED);
  901                 (void) tcp_output(tp);
  902                 TCPSTAT_INC(tcps_drops);
  903         } else
  904                 TCPSTAT_INC(tcps_conndrops);
  905         if (errno == ETIMEDOUT && tp->t_softerror)
  906                 errno = tp->t_softerror;
  907         so->so_error = errno;
  908         return (tcp_close(tp));
  909 }
  910 
  911 void
  912 tcp_discardcb(struct tcpcb *tp)
  913 {
  914         struct inpcb *inp = tp->t_inpcb;
  915         struct socket *so = inp->inp_socket;
  916 #ifdef INET6
  917         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  918 #endif /* INET6 */
  919         int released;
  920 
  921         INP_WLOCK_ASSERT(inp);
  922 
  923         /*
  924          * Make sure that all of our timers are stopped before we delete the
  925          * PCB.
  926          *
  927          * If stopping a timer fails, we schedule a discard function in same
  928          * callout, and the last discard function called will take care of
  929          * deleting the tcpcb.
  930          */
  931         tcp_timer_stop(tp, TT_REXMT);
  932         tcp_timer_stop(tp, TT_PERSIST);
  933         tcp_timer_stop(tp, TT_KEEP);
  934         tcp_timer_stop(tp, TT_2MSL);
  935         tcp_timer_stop(tp, TT_DELACK);
  936 
  937         /*
  938          * If we got enough samples through the srtt filter,
  939          * save the rtt and rttvar in the routing entry.
  940          * 'Enough' is arbitrarily defined as 4 rtt samples.
  941          * 4 samples is enough for the srtt filter to converge
  942          * to within enough % of the correct value; fewer samples
  943          * and we could save a bogus rtt. The danger is not high
  944          * as tcp quickly recovers from everything.
  945          * XXX: Works very well but needs some more statistics!
  946          */
  947         if (tp->t_rttupdated >= 4) {
  948                 struct hc_metrics_lite metrics;
  949                 u_long ssthresh;
  950 
  951                 bzero(&metrics, sizeof(metrics));
  952                 /*
  953                  * Update the ssthresh always when the conditions below
  954                  * are satisfied. This gives us better new start value
  955                  * for the congestion avoidance for new connections.
  956                  * ssthresh is only set if packet loss occured on a session.
  957                  *
  958                  * XXXRW: 'so' may be NULL here, and/or socket buffer may be
  959                  * being torn down.  Ideally this code would not use 'so'.
  960                  */
  961                 ssthresh = tp->snd_ssthresh;
  962                 if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
  963                         /*
  964                          * convert the limit from user data bytes to
  965                          * packets then to packet data bytes.
  966                          */
  967                         ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
  968                         if (ssthresh < 2)
  969                                 ssthresh = 2;
  970                         ssthresh *= (u_long)(tp->t_maxseg +
  971 #ifdef INET6
  972                             (isipv6 ? sizeof (struct ip6_hdr) +
  973                                 sizeof (struct tcphdr) :
  974 #endif
  975                                 sizeof (struct tcpiphdr)
  976 #ifdef INET6
  977                             )
  978 #endif
  979                             );
  980                 } else
  981                         ssthresh = 0;
  982                 metrics.rmx_ssthresh = ssthresh;
  983 
  984                 metrics.rmx_rtt = tp->t_srtt;
  985                 metrics.rmx_rttvar = tp->t_rttvar;
  986                 metrics.rmx_cwnd = tp->snd_cwnd;
  987                 metrics.rmx_sendpipe = 0;
  988                 metrics.rmx_recvpipe = 0;
  989 
  990                 tcp_hc_update(&inp->inp_inc, &metrics);
  991         }
  992 
  993         /* free the reassembly queue, if any */
  994         tcp_reass_flush(tp);
  995 
  996 #ifdef TCP_OFFLOAD
  997         /* Disconnect offload device, if any. */
  998         if (tp->t_flags & TF_TOE)
  999                 tcp_offload_detach(tp);
 1000 #endif
 1001                 
 1002         tcp_free_sackholes(tp);
 1003 
 1004         /* Allow the CC algorithm to clean up after itself. */
 1005         if (CC_ALGO(tp)->cb_destroy != NULL)
 1006                 CC_ALGO(tp)->cb_destroy(tp->ccv);
 1007 
 1008         khelp_destroy_osd(tp->osd);
 1009 
 1010         CC_ALGO(tp) = NULL;
 1011         inp->inp_ppcb = NULL;
 1012         if ((tp->t_timers->tt_flags & TT_MASK) == 0) {
 1013                 /* We own the last reference on tcpcb, let's free it. */
 1014                 tp->t_inpcb = NULL;
 1015                 uma_zfree(V_tcpcb_zone, tp);
 1016                 released = in_pcbrele_wlocked(inp);
 1017                 KASSERT(!released, ("%s: inp %p should not have been released "
 1018                         "here", __func__, inp));
 1019         }
 1020 }
 1021 
 1022 void
 1023 tcp_timer_2msl_discard(void *xtp)
 1024 {
 1025 
 1026         tcp_timer_discard((struct tcpcb *)xtp, TT_2MSL);
 1027 }
 1028 
 1029 void
 1030 tcp_timer_keep_discard(void *xtp)
 1031 {
 1032 
 1033         tcp_timer_discard((struct tcpcb *)xtp, TT_KEEP);
 1034 }
 1035 
 1036 void
 1037 tcp_timer_persist_discard(void *xtp)
 1038 {
 1039 
 1040         tcp_timer_discard((struct tcpcb *)xtp, TT_PERSIST);
 1041 }
 1042 
 1043 void
 1044 tcp_timer_rexmt_discard(void *xtp)
 1045 {
 1046 
 1047         tcp_timer_discard((struct tcpcb *)xtp, TT_REXMT);
 1048 }
 1049 
 1050 void
 1051 tcp_timer_delack_discard(void *xtp)
 1052 {
 1053 
 1054         tcp_timer_discard((struct tcpcb *)xtp, TT_DELACK);
 1055 }
 1056 
 1057 void
 1058 tcp_timer_discard(struct tcpcb *tp, uint32_t timer_type)
 1059 {
 1060         struct inpcb *inp;
 1061 
 1062         CURVNET_SET(tp->t_vnet);
 1063         INP_INFO_WLOCK(&V_tcbinfo);
 1064         inp = tp->t_inpcb;
 1065         KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL",
 1066                 __func__, tp));
 1067         INP_WLOCK(inp);
 1068         KASSERT((tp->t_timers->tt_flags & TT_STOPPED) != 0,
 1069                 ("%s: tcpcb has to be stopped here", __func__));
 1070         KASSERT((tp->t_timers->tt_flags & timer_type) != 0,
 1071                 ("%s: discard callout should be running", __func__));
 1072         tp->t_timers->tt_flags &= ~timer_type;
 1073         if ((tp->t_timers->tt_flags & TT_MASK) == 0) {
 1074                 /* We own the last reference on this tcpcb, let's free it. */
 1075                 tp->t_inpcb = NULL;
 1076                 uma_zfree(V_tcpcb_zone, tp);
 1077                 if (in_pcbrele_wlocked(inp)) {
 1078                         INP_INFO_WUNLOCK(&V_tcbinfo);
 1079                         CURVNET_RESTORE();
 1080                         return;
 1081                 }
 1082         }
 1083         INP_WUNLOCK(inp);
 1084         INP_INFO_WUNLOCK(&V_tcbinfo);
 1085         CURVNET_RESTORE();
 1086 }
 1087 
 1088 /*
 1089  * Attempt to close a TCP control block, marking it as dropped, and freeing
 1090  * the socket if we hold the only reference.
