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: releng/6.1/sys/netinet/tcp_subr.c 156186 2006-03-01 21:13:29Z andre $
   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 /*
  181  * TCP bandwidth limiting sysctls.  Note that the default lower bound of
  182  * 1024 exists only for debugging.  A good production default would be
  183  * something like 6100.
  184  */
  185 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, inflight, CTLFLAG_RW, 0,
  186     "TCP inflight data limiting");
  187 
  188 static int      tcp_inflight_enable = 1;
  189 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, enable, CTLFLAG_RW,
  190     &tcp_inflight_enable, 0, "Enable automatic TCP inflight data limiting");
  191 
  192 static int      tcp_inflight_debug = 0;
  193 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, debug, CTLFLAG_RW,
  194     &tcp_inflight_debug, 0, "Debug TCP inflight calculations");
  195 
  196 static int      tcp_inflight_rttthresh;
  197 SYSCTL_PROC(_net_inet_tcp_inflight, OID_AUTO, rttthresh, CTLTYPE_INT|CTLFLAG_RW,
  198     &tcp_inflight_rttthresh, 0, sysctl_msec_to_ticks, "I",
  199     "RTT threshold below which inflight will deactivate itself");
  200 
  201 static int      tcp_inflight_min = 6144;
  202 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, min, CTLFLAG_RW,
  203     &tcp_inflight_min, 0, "Lower-bound for TCP inflight window");
  204 
  205 static int      tcp_inflight_max = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  206 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, max, CTLFLAG_RW,
  207     &tcp_inflight_max, 0, "Upper-bound for TCP inflight window");
  208 
  209 static int      tcp_inflight_stab = 20;
  210 SYSCTL_INT(_net_inet_tcp_inflight, OID_AUTO, stab, CTLFLAG_RW,
  211     &tcp_inflight_stab, 0, "Inflight Algorithm Stabilization 20 = 2 packets");
  212 
  213 uma_zone_t sack_hole_zone;
  214 
  215 static struct inpcb *tcp_notify(struct inpcb *, int);
  216 static void     tcp_discardcb(struct tcpcb *);
  217 static void     tcp_isn_tick(void *);
  218 
  219 /*
  220  * Target size of TCP PCB hash tables. Must be a power of two.
  221  *
  222  * Note that this can be overridden by the kernel environment
  223  * variable net.inet.tcp.tcbhashsize
  224  */
  225 #ifndef TCBHASHSIZE
  226 #define TCBHASHSIZE     512
  227 #endif
  228 
  229 /*
  230  * XXX
  231  * Callouts should be moved into struct tcp directly.  They are currently
  232  * separate because the tcpcb structure is exported to userland for sysctl
  233  * parsing purposes, which do not know about callouts.
  234  */
  235 struct  tcpcb_mem {
  236         struct  tcpcb tcb;
  237         struct  callout tcpcb_mem_rexmt, tcpcb_mem_persist, tcpcb_mem_keep;
  238         struct  callout tcpcb_mem_2msl, tcpcb_mem_delack;
  239 };
  240 
  241 static uma_zone_t tcpcb_zone;
  242 static uma_zone_t tcptw_zone;
  243 struct callout isn_callout;
  244 
  245 /*
  246  * Tcp initialization
  247  */
  248 void
  249 tcp_init()
  250 {
  251         int hashsize = TCBHASHSIZE;
  252 
  253         tcp_delacktime = TCPTV_DELACK;
  254         tcp_keepinit = TCPTV_KEEP_INIT;
  255         tcp_keepidle = TCPTV_KEEP_IDLE;
  256         tcp_keepintvl = TCPTV_KEEPINTVL;
  257         tcp_maxpersistidle = TCPTV_KEEP_IDLE;
  258         tcp_msl = TCPTV_MSL;
  259         tcp_rexmit_min = TCPTV_MIN;
  260         tcp_rexmit_slop = TCPTV_CPU_VAR;
  261         tcp_inflight_rttthresh = TCPTV_INFLIGHT_RTTTHRESH;
  262 
  263         INP_INFO_LOCK_INIT(&tcbinfo, "tcp");
  264         LIST_INIT(&tcb);
  265         tcbinfo.listhead = &tcb;
  266         TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize);
  267         if (!powerof2(hashsize)) {
  268                 printf("WARNING: TCB hash size not a power of 2\n");
  269                 hashsize = 512; /* safe default */
  270         }
  271         tcp_tcbhashsize = hashsize;
  272         tcbinfo.hashbase = hashinit(hashsize, M_PCB, &tcbinfo.hashmask);
  273         tcbinfo.porthashbase = hashinit(hashsize, M_PCB,
  274                                         &tcbinfo.porthashmask);
  275         tcbinfo.ipi_zone = uma_zcreate("inpcb", sizeof(struct inpcb),
  276             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  277         uma_zone_set_max(tcbinfo.ipi_zone, maxsockets);
  278 #ifdef INET6
  279 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
  280 #else /* INET6 */
  281 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
  282 #endif /* INET6 */
  283         if (max_protohdr < TCP_MINPROTOHDR)
  284                 max_protohdr = TCP_MINPROTOHDR;
  285         if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
  286                 panic("tcp_init");
  287 #undef TCP_MINPROTOHDR
  288         /*
  289          * These have to be type stable for the benefit of the timers.
  290          */
  291         tcpcb_zone = uma_zcreate("tcpcb", sizeof(struct tcpcb_mem),
  292             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  293         uma_zone_set_max(tcpcb_zone, maxsockets);
  294         tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
  295             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  296         uma_zone_set_max(tcptw_zone, maxsockets / 5);
  297         tcp_timer_init();
  298         syncache_init();
  299         tcp_hc_init();
  300         tcp_reass_init();
  301         callout_init(&isn_callout, CALLOUT_MPSAFE);
  302         tcp_isn_tick(NULL);
  303         EVENTHANDLER_REGISTER(shutdown_pre_sync, tcp_fini, NULL,
  304                 SHUTDOWN_PRI_DEFAULT);
  305         sack_hole_zone = uma_zcreate("sackhole", sizeof(struct sackhole),
  306             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  307 }
  308 
  309 void
  310 tcp_fini(xtp)
  311         void *xtp;
  312 {
  313         callout_stop(&isn_callout);
  314 
  315 }
  316 
  317 /*
  318  * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
  319  * tcp_template used to store this data in mbufs, but we now recopy it out
  320  * of the tcpcb each time to conserve mbufs.
  321  */
  322 void
  323 tcpip_fillheaders(inp, ip_ptr, tcp_ptr)
  324         struct inpcb *inp;
  325         void *ip_ptr;
  326         void *tcp_ptr;
  327 {
  328         struct tcphdr *th = (struct tcphdr *)tcp_ptr;
  329 
  330         INP_LOCK_ASSERT(inp);
  331 
  332 #ifdef INET6
  333         if ((inp->inp_vflag & INP_IPV6) != 0) {
  334                 struct ip6_hdr *ip6;
  335 
  336                 ip6 = (struct ip6_hdr *)ip_ptr;
  337                 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
  338                         (inp->in6p_flowinfo & IPV6_FLOWINFO_MASK);
  339                 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
  340                         (IPV6_VERSION & IPV6_VERSION_MASK);
  341                 ip6->ip6_nxt = IPPROTO_TCP;
  342                 ip6->ip6_plen = sizeof(struct tcphdr);
  343                 ip6->ip6_src = inp->in6p_laddr;
  344                 ip6->ip6_dst = inp->in6p_faddr;
  345         } else
  346 #endif
  347         {
  348                 struct ip *ip;
  349 
  350                 ip = (struct ip *)ip_ptr;
  351                 ip->ip_v = IPVERSION;
  352                 ip->ip_hl = 5;
  353                 ip->ip_tos = inp->inp_ip_tos;
  354                 ip->ip_len = 0;
  355                 ip->ip_id = 0;
  356                 ip->ip_off = 0;
  357                 ip->ip_ttl = inp->inp_ip_ttl;
  358                 ip->ip_sum = 0;
  359                 ip->ip_p = IPPROTO_TCP;
  360                 ip->ip_src = inp->inp_laddr;
  361                 ip->ip_dst = inp->inp_faddr;
  362         }
  363         th->th_sport = inp->inp_lport;
  364         th->th_dport = inp->inp_fport;
  365         th->th_seq = 0;
  366         th->th_ack = 0;
  367         th->th_x2 = 0;
  368         th->th_off = 5;
  369         th->th_flags = 0;
  370         th->th_win = 0;
  371         th->th_urp = 0;
  372         th->th_sum = 0;         /* in_pseudo() is called later for ipv4 */
  373 }
  374 
  375 /*
  376  * Create template to be used to send tcp packets on a connection.
  377  * Allocates an mbuf and fills in a skeletal tcp/ip header.  The only
  378  * use for this function is in keepalives, which use tcp_respond.
