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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/8.1/sys/netinet/tcp_subr.c 207695 2010-05-06 06:44:19Z bz $");
   34 
   35 #include "opt_compat.h"
   36 #include "opt_inet.h"
   37 #include "opt_inet6.h"
   38 #include "opt_ipsec.h"
   39 #include "opt_tcpdebug.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/callout.h>
   44 #include <sys/kernel.h>
   45 #include <sys/sysctl.h>
   46 #include <sys/jail.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mbuf.h>
   49 #ifdef INET6
   50 #include <sys/domain.h>
   51 #endif
   52 #include <sys/priv.h>
   53 #include <sys/proc.h>
   54 #include <sys/socket.h>
   55 #include <sys/socketvar.h>
   56 #include <sys/protosw.h>
   57 #include <sys/random.h>
   58 
   59 #include <vm/uma.h>
   60 
   61 #include <net/route.h>
   62 #include <net/if.h>
   63 #include <net/vnet.h>
   64 
   65 #include <netinet/in.h>
   66 #include <netinet/in_systm.h>
   67 #include <netinet/ip.h>
   68 #ifdef INET6
   69 #include <netinet/ip6.h>
   70 #endif
   71 #include <netinet/in_pcb.h>
   72 #ifdef INET6
   73 #include <netinet6/in6_pcb.h>
   74 #endif
   75 #include <netinet/in_var.h>
   76 #include <netinet/ip_var.h>
   77 #ifdef INET6
   78 #include <netinet6/ip6_var.h>
   79 #include <netinet6/scope6_var.h>
   80 #include <netinet6/nd6.h>
   81 #endif
   82 #include <netinet/ip_icmp.h>
   83 #include <netinet/tcp.h>
   84 #include <netinet/tcp_fsm.h>
   85 #include <netinet/tcp_seq.h>
   86 #include <netinet/tcp_timer.h>
   87 #include <netinet/tcp_var.h>
   88 #include <netinet/tcp_syncache.h>
   89 #include <netinet/tcp_offload.h>
   90 #ifdef INET6
   91 #include <netinet6/tcp6_var.h>
   92 #endif
   93 #include <netinet/tcpip.h>
   94 #ifdef TCPDEBUG
   95 #include <netinet/tcp_debug.h>
   96 #endif
   97 #include <netinet6/ip6protosw.h>
   98 
   99 #ifdef IPSEC
  100 #include <netipsec/ipsec.h>
  101 #include <netipsec/xform.h>
  102 #ifdef INET6
  103 #include <netipsec/ipsec6.h>
  104 #endif
  105 #include <netipsec/key.h>
  106 #include <sys/syslog.h>
  107 #endif /*IPSEC*/
  108 
  109 #include <machine/in_cksum.h>
  110 #include <sys/md5.h>
  111 
  112 #include <security/mac/mac_framework.h>
  113 
  114 VNET_DEFINE(int, tcp_mssdflt) = TCP_MSS;
  115 #ifdef INET6
  116 VNET_DEFINE(int, tcp_v6mssdflt) = TCP6_MSS;
  117 #endif
  118 
  119 static int
  120 sysctl_net_inet_tcp_mss_check(SYSCTL_HANDLER_ARGS)
  121 {
  122         int error, new;
  123 
  124         new = V_tcp_mssdflt;
  125         error = sysctl_handle_int(oidp, &new, 0, req);
  126         if (error == 0 && req->newptr) {
  127                 if (new < TCP_MINMSS)
  128                         error = EINVAL;
  129                 else
  130                         V_tcp_mssdflt = new;
  131         }
  132         return (error);
  133 }
  134 
  135 SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt,
  136     CTLTYPE_INT|CTLFLAG_RW, &VNET_NAME(tcp_mssdflt), 0,
  137     &sysctl_net_inet_tcp_mss_check, "I",
  138     "Default TCP Maximum Segment Size");
  139 
  140 #ifdef INET6
  141 static int
  142 sysctl_net_inet_tcp_mss_v6_check(SYSCTL_HANDLER_ARGS)
  143 {
  144         int error, new;
  145 
  146         new = V_tcp_v6mssdflt;
  147         error = sysctl_handle_int(oidp, &new, 0, req);
  148         if (error == 0 && req->newptr) {
  149                 if (new < TCP_MINMSS)
  150                         error = EINVAL;
  151                 else
  152                         V_tcp_v6mssdflt = new;
  153         }
  154         return (error);
  155 }
  156 
  157 SYSCTL_VNET_PROC(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
  158     CTLTYPE_INT|CTLFLAG_RW, &VNET_NAME(tcp_v6mssdflt), 0,
  159     &sysctl_net_inet_tcp_mss_v6_check, "I",
  160    "Default TCP Maximum Segment Size for IPv6");
  161 #endif
  162 
  163 static int
  164 vnet_sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
  165 {
  166 
  167         VNET_SYSCTL_ARG(req, arg1);
  168         return (sysctl_msec_to_ticks(oidp, arg1, arg2, req));
  169 }
  170 
  171 /*
  172  * Minimum MSS we accept and use. This prevents DoS attacks where
  173  * we are forced to a ridiculous low MSS like 20 and send hundreds
  174  * of packets instead of one. The effect scales with the available
  175  * bandwidth and quickly saturates the CPU and network interface
  176  * with packet generation and sending. Set to zero to disable MINMSS
  177  * checking. This setting prevents us from sending too small packets.
  178  */
  179 VNET_DEFINE(int, tcp_minmss) = TCP_MINMSS;
  180 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_RW,
  181      &VNET_NAME(tcp_minmss), 0,
  182     "Minmum TCP Maximum Segment Size");
  183 
  184 VNET_DEFINE(int, tcp_do_rfc1323) = 1;
  185 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
  186     &VNET_NAME(tcp_do_rfc1323), 0,
  187     "Enable rfc1323 (high performance TCP) extensions");
  188 
  189 static int      tcp_log_debug = 0;
  190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
  191     &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
  192 
  193 static int      tcp_tcbhashsize = 0;
  194 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
  195     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
  196 
  197 static int      do_tcpdrain = 1;
  198 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
  199     "Enable tcp_drain routine for extra help when low on mbufs");
  200 
  201 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
  202     &VNET_NAME(tcbinfo.ipi_count), 0, "Number of active PCBs");
  203 
  204 static VNET_DEFINE(int, icmp_may_rst) = 1;
  205 #define V_icmp_may_rst                  VNET(icmp_may_rst)
  206 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW,
  207     &VNET_NAME(icmp_may_rst), 0,
  208     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
  209 
  210 static VNET_DEFINE(int, tcp_isn_reseed_interval) = 0;
  211 #define V_tcp_isn_reseed_interval       VNET(tcp_isn_reseed_interval)
  212 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW,
  213     &VNET_NAME(tcp_isn_reseed_interval), 0,
  214     "Seconds between reseeding of ISN secret");
  215 
  216 /*
  217  * TCP bandwidth limiting sysctls.  Note that the default lower bound of
  218  * 1024 exists only for debugging.  A good production default would be
  219  * something like 6100.
  220  */
  221 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, inflight, CTLFLAG_RW, 0,
  222     "TCP inflight data limiting");
  223 
  224 static VNET_DEFINE(int, tcp_inflight_enable) = 1;
  225 #define V_tcp_inflight_enable           VNET(tcp_inflight_enable)
  226 SYSCTL_VNET_INT(_net_inet_tcp_inflight, OID_AUTO, enable, CTLFLAG_RW,
  227     &VNET_NAME(tcp_inflight_enable), 0,
  228     "Enable automatic TCP inflight data limiting");
  229 
  230 static int      tcp_inflight_debug = 0;
  231 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, debug, CTLFLAG_RW,
  232     &tcp_inflight_debug, 0,
  233     "Debug TCP inflight calculations");
  234 
  235 static VNET_DEFINE(int, tcp_inflight_rttthresh);
  236 #define V_tcp_inflight_rttthresh        VNET(tcp_inflight_rttthresh)
  237 SYSCTL_VNET_PROC(_net_inet_tcp_inflight, OID_AUTO, rttthresh,
  238     CTLTYPE_INT|CTLFLAG_RW, &VNET_NAME(tcp_inflight_rttthresh), 0,
  239     vnet_sysctl_msec_to_ticks, "I",
  240     "RTT threshold below which inflight will deactivate itself");
  241 
  242 static VNET_DEFINE(int, tcp_inflight_min) = 6144;
  243 #define V_tcp_inflight_min              VNET(tcp_inflight_min)
  244 SYSCTL_VNET_INT(_net_inet_tcp_inflight, OID_AUTO, min, CTLFLAG_RW,
  245     &VNET_NAME(tcp_inflight_min), 0,
  246     "Lower-bound for TCP inflight window");
  247 
  248 static VNET_DEFINE(int, tcp_inflight_max) = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  249 #define V_tcp_inflight_max              VNET(tcp_inflight_max)
  250 SYSCTL_VNET_INT(_net_inet_tcp_inflight, OID_AUTO, max, CTLFLAG_RW,
  251     &VNET_NAME(tcp_inflight_max), 0,
  252     "Upper-bound for TCP inflight window");
  253 
  254 static VNET_DEFINE(int, tcp_inflight_stab) = 20;
  255 #define V_tcp_inflight_stab             VNET(tcp_inflight_stab)
  256 SYSCTL_VNET_INT(_net_inet_tcp_inflight, OID_AUTO, stab, CTLFLAG_RW,
  257     &VNET_NAME(tcp_inflight_stab), 0,
  258     "Inflight Algorithm Stabilization 20 = 2 packets");
  259 
  260 VNET_DEFINE(uma_zone_t, sack_hole_zone);
  261 #define V_sack_hole_zone                VNET(sack_hole_zone)
  262 
  263 static struct inpcb *tcp_notify(struct inpcb *, int);
  264 static void     tcp_isn_tick(void *);
  265 
  266 /*
  267  * Target size of TCP PCB hash tables. Must be a power of two.
  268  *
  269  * Note that this can be overridden by the kernel environment
  270  * variable net.inet.tcp.tcbhashsize
  271  */
  272 #ifndef TCBHASHSIZE
  273 #define TCBHASHSIZE     512
  274 #endif
  275 
  276 /*
  277  * XXX
  278  * Callouts should be moved into struct tcp directly.  They are currently
  279  * separate because the tcpcb structure is exported to userland for sysctl
  280  * parsing purposes, which do not know about callouts.
  281  */
  282 struct tcpcb_mem {
  283         struct  tcpcb           tcb;
  284         struct  tcp_timer       tt;
  285 };
  286 
  287 static VNET_DEFINE(uma_zone_t, tcpcb_zone);
  288 #define V_tcpcb_zone                    VNET(tcpcb_zone)
  289 
  290 MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
  291 struct callout isn_callout;
  292 static struct mtx isn_mtx;
  293 
  294 #define ISN_LOCK_INIT() mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
  295 #define ISN_LOCK()      mtx_lock(&isn_mtx)
  296 #define ISN_UNLOCK()    mtx_unlock(&isn_mtx)
  297 
  298 /*
  299  * TCP initialization.
