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

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)tcp_subr.c  8.2 (Berkeley) 5/24/95
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD$");
   34 
   35 #include "opt_compat.h"
   36 #include "opt_inet.h"
   37 #include "opt_inet6.h"
   38 #include "opt_ipsec.h"
   39 #include "opt_mac.h"
   40 #include "opt_tcpdebug.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/callout.h>
   45 #include <sys/kernel.h>
   46 #include <sys/sysctl.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mbuf.h>
   49 #ifdef INET6
   50 #include <sys/domain.h>
   51 #endif
   52 #include <sys/priv.h>
   53 #include <sys/proc.h>
   54 #include <sys/socket.h>
   55 #include <sys/socketvar.h>
   56 #include <sys/protosw.h>
   57 #include <sys/random.h>
   58 
   59 #include <vm/uma.h>
   60 
   61 #include <net/route.h>
   62 #include <net/if.h>
   63 
   64 #include <netinet/in.h>
   65 #include <netinet/in_systm.h>
   66 #include <netinet/ip.h>
   67 #ifdef INET6
   68 #include <netinet/ip6.h>
   69 #endif
   70 #include <netinet/in_pcb.h>
   71 #ifdef INET6
   72 #include <netinet6/in6_pcb.h>
   73 #endif
   74 #include <netinet/in_var.h>
   75 #include <netinet/ip_var.h>
   76 #ifdef INET6
   77 #include <netinet6/ip6_var.h>
   78 #include <netinet6/scope6_var.h>
   79 #include <netinet6/nd6.h>
   80 #endif
   81 #include <netinet/ip_icmp.h>
   82 #include <netinet/tcp.h>
   83 #include <netinet/tcp_fsm.h>
   84 #include <netinet/tcp_seq.h>
   85 #include <netinet/tcp_timer.h>
   86 #include <netinet/tcp_var.h>
   87 #include <netinet/tcp_syncache.h>
   88 #include <netinet/tcp_offload.h>
   89 #ifdef INET6
   90 #include <netinet6/tcp6_var.h>
   91 #endif
   92 #include <netinet/tcpip.h>
   93 #ifdef TCPDEBUG
   94 #include <netinet/tcp_debug.h>
   95 #endif
   96 #include <netinet6/ip6protosw.h>
   97 
   98 #ifdef IPSEC
   99 #include <netipsec/ipsec.h>
  100 #include <netipsec/xform.h>
  101 #ifdef INET6
  102 #include <netipsec/ipsec6.h>
  103 #endif
  104 #include <netipsec/key.h>
  105 #endif /*IPSEC*/
  106 
  107 #include <machine/in_cksum.h>
  108 #include <sys/md5.h>
  109 
  110 #include <security/mac/mac_framework.h>
  111 
  112 int     tcp_mssdflt = TCP_MSS;
  113 SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt, CTLFLAG_RW,
  114     &tcp_mssdflt, 0, "Default TCP Maximum Segment Size");
  115 
  116 #ifdef INET6
  117 int     tcp_v6mssdflt = TCP6_MSS;
  118 SYSCTL_INT(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
  119     CTLFLAG_RW, &tcp_v6mssdflt , 0,
  120     "Default TCP Maximum Segment Size for IPv6");
  121 #endif
  122 
  123 /*
  124  * Minimum MSS we accept and use. This prevents DoS attacks where
  125  * we are forced to a ridiculous low MSS like 20 and send hundreds
  126  * of packets instead of one. The effect scales with the available
  127  * bandwidth and quickly saturates the CPU and network interface
  128  * with packet generation and sending. Set to zero to disable MINMSS
  129  * checking. This setting prevents us from sending too small packets.
  130  */
  131 int     tcp_minmss = TCP_MINMSS;
  132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, minmss, CTLFLAG_RW,
  133     &tcp_minmss , 0, "Minmum TCP Maximum Segment Size");
  134 
  135 int     tcp_do_rfc1323 = 1;
  136 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
  137     &tcp_do_rfc1323, 0, "Enable rfc1323 (high performance TCP) extensions");
  138 
  139 static int      tcp_log_debug = 0;
  140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
  141     &tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
  142 
  143 static int      tcp_tcbhashsize = 0;
  144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RDTUN,
  145     &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
  146 
  147 static int      do_tcpdrain = 1;
  148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW,
  149     &do_tcpdrain, 0,
  150     "Enable tcp_drain routine for extra help when low on mbufs");
  151 
  152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
  153     &tcbinfo.ipi_count, 0, "Number of active PCBs");
  154 
  155 static int      icmp_may_rst = 1;
  156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW,
  157     &icmp_may_rst, 0,
  158     "Certain ICMP unreachable messages may abort connections in SYN_SENT");
  159 
  160 static int      tcp_isn_reseed_interval = 0;
  161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW,
  162     &tcp_isn_reseed_interval, 0, "Seconds between reseeding of ISN secret");
  163 
  164 /*
  165  * TCP bandwidth limiting sysctls.  Note that the default lower bound of
  166  * 1024 exists only for debugging.  A good production default would be
  167  * something like 6100.
  168  */
  169 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, inflight, CTLFLAG_RW, 0,
  170     "TCP inflight data limiting");
  171 
  172 static int      tcp_inflight_enable = 1;
  173 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, enable, CTLFLAG_RW,
  174     &tcp_inflight_enable, 0, "Enable automatic TCP inflight data limiting");
  175 
  176 static int      tcp_inflight_debug = 0;
  177 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, debug, CTLFLAG_RW,
  178     &tcp_inflight_debug, 0, "Debug TCP inflight calculations");
  179 
  180 static int      tcp_inflight_rttthresh;
  181 SYSCTL_PROC(_net_inet_tcp_inflight, OID_AUTO, rttthresh, CTLTYPE_INT|CTLFLAG_RW,
  182     &tcp_inflight_rttthresh, 0, sysctl_msec_to_ticks, "I",
  183     "RTT threshold below which inflight will deactivate itself");
  184 
  185 static int      tcp_inflight_min = 6144;
  186 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, min, CTLFLAG_RW,
  187     &tcp_inflight_min, 0, "Lower-bound for TCP inflight window");
  188 
  189 static int      tcp_inflight_max = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  190 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, max, CTLFLAG_RW,
  191     &tcp_inflight_max, 0, "Upper-bound for TCP inflight window");
  192 
  193 static int      tcp_inflight_stab = 20;
  194 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, stab, CTLFLAG_RW,
  195     &tcp_inflight_stab, 0, "Inflight Algorithm Stabilization 20 = 2 packets");
  196 
  197 uma_zone_t sack_hole_zone;
  198 
  199 static struct inpcb *tcp_notify(struct inpcb *, int);
  200 static void     tcp_isn_tick(void *);
  201 
  202 /*
  203  * Target size of TCP PCB hash tables. Must be a power of two.
  204  *
  205  * Note that this can be overridden by the kernel environment
  206  * variable net.inet.tcp.tcbhashsize
  207  */
  208 #ifndef TCBHASHSIZE
  209 #define TCBHASHSIZE     512
  210 #endif
  211 
  212 /*
  213  * XXX
  214  * Callouts should be moved into struct tcp directly.  They are currently
  215  * separate because the tcpcb structure is exported to userland for sysctl
  216  * parsing purposes, which do not know about callouts.
  217  */
  218 struct tcpcb_mem {
  219         struct  tcpcb           tcb;
  220         struct  tcp_timer       tt;
  221 };
  222 
  223 static uma_zone_t tcpcb_zone;
  224 MALLOC_DEFINE(M_TCPLOG, "tcplog", "TCP address and flags print buffers");
  225 struct callout isn_callout;
  226 static struct mtx isn_mtx;
  227 
  228 #define ISN_LOCK_INIT() mtx_init(&isn_mtx, "isn_mtx", NULL, MTX_DEF)
  229 #define ISN_LOCK()      mtx_lock(&isn_mtx)
  230 #define ISN_UNLOCK()    mtx_unlock(&isn_mtx)
  231 
  232 /*
  233  * TCP initialization.
  234  */
  235 static void
  236 tcp_zone_change(void *tag)
  237 {
  238 
  239         uma_zone_set_max(tcbinfo.ipi_zone, maxsockets);
  240         uma_zone_set_max(tcpcb_zone, maxsockets);
  241         tcp_tw_zone_change();
  242 }
  243 
  244 static int
  245 tcp_inpcb_init(void *mem, int size, int flags)
  246 {
  247         struct inpcb *inp = mem;
  248 
  249         INP_LOCK_INIT(inp, "inp", "tcpinp");
  250         return (0);
  251 }
  252 
  253 void
  254 tcp_init(void)
  255 {
  256 
  257         int hashsize = TCBHASHSIZE;
  258         tcp_delacktime = TCPTV_DELACK;
  259         tcp_keepinit = TCPTV_KEEP_INIT;
  260         tcp_keepidle = TCPTV_KEEP_IDLE;
  261         tcp_keepintvl = TCPTV_KEEPINTVL;
  262         tcp_maxpersistidle = TCPTV_KEEP_IDLE;
  263         tcp_msl = TCPTV_MSL;
  264         tcp_rexmit_min = TCPTV_MIN;
  265         if (tcp_rexmit_min < 1)
  266                 tcp_rexmit_min = 1;
  267         tcp_rexmit_slop = TCPTV_CPU_VAR;
  268         tcp_inflight_rttthresh = TCPTV_INFLIGHT_RTTTHRESH;
  269         tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
  270 
  271         INP_INFO_LOCK_INIT(&tcbinfo, "tcp");
  272         LIST_INIT(&tcb);
  273         tcbinfo.ipi_listhead = &tcb;
  274         TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize);
  275         if (!powerof2(hashsize)) {
  276                 printf("WARNING: TCB hash size not a power of 2\n");
  277                 hashsize = 512; /* safe default */
  278         }
  279         tcp_tcbhashsize = hashsize;
  280         tcbinfo.ipi_hashbase = hashinit(hashsize, M_PCB,
  281             &tcbinfo.ipi_hashmask);
  282         tcbinfo.ipi_porthashbase = hashinit(hashsize, M_PCB,
  283             &tcbinfo.ipi_porthashmask);
  284         tcbinfo.ipi_zone = uma_zcreate("inpcb", sizeof(struct inpcb),
  285             NULL, NULL, tcp_inpcb_init, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  286         uma_zone_set_max(tcbinfo.ipi_zone, maxsockets);
  287 #ifdef INET6
  288 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
  289 #else /* INET6 */
  290 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
  291 #endif /* INET6 */
  292         if (max_protohdr < TCP_MINPROTOHDR)
  293                 max_protohdr = TCP_MINPROTOHDR;
  294         if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
  295                 panic("tcp_init");
  296 #undef TCP_MINPROTOHDR
  297         /*
  298          * These have to be type stable for the benefit of the timers.