  379  */
  380 struct tcptemp *
  381 tcpip_maketemplate(inp)
  382         struct inpcb *inp;
  383 {
  384         struct mbuf *m;
  385         struct tcptemp *n;
  386 
  387         m = m_get(M_DONTWAIT, MT_DATA);
  388         if (m == NULL)
  389                 return (0);
  390         m->m_len = sizeof(struct tcptemp);
  391         n = mtod(m, struct tcptemp *);
  392 
  393         tcpip_fillheaders(inp, (void *)&n->tt_ipgen, (void *)&n->tt_t);
  394         return (n);
  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(tp, ipgen, th, m, ack, seq, flags)
  413         struct tcpcb *tp;
  414         void *ipgen;
  415         register struct tcphdr *th;
  416         register struct mbuf *m;
  417         tcp_seq ack, seq;
  418         int flags;
  419 {
  420         register int tlen;
  421         int win = 0;
  422         struct ip *ip;
  423         struct tcphdr *nth;
  424 #ifdef INET6
  425         struct ip6_hdr *ip6;
  426         int isipv6;
  427 #endif /* INET6 */
  428         int ipflags = 0;
  429         struct inpcb *inp;
  430 
  431         KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
  432 
  433 #ifdef INET6
  434         isipv6 = ((struct ip *)ipgen)->ip_v == 6;
  435         ip6 = ipgen;
  436 #endif /* INET6 */
  437         ip = ipgen;
  438 
  439         if (tp != NULL) {
  440                 inp = tp->t_inpcb;
  441                 KASSERT(inp != NULL, ("tcp control block w/o inpcb"));
  442                 INP_INFO_WLOCK_ASSERT(&tcbinfo);
  443                 INP_LOCK_ASSERT(inp);
  444         } else
  445                 inp = NULL;
  446 
  447         if (tp != NULL) {
  448                 if (!(flags & TH_RST)) {
  449                         win = sbspace(&inp->inp_socket->so_rcv);
  450                         if (win > (long)TCP_MAXWIN << tp->rcv_scale)
  451                                 win = (long)TCP_MAXWIN << tp->rcv_scale;
  452                 }
  453         }
  454         if (m == NULL) {
  455                 m = m_gethdr(M_DONTWAIT, MT_HEADER);
  456                 if (m == NULL)
  457                         return;
  458                 tlen = 0;
  459                 m->m_data += max_linkhdr;
  460 #ifdef INET6
  461                 if (isipv6) {
  462                         bcopy((caddr_t)ip6, mtod(m, caddr_t),
  463                               sizeof(struct ip6_hdr));
  464                         ip6 = mtod(m, struct ip6_hdr *);
  465                         nth = (struct tcphdr *)(ip6 + 1);
  466                 } else
  467 #endif /* INET6 */
  468               {
  469                 bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
  470                 ip = mtod(m, struct ip *);
  471                 nth = (struct tcphdr *)(ip + 1);
  472               }
  473                 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
  474                 flags = TH_ACK;
  475         } else {
  476                 m_freem(m->m_next);
  477                 m->m_next = NULL;
  478                 m->m_data = (caddr_t)ipgen;
  479                 /* m_len is set later */
  480                 tlen = 0;
  481 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
  482 #ifdef INET6
  483                 if (isipv6) {
  484                         xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
  485                         nth = (struct tcphdr *)(ip6 + 1);
  486                 } else
  487 #endif /* INET6 */
  488               {
  489                 xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long);
  490                 nth = (struct tcphdr *)(ip + 1);
  491               }
  492                 if (th != nth) {
  493                         /*
  494                          * this is usually a case when an extension header
  495                          * exists between the IPv6 header and the
  496                          * TCP header.
  497                          */
  498                         nth->th_sport = th->th_sport;
  499                         nth->th_dport = th->th_dport;
  500                 }
  501                 xchg(nth->th_dport, nth->th_sport, n_short);
  502 #undef xchg
  503         }
  504 #ifdef INET6
  505         if (isipv6) {
  506                 ip6->ip6_flow = 0;
  507                 ip6->ip6_vfc = IPV6_VERSION;
  508                 ip6->ip6_nxt = IPPROTO_TCP;
  509                 ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) +
  510                                                 tlen));
  511                 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
  512         } else
  513 #endif
  514         {
  515                 tlen += sizeof (struct tcpiphdr);
  516                 ip->ip_len = tlen;
  517                 ip->ip_ttl = ip_defttl;
  518                 if (path_mtu_discovery)
  519                         ip->ip_off |= IP_DF;
  520         }
  521         m->m_len = tlen;
  522         m->m_pkthdr.len = tlen;
  523         m->m_pkthdr.rcvif = NULL;
  524 #ifdef MAC
  525         if (inp != NULL) {
  526                 /*
  527                  * Packet is associated with a socket, so allow the
  528                  * label of the response to reflect the socket label.
  529                  */
  530                 INP_LOCK_ASSERT(inp);
  531                 mac_create_mbuf_from_inpcb(inp, m);
  532         } else {
  533                 /*
  534                  * Packet is not associated with a socket, so possibly
  535                  * update the label in place.
  536                  */
  537                 mac_reflect_mbuf_tcp(m);
  538         }
  539 #endif
  540         nth->th_seq = htonl(seq);
  541         nth->th_ack = htonl(ack);
  542         nth->th_x2 = 0;
  543         nth->th_off = sizeof (struct tcphdr) >> 2;
  544         nth->th_flags = flags;
  545         if (tp != NULL)
  546                 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
  547         else
  548                 nth->th_win = htons((u_short)win);
  549         nth->th_urp = 0;
  550 #ifdef INET6
  551         if (isipv6) {
  552                 nth->th_sum = 0;
  553                 nth->th_sum = in6_cksum(m, IPPROTO_TCP,
  554                                         sizeof(struct ip6_hdr),
  555                                         tlen - sizeof(struct ip6_hdr));
  556                 ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
  557                     NULL, NULL);
  558         } else
  559 #endif /* INET6 */
  560         {
  561                 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
  562                     htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
  563                 m->m_pkthdr.csum_flags = CSUM_TCP;
  564                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
  565         }
  566 #ifdef TCPDEBUG
  567         if (tp == NULL || (inp->inp_socket->so_options & SO_DEBUG))
  568                 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
  569 #endif
  570 #ifdef INET6
  571         if (isipv6)
  572                 (void) ip6_output(m, NULL, NULL, ipflags, NULL, NULL, inp);
  573         else
  574 #endif /* INET6 */
  575         (void) ip_output(m, NULL, NULL, ipflags, NULL, inp);
  576 }
  577 
  578 /*
  579  * Create a new TCP control block, making an
  580  * empty reassembly queue and hooking it to the argument
  581  * protocol control block.  The `inp' parameter must have
  582  * come from the zone allocator set up in tcp_init().
  583  */
  584 struct tcpcb *
  585 tcp_newtcpcb(inp)
  586         struct inpcb *inp;
  587 {
  588         struct tcpcb_mem *tm;
  589         struct tcpcb *tp;
  590 #ifdef INET6
  591         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  592 #endif /* INET6 */
  593 
  594         tm = uma_zalloc(tcpcb_zone, M_NOWAIT | M_ZERO);
  595         if (tm == NULL)
  596                 return (NULL);
  597         tp = &tm->tcb;
  598         /*      LIST_INIT(&tp->t_segq); */      /* XXX covered by M_ZERO */
  599         tp->t_maxseg = tp->t_maxopd =
  600 #ifdef INET6
  601                 isipv6 ? tcp_v6mssdflt :
  602 #endif /* INET6 */
  603                 tcp_mssdflt;
  604 
  605         /* Set up our timeouts. */
  606         callout_init(tp->tt_rexmt = &tm->tcpcb_mem_rexmt, NET_CALLOUT_MPSAFE);
  607         callout_init(tp->tt_persist = &tm->tcpcb_mem_persist, NET_CALLOUT_MPSAFE);
  608         callout_init(tp->tt_keep = &tm->tcpcb_mem_keep, NET_CALLOUT_MPSAFE);
  609         callout_init(tp->tt_2msl = &tm->tcpcb_mem_2msl, NET_CALLOUT_MPSAFE);
  610         callout_init(tp->tt_delack = &tm->tcpcb_mem_delack, NET_CALLOUT_MPSAFE);
  611 
  612         if (tcp_do_rfc1323)
  613                 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
  614         tp->sack_enable = tcp_do_sack;
  615         TAILQ_INIT(&tp->snd_holes);
  616         tp->t_inpcb = inp;      /* XXX */
  617         /*
  618          * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
  619          * rtt estimate.  Set rttvar so that srtt + 4 * rttvar gives
  620          * reasonable initial retransmit time.
  621          */
  622         tp->t_srtt = TCPTV_SRTTBASE;
  623         tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
  624         tp->t_rttmin = tcp_rexmit_min;
  625         tp->t_rxtcur = TCPTV_RTOBASE;
  626         tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  627         tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  628         tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
  629         tp->t_rcvtime = ticks;
  630         tp->t_bw_rtttime = ticks;
  631         /*
  632          * IPv4 TTL initialization is necessary for an IPv6 socket as well,
  633          * because the socket may be bound to an IPv6 wildcard address,
  634          * which may match an IPv4-mapped IPv6 address.
  635          */
  636         inp->inp_ip_ttl = ip_defttl;
  637         inp->inp_ppcb = (caddr_t)tp;
  638         return (tp);            /* XXX */
  639 }
  640 
  641 /*
  642  * Drop a TCP connection, reporting
  643  * the specified error.  If connection is synchronized,
  644  * then send a RST to peer.
  645  */
  646 struct tcpcb *
  647 tcp_drop(tp, errno)
  648         register struct tcpcb *tp;
  649         int errno;
  650 {
  651         struct socket *so = tp->t_inpcb->inp_socket;
  652 
  653         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  654         INP_LOCK_ASSERT(tp->t_inpcb);
  655 
  656         if (TCPS_HAVERCVDSYN(tp->t_state)) {
  657                 tp->t_state = TCPS_CLOSED;
  658                 (void) tcp_output(tp);
  659                 tcpstat.tcps_drops++;
  660         } else
  661                 tcpstat.tcps_conndrops++;
  662         if (errno == ETIMEDOUT && tp->t_softerror)
  663                 errno = tp->t_softerror;
  664         so->so_error = errno;
  665         return (tcp_close(tp));
  666 }
  667 
  668 static void
  669 tcp_discardcb(tp)
  670         struct tcpcb *tp;
  671 {
  672         struct tseg_qent *q;
  673         struct inpcb *inp = tp->t_inpcb;
  674         struct socket *so = inp->inp_socket;
  675 #ifdef INET6
  676         int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
  677 #endif /* INET6 */
  678 
  679         INP_LOCK_ASSERT(inp);
  680 
  681         /*
  682          * Make sure that all of our timers are stopped before we
  683          * delete the PCB.