  300  */
  301 static void
  302 tcp_zone_change(void *tag)
  303 {
  304 
  305         uma_zone_set_max(V_tcbinfo.ipi_zone, maxsockets);
  306         uma_zone_set_max(V_tcpcb_zone, maxsockets);
  307         tcp_tw_zone_change();
  308 }
  309 
  310 static int
  311 tcp_inpcb_init(void *mem, int size, int flags)
  312 {
  313         struct inpcb *inp = mem;
  314 
  315         INP_LOCK_INIT(inp, "inp", "tcpinp");
  316         return (0);
  317 }
  318 
  319 void
  320 tcp_init(void)
  321 {
  322         int hashsize;
  323 
  324         INP_INFO_LOCK_INIT(&V_tcbinfo, "tcp");
  325         LIST_INIT(&V_tcb);
  326 #ifdef VIMAGE
  327         V_tcbinfo.ipi_vnet = curvnet;
  328 #endif
  329         V_tcbinfo.ipi_listhead = &V_tcb;
  330         hashsize = TCBHASHSIZE;
  331         TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize);
  332         if (!powerof2(hashsize)) {
  333                 printf("WARNING: TCB hash size not a power of 2\n");
  334                 hashsize = 512; /* safe default */
  335         }
  336         V_tcbinfo.ipi_hashbase = hashinit(hashsize, M_PCB,
  337             &V_tcbinfo.ipi_hashmask);
  338         V_tcbinfo.ipi_porthashbase = hashinit(hashsize, M_PCB,
  339             &V_tcbinfo.ipi_porthashmask);
  340         V_tcbinfo.ipi_zone = uma_zcreate("tcp_inpcb", sizeof(struct inpcb),
  341             NULL, NULL, tcp_inpcb_init, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  342         uma_zone_set_max(V_tcbinfo.ipi_zone, maxsockets);
  343         V_tcp_inflight_rttthresh = TCPTV_INFLIGHT_RTTTHRESH;
  344 
  345         /*
  346          * These have to be type stable for the benefit of the timers.
  347          */
  348         V_tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
  349             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  350         uma_zone_set_max(V_tcpcb_zone, maxsockets);
  351 
  352         tcp_tw_init();
  353         syncache_init();
  354         tcp_hc_init();
  355         tcp_reass_init();
  356 
  357         TUNABLE_INT_FETCH("net.inet.tcp.sack.enable", &V_tcp_do_sack);
  358         V_sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
  359             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  360 
  361         /* Skip initialization of globals for non-default instances. */
  362         if (!IS_DEFAULT_VNET(curvnet))
  363                 return;
  364 
  365         /* XXX virtualize those bellow? */
  366         tcp_delacktime = TCPTV_DELACK;
  367         tcp_keepinit = TCPTV_KEEP_INIT;
  368         tcp_keepidle = TCPTV_KEEP_IDLE;
  369         tcp_keepintvl = TCPTV_KEEPINTVL;
  370         tcp_maxpersistidle = TCPTV_KEEP_IDLE;
  371         tcp_msl = TCPTV_MSL;
  372         tcp_rexmit_min = TCPTV_MIN;
  373         if (tcp_rexmit_min < 1)
  374                 tcp_rexmit_min = 1;
  375         tcp_rexmit_slop = TCPTV_CPU_VAR;
  376         tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
  377         tcp_tcbhashsize = hashsize;
  378 
  379 #ifdef INET6
  380 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
  381 #else /* INET6 */
  382 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
  383 #endif /* INET6 */
  384         if (max_protohdr < TCP_MINPROTOHDR)
  385                 max_protohdr = TCP_MINPROTOHDR;
  386         if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
  387                 panic("tcp_init");
  388 #undef TCP_MINPROTOHDR
  389 
  390         ISN_LOCK_INIT();
  391         callout_init(&isn_callout, CALLOUT_MPSAFE);
  392         callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
  393         EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
  394                 SHUTDOWN_PRI_DEFAULT);
  395         EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
  396                 EVENTHANDLER_PRI_ANY);
  397 }
  398 
  399 #ifdef VIMAGE
  400 void
  401 tcp_destroy(void)
  402 {
  403 
  404         tcp_reass_destroy();
  405         tcp_hc_destroy();
  406         syncache_destroy();
  407         tcp_tw_destroy();
  408 
  409         /* XXX check that hashes are empty! */
  410         hashdestroy(V_tcbinfo.ipi_hashbase, M_PCB,
  411             V_tcbinfo.ipi_hashmask);
  412         hashdestroy(V_tcbinfo.ipi_porthashbase, M_PCB,
  413             V_tcbinfo.ipi_porthashmask);
  414 
  415         uma_zdestroy(V_sack_hole_zone);
  416         uma_zdestroy(V_tcpcb_zone);
  417         uma_zdestroy(V_tcbinfo.ipi_zone);
  418 
  419         INP_INFO_LOCK_DESTROY(&V_tcbinfo);
  420 }
  421 #endif
  422 
  423 void
  424 tcp_fini(void *xtp)
  425 {
  426 
  427         callout_stop(&isn_callout);
  428 }
  429 
  430 /*
  431  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
  432  * tcp_template used to store this data in mbufs, but we now recopy it out
  433  * of the tcpcb each time to conserve mbufs.
  434  */
  435 void
  436 tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
  437 {
  438         struct tcphdr *th = (struct tcphdr *)tcp_ptr;
  439 
  440         INP_WLOCK_ASSERT(inp);
  441 
  442 #ifdef INET6
  443         if ((inp->inp_vflag & INP_IPV6) != 0) {
  444                 struct ip6_hdr *ip6;
  445 
  446                 ip6 = (struct ip6_hdr *)ip_ptr;
  447                 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
  448                         (inp->inp_flow & IPV6_FLOWINFO_MASK);
  449                 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
  450                         (IPV6_VERSION & IPV6_VERSION_MASK);
  451                 ip6->ip6_nxt = IPPROTO_TCP;
  452                 ip6->ip6_plen = htons(sizeof(struct tcphdr));
  453                 ip6->ip6_src = inp->in6p_laddr;
  454                 ip6->ip6_dst = inp->in6p_faddr;
  455         } else
  456 #endif
  457         {
  458                 struct ip *ip;
  459 
  460                 ip = (struct ip *)ip_ptr;
  461                 ip->ip_v = IPVERSION;
  462                 ip->ip_hl = 5;
  463                 ip->ip_tos = inp->inp_ip_tos;
  464                 ip->ip_len = 0;
  465                 ip->ip_id = 0;
  466                 ip->ip_off = 0;
  467                 ip->ip_ttl = inp->inp_ip_ttl;
  468                 ip->ip_sum = 0;
  469                 ip->ip_p = IPPROTO_TCP;
  470                 ip->ip_src = inp->inp_laddr;
  471                 ip->ip_dst = inp->inp_faddr;
  472         }
  473         th->th_sport = inp->inp_lport;
  474         th->th_dport = inp->inp_fport;
  475         th->th_seq = 0;
  476         th->th_ack = 0;
  477         th->th_x2 = 0;
  478         th->th_off = 5;
  479         th->th_flags = 0;
  480         th->th_win = 0;
  481         th->th_urp = 0;
  482         th->th_sum = 0;         /* in_pseudo() is called later for ipv4 */
  483 }
  484 
  485 /*
  486  * Create template to be used to send tcp packets on a connection.
  487  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
  488  * use for this function is in keepalives, which use tcp_respond.
  489  */
  490 struct tcptemp *
  491 tcpip_maketemplate(struct inpcb *inp)
  492 {
  493         struct tcptemp *t;
  494 
  495         t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
  496         if (t == NULL)
  497                 return (NULL);
  498         tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
  499         return (t);
  500 }
  501 
  502 /*
  503  * Send a single message to the TCP at address specified by
  504  * the given TCP/IP header.  If m == NULL, then we make a copy
  505  * of the tcpiphdr at ti and send directly to the addressed host.
  506  * This is used to force keep alive messages out using the TCP
  507  * template for a connection.  If flags are given then we send
  508  * a message back to the TCP which originated the * segment ti,
  509  * and discard the mbuf containing it and any other attached mbufs.
  510  *
  511  * In any case the ack and sequence number of the transmitted
  512  * segment are as specified by the parameters.
  513  *
  514  * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
  515  */
  516 void
  517 tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
  518     tcp_seq ack, tcp_seq seq, int flags)
  519 {
  520         int tlen;
  521         int win = 0;
  522         struct ip *ip;
  523         struct tcphdr *nth;
  524 #ifdef INET6
  525         struct ip6_hdr *ip6;
  526         int isipv6;
  527 #endif /* INET6 */
  528         int ipflags = 0;
  529         struct inpcb *inp;
  530 
  531         KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
  532 
  533 #ifdef INET6
  534         isipv6 = ((struct ip *)ipgen)->ip_v == 6;
  535         ip6 = ipgen;
  536 #endif /* INET6 */
  537         ip = ipgen;
  538 
  539         if (tp != NULL) {
  540                 inp = tp->t_inpcb;
  541                 KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
  542                 INP_WLOCK_ASSERT(inp);
  543         } else
  544                 inp = NULL;
  545 
  546         if (tp != NULL) {
  547                 if (!(flags & TH_RST)) {
  548                         win = sbspace(&inp->inp_socket->so_rcv);
  549                         if (win > (long)TCP_MAXWIN << tp->rcv_scale)
  550                                 win = (long)TCP_MAXWIN << tp->rcv_scale;
  551                 }
  552         }
  553         if (m == NULL) {
  554                 m = m_gethdr(M_DONTWAIT, MT_DATA);
  555                 if (m == NULL)
  556                         return;
  557                 tlen = 0;
  558                 m->m_data += max_linkhdr;
  559 #ifdef INET6
  560                 if (isipv6) {
  561                         bcopy((caddr_t)ip6, mtod(m, caddr_t),
  562                               sizeof(struct ip6_hdr));
  563                         ip6 = mtod(m, struct ip6_hdr *);
  564                         nth = (struct tcphdr *)(ip6 + 1);
  565                 } else
  566 #endif /* INET6 */
  567               {
  568                 bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
  569                 ip = mtod(m, struct ip *);
  570                 nth = (struct tcphdr *)(ip + 1);
  571               }
  572                 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
  573                 flags = TH_ACK;
  574         } else {
  575                 /*
  576                  *  reuse the mbuf. 
  577                  * XXX MRT We inherrit the FIB, which is lucky.
  578                  */
  579                 m_freem(m->m_next);
  580                 m->m_next = NULL;
  581                 m->m_data = (caddr_t)ipgen;
  582                 /* m_len is set later */
  583                 tlen = 0;
  584 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
  585 #ifdef INET6
  586                 if (isipv6) {
  587                         xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
  588                         nth = (struct tcphdr *)(ip6 + 1);
  589                 } else
  590 #endif /* INET6 */
  591               {
  592                 xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
  593                 nth = (struct tcphdr *)(ip + 1);
  594               }
  595                 if (th != nth) {
  596                         /*
  597                          * this is usually a case when an extension header
  598                          * exists between the IPv6 header and the
  599                          * TCP header.
  600                          */
  601                         nth->th_sport = th->th_sport;
  602                         nth->th_dport = th->th_dport;
  603                 }
  604                 xchg(nth->th_dport, nth->th_sport, uint16_t);
  605 #undef xchg
  606         }
  607 #ifdef INET6
  608         if (isipv6) {
  609                 ip6->ip6_flow = 0;
  610                 ip6->ip6_vfc = IPV6_VERSION;
  611                 ip6->ip6_nxt = IPPROTO_TCP;
  612                 ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) +
  613                                                 tlen));
  614                 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
  615         } else
  616 #endif
  617         {
  618                 tlen += sizeof (struct tcpiphdr);
  619                 ip->ip_len = tlen;
  620                 ip->ip_ttl = V_ip_defttl;
  621                 if (V_path_mtu_discovery)
  622                         ip->ip_off |= IP_DF;
  623         }
  624         m->m_len = tlen;
  625         m->m_pkthdr.len = tlen;
  626         m->m_pkthdr.rcvif = NULL;
  627 #ifdef MAC
  628         if (inp != NULL) {
  629                 /*
  630                  * Packet is associated with a socket, so allow the
  631                  * label of the response to reflect the socket label.