  299          */
  300         tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
  301             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  302         uma_zone_set_max(tcpcb_zone, maxsockets);
  303         tcp_tw_init();
  304         syncache_init();
  305         tcp_hc_init();
  306         tcp_reass_init();
  307         ISN_LOCK_INIT();
  308         callout_init(&isn_callout, CALLOUT_MPSAFE);
  309         tcp_isn_tick(NULL);
  310         EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
  311                 SHUTDOWN_PRI_DEFAULT);
  312         sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
  313             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  314         EVENTHANDLER_REGISTER(maxsockets_change, tcp_zone_change, NULL,
  315                 EVENTHANDLER_PRI_ANY);
  316 }
  317 
  318 void
  319 tcp_fini(void *xtp)
  320 {
  321 
  322         callout_stop(&isn_callout);
  323 }
  324 
  325 /*
  326  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
  327  * tcp_template used to store this data in mbufs, but we now recopy it out
  328  * of the tcpcb each time to conserve mbufs.
  329  */
  330 void
  331 tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
  332 {
  333         struct tcphdr *th = (struct tcphdr *)tcp_ptr;
  334 
  335         INP_WLOCK_ASSERT(inp);
  336 
  337 #ifdef INET6
  338         if ((inp->inp_vflag & INP_IPV6) != 0) {
  339                 struct ip6_hdr *ip6;
  340 
  341                 ip6 = (struct ip6_hdr *)ip_ptr;
  342                 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
  343                         (inp->in6p_flowinfo & IPV6_FLOWINFO_MASK);
  344                 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
  345                         (IPV6_VERSION & IPV6_VERSION_MASK);
  346                 ip6->ip6_nxt = IPPROTO_TCP;
  347                 ip6->ip6_plen = htons(sizeof(struct tcphdr));
  348                 ip6->ip6_src = inp->in6p_laddr;
  349                 ip6->ip6_dst = inp->in6p_faddr;
  350         } else
  351 #endif
  352         {
  353                 struct ip *ip;
  354 
  355                 ip = (struct ip *)ip_ptr;
  356                 ip->ip_v = IPVERSION;
  357                 ip->ip_hl = 5;
  358                 ip->ip_tos = inp->inp_ip_tos;
  359                 ip->ip_len = 0;
  360                 ip->ip_id = 0;
  361                 ip->ip_off = 0;
  362                 ip->ip_ttl = inp->inp_ip_ttl;
  363                 ip->ip_sum = 0;
  364                 ip->ip_p = IPPROTO_TCP;
  365                 ip->ip_src = inp->inp_laddr;
  366                 ip->ip_dst = inp->inp_faddr;
  367         }
  368         th->th_sport = inp->inp_lport;
  369         th->th_dport = inp->inp_fport;
  370         th->th_seq = 0;
  371         th->th_ack = 0;
  372         th->th_x2 = 0;
  373         th->th_off = 5;
  374         th->th_flags = 0;
  375         th->th_win = 0;
  376         th->th_urp = 0;
  377         th->th_sum = 0;         /* in_pseudo() is called later for ipv4 */
  378 }
  379 
  380 /*
  381  * Create template to be used to send tcp packets on a connection.
  382  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
  383  * use for this function is in keepalives, which use tcp_respond.
  384  */
  385 struct tcptemp *
  386 tcpip_maketemplate(struct inpcb *inp)
  387 {
  388         struct tcptemp *t;
  389 
  390         t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
  391         if (t == NULL)
  392                 return (NULL);
  393         tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
  394         return (t);
  395 }
  396 
  397 /*
  398  * Send a single message to the TCP at address specified by
  399  * the given TCP/IP header.  If m == NULL, then we make a copy
  400  * of the tcpiphdr at ti and send directly to the addressed host.
  401  * This is used to force keep alive messages out using the TCP
  402  * template for a connection.  If flags are given then we send
  403  * a message back to the TCP which originated the * segment ti,
  404  * and discard the mbuf containing it and any other attached mbufs.
  405  *
  406  * In any case the ack and sequence number of the transmitted
  407  * segment are as specified by the parameters.
  408  *
  409  * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
  410  */
  411 void
  412 tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
  413     tcp_seq ack, tcp_seq seq, int flags)
  414 {
  415         int tlen;
  416         int win = 0;
  417         struct ip *ip;
  418         struct tcphdr *nth;
  419 #ifdef INET6
  420         struct ip6_hdr *ip6;
  421         int isipv6;
  422 #endif /* INET6 */
  423         int ipflags = 0;
  424         struct inpcb *inp;
  425 
  426         KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
  427 
  428 #ifdef INET6
  429         isipv6 = ((struct ip *)ipgen)->ip_v == 6;
  430         ip6 = ipgen;
  431 #endif /* INET6 */
  432         ip = ipgen;
  433 
  434         if (tp != NULL) {
  435                 inp = tp->t_inpcb;
  436                 KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
  437                 INP_WLOCK_ASSERT(inp);
  438         } else
  439                 inp = NULL;
  440 
  441         if (tp != NULL) {
  442                 if (!(flags & TH_RST)) {
  443                         win = sbspace(&inp->inp_socket->so_rcv);
  444                         if (win > (long)TCP_MAXWIN << tp->rcv_scale)
  445                                 win = (long)TCP_MAXWIN << tp->rcv_scale;
  446                 }
  447         }
  448         if (m == NULL) {
  449                 m = m_gethdr(M_DONTWAIT, MT_DATA);
  450                 if (m == NULL)
  451                         return;
  452                 tlen = 0;
  453                 m->m_data += max_linkhdr;
  454 #ifdef INET6
  455                 if (isipv6) {
  456                         bcopy((caddr_t)ip6, mtod(m, caddr_t),
  457                               sizeof(struct ip6_hdr));
  458                         ip6 = mtod(m, struct ip6_hdr *);
  459                         nth = (struct tcphdr *)(ip6 + 1);
  460                 } else
  461 #endif /* INET6 */
  462               {
  463                 bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
  464                 ip = mtod(m, struct ip *);
  465                 nth = (struct tcphdr *)(ip + 1);
  466               }
  467                 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
  468                 flags = TH_ACK;
  469         } else {
  470                 /*
  471                  *  reuse the mbuf. 
  472                  * XXX MRT We inherrit the FIB, which is lucky.
  473                  */
  474                 m_freem(m->m_next);
  475                 m->m_next = NULL;
  476                 m->m_data = (caddr_t)ipgen;
  477                 /* m_len is set later */
  478                 tlen = 0;
  479 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
  480 #ifdef INET6
  481                 if (isipv6) {
  482                         xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
  483                         nth = (struct tcphdr *)(ip6 + 1);
  484                 } else
  485 #endif /* INET6 */
  486               {
  487                 xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long);
  488                 nth = (struct tcphdr *)(ip + 1);
  489               }
  490                 if (th != nth) {
  491                         /*
  492                          * this is usually a case when an extension header
  493                          * exists between the IPv6 header and the
  494                          * TCP header.
  495                          */
  496                         nth->th_sport = th->th_sport;
  497                         nth->th_dport = th->th_dport;
  498                 }
  499                 xchg(nth->th_dport, nth->th_sport, n_short);
  500 #undef xchg
  501         }
  502 #ifdef INET6
  503         if (isipv6) {
  504                 ip6->ip6_flow = 0;
  505                 ip6->ip6_vfc = IPV6_VERSION;
  506                 ip6->ip6_nxt = IPPROTO_TCP;
  507                 ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) +
  508                                                 tlen));
  509                 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
  510         } else
  511 #endif
  512         {
  513                 tlen += sizeof (struct tcpiphdr);
  514                 ip->ip_len = tlen;
  515                 ip->ip_ttl = ip_defttl;
  516                 if (path_mtu_discovery)
  517                         ip->ip_off |= IP_DF;
  518         }
  519         m->m_len = tlen;
  520         m->m_pkthdr.len = tlen;
  521         m->m_pkthdr.rcvif = NULL;
  522 #ifdef MAC
  523         if (inp != NULL) {
  524                 /*
  525                  * Packet is associated with a socket, so allow the
  526                  * label of the response to reflect the socket label.
  527                  */
  528                 INP_WLOCK_ASSERT(inp);
  529                 mac_create_mbuf_from_inpcb(inp, m);
  530         } else {
  531                 /*
  532                  * Packet is not associated with a socket, so possibly
  533                  * update the label in place.
  534                  */
  535                 mac_reflect_mbuf_tcp(m);
  536         }
  537 #endif
  538         nth->th_seq = htonl(seq);
  539         nth->th_ack = htonl(ack);
  540         nth->th_x2 = 0;
  541         nth->th_off = sizeof (struct tcphdr) >> 2;
  542         nth->th_flags = flags;
  543         if (tp != NULL)
  544                 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
  545         else
  546                 nth->th_win = htons((u_short)win);
  547         nth->th_urp = 0;
  548 #ifdef INET6
  549         if (isipv6) {
  550                 nth->th_sum = 0;
  551                 nth->th_sum = in6_cksum(m, IPPROTO_TCP,
  552                                         sizeof(struct ip6_hdr),
  553                                         tlen - sizeof(struct ip6_hdr));
  554                 ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
  555                     NULL, NULL);
  556         } else
  557 #endif /* INET6 */
  558         {
  559                 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
  560                     htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
  561                 m->m_pkthdr.csum_flags = CSUM_TCP;
  562                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
  563         }
  564 #ifdef TCPDEBUG
  565         if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
  566                 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
  567 #endif
  568 #ifdef INET6
  569         if (isipv6)
  570                 (void) ip6_output(m, NULL, NULL, ipflags, NULL, NULL, inp);
  571         else
  572 #endif /* INET6 */
  573         (void) ip_output(m, NULL, NULL, ipflags, NULL, inp);
  574 }
  575 
  576 /*
  577  * Create a new TCP control block, making an
  578  * empty reassembly queue and hooking it to the argument
  579  * protocol control block.  The `inp' parameter must have
  580  * come from the zone allocator set up in tcp_init().