  684          */
  685         callout_stop(tp->tt_rexmt);
  686         callout_stop(tp->tt_persist);
  687         callout_stop(tp->tt_keep);
  688         callout_stop(tp->tt_2msl);
  689         callout_stop(tp->tt_delack);
  690 
  691         /*
  692          * If we got enough samples through the srtt filter,
  693          * save the rtt and rttvar in the routing entry.
  694          * 'Enough' is arbitrarily defined as 4 rtt samples.
  695          * 4 samples is enough for the srtt filter to converge
  696          * to within enough % of the correct value; fewer samples
  697          * and we could save a bogus rtt. The danger is not high
  698          * as tcp quickly recovers from everything.
  699          * XXX: Works very well but needs some more statistics!
  700          */
  701         if (tp->t_rttupdated >= 4) {
  702                 struct hc_metrics_lite metrics;
  703                 u_long ssthresh;
  704 
  705                 bzero(&metrics, sizeof(metrics));
  706                 /*
  707                  * Update the ssthresh always when the conditions below
  708                  * are satisfied. This gives us better new start value
  709                  * for the congestion avoidance for new connections.
  710                  * ssthresh is only set if packet loss occured on a session.
  711                  */
  712                 ssthresh = tp->snd_ssthresh;
  713                 if (ssthresh != 0 && ssthresh < so->so_snd.sb_hiwat / 2) {
  714                         /*
  715                          * convert the limit from user data bytes to
  716                          * packets then to packet data bytes.
  717                          */
  718                         ssthresh = (ssthresh + tp->t_maxseg / 2) / tp->t_maxseg;
  719                         if (ssthresh < 2)
  720                                 ssthresh = 2;
  721                         ssthresh *= (u_long)(tp->t_maxseg +
  722 #ifdef INET6
  723                                       (isipv6 ? sizeof (struct ip6_hdr) +
  724                                                sizeof (struct tcphdr) :
  725 #endif
  726                                        sizeof (struct tcpiphdr)
  727 #ifdef INET6
  728                                        )
  729 #endif
  730                                       );
  731                 } else
  732                         ssthresh = 0;
  733                 metrics.rmx_ssthresh = ssthresh;
  734 
  735                 metrics.rmx_rtt = tp->t_srtt;
  736                 metrics.rmx_rttvar = tp->t_rttvar;
  737                 /* XXX: This wraps if the pipe is more than 4 Gbit per second */
  738                 metrics.rmx_bandwidth = tp->snd_bandwidth;
  739                 metrics.rmx_cwnd = tp->snd_cwnd;
  740                 metrics.rmx_sendpipe = 0;
  741                 metrics.rmx_recvpipe = 0;
  742 
  743                 tcp_hc_update(&inp->inp_inc, &metrics);
  744         }
  745 
  746         /* free the reassembly queue, if any */
  747         while ((q = LIST_FIRST(&tp->t_segq)) != NULL) {
  748                 LIST_REMOVE(q, tqe_q);
  749                 m_freem(q->tqe_m);
  750                 uma_zfree(tcp_reass_zone, q);
  751                 tp->t_segqlen--;
  752                 tcp_reass_qsize--;
  753         }
  754         tcp_free_sackholes(tp);
  755         inp->inp_ppcb = NULL;
  756         tp->t_inpcb = NULL;
  757         uma_zfree(tcpcb_zone, tp);
  758         soisdisconnected(so);
  759 }
  760 
  761 /*
  762  * Close a TCP control block:
  763  *    discard all space held by the tcp
  764  *    discard internet protocol block
  765  *    wake up any sleepers
  766  */
  767 struct tcpcb *
  768 tcp_close(tp)
  769         struct tcpcb *tp;
  770 {
  771         struct inpcb *inp = tp->t_inpcb;
  772 #ifdef INET6
  773         struct socket *so = inp->inp_socket;
  774 #endif
  775 
  776         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  777         INP_LOCK_ASSERT(inp);
  778 
  779         tcp_discardcb(tp);
  780 #ifdef INET6
  781         if (INP_CHECK_SOCKAF(so, AF_INET6))
  782                 in6_pcbdetach(inp);
  783         else
  784 #endif
  785                 in_pcbdetach(inp);
  786         tcpstat.tcps_closed++;
  787         return (NULL);
  788 }
  789 
  790 void
  791 tcp_drain()
  792 {
  793         if (do_tcpdrain)
  794         {
  795                 struct inpcb *inpb;
  796                 struct tcpcb *tcpb;
  797                 struct tseg_qent *te;
  798 
  799         /*
  800          * Walk the tcpbs, if existing, and flush the reassembly queue,
  801          * if there is one...
  802          * XXX: The "Net/3" implementation doesn't imply that the TCP
  803          *      reassembly queue should be flushed, but in a situation
  804          *      where we're really low on mbufs, this is potentially
  805          *      usefull.
  806          */
  807                 INP_INFO_RLOCK(&tcbinfo);
  808                 LIST_FOREACH(inpb, tcbinfo.listhead, inp_list) {
  809                         if (inpb->inp_vflag & INP_TIMEWAIT)
  810                                 continue;
  811                         INP_LOCK(inpb);
  812                         if ((tcpb = intotcpcb(inpb)) != NULL) {
  813                                 while ((te = LIST_FIRST(&tcpb->t_segq))
  814                                     != NULL) {
  815                                         LIST_REMOVE(te, tqe_q);
  816                                         m_freem(te->tqe_m);
  817                                         uma_zfree(tcp_reass_zone, te);
  818                                         tcpb->t_segqlen--;
  819                                         tcp_reass_qsize--;
  820                                 }
  821                                 tcp_clean_sackreport(tcpb);
  822                         }
  823                         INP_UNLOCK(inpb);
  824                 }
  825                 INP_INFO_RUNLOCK(&tcbinfo);
  826         }
  827 }
  828 
  829 /*
  830  * Notify a tcp user of an asynchronous error;
  831  * store error as soft error, but wake up user
  832  * (for now, won't do anything until can select for soft error).
  833  *
  834  * Do not wake up user since there currently is no mechanism for
  835  * reporting soft errors (yet - a kqueue filter may be added).
  836  */
  837 static struct inpcb *
  838 tcp_notify(inp, error)
  839         struct inpcb *inp;
  840         int error;
  841 {
  842         struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb;
  843 
  844         INP_INFO_WLOCK_ASSERT(&tcbinfo);
  845         INP_LOCK_ASSERT(inp);
  846 
  847         /*
  848          * Ignore some errors if we are hooked up.
  849          * If connection hasn't completed, has retransmitted several times,
  850          * and receives a second error, give up now.  This is better
  851          * than waiting a long time to establish a connection that
  852          * can never complete.
  853          */
  854         if (tp->t_state == TCPS_ESTABLISHED &&
  855             (error == EHOSTUNREACH || error == ENETUNREACH ||
  856              error == EHOSTDOWN)) {
  857                 return (inp);
  858         } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
  859             tp->t_softerror) {
  860                 tcp_drop(tp, error);
  861                 return (struct inpcb *)0;
  862         } else {
  863                 tp->t_softerror = error;
  864                 return (inp);
  865         }
  866 #if 0
  867         wakeup( &so->so_timeo);
  868         sorwakeup(so);
  869         sowwakeup(so);
  870 #endif
  871 }
  872 
  873 static int
  874 tcp_pcblist(SYSCTL_HANDLER_ARGS)
  875 {
  876         int error, i, n;
  877         struct inpcb *inp, **inp_list;
  878         inp_gen_t gencnt;
  879         struct xinpgen xig;
  880 
  881         /*
  882          * The process of preparing the TCB list is too time-consuming and
  883          * resource-intensive to repeat twice on every request.
  884          */
  885         if (req->oldptr == NULL) {
  886                 n = tcbinfo.ipi_count;
  887                 req->oldidx = 2 * (sizeof xig)
  888                         + (n + n/8) * sizeof(struct xtcpcb);
  889                 return (0);
  890         }
  891 
  892         if (req->newptr != NULL)
  893                 return (EPERM);
  894 
  895         /*
  896          * OK, now we're committed to doing something.
  897          */
  898         INP_INFO_RLOCK(&tcbinfo);
  899         gencnt = tcbinfo.ipi_gencnt;
  900         n = tcbinfo.ipi_count;
  901         INP_INFO_RUNLOCK(&tcbinfo);
  902 
  903         error = sysctl_wire_old_buffer(req, 2 * (sizeof xig)
  904                 + n * sizeof(struct xtcpcb));
  905         if (error != 0)
  906                 return (error);
  907 
  908         xig.xig_len = sizeof xig;
  909         xig.xig_count = n;
  910         xig.xig_gen = gencnt;
  911         xig.xig_sogen = so_gencnt;
  912         error = SYSCTL_OUT(req, &xig, sizeof xig);
  913         if (error)
  914                 return (error);
  915 
  916         inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
  917         if (inp_list == NULL)
  918                 return (ENOMEM);
  919 
  920         INP_INFO_RLOCK(&tcbinfo);
  921         for (inp = LIST_FIRST(tcbinfo.listhead), i = 0; inp != NULL && i < n;
  922              inp = LIST_NEXT(inp, inp_list)) {
  923                 INP_LOCK(inp);
  924                 if (inp->inp_gencnt <= gencnt) {
  925                         /*
  926                          * XXX: This use of cr_cansee(), introduced with
  927                          * TCP state changes, is not quite right, but for
  928                          * now, better than nothing.