  632                  */
  633                 INP_WLOCK_ASSERT(inp);
  634                 mac_inpcb_create_mbuf(inp, m);
  635         } else {
  636                 /*
  637                  * Packet is not associated with a socket, so possibly
  638                  * update the label in place.
  639                  */
  640                 mac_netinet_tcp_reply(m);
  641         }
  642 #endif
  643         nth->th_seq = htonl(seq);
  644         nth->th_ack = htonl(ack);
  645         nth->th_x2 = 0;
  646         nth->th_off = sizeof (struct tcphdr) >> 2;
  647         nth->th_flags = flags;
  648         if (tp != NULL)
  649                 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
  650         else
  651                 nth->th_win = htons((u_short)win);
  652         nth->th_urp = 0;
  653 #ifdef INET6
  654         if (isipv6) {
  655                 nth->th_sum = 0;
  656                 nth->th_sum = in6_cksum(m, IPPROTO_TCP,
  657                                         sizeof(struct ip6_hdr),
  658                                         tlen - sizeof(struct ip6_hdr));
  659                 ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
  660                     NULL, NULL);
  661         } else
  662 #endif /* INET6 */
  663         {
  664                 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
  665                     htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
  666                 m->m_pkthdr.csum_flags = CSUM_TCP;
  667                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
  668         }
  669 #ifdef TCPDEBUG
  670         if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
  671                 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
  672 #endif
  673 #ifdef INET6
  674         if (isipv6)
  675                 (void) ip6_output(m, NULL, NULL, ipflags, NULL, NULL, inp);
  676         else
  677 #endif /* INET6 */
  678         (void) ip_output(m, NULL, NULL, ipflags, NULL, inp);
  679 }
  680 
  681 /*
  682  * Create a new TCP control block, making an
  683  * empty reassembly queue and hooking it to the argument
  684  * protocol control block.  The `inp' parameter must have
  685  * come from the zone allocator set up in tcp_init().
  686  */
  687 struct tcpcb *
  688 tcp_newtcpcb(struct inpcb *inp)
  689 {
  690         struct tcpcb_mem *tm;
  691         struct tcpcb *tp;
  692 #ifdef INET6
  693         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  694 #endif /* INET6 */
  695 
  696         tm = uma_zalloc(V_tcpcb_zone, M_NOWAIT | M_ZERO);
  697         if (tm == NULL)
  698                 return (NULL);
  699         tp = &tm->tcb;
  700 #ifdef VIMAGE
  701         tp->t_vnet = inp->inp_vnet;
  702 #endif
  703         tp->t_timers = &tm->tt;
  704         /*      LIST_INIT(&tp->t_segq); */      /* XXX covered by M_ZERO */
  705         tp->t_maxseg = tp->t_maxopd =
  706 #ifdef INET6
  707                 isipv6 ? V_tcp_v6mssdflt :
  708 #endif /* INET6 */
  709                 V_tcp_mssdflt;
  710 
  711         /* Set up our timeouts. */
  712         callout_init(&tp->t_timers->tt_rexmt, CALLOUT_MPSAFE);
  713         callout_init(&tp->t_timers->tt_persist, CALLOUT_MPSAFE);
  714         callout_init(&tp->t_timers->tt_keep, CALLOUT_MPSAFE);
  715         callout_init(&tp->t_timers->tt_2msl, CALLOUT_MPSAFE);
  716         callout_init(&tp->t_timers->tt_delack, CALLOUT_MPSAFE);
  717 
  718         if (V_tcp_do_rfc1323)
  719                 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
  720         if (V_tcp_do_sack)
  721                 tp->t_flags |= TF_SACK_PERMIT;
  722         TAILQ_INIT(&tp->snd_holes);
  723         tp->t_inpcb = inp;      /* XXX */
  724         /*
  725          * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
  726          * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
  727          * reasonable initial retransmit time.
  728          */
  729         tp->t_srtt = TCPTV_SRTTBASE;
  730         tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
  731         tp->t_rttmin = tcp_rexmit_min;
  732         tp->t_rxtcur = TCPTV_RTOBASE;
  733         tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  734         tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  735         tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  736         tp->t_rcvtime = ticks;
  737         tp->t_bw_rtttime = ticks;
  738         /*
  739          * IPv4 TTL initialization is necessary for an IPv6 socket as well,
  740          * because the socket may be bound to an IPv6 wildcard address,
  741          * which may match an IPv4-mapped IPv6 address.
  742          */
  743         inp->inp_ip_ttl = V_ip_defttl;
  744         inp->inp_ppcb = tp;
  745         return (tp);            /* XXX */
  746 }
  747 
  748 /*
  749  * Drop a TCP connection, reporting
  750  * the specified error.  If connection is synchronized,
  751  * then send a RST to peer.
  752  */
  753 struct tcpcb *
  754 tcp_drop(struct tcpcb *tp, int errno)
  755 {
  756         struct socket *so = tp->t_inpcb->inp_socket;
  757 
  758         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
  759         INP_WLOCK_ASSERT(tp->t_inpcb);
  760 
  761         if (TCPS_HAVERCVDSYN(tp->t_state)) {
  762                 tp->t_state = TCPS_CLOSED;
  763                 (void) tcp_output_reset(tp);
  764                 TCPSTAT_INC(tcps_drops);
  765         } else
  766                 TCPSTAT_INC(tcps_conndrops);
  767         if (errno == ETIMEDOUT && tp->t_softerror)
  768                 errno = tp->t_softerror;
  769         so->so_error = errno;
  770         return (tcp_close(tp));
  771 }
  772 
  773 void
  774 tcp_discardcb(struct tcpcb *tp)
  775 {
  776         struct tseg_qent *q;
  777         struct inpcb *inp = tp->t_inpcb;
  778         struct socket *so = inp->inp_socket;
  779 #ifdef INET6
  780         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  781 #endif /* INET6 */
  782 
  783         INP_WLOCK_ASSERT(inp);
  784 
  785         /*
  786          * Make sure that all of our timers are stopped before we
  787          * delete the PCB.
  788          */
  789         callout_stop(&tp->t_timers->tt_rexmt);
  790         callout_stop(&tp->t_timers->tt_persist);
  791         callout_stop(&tp->t_timers->tt_keep);
  792         callout_stop(&tp->t_timers->tt_2msl);
  793         callout_stop(&tp->t_timers->tt_delack);
  794 
  795         /*
  796          * If we got enough samples through the srtt filter,
  797          * save the rtt and rttvar in the routing entry.
  798          * 'Enough' is arbitrarily defined as 4 rtt samples.
  799          * 4 samples is enough for the srtt filter to converge
  800          * to within enough % of the correct value; fewer samples
  801          * and we could save a bogus rtt. The danger is not high
  802          * as tcp quickly recovers from everything.
  803          * XXX: Works very well but needs some more statistics!
  804          */
  805         if (tp->t_rttupdated >= 4) {
  806                 struct hc_metrics_lite metrics;
  807                 u_long ssthresh;
  808 
  809                 bzero(&metrics, sizeof(metrics));
  810                 /*
  811                  * Update the ssthresh always when the conditions below
  812                  * are satisfied. This gives us better new start value
  813                  * for the congestion avoidance for new connections.
  814                  * ssthresh is only set if packet loss occured on a session.
  815                  *
  816                  * XXXRW: 'so' may be NULL here, and/or socket buffer may be
  817                  * being torn down.  Ideally this code would not use 'so'.
  818                  */
  819                 ssthresh = tp->snd_ssthresh;
  820                 if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
  821                         /*
  822                          * convert the limit from user data bytes to
  823                          * packets then to packet data bytes.
  824                          */
  825                         ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
  826                         if (ssthresh < 2)
  827                                 ssthresh = 2;
  828                         ssthresh *= (u_long)(tp->t_maxseg +
  829 #ifdef INET6
  830                                       (isipv6 ? sizeof (struct ip6_hdr) +
  831                                                sizeof (struct tcphdr) :
  832 #endif
  833                                        sizeof (struct tcpiphdr)
  834 #ifdef INET6
  835                                        )
  836 #endif
  837                                       );
  838                 } else
  839                         ssthresh = 0;
  840                 metrics.rmx_ssthresh = ssthresh;
  841 
  842                 metrics.rmx_rtt = tp->t_srtt;
  843                 metrics.rmx_rttvar = tp->t_rttvar;
  844                 /* XXX: This wraps if the pipe is more than 4 Gbit per second */
  845                 metrics.rmx_bandwidth = tp->snd_bandwidth;
  846                 metrics.rmx_cwnd = tp->snd_cwnd;
  847                 metrics.rmx_sendpipe = 0;
  848                 metrics.rmx_recvpipe = 0;
  849 
  850                 tcp_hc_update(&inp->inp_inc, &metrics);
  851         }
  852 
  853         /* free the reassembly queue, if any */
  854         while ((q = LIST_FIRST(&tp->t_segq)) != NULL) {
  855                 LIST_REMOVE(q, tqe_q);
  856                 m_freem(q->tqe_m);
  857                 uma_zfree(V_tcp_reass_zone, q);
  858                 tp->t_segqlen--;
  859                 V_tcp_reass_qsize--;
  860         }
  861         /* Disconnect offload device, if any. */
  862         tcp_offload_detach(tp);
  863                 
  864         tcp_free_sackholes(tp);
  865         inp->inp_ppcb = NULL;
  866         tp->t_inpcb = NULL;
  867         uma_zfree(V_tcpcb_zone, tp);
  868 }
  869 
  870 /*
  871  * Attempt to close a TCP control block, marking it as dropped, and freeing
  872  * the socket if we hold the only reference.
  873  */
  874 struct tcpcb *
  875 tcp_close(struct tcpcb *tp)
  876 {
  877         struct inpcb *inp = tp->t_inpcb;
  878         struct socket *so;
  879 
  880         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
  881         INP_WLOCK_ASSERT(inp);
  882 
  883         /* Notify any offload devices of listener close */
  884         if (tp->t_state == TCPS_LISTEN)
  885                 tcp_offload_listen_close(tp);
  886         in_pcbdrop(inp);
  887         TCPSTAT_INC(tcps_closed);
  888         KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
  889         so = inp->inp_socket;
  890         soisdisconnected(so);
  891         if (inp->inp_flags & INP_SOCKREF) {
  892                 KASSERT(so->so_state & SS_PROTOREF,
  893                     ("tcp_close: !SS_PROTOREF"));
  894                 inp->inp_flags &= ~INP_SOCKREF;
  895                 INP_WUNLOCK(inp);
  896                 ACCEPT_LOCK();
  897                 SOCK_LOCK(so);
  898                 so->so_state &= ~SS_PROTOREF;
  899                 sofree(so);
  900                 return (NULL);
  901         }
  902         return (tp);
  903 }
  904 
  905 void
  906 tcp_drain(void)
  907 {
  908         VNET_ITERATOR_DECL(vnet_iter);
  909 
  910         if (!do_tcpdrain)
  911                 return;
  912 
  913         VNET_LIST_RLOCK_NOSLEEP();
  914         VNET_FOREACH(vnet_iter) {
  915                 CURVNET_SET(vnet_iter);
  916                 struct inpcb *inpb;
  917                 struct tcpcb *tcpb;
  918                 struct tseg_qent *te;
  919 
  920         /*
  921          * Walk the tcpbs, if existing, and flush the reassembly queue,
  922          * if there is one...