 1091  */
 1092 struct tcpcb *
 1093 tcp_close(struct tcpcb *tp)
 1094 {
 1095         struct inpcb *inp = tp->t_inpcb;
 1096         struct socket *so;
 1097 
 1098         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
 1099         INP_WLOCK_ASSERT(inp);
 1100 
 1101 #ifdef TCP_OFFLOAD
 1102         if (tp->t_state == TCPS_LISTEN)
 1103                 tcp_offload_listen_stop(tp);
 1104 #endif
 1105         in_pcbdrop(inp);
 1106         TCPSTAT_INC(tcps_closed);
 1107         KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
 1108         so = inp->inp_socket;
 1109         soisdisconnected(so);
 1110         if (inp->inp_flags & INP_SOCKREF) {
 1111                 KASSERT(so->so_state & SS_PROTOREF,
 1112                     ("tcp_close: !SS_PROTOREF"));
 1113                 inp->inp_flags &= ~INP_SOCKREF;
 1114                 INP_WUNLOCK(inp);
 1115                 ACCEPT_LOCK();
 1116                 SOCK_LOCK(so);
 1117                 so->so_state &= ~SS_PROTOREF;
 1118                 sofree(so);
 1119                 return (NULL);
 1120         }
 1121         return (tp);
 1122 }
 1123 
 1124 void
 1125 tcp_drain(void)
 1126 {
 1127         VNET_ITERATOR_DECL(vnet_iter);
 1128 
 1129         if (!do_tcpdrain)
 1130                 return;
 1131 
 1132         VNET_LIST_RLOCK_NOSLEEP();
 1133         VNET_FOREACH(vnet_iter) {
 1134                 CURVNET_SET(vnet_iter);
 1135                 struct inpcb *inpb;
 1136                 struct tcpcb *tcpb;
 1137 
 1138         /*
 1139          * Walk the tcpbs, if existing, and flush the reassembly queue,
 1140          * if there is one...
 1141          * XXX: The "Net/3" implementation doesn't imply that the TCP
 1142          *      reassembly queue should be flushed, but in a situation
 1143          *      where we're really low on mbufs, this is potentially
 1144          *      useful.
 1145          */
 1146                 INP_INFO_RLOCK(&V_tcbinfo);
 1147                 LIST_FOREACH(inpb, V_tcbinfo.ipi_listhead, inp_list) {
 1148                         if (inpb->inp_flags & INP_TIMEWAIT)
 1149                                 continue;
 1150                         INP_WLOCK(inpb);
 1151                         if ((tcpb = intotcpcb(inpb)) != NULL) {
 1152                                 tcp_reass_flush(tcpb);
 1153                                 tcp_clean_sackreport(tcpb);
 1154                         }
 1155                         INP_WUNLOCK(inpb);
 1156                 }
 1157                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1158                 CURVNET_RESTORE();
 1159         }
 1160         VNET_LIST_RUNLOCK_NOSLEEP();
 1161 }
 1162 
 1163 /*
 1164  * Notify a tcp user of an asynchronous error;
 1165  * store error as soft error, but wake up user
 1166  * (for now, won't do anything until can select for soft error).
 1167  *
 1168  * Do not wake up user since there currently is no mechanism for
 1169  * reporting soft errors (yet - a kqueue filter may be added).
 1170  */
 1171 static struct inpcb *
 1172 tcp_notify(struct inpcb *inp, int error)
 1173 {
 1174         struct tcpcb *tp;
 1175 
 1176         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
 1177         INP_WLOCK_ASSERT(inp);
 1178 
 1179         if ((inp->inp_flags & INP_TIMEWAIT) ||
 1180             (inp->inp_flags & INP_DROPPED))
 1181                 return (inp);
 1182 
 1183         tp = intotcpcb(inp);
 1184         KASSERT(tp != NULL, ("tcp_notify: tp == NULL"));
 1185 
 1186         /*
 1187          * Ignore some errors if we are hooked up.
 1188          * If connection hasn't completed, has retransmitted several times,
 1189          * and receives a second error, give up now.  This is better
 1190          * than waiting a long time to establish a connection that
 1191          * can never complete.
 1192          */
 1193         if (tp->t_state == TCPS_ESTABLISHED &&
 1194             (error == EHOSTUNREACH || error == ENETUNREACH ||
 1195              error == EHOSTDOWN)) {
 1196                 return (inp);
 1197         } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
 1198             tp->t_softerror) {
 1199                 tp = tcp_drop(tp, error);
 1200                 if (tp != NULL)
 1201                         return (inp);
 1202                 else
 1203                         return (NULL);
 1204         } else {
 1205                 tp->t_softerror = error;
 1206                 return (inp);
 1207         }
 1208 #if 0
 1209         wakeup( &so->so_timeo);
 1210         sorwakeup(so);
 1211         sowwakeup(so);
 1212 #endif
 1213 }
 1214 
 1215 static int
 1216 tcp_pcblist(SYSCTL_HANDLER_ARGS)
 1217 {
 1218         int error, i, m, n, pcb_count;
 1219         struct inpcb *inp, **inp_list;
 1220         inp_gen_t gencnt;
 1221         struct xinpgen xig;
 1222 
 1223         /*
 1224          * The process of preparing the TCB list is too time-consuming and
 1225          * resource-intensive to repeat twice on every request.
 1226          */
 1227         if (req->oldptr == NULL) {
 1228                 n = V_tcbinfo.ipi_count + syncache_pcbcount();
 1229                 n += imax(n / 8, 10);
 1230                 req->oldidx = 2 * (sizeof xig) + n * sizeof(struct xtcpcb);
 1231                 return (0);
 1232         }
 1233 
 1234         if (req->newptr != NULL)
 1235                 return (EPERM);
 1236 
 1237         /*
 1238          * OK, now we're committed to doing something.
 1239          */
 1240         INP_INFO_RLOCK(&V_tcbinfo);
 1241         gencnt = V_tcbinfo.ipi_gencnt;
 1242         n = V_tcbinfo.ipi_count;
 1243         INP_INFO_RUNLOCK(&V_tcbinfo);
 1244 
 1245         m = syncache_pcbcount();
 1246 
 1247         error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
 1248                 + (n + m) * sizeof(struct xtcpcb));
 1249         if (error != 0)
 1250                 return (error);
 1251 
 1252         xig.xig_len = sizeof xig;
 1253         xig.xig_count = n + m;
 1254         xig.xig_gen = gencnt;
 1255         xig.xig_sogen = so_gencnt;
 1256         error = SYSCTL_OUT(req, &xig, sizeof xig);
 1257         if (error)
 1258                 return (error);
 1259 
 1260         error = syncache_pcblist(req, m, &pcb_count);
 1261         if (error)
 1262                 return (error);
 1263 
 1264         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
 1265         if (inp_list == NULL)
 1266                 return (ENOMEM);
 1267 
 1268         INP_INFO_RLOCK(&V_tcbinfo);
 1269         for (inp = LIST_FIRST(V_tcbinfo.ipi_listhead), i = 0;
 1270             inp != NULL && i < n; inp = LIST_NEXT(inp, inp_list)) {
 1271                 INP_WLOCK(inp);
 1272                 if (inp->inp_gencnt <= gencnt) {
 1273                         /*
 1274                          * XXX: This use of cr_cansee(), introduced with
 1275                          * TCP state changes, is not quite right, but for
 1276                          * now, better than nothing.