  929                          */
  930                         if (inp->inp_vflag & INP_TIMEWAIT)
  931                                 error = cr_cansee(req->td->td_ucred,
  932                                     intotw(inp)->tw_cred);
  933                         else
  934                                 error = cr_canseesocket(req->td->td_ucred,
  935                                     inp->inp_socket);
  936                         if (error == 0)
  937                                 inp_list[i++] = inp;
  938                 }
  939                 INP_UNLOCK(inp);
  940         }
  941         INP_INFO_RUNLOCK(&tcbinfo);
  942         n = i;
  943 
  944         error = 0;
  945         for (i = 0; i < n; i++) {
  946                 inp = inp_list[i];
  947                 if (inp->inp_gencnt <= gencnt) {
  948                         struct xtcpcb xt;
  949                         caddr_t inp_ppcb;
  950 
  951                         bzero(&xt, sizeof(xt));
  952                         xt.xt_len = sizeof xt;
  953                         /* XXX should avoid extra copy */
  954                         bcopy(inp, &xt.xt_inp, sizeof *inp);
  955                         inp_ppcb = inp->inp_ppcb;
  956                         if (inp_ppcb == NULL)
  957                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
  958                         else if (inp->inp_vflag & INP_TIMEWAIT) {
  959                                 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
  960                                 xt.xt_tp.t_state = TCPS_TIME_WAIT;
  961                         } else
  962                                 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
  963                         if (inp->inp_socket != NULL)
  964                                 sotoxsocket(inp->inp_socket, &xt.xt_socket);
  965                         else {
  966                                 bzero(&xt.xt_socket, sizeof xt.xt_socket);
  967                                 xt.xt_socket.xso_protocol = IPPROTO_TCP;
  968                         }
  969                         xt.xt_inp.inp_gencnt = inp->inp_gencnt;
  970                         error = SYSCTL_OUT(req, &xt, sizeof xt);
  971                 }
  972         }
  973         if (!error) {
  974                 /*
  975                  * Give the user an updated idea of our state.
  976                  * If the generation differs from what we told
  977                  * her before, she knows that something happened
  978                  * while we were processing this request, and it
  979                  * might be necessary to retry.
  980                  */
  981                 INP_INFO_RLOCK(&tcbinfo);
  982                 xig.xig_gen = tcbinfo.ipi_gencnt;
  983                 xig.xig_sogen = so_gencnt;
  984                 xig.xig_count = tcbinfo.ipi_count;
  985                 INP_INFO_RUNLOCK(&tcbinfo);
  986                 error = SYSCTL_OUT(req, &xig, sizeof xig);
  987         }
  988         free(inp_list, M_TEMP);
  989         return (error);
  990 }
  991 
  992 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
  993             tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
  994 
  995 static int
  996 tcp_getcred(SYSCTL_HANDLER_ARGS)
  997 {
  998         struct xucred xuc;
  999         struct sockaddr_in addrs[2];
 1000         struct inpcb *inp;
 1001         int error;
 1002 
 1003         error = suser_cred(req->td->td_ucred, SUSER_ALLOWJAIL);
 1004         if (error)
 1005                 return (error);
 1006         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1007         if (error)
 1008                 return (error);
 1009         INP_INFO_RLOCK(&tcbinfo);
 1010         inp = in_pcblookup_hash(&tcbinfo, addrs[1].sin_addr, addrs[1].sin_port,
 1011             addrs[0].sin_addr, addrs[0].sin_port, 0, NULL);
 1012         if (inp == NULL) {
 1013                 error = ENOENT;
 1014                 goto outunlocked;
 1015         }
 1016         INP_LOCK(inp);
 1017         if (inp->inp_socket == NULL) {
 1018                 error = ENOENT;
 1019                 goto out;
 1020         }
 1021         error = cr_canseesocket(req->td->td_ucred, inp->inp_socket);
 1022         if (error)
 1023                 goto out;
 1024         cru2x(inp->inp_socket->so_cred, &xuc);
 1025 out:
 1026         INP_UNLOCK(inp);
 1027 outunlocked:
 1028         INP_INFO_RUNLOCK(&tcbinfo);
 1029         if (error == 0)
 1030                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1031         return (error);
 1032 }
 1033 
 1034 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred,
 1035     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1036     tcp_getcred, "S,xucred", "Get the xucred of a TCP connection");
 1037 
 1038 #ifdef INET6
 1039 static int
 1040 tcp6_getcred(SYSCTL_HANDLER_ARGS)
 1041 {
 1042         struct xucred xuc;
 1043         struct sockaddr_in6 addrs[2];
 1044         struct inpcb *inp;
 1045         int error, mapped = 0;
 1046 
 1047         error = suser_cred(req->td->td_ucred, SUSER_ALLOWJAIL);
 1048         if (error)
 1049                 return (error);
 1050         error = SYSCTL_IN(req, addrs, sizeof(addrs));
 1051         if (error)
 1052                 return (error);
 1053         if ((error = sa6_embedscope(&addrs[0], ip6_use_defzone)) != 0 ||
 1054             (error = sa6_embedscope(&addrs[1], ip6_use_defzone)) != 0) {
 1055                 return (error);
 1056         }
 1057         if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
 1058                 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
 1059                         mapped = 1;
 1060                 else
 1061                         return (EINVAL);
 1062         }
 1063 
 1064         INP_INFO_RLOCK(&tcbinfo);
 1065         if (mapped == 1)
 1066                 inp = in_pcblookup_hash(&tcbinfo,
 1067                         *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
 1068                         addrs[1].sin6_port,
 1069                         *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
 1070                         addrs[0].sin6_port,
 1071                         0, NULL);
 1072         else
 1073                 inp = in6_pcblookup_hash(&tcbinfo,
 1074                         &addrs[1].sin6_addr, addrs[1].sin6_port,
 1075                         &addrs[0].sin6_addr, addrs[0].sin6_port, 0, NULL);
 1076         if (inp == NULL) {
 1077                 error = ENOENT;
 1078                 goto outunlocked;
 1079         }
 1080         INP_LOCK(inp);
 1081         if (inp->inp_socket == NULL) {
 1082                 error = ENOENT;
 1083                 goto out;
 1084         }
 1085         error = cr_canseesocket(req->td->td_ucred, inp->inp_socket);
 1086         if (error)
 1087                 goto out;
 1088         cru2x(inp->inp_socket->so_cred, &xuc);
 1089 out:
 1090         INP_UNLOCK(inp);
 1091 outunlocked:
 1092         INP_INFO_RUNLOCK(&tcbinfo);
 1093         if (error == 0)
 1094                 error = SYSCTL_OUT(req, &xuc, sizeof(struct xucred));
 1095         return (error);
 1096 }
 1097 
 1098 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 1099     CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_PRISON, 0, 0,
 1100     tcp6_getcred, "S,xucred", "Get the xucred of a TCP6 connection");
 1101 #endif
 1102 
 1103 
 1104 void
 1105 tcp_ctlinput(cmd, sa, vip)
 1106         int cmd;
 1107         struct sockaddr *sa;
 1108         void *vip;
 1109 {
 1110         struct ip *ip = vip;
 1111         struct tcphdr *th;
 1112         struct in_addr faddr;
 1113         struct inpcb *inp;
 1114         struct tcpcb *tp;
 1115         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1116         struct icmp *icp;
 1117         struct in_conninfo inc;
 1118         tcp_seq icmp_tcp_seq;
 1119         int mtu;
 1120 
 1121         faddr = ((struct sockaddr_in *)sa)->sin_addr;
 1122         if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
 1123                 return;
 1124 
 1125         if (cmd == PRC_MSGSIZE)
 1126                 notify = tcp_mtudisc;
 1127         else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
 1128                 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
 1129                 notify = tcp_drop_syn_sent;
 1130         /*
 1131          * Redirects don't need to be handled up here.
 1132          */
 1133         else if (PRC_IS_REDIRECT(cmd))
 1134                 return;
 1135         /*
 1136          * Source quench is depreciated.
 1137          */
 1138         else if (cmd == PRC_QUENCH)
 1139                 return;
 1140         /*
 1141          * Hostdead is ugly because it goes linearly through all PCBs.
 1142          * XXX: We never get this from ICMP, otherwise it makes an
 1143          * excellent DoS attack on machines with many connections.
 1144          */
 1145         else if (cmd == PRC_HOSTDEAD)
 1146                 ip = NULL;
 1147         else if ((unsigned)cmd >= PRC_NCMDS || inetctlerrmap[cmd] == 0)
 1148                 return;
 1149         if (ip != NULL) {
 1150                 icp = (struct icmp *)((caddr_t)ip
 1151                                       - offsetof(struct icmp, icmp_ip));
 1152                 th = (struct tcphdr *)((caddr_t)ip
 1153                                        + (ip->ip_hl << 2));
 1154                 INP_INFO_WLOCK(&tcbinfo);
 1155                 inp = in_pcblookup_hash(&tcbinfo, faddr, th->th_dport,
 1156                     ip->ip_src, th->th_sport, 0, NULL);
 1157                 if (inp != NULL)  {
 1158                         INP_LOCK(inp);
 1159                         if (inp->inp_socket != NULL) {
 1160                                 icmp_tcp_seq = htonl(th->th_seq);
 1161                                 tp = intotcpcb(inp);
 1162                                 if (SEQ_GEQ(icmp_tcp_seq, tp->snd_una) &&
 1163                                     SEQ_LT(icmp_tcp_seq, tp->snd_max)) {
 1164                                         if (cmd == PRC_MSGSIZE) {
 1165                                             /*
 1166                                              * MTU discovery:
 1167                                              * If we got a needfrag set the MTU
 1168                                              * in the route to the suggested new
 1169                                              * value (if given) and then notify.
 1170                                              */
 1171                                             bzero(&inc, sizeof(inc));
 1172                                             inc.inc_flags = 0;  /* IPv4 */
 1173                                             inc.inc_faddr = faddr;
 1174 
 1175                                             mtu = ntohs(icp->icmp_nextmtu);
 1176                                             /*
 1177                                              * If no alternative MTU was
 1178                                              * proposed, try the next smaller
 1179                                              * one.  ip->ip_len has already
 1180                                              * been swapped in icmp_input().