  923          * XXX: The "Net/3" implementation doesn't imply that the TCP
  924          *      reassembly queue should be flushed, but in a situation
  925          *      where we're really low on mbufs, this is potentially
  926          *      usefull.
  927          */
  928                 INP_INFO_RLOCK(&V_tcbinfo);
  929                 LIST_FOREACH(inpb, V_tcbinfo.ipi_listhead, inp_list) {
  930                         if (inpb->inp_flags & INP_TIMEWAIT)
  931                                 continue;
  932                         INP_WLOCK(inpb);
  933                         if ((tcpb = intotcpcb(inpb)) != NULL) {
  934                                 while ((te = LIST_FIRST(&tcpb->t_segq))
  935                                     != NULL) {
  936                                         LIST_REMOVE(te, tqe_q);
  937                                         m_freem(te->tqe_m);
  938                                         uma_zfree(V_tcp_reass_zone, te);
  939                                         tcpb->t_segqlen--;
  940                                         V_tcp_reass_qsize--;
  941                                 }
  942                                 tcp_clean_sackreport(tcpb);
  943                         }
  944                         INP_WUNLOCK(inpb);
  945                 }
  946                 INP_INFO_RUNLOCK(&V_tcbinfo);
  947                 CURVNET_RESTORE();
  948         }
  949         VNET_LIST_RUNLOCK_NOSLEEP();
  950 }
  951 
  952 /*
  953  * Notify a tcp user of an asynchronous error;
  954  * store error as soft error, but wake up user
  955  * (for now, won't do anything until can select for soft error).
  956  *
  957  * Do not wake up user since there currently is no mechanism for
  958  * reporting soft errors (yet - a kqueue filter may be added).
  959  */
  960 static struct inpcb *
  961 tcp_notify(struct inpcb *inp, int error)
  962 {
  963         struct tcpcb *tp;
  964 
  965         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
  966         INP_WLOCK_ASSERT(inp);
  967 
  968         if ((inp->inp_flags & INP_TIMEWAIT) ||
  969             (inp->inp_flags & INP_DROPPED))
  970                 return (inp);
  971 
  972         tp = intotcpcb(inp);
  973         KASSERT(tp != NULL, ("tcp_notify: tp == NULL"));
  974 
  975         /*
  976          * Ignore some errors if we are hooked up.
  977          * If connection hasn't completed, has retransmitted several times,
  978          * and receives a second error, give up now.  This is better
  979          * than waiting a long time to establish a connection that
  980          * can never complete.
  981          */
  982         if (tp->t_state == TCPS_ESTABLISHED &&
  983             (error == EHOSTUNREACH || error == ENETUNREACH ||
  984              error == EHOSTDOWN)) {
  985                 return (inp);
  986         } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
  987             tp->t_softerror) {
  988                 tp = tcp_drop(tp, error);
  989                 if (tp != NULL)
  990                         return (inp);
  991                 else
  992                         return (NULL);
  993         } else {
  994                 tp->t_softerror = error;
  995                 return (inp);
  996         }
  997 #if 0
  998         wakeup( &so->so_timeo);
  999         sorwakeup(so);
 1000         sowwakeup(so);
 1001 #endif
 1002 }
 1003 
 1004 static int
 1005 tcp_pcblist(SYSCTL_HANDLER_ARGS)
 1006 {
 1007         int error, i, m, n, pcb_count;
 1008         struct inpcb *inp, **inp_list;
 1009         inp_gen_t gencnt;
 1010         struct xinpgen xig;
 1011 
 1012         /*
 1013          * The process of preparing the TCB list is too time-consuming and
 1014          * resource-intensive to repeat twice on every request.
 1015          */
 1016         if (req->oldptr == NULL) {
 1017                 m = syncache_pcbcount();
 1018                 n = V_tcbinfo.ipi_count;
 1019                 req->oldidx = 2 * (sizeof xig)
 1020                         + ((m + n) + n/8) * sizeof(struct xtcpcb);
 1021                 return (0);
 1022         }
 1023 
 1024         if (req->newptr != NULL)
 1025                 return (EPERM);
 1026 
 1027         /*
 1028          * OK, now we're committed to doing something.
 1029          */
 1030         INP_INFO_RLOCK(&V_tcbinfo);
 1031         gencnt = V_tcbinfo.ipi_gencnt;
 1032         n = V_tcbinfo.ipi_count;
 1033         INP_INFO_RUNLOCK(&V_tcbinfo);
 1034 
 1035         m = syncache_pcbcount();
 1036 
 1037         error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
 1038                 + (n + m) * sizeof(struct xtcpcb));
 1039         if (error != 0)
 1040                 return (error);
 1041 
 1042         xig.xig_len = sizeof xig;
 1043         xig.xig_count = n + m;
 1044         xig.xig_gen = gencnt;
 1045         xig.xig_sogen = so_gencnt;
 1046         error = SYSCTL_OUT(req, &xig, sizeof xig);
 1047         if (error)
 1048                 return (error);
 1049 
 1050         error = syncache_pcblist(req, m, &pcb_count);
 1051         if (error)
 1052                 return (error);
 1053 
 1054         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
 1055         if (inp_list == NULL)
 1056                 return (ENOMEM);
 1057 
 1058         INP_INFO_RLOCK(&V_tcbinfo);
 1059         for (inp = LIST_FIRST(V_tcbinfo.ipi_listhead), i = 0;
 1060             inp != NULL && i < n; inp = LIST_NEXT(inp, inp_list)) {
 1061                 INP_WLOCK(inp);
 1062                 if (inp->inp_gencnt <= gencnt) {
 1063                         /*
 1064                          * XXX: This use of cr_cansee(), introduced with
 1065                          * TCP state changes, is not quite right, but for
 1066                          * now, better than nothing.
 1067                          */
 1068                         if (inp->inp_flags & INP_TIMEWAIT) {
 1069                                 if (intotw(inp) != NULL)
 1070                                         error = cr_cansee(req->td->td_ucred,
 1071                                             intotw(inp)->tw_cred);
 1072                                 else
 1073                                         error = EINVAL; /* Skip this inp. */
 1074                         } else
 1075                                 error = cr_canseeinpcb(req->td->td_ucred, inp);
 1076                         if (error == 0) {
 1077                                 in_pcbref(inp);
 1078                                 inp_list[i++] = inp;
 1079                         }
 1080                 }
 1081                 INP_WUNLOCK(inp);
 1082         }
 1083         INP_INFO_RUNLOCK(&V_tcbinfo);
 1084         n = i;
 1085 
 1086         error = 0;
 1087         for (i = 0; i < n; i++) {
 1088                 inp = inp_list[i];
 1089                 INP_RLOCK(inp);
 1090                 if (inp->inp_gencnt <= gencnt) {
 1091                         struct xtcpcb xt;
 1092                         void *inp_ppcb;
 1093 
 1094                         bzero(&xt, sizeof(xt));
 1095                         xt.xt_len = sizeof xt;
 1096                         /* XXX should avoid extra copy */
 1097                         bcopy(inp, &xt.xt_inp, sizeof *inp);
 1098                         inp_ppcb = inp->inp_ppcb;
 1099                         if (inp_ppcb == NULL)
 1100                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1101                         else if (inp->inp_flags & INP_TIMEWAIT) {
 1102                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1103                                 xt.xt_tp.t_state = TCPS_TIME_WAIT;
 1104                         } else
 1105                                 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
 1106                         if (inp->inp_socket != NULL)
 1107                                 sotoxsocket(inp->inp_socket, &xt.xt_socket);
 1108                         else {
 1109                                 bzero(&xt.xt_socket, sizeof xt.xt_socket);
 1110                                 xt.xt_socket.xso_protocol = IPPROTO_TCP;
 1111                         }
 1112                         xt.xt_inp.inp_gencnt = inp->inp_gencnt;
 1113                         INP_RUNLOCK(inp);
 1114                         error = SYSCTL_OUT(req, &xt, sizeof xt);
 1115                 } else
 1116                         INP_RUNLOCK(inp);
 1117         }
 1118         INP_INFO_WLOCK(&V_tcbinfo);
 1119         for (i = 0; i < n; i++) {
 1120                 inp = inp_list[i];
 1121                 INP_WLOCK(inp);
 1122                 if (!in_pcbrele(inp))
 1123                         INP_WUNLOCK(inp);
 1124         }
 1125         INP_INFO_WUNLOCK(&V_tcbinfo);
 1126 
 1127         if (!error) {
 1128                 /*
 1129                  * Give the user an updated idea of our state.
 1130                  * If the generation differs from what we told
 1131                  * her before, she knows that something happened
 1132                  * while we were processing this request, and it
 1133                  * might be necessary to retry.
 1134                  */
 1135                 INP_INFO_RLOCK(&V_tcbinfo);
 1136                 xig.xig_gen = V_tcbinfo.ipi_gencnt;
 1137                 xig.xig_sogen = so_gencnt;
 1138                 xig.xig_count = V_tcbinfo.ipi_count + pcb_count;
 1139                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1140                 error = SYSCTL_OUT(req, &xig, sizeof xig);
 1141         }
 1142         free(inp_list, M_TEMP);
 1143         return (error);
 1144 }
 1145 
 1146 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
 1147     tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
 1148 
 1149 static int
 1150 tcp_getcred(SYSCTL_HANDLER_ARGS)
 1151 {
 1152         struct xucred xuc;
 1153         struct sockaddr_in addrs[2];
 1154         struct inpcb *inp;
 1155         int error;
 1156 
 1157         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1158         if (error)
 1159                 return (error);
 1160         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1161         if (error)
 1162                 return (error);
 1163         INP_INFO_RLOCK(&V_tcbinfo);
 1164         inp = in_pcblookup_hash(&V_tcbinfo, addrs[1].sin_addr,
 1165             addrs[1].sin_port, addrs[0].sin_addr, addrs[0].sin_port, 0, NULL);
 1166         if (inp != NULL) {
 1167                 INP_RLOCK(inp);
 1168                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1169                 if (inp->inp_socket == NULL)
 1170                         error = ENOENT;
 1171                 if (error == 0)
 1172                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1173                 if (error == 0)
 1174                         cru2x(inp->inp_cred, &xuc);
 1175                 INP_RUNLOCK(inp);
 1176         } else {
 1177                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1178                 error = ENOENT;
 1179         }
 1180         if (error == 0)
 1181                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1182         return (error);
 1183 }
 1184 
 1185 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
 1186     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1187     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
 1188 
 1189 #ifdef INET6
 1190 static int
 1191 tcp6_getcred(SYSCTL_HANDLER_ARGS)
 1192 {
 1193         struct xucred xuc;
 1194         struct sockaddr_in6 addrs[2];
 1195         struct inpcb *inp;
 1196         int error, mapped = 0;
 1197 
 1198         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1199         if (error)
 1200                 return (error);
 1201         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1202         if (error)
 1203                 return (error);
 1204         if ((error = sa6_embedscope(&addrs[0], V_ip6_use_defzone)) != 0 ||
 1205             (error = sa6_embedscope(&addrs[1], V_ip6_use_defzone)) != 0) {
 1206                 return (error);
 1207         }
 1208         if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
 1209                 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
 1210                         mapped = 1;
 1211                 else
 1212                         return (EINVAL);
 1213         }
 1214 
 1215         INP_INFO_RLOCK(&V_tcbinfo);
 1216         if (mapped == 1)
 1217                 inp = in_pcblookup_hash(&V_tcbinfo,
 1218                         *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
 1219                         addrs[1].sin6_port,
 1220                         *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
 1221                         addrs[0].sin6_port,
 1222                         0, NULL);
 1223         else
 1224                 inp = in6_pcblookup_hash(&V_tcbinfo,
 1225                         &addrs[1].sin6_addr, addrs[1].sin6_port,
 1226                         &addrs[0].sin6_addr, addrs[0].sin6_port, 0, NULL);
 1227         if (inp != NULL) {
 1228                 INP_RLOCK(inp);
 1229                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1230                 if (inp->inp_socket == NULL)
 1231                         error = ENOENT;
 1232                 if (error == 0)
 1233                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1234                 if (error == 0)
 1235                         cru2x(inp->inp_cred, &xuc);
 1236                 INP_RUNLOCK(inp);
 1237         } else {
 1238                 INP_INFO_RUNLOCK(&V_tcbinfo);
 1239                 error = ENOENT;
 1240         }
 1241         if (error == 0)
 1242                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1243         return (error);
 1244 }
 1245 
 1246 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 1247     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1248     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
 1249 #endif
 1250 
 1251 
 1252 void
 1253 tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
 1254 {
 1255         struct ip *ip = vip;
 1256         struct tcphdr *th;
 1257         struct in_addr faddr;
 1258         struct inpcb *inp;
 1259         struct tcpcb *tp;
 1260         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1261         struct icmp *icp;
 1262         struct in_conninfo inc;
 1263         tcp_seq icmp_tcp_seq;
 1264         int mtu;
 1265 
 1266         faddr = ((struct sockaddr_in *)sa)->sin_addr;
 1267         if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
 1268                 return;
 1269 
 1270         if (cmd == PRC_MSGSIZE)
 1271                 notify = tcp_mtudisc;
 1272         else if (V_icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
 1273                 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
 1274                 notify = tcp_drop_syn_sent;
 1275         /*
 1276          * Redirects don't need to be handled up here.