  581  */
  582 struct tcpcb *
  583 tcp_newtcpcb(struct inpcb *inp)
  584 {
  585         struct tcpcb_mem *tm;
  586         struct tcpcb *tp;
  587 #ifdef INET6
  588         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  589 #endif /* INET6 */
  590 
  591         tm = uma_zalloc(tcpcb_zone, M_NOWAIT | M_ZERO);
  592         if (tm == NULL)
  593                 return (NULL);
  594         tp = &tm->tcb;
  595         tp->t_timers = &tm->tt;
  596         /*      LIST_INIT(&tp->t_segq); */      /* XXX covered by M_ZERO */
  597         tp->t_maxseg = tp->t_maxopd =
  598 #ifdef INET6
  599                 isipv6 ? tcp_v6mssdflt :
  600 #endif /* INET6 */
  601                 tcp_mssdflt;
  602 
  603         /* Set up our timeouts. */
  604         callout_init(&tp->t_timers->tt_rexmt, CALLOUT_MPSAFE);
  605         callout_init(&tp->t_timers->tt_persist, CALLOUT_MPSAFE);
  606         callout_init(&tp->t_timers->tt_keep, CALLOUT_MPSAFE);
  607         callout_init(&tp->t_timers->tt_2msl, CALLOUT_MPSAFE);
  608         callout_init(&tp->t_timers->tt_delack, CALLOUT_MPSAFE);
  609 
  610         if (tcp_do_rfc1323)
  611                 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
  612         if (tcp_do_sack)
  613                 tp->t_flags |= TF_SACK_PERMIT;
  614         TAILQ_INIT(&tp->snd_holes);
  615         tp->t_inpcb = inp;      /* XXX */
  616         /*
  617          * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
  618          * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
  619          * reasonable initial retransmit time.
  620          */
  621         tp->t_srtt = TCPTV_SRTTBASE;
  622         tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
  623         tp->t_rttmin = tcp_rexmit_min;
  624         tp->t_rxtcur = TCPTV_RTOBASE;
  625         tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  626         tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  627         tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  628         tp->t_rcvtime = ticks;
  629         tp->t_bw_rtttime = ticks;
  630         /*
  631          * IPv4 TTL initialization is necessary for an IPv6 socket as well,
  632          * because the socket may be bound to an IPv6 wildcard address,
  633          * which may match an IPv4-mapped IPv6 address.
  634          */
  635         inp->inp_ip_ttl = ip_defttl;
  636         inp->inp_ppcb = tp;
  637         return (tp);            /* XXX */
  638 }
  639 
  640 /*
  641  * Drop a TCP connection, reporting
  642  * the specified error.  If connection is synchronized,
  643  * then send a RST to peer.
  644  */
  645 struct tcpcb *
  646 tcp_drop(struct tcpcb *tp, int errno)
  647 {
  648         struct socket *so = tp->t_inpcb->inp_socket;
  649 
  650         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  651         INP_WLOCK_ASSERT(tp->t_inpcb);
  652 
  653         if (TCPS_HAVERCVDSYN(tp->t_state)) {
  654                 tp->t_state = TCPS_CLOSED;
  655                 (void) tcp_output_reset(tp);
  656                 tcpstat.tcps_drops++;
  657         } else
  658                 tcpstat.tcps_conndrops++;
  659         if (errno == ETIMEDOUT && tp->t_softerror)
  660                 errno = tp->t_softerror;
  661         so->so_error = errno;
  662         return (tcp_close(tp));
  663 }
  664 
  665 void
  666 tcp_discardcb(struct tcpcb *tp)
  667 {
  668         struct tseg_qent *q;
  669         struct inpcb *inp = tp->t_inpcb;
  670         struct socket *so = inp->inp_socket;
  671 #ifdef INET6
  672         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  673 #endif /* INET6 */
  674 
  675         INP_WLOCK_ASSERT(inp);
  676 
  677         /*
  678          * Make sure that all of our timers are stopped before we
  679          * delete the PCB.
  680          */
  681         callout_stop(&tp->t_timers->tt_rexmt);
  682         callout_stop(&tp->t_timers->tt_persist);
  683         callout_stop(&tp->t_timers->tt_keep);
  684         callout_stop(&tp->t_timers->tt_2msl);
  685         callout_stop(&tp->t_timers->tt_delack);
  686 
  687         /*
  688          * If we got enough samples through the srtt filter,
  689          * save the rtt and rttvar in the routing entry.
  690          * 'Enough' is arbitrarily defined as 4 rtt samples.
  691          * 4 samples is enough for the srtt filter to converge
  692          * to within enough % of the correct value; fewer samples
  693          * and we could save a bogus rtt. The danger is not high
  694          * as tcp quickly recovers from everything.
  695          * XXX: Works very well but needs some more statistics!
  696          */
  697         if (tp->t_rttupdated >= 4) {
  698                 struct hc_metrics_lite metrics;
  699                 u_long ssthresh;
  700 
  701                 bzero(&metrics, sizeof(metrics));
  702                 /*
  703                  * Update the ssthresh always when the conditions below
  704                  * are satisfied. This gives us better new start value
  705                  * for the congestion avoidance for new connections.
  706                  * ssthresh is only set if packet loss occured on a session.
  707                  *
  708                  * XXXRW: 'so' may be NULL here, and/or socket buffer may be
  709                  * being torn down.  Ideally this code would not use 'so'.
  710                  */
  711                 ssthresh = tp->snd_ssthresh;
  712                 if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
  713                         /*
  714                          * convert the limit from user data bytes to
  715                          * packets then to packet data bytes.
  716                          */
  717                         ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
  718                         if (ssthresh < 2)
  719                                 ssthresh = 2;
  720                         ssthresh *= (u_long)(tp->t_maxseg +
  721 #ifdef INET6
  722                                       (isipv6 ? sizeof (struct ip6_hdr) +
  723                                                sizeof (struct tcphdr) :
  724 #endif
  725                                        sizeof (struct tcpiphdr)
  726 #ifdef INET6
  727                                        )
  728 #endif
  729                                       );
  730                 } else
  731                         ssthresh = 0;
  732                 metrics.rmx_ssthresh = ssthresh;
  733 
  734                 metrics.rmx_rtt = tp->t_srtt;
  735                 metrics.rmx_rttvar = tp->t_rttvar;
  736                 /* XXX: This wraps if the pipe is more than 4 Gbit per second */
  737                 metrics.rmx_bandwidth = tp->snd_bandwidth;
  738                 metrics.rmx_cwnd = tp->snd_cwnd;
  739                 metrics.rmx_sendpipe = 0;
  740                 metrics.rmx_recvpipe = 0;
  741 
  742                 tcp_hc_update(&inp->inp_inc, &metrics);
  743         }
  744 
  745         /* free the reassembly queue, if any */
  746         while ((q = LIST_FIRST(&tp->t_segq)) != NULL) {
  747                 LIST_REMOVE(q, tqe_q);
  748                 m_freem(q->tqe_m);
  749                 uma_zfree(tcp_reass_zone, q);
  750                 tp->t_segqlen--;
  751                 tcp_reass_qsize--;
  752         }
  753         /* Disconnect offload device, if any. */
  754         tcp_offload_detach(tp);
  755                 
  756         tcp_free_sackholes(tp);
  757         inp->inp_ppcb = NULL;
  758         tp->t_inpcb = NULL;
  759         uma_zfree(tcpcb_zone, tp);
  760 }
  761 
  762 /*
  763  * Attempt to close a TCP control block, marking it as dropped, and freeing
  764  * the socket if we hold the only reference.
  765  */
  766 struct tcpcb *
  767 tcp_close(struct tcpcb *tp)
  768 {
  769         struct inpcb *inp = tp->t_inpcb;
  770         struct socket *so;
  771 
  772         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  773         INP_WLOCK_ASSERT(inp);
  774 
  775         /* Notify any offload devices of listener close */
  776         if (tp->t_state == TCPS_LISTEN)
  777                 tcp_offload_listen_close(tp);
  778         in_pcbdrop(inp);
  779         tcpstat.tcps_closed++;
  780         KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
  781         so = inp->inp_socket;
  782         soisdisconnected(so);
  783         if (inp->inp_vflag & INP_SOCKREF) {
  784                 KASSERT(so->so_state & SS_PROTOREF,
  785                     ("tcp_close: !SS_PROTOREF"));
  786                 inp->inp_vflag &= ~INP_SOCKREF;
  787                 INP_WUNLOCK(inp);
  788                 ACCEPT_LOCK();
  789                 SOCK_LOCK(so);
  790                 so->so_state &= ~SS_PROTOREF;
  791                 sofree(so);
  792                 return (NULL);
  793         }
  794         return (tp);
  795 }
  796 
  797 void
  798 tcp_drain(void)
  799 {
  800 
  801         if (do_tcpdrain) {
  802                 struct inpcb *inpb;
  803                 struct tcpcb *tcpb;
  804                 struct tseg_qent *te;
  805 
  806         /*
  807          * Walk the tcpbs, if existing, and flush the reassembly queue,
  808          * if there is one...
  809          * XXX: The "Net/3" implementation doesn't imply that the TCP
  810          *      reassembly queue should be flushed, but in a situation
  811          *      where we're really low on mbufs, this is potentially
  812          *      usefull.
  813          */
  814                 INP_INFO_RLOCK(&tcbinfo);
  815                 LIST_FOREACH(inpb, tcbinfo.ipi_listhead, inp_list) {
  816                         if (inpb->inp_vflag & INP_TIMEWAIT)
  817                                 continue;
  818                         INP_WLOCK(inpb);
  819                         if ((tcpb = intotcpcb(inpb)) != NULL) {
  820                                 while ((te = LIST_FIRST(&tcpb->t_segq))
  821                                     != NULL) {
  822                                         LIST_REMOVE(te, tqe_q);
  823                                         m_freem(te->tqe_m);
  824                                         uma_zfree(tcp_reass_zone, te);
  825                                         tcpb->t_segqlen--;
  826                                         tcp_reass_qsize--;
  827                                 }
  828                                 tcp_clean_sackreport(tcpb);
  829                         }
  830                         INP_WUNLOCK(inpb);
  831                 }
  832                 INP_INFO_RUNLOCK(&tcbinfo);
  833         }
  834 }
  835 
  836 /*
  837  * Notify a tcp user of an asynchronous error;
  838  * store error as soft error, but wake up user
  839  * (for now, won't do anything until can select for soft error).
  840  *
  841  * Do not wake up user since there currently is no mechanism for
  842  * reporting soft errors (yet - a kqueue filter may be added).
  843  */
  844 static struct inpcb *
  845 tcp_notify(struct inpcb *inp, int error)
  846 {
  847         struct tcpcb *tp;
  848 
  849         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  850         INP_WLOCK_ASSERT(inp);
  851 
  852         if ((inp->inp_vflag & INP_TIMEWAIT) ||
  853             (inp->inp_vflag & INP_DROPPED))
  854                 return (inp);
  855 
  856         tp = intotcpcb(inp);
  857         KASSERT(tp != NULL, ("tcp_notify: tp == NULL"));
  858 
  859         /*
  860          * Ignore some errors if we are hooked up.
  861          * If connection hasn't completed, has retransmitted several times,
  862          * and receives a second error, give up now.  This is better
  863          * than waiting a long time to establish a connection that
  864          * can never complete.
