The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_subr.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)tcp_subr.c  8.2 (Berkeley) 5/24/95
   30  * $FreeBSD$
   31  */
   32 
   33 #include "opt_compat.h"
   34 #include "opt_inet.h"
   35 #include "opt_inet6.h"
   36 #include "opt_ipsec.h"
   37 #include "opt_mac.h"
   38 #include "opt_tcpdebug.h"
   39 #include "opt_tcp_sack.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/mac.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mbuf.h>
   49 #ifdef INET6
   50 #include <sys/domain.h>
   51 #endif
   52 #include <sys/proc.h>
   53 #include <sys/socket.h>
   54 #include <sys/socketvar.h>
   55 #include <sys/protosw.h>
   56 #include <sys/random.h>
   57 
   58 #include <vm/uma.h>
   59 
   60 #include <net/route.h>
   61 #include <net/if.h>
   62 
   63 #include <netinet/in.h>
   64 #include <netinet/in_systm.h>
   65 #include <netinet/ip.h>
   66 #ifdef INET6
   67 #include <netinet/ip6.h>
   68 #endif
   69 #include <netinet/in_pcb.h>
   70 #ifdef INET6
   71 #include <netinet6/in6_pcb.h>
   72 #endif
   73 #include <netinet/in_var.h>
   74 #include <netinet/ip_var.h>
   75 #ifdef INET6
   76 #include <netinet6/ip6_var.h>
   77 #include <netinet6/scope6_var.h>
   78 #include <netinet6/nd6.h>
   79 #endif
   80 #include <netinet/ip_icmp.h>
   81 #include <netinet/tcp.h>
   82 #include <netinet/tcp_fsm.h>
   83 #include <netinet/tcp_seq.h>
   84 #include <netinet/tcp_timer.h>
   85 #include <netinet/tcp_var.h>
   86 #ifdef INET6
   87 #include <netinet6/tcp6_var.h>
   88 #endif
   89 #include <netinet/tcpip.h>
   90 #ifdef TCPDEBUG
   91 #include <netinet/tcp_debug.h>
   92 #endif
   93 #include <netinet6/ip6protosw.h>
   94 
   95 #ifdef IPSEC
   96 #include <netinet6/ipsec.h>
   97 #ifdef INET6
   98 #include <netinet6/ipsec6.h>
   99 #endif
  100 #include <netkey/key.h>
  101 #endif /*IPSEC*/
  102 
  103 #ifdef FAST_IPSEC
  104 #include <netipsec/ipsec.h>
  105 #include <netipsec/xform.h>
  106 #ifdef INET6
  107 #include <netipsec/ipsec6.h>
  108 #endif
  109 #include <netipsec/key.h>
  110 #define IPSEC
  111 #endif /*FAST_IPSEC*/
  112 
  113 #include <machine/in_cksum.h>
  114 #include <sys/md5.h>
  115 
  116 int     tcp_mssdflt = TCP_MSS;
  117 SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt, CTLFLAG_RW,
  118     &tcp_mssdflt , 0, "Default TCP Maximum Segment Size");
  119 
  120 #ifdef INET6
  121 int     tcp_v6mssdflt = TCP6_MSS;
  122 SYSCTL_INT(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
  123         CTLFLAG_RW, &tcp_v6mssdflt , 0,
  124         "Default TCP Maximum Segment Size for IPv6");
  125 #endif
  126 
  127 /*
  128  * Minimum MSS we accept and use. This prevents DoS attacks where
  129  * we are forced to a ridiculous low MSS like 20 and send hundreds
  130  * of packets instead of one. The effect scales with the available
  131  * bandwidth and quickly saturates the CPU and network interface
  132  * with packet generation and sending. Set to zero to disable MINMSS
  133  * checking. This setting prevents us from sending too small packets.
  134  */
  135 int     tcp_minmss = TCP_MINMSS;
  136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_RW,
  137     &tcp_minmss , 0, "Minmum TCP Maximum Segment Size");
  138 /*
  139  * Number of TCP segments per second we accept from remote host
  140  * before we start to calculate average segment size. If average
  141  * segment size drops below the minimum TCP MSS we assume a DoS
  142  * attack and reset+drop the connection. Care has to be taken not to
  143  * set this value too small to not kill interactive type connections
  144  * (telnet, SSH) which send many small packets.
  145  */
  146 int     tcp_minmssoverload = TCP_MINMSSOVERLOAD;
  147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, minmssoverload, CTLFLAG_RW,
  148     &tcp_minmssoverload , 0, "Number of TCP Segments per Second allowed to"
  149     "be under the MINMSS Size");
  150 
  151 #if 0
  152 static int      tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
  153 SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt, CTLFLAG_RW,
  154     &tcp_rttdflt , 0, "Default maximum TCP Round Trip Time");
  155 #endif
  156 
  157 int     tcp_do_rfc1323 = 1;
  158 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
  159     &tcp_do_rfc1323 , 0, "Enable rfc1323 (high performance TCP) extensions");
  160 
  161 static int      tcp_tcbhashsize = 0;
  162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
  163      &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
  164 
  165 static int      do_tcpdrain = 1;
  166 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
  167      "Enable tcp_drain routine for extra help when low on mbufs");
  168 
  169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
  170     &tcbinfo.ipi_count, 0, "Number of active PCBs");
  171 
  172 static int      icmp_may_rst = 1;
  173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW, &icmp_may_rst, 0,
  174     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
  175 
  176 static int      tcp_isn_reseed_interval = 0;
  177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW,
  178     &tcp_isn_reseed_interval, 0, "Seconds between reseeding of ISN secret");
  179 
  180 static uma_zone_t tcptw_zone;
  181 static int      maxtcptw;
  182 
  183 static int
  184 tcptw_auto_size(void)
  185 {
  186         int halfrange;
  187 
  188         /*
  189          * Max out at half the ephemeral port range so that TIME_WAIT
  190          * sockets don't tie up too many ephemeral ports.
  191          */
  192         if (ipport_lastauto > ipport_firstauto)
  193                 halfrange = (ipport_lastauto - ipport_firstauto) / 2;
  194         else
  195                 halfrange = (ipport_firstauto - ipport_lastauto) / 2;
  196         /* Protect against goofy port ranges smaller than 32. */
  197         return (imin(imax(halfrange, 32), maxsockets / 5));
  198 }
  199 
  200 static int
  201 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
  202 {
  203         int error, new;
  204 
  205         if (maxtcptw == 0)
  206                 new = tcptw_auto_size();
  207         else
  208                 new = maxtcptw;
  209         error = sysctl_handle_int(oidp, &new, sizeof(int), req);
  210         if (error == 0 && req->newptr)
  211                 if (new >= 32) {
  212                         maxtcptw = new;
  213                         uma_zone_set_max(tcptw_zone, maxtcptw);
  214                 }
  215         return (error);
  216 }
  217 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
  218     &maxtcptw, 0, sysctl_maxtcptw, "IU",
  219     "Maximum number of compressed TCP TIME_WAIT entries");
  220 
  221 static int      nolocaltimewait = 0;
  222 SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
  223     &nolocaltimewait, 0, "Do not create compressed TCP TIME_WAIT entries"
  224                          "for local connections");
  225 
  226 /*
  227  * TCP bandwidth limiting sysctls.  Note that the default lower bound of
  228  * 1024 exists only for debugging.  A good production default would be
  229  * something like 6100.
  230  */
  231 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, inflight, CTLFLAG_RW, 0,
  232     "TCP inflight data limiting");
  233 
  234 static int      tcp_inflight_enable = 0;
  235 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, enable, CTLFLAG_RW,
  236     &tcp_inflight_enable, 0, "Enable automatic TCP inflight data limiting");
  237 
  238 static int      tcp_inflight_debug = 0;
  239 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, debug, CTLFLAG_RW,
  240     &tcp_inflight_debug, 0, "Debug TCP inflight calculations");
  241 
  242 static int      tcp_inflight_rttthresh;
  243 SYSCTL_PROC(_net_inet_tcp_inflight, OID_AUTO, rttthresh, CTLTYPE_INT|CTLFLAG_RW,
  244     &tcp_inflight_rttthresh, 0, sysctl_msec_to_ticks, "I",
  245     "RTT threshold below which inflight will deactivate itself");
  246 
  247 static int      tcp_inflight_min = 6144;
  248 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, min, CTLFLAG_RW,
  249     &tcp_inflight_min, 0, "Lower-bound for TCP inflight window");
  250 
  251 static int      tcp_inflight_max = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  252 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, max, CTLFLAG_RW,
  253     &tcp_inflight_max, 0, "Upper-bound for TCP inflight window");
  254 
  255 static int      tcp_inflight_stab = 20;
  256 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, stab, CTLFLAG_RW,
  257     &tcp_inflight_stab, 0, "Inflight Algorithm Stabilization 20 = 2 packets");
  258 
  259 uma_zone_t sack_hole_zone;
  260 
  261 static struct inpcb *tcp_notify(struct inpcb *, int);
  262 static void     tcp_discardcb(struct tcpcb *);
  263 static void     tcp_isn_tick(void *);
  264 
  265 /*
  266  * Target size of TCP PCB hash tables. Must be a power of two.
  267  *
  268  * Note that this can be overridden by the kernel environment
  269  * variable net.inet.tcp.tcbhashsize
  270  */
  271 #ifndef TCBHASHSIZE
  272 #define TCBHASHSIZE     512
  273 #endif
  274 
  275 /*
  276  * XXX
  277  * Callouts should be moved into struct tcp directly.  They are currently
  278  * separate because the tcpcb structure is exported to userland for sysctl
  279  * parsing purposes, which do not know about callouts.
  280  */
  281 struct  tcpcb_mem {
  282         struct  tcpcb tcb;
  283         struct  callout tcpcb_mem_rexmt, tcpcb_mem_persist, tcpcb_mem_keep;
  284         struct  callout tcpcb_mem_2msl, tcpcb_mem_delack;
  285 };
  286 
  287 static uma_zone_t tcpcb_zone;
  288 struct callout isn_callout;
  289 
  290 /*
  291  * Tcp initialization
  292  */
  293 static void
  294 tcp_zone_change(void *tag)
  295 {
  296 
  297         uma_zone_set_max(tcbinfo.ipi_zone, maxsockets);
  298         uma_zone_set_max(tcpcb_zone, maxsockets);
  299         if (maxtcptw == 0)
  300                 uma_zone_set_max(tcptw_zone, tcptw_auto_size());
  301 }
  302 
  303 static int
  304 tcp_inpcb_init(void *mem, int size, int flags)
  305 {
  306         struct inpcb *inp = mem;
  307 
  308         INP_LOCK_INIT(inp, "inp", "tcpinp");
  309         return (0);
  310 }
  311 
  312 void
  313 tcp_init()
  314 {
  315         int hashsize = TCBHASHSIZE;
  316 
  317         tcp_delacktime = TCPTV_DELACK;
  318         tcp_keepinit = TCPTV_KEEP_INIT;
  319         tcp_keepidle = TCPTV_KEEP_IDLE;
  320         tcp_keepintvl = TCPTV_KEEPINTVL;
  321         tcp_maxpersistidle = TCPTV_KEEP_IDLE;
  322         tcp_msl = TCPTV_MSL;
  323         tcp_rexmit_min = TCPTV_MIN;
  324         if (tcp_rexmit_min < 1)
  325                 tcp_rexmit_min = 1;
  326         tcp_rexmit_slop = TCPTV_CPU_VAR;
  327         tcp_inflight_rttthresh = TCPTV_INFLIGHT_RTTTHRESH;
  328 
  329         INP_INFO_LOCK_INIT(&tcbinfo, "tcp");
  330         LIST_INIT(&tcb);
  331         tcbinfo.listhead = &tcb;
  332         TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize);
  333         if (!powerof2(hashsize)) {
  334                 printf("WARNING: TCB hash size not a power of 2\n");
  335                 hashsize = 512; /* safe default */
  336         }
  337         tcp_tcbhashsize = hashsize;
  338         tcbinfo.hashbase = hashinit(hashsize, M_PCB, &tcbinfo.hashmask);
  339         tcbinfo.porthashbase = hashinit(hashsize, M_PCB,
  340                                         &tcbinfo.porthashmask);
  341         tcbinfo.ipi_zone = uma_zcreate("inpcb", sizeof(struct inpcb),
  342             NULL, NULL, tcp_inpcb_init, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  343         uma_zone_set_max(tcbinfo.ipi_zone, maxsockets);
  344 #ifdef INET6
  345 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
  346 #else /* INET6 */
  347 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
  348 #endif /* INET6 */
  349         if (max_protohdr < TCP_MINPROTOHDR)
  350                 max_protohdr = TCP_MINPROTOHDR;
  351         if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
  352                 panic("tcp_init");
  353 #undef TCP_MINPROTOHDR
  354         /*
  355          * These have to be type stable for the benefit of the timers.