 1277          */
 1278         else if (PRC_IS_REDIRECT(cmd))
 1279                 return;
 1280         /*
 1281          * Source quench is depreciated.
 1282          */
 1283         else if (cmd == PRC_QUENCH)
 1284                 return;
 1285         /*
 1286          * Hostdead is ugly because it goes linearly through all PCBs.
 1287          * XXX: We never get this from ICMP, otherwise it makes an
 1288          * excellent DoS attack on machines with many connections.
 1289          */
 1290         else if (cmd == PRC_HOSTDEAD)
 1291                 ip = NULL;
 1292         else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
 1293                 return;
 1294         if (ip != NULL) {
 1295                 icp = (struct icmp *)((caddr_t)ip
 1296                                       - offsetof(struct icmp, icmp_ip));
 1297                 th = (struct tcphdr *)((caddr_t)ip
 1298                                        + (ip->ip_hl << 2));
 1299                 INP_INFO_WLOCK(&V_tcbinfo);
 1300                 inp = in_pcblookup_hash(&V_tcbinfo, faddr, th->th_dport,
 1301                     ip->ip_src, th->th_sport, 0, NULL);
 1302                 if (inp != NULL)  {
 1303                         INP_WLOCK(inp);
 1304                         if (!(inp->inp_flags & INP_TIMEWAIT) &&
 1305                             !(inp->inp_flags & INP_DROPPED) &&
 1306                             !(inp->inp_socket == NULL)) {
 1307                                 icmp_tcp_seq = htonl(th->th_seq);
 1308                                 tp = intotcpcb(inp);
 1309                                 if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
 1310                                     SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
 1311                                         if (cmd == PRC_MSGSIZE) {
 1312                                             /*
 1313                                              * MTU discovery:
 1314                                              * If we got a needfrag set the MTU
 1315                                              * in the route to the suggested new
 1316                                              * value (if given) and then notify.
 1317                                              */
 1318                                             bzero(&inc, sizeof(inc));
 1319                                             inc.inc_faddr = faddr;
 1320                                             inc.inc_fibnum =
 1321                                                 inp->inp_inc.inc_fibnum;
 1322 
 1323                                             mtu = ntohs(icp->icmp_nextmtu);
 1324                                             /*
 1325                                              * If no alternative MTU was
 1326                                              * proposed, try the next smaller
 1327                                              * one.  ip->ip_len has already
 1328                                              * been swapped in icmp_input().
 1329                                              */
 1330                                             if (!mtu)
 1331                                                 mtu = ip_next_mtu(ip->ip_len,
 1332                                                  1);
 1333                                             if (mtu < max(296, V_tcp_minmss
 1334                                                  + sizeof(struct tcpiphdr)))
 1335                                                 mtu = 0;
 1336                                             if (!mtu)
 1337                                                 mtu = V_tcp_mssdflt
 1338                                                  + sizeof(struct tcpiphdr);
 1339                                             /*
 1340                                              * Only cache the the MTU if it
 1341                                              * is smaller than the interface
 1342                                              * or route MTU.  tcp_mtudisc()
 1343                                              * will do right thing by itself.
 1344                                              */
 1345                                             if (mtu <= tcp_maxmtu(&inc, NULL))
 1346                                                 tcp_hc_updatemtu(&inc, mtu);
 1347                                         }
 1348 
 1349                                         inp = (*notify)(inp, inetctlerrmap[cmd]);
 1350                                 }
 1351                         }
 1352                         if (inp != NULL)
 1353                                 INP_WUNLOCK(inp);
 1354                 } else {
 1355                         bzero(&inc, sizeof(inc));
 1356                         inc.inc_fport = th->th_dport;
 1357                         inc.inc_lport = th->th_sport;
 1358                         inc.inc_faddr = faddr;
 1359                         inc.inc_laddr = ip->ip_src;
 1360                         syncache_unreach(&inc, th);
 1361                 }
 1362                 INP_INFO_WUNLOCK(&V_tcbinfo);
 1363         } else
 1364                 in_pcbnotifyall(&V_tcbinfo, faddr, inetctlerrmap[cmd], notify);
 1365 }
 1366 
 1367 #ifdef INET6
 1368 void
 1369 tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
 1370 {
 1371         struct tcphdr th;
 1372         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1373         struct ip6_hdr *ip6;
 1374         struct mbuf *m;
 1375         struct ip6ctlparam *ip6cp = NULL;
 1376         const struct sockaddr_in6 *sa6_src = NULL;
 1377         int off;
 1378         struct tcp_portonly {
 1379                 u_int16_t th_sport;
 1380                 u_int16_t th_dport;
 1381         } *thp;
 1382 
 1383         if (sa->sa_family != AF_INET6 ||
 1384             sa->sa_len != sizeof(struct sockaddr_in6))
 1385                 return;
 1386 
 1387         if (cmd == PRC_MSGSIZE)
 1388                 notify = tcp_mtudisc;
 1389         else if (!PRC_IS_REDIRECT(cmd) &&
 1390                  ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
 1391                 return;
 1392         /* Source quench is depreciated. */
 1393         else if (cmd == PRC_QUENCH)
 1394                 return;
 1395 
 1396         /* if the parameter is from icmp6, decode it. */
 1397         if (d != NULL) {
 1398                 ip6cp = (struct ip6ctlparam *)d;
 1399                 m = ip6cp->ip6c_m;
 1400                 ip6 = ip6cp->ip6c_ip6;
 1401                 off = ip6cp->ip6c_off;
 1402                 sa6_src = ip6cp->ip6c_src;
 1403         } else {
 1404                 m = NULL;
 1405                 ip6 = NULL;
 1406                 off = 0;        /* fool gcc */
 1407                 sa6_src = &sa6_any;
 1408         }
 1409 
 1410         if (ip6 != NULL) {
 1411                 struct in_conninfo inc;
 1412                 /*
 1413                  * XXX: We assume that when IPV6 is non NULL,
 1414                  * M and OFF are valid.
 1415                  */
 1416 
 1417                 /* check if we can safely examine src and dst ports */
 1418                 if (m->m_pkthdr.len < off + sizeof(*thp))
 1419                         return;
 1420 
 1421                 bzero(&th, sizeof(th));
 1422                 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
 1423 
 1424                 in6_pcbnotify(&V_tcbinfo, sa, th.th_dport,
 1425                     (struct sockaddr *)ip6cp->ip6c_src,
 1426                     th.th_sport, cmd, NULL, notify);
 1427 
 1428                 bzero(&inc, sizeof(inc));
 1429                 inc.inc_fport = th.th_dport;
 1430                 inc.inc_lport = th.th_sport;
 1431                 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
 1432                 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
 1433                 inc.inc_flags |= INC_ISIPV6;
 1434                 INP_INFO_WLOCK(&V_tcbinfo);
 1435                 syncache_unreach(&inc, &th);
 1436                 INP_INFO_WUNLOCK(&V_tcbinfo);
 1437         } else
 1438                 in6_pcbnotify(&V_tcbinfo, sa, 0, (const struct sockaddr *)sa6_src,
 1439                               0, cmd, NULL, notify);
 1440 }
 1441 #endif /* INET6 */
 1442 
 1443 
 1444 /*
 1445  * Following is where TCP initial sequence number generation occurs.
 1446  *
 1447  * There are two places where we must use initial sequence numbers:
 1448  * 1.  In SYN-ACK packets.
 1449  * 2.  In SYN packets.
 1450  *
 1451  * All ISNs for SYN-ACK packets are generated by the syncache.  See
 1452  * tcp_syncache.c for details.
 1453  *
 1454  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 1455  * depends on this property.  In addition, these ISNs should be
 1456  * unguessable so as to prevent connection hijacking.  To satisfy
 1457  * the requirements of this situation, the algorithm outlined in
 1458  * RFC 1948 is used, with only small modifications.
 1459  *
 1460  * Implementation details:
 1461  *
 1462  * Time is based off the system timer, and is corrected so that it
 1463  * increases by one megabyte per second.  This allows for proper
 1464  * recycling on high speed LANs while still leaving over an hour
 1465  * before rollover.
 1466  *
 1467  * As reading the *exact* system time is too expensive to be done
 1468  * whenever setting up a TCP connection, we increment the time
 1469  * offset in two ways.  First, a small random positive increment
 1470  * is added to isn_offset for each connection that is set up.
 1471  * Second, the function tcp_isn_tick fires once per clock tick
 1472  * and increments isn_offset as necessary so that sequence numbers
 1473  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
 1474  * random positive increments serve only to ensure that the same
 1475  * exact sequence number is never sent out twice (as could otherwise
 1476  * happen when a port is recycled in less than the system tick
 1477  * interval.)
 1478  *
 1479  * net.inet.tcp.isn_reseed_interval controls the number of seconds
 1480  * between seeding of isn_secret.  This is normally set to zero,
 1481  * as reseeding should not be necessary.
 1482  *
 1483  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
 1484  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
 1485  * general, this means holding an exclusive (write) lock.