 1181                                              */
 1182                                             if (!mtu)
 1183                                                 mtu = ip_next_mtu(ip->ip_len,
 1184                                                  1);
 1185                                             if (mtu < max(296, (tcp_minmss)
 1186                                                  + sizeof(struct tcpiphdr)))
 1187                                                 mtu = 0;
 1188                                             if (!mtu)
 1189                                                 mtu = tcp_mssdflt
 1190                                                  + sizeof(struct tcpiphdr);
 1191                                             /*
 1192                                              * Only cache the the MTU if it
 1193                                              * is smaller than the interface
 1194                                              * or route MTU.  tcp_mtudisc()
 1195                                              * will do right thing by itself.
 1196                                              */
 1197                                             if (mtu <= tcp_maxmtu(&inc))
 1198                                                 tcp_hc_updatemtu(&inc, mtu);
 1199                                         }
 1200 
 1201                                         inp = (*notify)(inp, inetctlerrmap[cmd]);
 1202                                 }
 1203                         }
 1204                         if (inp != NULL)
 1205                                 INP_UNLOCK(inp);
 1206                 } else {
 1207                         inc.inc_fport = th->th_dport;
 1208                         inc.inc_lport = th->th_sport;
 1209                         inc.inc_faddr = faddr;
 1210                         inc.inc_laddr = ip->ip_src;
 1211 #ifdef INET6
 1212                         inc.inc_isipv6 = 0;
 1213 #endif
 1214                         syncache_unreach(&inc, th);
 1215                 }
 1216                 INP_INFO_WUNLOCK(&tcbinfo);
 1217         } else
 1218                 in_pcbnotifyall(&tcbinfo, faddr, inetctlerrmap[cmd], notify);
 1219 }
 1220 
 1221 #ifdef INET6
 1222 void
 1223 tcp6_ctlinput(cmd, sa, d)
 1224         int cmd;
 1225         struct sockaddr *sa;
 1226         void *d;
 1227 {
 1228         struct tcphdr th;
 1229         struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
 1230         struct ip6_hdr *ip6;
 1231         struct mbuf *m;
 1232         struct ip6ctlparam *ip6cp = NULL;
 1233         const struct sockaddr_in6 *sa6_src = NULL;
 1234         int off;
 1235         struct tcp_portonly {
 1236                 u_int16_t th_sport;
 1237                 u_int16_t th_dport;
 1238         } *thp;
 1239 
 1240         if (sa->sa_family != AF_INET6 ||
 1241             sa->sa_len != sizeof(struct sockaddr_in6))
 1242                 return;
 1243 
 1244         if (cmd == PRC_MSGSIZE)
 1245                 notify = tcp_mtudisc;
 1246         else if (!PRC_IS_REDIRECT(cmd) &&
 1247                  ((unsigned)cmd >= PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
 1248                 return;
 1249         /* Source quench is depreciated. */
 1250         else if (cmd == PRC_QUENCH)
 1251                 return;
 1252 
 1253         /* if the parameter is from icmp6, decode it. */
 1254         if (d != NULL) {
 1255                 ip6cp = (struct ip6ctlparam *)d;
 1256                 m = ip6cp->ip6c_m;
 1257                 ip6 = ip6cp->ip6c_ip6;
 1258                 off = ip6cp->ip6c_off;
 1259                 sa6_src = ip6cp->ip6c_src;
 1260         } else {
 1261                 m = NULL;
 1262                 ip6 = NULL;
 1263                 off = 0;        /* fool gcc */
 1264                 sa6_src = &sa6_any;
 1265         }
 1266 
 1267         if (ip6 != NULL) {
 1268                 struct in_conninfo inc;
 1269                 /*
 1270                  * XXX: We assume that when IPV6 is non NULL,
 1271                  * M and OFF are valid.
 1272                  */
 1273 
 1274                 /* check if we can safely examine src and dst ports */
 1275                 if (m->m_pkthdr.len < off + sizeof(*thp))
 1276                         return;
 1277 
 1278                 bzero(&th, sizeof(th));
 1279                 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
 1280 
 1281                 in6_pcbnotify(&tcbinfo, sa, th.th_dport,
 1282                     (struct sockaddr *)ip6cp->ip6c_src,
 1283                     th.th_sport, cmd, NULL, notify);
 1284 
 1285                 inc.inc_fport = th.th_dport;
 1286                 inc.inc_lport = th.th_sport;
 1287                 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
 1288                 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
 1289                 inc.inc_isipv6 = 1;
 1290                 INP_INFO_WLOCK(&tcbinfo);
 1291                 syncache_unreach(&inc, &th);
 1292                 INP_INFO_WUNLOCK(&tcbinfo);
 1293         } else
 1294                 in6_pcbnotify(&tcbinfo, sa, 0, (const struct sockaddr *)sa6_src,
 1295                               0, cmd, NULL, notify);
 1296 }
 1297 #endif /* INET6 */
 1298 
 1299 
 1300 /*
 1301  * Following is where TCP initial sequence number generation occurs.
 1302  *
 1303  * There are two places where we must use initial sequence numbers:
 1304  * 1.  In SYN-ACK packets.
 1305  * 2.  In SYN packets.
 1306  *
 1307  * All ISNs for SYN-ACK packets are generated by the syncache.  See
 1308  * tcp_syncache.c for details.
 1309  *
 1310  * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
 1311  * depends on this property.  In addition, these ISNs should be
 1312  * unguessable so as to prevent connection hijacking.  To satisfy
 1313  * the requirements of this situation, the algorithm outlined in
 1314  * RFC 1948 is used, with only small modifications.
 1315  *
 1316  * Implementation details:
 1317  *
 1318  * Time is based off the system timer, and is corrected so that it
 1319  * increases by one megabyte per second.  This allows for proper
 1320  * recycling on high speed LANs while still leaving over an hour
 1321  * before rollover.
 1322  *
 1323  * As reading the *exact* system time is too expensive to be done
 1324  * whenever setting up a TCP connection, we increment the time
 1325  * offset in two ways.  First, a small random positive increment
 1326  * is added to isn_offset for each connection that is set up.
 1327  * Second, the function tcp_isn_tick fires once per clock tick
 1328  * and increments isn_offset as necessary so that sequence numbers
 1329  * are incremented at approximately ISN_BYTES_PER_SECOND.  The
 1330  * random positive increments serve only to ensure that the same
 1331  * exact sequence number is never sent out twice (as could otherwise
 1332  * happen when a port is recycled in less than the system tick
 1333  * interval.)
 1334  *
 1335  * net.inet.tcp.isn_reseed_interval controls the number of seconds
 1336  * between seeding of isn_secret.  This is normally set to zero,
 1337  * as reseeding should not be necessary.
 1338  *
 1339  * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
 1340  * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock.  In
 1341  * general, this means holding an exclusive (write) lock.
 1342  */
 1343 
 1344 #define ISN_BYTES_PER_SECOND 1048576
 1345 #define ISN_STATIC_INCREMENT 4096
 1346 #define ISN_RANDOM_INCREMENT (4096 - 1)
 1347 
 1348 static u_char isn_secret[32];
 1349 static int isn_last_reseed;
 1350 static u_int32_t isn_offset, isn_offset_old;
 1351 static MD5_CTX isn_ctx;
 1352 
 1353 tcp_seq
 1354 tcp_new_isn(tp)
 1355         struct tcpcb *tp;
 1356 {
 1357         u_int32_t md5_buffer[4];
 1358         tcp_seq new_isn;
 1359 
 1360         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1361         INP_LOCK_ASSERT(tp->t_inpcb);
 1362 
 1363         /* Seed if this is the first use, reseed if requested. */
 1364         if ((isn_last_reseed == 0) || ((tcp_isn_reseed_interval > 0) &&
 1365              (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval*hz)
 1366                 < (u_int)ticks))) {
 1367                 read_random(&isn_secret, sizeof(isn_secret));
 1368                 isn_last_reseed = ticks;
 1369         }
 1370 
 1371         /* Compute the md5 hash and return the ISN. */
 1372         MD5Init(&isn_ctx);
 1373         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
 1374         MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
 1375 #ifdef INET6
 1376         if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
 1377                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
 1378                           sizeof(struct in6_addr));
 1379                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
 1380                           sizeof(struct in6_addr));
 1381         } else
 1382 #endif
 1383         {
 1384                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
 1385                           sizeof(struct in_addr));
 1386                 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
 1387                           sizeof(struct in_addr));
 1388         }
 1389         MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret));
 1390         MD5Final((u_char *) &md5_buffer, &isn_ctx);
 1391         new_isn = (tcp_seq) md5_buffer[0];
 1392         isn_offset += ISN_STATIC_INCREMENT +
 1393                 (arc4random() & ISN_RANDOM_INCREMENT);
 1394         new_isn += isn_offset;
 1395         return (new_isn);
 1396 }
 1397 
 1398 /*
 1399  * Increment the offset to the next ISN_BYTES_PER_SECOND / hz boundary
 1400  * to keep time flowing at a relatively constant rate.  If the random
 1401  * increments have already pushed us past the projected offset, do nothing.
 1402  */
 1403 static void
 1404 tcp_isn_tick(xtp)
 1405         void *xtp;
 1406 {
 1407         u_int32_t projected_offset;
 1408 
 1409         INP_INFO_WLOCK(&tcbinfo);
 1410         projected_offset = isn_offset_old + ISN_BYTES_PER_SECOND / 100;
 1411 
 1412         if (projected_offset > isn_offset)
 1413                 isn_offset = projected_offset;
 1414 
 1415         isn_offset_old = isn_offset;
 1416         callout_reset(&isn_callout, hz/100, tcp_isn_tick, NULL);
 1417         INP_INFO_WUNLOCK(&tcbinfo);
 1418 }
 1419 
 1420 /*
 1421  * When a specific ICMP unreachable message is received and the
 1422  * connection state is SYN-SENT, drop the connection.  This behavior
 1423  * is controlled by the icmp_may_rst sysctl.