  356          */
  357         tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
  358             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  359         uma_zone_set_max(tcpcb_zone, maxsockets);
  360         tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
  361             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  362         TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
  363         if (maxtcptw == 0)
  364                 uma_zone_set_max(tcptw_zone, tcptw_auto_size());
  365         else
  366                 uma_zone_set_max(tcptw_zone, maxtcptw);
  367         tcp_timer_init();
  368         syncache_init();
  369         tcp_hc_init();
  370         tcp_reass_init();
  371         callout_init(&isn_callout, CALLOUT_MPSAFE);
  372         tcp_isn_tick(NULL);
  373         EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
  374                 SHUTDOWN_PRI_DEFAULT);
  375         sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
  376             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  377         EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
  378                 EVENTHANDLER_PRI_ANY);
  379 }
  380 
  381 void
  382 tcp_fini(xtp)
  383         void *xtp;
  384 {
  385         callout_stop(&isn_callout);
  386 
  387 }
  388 
  389 /*
  390  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
  391  * tcp_template used to store this data in mbufs, but we now recopy it out
  392  * of the tcpcb each time to conserve mbufs.
  393  */
  394 void
  395 tcpip_fillheaders(inp, ip_ptr, tcp_ptr)
  396         struct inpcb *inp;
  397         void *ip_ptr;
  398         void *tcp_ptr;
  399 {
  400         struct tcphdr *th = (struct tcphdr *)tcp_ptr;
  401 
  402         INP_LOCK_ASSERT(inp);
  403 
  404 #ifdef INET6
  405         if ((inp->inp_vflag & INP_IPV6) != 0) {
  406                 struct ip6_hdr *ip6;
  407 
  408                 ip6 = (struct ip6_hdr *)ip_ptr;
  409                 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
  410                         (inp->in6p_flowinfo & IPV6_FLOWINFO_MASK);
  411                 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
  412                         (IPV6_VERSION & IPV6_VERSION_MASK);
  413                 ip6->ip6_nxt = IPPROTO_TCP;
  414                 ip6->ip6_plen = sizeof(struct tcphdr);
  415                 ip6->ip6_src = inp->in6p_laddr;
  416                 ip6->ip6_dst = inp->in6p_faddr;
  417         } else
  418 #endif
  419         {
  420                 struct ip *ip;
  421 
  422                 ip = (struct ip *)ip_ptr;
  423                 ip->ip_v = IPVERSION;
  424                 ip->ip_hl = 5;
  425                 ip->ip_tos = inp->inp_ip_tos;
  426                 ip->ip_len = 0;
  427                 ip->ip_id = 0;
  428                 ip->ip_off = 0;
  429                 ip->ip_ttl = inp->inp_ip_ttl;
  430                 ip->ip_sum = 0;
  431                 ip->ip_p = IPPROTO_TCP;
  432                 ip->ip_src = inp->inp_laddr;
  433                 ip->ip_dst = inp->inp_faddr;
  434         }
  435         th->th_sport = inp->inp_lport;
  436         th->th_dport = inp->inp_fport;
  437         th->th_seq = 0;
  438         th->th_ack = 0;
  439         th->th_x2 = 0;
  440         th->th_off = 5;
  441         th->th_flags = 0;
  442         th->th_win = 0;
  443         th->th_urp = 0;
  444         th->th_sum = 0;         /* in_pseudo() is called later for ipv4 */
  445 }
  446 
  447 /*
  448  * Create template to be used to send tcp packets on a connection.
  449  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
  450  * use for this function is in keepalives, which use tcp_respond.
  451  */
  452 struct tcptemp *
  453 tcpip_maketemplate(inp)
  454         struct inpcb *inp;
  455 {
  456         struct mbuf *m;
  457         struct tcptemp *n;
  458 
  459         m = m_get(M_DONTWAIT, MT_DATA);
  460         if (m == NULL)
  461                 return (0);
  462         m->m_len = sizeof(struct tcptemp);
  463         n = mtod(m, struct tcptemp *);
  464 
  465         tcpip_fillheaders(inp, (void *)&n->tt_ipgen, (void *)&n->tt_t);
  466         return (n);
  467 }
  468 
  469 /*
  470  * Send a single message to the TCP at address specified by
  471  * the given TCP/IP header.  If m == NULL, then we make a copy
  472  * of the tcpiphdr at ti and send directly to the addressed host.
  473  * This is used to force keep alive messages out using the TCP
  474  * template for a connection.  If flags are given then we send
  475  * a message back to the TCP which originated the * segment ti,
  476  * and discard the mbuf containing it and any other attached mbufs.
  477  *
  478  * In any case the ack and sequence number of the transmitted
  479  * segment are as specified by the parameters.
  480  *
  481  * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
  482  */
  483 void
  484 tcp_respond(tp, ipgen, th, m, ack, seq, flags)
  485         struct tcpcb *tp;
  486         void *ipgen;
  487         register struct tcphdr *th;
  488         register struct mbuf *m;
  489         tcp_seq ack, seq;
  490         int flags;
  491 {
  492         register int tlen;
  493         int win = 0;
  494         struct ip *ip;
  495         struct tcphdr *nth;
  496 #ifdef INET6
  497         struct ip6_hdr *ip6;
  498         int isipv6;
  499 #endif /* INET6 */
  500         int ipflags = 0;
  501         struct inpcb *inp;
  502 
  503         KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
  504 
  505 #ifdef INET6
  506         isipv6 = ((struct ip *)ipgen)->ip_v == 6;
  507         ip6 = ipgen;
  508 #endif /* INET6 */
  509         ip = ipgen;
  510 
  511         if (tp != NULL) {
  512                 inp = tp->t_inpcb;
  513                 KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
  514                 INP_INFO_WLOCK_ASSERT(&tcbinfo);
  515                 INP_LOCK_ASSERT(inp);
  516         } else
  517                 inp = NULL;
  518 
  519         if (tp != NULL) {
  520                 if (!(flags & TH_RST)) {
  521                         win = sbspace(&inp->inp_socket->so_rcv);
  522                         if (win > (long)TCP_MAXWIN << tp->rcv_scale)
  523                                 win = (long)TCP_MAXWIN << tp->rcv_scale;
  524                 }
  525         }
  526         if (m == NULL) {
  527                 m = m_gethdr(M_DONTWAIT, MT_HEADER);
  528                 if (m == NULL)
  529                         return;
  530                 tlen = 0;
  531                 m->m_data += max_linkhdr;
  532 #ifdef INET6
  533                 if (isipv6) {
  534                         bcopy((caddr_t)ip6, mtod(m, caddr_t),
  535                               sizeof(struct ip6_hdr));
  536                         ip6 = mtod(m, struct ip6_hdr *);
  537                         nth = (struct tcphdr *)(ip6 + 1);
  538                 } else
  539 #endif /* INET6 */
  540               {
  541                 bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
  542                 ip = mtod(m, struct ip *);
  543                 nth = (struct tcphdr *)(ip + 1);
  544               }
  545                 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
  546                 flags = TH_ACK;
  547         } else {
  548                 m_freem(m->m_next);
  549                 m->m_next = NULL;
  550                 m->m_data = (caddr_t)ipgen;
  551                 /* m_len is set later */
  552                 tlen = 0;
  553 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
  554 #ifdef INET6
  555                 if (isipv6) {
  556                         xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
  557                         nth = (struct tcphdr *)(ip6 + 1);
  558                 } else
  559 #endif /* INET6 */
  560               {
  561                 xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long);
  562                 nth = (struct tcphdr *)(ip + 1);
  563               }
  564                 if (th != nth) {
  565                         /*
  566                          * this is usually a case when an extension header
  567                          * exists between the IPv6 header and the
  568                          * TCP header.
  569                          */
  570                         nth->th_sport = th->th_sport;
  571                         nth->th_dport = th->th_dport;
  572                 }
  573                 xchg(nth->th_dport, nth->th_sport, n_short);
  574 #undef xchg
  575         }
  576 #ifdef INET6
  577         if (isipv6) {
  578                 ip6->ip6_flow = 0;
  579                 ip6->ip6_vfc = IPV6_VERSION;
  580                 ip6->ip6_nxt = IPPROTO_TCP;
  581                 ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) +
  582                                                 tlen));
  583                 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
  584         } else
  585 #endif
  586         {
  587                 tlen += sizeof (struct tcpiphdr);
  588                 ip->ip_len = tlen;
  589                 ip->ip_ttl = ip_defttl;
  590                 if (path_mtu_discovery)
  591                         ip->ip_off |= IP_DF;
  592         }
  593         m->m_len = tlen;
  594         m->m_pkthdr.len = tlen;
  595         m->m_pkthdr.rcvif = NULL;
  596 #ifdef MAC
  597         if (inp != NULL) {
  598                 /*
  599                  * Packet is associated with a socket, so allow the
  600                  * label of the response to reflect the socket label.
  601                  */
  602                 INP_LOCK_ASSERT(inp);
  603                 mac_create_mbuf_from_inpcb(inp, m);
  604         } else {
  605                 /*
  606                  * Packet is not associated with a socket, so possibly
  607                  * update the label in place.