 1486  */
 1487 
 1488 #define ISN_BYTES_PER_SECOND 1048576
 1489 #define ISN_STATIC_INCREMENT 4096
 1490 #define ISN_RANDOM_INCREMENT (4096 - 1)
 1491 
 1492 static VNET_DEFINE(u_char, isn_secret[32]);
 1493 static VNET_DEFINE(int, isn_last_reseed);
 1494 static VNET_DEFINE(u_int32_t, isn_offset);
 1495 static VNET_DEFINE(u_int32_t, isn_offset_old);
 1496 
 1497 #define V_isn_secret                    VNET(isn_secret)
 1498 #define V_isn_last_reseed               VNET(isn_last_reseed)
 1499 #define V_isn_offset                    VNET(isn_offset)
 1500 #define V_isn_offset_old                VNET(isn_offset_old)
 1501 
 1502 tcp_seq
 1503 tcp_new_isn(struct tcpcb *tp)
 1504 {
 1505         MD5_CTX isn_ctx;
 1506         u_int32_t md5_buffer[4];
 1507         tcp_seq new_isn;
 1508 
 1509         INP_WLOCK_ASSERT(tp->t_inpcb);
 1510 
 1511         ISN_LOCK();
 1512         /* Seed if this is the first use, reseed if requested. */
 1513         if ((V_isn_last_reseed == 0) || ((V_tcp_isn_reseed_interval > 0) &&
 1514              (((u_int)V_isn_last_reseed + (u_int)V_tcp_isn_reseed_interval*hz)
 1515                 < (u_int)ticks))) {
 1516                 read_random(&V_isn_secret, sizeof(V_isn_secret));
 1517                 V_isn_last_reseed = ticks;
 1518         }
 1519 
 1520         /* Compute the md5 hash and return the ISN. */
 1521         MD5Init(&isn_ctx);
 1522         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
 1523         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
 1524 #ifdef INET6
 1525         if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
 1526                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
 1527                           sizeof(struct in6_addr));
 1528                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
 1529                           sizeof(struct in6_addr));
 1530         } else
 1531 #endif
 1532         {
 1533                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
 1534                           sizeof(struct in_addr));
 1535                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
 1536                           sizeof(struct in_addr));
 1537         }
 1538         MD5Update(&isn_ctx, (u_char *) &V_isn_secret, sizeof(V_isn_secret));
 1539         MD5Final((u_char *) &md5_buffer, &isn_ctx);
 1540         new_isn = (tcp_seq) md5_buffer[0];
 1541         V_isn_offset += ISN_STATIC_INCREMENT +
 1542                 (arc4random() & ISN_RANDOM_INCREMENT);
 1543         new_isn += V_isn_offset;
 1544         ISN_UNLOCK();
 1545         return (new_isn);
 1546 }
 1547 
 1548 /*
 1549  * Increment the offset to the next ISN_BYTES_PER_SECOND / 100 boundary
 1550  * to keep time flowing at a relatively constant rate.  If the random
 1551  * increments have already pushed us past the projected offset, do nothing.
 1552  */
 1553 static void
 1554 tcp_isn_tick(void *xtp)
 1555 {
 1556         VNET_ITERATOR_DECL(vnet_iter);
 1557         u_int32_t projected_offset;
 1558 
 1559         VNET_LIST_RLOCK_NOSLEEP();
 1560         ISN_LOCK();
 1561         VNET_FOREACH(vnet_iter) {
 1562                 CURVNET_SET(vnet_iter); /* XXX appease INVARIANTS */
 1563                 projected_offset =
 1564                     V_isn_offset_old + ISN_BYTES_PER_SECOND / 100;
 1565 
 1566                 if (SEQ_GT(projected_offset, V_isn_offset))
 1567                         V_isn_offset = projected_offset;
 1568 
 1569                 V_isn_offset_old = V_isn_offset;
 1570                 CURVNET_RESTORE();
 1571         }
 1572         ISN_UNLOCK();
 1573         VNET_LIST_RUNLOCK_NOSLEEP();
 1574         callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
 1575 }
 1576 
 1577 /*
 1578  * When a specific ICMP unreachable message is received and the
 1579  * connection state is SYN-SENT, drop the connection.  This behavior
 1580  * is controlled by the icmp_may_rst sysctl.
 1581  */
 1582 struct inpcb *
 1583 tcp_drop_syn_sent(struct inpcb *inp, int errno)
 1584 {
 1585         struct tcpcb *tp;
 1586 
 1587         INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
 1588         INP_WLOCK_ASSERT(inp);
 1589 
 1590         if ((inp->inp_flags & INP_TIMEWAIT) ||
 1591             (inp->inp_flags & INP_DROPPED))
 1592                 return (inp);
 1593 
 1594         tp = intotcpcb(inp);
 1595         if (tp->t_state != TCPS_SYN_SENT)
 1596                 return (inp);
 1597 
 1598         tp = tcp_drop(tp, errno);
 1599         if (tp != NULL)
 1600                 return (inp);
 1601         else
 1602                 return (NULL);
 1603 }
 1604 
 1605 /*
 1606  * When `need fragmentation' ICMP is received, update our idea of the MSS
 1607  * based on the new value in the route.  Also nudge TCP to send something,
 1608  * since we know the packet we just sent was dropped.
 1609  * This duplicates some code in the tcp_mss() function in tcp_input.c.
 1610  */
 1611 struct inpcb *
 1612 tcp_mtudisc(struct inpcb *inp, int errno)
 1613 {
 1614         struct tcpcb *tp;
 1615         struct socket *so;
 1616 
 1617         INP_WLOCK_ASSERT(inp);
 1618         if ((inp->inp_flags & INP_TIMEWAIT) ||
 1619             (inp->inp_flags & INP_DROPPED))
 1620                 return (inp);
 1621 
 1622         tp = intotcpcb(inp);
 1623         KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
 1624 
 1625         tcp_mss_update(tp, -1, NULL, NULL);
 1626   
 1627         so = inp->inp_socket;
 1628         SOCKBUF_LOCK(&so->so_snd);
 1629         /* If the mss is larger than the socket buffer, decrease the mss. */
 1630         if (so->so_snd.sb_hiwat < tp->t_maxseg)
 1631                 tp->t_maxseg = so->so_snd.sb_hiwat;
 1632         SOCKBUF_UNLOCK(&so->so_snd);
 1633 
 1634         TCPSTAT_INC(tcps_mturesent);
 1635         tp->t_rtttime = 0;
 1636         tp->snd_nxt = tp->snd_una;
 1637         tcp_free_sackholes(tp);
 1638         tp->snd_recover = tp->snd_max;
 1639         if (tp->t_flags & TF_SACK_PERMIT)
 1640                 EXIT_FASTRECOVERY(tp);
 1641         tcp_output_send(tp);
 1642         return (inp);
 1643 }
 1644 
 1645 /*
 1646  * Look-up the routing entry to the peer of this inpcb.  If no route
 1647  * is found and it cannot be allocated, then return 0.  This routine
 1648  * is called by TCP routines that access the rmx structure and by
 1649  * tcp_mss_update to get the peer/interface MTU.
 1650  */
 1651 u_long
 1652 tcp_maxmtu(struct in_conninfo *inc, int *flags)
 1653 {
 1654         struct route sro;
 1655         struct sockaddr_in *dst;
 1656         struct ifnet *ifp;
 1657         u_long maxmtu = 0;
 1658 
 1659         KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
 1660 
 1661         bzero(&sro, sizeof(sro));
 1662         if (inc->inc_faddr.s_addr != INADDR_ANY) {
 1663                 dst = (struct sockaddr_in *)&sro.ro_dst;
 1664                 dst->sin_family = AF_INET;
 1665                 dst->sin_len = sizeof(*dst);
 1666                 dst->sin_addr = inc->inc_faddr;
 1667                 in_rtalloc_ign(&sro, 0, inc->inc_fibnum);
 1668         }
 1669         if (sro.ro_rt != NULL) {
 1670                 ifp = sro.ro_rt->rt_ifp;
 1671                 if (sro.ro_rt->rt_rmx.rmx_mtu == 0)
 1672                         maxmtu = ifp->if_mtu;
 1673                 else
 1674                         maxmtu = min(sro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
 1675 
 1676                 /* Report additional interface capabilities. */
 1677                 if (flags != NULL) {
 1678                         if (ifp->if_capenable & IFCAP_TSO4 &&
 1679                             ifp->if_hwassist & CSUM_TSO)
 1680                                 *flags |= CSUM_TSO;
 1681                 }
 1682                 RTFREE(sro.ro_rt);
 1683         }
 1684         return (maxmtu);
 1685 }
 1686 
 1687 #ifdef INET6
 1688 u_long
 1689 tcp_maxmtu6(struct in_conninfo *inc, int *flags)
 1690 {
 1691         struct route_in6 sro6;
 1692         struct ifnet *ifp;
 1693         u_long maxmtu = 0;
 1694 
 1695         KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
 1696 
 1697         bzero(&sro6, sizeof(sro6));
 1698         if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
 1699                 sro6.ro_dst.sin6_family = AF_INET6;
 1700                 sro6.ro_dst.sin6_len = sizeof(struct sockaddr_in6);
 1701                 sro6.ro_dst.sin6_addr = inc->inc6_faddr;
 1702                 rtalloc_ign((struct route *)&sro6, 0);
 1703         }
 1704         if (sro6.ro_rt != NULL) {
 1705                 ifp = sro6.ro_rt->rt_ifp;
 1706                 if (sro6.ro_rt->rt_rmx.rmx_mtu == 0)
 1707                         maxmtu = IN6_LINKMTU(sro6.ro_rt->rt_ifp);
 1708                 else
 1709                         maxmtu = min(sro6.ro_rt->rt_rmx.rmx_mtu,
 1710                                      IN6_LINKMTU(sro6.ro_rt->rt_ifp));
 1711 
 1712                 /* Report additional interface capabilities. */
 1713                 if (flags != NULL) {
 1714                         if (ifp->if_capenable & IFCAP_TSO6 &&
 1715                             ifp->if_hwassist & CSUM_TSO)
 1716                                 *flags |= CSUM_TSO;
 1717                 }
 1718                 RTFREE(sro6.ro_rt);
 1719         }
 1720 
 1721         return (maxmtu);
 1722 }
 1723 #endif /* INET6 */
 1724 
 1725 #ifdef IPSEC
 1726 /* compute ESP/AH header size for TCP, including outer IP header. */
 1727 size_t
 1728 ipsec_hdrsiz_tcp(struct tcpcb *tp)
 1729 {
 1730         struct inpcb *inp;
 1731         struct mbuf *m;
 1732         size_t hdrsiz;
 1733         struct ip *ip;
 1734 #ifdef INET6
 1735         struct ip6_hdr *ip6;
 1736 #endif
 1737         struct tcphdr *th;
 1738 
 1739         if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
 1740                 return (0);
 1741         MGETHDR(m, M_DONTWAIT, MT_DATA);
 1742         if (!m)
 1743                 return (0);
 1744 
 1745 #ifdef INET6
 1746         if ((inp->inp_vflag & INP_IPV6) != 0) {
 1747                 ip6 = mtod(m, struct ip6_hdr *);
 1748                 th = (struct tcphdr *)(ip6 + 1);
 1749                 m->m_pkthdr.len = m->m_len =
 1750                         sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1751                 tcpip_fillheaders(inp, ip6, th);
 1752                 hdrsiz = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1753         } else
 1754 #endif /* INET6 */
 1755         {
 1756                 ip = mtod(m, struct ip *);
 1757                 th = (struct tcphdr *)(ip + 1);
 1758                 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
 1759                 tcpip_fillheaders(inp, ip, th);
 1760                 hdrsiz = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1761         }
 1762 
 1763         m_free(m);
 1764         return (hdrsiz);
 1765 }
 1766 #endif /* IPSEC */
 1767 
 1768 /*
 1769  * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING
 1770  *
 1771  * This code attempts to calculate the bandwidth-delay product as a
 1772  * means of determining the optimal window size to maximize bandwidth,
 1773  * minimize RTT, and avoid the over-allocation of buffers on interfaces and
 1774  * routers.  This code also does a fairly good job keeping RTTs in check
 1775  * across slow links like modems.  We implement an algorithm which is very
 1776  * similar (but not meant to be) TCP/Vegas.  The code operates on the
 1777  * transmitter side of a TCP connection and so only effects the transmit
 1778  * side of the connection.