 1277                          */
 1278                         if (inp->inp_flags & INP_TIMEWAIT) {
 1279                                 if (intotw(inp) != NULL)
 1280                                         error = cr_cansee(req->td->td_ucred,
 1281                                             intotw(inp)->tw_cred);
 1282                                 else
 1283                                         error = EINVAL; /* Skip this inp. */
 1284                         } else
 1285                                 error = cr_canseeinpcb(req->td->td_ucred, inp);
 1286                         if (error == 0) {
 1287                                 in_pcbref(inp);
 1288                                 inp_list[i++] = inp;
 1289                         }
 1290                 }
 1291                 INP_WUNLOCK(inp);
 1292         }
 1293         INP_INFO_RUNLOCK(&V_tcbinfo);
 1294         n = i;
 1295 
 1296         error = 0;
 1297         for (i = 0; i < n; i++) {
 1298                 inp = inp_list[i];
 1299                 INP_RLOCK(inp);
 1300                 if (inp->inp_gencnt <= gencnt) {
 1301                         struct xtcpcb xt;
 1302                         void *inp_ppcb;
 1303 
 1304                         bzero(&xt, sizeof(xt));
 1305                         xt.xt_len = sizeof xt;
 1306                         /* XXX should avoid extra copy */
 1307                         bcopy(inp, &xt.xt_inp, sizeof *inp);
 1308                         inp_ppcb = inp->inp_ppcb;
 1309                         if (inp_ppcb == NULL)
 1310                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1311                         else if (inp->inp_flags & INP_TIMEWAIT) {
 1312                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1313                                 xt.xt_tp.t_state = TCPS_TIME_WAIT;
 1314                         } else {
 1315                                 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
 1316                                 if (xt.xt_tp.t_timers)
 1317                                         tcp_timer_to_xtimer(&xt.xt_tp, xt.xt_tp.t_timers, &xt.xt_timer);
 1318                         }
 1319                         if (inp->inp_socket != NULL)
 1320                                 sotoxsocket(inp->inp_socket, &xt.xt_socket);
 1321                         else {
 1322                                 bzero(&xt.xt_socket, sizeof xt.xt_socket);
 1323                                 xt.xt_socket.xso_protocol = IPPROTO_TCP;
 1324                         }
 1325                         xt.xt_inp.inp_gencnt = inp->inp_gencnt;
 1326                         INP_RUNLOCK(inp);
 1327                         error = SYSCTL_OUT(req, &xt, sizeof xt);
 1328                 } else
 1329                         INP_RUNLOCK(inp);
 1330         }
 1331         INP_INFO_WLOCK(&V_tcbinfo);
 1332         for (i = 0; i < n; i++) {
 1333                 inp = inp_list[i];
 1334                 INP_RLOCK(inp);
 1335                 if (!in_pcbrele_rlocked(inp))
 1336                         INP_RUNLOCK(inp);
 1337         }
 1338         INP_INFO_WUNLOCK(&V_tcbinfo);
 1339 
 1340         if (!error) {
 1341                 /*
 1342                  * Give the user an updated idea of our state.
 1343                  * If the generation differs from what we told
 1344                  * her before, she knows that something happened
 1345                  * while we were processing this request, and it
 1346                  * might be necessary to retry.
 1347                  */
 1348                 INP_INFO_RLOCK(&V_tcbinfo);
 1349                 xig.xig_gen = V_tcbinfo.ipi_gencnt;
 1350                 xig.xig_sogen = so_gencnt;
 1351                 xig.xig_count = V_tcbinfo.ipi_count + pcb_count;
 1352                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1353                 error = SYSCTL_OUT(req, &xig, sizeof xig);
 1354         }
 1355         free(inp_list, M_TEMP);
 1356         return (error);
 1357 }
 1358 
 1359 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist,
 1360     CTLTYPE_OPAQUE | CTLFLAG_RD, NULL, 0,
 1361     tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
 1362 
 1363 #ifdef INET
 1364 static int
 1365 tcp_getcred(SYSCTL_HANDLER_ARGS)
 1366 {
 1367         struct xucred xuc;
 1368         struct sockaddr_in addrs[2];
 1369         struct inpcb *inp;
 1370         int error;
 1371 
 1372         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1373         if (error)
 1374                 return (error);
 1375         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1376         if (error)
 1377                 return (error);
 1378         inp = in_pcblookup(&V_tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
 1379             addrs[0].sin_addr, addrs[0].sin_port, INPLOOKUP_RLOCKPCB, NULL);
 1380         if (inp != NULL) {
 1381                 if (inp->inp_socket == NULL)
 1382                         error = ENOENT;
 1383                 if (error == 0)
 1384                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1385                 if (error == 0)
 1386                         cru2x(inp->inp_cred, &xuc);
 1387                 INP_RUNLOCK(inp);
 1388         } else
 1389                 error = ENOENT;
 1390         if (error == 0)
 1391                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1392         return (error);
 1393 }
 1394 
 1395 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
 1396     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1397     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
 1398 #endif /* INET */
 1399 
 1400 #ifdef INET6
 1401 static int
 1402 tcp6_getcred(SYSCTL_HANDLER_ARGS)
 1403 {
 1404         struct xucred xuc;
 1405         struct sockaddr_in6 addrs[2];
 1406         struct inpcb *inp;
 1407         int error;
 1408 #ifdef INET
 1409         int mapped = 0;
 1410 #endif
 1411 
 1412         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1413         if (error)
 1414                 return (error);
 1415         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1416         if (error)
 1417                 return (error);
 1418         if ((error = sa6_embedscope(&addrs[0], V_ip6_use_defzone)) != 0 ||
 1419             (error = sa6_embedscope(&addrs[1], V_ip6_use_defzone)) != 0) {
 1420                 return (error);
 1421         }
 1422         if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
 1423 #ifdef INET
 1424                 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
 1425                         mapped = 1;
 1426                 else
 1427 #endif
 1428                         return (EINVAL);
 1429         }
 1430 
 1431 #ifdef INET
 1432         if (mapped == 1)
 1433                 inp = in_pcblookup(&V_tcbinfo,
 1434                         *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
 1435                         addrs[1].sin6_port,
 1436                         *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
 1437                         addrs[0].sin6_port, INPLOOKUP_RLOCKPCB, NULL);
 1438         else
 1439 #endif
 1440                 inp = in6_pcblookup(&V_tcbinfo,
 1441                         &addrs[1].sin6_addr, addrs[1].sin6_port,
 1442                         &addrs[0].sin6_addr, addrs[0].sin6_port,
 1443                         INPLOOKUP_RLOCKPCB, NULL);
 1444         if (inp != NULL) {
 1445                 if (inp->inp_socket == NULL)
 1446                         error = ENOENT;
 1447                 if (error == 0)
 1448                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1449                 if (error == 0)
 1450                         cru2x(inp->inp_cred, &xuc);
 1451                 INP_RUNLOCK(inp);
 1452         } else
 1453                 error = ENOENT;
 1454         if (error == 0)
 1455                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1456         return (error);
 1457 }
 1458 
 1459 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 1460     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1461     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
 1462 #endif /* INET6 */
 1463 
 1464 
 1465 #ifdef INET
 1466 void
 1467 tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
 1468 {
 1469         struct ip *ip = vip;
 1470         struct tcphdr *th;
 1471         struct in_addr faddr;
 1472         struct inpcb *inp;
 1473         struct tcpcb *tp;
 1474         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1475         struct icmp *icp;
 1476         struct in_conninfo inc;
 1477         tcp_seq icmp_tcp_seq;
 1478         int mtu;
 1479 
 1480         faddr = ((struct sockaddr_in *)sa)->sin_addr;
 1481         if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
 1482                 return;
 1483 
 1484         if (cmd == PRC_MSGSIZE)
 1485                 notify = tcp_mtudisc_notify;
 1486         else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
 1487                 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
 1488                 notify = tcp_drop_syn_sent;
 1489         /*
 1490          * Redirects don't need to be handled up here.
 1491          */
 1492         else if (PRC_IS_REDIRECT(cmd))
 1493                 return;
 1494         /*
 1495          * Source quench is depreciated.
 1496          */
 1497         else if (cmd == PRC_QUENCH)
 1498                 return;
 1499         /*
 1500          * Hostdead is ugly because it goes linearly through all PCBs.
 1501          * XXX: We never get this from ICMP, otherwise it makes an
 1502          * excellent DoS attack on machines with many connections.
 1503          */
 1504         else if (cmd == PRC_HOSTDEAD)
 1505                 ip = NULL;
 1506         else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
 1507                 return;
 1508         if (ip != NULL) {
 1509                 icp = (struct icmp *)((caddr_t)ip
 1510                                       - offsetof(struct icmp, icmp_ip));
 1511                 th = (struct tcphdr *)((caddr_t)ip
 1512                                        + (ip->ip_hl << 2));
 1513                 INP_INFO_WLOCK(&V_tcbinfo);
 1514                 inp = in_pcblookup(&V_tcbinfo, faddr, th->th_dport,
 1515                     ip->ip_src, th->th_sport, INPLOOKUP_WLOCKPCB, NULL);
 1516                 if (inp != NULL)  {
 1517                         if (!(inp->inp_flags & INP_TIMEWAIT) &&
 1518                             !(inp->inp_flags & INP_DROPPED) &&
 1519                             !(inp->inp_socket == NULL)) {
 1520                                 icmp_tcp_seq = htonl(th->th_seq);
 1521                                 tp = intotcpcb(inp);
 1522                                 if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
 1523                                     SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
 1524                                         if (cmd == PRC_MSGSIZE) {
 1525                                             /*
 1526                                              * MTU discovery:
 1527                                              * If we got a needfrag set the MTU
 1528                                              * in the route to the suggested new
 1529                                              * value (if given) and then notify.