  608                  */
  609                 mac_reflect_mbuf_tcp(m);
  610         }
  611 #endif
  612         nth->th_seq = htonl(seq);
  613         nth->th_ack = htonl(ack);
  614         nth->th_x2 = 0;
  615         nth->th_off = sizeof (struct tcphdr) >> 2;
  616         nth->th_flags = flags;
  617         if (tp != NULL)
  618                 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
  619         else
  620                 nth->th_win = htons((u_short)win);
  621         nth->th_urp = 0;
  622 #ifdef INET6
  623         if (isipv6) {
  624                 nth->th_sum = 0;
  625                 nth->th_sum = in6_cksum(m, IPPROTO_TCP,
  626                                         sizeof(struct ip6_hdr),
  627                                         tlen - sizeof(struct ip6_hdr));
  628                 ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
  629                     NULL, NULL);
  630         } else
  631 #endif /* INET6 */
  632         {
  633                 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
  634                     htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
  635                 m->m_pkthdr.csum_flags = CSUM_TCP;
  636                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
  637         }
  638 #ifdef TCPDEBUG
  639         if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
  640                 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
  641 #endif
  642 #ifdef INET6
  643         if (isipv6)
  644                 (void) ip6_output(m, NULL, NULL, ipflags, NULL, NULL, inp);
  645         else
  646 #endif /* INET6 */
  647         (void) ip_output(m, NULL, NULL, ipflags, NULL, inp);
  648 }
  649 
  650 /*
  651  * Create a new TCP control block, making an
  652  * empty reassembly queue and hooking it to the argument
  653  * protocol control block.  The `inp' parameter must have
  654  * come from the zone allocator set up in tcp_init().
  655  */
  656 struct tcpcb *
  657 tcp_newtcpcb(inp)
  658         struct inpcb *inp;
  659 {
  660         struct tcpcb_mem *tm;
  661         struct tcpcb *tp;
  662 #ifdef INET6
  663         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  664 #endif /* INET6 */
  665 
  666         tm = uma_zalloc(tcpcb_zone, M_NOWAIT | M_ZERO);
  667         if (tm == NULL)
  668                 return (NULL);
  669         tp = &tm->tcb;
  670         /*      LIST_INIT(&tp->t_segq); */      /* XXX covered by M_ZERO */
  671         tp->t_maxseg = tp->t_maxopd =
  672 #ifdef INET6
  673                 isipv6 ? tcp_v6mssdflt :
  674 #endif /* INET6 */
  675                 tcp_mssdflt;
  676 
  677         /* Set up our timeouts. */
  678         callout_init(tp->tt_rexmt = &tm->tcpcb_mem_rexmt, NET_CALLOUT_MPSAFE);
  679         callout_init(tp->tt_persist = &tm->tcpcb_mem_persist, NET_CALLOUT_MPSAFE);
  680         callout_init(tp->tt_keep = &tm->tcpcb_mem_keep, NET_CALLOUT_MPSAFE);
  681         callout_init(tp->tt_2msl = &tm->tcpcb_mem_2msl, NET_CALLOUT_MPSAFE);
  682         callout_init(tp->tt_delack = &tm->tcpcb_mem_delack, NET_CALLOUT_MPSAFE);
  683 
  684         if (tcp_do_rfc1323)
  685                 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
  686         tp->sack_enable = tcp_do_sack;
  687         TAILQ_INIT(&tp->snd_holes);
  688         tp->t_inpcb = inp;      /* XXX */
  689         /*
  690          * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
  691          * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
  692          * reasonable initial retransmit time.
  693          */
  694         tp->t_srtt = TCPTV_SRTTBASE;
  695         tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
  696         tp->t_rttmin = tcp_rexmit_min;
  697         tp->t_rxtcur = TCPTV_RTOBASE;
  698         tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  699         tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  700         tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  701         tp->t_rcvtime = ticks;
  702         tp->t_bw_rtttime = ticks;
  703         /*
  704          * IPv4 TTL initialization is necessary for an IPv6 socket as well,
  705          * because the socket may be bound to an IPv6 wildcard address,
  706          * which may match an IPv4-mapped IPv6 address.
  707          */
  708         inp->inp_ip_ttl = ip_defttl;
  709         inp->inp_ppcb = (caddr_t)tp;
  710         return (tp);            /* XXX */
  711 }
  712 
  713 /*
  714  * Drop a TCP connection, reporting
  715  * the specified error.  If connection is synchronized,
  716  * then send a RST to peer.
  717  */
  718 struct tcpcb *
  719 tcp_drop(tp, errno)
  720         register struct tcpcb *tp;
  721         int errno;
  722 {
  723         struct socket *so = tp->t_inpcb->inp_socket;
  724 
  725         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  726         INP_LOCK_ASSERT(tp->t_inpcb);
  727 
  728         if (TCPS_HAVERCVDSYN(tp->t_state)) {
  729                 tp->t_state = TCPS_CLOSED;
  730                 (void) tcp_output(tp);
  731                 tcpstat.tcps_drops++;
  732         } else
  733                 tcpstat.tcps_conndrops++;
  734         if (errno == ETIMEDOUT && tp->t_softerror)
  735                 errno = tp->t_softerror;
  736         so->so_error = errno;
  737         return (tcp_close(tp));
  738 }
  739 
  740 static void
  741 tcp_discardcb(tp)
  742         struct tcpcb *tp;
  743 {
  744         struct tseg_qent *q;
  745         struct inpcb *inp = tp->t_inpcb;
  746         struct socket *so = inp->inp_socket;
  747 #ifdef INET6
  748         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  749 #endif /* INET6 */
  750 
  751         INP_LOCK_ASSERT(inp);
  752 
  753         /*
  754          * Make sure that all of our timers are stopped before we
  755          * delete the PCB.
  756          */
  757         callout_stop(tp->tt_rexmt);
  758         callout_stop(tp->tt_persist);
  759         callout_stop(tp->tt_keep);
  760         callout_stop(tp->tt_2msl);
  761         callout_stop(tp->tt_delack);
  762 
  763         /*
  764          * If we got enough samples through the srtt filter,
  765          * save the rtt and rttvar in the routing entry.
  766          * 'Enough' is arbitrarily defined as 4 rtt samples.
  767          * 4 samples is enough for the srtt filter to converge
  768          * to within enough % of the correct value; fewer samples
  769          * and we could save a bogus rtt. The danger is not high
  770          * as tcp quickly recovers from everything.
  771          * XXX: Works very well but needs some more statistics!
  772          */
  773         if (tp->t_rttupdated >= 4) {
  774                 struct hc_metrics_lite metrics;
  775                 u_long ssthresh;
  776 
  777                 bzero(&metrics, sizeof(metrics));
  778                 /*
  779                  * Update the ssthresh always when the conditions below
  780                  * are satisfied. This gives us better new start value
  781                  * for the congestion avoidance for new connections.
  782                  * ssthresh is only set if packet loss occured on a session.
  783                  */
  784                 ssthresh = tp->snd_ssthresh;
  785                 if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
  786                         /*
  787                          * convert the limit from user data bytes to
  788                          * packets then to packet data bytes.
  789                          */
  790                         ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
  791                         if (ssthresh < 2)
  792                                 ssthresh = 2;
  793                         ssthresh *= (u_long)(tp->t_maxseg +
  794 #ifdef INET6
  795                                       (isipv6 ? sizeof (struct ip6_hdr) +
  796                                                sizeof (struct tcphdr) :
  797 #endif
  798                                        sizeof (struct tcpiphdr)
  799 #ifdef INET6
  800                                        )
  801 #endif
  802                                       );
  803                 } else
  804                         ssthresh = 0;
  805                 metrics.rmx_ssthresh = ssthresh;
  806 
  807                 metrics.rmx_rtt = tp->t_srtt;
  808                 metrics.rmx_rttvar = tp->t_rttvar;
  809                 /* XXX: This wraps if the pipe is more than 4 Gbit per second */
  810                 metrics.rmx_bandwidth = tp->snd_bandwidth;
  811                 metrics.rmx_cwnd = tp->snd_cwnd;
  812                 metrics.rmx_sendpipe = 0;
  813                 metrics.rmx_recvpipe = 0;
  814 
  815                 tcp_hc_update(&inp->inp_inc, &metrics);
  816         }
  817 
  818         /* free the reassembly queue, if any */
  819         while ((q = LIST_FIRST(&tp->t_segq)) != NULL) {
  820                 LIST_REMOVE(q, tqe_q);
  821                 m_freem(q->tqe_m);
  822                 uma_zfree(tcp_reass_zone, q);
  823                 tp->t_segqlen--;
  824                 tcp_reass_qsize--;
  825         }
  826         tcp_free_sackholes(tp);
  827         inp->inp_ppcb = NULL;
  828         tp->t_inpcb = NULL;
  829         uma_zfree(tcpcb_zone, tp);
  830         soisdisconnected(so);
  831 }
  832 
  833 /*
  834  * Close a TCP control block:
  835  *    discard all space held by the tcp
  836  *    discard internet protocol block
  837  *    wake up any sleepers
  838  */
  839 struct tcpcb *
  840 tcp_close(tp)
  841         struct tcpcb *tp;
  842 {
  843         struct inpcb *inp = tp->t_inpcb;
  844 #ifdef INET6
  845         struct socket *so = inp->inp_socket;
  846 #endif
  847 
  848         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  849         INP_LOCK_ASSERT(inp);
  850 
  851         tcp_discardcb(tp);
  852 #ifdef INET6
  853         if (INP_CHECK_SOCKAF(so, AF_INET6))
  854                 in6_pcbdetach(inp);
  855         else
  856 #endif
  857                 in_pcbdetach(inp);
  858         tcpstat.tcps_closed++;
  859         return (NULL);
  860 }
  861 
  862 void
  863 tcp_drain()
  864 {
  865         if (do_tcpdrain)
  866         {
  867                 struct inpcb *inpb;
  868                 struct tcpcb *tcpb;
  869                 struct tseg_qent *te;
  870 
  871         /*
  872          * Walk the tcpbs, if existing, and flush the reassembly queue,
  873          * if there is one...
  874          * XXX: The "Net/3" implementation doesn't imply that the TCP
  875          *      reassembly queue should be flushed, but in a situation
  876          *      where we're really low on mbufs, this is potentially
  877          *      usefull.
  878          */
  879                 INP_INFO_RLOCK(&tcbinfo);
  880                 LIST_FOREACH(inpb, tcbinfo.listhead, inp_list) {
  881                         if (inpb->inp_vflag & INP_TIMEWAIT)
  882                                 continue;
  883                         INP_LOCK(inpb);
  884                         if ((tcpb = intotcpcb(inpb)) != NULL) {
  885                                 while ((te = LIST_FIRST(&tcpb->t_segq))
  886                                     != NULL) {
  887                                         LIST_REMOVE(te, tqe_q);
  888                                         m_freem(te->tqe_m);
  889                                         uma_zfree(tcp_reass_zone, te);
  890                                         tcpb->t_segqlen--;
  891                                         tcp_reass_qsize--;
  892                                 }
  893                                 tcp_clean_sackreport(tcpb);
  894                         }
  895                         INP_UNLOCK(inpb);
  896                 }
  897                 INP_INFO_RUNLOCK(&tcbinfo);
  898         }
  899 }
  900 
  901 /*
  902  * Notify a tcp user of an asynchronous error;
  903  * store error as soft error, but wake up user
  904  * (for now, won't do anything until can select for soft error).
  905  *
  906  * Do not wake up user since there currently is no mechanism for
  907  * reporting soft errors (yet - a kqueue filter may be added).
  908  */
  909 static struct inpcb *
  910 tcp_notify(inp, error)
  911         struct inpcb *inp;
  912         int error;
  913 {
  914         struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb;
  915 
  916         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  917         INP_LOCK_ASSERT(inp);
  918 
  919         /*
  920          * Ignore some errors if we are hooked up.
  921          * If connection hasn't completed, has retransmitted several times,
  922          * and receives a second error, give up now.  This is better
  923          * than waiting a long time to establish a connection that
  924          * can never complete.