  865          */
  866         if (tp->t_state == TCPS_ESTABLISHED &&
  867             (error == EHOSTUNREACH || error == ENETUNREACH ||
  868              error == EHOSTDOWN)) {
  869                 return (inp);
  870         } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
  871             tp->t_softerror) {
  872                 tp = tcp_drop(tp, error);
  873                 if (tp != NULL)
  874                         return (inp);
  875                 else
  876                         return (NULL);
  877         } else {
  878                 tp->t_softerror = error;
  879                 return (inp);
  880         }
  881 #if 0
  882         wakeup( &so->so_timeo);
  883         sorwakeup(so);
  884         sowwakeup(so);
  885 #endif
  886 }
  887 
  888 static int
  889 tcp_pcblist(SYSCTL_HANDLER_ARGS)
  890 {
  891         int error, i, m, n, pcb_count;
  892         struct inpcb *inp, **inp_list;
  893         inp_gen_t gencnt;
  894         struct xinpgen xig;
  895 
  896         /*
  897          * The process of preparing the TCB list is too time-consuming and
  898          * resource-intensive to repeat twice on every request.
  899          */
  900         if (req->oldptr == NULL) {
  901                 m = syncache_pcbcount();
  902                 n = tcbinfo.ipi_count;
  903                 req->oldidx = 2 * (sizeof xig)
  904                         + ((m + n) + n/8) * sizeof(struct xtcpcb);
  905                 return (0);
  906         }
  907 
  908         if (req->newptr != NULL)
  909                 return (EPERM);
  910 
  911         /*
  912          * OK, now we're committed to doing something.
  913          */
  914         INP_INFO_RLOCK(&tcbinfo);
  915         gencnt = tcbinfo.ipi_gencnt;
  916         n = tcbinfo.ipi_count;
  917         INP_INFO_RUNLOCK(&tcbinfo);
  918 
  919         m = syncache_pcbcount();
  920 
  921         error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
  922                 + (n + m) * sizeof(struct xtcpcb));
  923         if (error != 0)
  924                 return (error);
  925 
  926         xig.xig_len = sizeof xig;
  927         xig.xig_count = n + m;
  928         xig.xig_gen = gencnt;
  929         xig.xig_sogen = so_gencnt;
  930         error = SYSCTL_OUT(req, &xig, sizeof xig);
  931         if (error)
  932                 return (error);
  933 
  934         error = syncache_pcblist(req, m, &pcb_count);
  935         if (error)
  936                 return (error);
  937 
  938         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
  939         if (inp_list == NULL)
  940                 return (ENOMEM);
  941 
  942         INP_INFO_RLOCK(&tcbinfo);
  943         for (inp = LIST_FIRST(tcbinfo.ipi_listhead), i = 0; inp != NULL && i
  944             < n; inp = LIST_NEXT(inp, inp_list)) {
  945                 INP_RLOCK(inp);
  946                 if (inp->inp_gencnt <= gencnt) {
  947                         /*
  948                          * XXX: This use of cr_cansee(), introduced with
  949                          * TCP state changes, is not quite right, but for
  950                          * now, better than nothing.
  951                          */
  952                         if (inp->inp_vflag & INP_TIMEWAIT) {
  953                                 if (intotw(inp) != NULL)
  954                                         error = cr_cansee(req->td->td_ucred,
  955                                             intotw(inp)->tw_cred);
  956                                 else
  957                                         error = EINVAL; /* Skip this inp. */
  958                         } else
  959                                 error = cr_canseeinpcb(req->td->td_ucred, inp);
  960                         if (error == 0)
  961                                 inp_list[i++] = inp;
  962                 }
  963                 INP_RUNLOCK(inp);
  964         }
  965         INP_INFO_RUNLOCK(&tcbinfo);
  966         n = i;
  967 
  968         error = 0;
  969         for (i = 0; i < n; i++) {
  970                 inp = inp_list[i];
  971                 INP_RLOCK(inp);
  972                 if (inp->inp_gencnt <= gencnt) {
  973                         struct xtcpcb xt;
  974                         void *inp_ppcb;
  975 
  976                         bzero(&xt, sizeof(xt));
  977                         xt.xt_len = sizeof xt;
  978                         /* XXX should avoid extra copy */
  979                         bcopy(inp, &xt.xt_inp, sizeof *inp);
  980                         inp_ppcb = inp->inp_ppcb;
  981                         if (inp_ppcb == NULL)
  982                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
  983                         else if (inp->inp_vflag & INP_TIMEWAIT) {
  984                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
  985                                 xt.xt_tp.t_state = TCPS_TIME_WAIT;
  986                         } else
  987                                 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
  988                         if (inp->inp_socket != NULL)
  989                                 sotoxsocket(inp->inp_socket, &xt.xt_socket);
  990                         else {
  991                                 bzero(&xt.xt_socket, sizeof xt.xt_socket);
  992                                 xt.xt_socket.xso_protocol = IPPROTO_TCP;
  993                         }
  994                         xt.xt_inp.inp_gencnt = inp->inp_gencnt;
  995                         INP_RUNLOCK(inp);
  996                         error = SYSCTL_OUT(req, &xt, sizeof xt);
  997                 } else
  998                         INP_RUNLOCK(inp);
  999         
 1000         }
 1001         if (!error) {
 1002                 /*
 1003                  * Give the user an updated idea of our state.
 1004                  * If the generation differs from what we told
 1005                  * her before, she knows that something happened
 1006                  * while we were processing this request, and it
 1007                  * might be necessary to retry.
 1008                  */
 1009                 INP_INFO_RLOCK(&tcbinfo);
 1010                 xig.xig_gen = tcbinfo.ipi_gencnt;
 1011                 xig.xig_sogen = so_gencnt;
 1012                 xig.xig_count = tcbinfo.ipi_count + pcb_count;
 1013                 INP_INFO_RUNLOCK(&tcbinfo);
 1014                 error = SYSCTL_OUT(req, &xig, sizeof xig);
 1015         }
 1016         free(inp_list, M_TEMP);
 1017         return (error);
 1018 }
 1019 
 1020 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
 1021     tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
 1022 
 1023 static int
 1024 tcp_getcred(SYSCTL_HANDLER_ARGS)
 1025 {
 1026         struct xucred xuc;
 1027         struct sockaddr_in addrs[2];
 1028         struct inpcb *inp;
 1029         int error;
 1030 
 1031         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1032         if (error)
 1033                 return (error);
 1034         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1035         if (error)
 1036                 return (error);
 1037         INP_INFO_RLOCK(&tcbinfo);
 1038         inp = in_pcblookup_hash(&tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
 1039             addrs[0].sin_addr, addrs[0].sin_port, 0, NULL);
 1040         if (inp != NULL) {
 1041                 INP_RLOCK(inp);
 1042                 INP_INFO_RUNLOCK(&tcbinfo);
 1043                 if (inp->inp_socket == NULL)
 1044                         error = ENOENT;
 1045                 if (error == 0)
 1046                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1047                 if (error == 0)
 1048                         cru2x(inp->inp_cred, &xuc);
 1049                 INP_RUNLOCK(inp);
 1050         } else {
 1051                 INP_INFO_RUNLOCK(&tcbinfo);
 1052                 error = ENOENT;
 1053         }
 1054         if (error == 0)
 1055                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1056         return (error);
 1057 }
 1058 
 1059 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
 1060     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1061     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
 1062 
 1063 #ifdef INET6
 1064 static int
 1065 tcp6_getcred(SYSCTL_HANDLER_ARGS)
 1066 {
 1067         struct xucred xuc;
 1068         struct sockaddr_in6 addrs[2];
 1069         struct inpcb *inp;
 1070         int error, mapped = 0;
 1071 
 1072         error = priv_check(req->td, PRIV_NETINET_GETCRED);
 1073         if (error)
 1074                 return (error);
 1075         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1076         if (error)
 1077                 return (error);
 1078         if ((error = sa6_embedscope(&addrs[0], ip6_use_defzone)) != 0 ||
 1079             (error = sa6_embedscope(&addrs[1], ip6_use_defzone)) != 0) {
 1080                 return (error);
 1081         }
 1082         if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
 1083                 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
 1084                         mapped = 1;
 1085                 else
 1086                         return (EINVAL);
 1087         }
 1088 
 1089         INP_INFO_RLOCK(&tcbinfo);
 1090         if (mapped == 1)
 1091                 inp = in_pcblookup_hash(&tcbinfo,
 1092                         *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
 1093                         addrs[1].sin6_port,
 1094                         *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
 1095                         addrs[0].sin6_port,
 1096                         0, NULL);
 1097         else
 1098                 inp = in6_pcblookup_hash(&tcbinfo,
 1099                         &addrs[1].sin6_addr, addrs[1].sin6_port,
 1100                         &addrs[0].sin6_addr, addrs[0].sin6_port, 0, NULL);
 1101         if (inp != NULL) {
 1102                 INP_RLOCK(inp);
 1103                 INP_INFO_RUNLOCK(&tcbinfo);
 1104                 if (inp->inp_socket == NULL)
 1105                         error = ENOENT;
 1106                 if (error == 0)
 1107                         error = cr_canseeinpcb(req->td->td_ucred, inp);
 1108                 if (error == 0)
 1109                         cru2x(inp->inp_cred, &xuc);
 1110                 INP_RUNLOCK(inp);
 1111         } else {
 1112                 INP_INFO_RUNLOCK(&tcbinfo);
 1113                 error = ENOENT;
 1114         }
 1115         if (error == 0)
 1116                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1117         return (error);
 1118 }
 1119 
 1120 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 1121     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1122     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
 1123 #endif
 1124 
 1125 
 1126 void
 1127 tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
 1128 {
 1129         struct ip *ip = vip;
 1130         struct tcphdr *th;
 1131         struct in_addr faddr;
 1132         struct inpcb *inp;
 1133         struct tcpcb *tp;
 1134         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1135         struct icmp *icp;
 1136         struct in_conninfo inc;
 1137         tcp_seq icmp_tcp_seq;
 1138         int mtu;
 1139 
 1140         faddr = ((struct sockaddr_in *)sa)->sin_addr;
 1141         if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
 1142                 return;
 1143 
 1144         if (cmd == PRC_MSGSIZE)
 1145                 notify = tcp_mtudisc;
 1146         else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
 1147                 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
 1148                 notify = tcp_drop_syn_sent;
 1149         /*
 1150          * Redirects don't need to be handled up here.
 1151          */
 1152         else if (PRC_IS_REDIRECT(cmd))
 1153                 return;
 1154         /*
 1155          * Source quench is depreciated.
 1156          */
 1157         else if (cmd == PRC_QUENCH)
 1158                 return;
 1159         /*
 1160          * Hostdead is ugly because it goes linearly through all PCBs.