 1530                                              */
 1531                                             bzero(&inc, sizeof(inc));
 1532                                             inc.inc_faddr = faddr;
 1533                                             inc.inc_fibnum =
 1534                                                 inp->inp_inc.inc_fibnum;
 1535 
 1536                                             mtu = ntohs(icp->icmp_nextmtu);
 1537                                             /*
 1538                                              * If no alternative MTU was
 1539                                              * proposed, try the next smaller
 1540                                              * one.
 1541                                              */
 1542                                             if (!mtu)
 1543                                                 mtu = ip_next_mtu(
 1544                                                  ntohs(ip->ip_len), 1);
 1545                                             if (mtu < V_tcp_minmss
 1546                                                  + sizeof(struct tcpiphdr))
 1547                                                 mtu = V_tcp_minmss
 1548                                                  + sizeof(struct tcpiphdr);
 1549                                             /*
 1550                                              * Only cache the MTU if it
 1551                                              * is smaller than the interface
 1552                                              * or route MTU.  tcp_mtudisc()
 1553                                              * will do right thing by itself.
 1554                                              */
 1555                                             if (mtu <= tcp_maxmtu(&inc, NULL))
 1556                                                 tcp_hc_updatemtu(&inc, mtu);
 1557                                             tcp_mtudisc(inp, mtu);
 1558                                         } else
 1559                                                 inp = (*notify)(inp,
 1560                                                     inetctlerrmap[cmd]);
 1561                                 }
 1562                         }
 1563                         if (inp != NULL)
 1564                                 INP_WUNLOCK(inp);
 1565                 } else {
 1566                         bzero(&inc, sizeof(inc));
 1567                         inc.inc_fport = th->th_dport;
 1568                         inc.inc_lport = th->th_sport;
 1569                         inc.inc_faddr = faddr;
 1570                         inc.inc_laddr = ip->ip_src;
 1571                         syncache_unreach(&inc, th);
 1572                 }
 1573                 INP_INFO_WUNLOCK(&V_tcbinfo);
 1574         } else
 1575                 in_pcbnotifyall(&V_tcbinfo, faddr, inetctlerrmap[cmd], notify);
 1576 }
 1577 #endif /* INET */
 1578 
 1579 #ifdef INET6
 1580 void
 1581 tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
 1582 {
 1583         struct tcphdr th;
 1584         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1585         struct ip6_hdr *ip6;
 1586         struct mbuf *m;
 1587         struct ip6ctlparam *ip6cp = NULL;
 1588         const struct sockaddr_in6 *sa6_src = NULL;
 1589         int off;
 1590         struct tcp_portonly {
 1591                 u_int16_t th_sport;
 1592                 u_int16_t th_dport;
 1593         } *thp;
 1594 
 1595         if (sa->sa_family != AF_INET6 ||
 1596             sa->sa_len != sizeof(struct sockaddr_in6))
 1597                 return;
 1598 
 1599         if (cmd == PRC_MSGSIZE)
 1600                 notify = tcp_mtudisc_notify;
 1601         else if (!PRC_IS_REDIRECT(cmd) &&
 1602                  ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
 1603                 return;
 1604         /* Source quench is depreciated. */
 1605         else if (cmd == PRC_QUENCH)
 1606                 return;
 1607 
 1608         /* if the parameter is from icmp6, decode it. */
 1609         if (d != NULL) {
 1610                 ip6cp = (struct ip6ctlparam *)d;
 1611                 m = ip6cp->ip6c_m;
 1612                 ip6 = ip6cp->ip6c_ip6;
 1613                 off = ip6cp->ip6c_off;
 1614                 sa6_src = ip6cp->ip6c_src;
 1615         } else {
 1616                 m = NULL;
 1617                 ip6 = NULL;
 1618                 off = 0;        /* fool gcc */
 1619                 sa6_src = &sa6_any;
 1620         }
 1621 
 1622         if (ip6 != NULL) {
 1623                 struct in_conninfo inc;
 1624                 /*
 1625                  * XXX: We assume that when IPV6 is non NULL,
 1626                  * M and OFF are valid.
 1627                  */
 1628 
 1629                 /* check if we can safely examine src and dst ports */
 1630                 if (m->m_pkthdr.len < off + sizeof(*thp))
 1631                         return;
 1632 
 1633                 bzero(&th, sizeof(th));
 1634                 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
 1635 
 1636                 in6_pcbnotify(&V_tcbinfo, sa, th.th_dport,
 1637                     (struct sockaddr *)ip6cp->ip6c_src,
 1638                     th.th_sport, cmd, NULL, notify);
 1639 
 1640                 bzero(&inc, sizeof(inc));
 1641                 inc.inc_fport = th.th_dport;
 1642                 inc.inc_lport = th.th_sport;
 1643                 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
 1644                 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
 1645                 inc.inc_flags |= INC_ISIPV6;
 1646                 INP_INFO_WLOCK(&V_tcbinfo);
 1647                 syncache_unreach(&inc, &th);
 1648                 INP_INFO_WUNLOCK(&V_tcbinfo);
 1649         } else
 1650                 in6_pcbnotify(&V_tcbinfo, sa, 0, (const struct sockaddr *)sa6_src,
 1651                               0, cmd, NULL, notify);
 1652 }
 1653 #endif /* INET6 */
 1654 
 1655 
 1656 /*
 1657  * Following is where TCP initial sequence number generation occurs.
 1658  *
 1659  * There are two places where we must use initial sequence numbers:
 1660  * 1.  In SYN-ACK packets.
 1661  * 2.  In SYN packets.
 1662  *
 1663  * All ISNs for SYN-ACK packets are generated by the syncache.  See
 1664  * tcp_syncache.c for details.
 1665  *
 1666  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 1667  * depends on this property.  In addition, these ISNs should be
 1668  * unguessable so as to prevent connection hijacking.  To satisfy
 1669  * the requirements of this situation, the algorithm outlined in
 1670  * RFC 1948 is used, with only small modifications.
 1671  *
 1672  * Implementation details:
 1673  *
 1674  * Time is based off the system timer, and is corrected so that it
 1675  * increases by one megabyte per second.  This allows for proper
 1676  * recycling on high speed LANs while still leaving over an hour
 1677  * before rollover.
 1678  *
 1679  * As reading the *exact* system time is too expensive to be done
 1680  * whenever setting up a TCP connection, we increment the time
 1681  * offset in two ways.  First, a small random positive increment
 1682  * is added to isn_offset for each connection that is set up.
 1683  * Second, the function tcp_isn_tick fires once per clock tick
 1684  * and increments isn_offset as necessary so that sequence numbers
 1685  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
 1686  * random positive increments serve only to ensure that the same
 1687  * exact sequence number is never sent out twice (as could otherwise
 1688  * happen when a port is recycled in less than the system tick
 1689  * interval.)
 1690  *
 1691  * net.inet.tcp.isn_reseed_interval controls the number of seconds
 1692  * between seeding of isn_secret.  This is normally set to zero,
 1693  * as reseeding should not be necessary.
 1694  *
 1695  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
 1696  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
 1697  * general, this means holding an exclusive (write) lock.