  925          */
  926         if (tp->t_state == TCPS_ESTABLISHED &&
  927             (error == EHOSTUNREACH || error == ENETUNREACH ||
  928              error == EHOSTDOWN)) {
  929                 return (inp);
  930         } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
  931             tp->t_softerror) {
  932                 tcp_drop(tp, error);
  933                 return (struct inpcb *)0;
  934         } else {
  935                 tp->t_softerror = error;
  936                 return (inp);
  937         }
  938 #if 0
  939         wakeup( &so->so_timeo);
  940         sorwakeup(so);
  941         sowwakeup(so);
  942 #endif
  943 }
  944 
  945 static int
  946 tcp_pcblist(SYSCTL_HANDLER_ARGS)
  947 {
  948         int error, i, n;
  949         struct inpcb *inp, **inp_list;
  950         inp_gen_t gencnt;
  951         struct xinpgen xig;
  952 
  953         /*
  954          * The process of preparing the TCB list is too time-consuming and
  955          * resource-intensive to repeat twice on every request.
  956          */
  957         if (req->oldptr == NULL) {
  958                 n = tcbinfo.ipi_count;
  959                 req->oldidx = 2 * (sizeof xig)
  960                         + (n + n/8) * sizeof(struct xtcpcb);
  961                 return (0);
  962         }
  963 
  964         if (req->newptr != NULL)
  965                 return (EPERM);
  966 
  967         /*
  968          * OK, now we're committed to doing something.
  969          */
  970         INP_INFO_RLOCK(&tcbinfo);
  971         gencnt = tcbinfo.ipi_gencnt;
  972         n = tcbinfo.ipi_count;
  973         INP_INFO_RUNLOCK(&tcbinfo);
  974 
  975         error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
  976                 + n * sizeof(struct xtcpcb));
  977         if (error != 0)
  978                 return (error);
  979 
  980         xig.xig_len = sizeof xig;
  981         xig.xig_count = n;
  982         xig.xig_gen = gencnt;
  983         xig.xig_sogen = so_gencnt;
  984         error = SYSCTL_OUT(req, &xig, sizeof xig);
  985         if (error)
  986                 return (error);
  987 
  988         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
  989         if (inp_list == NULL)
  990                 return (ENOMEM);
  991 
  992         INP_INFO_RLOCK(&tcbinfo);
  993         for (inp = LIST_FIRST(tcbinfo.listhead), i = 0; inp != NULL && i < n;
  994              inp = LIST_NEXT(inp, inp_list)) {
  995                 INP_LOCK(inp);
  996                 if (inp->inp_gencnt <= gencnt) {
  997                         /*
  998                          * XXX: This use of cr_cansee(), introduced with
  999                          * TCP state changes, is not quite right, but for
 1000                          * now, better than nothing.
 1001                          */
 1002                         if (inp->inp_vflag & INP_TIMEWAIT)
 1003                                 error = cr_cansee(req->td->td_ucred,
 1004                                     intotw(inp)->tw_cred);
 1005                         else
 1006                                 error = cr_canseesocket(req->td->td_ucred,
 1007                                     inp->inp_socket);
 1008                         if (error == 0)
 1009                                 inp_list[i++] = inp;
 1010                 }
 1011                 INP_UNLOCK(inp);
 1012         }
 1013         INP_INFO_RUNLOCK(&tcbinfo);
 1014         n = i;
 1015 
 1016         error = 0;
 1017         for (i = 0; i < n; i++) {
 1018                 inp = inp_list[i];
 1019                 INP_LOCK(inp);
 1020                 if (inp->inp_gencnt <= gencnt) {
 1021                         struct xtcpcb xt;
 1022                         caddr_t inp_ppcb;
 1023 
 1024                         bzero(&xt, sizeof(xt));
 1025                         xt.xt_len = sizeof xt;
 1026                         /* XXX should avoid extra copy */
 1027                         bcopy(inp, &xt.xt_inp, sizeof *inp);
 1028                         inp_ppcb = inp->inp_ppcb;
 1029                         if (inp_ppcb == NULL)
 1030                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1031                         else if (inp->inp_vflag & INP_TIMEWAIT) {
 1032                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
 1033                                 xt.xt_tp.t_state = TCPS_TIME_WAIT;
 1034                         } else
 1035                                 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
 1036                         if (inp->inp_socket != NULL)
 1037                                 sotoxsocket(inp->inp_socket, &xt.xt_socket);
 1038                         else {
 1039                                 bzero(&xt.xt_socket, sizeof xt.xt_socket);
 1040                                 xt.xt_socket.xso_protocol = IPPROTO_TCP;
 1041                         }
 1042                         xt.xt_inp.inp_gencnt = inp->inp_gencnt;
 1043                         INP_UNLOCK(inp);
 1044                         error = SYSCTL_OUT(req, &xt, sizeof xt);
 1045                 } else
 1046                         INP_UNLOCK(inp);
 1047         
 1048         }
 1049         if (!error) {
 1050                 /*
 1051                  * Give the user an updated idea of our state.
 1052                  * If the generation differs from what we told
 1053                  * her before, she knows that something happened
 1054                  * while we were processing this request, and it
 1055                  * might be necessary to retry.
 1056                  */
 1057                 INP_INFO_RLOCK(&tcbinfo);
 1058                 xig.xig_gen = tcbinfo.ipi_gencnt;
 1059                 xig.xig_sogen = so_gencnt;
 1060                 xig.xig_count = tcbinfo.ipi_count;
 1061                 INP_INFO_RUNLOCK(&tcbinfo);
 1062                 error = SYSCTL_OUT(req, &xig, sizeof xig);
 1063         }
 1064         free(inp_list, M_TEMP);
 1065         return (error);
 1066 }
 1067 
 1068 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
 1069             tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
 1070 
 1071 static int
 1072 tcp_getcred(SYSCTL_HANDLER_ARGS)
 1073 {
 1074         struct xucred xuc;
 1075         struct sockaddr_in addrs[2];
 1076         struct inpcb *inp;
 1077         int error;
 1078 
 1079         error = suser_cred(req->td->td_ucred, SUSER_ALLOWJAIL);
 1080         if (error)
 1081                 return (error);
 1082         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1083         if (error)
 1084                 return (error);
 1085         INP_INFO_RLOCK(&tcbinfo);
 1086         inp = in_pcblookup_hash(&tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
 1087             addrs[0].sin_addr, addrs[0].sin_port, 0, NULL);
 1088         if (inp == NULL) {
 1089                 error = ENOENT;
 1090                 goto outunlocked;
 1091         }
 1092         INP_LOCK(inp);
 1093         if (inp->inp_socket == NULL) {
 1094                 error = ENOENT;
 1095                 goto out;
 1096         }
 1097         error = cr_canseesocket(req->td->td_ucred, inp->inp_socket);
 1098         if (error)
 1099                 goto out;
 1100         cru2x(inp->inp_socket->so_cred, &xuc);
 1101 out:
 1102         INP_UNLOCK(inp);
 1103 outunlocked:
 1104         INP_INFO_RUNLOCK(&tcbinfo);
 1105         if (error == 0)
 1106                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1107         return (error);
 1108 }
 1109 
 1110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
 1111     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1112     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
 1113 
 1114 #ifdef INET6
 1115 static int
 1116 tcp6_getcred(SYSCTL_HANDLER_ARGS)
 1117 {
 1118         struct xucred xuc;
 1119         struct sockaddr_in6 addrs[2];
 1120         struct inpcb *inp;
 1121         int error, mapped = 0;
 1122 
 1123         error = suser_cred(req->td->td_ucred, SUSER_ALLOWJAIL);
 1124         if (error)
 1125                 return (error);
 1126         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1127         if (error)
 1128                 return (error);
 1129         if ((error = sa6_embedscope(&addrs[0], ip6_use_defzone)) != 0 ||
 1130             (error = sa6_embedscope(&addrs[1], ip6_use_defzone)) != 0) {
 1131                 return (error);
 1132         }
 1133         if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
 1134                 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
 1135                         mapped = 1;
 1136                 else
 1137                         return (EINVAL);
 1138         }
 1139 
 1140         INP_INFO_RLOCK(&tcbinfo);
 1141         if (mapped == 1)
 1142                 inp = in_pcblookup_hash(&tcbinfo,
 1143                         *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
 1144                         addrs[1].sin6_port,
 1145                         *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
 1146                         addrs[0].sin6_port,
 1147                         0, NULL);
 1148         else
 1149                 inp = in6_pcblookup_hash(&tcbinfo,
 1150                         &addrs[1].sin6_addr, addrs[1].sin6_port,
 1151                         &addrs[0].sin6_addr, addrs[0].sin6_port, 0, NULL);
 1152         if (inp == NULL) {
 1153                 error = ENOENT;
 1154                 goto outunlocked;
 1155         }
 1156         INP_LOCK(inp);
 1157         if (inp->inp_socket == NULL) {
 1158                 error = ENOENT;
 1159                 goto out;
 1160         }
 1161         error = cr_canseesocket(req->td->td_ucred, inp->inp_socket);
 1162         if (error)
 1163                 goto out;
 1164         cru2x(inp->inp_socket->so_cred, &xuc);
 1165 out:
 1166         INP_UNLOCK(inp);
 1167 outunlocked:
 1168         INP_INFO_RUNLOCK(&tcbinfo);
 1169         if (error == 0)
 1170                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1171         return (error);
 1172 }
 1173 
 1174 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 1175     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1176     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
 1177 #endif
 1178 
 1179 
 1180 void
 1181 tcp_ctlinput(cmd, sa, vip)
 1182         int cmd;
 1183         struct sockaddr *sa;
 1184         void *vip;
 1185 {
 1186         struct ip *ip = vip;
 1187         struct tcphdr *th;
 1188         struct in_addr faddr;
 1189         struct inpcb *inp;
 1190         struct tcpcb *tp;
 1191         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1192         struct icmp *icp;
 1193         struct in_conninfo inc;
 1194         tcp_seq icmp_tcp_seq;
 1195         int mtu;
 1196 
 1197         faddr = ((struct sockaddr_in *)sa)->sin_addr;
 1198         if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
 1199                 return;
 1200 
 1201         if (cmd == PRC_MSGSIZE)
 1202                 notify = tcp_mtudisc;
 1203         else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
 1204                 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
 1205                 notify = tcp_drop_syn_sent;
 1206         /*
 1207          * Redirects don't need to be handled up here.
 1208          */
 1209         else if (PRC_IS_REDIRECT(cmd))
 1210                 return;
 1211         /*
 1212          * Source quench is depreciated.
 1213          */
 1214         else if (cmd == PRC_QUENCH)
 1215                 return;
 1216         /*
 1217          * Hostdead is ugly because it goes linearly through all PCBs.
 1218          * XXX: We never get this from ICMP, otherwise it makes an
 1219          * excellent DoS attack on machines with many connections.