 1779  *
 1780  * BACKGROUND:  TCP makes no provision for the management of buffer space
 1781  * at the end points or at the intermediate routers and switches.  A TCP
 1782  * stream, whether using NewReno or not, will eventually buffer as
 1783  * many packets as it is able and the only reason this typically works is
 1784  * due to the fairly small default buffers made available for a connection
 1785  * (typicaly 16K or 32K).  As machines use larger windows and/or window
 1786  * scaling it is now fairly easy for even a single TCP connection to blow-out
 1787  * all available buffer space not only on the local interface, but on
 1788  * intermediate routers and switches as well.  NewReno makes a misguided
 1789  * attempt to 'solve' this problem by waiting for an actual failure to occur,
 1790  * then backing off, then steadily increasing the window again until another
 1791  * failure occurs, ad-infinitum.  This results in terrible oscillation that
 1792  * is only made worse as network loads increase and the idea of intentionally
 1793  * blowing out network buffers is, frankly, a terrible way to manage network
 1794  * resources.
 1795  *
 1796  * It is far better to limit the transmit window prior to the failure
 1797  * condition being achieved.  There are two general ways to do this:  First
 1798  * you can 'scan' through different transmit window sizes and locate the
 1799  * point where the RTT stops increasing, indicating that you have filled the
 1800  * pipe, then scan backwards until you note that RTT stops decreasing, then
 1801  * repeat ad-infinitum.  This method works in principle but has severe
 1802  * implementation issues due to RTT variances, timer granularity, and
 1803  * instability in the algorithm which can lead to many false positives and
 1804  * create oscillations as well as interact badly with other TCP streams
 1805  * implementing the same algorithm.
 1806  *
 1807  * The second method is to limit the window to the bandwidth delay product
 1808  * of the link.  This is the method we implement.  RTT variances and our
 1809  * own manipulation of the congestion window, bwnd, can potentially
 1810  * destabilize the algorithm.  For this reason we have to stabilize the
 1811  * elements used to calculate the window.  We do this by using the minimum
 1812  * observed RTT, the long term average of the observed bandwidth, and
 1813  * by adding two segments worth of slop.  It isn't perfect but it is able
 1814  * to react to changing conditions and gives us a very stable basis on
 1815  * which to extend the algorithm.
 1816  */
 1817 void
 1818 tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq)
 1819 {
 1820         u_long bw;
 1821         u_long bwnd;
 1822         int save_ticks;
 1823 
 1824         INP_WLOCK_ASSERT(tp->t_inpcb);
 1825 
 1826         /*
 1827          * If inflight_enable is disabled in the middle of a tcp connection,
 1828          * make sure snd_bwnd is effectively disabled.
 1829          */
 1830         if (V_tcp_inflight_enable == 0 ||
 1831             tp->t_rttlow < V_tcp_inflight_rttthresh) {
 1832                 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 1833                 tp->snd_bandwidth = 0;
 1834                 return;
 1835         }
 1836 
 1837         /*
 1838          * Figure out the bandwidth.  Due to the tick granularity this
 1839          * is a very rough number and it MUST be averaged over a fairly
 1840          * long period of time.  XXX we need to take into account a link
 1841          * that is not using all available bandwidth, but for now our
 1842          * slop will ramp us up if this case occurs and the bandwidth later
 1843          * increases.
 1844          *
 1845          * Note: if ticks rollover 'bw' may wind up negative.  We must
 1846          * effectively reset t_bw_rtttime for this case.
 1847          */
 1848         save_ticks = ticks;
 1849         if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1)
 1850                 return;
 1851 
 1852         bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz /
 1853             (save_ticks - tp->t_bw_rtttime);
 1854         tp->t_bw_rtttime = save_ticks;
 1855         tp->t_bw_rtseq = ack_seq;
 1856         if (tp->t_bw_rtttime == 0 || (int)bw < 0)
 1857                 return;
 1858         bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4;
 1859 
 1860         tp->snd_bandwidth = bw;
 1861 
 1862         /*
 1863          * Calculate the semi-static bandwidth delay product, plus two maximal
 1864          * segments.  The additional slop puts us squarely in the sweet
 1865          * spot and also handles the bandwidth run-up case and stabilization.
 1866          * Without the slop we could be locking ourselves into a lower
 1867          * bandwidth.
 1868          *
 1869          * Situations Handled:
 1870          *      (1) Prevents over-queueing of packets on LANs, especially on
 1871          *          high speed LANs, allowing larger TCP buffers to be
 1872          *          specified, and also does a good job preventing
 1873          *          over-queueing of packets over choke points like modems
 1874          *          (at least for the transmit side).
 1875          *
 1876          *      (2) Is able to handle changing network loads (bandwidth
 1877          *          drops so bwnd drops, bandwidth increases so bwnd
 1878          *          increases).
 1879          *
 1880          *      (3) Theoretically should stabilize in the face of multiple
 1881          *          connections implementing the same algorithm (this may need
 1882          *          a little work).
 1883          *
 1884          *      (4) Stability value (defaults to 20 = 2 maximal packets) can
 1885          *          be adjusted with a sysctl but typically only needs to be
 1886          *          on very slow connections.  A value no smaller then 5
 1887          *          should be used, but only reduce this default if you have
 1888          *          no other choice.
 1889          */
 1890 #define USERTT  ((tp->t_srtt + tp->t_rttbest) / 2)
 1891         bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + V_tcp_inflight_stab * tp->t_maxseg / 10;
 1892 #undef USERTT
 1893 
 1894         if (tcp_inflight_debug > 0) {
 1895                 static int ltime;
 1896                 if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) {
 1897                         ltime = ticks;
 1898                         printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n",
 1899                             tp,
 1900                             bw,
 1901                             tp->t_rttbest,
 1902                             tp->t_srtt,
 1903                             bwnd
 1904                         );
 1905                 }
 1906         }
 1907         if ((long)bwnd < V_tcp_inflight_min)
 1908                 bwnd = V_tcp_inflight_min;
 1909         if (bwnd > V_tcp_inflight_max)
 1910                 bwnd = V_tcp_inflight_max;
 1911         if ((long)bwnd < tp->t_maxseg * 2)
 1912                 bwnd = tp->t_maxseg * 2;
 1913         tp->snd_bwnd = bwnd;
 1914 }
 1915 
 1916 #ifdef TCP_SIGNATURE
 1917 /*
 1918  * Callback function invoked by m_apply() to digest TCP segment data
 1919  * contained within an mbuf chain.
 1920  */
 1921 static int
 1922 tcp_signature_apply(void *fstate, void *data, u_int len)
 1923 {
 1924 
 1925         MD5Update(fstate, (u_char *)data, len);
 1926         return (0);
 1927 }
 1928 
 1929 /*
 1930  * Compute TCP-MD5 hash of a TCP segment. (RFC2385)
 1931  *
 1932  * Parameters:
 1933  * m            pointer to head of mbuf chain
 1934  * _unused      
 1935  * len          length of TCP segment data, excluding options
 1936  * optlen       length of TCP segment options
 1937  * buf          pointer to storage for computed MD5 digest
 1938  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 1939  *
 1940  * We do this over ip, tcphdr, segment data, and the key in the SADB.
 1941  * When called from tcp_input(), we can be sure that th_sum has been
 1942  * zeroed out and verified already.
 1943  *
 1944  * Return 0 if successful, otherwise return -1.
 1945  *
 1946  * XXX The key is retrieved from the system's PF_KEY SADB, by keying a
 1947  * search with the destination IP address, and a 'magic SPI' to be
 1948  * determined by the application. This is hardcoded elsewhere to 1179
 1949  * right now. Another branch of this code exists which uses the SPD to
 1950  * specify per-application flows but it is unstable.
 1951  */
 1952 int
 1953 tcp_signature_compute(struct mbuf *m, int _unused, int len, int optlen,
 1954     u_char *buf, u_int direction)
 1955 {
 1956         union sockaddr_union dst;
 1957         struct ippseudo ippseudo;
 1958         MD5_CTX ctx;
 1959         int doff;
 1960         struct ip *ip;
 1961         struct ipovly *ipovly;
 1962         struct secasvar *sav;
 1963         struct tcphdr *th;
 1964 #ifdef INET6
 1965         struct ip6_hdr *ip6;
 1966         struct in6_addr in6;
 1967         char ip6buf[INET6_ADDRSTRLEN];
 1968         uint32_t plen;
 1969         uint16_t nhdr;
 1970 #endif
 1971         u_short savecsum;
 1972 
 1973         KASSERT(m != NULL, ("NULL mbuf chain"));
 1974         KASSERT(buf != NULL, ("NULL signature pointer"));
 1975 
 1976         /* Extract the destination from the IP header in the mbuf. */
 1977         bzero(&dst, sizeof(union sockaddr_union));
 1978         ip = mtod(m, struct ip *);
 1979 #ifdef INET6
 1980         ip6 = NULL;     /* Make the compiler happy. */
 1981 #endif
 1982         switch (ip->ip_v) {
 1983         case IPVERSION:
 1984                 dst.sa.sa_len = sizeof(struct sockaddr_in);
 1985                 dst.sa.sa_family = AF_INET;
 1986                 dst.sin.sin_addr = (direction == IPSEC_DIR_INBOUND) ?
 1987                     ip->ip_src : ip->ip_dst;
 1988                 break;
 1989 #ifdef INET6
 1990         case (IPV6_VERSION >> 4):
 1991                 ip6 = mtod(m, struct ip6_hdr *);
 1992                 dst.sa.sa_len = sizeof(struct sockaddr_in6);
 1993                 dst.sa.sa_family = AF_INET6;
 1994                 dst.sin6.sin6_addr = (direction == IPSEC_DIR_INBOUND) ?
 1995                     ip6->ip6_src : ip6->ip6_dst;
 1996                 break;
 1997 #endif
 1998         default:
 1999                 return (EINVAL);
 2000                 /* NOTREACHED */
 2001                 break;
 2002         }
 2003 
 2004         /* Look up an SADB entry which matches the address of the peer. */
 2005         sav = KEY_ALLOCSA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI));
 2006         if (sav == NULL) {
 2007                 ipseclog((LOG_ERR, "%s: SADB lookup failed for %s\n", __func__,
 2008                     (ip->ip_v == IPVERSION) ? inet_ntoa(dst.sin.sin_addr) :
 2009 #ifdef INET6
 2010                         (ip->ip_v == (IPV6_VERSION >> 4)) ?
 2011                             ip6_sprintf(ip6buf, &dst.sin6.sin6_addr) :
 2012 #endif
 2013                         "(unsupported)"));
 2014                 return (EINVAL);
 2015         }
 2016 
 2017         MD5Init(&ctx);
 2018         /*
 2019          * Step 1: Update MD5 hash with IP(v6) pseudo-header.
 2020          *
 2021          * XXX The ippseudo header MUST be digested in network byte order,
 2022          * or else we'll fail the regression test. Assume all fields we've
 2023          * been doing arithmetic on have been in host byte order.
 2024          * XXX One cannot depend on ipovly->ih_len here. When called from
 2025          * tcp_output(), the underlying ip_len member has not yet been set.