 1698  */
 1699 
 1700 #define ISN_BYTES_PER_SECOND 1048576
 1701 #define ISN_STATIC_INCREMENT 4096
 1702 #define ISN_RANDOM_INCREMENT (4096 - 1)
 1703 
 1704 static VNET_DEFINE(u_char, isn_secret[32]);
 1705 static VNET_DEFINE(int, isn_last);
 1706 static VNET_DEFINE(int, isn_last_reseed);
 1707 static VNET_DEFINE(u_int32_t, isn_offset);
 1708 static VNET_DEFINE(u_int32_t, isn_offset_old);
 1709 
 1710 #define V_isn_secret                    VNET(isn_secret)
 1711 #define V_isn_last                      VNET(isn_last)
 1712 #define V_isn_last_reseed               VNET(isn_last_reseed)
 1713 #define V_isn_offset                    VNET(isn_offset)
 1714 #define V_isn_offset_old                VNET(isn_offset_old)
 1715 
 1716 tcp_seq
 1717 tcp_new_isn(struct tcpcb *tp)
 1718 {
 1719         MD5_CTX isn_ctx;
 1720         u_int32_t md5_buffer[4];
 1721         tcp_seq new_isn;
 1722         u_int32_t projected_offset;
 1723 
 1724         INP_WLOCK_ASSERT(tp->t_inpcb);
 1725 
 1726         ISN_LOCK();
 1727         /* Seed if this is the first use, reseed if requested. */
 1728         if ((V_isn_last_reseed == 0) || ((V_tcp_isn_reseed_interval > 0) &&
 1729              (((u_int)V_isn_last_reseed + (u_int)V_tcp_isn_reseed_interval*hz)
 1730                 < (u_int)ticks))) {
 1731                 read_random(&V_isn_secret, sizeof(V_isn_secret));
 1732                 V_isn_last_reseed = ticks;
 1733         }
 1734 
 1735         /* Compute the md5 hash and return the ISN. */
 1736         MD5Init(&isn_ctx);
 1737         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
 1738         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
 1739 #ifdef INET6
 1740         if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
 1741                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
 1742                           sizeof(struct in6_addr));
 1743                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
 1744                           sizeof(struct in6_addr));
 1745         } else
 1746 #endif
 1747         {
 1748                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
 1749                           sizeof(struct in_addr));
 1750                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
 1751                           sizeof(struct in_addr));
 1752         }
 1753         MD5Update(&isn_ctx, (u_char *) &V_isn_secret, sizeof(V_isn_secret));
 1754         MD5Final((u_char *) &md5_buffer, &isn_ctx);
 1755         new_isn = (tcp_seq) md5_buffer[0];
 1756         V_isn_offset += ISN_STATIC_INCREMENT +
 1757                 (arc4random() & ISN_RANDOM_INCREMENT);
 1758         if (ticks != V_isn_last) {
 1759                 projected_offset = V_isn_offset_old +
 1760                     ISN_BYTES_PER_SECOND / hz * (ticks - V_isn_last);
 1761                 if (SEQ_GT(projected_offset, V_isn_offset))
 1762                         V_isn_offset = projected_offset;
 1763                 V_isn_offset_old = V_isn_offset;
 1764                 V_isn_last = ticks;
 1765         }
 1766         new_isn += V_isn_offset;
 1767         ISN_UNLOCK();
 1768         return (new_isn);
 1769 }
 1770 
 1771 /*
 1772  * When a specific ICMP unreachable message is received and the
 1773  * connection state is SYN-SENT, drop the connection.  This behavior
 1774  * is controlled by the icmp_may_rst sysctl.
 1775  */
 1776 struct inpcb *
 1777 tcp_drop_syn_sent(struct inpcb *inp, int errno)
 1778 {
 1779         struct tcpcb *tp;
 1780 
 1781         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
 1782         INP_WLOCK_ASSERT(inp);
 1783 
 1784         if ((inp->inp_flags & INP_TIMEWAIT) ||
 1785             (inp->inp_flags & INP_DROPPED))
 1786                 return (inp);
 1787 
 1788         tp = intotcpcb(inp);
 1789         if (tp->t_state != TCPS_SYN_SENT)
 1790                 return (inp);
 1791 
 1792         tp = tcp_drop(tp, errno);
 1793         if (tp != NULL)
 1794                 return (inp);
 1795         else
 1796                 return (NULL);
 1797 }
 1798 
 1799 /*
 1800  * When `need fragmentation' ICMP is received, update our idea of the MSS
 1801  * based on the new value. Also nudge TCP to send something, since we
 1802  * know the packet we just sent was dropped.
 1803  * This duplicates some code in the tcp_mss() function in tcp_input.c.
 1804  */
 1805 static struct inpcb *
 1806 tcp_mtudisc_notify(struct inpcb *inp, int error)
 1807 {
 1808 
 1809         return (tcp_mtudisc(inp, -1));
 1810 }
 1811 
 1812 struct inpcb *
 1813 tcp_mtudisc(struct inpcb *inp, int mtuoffer)
 1814 {
 1815         struct tcpcb *tp;
 1816         struct socket *so;
 1817 
 1818         INP_WLOCK_ASSERT(inp);
 1819         if ((inp->inp_flags & INP_TIMEWAIT) ||
 1820             (inp->inp_flags & INP_DROPPED))
 1821                 return (inp);
 1822 
 1823         tp = intotcpcb(inp);
 1824         KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
 1825 
 1826         tcp_mss_update(tp, -1, mtuoffer, NULL, NULL);
 1827   
 1828         so = inp->inp_socket;
 1829         SOCKBUF_LOCK(&so->so_snd);
 1830         /* If the mss is larger than the socket buffer, decrease the mss. */
 1831         if (so->so_snd.sb_hiwat < tp->t_maxseg)
 1832                 tp->t_maxseg = so->so_snd.sb_hiwat;
 1833         SOCKBUF_UNLOCK(&so->so_snd);
 1834 
 1835         TCPSTAT_INC(tcps_mturesent);
 1836         tp->t_rtttime = 0;
 1837         tp->snd_nxt = tp->snd_una;
 1838         tcp_free_sackholes(tp);
 1839         tp->snd_recover = tp->snd_max;
 1840         if (tp->t_flags & TF_SACK_PERMIT)
 1841                 EXIT_FASTRECOVERY(tp->t_flags);
 1842         tcp_output(tp);
 1843         return (inp);
 1844 }
 1845 
 1846 #ifdef INET
 1847 /*
 1848  * Look-up the routing entry to the peer of this inpcb.  If no route
 1849  * is found and it cannot be allocated, then return 0.  This routine
 1850  * is called by TCP routines that access the rmx structure and by
 1851  * tcp_mss_update to get the peer/interface MTU.