 1220          */
 1221         else if (cmd == PRC_HOSTDEAD)
 1222                 ip = NULL;
 1223         else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
 1224                 return;
 1225         if (ip != NULL) {
 1226                 icp = (struct icmp *)((caddr_t)ip
 1227                                       - offsetof(struct icmp, icmp_ip));
 1228                 th = (struct tcphdr *)((caddr_t)ip
 1229                                        + (ip->ip_hl << 2));
 1230                 INP_INFO_WLOCK(&tcbinfo);
 1231                 inp = in_pcblookup_hash(&tcbinfo, faddr, th->th_dport,
 1232                     ip->ip_src, th->th_sport, 0, NULL);
 1233                 if (inp != NULL)  {
 1234                         INP_LOCK(inp);
 1235                         if (inp->inp_socket != NULL) {
 1236                                 icmp_tcp_seq = htonl(th->th_seq);
 1237                                 tp = intotcpcb(inp);
 1238                                 if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
 1239                                     SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
 1240                                         if (cmd == PRC_MSGSIZE) {
 1241                                             /*
 1242                                              * MTU discovery:
 1243                                              * If we got a needfrag set the MTU
 1244                                              * in the route to the suggested new
 1245                                              * value (if given) and then notify.
 1246                                              */
 1247                                             bzero(&inc, sizeof(inc));
 1248                                             inc.inc_flags = 0;  /* IPv4 */
 1249                                             inc.inc_faddr = faddr;
 1250 
 1251                                             mtu = ntohs(icp->icmp_nextmtu);
 1252                                             /*
 1253                                              * If no alternative MTU was
 1254                                              * proposed, try the next smaller
 1255                                              * one.  ip->ip_len has already
 1256                                              * been swapped in icmp_input().
 1257                                              */
 1258                                             if (!mtu)
 1259                                                 mtu = ip_next_mtu(ip->ip_len,
 1260                                                  1);
 1261                                             if (mtu < max(296, (tcp_minmss)
 1262                                                  + sizeof(struct tcpiphdr)))
 1263                                                 mtu = 0;
 1264                                             if (!mtu)
 1265                                                 mtu = tcp_mssdflt
 1266                                                  + sizeof(struct tcpiphdr);
 1267                                             /*
 1268                                              * Only cache the the MTU if it
 1269                                              * is smaller than the interface
 1270                                              * or route MTU.  tcp_mtudisc()
 1271                                              * will do right thing by itself.
 1272                                              */
 1273                                             if (mtu <= tcp_maxmtu(&inc))
 1274                                                 tcp_hc_updatemtu(&inc, mtu);
 1275                                         }
 1276 
 1277                                         inp = (*notify)(inp, inetctlerrmap[cmd]);
 1278                                 }
 1279                         }
 1280                         if (inp != NULL)
 1281                                 INP_UNLOCK(inp);
 1282                 } else {
 1283                         inc.inc_fport = th->th_dport;
 1284                         inc.inc_lport = th->th_sport;
 1285                         inc.inc_faddr = faddr;
 1286                         inc.inc_laddr = ip->ip_src;
 1287 #ifdef INET6
 1288                         inc.inc_isipv6 = 0;
 1289 #endif
 1290                         syncache_unreach(&inc, th);
 1291                 }
 1292                 INP_INFO_WUNLOCK(&tcbinfo);
 1293         } else
 1294                 in_pcbnotifyall(&tcbinfo, faddr, inetctlerrmap[cmd], notify);
 1295 }
 1296 
 1297 #ifdef INET6
 1298 void
 1299 tcp6_ctlinput(cmd, sa, d)
 1300         int cmd;
 1301         struct sockaddr *sa;
 1302         void *d;
 1303 {
 1304         struct tcphdr th;
 1305         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1306         struct ip6_hdr *ip6;
 1307         struct mbuf *m;
 1308         struct ip6ctlparam *ip6cp = NULL;
 1309         const struct sockaddr_in6 *sa6_src = NULL;
 1310         int off;
 1311         struct tcp_portonly {
 1312                 u_int16_t th_sport;
 1313                 u_int16_t th_dport;
 1314         } *thp;
 1315 
 1316         if (sa->sa_family != AF_INET6 ||
 1317             sa->sa_len != sizeof(struct sockaddr_in6))
 1318                 return;
 1319 
 1320         if (cmd == PRC_MSGSIZE)
 1321                 notify = tcp_mtudisc;
 1322         else if (!PRC_IS_REDIRECT(cmd) &&
 1323                  ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
 1324                 return;
 1325         /* Source quench is depreciated. */
 1326         else if (cmd == PRC_QUENCH)
 1327                 return;
 1328 
 1329         /* if the parameter is from icmp6, decode it. */
 1330         if (d != NULL) {
 1331                 ip6cp = (struct ip6ctlparam *)d;
 1332                 m = ip6cp->ip6c_m;
 1333                 ip6 = ip6cp->ip6c_ip6;
 1334                 off = ip6cp->ip6c_off;
 1335                 sa6_src = ip6cp->ip6c_src;
 1336         } else {
 1337                 m = NULL;
 1338                 ip6 = NULL;
 1339                 off = 0;        /* fool gcc */
 1340                 sa6_src = &sa6_any;
 1341         }
 1342 
 1343         if (ip6 != NULL) {
 1344                 struct in_conninfo inc;
 1345                 /*
 1346                  * XXX: We assume that when IPV6 is non NULL,
 1347                  * M and OFF are valid.
 1348                  */
 1349 
 1350                 /* check if we can safely examine src and dst ports */
 1351                 if (m->m_pkthdr.len < off + sizeof(*thp))
 1352                         return;
 1353 
 1354                 bzero(&th, sizeof(th));
 1355                 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
 1356 
 1357                 in6_pcbnotify(&tcbinfo, sa, th.th_dport,
 1358                     (struct sockaddr *)ip6cp->ip6c_src,
 1359                     th.th_sport, cmd, NULL, notify);
 1360 
 1361                 inc.inc_fport = th.th_dport;
 1362                 inc.inc_lport = th.th_sport;
 1363                 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
 1364                 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
 1365                 inc.inc_isipv6 = 1;
 1366                 INP_INFO_WLOCK(&tcbinfo);
 1367                 syncache_unreach(&inc, &th);
 1368                 INP_INFO_WUNLOCK(&tcbinfo);
 1369         } else
 1370                 in6_pcbnotify(&tcbinfo, sa, 0, (const struct sockaddr *)sa6_src,
 1371                               0, cmd, NULL, notify);
 1372 }
 1373 #endif /* INET6 */
 1374 
 1375 
 1376 /*
 1377  * Following is where TCP initial sequence number generation occurs.
 1378  *
 1379  * There are two places where we must use initial sequence numbers:
 1380  * 1.  In SYN-ACK packets.
 1381  * 2.  In SYN packets.
 1382  *
 1383  * All ISNs for SYN-ACK packets are generated by the syncache.  See
 1384  * tcp_syncache.c for details.
 1385  *
 1386  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 1387  * depends on this property.  In addition, these ISNs should be
 1388  * unguessable so as to prevent connection hijacking.  To satisfy
 1389  * the requirements of this situation, the algorithm outlined in
 1390  * RFC 1948 is used, with only small modifications.
 1391  *
 1392  * Implementation details:
 1393  *
 1394  * Time is based off the system timer, and is corrected so that it
 1395  * increases by one megabyte per second.  This allows for proper
 1396  * recycling on high speed LANs while still leaving over an hour
 1397  * before rollover.
 1398  *
 1399  * As reading the *exact* system time is too expensive to be done
 1400  * whenever setting up a TCP connection, we increment the time
 1401  * offset in two ways.  First, a small random positive increment
 1402  * is added to isn_offset for each connection that is set up.
 1403  * Second, the function tcp_isn_tick fires once per clock tick
 1404  * and increments isn_offset as necessary so that sequence numbers
 1405  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
 1406  * random positive increments serve only to ensure that the same
 1407  * exact sequence number is never sent out twice (as could otherwise
 1408  * happen when a port is recycled in less than the system tick
 1409  * interval.)
 1410  *
 1411  * net.inet.tcp.isn_reseed_interval controls the number of seconds
 1412  * between seeding of isn_secret.  This is normally set to zero,
 1413  * as reseeding should not be necessary.
 1414  *
 1415  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
 1416  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
 1417  * general, this means holding an exclusive (write) lock.
 1418  */
 1419 
 1420 #define ISN_BYTES_PER_SECOND 1048576
 1421 #define ISN_STATIC_INCREMENT 4096
 1422 #define ISN_RANDOM_INCREMENT (4096 - 1)
 1423 
 1424 static u_char isn_secret[32];
 1425 static int isn_last_reseed;
 1426 static u_int32_t isn_offset, isn_offset_old;
 1427 static MD5_CTX isn_ctx;
 1428 
 1429 tcp_seq
 1430 tcp_new_isn(tp)
 1431         struct tcpcb *tp;
 1432 {
 1433         u_int32_t md5_buffer[4];
 1434         tcp_seq new_isn;
 1435 
 1436         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1437         INP_LOCK_ASSERT(tp->t_inpcb);
 1438 
 1439         /* Seed if this is the first use, reseed if requested. */
 1440         if ((isn_last_reseed == 0) || ((tcp_isn_reseed_interval > 0) &&
 1441              (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval*hz)
 1442                 < (u_int)ticks))) {
 1443                 read_random(&isn_secret, sizeof(isn_secret));
 1444                 isn_last_reseed = ticks;
 1445         }
 1446 
 1447         /* Compute the md5 hash and return the ISN. */
 1448         MD5Init(&isn_ctx);
 1449         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
 1450         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
 1451 #ifdef INET6
 1452         if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
 1453                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
 1454                           sizeof(struct in6_addr));
 1455                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
 1456                           sizeof(struct in6_addr));
 1457         } else
 1458 #endif
 1459         {
 1460                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
 1461                           sizeof(struct in_addr));
 1462                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
 1463                           sizeof(struct in_addr));
 1464         }
 1465         MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret));
 1466         MD5Final((u_char *) &md5_buffer, &isn_ctx);
 1467         new_isn = (tcp_seq) md5_buffer[0];
 1468         isn_offset += ISN_STATIC_INCREMENT +
 1469                 (arc4random() & ISN_RANDOM_INCREMENT);
 1470         new_isn += isn_offset;
 1471         return (new_isn);
 1472 }
 1473 
 1474 /*
 1475  * Increment the offset to the next ISN_BYTES_PER_SECOND / 100 boundary
 1476  * to keep time flowing at a relatively constant rate.  If the random
 1477  * increments have already pushed us past the projected offset, do nothing.
 1478  */
 1479 static void
 1480 tcp_isn_tick(xtp)
 1481         void *xtp;
 1482 {
 1483         u_int32_t projected_offset;
 1484 
 1485         INP_INFO_WLOCK(&tcbinfo);
 1486         projected_offset = isn_offset_old + ISN_BYTES_PER_SECOND / 100;
 1487 
 1488         if (SEQ_GT(projected_offset, isn_offset))
 1489                 isn_offset = projected_offset;
 1490 
 1491         isn_offset_old = isn_offset;
 1492         callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
 1493         INP_INFO_WUNLOCK(&tcbinfo);
 1494 }
 1495 
 1496 /*
 1497  * When a specific ICMP unreachable message is received and the
 1498  * connection state is SYN-SENT, drop the connection.  This behavior
 1499  * is controlled by the icmp_may_rst sysctl.