 1424  */
 1425 struct inpcb *
 1426 tcp_drop_syn_sent(inp, errno)
 1427         struct inpcb *inp;
 1428         int errno;
 1429 {
 1430         struct tcpcb *tp = intotcpcb(inp);
 1431 
 1432         INP_INFO_WLOCK_ASSERT(&tcbinfo);
 1433         INP_LOCK_ASSERT(inp);
 1434 
 1435         if (tp != NULL && tp->t_state == TCPS_SYN_SENT) {
 1436                 tcp_drop(tp, errno);
 1437                 return (NULL);
 1438         }
 1439         return (inp);
 1440 }
 1441 
 1442 /*
 1443  * When `need fragmentation' ICMP is received, update our idea of the MSS
 1444  * based on the new value in the route.  Also nudge TCP to send something,
 1445  * since we know the packet we just sent was dropped.
 1446  * This duplicates some code in the tcp_mss() function in tcp_input.c.
 1447  */
 1448 struct inpcb *
 1449 tcp_mtudisc(inp, errno)
 1450         struct inpcb *inp;
 1451         int errno;
 1452 {
 1453         struct tcpcb *tp = intotcpcb(inp);
 1454         struct socket *so = inp->inp_socket;
 1455         u_int maxmtu;
 1456         u_int romtu;
 1457         int mss;
 1458 #ifdef INET6
 1459         int isipv6;
 1460 #endif /* INET6 */
 1461 
 1462         INP_LOCK_ASSERT(inp);
 1463         if (tp != NULL) {
 1464 #ifdef INET6
 1465                 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
 1466 #endif
 1467                 maxmtu = tcp_hc_getmtu(&inp->inp_inc); /* IPv4 and IPv6 */
 1468                 romtu =
 1469 #ifdef INET6
 1470                     isipv6 ? tcp_maxmtu6(&inp->inp_inc) :
 1471 #endif /* INET6 */
 1472                     tcp_maxmtu(&inp->inp_inc);
 1473                 if (!maxmtu)
 1474                         maxmtu = romtu;
 1475                 else
 1476                         maxmtu = min(maxmtu, romtu);
 1477                 if (!maxmtu) {
 1478                         tp->t_maxopd = tp->t_maxseg =
 1479 #ifdef INET6
 1480                                 isipv6 ? tcp_v6mssdflt :
 1481 #endif /* INET6 */
 1482                                 tcp_mssdflt;
 1483                         return (inp);
 1484                 }
 1485                 mss = maxmtu -
 1486 #ifdef INET6
 1487                         (isipv6 ?
 1488                          sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
 1489 #endif /* INET6 */
 1490                          sizeof(struct tcpiphdr)
 1491 #ifdef INET6
 1492                          )
 1493 #endif /* INET6 */
 1494                         ;
 1495 
 1496                 /*
 1497                  * XXX - The above conditional probably violates the TCP
 1498                  * spec.  The problem is that, since we don't know the
 1499                  * other end's MSS, we are supposed to use a conservative
 1500                  * default.  But, if we do that, then MTU discovery will
 1501                  * never actually take place, because the conservative
 1502                  * default is much less than the MTUs typically seen
 1503                  * on the Internet today.  For the moment, we'll sweep
 1504                  * this under the carpet.
 1505                  *
 1506                  * The conservative default might not actually be a problem
 1507                  * if the only case this occurs is when sending an initial
 1508                  * SYN with options and data to a host we've never talked
 1509                  * to before.  Then, they will reply with an MSS value which
 1510                  * will get recorded and the new parameters should get
 1511                  * recomputed.  For Further Study.
 1512                  */
 1513                 if (tp->t_maxopd <= mss)
 1514                         return (inp);
 1515                 tp->t_maxopd = mss;
 1516 
 1517                 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
 1518                     (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
 1519                         mss -= TCPOLEN_TSTAMP_APPA;
 1520 #if     (MCLBYTES & (MCLBYTES - 1)) == 0
 1521                 if (mss > MCLBYTES)
 1522                         mss &= ~(MCLBYTES-1);
 1523 #else
 1524                 if (mss > MCLBYTES)
 1525                         mss = mss / MCLBYTES * MCLBYTES;
 1526 #endif
 1527                 if (so->so_snd.sb_hiwat < mss)
 1528                         mss = so->so_snd.sb_hiwat;
 1529 
 1530                 tp->t_maxseg = mss;
 1531 
 1532                 tcpstat.tcps_mturesent++;
 1533                 tp->t_rtttime = 0;
 1534                 tp->snd_nxt = tp->snd_una;
 1535                 tcp_output(tp);
 1536         }
 1537         return (inp);
 1538 }
 1539 
 1540 /*
 1541  * Look-up the routing entry to the peer of this inpcb.  If no route
 1542  * is found and it cannot be allocated, then return NULL.  This routine
 1543  * is called by TCP routines that access the rmx structure and by tcp_mss
 1544  * to get the interface MTU.
 1545  */
 1546 u_long
 1547 tcp_maxmtu(inc)
 1548         struct in_conninfo *inc;
 1549 {
 1550         struct route sro;
 1551         struct sockaddr_in *dst;
 1552         struct ifnet *ifp;
 1553         u_long maxmtu = 0;
 1554 
 1555         KASSERT(inc != NULL, ("tcp_maxmtu with NULL in_conninfo pointer"));
 1556 
 1557         bzero(&sro, sizeof(sro));
 1558         if (inc->inc_faddr.s_addr != INADDR_ANY) {
 1559                 dst = (struct sockaddr_in *)&sro.ro_dst;
 1560                 dst->sin_family = AF_INET;
 1561                 dst->sin_len = sizeof(*dst);
 1562                 dst->sin_addr = inc->inc_faddr;
 1563                 rtalloc_ign(&sro, RTF_CLONING);
 1564         }
 1565         if (sro.ro_rt != NULL) {
 1566                 ifp = sro.ro_rt->rt_ifp;
 1567                 if (sro.ro_rt->rt_rmx.rmx_mtu == 0)
 1568                         maxmtu = ifp->if_mtu;
 1569                 else
 1570                         maxmtu = min(sro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
 1571                 RTFREE(sro.ro_rt);
 1572         }
 1573         return (maxmtu);
 1574 }
 1575 
 1576 #ifdef INET6
 1577 u_long
 1578 tcp_maxmtu6(inc)
 1579         struct in_conninfo *inc;
 1580 {
 1581         struct route_in6 sro6;
 1582         struct ifnet *ifp;
 1583         u_long maxmtu = 0;
 1584 
 1585         KASSERT(inc != NULL, ("tcp_maxmtu6 with NULL in_conninfo pointer"));
 1586 
 1587         bzero(&sro6, sizeof(sro6));
 1588         if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
 1589                 sro6.ro_dst.sin6_family = AF_INET6;
 1590                 sro6.ro_dst.sin6_len = sizeof(struct sockaddr_in6);
 1591                 sro6.ro_dst.sin6_addr = inc->inc6_faddr;
 1592                 rtalloc_ign((struct route *)&sro6, RTF_CLONING);
 1593         }
 1594         if (sro6.ro_rt != NULL) {
 1595                 ifp = sro6.ro_rt->rt_ifp;
 1596                 if (sro6.ro_rt->rt_rmx.rmx_mtu == 0)
 1597                         maxmtu = IN6_LINKMTU(sro6.ro_rt->rt_ifp);
 1598                 else
 1599                         maxmtu = min(sro6.ro_rt->rt_rmx.rmx_mtu,
 1600                                      IN6_LINKMTU(sro6.ro_rt->rt_ifp));
 1601                 RTFREE(sro6.ro_rt);
 1602         }
 1603 
 1604         return (maxmtu);
 1605 }
 1606 #endif /* INET6 */
 1607 
 1608 #ifdef IPSEC
 1609 /* compute ESP/AH header size for TCP, including outer IP header. */
 1610 size_t
 1611 ipsec_hdrsiz_tcp(tp)
 1612         struct tcpcb *tp;
 1613 {
 1614         struct inpcb *inp;
 1615         struct mbuf *m;
 1616         size_t hdrsiz;
 1617         struct ip *ip;
 1618 #ifdef INET6
 1619         struct ip6_hdr *ip6;
 1620 #endif
 1621         struct tcphdr *th;
 1622 
 1623         if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
 1624                 return (0);
 1625         MGETHDR(m, M_DONTWAIT, MT_DATA);
 1626         if (!m)
 1627                 return (0);
 1628 
 1629 #ifdef INET6
 1630         if ((inp->inp_vflag & INP_IPV6) != 0) {
 1631                 ip6 = mtod(m, struct ip6_hdr *);
 1632                 th = (struct tcphdr *)(ip6 + 1);
 1633                 m->m_pkthdr.len = m->m_len =
 1634                         sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1635                 tcpip_fillheaders(inp, ip6, th);
 1636                 hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1637         } else
 1638 #endif /* INET6 */
 1639         {
 1640                 ip = mtod(m, struct ip *);
 1641                 th = (struct tcphdr *)(ip + 1);
 1642                 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
 1643                 tcpip_fillheaders(inp, ip, th);
 1644                 hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
 1645         }
 1646 
 1647         m_free(m);
 1648         return (hdrsiz);
 1649 }
 1650 #endif /*IPSEC*/
 1651 
 1652 /*
 1653  * Move a TCP connection into TIME_WAIT state.
 1654  *    tcbinfo is locked.
 1655  *    inp is locked, and is unlocked before returning.