 1161          * XXX: We never get this from ICMP, otherwise it makes an
 1162          * excellent DoS attack on machines with many connections.
 1163          */
 1164         else if (cmd == PRC_HOSTDEAD)
 1165                 ip = NULL;
 1166         else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
 1167                 return;
 1168         if (ip != NULL) {
 1169                 icp = (struct icmp *)((caddr_t)ip
 1170                                       - offsetof(struct icmp, icmp_ip));
 1171                 th = (struct tcphdr *)((caddr_t)ip
 1172                                        + (ip->ip_hl << 2));
 1173                 INP_INFO_WLOCK(&tcbinfo);
 1174                 inp = in_pcblookup_hash(&tcbinfo, faddr, th->th_dport,
 1175                     ip->ip_src, th->th_sport, 0, NULL);
 1176                 if (inp != NULL)  {
 1177                         INP_WLOCK(inp);
 1178                         if (!(inp->inp_vflag & INP_TIMEWAIT) &&
 1179                             !(inp->inp_vflag & INP_DROPPED) &&
 1180                             !(inp->inp_socket == NULL)) {
 1181                                 icmp_tcp_seq = htonl(th->th_seq);
 1182                                 tp = intotcpcb(inp);
 1183                                 if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
 1184                                     SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
 1185                                         if (cmd == PRC_MSGSIZE) {
 1186                                             /*
 1187                                              * MTU discovery:
 1188                                              * If we got a needfrag set the MTU
 1189                                              * in the route to the suggested new
 1190                                              * value (if given) and then notify.
 1191                                              */
 1192                                             bzero(&inc, sizeof(inc));
 1193                                             inc.inc_flags = 0;  /* IPv4 */
 1194                                             inc.inc_faddr = faddr;
 1195                                             inc.inc_fibnum =
 1196                                                 inp->inp_inc.inc_fibnum;
 1197 
 1198                                             mtu = ntohs(icp->icmp_nextmtu);
 1199                                             /*
 1200                                              * If no alternative MTU was
 1201                                              * proposed, try the next smaller
 1202                                              * one.  ip->ip_len has already
 1203                                              * been swapped in icmp_input().
 1204                                              */
 1205                                             if (!mtu)
 1206                                                 mtu = ip_next_mtu(ip->ip_len,
 1207                                                  1);
 1208                                             if (mtu < max(296, (tcp_minmss)
 1209                                                  + sizeof(struct tcpiphdr)))
 1210                                                 mtu = 0;
 1211                                             if (!mtu)
 1212                                                 mtu = tcp_mssdflt
 1213                                                  + sizeof(struct tcpiphdr);
 1214                                             /*
 1215                                              * Only cache the the MTU if it
 1216                                              * is smaller than the interface
 1217                                              * or route MTU.  tcp_mtudisc()
 1218                                              * will do right thing by itself.
 1219                                              */
 1220                                             if (mtu <= tcp_maxmtu(&inc, NULL))
 1221                                                 tcp_hc_updatemtu(&inc, mtu);
 1222                                         }
 1223 
 1224                                         inp = (*notify)(inp, inetctlerrmap[cmd]);
 1225                                 }
 1226                         }
 1227                         if (inp != NULL)
 1228                                 INP_WUNLOCK(inp);
 1229                 } else {
 1230                         inc.inc_fport = th->th_dport;
 1231                         inc.inc_lport = th->th_sport;
 1232                         inc.inc_faddr = faddr;
 1233                         inc.inc_laddr = ip->ip_src;
 1234 #ifdef INET6
 1235                         inc.inc_isipv6 = 0;
 1236 #endif
 1237                         syncache_unreach(&inc, th);
 1238                 }
 1239                 INP_INFO_WUNLOCK(&tcbinfo);
 1240         } else
 1241                 in_pcbnotifyall(&tcbinfo, faddr, inetctlerrmap[cmd], notify);
 1242 }
 1243 
 1244 #ifdef INET6
 1245 void
 1246 tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
 1247 {
 1248         struct tcphdr th;
 1249         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1250         struct ip6_hdr *ip6;
 1251         struct mbuf *m;
 1252         struct ip6ctlparam *ip6cp = NULL;
 1253         const struct sockaddr_in6 *sa6_src = NULL;
 1254         int off;
 1255         struct tcp_portonly {
 1256                 u_int16_t th_sport;
 1257                 u_int16_t th_dport;
 1258         } *thp;
 1259 
 1260         if (sa->sa_family != AF_INET6 ||
 1261             sa->sa_len != sizeof(struct sockaddr_in6))
 1262                 return;
 1263 
 1264         if (cmd == PRC_MSGSIZE)
 1265                 notify = tcp_mtudisc;
 1266         else if (!PRC_IS_REDIRECT(cmd) &&
 1267                  ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
 1268                 return;
 1269         /* Source quench is depreciated. */
 1270         else if (cmd == PRC_QUENCH)
 1271                 return;
 1272 
 1273         /* if the parameter is from icmp6, decode it. */
 1274         if (d != NULL) {
 1275                 ip6cp = (struct ip6ctlparam *)d;
 1276                 m = ip6cp->ip6c_m;
 1277                 ip6 = ip6cp->ip6c_ip6;
 1278                 off = ip6cp->ip6c_off;
 1279                 sa6_src = ip6cp->ip6c_src;
 1280         } else {
 1281                 m = NULL;
 1282                 ip6 = NULL;
 1283                 off = 0;        /* fool gcc */
 1284                 sa6_src = &sa6_any;
 1285         }
 1286 
 1287         if (ip6 != NULL) {
 1288                 struct in_conninfo inc;
 1289                 /*
 1290                  * XXX: We assume that when IPV6 is non NULL,
 1291                  * M and OFF are valid.
 1292                  */
 1293 
 1294                 /* check if we can safely examine src and dst ports */
 1295                 if (m->m_pkthdr.len < off + sizeof(*thp))
 1296                         return;
 1297 
 1298                 bzero(&th, sizeof(th));
 1299                 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
 1300 
 1301                 in6_pcbnotify(&tcbinfo, sa, th.th_dport,
 1302                     (struct sockaddr *)ip6cp->ip6c_src,
 1303                     th.th_sport, cmd, NULL, notify);
 1304 
 1305                 inc.inc_fport = th.th_dport;
 1306                 inc.inc_lport = th.th_sport;
 1307                 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
 1308                 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
 1309                 inc.inc_isipv6 = 1;
 1310                 INP_INFO_WLOCK(&tcbinfo);
 1311                 syncache_unreach(&inc, &th);
 1312                 INP_INFO_WUNLOCK(&tcbinfo);
 1313         } else
 1314                 in6_pcbnotify(&tcbinfo, sa, 0, (const struct sockaddr *)sa6_src,
 1315                               0, cmd, NULL, notify);
 1316 }
 1317 #endif /* INET6 */
 1318 
 1319 
 1320 /*
 1321  * Following is where TCP initial sequence number generation occurs.
 1322  *
 1323  * There are two places where we must use initial sequence numbers:
 1324  * 1.  In SYN-ACK packets.
 1325  * 2.  In SYN packets.
 1326  *
 1327  * All ISNs for SYN-ACK packets are generated by the syncache.  See
 1328  * tcp_syncache.c for details.
 1329  *
 1330  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 1331  * depends on this property.  In addition, these ISNs should be
 1332  * unguessable so as to prevent connection hijacking.  To satisfy
 1333  * the requirements of this situation, the algorithm outlined in
 1334  * RFC 1948 is used, with only small modifications.
 1335  *
 1336  * Implementation details:
 1337  *
 1338  * Time is based off the system timer, and is corrected so that it
 1339  * increases by one megabyte per second.  This allows for proper
 1340  * recycling on high speed LANs while still leaving over an hour
 1341  * before rollover.
 1342  *
 1343  * As reading the *exact* system time is too expensive to be done
 1344  * whenever setting up a TCP connection, we increment the time
 1345  * offset in two ways.  First, a small random positive increment
 1346  * is added to isn_offset for each connection that is set up.
 1347  * Second, the function tcp_isn_tick fires once per clock tick
 1348  * and increments isn_offset as necessary so that sequence numbers
 1349  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
 1350  * random positive increments serve only to ensure that the same
 1351  * exact sequence number is never sent out twice (as could otherwise
 1352  * happen when a port is recycled in less than the system tick
 1353  * interval.)
 1354  *
 1355  * net.inet.tcp.isn_reseed_interval controls the number of seconds
 1356  * between seeding of isn_secret.  This is normally set to zero,
 1357  * as reseeding should not be necessary.
 1358  *
 1359  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
 1360  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
 1361  * general, this means holding an exclusive (write) lock.
 1362  */
 1363 
 1364 #define ISN_BYTES_PER_SECOND 1048576
 1365 #define ISN_STATIC_INCREMENT 4096
 1366 #define ISN_RANDOM_INCREMENT (4096 - 1)
 1367 
 1368 static u_char isn_secret[32];
 1369 static int isn_last_reseed;
 1370 static u_int32_t isn_offset, isn_offset_old;
 1371 static MD5_CTX isn_ctx;
 1372 
 1373 tcp_seq
 1374 tcp_new_isn(struct tcpcb *tp)
 1375 {
 1376         u_int32_t md5_buffer[4];
 1377         tcp_seq new_isn;
 1378 
 1379         INP_WLOCK_ASSERT(tp->t_inpcb);
 1380 
 1381         ISN_LOCK();
 1382         /* Seed if this is the first use, reseed if requested. */
 1383         if ((isn_last_reseed == 0) || ((tcp_isn_reseed_interval > 0) &&
 1384              (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval*hz)
 1385                 < (u_int)ticks))) {
 1386                 read_random(&isn_secret, sizeof(isn_secret));
 1387                 isn_last_reseed = ticks;
 1388         }
 1389 
 1390         /* Compute the md5 hash and return the ISN. */
 1391         MD5Init(&isn_ctx);
 1392         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
 1393         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
 1394 #ifdef INET6
 1395         if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
 1396                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
 1397                           sizeof(struct in6_addr));
 1398                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
 1399                           sizeof(struct in6_addr));
 1400         } else
 1401 #endif
 1402         {
 1403                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
 1404                           sizeof(struct in_addr));
 1405                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
 1406                           sizeof(struct in_addr));
 1407         }
 1408         MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret));
 1409         MD5Final((u_char *) &md5_buffer, &isn_ctx);
 1410         new_isn = (tcp_seq) md5_buffer[0];
 1411         isn_offset += ISN_STATIC_INCREMENT +
 1412                 (arc4random() & ISN_RANDOM_INCREMENT);
 1413         new_isn += isn_offset;
 1414         ISN_UNLOCK();
 1415         return (new_isn);
 1416 }
 1417 
 1418 /*
 1419  * Increment the offset to the next ISN_BYTES_PER_SECOND / 100 boundary
 1420  * to keep time flowing at a relatively constant rate.  If the random
 1421  * increments have already pushed us past the projected offset, do nothing.