 1500  */
 1501 struct inpcb *
 1502 tcp_drop_syn_sent(inp, errno)
 1503         struct inpcb *inp;
 1504         int errno;
 1505 {
 1506         struct tcpcb *tp = intotcpcb(inp);
 1507 
 1508         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1509         INP_LOCK_ASSERT(inp);
 1510 
 1511         if (tp != NULL && tp->t_state == TCPS_SYN_SENT) {
 1512                 tcp_drop(tp, errno);
 1513                 return (NULL);
 1514         }
 1515         return (inp);
 1516 }
 1517 
 1518 /*
 1519  * When `need fragmentation' ICMP is received, update our idea of the MSS
 1520  * based on the new value in the route.  Also nudge TCP to send something,
 1521  * since we know the packet we just sent was dropped.
 1522  * This duplicates some code in the tcp_mss() function in tcp_input.c.
 1523  */
 1524 struct inpcb *
 1525 tcp_mtudisc(inp, errno)
 1526         struct inpcb *inp;
 1527         int errno;
 1528 {
 1529         struct tcpcb *tp = intotcpcb(inp);
 1530         struct socket *so = inp->inp_socket;
 1531         u_int maxmtu;
 1532         u_int romtu;
 1533         int mss;
 1534 #ifdef INET6
 1535         int isipv6;
 1536 #endif /* INET6 */
 1537 
 1538         INP_LOCK_ASSERT(inp);
 1539         if (tp != NULL) {
 1540 #ifdef INET6
 1541                 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
 1542 #endif
 1543                 maxmtu = tcp_hc_getmtu(&inp->inp_inc); /* IPv4 and IPv6 */
 1544                 romtu =
 1545 #ifdef INET6
 1546                     isipv6 ? tcp_maxmtu6(&inp->inp_inc) :
 1547 #endif /* INET6 */
 1548                     tcp_maxmtu(&inp->inp_inc);
 1549                 if (!maxmtu)
 1550                         maxmtu = romtu;
 1551                 else
 1552                         maxmtu = min(maxmtu, romtu);
 1553                 if (!maxmtu) {
 1554                         tp->t_maxopd = tp->t_maxseg =
 1555 #ifdef INET6
 1556                                 isipv6 ? tcp_v6mssdflt :
 1557 #endif /* INET6 */
 1558                                 tcp_mssdflt;
 1559                         return (inp);
 1560                 }
 1561                 mss = maxmtu -
 1562 #ifdef INET6
 1563                         (isipv6 ?
 1564                          sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
 1565 #endif /* INET6 */
 1566                          sizeof(struct tcpiphdr)
 1567 #ifdef INET6
 1568                          )
 1569 #endif /* INET6 */
 1570                         ;
 1571 
 1572                 /*
 1573                  * XXX - The above conditional probably violates the TCP
 1574                  * spec.  The problem is that, since we don't know the
 1575                  * other end's MSS, we are supposed to use a conservative
 1576                  * default.  But, if we do that, then MTU discovery will
 1577                  * never actually take place, because the conservative
 1578                  * default is much less than the MTUs typically seen
 1579                  * on the Internet today.  For the moment, we'll sweep
 1580                  * this under the carpet.
 1581                  *
 1582                  * The conservative default might not actually be a problem
 1583                  * if the only case this occurs is when sending an initial
 1584                  * SYN with options and data to a host we've never talked
 1585                  * to before.  Then, they will reply with an MSS value which
 1586                  * will get recorded and the new parameters should get
 1587                  * recomputed.  For Further Study.
 1588                  */
 1589                 if (tp->t_maxopd <= mss)
 1590                         return (inp);
 1591                 tp->t_maxopd = mss;
 1592 
 1593                 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 1594                     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
 1595                         mss -= TCPOLEN_TSTAMP_APPA;
 1596 #if     (MCLBYTES & (MCLBYTES - 1)) == 0
 1597                 if (mss > MCLBYTES)
 1598                         mss &= ~(MCLBYTES-1);
 1599 #else
 1600                 if (mss > MCLBYTES)
 1601                         mss = mss / MCLBYTES * MCLBYTES;
 1602 #endif
 1603                 if (so->so_snd.sb_hiwat < mss)
 1604                         mss = so->so_snd.sb_hiwat;
 1605 
 1606                 tp->t_maxseg = mss;
 1607 
 1608                 tcpstat.tcps_mturesent++;
 1609                 tp->t_rtttime = 0;
 1610                 tp->snd_nxt = tp->snd_una;
 1611                 tcp_free_sackholes(tp);
 1612                 tp->snd_recover = tp->snd_max;
 1613                 if (tp->sack_enable)
 1614                         EXIT_FASTRECOVERY(tp);
 1615                 tcp_output(tp);
 1616         }
 1617         return (inp);
 1618 }
 1619 
 1620 /*
 1621  * Look-up the routing entry to the peer of this inpcb.  If no route
 1622  * is found and it cannot be allocated, then return NULL.  This routine
 1623  * is called by TCP routines that access the rmx structure and by tcp_mss
 1624  * to get the interface MTU.
 1625  */
 1626 u_long
 1627 tcp_maxmtu(inc)
 1628         struct in_conninfo *inc;
 1629 {
 1630         struct route sro;
 1631         struct sockaddr_in *dst;
 1632         struct ifnet *ifp;
 1633         u_long maxmtu = 0;
 1634 
 1635         KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
 1636 
 1637         bzero(&sro, sizeof(sro));
 1638         if (inc->inc_faddr.s_addr != INADDR_ANY) {
 1639                 dst = (struct sockaddr_in *)&sro.ro_dst;
 1640                 dst->sin_family = AF_INET;
 1641                 dst->sin_len = sizeof(*dst);
 1642                 dst->sin_addr = inc->inc_faddr;
 1643                 rtalloc_ign(&sro, RTF_CLONING);
 1644         }
 1645         if (sro.ro_rt != NULL) {
 1646                 ifp = sro.ro_rt->rt_ifp;
 1647                 if (sro.ro_rt->rt_rmx.rmx_mtu == 0)
 1648                         maxmtu = ifp->if_mtu;
 1649                 else
 1650                         maxmtu = min(sro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
 1651                 RTFREE(sro.ro_rt);
 1652         }
 1653         return (maxmtu);
 1654 }
 1655 
 1656 #ifdef INET6
 1657 u_long
 1658 tcp_maxmtu6(inc)
 1659         struct in_conninfo *inc;
 1660 {
 1661         struct route_in6 sro6;
 1662         struct ifnet *ifp;
 1663         u_long maxmtu = 0;
 1664 
 1665         KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
 1666 
 1667         bzero(&sro6, sizeof(sro6));
 1668         if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
 1669                 sro6.ro_dst.sin6_family = AF_INET6;
 1670                 sro6.ro_dst.sin6_len = sizeof(struct sockaddr_in6);
 1671                 sro6.ro_dst.sin6_addr = inc->inc6_faddr;
 1672                 rtalloc_ign((struct route *)&sro6, RTF_CLONING);
 1673         }
 1674         if (sro6.ro_rt != NULL) {
 1675                 ifp = sro6.ro_rt->rt_ifp;
 1676                 if (sro6.ro_rt->rt_rmx.rmx_mtu == 0)
 1677                         maxmtu = IN6_LINKMTU(sro6.ro_rt->rt_ifp);
 1678                 else
 1679                         maxmtu = min(sro6.ro_rt->rt_rmx.rmx_mtu,
 1680                                      IN6_LINKMTU(sro6.ro_rt->rt_ifp));
 1681                 RTFREE(sro6.ro_rt);
 1682         }
 1683 
 1684         return (maxmtu);
 1685 }
 1686 #endif /* INET6 */
 1687 
 1688 #ifdef IPSEC
 1689 /* compute ESP/AH header size for TCP, including outer IP header. */
 1690 size_t
 1691 ipsec_hdrsiz_tcp(tp)
 1692         struct tcpcb *tp;
 1693 {
 1694         struct inpcb *inp;
 1695         struct mbuf *m;
 1696         size_t hdrsiz;
 1697         struct ip *ip;
 1698 #ifdef INET6
 1699         struct ip6_hdr *ip6;
 1700 #endif
 1701         struct tcphdr *th;
 1702 
 1703         if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
 1704                 return (0);
 1705         MGETHDR(m, M_DONTWAIT, MT_DATA);
 1706         if (!m)
 1707                 return (0);
 1708 
 1709 #ifdef INET6
 1710         if ((inp->inp_vflag & INP_IPV6) != 0) {
 1711                 ip6 = mtod(m, struct ip6_hdr *);
 1712                 th = (struct tcphdr *)(ip6 + 1);
 1713                 m->m_pkthdr.len = m->m_len =
 1714                         sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1715                 tcpip_fillheaders(inp, ip6, th);
 1716                 hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1717         } else
 1718 #endif /* INET6 */
 1719         {
 1720                 ip = mtod(m, struct ip *);
 1721                 th = (struct tcphdr *)(ip + 1);
 1722                 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
 1723                 tcpip_fillheaders(inp, ip, th);
 1724                 hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1725         }
 1726 
 1727         m_free(m);
 1728         return (hdrsiz);
 1729 }
 1730 #endif /*IPSEC*/
 1731 
 1732 /*
 1733  * Move a TCP connection into TIME_WAIT state.
 1734  *    tcbinfo is locked.
 1735  *    inp is locked, and is unlocked before returning.
 1736  */
 1737 void
 1738 tcp_twstart(tp)
 1739         struct tcpcb *tp;
 1740 {
 1741         struct tcptw *tw;
 1742         struct inpcb *inp = tp->t_inpcb;
 1743         int acknow;
 1744         struct socket *so;
 1745 
 1746         INP_INFO_WLOCK_ASSERT(&tcbinfo);        /* tcp_timer_2msl_reset(). */
 1747         INP_LOCK_ASSERT(inp);
 1748 
 1749         if (nolocaltimewait && in_localip(inp->inp_faddr)) {
 1750                 tcp_close(tp);
 1751                 return;
 1752         }
 1753 
 1754         tw = uma_zalloc(tcptw_zone, M_NOWAIT);
 1755         if (tw == NULL) {
 1756                 tw = tcp_timer_2msl_tw(1);
 1757                 if (tw == NULL) {
 1758                         tcp_close(tp);
 1759                         return;
 1760                 }
 1761         }
 1762         tw->tw_inpcb = inp;
 1763 
 1764         /*
 1765          * Recover last window size sent.
 1766          */
 1767         tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
 1768 
 1769         /*
 1770          * Set t_recent if timestamps are used on the connection.
 1771          */
 1772         if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
 1773             (TF_REQ_TSTMP|TF_RCVD_TSTMP))
 1774                 tw->t_recent = tp->ts_recent;
 1775         else
 1776                 tw->t_recent = 0;
 1777 
 1778         tw->snd_nxt = tp->snd_nxt;
 1779         tw->rcv_nxt = tp->rcv_nxt;
 1780         tw->iss     = tp->iss;
 1781         tw->irs     = tp->irs;
 1782         tw->t_starttime = tp->t_starttime;
 1783         tw->tw_time = 0;
 1784 
 1785 /* XXX
 1786  * If this code will
 1787  * be used for fin-wait-2 state also, then we may need
 1788  * a ts_recent from the last segment.