 1656  */
 1657 void
 1658 tcp_twstart(tp)
 1659         struct tcpcb *tp;
 1660 {
 1661         struct tcptw *tw;
 1662         struct inpcb *inp;
 1663         int tw_time, acknow;
 1664         struct socket *so;
 1665 
 1666         INP_INFO_WLOCK_ASSERT(&tcbinfo);        /* tcp_timer_2msl_reset(). */
 1667         INP_LOCK_ASSERT(tp->t_inpcb);
 1668 
 1669         tw = uma_zalloc(tcptw_zone, M_NOWAIT);
 1670         if (tw == NULL) {
 1671                 tw = tcp_timer_2msl_tw(1);
 1672                 if (tw == NULL) {
 1673                         tcp_close(tp);
 1674                         return;
 1675                 }
 1676         }
 1677         inp = tp->t_inpcb;
 1678         tw->tw_inpcb = inp;
 1679 
 1680         /*
 1681          * Recover last window size sent.
 1682          */
 1683         tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
 1684 
 1685         /*
 1686          * Set t_recent if timestamps are used on the connection.
 1687          */
 1688         if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
 1689             (TF_REQ_TSTMP|TF_RCVD_TSTMP))
 1690                 tw->t_recent = tp->ts_recent;
 1691         else
 1692                 tw->t_recent = 0;
 1693 
 1694         tw->snd_nxt = tp->snd_nxt;
 1695         tw->rcv_nxt = tp->rcv_nxt;
 1696         tw->iss     = tp->iss;
 1697         tw->irs     = tp->irs;
 1698         tw->t_starttime = tp->t_starttime;
 1699         tw->tw_time = 0;
 1700 
 1701 /* XXX
 1702  * If this code will
 1703  * be used for fin-wait-2 state also, then we may need
 1704  * a ts_recent from the last segment.
 1705  */
 1706         tw_time = 2 * tcp_msl;
 1707         acknow = tp->t_flags & TF_ACKNOW;
 1708         tcp_discardcb(tp);
 1709         so = inp->inp_socket;
 1710         ACCEPT_LOCK();
 1711         SOCK_LOCK(so);
 1712         so->so_pcb = NULL;
 1713         tw->tw_cred = crhold(so->so_cred);
 1714         tw->tw_so_options = so->so_options;
 1715         sotryfree(so);
 1716         inp->inp_socket = NULL;
 1717         if (acknow)
 1718                 tcp_twrespond(tw, TH_ACK);
 1719         inp->inp_ppcb = (caddr_t)tw;
 1720         inp->inp_vflag |= INP_TIMEWAIT;
 1721         tcp_timer_2msl_reset(tw, tw_time);
 1722         INP_UNLOCK(inp);
 1723 }
 1724 
 1725 /*
 1726  * The appromixate rate of ISN increase of Microsoft TCP stacks;
 1727  * the actual rate is slightly higher due to the addition of
 1728  * random positive increments.
 1729  *
 1730  * Most other new OSes use semi-randomized ISN values, so we
 1731  * do not need to worry about them.
 1732  */
 1733 #define MS_ISN_BYTES_PER_SECOND         250000
 1734 
 1735 /*
 1736  * Determine if the ISN we will generate has advanced beyond the last
 1737  * sequence number used by the previous connection.  If so, indicate
 1738  * that it is safe to recycle this tw socket by returning 1.
 1739  *
 1740  * XXXRW: This function should assert the inpcb lock as it does multiple
 1741  * non-atomic reads from the tcptw, but is currently called without it from
 1742  * in_pcb.c:in_pcblookup_local().
 1743  */
 1744 int
 1745 tcp_twrecycleable(struct tcptw *tw)
 1746 {
 1747         tcp_seq new_iss = tw->iss;
 1748         tcp_seq new_irs = tw->irs;
 1749 
 1750         new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
 1751         new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
 1752 
 1753         if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
 1754                 return (1);
 1755         else
 1756                 return (0);
 1757 }
 1758 
 1759 struct tcptw *
 1760 tcp_twclose(struct tcptw *tw, int reuse)
 1761 {
 1762         struct inpcb *inp;
 1763 
 1764         inp = tw->tw_inpcb;
 1765         INP_INFO_WLOCK_ASSERT(&tcbinfo);        /* tcp_timer_2msl_stop(). */
 1766         INP_LOCK_ASSERT(inp);
 1767 
 1768         tw->tw_inpcb = NULL;
 1769         tcp_timer_2msl_stop(tw);
 1770         inp->inp_ppcb = NULL;
 1771 #ifdef INET6
 1772         if (inp->inp_vflag & INP_IPV6PROTO)
 1773                 in6_pcbdetach(inp);
 1774         else
 1775 #endif
 1776                 in_pcbdetach(inp);
 1777         tcpstat.tcps_closed++;
 1778         crfree(tw->tw_cred);
 1779         tw->tw_cred = NULL;
 1780         if (reuse)
 1781                 return (tw);
 1782         uma_zfree(tcptw_zone, tw);
 1783         return (NULL);
 1784 }
 1785 
 1786 int
 1787 tcp_twrespond(struct tcptw *tw, int flags)
 1788 {
 1789         struct inpcb *inp = tw->tw_inpcb;
 1790         struct tcphdr *th;
 1791         struct mbuf *m;
 1792         struct ip *ip = NULL;
 1793         u_int8_t *optp;
 1794         u_int hdrlen, optlen;
 1795         int error;
 1796 #ifdef INET6
 1797         struct ip6_hdr *ip6 = NULL;
 1798         int isipv6 = inp->inp_inc.inc_isipv6;
 1799 #endif
 1800 
 1801         INP_LOCK_ASSERT(inp);
 1802 
 1803         m = m_gethdr(M_DONTWAIT, MT_HEADER);
 1804         if (m == NULL)
 1805                 return (ENOBUFS);
 1806         m->m_data += max_linkhdr;
 1807 
 1808 #ifdef MAC
 1809         mac_create_mbuf_from_inpcb(inp, m);
 1810 #endif
 1811 
 1812 #ifdef INET6
 1813         if (isipv6) {
 1814                 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 1815                 ip6 = mtod(m, struct ip6_hdr *);
 1816                 th = (struct tcphdr *)(ip6 + 1);
 1817                 tcpip_fillheaders(inp, ip6, th);
 1818         } else
 1819 #endif
 1820         {
 1821                 hdrlen = sizeof(struct tcpiphdr);
 1822                 ip = mtod(m, struct ip *);
 1823                 th = (struct tcphdr *)(ip + 1);
 1824                 tcpip_fillheaders(inp, ip, th);
 1825         }
 1826         optp = (u_int8_t *)(th + 1);
 1827 
 1828         /*
 1829          * Send a timestamp and echo-reply if both our side and our peer
 1830          * have sent timestamps in our SYN's and this is not a RST.
 1831          */
 1832         if (tw->t_recent && flags == TH_ACK) {
 1833                 u_int32_t *lp = (u_int32_t *)optp;
 1834 
 1835                 /* Form timestamp option as shown in appendix A of RFC 1323. */
 1836                 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
 1837                 *lp++ = htonl(ticks);
 1838                 *lp   = htonl(tw->t_recent);
 1839                 optp += TCPOLEN_TSTAMP_APPA;
 1840         }
 1841 
 1842         optlen = optp - (u_int8_t *)(th + 1);
 1843 
 1844         m->m_len = hdrlen + optlen;
 1845         m->m_pkthdr.len = m->m_len;
 1846 
 1847         KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
 1848 
 1849         th->th_seq = htonl(tw->snd_nxt);
 1850         th->th_ack = htonl(tw->rcv_nxt);
 1851         th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
 1852         th->th_flags = flags;
 1853         th->th_win = htons(tw->last_win);
 1854 
 1855 #ifdef INET6
 1856         if (isipv6) {
 1857                 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
 1858                     sizeof(struct tcphdr) + optlen);
 1859                 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
 1860                 error = ip6_output(m, inp->in6p_outputopts, NULL,
 1861                     (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
 1862         } else
 1863 #endif
 1864         {
 1865                 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
 1866                     htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
 1867                 m->m_pkthdr.csum_flags = CSUM_TCP;
 1868                 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 1869                 ip->ip_len = m->m_pkthdr.len;
 1870                 if (path_mtu_discovery)
 1871                         ip->ip_off |= IP_DF;
 1872                 error = ip_output(m, inp->inp_options, NULL,
 1873                     ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
 1874                     NULL, inp);
 1875         }
 1876         if (flags & TH_ACK)
 1877                 tcpstat.tcps_sndacks++;
 1878         else
 1879                 tcpstat.tcps_sndctrl++;
 1880         tcpstat.tcps_sndtotal++;
 1881         return (error);
 1882 }
 1883 
 1884 /*
 1885  * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING
 1886  *
 1887  * This code attempts to calculate the bandwidth-delay product as a
 1888  * means of determining the optimal window size to maximize bandwidth,
 1889  * minimize RTT, and avoid the over-allocation of buffers on interfaces and
 1890  * routers.  This code also does a fairly good job keeping RTTs in check
 1891  * across slow links like modems.  We implement an algorithm which is very
 1892  * similar (but not meant to be) TCP/Vegas.  The code operates on the
 1893  * transmitter side of a TCP connection and so only effects the transmit
 1894  * side of the connection.
 1895  *
 1896  * BACKGROUND:  TCP makes no provision for the management of buffer space
 1897  * at the end points or at the intermediate routers and switches.  A TCP
 1898  * stream, whether using NewReno or not, will eventually buffer as
 1899  * many packets as it is able and the only reason this typically works is
 1900  * due to the fairly small default buffers made available for a connection
 1901  * (typicaly 16K or 32K).  As machines use larger windows and/or window
 1902  * scaling it is now fairly easy for even a single TCP connection to blow-out
 1903  * all available buffer space not only on the local interface, but on
 1904  * intermediate routers and switches as well.  NewReno makes a misguided
 1905  * attempt to 'solve' this problem by waiting for an actual failure to occur,
 1906  * then backing off, then steadily increasing the window again until another
 1907  * failure occurs, ad-infinitum.  This results in terrible oscillation that
 1908  * is only made worse as network loads increase and the idea of intentionally
 1909  * blowing out network buffers is, frankly, a terrible way to manage network
 1910  * resources.