 1422  */
 1423 static void
 1424 tcp_isn_tick(void *xtp)
 1425 {
 1426         u_int32_t projected_offset;
 1427 
 1428         ISN_LOCK();
 1429         projected_offset = isn_offset_old + ISN_BYTES_PER_SECOND / 100;
 1430 
 1431         if (SEQ_GT(projected_offset, isn_offset))
 1432                 isn_offset = projected_offset;
 1433 
 1434         isn_offset_old = isn_offset;
 1435         callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
 1436         ISN_UNLOCK();
 1437 }
 1438 
 1439 /*
 1440  * When a specific ICMP unreachable message is received and the
 1441  * connection state is SYN-SENT, drop the connection.  This behavior
 1442  * is controlled by the icmp_may_rst sysctl.
 1443  */
 1444 struct inpcb *
 1445 tcp_drop_syn_sent(struct inpcb *inp, int errno)
 1446 {
 1447         struct tcpcb *tp;
 1448 
 1449         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1450         INP_WLOCK_ASSERT(inp);
 1451 
 1452         if ((inp->inp_vflag & INP_TIMEWAIT) ||
 1453             (inp->inp_vflag & INP_DROPPED))
 1454                 return (inp);
 1455 
 1456         tp = intotcpcb(inp);
 1457         if (tp->t_state != TCPS_SYN_SENT)
 1458                 return (inp);
 1459 
 1460         tp = tcp_drop(tp, errno);
 1461         if (tp != NULL)
 1462                 return (inp);
 1463         else
 1464                 return (NULL);
 1465 }
 1466 
 1467 /*
 1468  * When `need fragmentation' ICMP is received, update our idea of the MSS
 1469  * based on the new value in the route.  Also nudge TCP to send something,
 1470  * since we know the packet we just sent was dropped.
 1471  * This duplicates some code in the tcp_mss() function in tcp_input.c.
 1472  */
 1473 struct inpcb *
 1474 tcp_mtudisc(struct inpcb *inp, int errno)
 1475 {
 1476         struct tcpcb *tp;
 1477         struct socket *so = inp->inp_socket;
 1478         u_int maxmtu;
 1479         u_int romtu;
 1480         int mss;
 1481 #ifdef INET6
 1482         int isipv6;
 1483 #endif /* INET6 */
 1484 
 1485         INP_WLOCK_ASSERT(inp);
 1486         if ((inp->inp_vflag & INP_TIMEWAIT) ||
 1487             (inp->inp_vflag & INP_DROPPED))
 1488                 return (inp);
 1489 
 1490         tp = intotcpcb(inp);
 1491         KASSERT(tp != NULL, ("tcp_mtudisc: tp == NULL"));
 1492 
 1493 #ifdef INET6
 1494         isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
 1495 #endif
 1496         maxmtu = tcp_hc_getmtu(&inp->inp_inc); /* IPv4 and IPv6 */
 1497         romtu =
 1498 #ifdef INET6
 1499             isipv6 ? tcp_maxmtu6(&inp->inp_inc, NULL) :
 1500 #endif /* INET6 */
 1501             tcp_maxmtu(&inp->inp_inc, NULL);
 1502         if (!maxmtu)
 1503                 maxmtu = romtu;
 1504         else
 1505                 maxmtu = min(maxmtu, romtu);
 1506         if (!maxmtu) {
 1507                 tp->t_maxopd = tp->t_maxseg =
 1508 #ifdef INET6
 1509                         isipv6 ? tcp_v6mssdflt :
 1510 #endif /* INET6 */
 1511                         tcp_mssdflt;
 1512                 return (inp);
 1513         }
 1514         mss = maxmtu -
 1515 #ifdef INET6
 1516                 (isipv6 ? sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
 1517 #endif /* INET6 */
 1518                  sizeof(struct tcpiphdr)
 1519 #ifdef INET6
 1520                  )
 1521 #endif /* INET6 */
 1522                 ;
 1523 
 1524         /*
 1525          * XXX - The above conditional probably violates the TCP
 1526          * spec.  The problem is that, since we don't know the
 1527          * other end's MSS, we are supposed to use a conservative
 1528          * default.  But, if we do that, then MTU discovery will
 1529          * never actually take place, because the conservative
 1530          * default is much less than the MTUs typically seen
 1531          * on the Internet today.  For the moment, we'll sweep
 1532          * this under the carpet.
 1533          *
 1534          * The conservative default might not actually be a problem
 1535          * if the only case this occurs is when sending an initial
 1536          * SYN with options and data to a host we've never talked
 1537          * to before.  Then, they will reply with an MSS value which
 1538          * will get recorded and the new parameters should get
 1539          * recomputed.  For Further Study.
 1540          */
 1541         if (tp->t_maxopd <= mss)
 1542                 return (inp);
 1543         tp->t_maxopd = mss;
 1544 
 1545         if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 1546             (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
 1547                 mss -= TCPOLEN_TSTAMP_APPA;
 1548 #if     (MCLBYTES & (MCLBYTES - 1)) == 0
 1549         if (mss > MCLBYTES)
 1550                 mss &= ~(MCLBYTES-1);
 1551 #else
 1552         if (mss > MCLBYTES)
 1553                 mss = mss / MCLBYTES * MCLBYTES;
 1554 #endif
 1555         if (so->so_snd.sb_hiwat < mss)
 1556                 mss = so->so_snd.sb_hiwat;
 1557 
 1558         tp->t_maxseg = mss;
 1559 
 1560         tcpstat.tcps_mturesent++;
 1561         tp->t_rtttime = 0;
 1562         tp->snd_nxt = tp->snd_una;
 1563         tcp_free_sackholes(tp);
 1564         tp->snd_recover = tp->snd_max;
 1565         if (tp->t_flags & TF_SACK_PERMIT)
 1566                 EXIT_FASTRECOVERY(tp);
 1567         tcp_output_send(tp);
 1568         return (inp);
 1569 }
 1570 
 1571 /*
 1572  * Look-up the routing entry to the peer of this inpcb.  If no route
 1573  * is found and it cannot be allocated, then return NULL.  This routine
 1574  * is called by TCP routines that access the rmx structure and by tcp_mss
 1575  * to get the interface MTU.
 1576  */
 1577 u_long
 1578 tcp_maxmtu(struct in_conninfo *inc, int *flags)
 1579 {
 1580         struct route sro;
 1581         struct sockaddr_in *dst;
 1582         struct ifnet *ifp;
 1583         u_long maxmtu = 0;
 1584 
 1585         KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
 1586 
 1587         bzero(&sro, sizeof(sro));
 1588         if (inc->inc_faddr.s_addr != INADDR_ANY) {
 1589                 dst = (struct sockaddr_in *)&sro.ro_dst;
 1590                 dst->sin_family = AF_INET;
 1591                 dst->sin_len = sizeof(*dst);
 1592                 dst->sin_addr = inc->inc_faddr;
 1593                 in_rtalloc_ign(&sro, RTF_CLONING, inc->inc_fibnum);
 1594         }
 1595         if (sro.ro_rt != NULL) {
 1596                 ifp = sro.ro_rt->rt_ifp;
 1597                 if (sro.ro_rt->rt_rmx.rmx_mtu == 0)
 1598                         maxmtu = ifp->if_mtu;
 1599                 else
 1600                         maxmtu = min(sro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
 1601 
 1602                 /* Report additional interface capabilities. */
 1603                 if (flags != NULL) {
 1604                         if (ifp->if_capenable & IFCAP_TSO4 &&
 1605                             ifp->if_hwassist & CSUM_TSO)
 1606                                 *flags |= CSUM_TSO;
 1607                 }
 1608                 RTFREE(sro.ro_rt);
 1609         }
 1610         return (maxmtu);
 1611 }
 1612 
 1613 #ifdef INET6
 1614 u_long
 1615 tcp_maxmtu6(struct in_conninfo *inc, int *flags)
 1616 {
 1617         struct route_in6 sro6;
 1618         struct ifnet *ifp;
 1619         u_long maxmtu = 0;
 1620 
 1621         KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
 1622 
 1623         bzero(&sro6, sizeof(sro6));
 1624         if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
 1625                 sro6.ro_dst.sin6_family = AF_INET6;
 1626                 sro6.ro_dst.sin6_len = sizeof(struct sockaddr_in6);
 1627                 sro6.ro_dst.sin6_addr = inc->inc6_faddr;
 1628                 rtalloc_ign((struct route *)&sro6, RTF_CLONING);
 1629         }
 1630         if (sro6.ro_rt != NULL) {
 1631                 ifp = sro6.ro_rt->rt_ifp;
 1632                 if (sro6.ro_rt->rt_rmx.rmx_mtu == 0)
 1633                         maxmtu = IN6_LINKMTU(sro6.ro_rt->rt_ifp);
 1634                 else
 1635                         maxmtu = min(sro6.ro_rt->rt_rmx.rmx_mtu,
 1636                                      IN6_LINKMTU(sro6.ro_rt->rt_ifp));
 1637 
 1638                 /* Report additional interface capabilities. */
 1639                 if (flags != NULL) {
 1640                         if (ifp->if_capenable & IFCAP_TSO6 &&
 1641                             ifp->if_hwassist & CSUM_TSO)
 1642                                 *flags |= CSUM_TSO;
 1643                 }
 1644                 RTFREE(sro6.ro_rt);
 1645         }
 1646 
 1647         return (maxmtu);
 1648 }
 1649 #endif /* INET6 */
 1650 
 1651 #ifdef IPSEC
 1652 /* compute ESP/AH header size for TCP, including outer IP header. */
 1653 size_t
 1654 ipsec_hdrsiz_tcp(struct tcpcb *tp)
 1655 {
 1656         struct inpcb *inp;
 1657         struct mbuf *m;
 1658         size_t hdrsiz;
 1659         struct ip *ip;
 1660 #ifdef INET6
 1661         struct ip6_hdr *ip6;
 1662 #endif
 1663         struct tcphdr *th;
 1664 
 1665         if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
 1666                 return (0);
 1667         MGETHDR(m, M_DONTWAIT, MT_DATA);
 1668         if (!m)
 1669                 return (0);
 1670 
 1671 #ifdef INET6
 1672         if ((inp->inp_vflag & INP_IPV6) != 0) {
 1673                 ip6 = mtod(m, struct ip6_hdr *);
 1674                 th = (struct tcphdr *)(ip6 + 1);
 1675                 m->m_pkthdr.len = m->m_len =
 1676                         sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1677                 tcpip_fillheaders(inp, ip6, th);
 1678                 hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1679         } else
 1680 #endif /* INET6 */
 1681         {
 1682                 ip = mtod(m, struct ip *);
 1683                 th = (struct tcphdr *)(ip + 1);
 1684                 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
 1685                 tcpip_fillheaders(inp, ip, th);
 1686                 hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1687         }
 1688 
 1689         m_free(m);
 1690         return (hdrsiz);
 1691 }
 1692 #endif /* IPSEC */
 1693 
 1694 /*
 1695  * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING
 1696  *
 1697  * This code attempts to calculate the bandwidth-delay product as a
 1698  * means of determining the optimal window size to maximize bandwidth,
 1699  * minimize RTT, and avoid the over-allocation of buffers on interfaces and
 1700  * routers.  This code also does a fairly good job keeping RTTs in check
 1701  * across slow links like modems.  We implement an algorithm which is very
 1702  * similar (but not meant to be) TCP/Vegas.  The code operates on the
 1703  * transmitter side of a TCP connection and so only effects the transmit
 1704  * side of the connection.