 1852  */
 1853 u_long
 1854 tcp_maxmtu(struct in_conninfo *inc, struct tcp_ifcap *cap)
 1855 {
 1856         struct route sro;
 1857         struct sockaddr_in *dst;
 1858         struct ifnet *ifp;
 1859         u_long maxmtu = 0;
 1860 
 1861         KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
 1862 
 1863         bzero(&sro, sizeof(sro));
 1864         if (inc->inc_faddr.s_addr != INADDR_ANY) {
 1865                 dst = (struct sockaddr_in *)&sro.ro_dst;
 1866                 dst->sin_family = AF_INET;
 1867                 dst->sin_len = sizeof(*dst);
 1868                 dst->sin_addr = inc->inc_faddr;
 1869                 in_rtalloc_ign(&sro, 0, inc->inc_fibnum);
 1870         }
 1871         if (sro.ro_rt != NULL) {
 1872                 ifp = sro.ro_rt->rt_ifp;
 1873                 if (sro.ro_rt->rt_mtu == 0)
 1874                         maxmtu = ifp->if_mtu;
 1875                 else
 1876                         maxmtu = min(sro.ro_rt->rt_mtu, ifp->if_mtu);
 1877 
 1878                 /* Report additional interface capabilities. */
 1879                 if (cap != NULL) {
 1880                         if (ifp->if_capenable & IFCAP_TSO4 &&
 1881                             ifp->if_hwassist & CSUM_TSO) {
 1882                                 cap->ifcap |= CSUM_TSO;
 1883                                 cap->tsomax = ifp->if_hw_tsomax;
 1884                                 cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
 1885                                 cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
 1886                         }
 1887                 }
 1888                 RTFREE(sro.ro_rt);
 1889         }
 1890         return (maxmtu);
 1891 }
 1892 #endif /* INET */
 1893 
 1894 #ifdef INET6
 1895 u_long
 1896 tcp_maxmtu6(struct in_conninfo *inc, struct tcp_ifcap *cap)
 1897 {
 1898         struct route_in6 sro6;
 1899         struct ifnet *ifp;
 1900         u_long maxmtu = 0;
 1901 
 1902         KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
 1903 
 1904         bzero(&sro6, sizeof(sro6));
 1905         if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
 1906                 sro6.ro_dst.sin6_family = AF_INET6;
 1907                 sro6.ro_dst.sin6_len = sizeof(struct sockaddr_in6);
 1908                 sro6.ro_dst.sin6_addr = inc->inc6_faddr;
 1909                 in6_rtalloc_ign(&sro6, 0, inc->inc_fibnum);
 1910         }
 1911         if (sro6.ro_rt != NULL) {
 1912                 ifp = sro6.ro_rt->rt_ifp;
 1913                 if (sro6.ro_rt->rt_mtu == 0)
 1914                         maxmtu = IN6_LINKMTU(sro6.ro_rt->rt_ifp);
 1915                 else
 1916                         maxmtu = min(sro6.ro_rt->rt_mtu,
 1917                                      IN6_LINKMTU(sro6.ro_rt->rt_ifp));
 1918 
 1919                 /* Report additional interface capabilities. */
 1920                 if (cap != NULL) {
 1921                         if (ifp->if_capenable & IFCAP_TSO6 &&
 1922                             ifp->if_hwassist & CSUM_TSO) {
 1923                                 cap->ifcap |= CSUM_TSO;
 1924                                 cap->tsomax = ifp->if_hw_tsomax;
 1925                                 cap->tsomaxsegcount = ifp->if_hw_tsomaxsegcount;
 1926                                 cap->tsomaxsegsize = ifp->if_hw_tsomaxsegsize;
 1927                         }
 1928                 }
 1929                 RTFREE(sro6.ro_rt);
 1930         }
 1931 
 1932         return (maxmtu);
 1933 }
 1934 #endif /* INET6 */
 1935 
 1936 #ifdef IPSEC
 1937 /* compute ESP/AH header size for TCP, including outer IP header. */
 1938 size_t
 1939 ipsec_hdrsiz_tcp(struct tcpcb *tp)
 1940 {
 1941         struct inpcb *inp;
 1942         struct mbuf *m;
 1943         size_t hdrsiz;
 1944         struct ip *ip;
 1945 #ifdef INET6
 1946         struct ip6_hdr *ip6;
 1947 #endif
 1948         struct tcphdr *th;
 1949 
 1950         if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
 1951                 return (0);
 1952         m = m_gethdr(M_NOWAIT, MT_DATA);
 1953         if (!m)
 1954                 return (0);
 1955 
 1956 #ifdef INET6
 1957         if ((inp->inp_vflag & INP_IPV6) != 0) {
 1958                 ip6 = mtod(m, struct ip6_hdr *);
 1959                 th = (struct tcphdr *)(ip6 + 1);
 1960                 m->m_pkthdr.len = m->m_len =
 1961                         sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1962                 tcpip_fillheaders(inp, ip6, th);
 1963                 hdrsiz = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1964         } else
 1965 #endif /* INET6 */
 1966         {
 1967                 ip = mtod(m, struct ip *);
 1968                 th = (struct tcphdr *)(ip + 1);
 1969                 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
 1970                 tcpip_fillheaders(inp, ip, th);
 1971                 hdrsiz = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1972         }
 1973 
 1974         m_free(m);
 1975         return (hdrsiz);
 1976 }
 1977 #endif /* IPSEC */
 1978 
 1979 #ifdef TCP_SIGNATURE
 1980 /*
 1981  * Callback function invoked by m_apply() to digest TCP segment data
 1982  * contained within an mbuf chain.
 1983  */
 1984 static int
 1985 tcp_signature_apply(void *fstate, void *data, u_int len)
 1986 {
 1987 
 1988         MD5Update(fstate, (u_char *)data, len);
 1989         return (0);
 1990 }
 1991 
 1992 /*
 1993  * Compute TCP-MD5 hash of a TCP segment. (RFC2385)
 1994  *
 1995  * Parameters:
 1996  * m            pointer to head of mbuf chain
 1997  * _unused      
 1998  * len          length of TCP segment data, excluding options
 1999  * optlen       length of TCP segment options
 2000  * buf          pointer to storage for computed MD5 digest
 2001  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 2002  *
 2003  * We do this over ip, tcphdr, segment data, and the key in the SADB.
 2004  * When called from tcp_input(), we can be sure that th_sum has been
 2005  * zeroed out and verified already.
 2006  *
 2007  * Return 0 if successful, otherwise return -1.
 2008  *
 2009  * XXX The key is retrieved from the system's PF_KEY SADB, by keying a
 2010  * search with the destination IP address, and a 'magic SPI' to be
 2011  * determined by the application. This is hardcoded elsewhere to 1179
 2012  * right now. Another branch of this code exists which uses the SPD to
 2013  * specify per-application flows but it is unstable.
 2014  */
 2015 int
 2016 tcp_signature_compute(struct mbuf *m, int _unused, int len, int optlen,
 2017     u_char *buf, u_int direction)
 2018 {
 2019         union sockaddr_union dst;
 2020 #ifdef INET
 2021         struct ippseudo ippseudo;
 2022 #endif
 2023         MD5_CTX ctx;
 2024         int doff;
 2025         struct ip *ip;
 2026 #ifdef INET
 2027         struct ipovly *ipovly;
 2028 #endif
 2029         struct secasvar *sav;
 2030         struct tcphdr *th;
 2031 #ifdef INET6
 2032         struct ip6_hdr *ip6;
 2033         struct in6_addr in6;
 2034         char ip6buf[INET6_ADDRSTRLEN];
 2035         uint32_t plen;
 2036         uint16_t nhdr;
 2037 #endif
 2038         u_short savecsum;
 2039 
 2040         KASSERT(m != NULL, ("NULL mbuf chain"));
 2041         KASSERT(buf != NULL, ("NULL signature pointer"));
 2042 
 2043         /* Extract the destination from the IP header in the mbuf. */
 2044         bzero(&dst, sizeof(union sockaddr_union));
 2045         ip = mtod(m, struct ip *);
 2046 #ifdef INET6
 2047         ip6 = NULL;     /* Make the compiler happy. */
 2048 #endif
 2049         switch (ip->ip_v) {
 2050 #ifdef INET
 2051         case IPVERSION:
 2052                 dst.sa.sa_len = sizeof(struct sockaddr_in);
 2053                 dst.sa.sa_family = AF_INET;
 2054                 dst.sin.sin_addr = (direction == IPSEC_DIR_INBOUND) ?
 2055                     ip->ip_src : ip->ip_dst;
 2056                 break;
 2057 #endif
 2058 #ifdef INET6
 2059         case (IPV6_VERSION >> 4):
 2060                 ip6 = mtod(m, struct ip6_hdr *);
 2061                 dst.sa.sa_len = sizeof(struct sockaddr_in6);
 2062                 dst.sa.sa_family = AF_INET6;
 2063                 dst.sin6.sin6_addr = (direction == IPSEC_DIR_INBOUND) ?
 2064                     ip6->ip6_src : ip6->ip6_dst;
 2065                 break;
 2066 #endif
 2067         default:
 2068                 return (EINVAL);
 2069                 /* NOTREACHED */
 2070                 break;
 2071         }
 2072 
 2073         /* Look up an SADB entry which matches the address of the peer. */
 2074         sav = KEY_ALLOCSA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI));
 2075         if (sav == NULL) {
 2076                 ipseclog((LOG_ERR, "%s: SADB lookup failed for %s\n", __func__,
 2077                     (ip->ip_v == IPVERSION) ? inet_ntoa(dst.sin.sin_addr) :
 2078 #ifdef INET6
 2079                         (ip->ip_v == (IPV6_VERSION >> 4)) ?
 2080                             ip6_sprintf(ip6buf, &dst.sin6.sin6_addr) :
 2081 #endif
 2082                         "(unsupported)"));
 2083                 return (EINVAL);
 2084         }
 2085 
 2086         MD5Init(&ctx);
 2087         /*
 2088          * Step 1: Update MD5 hash with IP(v6) pseudo-header.