 2026          */
 2027         switch (ip->ip_v) {
 2028         case IPVERSION:
 2029                 ipovly = (struct ipovly *)ip;
 2030                 ippseudo.ippseudo_src = ipovly->ih_src;
 2031                 ippseudo.ippseudo_dst = ipovly->ih_dst;
 2032                 ippseudo.ippseudo_pad = 0;
 2033                 ippseudo.ippseudo_p = IPPROTO_TCP;
 2034                 ippseudo.ippseudo_len = htons(len + sizeof(struct tcphdr) +
 2035                     optlen);
 2036                 MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo));
 2037 
 2038                 th = (struct tcphdr *)((u_char *)ip + sizeof(struct ip));
 2039                 doff = sizeof(struct ip) + sizeof(struct tcphdr) + optlen;
 2040                 break;
 2041 #ifdef INET6
 2042         /*
 2043          * RFC 2385, 2.0  Proposal
 2044          * For IPv6, the pseudo-header is as described in RFC 2460, namely the
 2045          * 128-bit source IPv6 address, 128-bit destination IPv6 address, zero-
 2046          * extended next header value (to form 32 bits), and 32-bit segment
 2047          * length.
 2048          * Note: Upper-Layer Packet Length comes before Next Header.
 2049          */
 2050         case (IPV6_VERSION >> 4):
 2051                 in6 = ip6->ip6_src;
 2052                 in6_clearscope(&in6);
 2053                 MD5Update(&ctx, (char *)&in6, sizeof(struct in6_addr));
 2054                 in6 = ip6->ip6_dst;
 2055                 in6_clearscope(&in6);
 2056                 MD5Update(&ctx, (char *)&in6, sizeof(struct in6_addr));
 2057                 plen = htonl(len + sizeof(struct tcphdr) + optlen);
 2058                 MD5Update(&ctx, (char *)&plen, sizeof(uint32_t));
 2059                 nhdr = 0;
 2060                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2061                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2062                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2063                 nhdr = IPPROTO_TCP;
 2064                 MD5Update(&ctx, (char *)&nhdr, sizeof(uint8_t));
 2065 
 2066                 th = (struct tcphdr *)((u_char *)ip6 + sizeof(struct ip6_hdr));
 2067                 doff = sizeof(struct ip6_hdr) + sizeof(struct tcphdr) + optlen;
 2068                 break;
 2069 #endif
 2070         default:
 2071                 return (EINVAL);
 2072                 /* NOTREACHED */
 2073                 break;
 2074         }
 2075 
 2076 
 2077         /*
 2078          * Step 2: Update MD5 hash with TCP header, excluding options.
 2079          * The TCP checksum must be set to zero.
 2080          */
 2081         savecsum = th->th_sum;
 2082         th->th_sum = 0;
 2083         MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
 2084         th->th_sum = savecsum;
 2085 
 2086         /*
 2087          * Step 3: Update MD5 hash with TCP segment data.
 2088          *         Use m_apply() to avoid an early m_pullup().
 2089          */
 2090         if (len > 0)
 2091                 m_apply(m, doff, len, tcp_signature_apply, &ctx);
 2092 
 2093         /*
 2094          * Step 4: Update MD5 hash with shared secret.
 2095          */
 2096         MD5Update(&ctx, sav->key_auth->key_data, _KEYLEN(sav->key_auth));
 2097         MD5Final(buf, &ctx);
 2098 
 2099         key_sa_recordxfer(sav, m);
 2100         KEY_FREESAV(&sav);
 2101         return (0);
 2102 }
 2103 #endif /* TCP_SIGNATURE */
 2104 
 2105 static int
 2106 sysctl_drop(SYSCTL_HANDLER_ARGS)
 2107 {
 2108         /* addrs[0] is a foreign socket, addrs[1] is a local one. */
 2109         struct sockaddr_storage addrs[2];
 2110         struct inpcb *inp;
 2111         struct tcpcb *tp;
 2112         struct tcptw *tw;
 2113         struct sockaddr_in *fin, *lin;
 2114 #ifdef INET6
 2115         struct sockaddr_in6 *fin6, *lin6;
 2116 #endif
 2117         int error;
 2118 
 2119         inp = NULL;
 2120         fin = lin = NULL;
 2121 #ifdef INET6
 2122         fin6 = lin6 = NULL;
 2123 #endif
 2124         error = 0;
 2125 
 2126         if (req->oldptr != NULL || req->oldlen != 0)
 2127                 return (EINVAL);
 2128         if (req->newptr == NULL)
 2129                 return (EPERM);
 2130         if (req->newlen < sizeof(addrs))
 2131                 return (ENOMEM);
 2132         error = SYSCTL_IN(req, &addrs, sizeof(addrs));
 2133         if (error)
 2134                 return (error);
 2135 
 2136         switch (addrs[0].ss_family) {
 2137 #ifdef INET6
 2138         case AF_INET6:
 2139                 fin6 = (struct sockaddr_in6 *)&addrs[0];
 2140                 lin6 = (struct sockaddr_in6 *)&addrs[1];
 2141                 if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
 2142                     lin6->sin6_len != sizeof(struct sockaddr_in6))
 2143                         return (EINVAL);
 2144                 if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
 2145                         if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
 2146                                 return (EINVAL);
 2147                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
 2148                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
 2149                         fin = (struct sockaddr_in *)&addrs[0];
 2150                         lin = (struct sockaddr_in *)&addrs[1];
 2151                         break;
 2152                 }
 2153                 error = sa6_embedscope(fin6, V_ip6_use_defzone);
 2154                 if (error)
 2155                         return (error);
 2156                 error = sa6_embedscope(lin6, V_ip6_use_defzone);
 2157                 if (error)
 2158                         return (error);
 2159                 break;
 2160 #endif
 2161         case AF_INET:
 2162                 fin = (struct sockaddr_in *)&addrs[0];
 2163                 lin = (struct sockaddr_in *)&addrs[1];
 2164                 if (fin->sin_len != sizeof(struct sockaddr_in) ||
 2165                     lin->sin_len != sizeof(struct sockaddr_in))
 2166                         return (EINVAL);
 2167                 break;
 2168         default:
 2169                 return (EINVAL);
 2170         }
 2171         INP_INFO_WLOCK(&V_tcbinfo);
 2172         switch (addrs[0].ss_family) {
 2173 #ifdef INET6
 2174         case AF_INET6:
 2175                 inp = in6_pcblookup_hash(&V_tcbinfo, &fin6->sin6_addr,
 2176                     fin6->sin6_port, &lin6->sin6_addr, lin6->sin6_port, 0,
 2177                     NULL);
 2178                 break;
 2179 #endif
 2180         case AF_INET:
 2181                 inp = in_pcblookup_hash(&V_tcbinfo, fin->sin_addr,
 2182                     fin->sin_port, lin->sin_addr, lin->sin_port, 0, NULL);
 2183                 break;
 2184         }
 2185         if (inp != NULL) {
 2186                 INP_WLOCK(inp);
 2187                 if (inp->inp_flags & INP_TIMEWAIT) {
 2188                         /*
 2189                          * XXXRW: There currently exists a state where an
 2190                          * inpcb is present, but its timewait state has been
 2191                          * discarded.  For now, don't allow dropping of this
 2192                          * type of inpcb.
 2193                          */
 2194                         tw = intotw(inp);
 2195                         if (tw != NULL)
 2196                                 tcp_twclose(tw, 0);
 2197                         else
 2198                                 INP_WUNLOCK(inp);
 2199                 } else if (!(inp->inp_flags & INP_DROPPED) &&
 2200                            !(inp->inp_socket->so_options & SO_ACCEPTCONN)) {
 2201                         tp = intotcpcb(inp);
 2202                         tp = tcp_drop(tp, ECONNABORTED);
 2203                         if (tp != NULL)
 2204                                 INP_WUNLOCK(inp);
 2205                 } else
 2206                         INP_WUNLOCK(inp);
 2207         } else
 2208                 error = ESRCH;
 2209         INP_INFO_WUNLOCK(&V_tcbinfo);
 2210         return (error);
 2211 }
 2212 
 2213 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
 2214     CTLTYPE_STRUCT|CTLFLAG_WR|CTLFLAG_SKIP, NULL,
 2215     0, sysctl_drop, "", "Drop TCP connection");
 2216 
 2217 /*
 2218  * Generate a standardized TCP log line for use throughout the
 2219  * tcp subsystem.  Memory allocation is done with M_NOWAIT to
 2220  * allow use in the interrupt context.
 2221  *
 2222  * NB: The caller MUST free(s, M_TCPLOG) the returned string.
 2223  * NB: The function may return NULL if memory allocation failed.
 2224  *
 2225  * Due to header inclusion and ordering limitations the struct ip
 2226  * and ip6_hdr pointers have to be passed as void pointers.
 2227  */
 2228 char *
 2229 tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 2230     const void *ip6hdr)
 2231 {
 2232         char *s, *sp;
 2233         size_t size;
 2234         struct ip *ip;
 2235 #ifdef INET6
 2236         const struct ip6_hdr *ip6;
 2237 
 2238         ip6 = (const struct ip6_hdr *)ip6hdr;
 2239 #endif /* INET6 */
 2240         ip = (struct ip *)ip4hdr;
 2241 
 2242         /*
 2243          * The log line looks like this:
 2244          * "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags 0x2<SYN>"
 2245          */
 2246         size = sizeof("TCP: []:12345 to []:12345 tcpflags 0x2<>") +
 2247             sizeof(PRINT_TH_FLAGS) + 1 +
 2248 #ifdef INET6
 2249             2 * INET6_ADDRSTRLEN;
 2250 #else
 2251             2 * INET_ADDRSTRLEN;
 2252 #endif /* INET6 */
 2253 
 2254         /* Is logging enabled? */
 2255         if (tcp_log_debug == 0 && tcp_log_in_vain == 0)
 2256                 return (NULL);
 2257 
 2258         s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
 2259         if (s == NULL)
 2260                 return (NULL);
 2261 
 2262         strcat(s, "TCP: [");
 2263         sp = s + strlen(s);
 2264 
 2265         if (inc && ((inc->inc_flags & INC_ISIPV6) == 0)) {
 2266                 inet_ntoa_r(inc->inc_faddr, sp);
 2267                 sp = s + strlen(s);
 2268                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2269                 sp = s + strlen(s);
 2270                 inet_ntoa_r(inc->inc_laddr, sp);
 2271                 sp = s + strlen(s);
 2272                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2273 #ifdef INET6
 2274         } else if (inc) {
 2275                 ip6_sprintf(sp, &inc->inc6_faddr);
 2276                 sp = s + strlen(s);
 2277                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2278                 sp = s + strlen(s);
 2279                 ip6_sprintf(sp, &inc->inc6_laddr);
 2280                 sp = s + strlen(s);
 2281                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2282         } else if (ip6 && th) {
 2283                 ip6_sprintf(sp, &ip6->ip6_src);
 2284                 sp = s + strlen(s);
 2285                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2286                 sp = s + strlen(s);
 2287                 ip6_sprintf(sp, &ip6->ip6_dst);
 2288                 sp = s + strlen(s);
 2289                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2290 #endif /* INET6 */
 2291         } else if (ip && th) {
 2292                 inet_ntoa_r(ip->ip_src, sp);
 2293                 sp = s + strlen(s);
 2294                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2295                 sp = s + strlen(s);
 2296                 inet_ntoa_r(ip->ip_dst, sp);
 2297                 sp = s + strlen(s);
 2298                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2299         } else {
 2300                 free(s, M_TCPLOG);
 2301                 return (NULL);
 2302         }
 2303         sp = s + strlen(s);
 2304         if (th)
 2305                 sprintf(sp, " tcpflags 0x%b", th->th_flags, PRINT_TH_FLAGS);
 2306         if (*(s + size - 1) != '\0')
 2307                 panic("%s: string too long", __func__);
 2308         return (s);
 2309 }

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