 1705  *
 1706  * BACKGROUND:  TCP makes no provision for the management of buffer space
 1707  * at the end points or at the intermediate routers and switches.  A TCP
 1708  * stream, whether using NewReno or not, will eventually buffer as
 1709  * many packets as it is able and the only reason this typically works is
 1710  * due to the fairly small default buffers made available for a connection
 1711  * (typicaly 16K or 32K).  As machines use larger windows and/or window
 1712  * scaling it is now fairly easy for even a single TCP connection to blow-out
 1713  * all available buffer space not only on the local interface, but on
 1714  * intermediate routers and switches as well.  NewReno makes a misguided
 1715  * attempt to 'solve' this problem by waiting for an actual failure to occur,
 1716  * then backing off, then steadily increasing the window again until another
 1717  * failure occurs, ad-infinitum.  This results in terrible oscillation that
 1718  * is only made worse as network loads increase and the idea of intentionally
 1719  * blowing out network buffers is, frankly, a terrible way to manage network
 1720  * resources.
 1721  *
 1722  * It is far better to limit the transmit window prior to the failure
 1723  * condition being achieved.  There are two general ways to do this:  First
 1724  * you can 'scan' through different transmit window sizes and locate the
 1725  * point where the RTT stops increasing, indicating that you have filled the
 1726  * pipe, then scan backwards until you note that RTT stops decreasing, then
 1727  * repeat ad-infinitum.  This method works in principle but has severe
 1728  * implementation issues due to RTT variances, timer granularity, and
 1729  * instability in the algorithm which can lead to many false positives and
 1730  * create oscillations as well as interact badly with other TCP streams
 1731  * implementing the same algorithm.
 1732  *
 1733  * The second method is to limit the window to the bandwidth delay product
 1734  * of the link.  This is the method we implement.  RTT variances and our
 1735  * own manipulation of the congestion window, bwnd, can potentially
 1736  * destabilize the algorithm.  For this reason we have to stabilize the
 1737  * elements used to calculate the window.  We do this by using the minimum
 1738  * observed RTT, the long term average of the observed bandwidth, and
 1739  * by adding two segments worth of slop.  It isn't perfect but it is able
 1740  * to react to changing conditions and gives us a very stable basis on
 1741  * which to extend the algorithm.
 1742  */
 1743 void
 1744 tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq)
 1745 {
 1746         u_long bw;
 1747         u_long bwnd;
 1748         int save_ticks;
 1749 
 1750         INP_WLOCK_ASSERT(tp->t_inpcb);
 1751 
 1752         /*
 1753          * If inflight_enable is disabled in the middle of a tcp connection,
 1754          * make sure snd_bwnd is effectively disabled.
 1755          */
 1756         if (tcp_inflight_enable == 0 || tp->t_rttlow < tcp_inflight_rttthresh) {
 1757                 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 1758                 tp->snd_bandwidth = 0;
 1759                 return;
 1760         }
 1761 
 1762         /*
 1763          * Figure out the bandwidth.  Due to the tick granularity this
 1764          * is a very rough number and it MUST be averaged over a fairly
 1765          * long period of time.  XXX we need to take into account a link
 1766          * that is not using all available bandwidth, but for now our
 1767          * slop will ramp us up if this case occurs and the bandwidth later
 1768          * increases.
 1769          *
 1770          * Note: if ticks rollover 'bw' may wind up negative.  We must
 1771          * effectively reset t_bw_rtttime for this case.
 1772          */
 1773         save_ticks = ticks;
 1774         if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1)
 1775                 return;
 1776 
 1777         bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz /
 1778             (save_ticks - tp->t_bw_rtttime);
 1779         tp->t_bw_rtttime = save_ticks;
 1780         tp->t_bw_rtseq = ack_seq;
 1781         if (tp->t_bw_rtttime == 0 || (int)bw < 0)
 1782                 return;
 1783         bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4;
 1784 
 1785         tp->snd_bandwidth = bw;
 1786 
 1787         /*
 1788          * Calculate the semi-static bandwidth delay product, plus two maximal
 1789          * segments.  The additional slop puts us squarely in the sweet
 1790          * spot and also handles the bandwidth run-up case and stabilization.
 1791          * Without the slop we could be locking ourselves into a lower
 1792          * bandwidth.
 1793          *
 1794          * Situations Handled:
 1795          *      (1) Prevents over-queueing of packets on LANs, especially on
 1796          *          high speed LANs, allowing larger TCP buffers to be
 1797          *          specified, and also does a good job preventing
 1798          *          over-queueing of packets over choke points like modems
 1799          *          (at least for the transmit side).
 1800          *
 1801          *      (2) Is able to handle changing network loads (bandwidth
 1802          *          drops so bwnd drops, bandwidth increases so bwnd
 1803          *          increases).
 1804          *
 1805          *      (3) Theoretically should stabilize in the face of multiple
 1806          *          connections implementing the same algorithm (this may need
 1807          *          a little work).
 1808          *
 1809          *      (4) Stability value (defaults to 20 = 2 maximal packets) can
 1810          *          be adjusted with a sysctl but typically only needs to be
 1811          *          on very slow connections.  A value no smaller then 5
 1812          *          should be used, but only reduce this default if you have
 1813          *          no other choice.
 1814          */
 1815 #define USERTT  ((tp->t_srtt + tp->t_rttbest) / 2)
 1816         bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + tcp_inflight_stab * tp->t_maxseg / 10;
 1817 #undef USERTT
 1818 
 1819         if (tcp_inflight_debug > 0) {
 1820                 static int ltime;
 1821                 if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) {
 1822                         ltime = ticks;
 1823                         printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n",
 1824                             tp,
 1825                             bw,
 1826                             tp->t_rttbest,
 1827                             tp->t_srtt,
 1828                             bwnd
 1829                         );
 1830                 }
 1831         }
 1832         if ((long)bwnd < tcp_inflight_min)
 1833                 bwnd = tcp_inflight_min;
 1834         if (bwnd > tcp_inflight_max)
 1835                 bwnd = tcp_inflight_max;
 1836         if ((long)bwnd < tp->t_maxseg * 2)
 1837                 bwnd = tp->t_maxseg * 2;
 1838         tp->snd_bwnd = bwnd;
 1839 }
 1840 
 1841 #ifdef TCP_SIGNATURE
 1842 /*
 1843  * Callback function invoked by m_apply() to digest TCP segment data
 1844  * contained within an mbuf chain.
 1845  */
 1846 static int
 1847 tcp_signature_apply(void *fstate, void *data, u_int len)
 1848 {
 1849 
 1850         MD5Update(fstate, (u_char *)data, len);
 1851         return (0);
 1852 }
 1853 
 1854 /*
 1855  * Compute TCP-MD5 hash of a TCPv4 segment. (RFC2385)
 1856  *
 1857  * Parameters:
 1858  * m            pointer to head of mbuf chain
 1859  * off0         offset to TCP header within the mbuf chain
 1860  * len          length of TCP segment data, excluding options
 1861  * optlen       length of TCP segment options
 1862  * buf          pointer to storage for computed MD5 digest
 1863  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 1864  *
 1865  * We do this over ip, tcphdr, segment data, and the key in the SADB.
 1866  * When called from tcp_input(), we can be sure that th_sum has been
 1867  * zeroed out and verified already.
 1868  *
 1869  * This function is for IPv4 use only. Calling this function with an
 1870  * IPv6 packet in the mbuf chain will yield undefined results.
 1871  *
 1872  * Return 0 if successful, otherwise return -1.
 1873  *
 1874  * XXX The key is retrieved from the system's PF_KEY SADB, by keying a
 1875  * search with the destination IP address, and a 'magic SPI' to be
 1876  * determined by the application. This is hardcoded elsewhere to 1179
 1877  * right now. Another branch of this code exists which uses the SPD to
 1878  * specify per-application flows but it is unstable.
 1879  */
 1880 int
 1881 tcp_signature_compute(struct mbuf *m, int off0, int len, int optlen,
 1882     u_char *buf, u_int direction)
 1883 {
 1884         union sockaddr_union dst;
 1885         struct ippseudo ippseudo;
 1886         MD5_CTX ctx;
 1887         int doff;
 1888         struct ip *ip;
 1889         struct ipovly *ipovly;
 1890         struct secasvar *sav;
 1891         struct tcphdr *th;
 1892         u_short savecsum;
 1893 
 1894         KASSERT(m != NULL, ("NULL mbuf chain"));
 1895         KASSERT(buf != NULL, ("NULL signature pointer"));
 1896 
 1897         /* Extract the destination from the IP header in the mbuf. */
 1898         ip = mtod(m, struct ip *);
 1899         bzero(&dst, sizeof(union sockaddr_union));
 1900         dst.sa.sa_len = sizeof(struct sockaddr_in);
 1901         dst.sa.sa_family = AF_INET;
 1902         dst.sin.sin_addr = (direction == IPSEC_DIR_INBOUND) ?
 1903             ip->ip_src : ip->ip_dst;
 1904 
 1905         /* Look up an SADB entry which matches the address of the peer. */
 1906         sav = KEY_ALLOCSA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI));
 1907         if (sav == NULL) {
 1908                 printf("%s: SADB lookup failed for %s\n", __func__,
 1909                     inet_ntoa(dst.sin.sin_addr));
 1910                 return (EINVAL);
 1911         }
 1912 
 1913         MD5Init(&ctx);
 1914         ipovly = (struct ipovly *)ip;
 1915         th = (struct tcphdr *)((u_char *)ip + off0);
 1916         doff = off0 + sizeof(struct tcphdr) + optlen;
 1917 
 1918         /*
 1919          * Step 1: Update MD5 hash with IP pseudo-header.