 2089          *
 2090          * XXX The ippseudo header MUST be digested in network byte order,
 2091          * or else we'll fail the regression test. Assume all fields we've
 2092          * been doing arithmetic on have been in host byte order.
 2093          * XXX One cannot depend on ipovly->ih_len here. When called from
 2094          * tcp_output(), the underlying ip_len member has not yet been set.
 2095          */
 2096         switch (ip->ip_v) {
 2097 #ifdef INET
 2098         case IPVERSION:
 2099                 ipovly = (struct ipovly *)ip;
 2100                 ippseudo.ippseudo_src = ipovly->ih_src;
 2101                 ippseudo.ippseudo_dst = ipovly->ih_dst;
 2102                 ippseudo.ippseudo_pad = 0;
 2103                 ippseudo.ippseudo_p = IPPROTO_TCP;
 2104                 ippseudo.ippseudo_len = htons(len + sizeof(struct tcphdr) +
 2105                     optlen);
 2106                 MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo));
 2107 
 2108                 th = (struct tcphdr *)((u_char *)ip + sizeof(struct ip));
 2109                 doff = sizeof(struct ip) + sizeof(struct tcphdr) + optlen;
 2110                 break;
 2111 #endif
 2112 #ifdef INET6
 2113         /*
 2114          * RFC 2385, 2.0  Proposal
 2115          * For IPv6, the pseudo-header is as described in RFC 2460, namely the
 2116          * 128-bit source IPv6 address, 128-bit destination IPv6 address, zero-
 2117          * extended next header value (to form 32 bits), and 32-bit segment
 2118          * length.
 2119          * Note: Upper-Layer Packet Length comes before Next Header.
 2120          */
 2121         case (IPV6_VERSION >> 4):
 2122                 in6 = ip6->ip6_src;
 2123                 in6_clearscope(&in6);
 2124                 MD5Update(&ctx, (char *)&in6, sizeof(struct in6_addr));
 2125                 in6 = ip6->ip6_dst;
 2126                 in6_clearscope(&in6);
 2127                 MD5Update(&ctx, (char *)&in6, sizeof(struct in6_addr));
 2128                 plen = htonl(len + sizeof(struct tcphdr) + optlen);
 2129                 MD5Update(&ctx, (char *)&plen, sizeof(uint32_t));
 2130                 nhdr = 0;
 2131                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2132                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2133                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2134                 nhdr = IPPROTO_TCP;
 2135                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2136 
 2137                 th = (struct tcphdr *)((u_char *)ip6 + sizeof(struct ip6_hdr));
 2138                 doff = sizeof(struct ip6_hdr) + sizeof(struct tcphdr) + optlen;
 2139                 break;
 2140 #endif
 2141         default:
 2142                 return (EINVAL);
 2143                 /* NOTREACHED */
 2144                 break;
 2145         }
 2146 
 2147 
 2148         /*
 2149          * Step 2: Update MD5 hash with TCP header, excluding options.
 2150          * The TCP checksum must be set to zero.
 2151          */
 2152         savecsum = th->th_sum;
 2153         th->th_sum = 0;
 2154         MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
 2155         th->th_sum = savecsum;
 2156 
 2157         /*
 2158          * Step 3: Update MD5 hash with TCP segment data.
 2159          *         Use m_apply() to avoid an early m_pullup().
 2160          */
 2161         if (len > 0)
 2162                 m_apply(m, doff, len, tcp_signature_apply, &ctx);
 2163 
 2164         /*
 2165          * Step 4: Update MD5 hash with shared secret.
 2166          */
 2167         MD5Update(&ctx, sav->key_auth->key_data, _KEYLEN(sav->key_auth));
 2168         MD5Final(buf, &ctx);
 2169 
 2170         key_sa_recordxfer(sav, m);
 2171         KEY_FREESAV(&sav);
 2172         return (0);
 2173 }
 2174 
 2175 /*
 2176  * Verify the TCP-MD5 hash of a TCP segment. (RFC2385)
 2177  *
 2178  * Parameters:
 2179  * m            pointer to head of mbuf chain
 2180  * len          length of TCP segment data, excluding options
 2181  * optlen       length of TCP segment options
 2182  * buf          pointer to storage for computed MD5 digest
 2183  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 2184  *
 2185  * Return 1 if successful, otherwise return 0.
 2186  */
 2187 int
 2188 tcp_signature_verify(struct mbuf *m, int off0, int tlen, int optlen,
 2189     struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
 2190 {
 2191         char tmpdigest[TCP_SIGLEN];
 2192 
 2193         if (tcp_sig_checksigs == 0)
 2194                 return (1);
 2195         if ((tcpbflag & TF_SIGNATURE) == 0) {
 2196                 if ((to->to_flags & TOF_SIGNATURE) != 0) {
 2197 
 2198                         /*
 2199                          * If this socket is not expecting signature but
 2200                          * the segment contains signature just fail.
 2201                          */
 2202                         TCPSTAT_INC(tcps_sig_err_sigopt);
 2203                         TCPSTAT_INC(tcps_sig_rcvbadsig);
 2204                         return (0);
 2205                 }
 2206 
 2207                 /* Signature is not expected, and not present in segment. */
 2208                 return (1);
 2209         }
 2210 
 2211         /*
 2212          * If this socket is expecting signature but the segment does not
 2213          * contain any just fail.
 2214          */
 2215         if ((to->to_flags & TOF_SIGNATURE) == 0) {
 2216                 TCPSTAT_INC(tcps_sig_err_nosigopt);
 2217                 TCPSTAT_INC(tcps_sig_rcvbadsig);
 2218                 return (0);
 2219         }
 2220         if (tcp_signature_compute(m, off0, tlen, optlen, &tmpdigest[0],
 2221             IPSEC_DIR_INBOUND) == -1) {
 2222                 TCPSTAT_INC(tcps_sig_err_buildsig);
 2223                 TCPSTAT_INC(tcps_sig_rcvbadsig);
 2224                 return (0);
 2225         }
 2226         
 2227         if (bcmp(to->to_signature, &tmpdigest[0], TCP_SIGLEN) != 0) {
 2228                 TCPSTAT_INC(tcps_sig_rcvbadsig);
 2229                 return (0);
 2230         }
 2231         TCPSTAT_INC(tcps_sig_rcvgoodsig);
 2232         return (1);
 2233 }
 2234 #endif /* TCP_SIGNATURE */
 2235 
 2236 static int
 2237 sysctl_drop(SYSCTL_HANDLER_ARGS)
 2238 {
 2239         /* addrs[0] is a foreign socket, addrs[1] is a local one. */
 2240         struct sockaddr_storage addrs[2];
 2241         struct inpcb *inp;
 2242         struct tcpcb *tp;
 2243         struct tcptw *tw;
 2244         struct sockaddr_in *fin, *lin;
 2245 #ifdef INET6
 2246         struct sockaddr_in6 *fin6, *lin6;
 2247 #endif
 2248         int error;
 2249 
 2250         inp = NULL;
 2251         fin = lin = NULL;
 2252 #ifdef INET6
 2253         fin6 = lin6 = NULL;
 2254 #endif
 2255         error = 0;
 2256 
 2257         if (req->oldptr != NULL || req->oldlen != 0)
 2258                 return (EINVAL);
 2259         if (req->newptr == NULL)
 2260                 return (EPERM);
 2261         if (req->newlen < sizeof(addrs))
 2262                 return (ENOMEM);
 2263         error = SYSCTL_IN(req, &addrs, sizeof(addrs));
 2264         if (error)
 2265                 return (error);
 2266 
 2267         switch (addrs[0].ss_family) {
 2268 #ifdef INET6
 2269         case AF_INET6:
 2270                 fin6 = (struct sockaddr_in6 *)&addrs[0];
 2271                 lin6 = (struct sockaddr_in6 *)&addrs[1];
 2272                 if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
 2273                     lin6->sin6_len != sizeof(struct sockaddr_in6))
 2274                         return (EINVAL);
 2275                 if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
 2276                         if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
 2277                                 return (EINVAL);
 2278                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
 2279                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
 2280                         fin = (struct sockaddr_in *)&addrs[0];
 2281                         lin = (struct sockaddr_in *)&addrs[1];
 2282                         break;
 2283                 }
 2284                 error = sa6_embedscope(fin6, V_ip6_use_defzone);
 2285                 if (error)
 2286                         return (error);
 2287                 error = sa6_embedscope(lin6, V_ip6_use_defzone);
 2288                 if (error)
 2289                         return (error);
 2290                 break;
 2291 #endif
 2292 #ifdef INET
 2293         case AF_INET:
 2294                 fin = (struct sockaddr_in *)&addrs[0];
 2295                 lin = (struct sockaddr_in *)&addrs[1];
 2296                 if (fin->sin_len != sizeof(struct sockaddr_in) ||
 2297                     lin->sin_len != sizeof(struct sockaddr_in))
 2298                         return (EINVAL);
 2299                 break;
 2300 #endif
 2301         default:
 2302                 return (EINVAL);
 2303         }
 2304         INP_INFO_WLOCK(&V_tcbinfo);
 2305         switch (addrs[0].ss_family) {
 2306 #ifdef INET6
 2307         case AF_INET6:
 2308                 inp = in6_pcblookup(&V_tcbinfo, &fin6->sin6_addr,
 2309                     fin6->sin6_port, &lin6->sin6_addr, lin6->sin6_port,
 2310                     INPLOOKUP_WLOCKPCB, NULL);
 2311                 break;
 2312 #endif
 2313 #ifdef INET
 2314         case AF_INET:
 2315                 inp = in_pcblookup(&V_tcbinfo, fin->sin_addr, fin->sin_port,
 2316                     lin->sin_addr, lin->sin_port, INPLOOKUP_WLOCKPCB, NULL);
 2317                 break;
 2318 #endif
 2319         }
 2320         if (inp != NULL) {
 2321                 if (inp->inp_flags & INP_TIMEWAIT) {
 2322                         /*
 2323                          * XXXRW: There currently exists a state where an
 2324                          * inpcb is present, but its timewait state has been
 2325                          * discarded.  For now, don't allow dropping of this
 2326                          * type of inpcb.