 1789  */
 1790         acknow = tp->t_flags & TF_ACKNOW;
 1791         tcp_discardcb(tp);
 1792         so = inp->inp_socket;
 1793         ACCEPT_LOCK();
 1794         SOCK_LOCK(so);
 1795         so->so_pcb = NULL;
 1796         tw->tw_cred = crhold(so->so_cred);
 1797         tw->tw_so_options = so->so_options;
 1798         sotryfree(so);
 1799         inp->inp_socket = NULL;
 1800         if (acknow)
 1801                 tcp_twrespond(tw, TH_ACK);
 1802         inp->inp_ppcb = (caddr_t)tw;
 1803         inp->inp_vflag |= INP_TIMEWAIT;
 1804         tcp_timer_2msl_reset(tw, 0);
 1805         INP_UNLOCK(inp);
 1806 }
 1807 
 1808 #if 0
 1809 /*
 1810  * The appromixate rate of ISN increase of Microsoft TCP stacks;
 1811  * the actual rate is slightly higher due to the addition of
 1812  * random positive increments.
 1813  *
 1814  * Most other new OSes use semi-randomized ISN values, so we
 1815  * do not need to worry about them.
 1816  */
 1817 #define MS_ISN_BYTES_PER_SECOND         250000
 1818 
 1819 /*
 1820  * Determine if the ISN we will generate has advanced beyond the last
 1821  * sequence number used by the previous connection.  If so, indicate
 1822  * that it is safe to recycle this tw socket by returning 1.
 1823  */
 1824 int
 1825 tcp_twrecycleable(struct tcptw *tw)
 1826 {
 1827         tcp_seq new_iss = tw->iss;
 1828         tcp_seq new_irs = tw->irs;
 1829 
 1830         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1831         new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
 1832         new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
 1833 
 1834         if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
 1835                 return (1);
 1836         else
 1837                 return (0);
 1838 }
 1839 #endif
 1840 
 1841 void
 1842 tcp_twclose(struct tcptw *tw, int reuse)
 1843 {
 1844         struct inpcb *inp;
 1845 
 1846         inp = tw->tw_inpcb;
 1847         INP_INFO_WLOCK_ASSERT(&tcbinfo);        /* tcp_timer_2msl_stop(). */
 1848         INP_LOCK_ASSERT(inp);
 1849 
 1850         tw->tw_inpcb = NULL;
 1851         tcp_timer_2msl_stop(tw);
 1852         inp->inp_ppcb = NULL;
 1853 #ifdef INET6
 1854         if (inp->inp_vflag & INP_IPV6PROTO)
 1855                 in6_pcbdetach(inp);
 1856         else
 1857 #endif
 1858                 in_pcbdetach(inp);
 1859         tcpstat.tcps_closed++;
 1860         crfree(tw->tw_cred);
 1861         tw->tw_cred = NULL;
 1862         if (reuse)
 1863                 return;
 1864         uma_zfree(tcptw_zone, tw);
 1865 }
 1866 
 1867 int
 1868 tcp_twrespond(struct tcptw *tw, int flags)
 1869 {
 1870         struct inpcb *inp = tw->tw_inpcb;
 1871         struct tcphdr *th;
 1872         struct mbuf *m;
 1873         struct ip *ip = NULL;
 1874         u_int8_t *optp;
 1875         u_int hdrlen, optlen;
 1876         int error;
 1877 #ifdef INET6
 1878         struct ip6_hdr *ip6 = NULL;
 1879         int isipv6 = inp->inp_inc.inc_isipv6;
 1880 #endif
 1881 
 1882         INP_LOCK_ASSERT(inp);
 1883 
 1884         m = m_gethdr(M_DONTWAIT, MT_HEADER);
 1885         if (m == NULL)
 1886                 return (ENOBUFS);
 1887         m->m_data += max_linkhdr;
 1888 
 1889 #ifdef MAC
 1890         mac_create_mbuf_from_inpcb(inp, m);
 1891 #endif
 1892 
 1893 #ifdef INET6
 1894         if (isipv6) {
 1895                 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1896                 ip6 = mtod(m, struct ip6_hdr *);
 1897                 th = (struct tcphdr *)(ip6 + 1);
 1898                 tcpip_fillheaders(inp, ip6, th);
 1899         } else
 1900 #endif
 1901         {
 1902                 hdrlen = sizeof(struct tcpiphdr);
 1903                 ip = mtod(m, struct ip *);
 1904                 th = (struct tcphdr *)(ip + 1);
 1905                 tcpip_fillheaders(inp, ip, th);
 1906         }
 1907         optp = (u_int8_t *)(th + 1);
 1908 
 1909         /*
 1910          * Send a timestamp and echo-reply if both our side and our peer
 1911          * have sent timestamps in our SYN's and this is not a RST.
 1912          */
 1913         if (tw->t_recent && flags == TH_ACK) {
 1914                 u_int32_t *lp = (u_int32_t *)optp;
 1915 
 1916                 /* Form timestamp option as shown in appendix A of RFC 1323. */
 1917                 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
 1918                 *lp++ = htonl(ticks);
 1919                 *lp   = htonl(tw->t_recent);
 1920                 optp += TCPOLEN_TSTAMP_APPA;
 1921         }
 1922 
 1923         optlen = optp - (u_int8_t *)(th + 1);
 1924 
 1925         m->m_len = hdrlen + optlen;
 1926         m->m_pkthdr.len = m->m_len;
 1927 
 1928         KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
 1929 
 1930         th->th_seq = htonl(tw->snd_nxt);
 1931         th->th_ack = htonl(tw->rcv_nxt);
 1932         th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
 1933         th->th_flags = flags;
 1934         th->th_win = htons(tw->last_win);
 1935 
 1936 #ifdef INET6
 1937         if (isipv6) {
 1938                 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
 1939                     sizeof(struct tcphdr) + optlen);
 1940                 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
 1941                 error = ip6_output(m, inp->in6p_outputopts, NULL,
 1942                     (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
 1943         } else
 1944 #endif
 1945         {
 1946                 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
 1947                     htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
 1948                 m->m_pkthdr.csum_flags = CSUM_TCP;
 1949                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 1950                 ip->ip_len = m->m_pkthdr.len;
 1951                 if (path_mtu_discovery)
 1952                         ip->ip_off |= IP_DF;
 1953                 error = ip_output(m, inp->inp_options, NULL,
 1954                     ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
 1955                     NULL, inp);
 1956         }
 1957         if (flags & TH_ACK)
 1958                 tcpstat.tcps_sndacks++;
 1959         else
 1960                 tcpstat.tcps_sndctrl++;
 1961         tcpstat.tcps_sndtotal++;
 1962         return (error);
 1963 }
 1964 
 1965 /*
 1966  * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING
 1967  *
 1968  * This code attempts to calculate the bandwidth-delay product as a
 1969  * means of determining the optimal window size to maximize bandwidth,
 1970  * minimize RTT, and avoid the over-allocation of buffers on interfaces and
 1971  * routers.  This code also does a fairly good job keeping RTTs in check
 1972  * across slow links like modems.  We implement an algorithm which is very
 1973  * similar (but not meant to be) TCP/Vegas.  The code operates on the
 1974  * transmitter side of a TCP connection and so only effects the transmit
 1975  * side of the connection.
 1976  *
 1977  * BACKGROUND:  TCP makes no provision for the management of buffer space
 1978  * at the end points or at the intermediate routers and switches.  A TCP
 1979  * stream, whether using NewReno or not, will eventually buffer as
 1980  * many packets as it is able and the only reason this typically works is
 1981  * due to the fairly small default buffers made available for a connection
 1982  * (typicaly 16K or 32K).  As machines use larger windows and/or window
 1983  * scaling it is now fairly easy for even a single TCP connection to blow-out
 1984  * all available buffer space not only on the local interface, but on
 1985  * intermediate routers and switches as well.  NewReno makes a misguided
 1986  * attempt to 'solve' this problem by waiting for an actual failure to occur,
 1987  * then backing off, then steadily increasing the window again until another
 1988  * failure occurs, ad-infinitum.  This results in terrible oscillation that
 1989  * is only made worse as network loads increase and the idea of intentionally
 1990  * blowing out network buffers is, frankly, a terrible way to manage network
 1991  * resources.
 1992  *
 1993  * It is far better to limit the transmit window prior to the failure
 1994  * condition being achieved.  There are two general ways to do this:  First
 1995  * you can 'scan' through different transmit window sizes and locate the
 1996  * point where the RTT stops increasing, indicating that you have filled the
 1997  * pipe, then scan backwards until you note that RTT stops decreasing, then
 1998  * repeat ad-infinitum.  This method works in principle but has severe
 1999  * implementation issues due to RTT variances, timer granularity, and
 2000  * instability in the algorithm which can lead to many false positives and
 2001  * create oscillations as well as interact badly with other TCP streams
 2002  * implementing the same algorithm.
 2003  *
 2004  * The second method is to limit the window to the bandwidth delay product
 2005  * of the link.  This is the method we implement.  RTT variances and our
 2006  * own manipulation of the congestion window, bwnd, can potentially
 2007  * destabilize the algorithm.  For this reason we have to stabilize the
 2008  * elements used to calculate the window.  We do this by using the minimum
 2009  * observed RTT, the long term average of the observed bandwidth, and
 2010  * by adding two segments worth of slop.  It isn't perfect but it is able
 2011  * to react to changing conditions and gives us a very stable basis on
 2012  * which to extend the algorithm.
 2013  */
 2014 void
 2015 tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq)
 2016 {
 2017         u_long bw;
 2018         u_long bwnd;
 2019         int save_ticks;
 2020 
 2021         INP_LOCK_ASSERT(tp->t_inpcb);
 2022 
 2023         /*
 2024          * If inflight_enable is disabled in the middle of a tcp connection,
 2025          * make sure snd_bwnd is effectively disabled.
 2026          */
 2027         if (tcp_inflight_enable == 0 || tp->t_rttlow < tcp_inflight_rttthresh) {
 2028                 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 2029                 tp->snd_bandwidth = 0;
 2030                 return;
 2031         }
 2032 
 2033         /*
 2034          * Figure out the bandwidth.  Due to the tick granularity this
 2035          * is a very rough number and it MUST be averaged over a fairly
 2036          * long period of time.  XXX we need to take into account a link
 2037          * that is not using all available bandwidth, but for now our
 2038          * slop will ramp us up if this case occurs and the bandwidth later
 2039          * increases.
 2040          *
 2041          * Note: if ticks rollover 'bw' may wind up negative.  We must
 2042          * effectively reset t_bw_rtttime for this case.
 2043          */
 2044         save_ticks = ticks;
 2045         if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1)
 2046                 return;
 2047 
 2048         bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz /
 2049             (save_ticks - tp->t_bw_rtttime);
 2050         tp->t_bw_rtttime = save_ticks;
 2051         tp->t_bw_rtseq = ack_seq;
 2052         if (tp->t_bw_rtttime == 0 || (int)bw < 0)
 2053                 return;
 2054         bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4;
 2055 
 2056         tp->snd_bandwidth = bw;
 2057 
 2058         /*
 2059          * Calculate the semi-static bandwidth delay product, plus two maximal
 2060          * segments.  The additional slop puts us squarely in the sweet
 2061          * spot and also handles the bandwidth run-up case and stabilization.
 2062          * Without the slop we could be locking ourselves into a lower
 2063          * bandwidth.
 2064          *
 2065          * Situations Handled:
 2066          *      (1) Prevents over-queueing of packets on LANs, especially on
 2067          *          high speed LANs, allowing larger TCP buffers to be
 2068          *          specified, and also does a good job preventing
 2069          *          over-queueing of packets over choke points like modems
 2070          *          (at least for the transmit side).