 1920          *
 1921          * XXX The ippseudo header MUST be digested in network byte order,
 1922          * or else we'll fail the regression test. Assume all fields we've
 1923          * been doing arithmetic on have been in host byte order.
 1924          * XXX One cannot depend on ipovly->ih_len here. When called from
 1925          * tcp_output(), the underlying ip_len member has not yet been set.
 1926          */
 1927         ippseudo.ippseudo_src = ipovly->ih_src;
 1928         ippseudo.ippseudo_dst = ipovly->ih_dst;
 1929         ippseudo.ippseudo_pad = 0;
 1930         ippseudo.ippseudo_p = IPPROTO_TCP;
 1931         ippseudo.ippseudo_len = htons(len + sizeof(struct tcphdr) + optlen);
 1932         MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo));
 1933 
 1934         /*
 1935          * Step 2: Update MD5 hash with TCP header, excluding options.
 1936          * The TCP checksum must be set to zero.
 1937          */
 1938         savecsum = th->th_sum;
 1939         th->th_sum = 0;
 1940         MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
 1941         th->th_sum = savecsum;
 1942 
 1943         /*
 1944          * Step 3: Update MD5 hash with TCP segment data.
 1945          *         Use m_apply() to avoid an early m_pullup().
 1946          */
 1947         if (len > 0)
 1948                 m_apply(m, doff, len, tcp_signature_apply, &ctx);
 1949 
 1950         /*
 1951          * Step 4: Update MD5 hash with shared secret.
 1952          */
 1953         MD5Update(&ctx, sav->key_auth->key_data, _KEYLEN(sav->key_auth));
 1954         MD5Final(buf, &ctx);
 1955 
 1956         key_sa_recordxfer(sav, m);
 1957         KEY_FREESAV(&sav);
 1958         return (0);
 1959 }
 1960 #endif /* TCP_SIGNATURE */
 1961 
 1962 static int
 1963 sysctl_drop(SYSCTL_HANDLER_ARGS)
 1964 {
 1965         /* addrs[0] is a foreign socket, addrs[1] is a local one. */
 1966         struct sockaddr_storage addrs[2];
 1967         struct inpcb *inp;
 1968         struct tcpcb *tp;
 1969         struct tcptw *tw;
 1970         struct sockaddr_in *fin, *lin;
 1971 #ifdef INET6
 1972         struct sockaddr_in6 *fin6, *lin6;
 1973         struct in6_addr f6, l6;
 1974 #endif
 1975         int error;
 1976 
 1977         inp = NULL;
 1978         fin = lin = NULL;
 1979 #ifdef INET6
 1980         fin6 = lin6 = NULL;
 1981 #endif
 1982         error = 0;
 1983 
 1984         if (req->oldptr != NULL || req->oldlen != 0)
 1985                 return (EINVAL);
 1986         if (req->newptr == NULL)
 1987                 return (EPERM);
 1988         if (req->newlen < sizeof(addrs))
 1989                 return (ENOMEM);
 1990         error = SYSCTL_IN(req, &addrs, sizeof(addrs));
 1991         if (error)
 1992                 return (error);
 1993 
 1994         switch (addrs[0].ss_family) {
 1995 #ifdef INET6
 1996         case AF_INET6:
 1997                 fin6 = (struct sockaddr_in6 *)&addrs[0];
 1998                 lin6 = (struct sockaddr_in6 *)&addrs[1];
 1999                 if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
 2000                     lin6->sin6_len != sizeof(struct sockaddr_in6))
 2001                         return (EINVAL);
 2002                 if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
 2003                         if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
 2004                                 return (EINVAL);
 2005                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
 2006                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
 2007                         fin = (struct sockaddr_in *)&addrs[0];
 2008                         lin = (struct sockaddr_in *)&addrs[1];
 2009                         break;
 2010                 }
 2011                 error = sa6_embedscope(fin6, ip6_use_defzone);
 2012                 if (error)
 2013                         return (error);
 2014                 error = sa6_embedscope(lin6, ip6_use_defzone);
 2015                 if (error)
 2016                         return (error);
 2017                 break;
 2018 #endif
 2019         case AF_INET:
 2020                 fin = (struct sockaddr_in *)&addrs[0];
 2021                 lin = (struct sockaddr_in *)&addrs[1];
 2022                 if (fin->sin_len != sizeof(struct sockaddr_in) ||
 2023                     lin->sin_len != sizeof(struct sockaddr_in))
 2024                         return (EINVAL);
 2025                 break;
 2026         default:
 2027                 return (EINVAL);
 2028         }
 2029         INP_INFO_WLOCK(&tcbinfo);
 2030         switch (addrs[0].ss_family) {
 2031 #ifdef INET6
 2032         case AF_INET6:
 2033                 inp = in6_pcblookup_hash(&tcbinfo, &f6, fin6->sin6_port,
 2034                     &l6, lin6->sin6_port, 0, NULL);
 2035                 break;
 2036 #endif
 2037         case AF_INET:
 2038                 inp = in_pcblookup_hash(&tcbinfo, fin->sin_addr, fin->sin_port,
 2039                     lin->sin_addr, lin->sin_port, 0, NULL);
 2040                 break;
 2041         }
 2042         if (inp != NULL) {
 2043                 INP_WLOCK(inp);
 2044                 if (inp->inp_vflag & INP_TIMEWAIT) {
 2045                         /*
 2046                          * XXXRW: There currently exists a state where an
 2047                          * inpcb is present, but its timewait state has been
 2048                          * discarded.  For now, don't allow dropping of this
 2049                          * type of inpcb.
 2050                          */
 2051                         tw = intotw(inp);
 2052                         if (tw != NULL)
 2053                                 tcp_twclose(tw, 0);
 2054                         else
 2055                                 INP_WUNLOCK(inp);
 2056                 } else if (!(inp->inp_vflag & INP_DROPPED) &&
 2057                            !(inp->inp_socket->so_options & SO_ACCEPTCONN)) {
 2058                         tp = intotcpcb(inp);
 2059                         tp = tcp_drop(tp, ECONNABORTED);
 2060                         if (tp != NULL)
 2061                                 INP_WUNLOCK(inp);
 2062                 } else
 2063                         INP_WUNLOCK(inp);
 2064         } else
 2065                 error = ESRCH;
 2066         INP_INFO_WUNLOCK(&tcbinfo);
 2067         return (error);
 2068 }
 2069 
 2070 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
 2071     CTLTYPE_STRUCT|CTLFLAG_WR|CTLFLAG_SKIP, NULL,
 2072     0, sysctl_drop, "", "Drop TCP connection");
 2073 
 2074 /*
 2075  * Generate a standardized TCP log line for use throughout the
 2076  * tcp subsystem.  Memory allocation is done with M_NOWAIT to
 2077  * allow use in the interrupt context.
 2078  *
 2079  * NB: The caller MUST free(s, M_TCPLOG) the returned string.
 2080  * NB: The function may return NULL if memory allocation failed.
 2081  *
 2082  * Due to header inclusion and ordering limitations the struct ip
 2083  * and ip6_hdr pointers have to be passed as void pointers.
 2084  */
 2085 char *
 2086 tcp_log_addrs(struct in_conninfo *inc, struct tcphdr *th, void *ip4hdr,
 2087     const void *ip6hdr)
 2088 {
 2089         char *s, *sp;
 2090         size_t size;
 2091         struct ip *ip;
 2092 #ifdef INET6
 2093         const struct ip6_hdr *ip6;
 2094 
 2095         ip6 = (const struct ip6_hdr *)ip6hdr;
 2096 #endif /* INET6 */
 2097         ip = (struct ip *)ip4hdr;
 2098 
 2099         /*
 2100          * The log line looks like this:
 2101          * "TCP: [1.2.3.4]:50332 to [1.2.3.4]:80 tcpflags 0x2<SYN>"
 2102          */
 2103         size = sizeof("TCP: []:12345 to []:12345 tcpflags 0x2<>") +
 2104             sizeof(PRINT_TH_FLAGS) + 1 +
 2105 #ifdef INET6
 2106             2 * INET6_ADDRSTRLEN;
 2107 #else
 2108             2 * INET_ADDRSTRLEN;
 2109 #endif /* INET6 */
 2110 
 2111         /* Is logging enabled? */
 2112         if (tcp_log_debug == 0 && tcp_log_in_vain == 0)
 2113                 return (NULL);
 2114 
 2115         s = malloc(size, M_TCPLOG, M_ZERO|M_NOWAIT);
 2116         if (s == NULL)
 2117                 return (NULL);
 2118 
 2119         strcat(s, "TCP: [");
 2120         sp = s + strlen(s);
 2121 
 2122         if (inc && inc->inc_isipv6 == 0) {
 2123                 inet_ntoa_r(inc->inc_faddr, sp);
 2124                 sp = s + strlen(s);
 2125                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2126                 sp = s + strlen(s);
 2127                 inet_ntoa_r(inc->inc_laddr, sp);
 2128                 sp = s + strlen(s);
 2129                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2130 #ifdef INET6
 2131         } else if (inc) {
 2132                 ip6_sprintf(sp, &inc->inc6_faddr);
 2133                 sp = s + strlen(s);
 2134                 sprintf(sp, "]:%i to [", ntohs(inc->inc_fport));
 2135                 sp = s + strlen(s);
 2136                 ip6_sprintf(sp, &inc->inc6_laddr);
 2137                 sp = s + strlen(s);
 2138                 sprintf(sp, "]:%i", ntohs(inc->inc_lport));
 2139         } else if (ip6 && th) {
 2140                 ip6_sprintf(sp, &ip6->ip6_src);
 2141                 sp = s + strlen(s);
 2142                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2143                 sp = s + strlen(s);
 2144                 ip6_sprintf(sp, &ip6->ip6_dst);
 2145                 sp = s + strlen(s);
 2146                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2147 #endif /* INET6 */
 2148         } else if (ip && th) {
 2149                 inet_ntoa_r(ip->ip_src, sp);
 2150                 sp = s + strlen(s);
 2151                 sprintf(sp, "]:%i to [", ntohs(th->th_sport));
 2152                 sp = s + strlen(s);
 2153                 inet_ntoa_r(ip->ip_dst, sp);
 2154                 sp = s + strlen(s);
 2155                 sprintf(sp, "]:%i", ntohs(th->th_dport));
 2156         } else {
 2157                 free(s, M_TCPLOG);
 2158                 return (NULL);
 2159         }
 2160         sp = s + strlen(s);
 2161         if (th)
 2162                 sprintf(sp, " tcpflags 0x%b", th->th_flags, PRINT_TH_FLAGS);
 2163         if (*(s + size - 1) != '\0')
 2164                 panic("%s: string too long", __func__);
 2165         return (s);
 2166 }

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