 2327                          */
 2328                         tw = intotw(inp);
 2329                         if (tw != NULL)
 2330                                 tcp_twclose(tw, 0);
 2331                         else
 2332                                 INP_WUNLOCK(inp);
 2333                 } else if (!(inp->inp_flags & INP_DROPPED) &&
 2334                            !(inp->inp_socket->so_options & SO_ACCEPTCONN)) {
 2335                         tp = intotcpcb(inp);
 2336                         tp = tcp_drop(tp, ECONNABORTED);
 2337                         if (tp != NULL)
 2338                                 INP_WUNLOCK(inp);
 2339                 } else
 2340                         INP_WUNLOCK(inp);
 2341         } else
 2342                 error = ESRCH;
 2343         INP_INFO_WUNLOCK(&V_tcbinfo);
 2344         return (error);
 2345 }
 2346 
 2347 SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
 2348     CTLTYPE_STRUCT|CTLFLAG_WR|CTLFLAG_SKIP, NULL,
 2349     0, sysctl_drop, "", "Drop TCP connection");
 2350 
 2351 /*
 2352  * Generate a standardized TCP log line for use throughout the
 2353  * tcp subsystem.  Memory allocation is done with M_NOWAIT to
 2354  * allow use in the interrupt context.
 2355  *
 2356  * NB: The caller MUST free(s, M_TCPLOG) the returned string.
 2357  * NB: The function may return NULL if memory allocation failed.
 2358  *
 2359  * Due to header inclusion and ordering limitations the struct ip
 2360  * and ip6_hdr pointers have to be passed as void pointers.
 2361  */
 2362 char *
 2363 tcp_log_vain(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 2364     const void *ip6hdr)
 2365 {
 2366 
 2367         /* Is logging enabled? */
 2368         if (tcp_log_in_vain == 0)
 2369                 return (NULL);
 2370 
 2371         return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
 2372 }
 2373 
 2374 char *
 2375 tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 2376     const void *ip6hdr)
 2377 {
 2378 
 2379         /* Is logging enabled? */
 2380         if (tcp_log_debug == 0)
 2381                 return (NULL);
 2382 
 2383         return (tcp_log_addr(inc, th, ip4hdr, ip6hdr));
 2384 }
 2385 
 2386 static char *
 2387 tcp_log_addr(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 2388     const void *ip6hdr)
 2389 {
 2390         char *s, *sp;
 2391         size_t size;
 2392         struct ip *ip;
 2393 #ifdef INET6
 2394         const struct ip6_hdr *ip6;
 2395 
 2396         ip6 = (const struct ip6_hdr *)ip6hdr;
 2397 #endif /* INET6 */
 2398         ip = (struct ip *)ip4hdr;
 2399 
 2400         /*
 2401          * The log line looks like this:
 2402          * "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags 0x2<SYN>"
 2403          */
 2404         size = sizeof("TCP: []:12345 to []:12345 tcpflags 0x2<>") +
 2405             sizeof(PRINT_TH_FLAGS) + 1 +
 2406 #ifdef INET6
 2407             2 * INET6_ADDRSTRLEN;
 2408 #else
 2409             2 * INET_ADDRSTRLEN;
 2410 #endif /* INET6 */
 2411 
 2412         s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
 2413         if (s == NULL)
 2414                 return (NULL);
 2415 
 2416         strcat(s, "TCP: [");
 2417         sp = s + strlen(s);
 2418 
 2419         if (inc && ((inc->inc_flags & INC_ISIPV6) == 0)) {
 2420                 inet_ntoa_r(inc->inc_faddr, sp);
 2421                 sp = s + strlen(s);
 2422                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2423                 sp = s + strlen(s);
 2424                 inet_ntoa_r(inc->inc_laddr, sp);
 2425                 sp = s + strlen(s);
 2426                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2427 #ifdef INET6
 2428         } else if (inc) {
 2429                 ip6_sprintf(sp, &inc->inc6_faddr);
 2430                 sp = s + strlen(s);
 2431                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2432                 sp = s + strlen(s);
 2433                 ip6_sprintf(sp, &inc->inc6_laddr);
 2434                 sp = s + strlen(s);
 2435                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2436         } else if (ip6 && th) {
 2437                 ip6_sprintf(sp, &ip6->ip6_src);
 2438                 sp = s + strlen(s);
 2439                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2440                 sp = s + strlen(s);
 2441                 ip6_sprintf(sp, &ip6->ip6_dst);
 2442                 sp = s + strlen(s);
 2443                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2444 #endif /* INET6 */
 2445 #ifdef INET
 2446         } else if (ip && th) {
 2447                 inet_ntoa_r(ip->ip_src, sp);
 2448                 sp = s + strlen(s);
 2449                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2450                 sp = s + strlen(s);
 2451                 inet_ntoa_r(ip->ip_dst, sp);
 2452                 sp = s + strlen(s);
 2453                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2454 #endif /* INET */
 2455         } else {
 2456                 free(s, M_TCPLOG);
 2457                 return (NULL);
 2458         }
 2459         sp = s + strlen(s);
 2460         if (th)
 2461                 sprintf(sp, " tcpflags 0x%b", th->th_flags, PRINT_TH_FLAGS);
 2462         if (*(s + size - 1) != '\0')
 2463                 panic("%s: string too long", __func__);
 2464         return (s);
 2465 }
 2466 
 2467 /*
 2468  * A subroutine which makes it easy to track TCP state changes with DTrace.
 2469  * This function shouldn't be called for t_state initializations that don't
 2470  * correspond to actual TCP state transitions.
 2471  */
 2472 void
 2473 tcp_state_change(struct tcpcb *tp, int newstate)
 2474 {
 2475 #if defined(KDTRACE_HOOKS)
 2476         int pstate = tp->t_state;
 2477 #endif
 2478 
 2479         tp->t_state = newstate;
 2480         TCP_PROBE6(state__change, NULL, tp, NULL, tp, NULL, pstate);
 2481 }

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