 2071          *
 2072          *      (2) Is able to handle changing network loads (bandwidth
 2073          *          drops so bwnd drops, bandwidth increases so bwnd
 2074          *          increases).
 2075          *
 2076          *      (3) Theoretically should stabilize in the face of multiple
 2077          *          connections implementing the same algorithm (this may need
 2078          *          a little work).
 2079          *
 2080          *      (4) Stability value (defaults to 20 = 2 maximal packets) can
 2081          *          be adjusted with a sysctl but typically only needs to be
 2082          *          on very slow connections.  A value no smaller then 5
 2083          *          should be used, but only reduce this default if you have
 2084          *          no other choice.
 2085          */
 2086 #define USERTT  ((tp->t_srtt + tp->t_rttbest) / 2)
 2087         bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + tcp_inflight_stab * tp->t_maxseg / 10;
 2088 #undef USERTT
 2089 
 2090         if (tcp_inflight_debug > 0) {
 2091                 static int ltime;
 2092                 if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) {
 2093                         ltime = ticks;
 2094                         printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n",
 2095                             tp,
 2096                             bw,
 2097                             tp->t_rttbest,
 2098                             tp->t_srtt,
 2099                             bwnd
 2100                         );
 2101                 }
 2102         }
 2103         if ((long)bwnd < tcp_inflight_min)
 2104                 bwnd = tcp_inflight_min;
 2105         if (bwnd > tcp_inflight_max)
 2106                 bwnd = tcp_inflight_max;
 2107         if ((long)bwnd < tp->t_maxseg * 2)
 2108                 bwnd = tp->t_maxseg * 2;
 2109         tp->snd_bwnd = bwnd;
 2110 }
 2111 
 2112 #ifdef TCP_SIGNATURE
 2113 /*
 2114  * Callback function invoked by m_apply() to digest TCP segment data
 2115  * contained within an mbuf chain.
 2116  */
 2117 static int
 2118 tcp_signature_apply(void *fstate, void *data, u_int len)
 2119 {
 2120 
 2121         MD5Update(fstate, (u_char *)data, len);
 2122         return (0);
 2123 }
 2124 
 2125 /*
 2126  * Compute TCP-MD5 hash of a TCPv4 segment. (RFC2385)
 2127  *
 2128  * Parameters:
 2129  * m            pointer to head of mbuf chain
 2130  * off0         offset to TCP header within the mbuf chain
 2131  * len          length of TCP segment data, excluding options
 2132  * optlen       length of TCP segment options
 2133  * buf          pointer to storage for computed MD5 digest
 2134  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 2135  *
 2136  * We do this over ip, tcphdr, segment data, and the key in the SADB.
 2137  * When called from tcp_input(), we can be sure that th_sum has been
 2138  * zeroed out and verified already.
 2139  *
 2140  * This function is for IPv4 use only. Calling this function with an
 2141  * IPv6 packet in the mbuf chain will yield undefined results.
 2142  *
 2143  * Return 0 if successful, otherwise return -1.
 2144  *
 2145  * XXX The key is retrieved from the system's PF_KEY SADB, by keying a
 2146  * search with the destination IP address, and a 'magic SPI' to be
 2147  * determined by the application. This is hardcoded elsewhere to 1179
 2148  * right now. Another branch of this code exists which uses the SPD to
 2149  * specify per-application flows but it is unstable.
 2150  */
 2151 int
 2152 tcp_signature_compute(struct mbuf *m, int off0, int len, int optlen,
 2153     u_char *buf, u_int direction)
 2154 {
 2155         union sockaddr_union dst;
 2156         struct ippseudo ippseudo;
 2157         MD5_CTX ctx;
 2158         int doff;
 2159         struct ip *ip;
 2160         struct ipovly *ipovly;
 2161         struct secasvar *sav;
 2162         struct tcphdr *th;
 2163         u_short savecsum;
 2164 
 2165         KASSERT(m != NULL, ("NULL mbuf chain"));
 2166         KASSERT(buf != NULL, ("NULL signature pointer"));
 2167 
 2168         /* Extract the destination from the IP header in the mbuf. */
 2169         ip = mtod(m, struct ip *);
 2170         bzero(&dst, sizeof(union sockaddr_union));
 2171         dst.sa.sa_len = sizeof(struct sockaddr_in);
 2172         dst.sa.sa_family = AF_INET;
 2173         dst.sin.sin_addr = (direction == IPSEC_DIR_INBOUND) ?
 2174             ip->ip_src : ip->ip_dst;
 2175 
 2176         /* Look up an SADB entry which matches the address of the peer. */
 2177         sav = KEY_ALLOCSA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI));
 2178         if (sav == NULL) {
 2179                 printf("%s: SADB lookup failed for %s\n", __func__,
 2180                     inet_ntoa(dst.sin.sin_addr));
 2181                 return (EINVAL);
 2182         }
 2183 
 2184         MD5Init(&ctx);
 2185         ipovly = (struct ipovly *)ip;
 2186         th = (struct tcphdr *)((u_char *)ip + off0);
 2187         doff = off0 + sizeof(struct tcphdr) + optlen;
 2188 
 2189         /*
 2190          * Step 1: Update MD5 hash with IP pseudo-header.
 2191          *
 2192          * XXX The ippseudo header MUST be digested in network byte order,
 2193          * or else we'll fail the regression test. Assume all fields we've
 2194          * been doing arithmetic on have been in host byte order.
 2195          * XXX One cannot depend on ipovly->ih_len here. When called from
 2196          * tcp_output(), the underlying ip_len member has not yet been set.
 2197          */
 2198         ippseudo.ippseudo_src = ipovly->ih_src;
 2199         ippseudo.ippseudo_dst = ipovly->ih_dst;
 2200         ippseudo.ippseudo_pad = 0;
 2201         ippseudo.ippseudo_p = IPPROTO_TCP;
 2202         ippseudo.ippseudo_len = htons(len + sizeof(struct tcphdr) + optlen);
 2203         MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo));
 2204 
 2205         /*
 2206          * Step 2: Update MD5 hash with TCP header, excluding options.
 2207          * The TCP checksum must be set to zero.
 2208          */
 2209         savecsum = th->th_sum;
 2210         th->th_sum = 0;
 2211         MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
 2212         th->th_sum = savecsum;
 2213 
 2214         /*
 2215          * Step 3: Update MD5 hash with TCP segment data.
 2216          *         Use m_apply() to avoid an early m_pullup().
 2217          */
 2218         if (len > 0)
 2219                 m_apply(m, doff, len, tcp_signature_apply, &ctx);
 2220 
 2221         /*
 2222          * Step 4: Update MD5 hash with shared secret.
 2223          */
 2224         MD5Update(&ctx, _KEYBUF(sav->key_auth), _KEYLEN(sav->key_auth));
 2225         MD5Final(buf, &ctx);
 2226 
 2227         key_sa_recordxfer(sav, m);
 2228         KEY_FREESAV(&sav);
 2229         return (0);
 2230 }
 2231 #endif /* TCP_SIGNATURE */
 2232 
 2233 static int
 2234 sysctl_drop(SYSCTL_HANDLER_ARGS)
 2235 {
 2236         /* addrs[0] is a foreign socket, addrs[1] is a local one. */
 2237         struct sockaddr_storage addrs[2];
 2238         struct inpcb *inp;
 2239         struct tcpcb *tp;
 2240         struct tcptw *tw;
 2241         struct sockaddr_in *fin, *lin;
 2242 #ifdef INET6
 2243         struct sockaddr_in6 *fin6, *lin6;
 2244         struct in6_addr f6, l6;
 2245 #endif
 2246         int error;
 2247 
 2248         inp = NULL;
 2249         fin = lin = NULL;
 2250 #ifdef INET6
 2251         fin6 = lin6 = NULL;
 2252 #endif
 2253         error = 0;
 2254 
 2255         if (req->oldptr != NULL || req->oldlen != 0)
 2256                 return (EINVAL);
 2257         if (req->newptr == NULL)
 2258                 return (EPERM);
 2259         if (req->newlen < sizeof(addrs))
 2260                 return (ENOMEM);
 2261         error = SYSCTL_IN(req, &addrs, sizeof(addrs));
 2262         if (error)
 2263                 return (error);
 2264 
 2265         switch (addrs[0].ss_family) {
 2266 #ifdef INET6
 2267         case AF_INET6:
 2268                 fin6 = (struct sockaddr_in6 *)&addrs[0];
 2269                 lin6 = (struct sockaddr_in6 *)&addrs[1];
 2270                 if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
 2271                     lin6->sin6_len != sizeof(struct sockaddr_in6))
 2272                         return (EINVAL);
 2273                 if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
 2274                         if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
 2275                                 return (EINVAL);
 2276                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
 2277                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
 2278                         fin = (struct sockaddr_in *)&addrs[0];
 2279                         lin = (struct sockaddr_in *)&addrs[1];
 2280                         break;
 2281                 }
 2282                 error = sa6_embedscope(fin6, ip6_use_defzone);
 2283                 if (error)
 2284                         return (error);
 2285                 error = sa6_embedscope(lin6, ip6_use_defzone);
 2286                 if (error)
 2287                         return (error);
 2288                 break;
 2289 #endif
 2290         case AF_INET:
 2291                 fin = (struct sockaddr_in *)&addrs[0];
 2292                 lin = (struct sockaddr_in *)&addrs[1];
 2293                 if (fin->sin_len != sizeof(struct sockaddr_in) ||
 2294                     lin->sin_len != sizeof(struct sockaddr_in))
 2295                         return (EINVAL);
 2296                 break;
 2297         default:
 2298                 return (EINVAL);
 2299         }
 2300         INP_INFO_WLOCK(&tcbinfo);
 2301         switch (addrs[0].ss_family) {
 2302 #ifdef INET6
 2303         case AF_INET6:
 2304                 inp = in6_pcblookup_hash(&tcbinfo, &f6, fin6->sin6_port,
 2305                     &l6, lin6->sin6_port, 0, NULL);
 2306                 break;
 2307 #endif
 2308         case AF_INET:
 2309                 inp = in_pcblookup_hash(&tcbinfo, fin->sin_addr, fin->sin_port,
 2310                     lin->sin_addr, lin->sin_port, 0, NULL);
 2311                 break;
 2312         }
 2313         if (inp != NULL) {
 2314                 INP_LOCK(inp);
 2315                 if ((tw = intotw(inp)) &&
 2316                     (inp->inp_vflag & INP_TIMEWAIT) != 0) {
 2317                         (void) tcp_twclose(tw, 0);
 2318                 } else if ((tp = intotcpcb(inp)) &&
 2319                     ((inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
 2320                         tp = tcp_drop(tp, ECONNABORTED);
 2321                         if (tp != NULL)
 2322                                 INP_UNLOCK(inp);
 2323                 } else
 2324                         INP_UNLOCK(inp);
 2325         } else
 2326                 error = ESRCH;
 2327         INP_INFO_WUNLOCK(&tcbinfo);
 2328         return (error);
 2329 }
 2330 
 2331 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
 2332     CTLTYPE_STRUCT|CTLFLAG_WR|CTLFLAG_SKIP, NULL,
 2333     0, sysctl_drop, "", "Drop TCP connection");

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