 1911  *
 1912  * It is far better to limit the transmit window prior to the failure
 1913  * condition being achieved.  There are two general ways to do this:  First
 1914  * you can 'scan' through different transmit window sizes and locate the
 1915  * point where the RTT stops increasing, indicating that you have filled the
 1916  * pipe, then scan backwards until you note that RTT stops decreasing, then
 1917  * repeat ad-infinitum.  This method works in principle but has severe
 1918  * implementation issues due to RTT variances, timer granularity, and
 1919  * instability in the algorithm which can lead to many false positives and
 1920  * create oscillations as well as interact badly with other TCP streams
 1921  * implementing the same algorithm.
 1922  *
 1923  * The second method is to limit the window to the bandwidth delay product
 1924  * of the link.  This is the method we implement.  RTT variances and our
 1925  * own manipulation of the congestion window, bwnd, can potentially
 1926  * destabilize the algorithm.  For this reason we have to stabilize the
 1927  * elements used to calculate the window.  We do this by using the minimum
 1928  * observed RTT, the long term average of the observed bandwidth, and
 1929  * by adding two segments worth of slop.  It isn't perfect but it is able
 1930  * to react to changing conditions and gives us a very stable basis on
 1931  * which to extend the algorithm.
 1932  */
 1933 void
 1934 tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq)
 1935 {
 1936         u_long bw;
 1937         u_long bwnd;
 1938         int save_ticks;
 1939 
 1940         INP_LOCK_ASSERT(tp->t_inpcb);
 1941 
 1942         /*
 1943          * If inflight_enable is disabled in the middle of a tcp connection,
 1944          * make sure snd_bwnd is effectively disabled.
 1945          */
 1946         if (tcp_inflight_enable == 0 || tp->t_rttlow < tcp_inflight_rttthresh) {
 1947                 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 1948                 tp->snd_bandwidth = 0;
 1949                 return;
 1950         }
 1951 
 1952         /*
 1953          * Figure out the bandwidth.  Due to the tick granularity this
 1954          * is a very rough number and it MUST be averaged over a fairly
 1955          * long period of time.  XXX we need to take into account a link
 1956          * that is not using all available bandwidth, but for now our
 1957          * slop will ramp us up if this case occurs and the bandwidth later
 1958          * increases.
 1959          *
 1960          * Note: if ticks rollover 'bw' may wind up negative.  We must
 1961          * effectively reset t_bw_rtttime for this case.
 1962          */
 1963         save_ticks = ticks;
 1964         if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1)
 1965                 return;
 1966 
 1967         bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz /
 1968             (save_ticks - tp->t_bw_rtttime);
 1969         tp->t_bw_rtttime = save_ticks;
 1970         tp->t_bw_rtseq = ack_seq;
 1971         if (tp->t_bw_rtttime == 0 || (int)bw < 0)
 1972                 return;
 1973         bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4;
 1974 
 1975         tp->snd_bandwidth = bw;
 1976 
 1977         /*
 1978          * Calculate the semi-static bandwidth delay product, plus two maximal
 1979          * segments.  The additional slop puts us squarely in the sweet
 1980          * spot and also handles the bandwidth run-up case and stabilization.
 1981          * Without the slop we could be locking ourselves into a lower
 1982          * bandwidth.
 1983          *
 1984          * Situations Handled:
 1985          *      (1) Prevents over-queueing of packets on LANs, especially on
 1986          *          high speed LANs, allowing larger TCP buffers to be
 1987          *          specified, and also does a good job preventing
 1988          *          over-queueing of packets over choke points like modems
 1989          *          (at least for the transmit side).
 1990          *
 1991          *      (2) Is able to handle changing network loads (bandwidth
 1992          *          drops so bwnd drops, bandwidth increases so bwnd
 1993          *          increases).
 1994          *
 1995          *      (3) Theoretically should stabilize in the face of multiple
 1996          *          connections implementing the same algorithm (this may need
 1997          *          a little work).
 1998          *
 1999          *      (4) Stability value (defaults to 20 = 2 maximal packets) can
 2000          *          be adjusted with a sysctl but typically only needs to be
 2001          *          on very slow connections.  A value no smaller then 5
 2002          *          should be used, but only reduce this default if you have
 2003          *          no other choice.
 2004          */
 2005 #define USERTT  ((tp->t_srtt + tp->t_rttbest) / 2)
 2006         bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + tcp_inflight_stab * tp->t_maxseg / 10;
 2007 #undef USERTT
 2008 
 2009         if (tcp_inflight_debug > 0) {
 2010                 static int ltime;
 2011                 if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) {
 2012                         ltime = ticks;
 2013                         printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n",
 2014                             tp,
 2015                             bw,
 2016                             tp->t_rttbest,
 2017                             tp->t_srtt,
 2018                             bwnd
 2019                         );
 2020                 }
 2021         }
 2022         if ((long)bwnd < tcp_inflight_min)
 2023                 bwnd = tcp_inflight_min;
 2024         if (bwnd > tcp_inflight_max)
 2025                 bwnd = tcp_inflight_max;
 2026         if ((long)bwnd < tp->t_maxseg * 2)
 2027                 bwnd = tp->t_maxseg * 2;
 2028         tp->snd_bwnd = bwnd;
 2029 }
 2030 
 2031 #ifdef TCP_SIGNATURE
 2032 /*
 2033  * Callback function invoked by m_apply() to digest TCP segment data
 2034  * contained within an mbuf chain.
 2035  */
 2036 static int
 2037 tcp_signature_apply(void *fstate, void *data, u_int len)
 2038 {
 2039 
 2040         MD5Update(fstate, (u_char *)data, len);
 2041         return (0);
 2042 }
 2043 
 2044 /*
 2045  * Compute TCP-MD5 hash of a TCPv4 segment. (RFC2385)
 2046  *
 2047  * Parameters:
 2048  * m            pointer to head of mbuf chain
 2049  * off0         offset to TCP header within the mbuf chain
 2050  * len          length of TCP segment data, excluding options
 2051  * optlen       length of TCP segment options
 2052  * buf          pointer to storage for computed MD5 digest
 2053  * direction    direction of flow (IPSEC_DIR_INBOUND or OUTBOUND)
 2054  *
 2055  * We do this over ip, tcphdr, segment data, and the key in the SADB.
 2056  * When called from tcp_input(), we can be sure that th_sum has been
 2057  * zeroed out and verified already.
 2058  *
 2059  * This function is for IPv4 use only. Calling this function with an
 2060  * IPv6 packet in the mbuf chain will yield undefined results.
 2061  *
 2062  * Return 0 if successful, otherwise return -1.
 2063  *
 2064  * XXX The key is retrieved from the system's PF_KEY SADB, by keying a
 2065  * search with the destination IP address, and a 'magic SPI' to be
 2066  * determined by the application. This is hardcoded elsewhere to 1179
 2067  * right now. Another branch of this code exists which uses the SPD to
 2068  * specify per-application flows but it is unstable.
 2069  */
 2070 int
 2071 tcp_signature_compute(struct mbuf *m, int off0, int len, int optlen,
 2072     u_char *buf, u_int direction)
 2073 {
 2074         union sockaddr_union dst;
 2075         struct ippseudo ippseudo;
 2076         MD5_CTX ctx;
 2077         int doff;
 2078         struct ip *ip;
 2079         struct ipovly *ipovly;
 2080         struct secasvar *sav;
 2081         struct tcphdr *th;
 2082         u_short savecsum;
 2083 
 2084         KASSERT(m != NULL, ("NULL mbuf chain"));
 2085         KASSERT(buf != NULL, ("NULL signature pointer"));
 2086 
 2087         /* Extract the destination from the IP header in the mbuf. */
 2088         ip = mtod(m, struct ip *);
 2089         bzero(&dst, sizeof(union sockaddr_union));
 2090         dst.sa.sa_len = sizeof(struct sockaddr_in);
 2091         dst.sa.sa_family = AF_INET;
 2092         dst.sin.sin_addr = (direction == IPSEC_DIR_INBOUND) ?
 2093             ip->ip_src : ip->ip_dst;
 2094 
 2095         /* Look up an SADB entry which matches the address of the peer. */
 2096         sav = KEY_ALLOCSA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI));
 2097         if (sav == NULL) {
 2098                 printf("%s: SADB lookup failed for %s\n", __func__,
 2099                     inet_ntoa(dst.sin.sin_addr));
 2100                 return (EINVAL);
 2101         }
 2102 
 2103         MD5Init(&ctx);
 2104         ipovly = (struct ipovly *)ip;
 2105         th = (struct tcphdr *)((u_char *)ip + off0);
 2106         doff = off0 + sizeof(struct tcphdr) + optlen;
 2107 
 2108         /*
 2109          * Step 1: Update MD5 hash with IP pseudo-header.
 2110          *
 2111          * XXX The ippseudo header MUST be digested in network byte order,
 2112          * or else we'll fail the regression test. Assume all fields we've
 2113          * been doing arithmetic on have been in host byte order.
 2114          * XXX One cannot depend on ipovly->ih_len here. When called from
 2115          * tcp_output(), the underlying ip_len member has not yet been set.
 2116          */
 2117         ippseudo.ippseudo_src = ipovly->ih_src;
 2118         ippseudo.ippseudo_dst = ipovly->ih_dst;
 2119         ippseudo.ippseudo_pad = 0;
 2120         ippseudo.ippseudo_p = IPPROTO_TCP;
 2121         ippseudo.ippseudo_len = htons(len + sizeof(struct tcphdr) + optlen);
 2122         MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo));
 2123 
 2124         /*
 2125          * Step 2: Update MD5 hash with TCP header, excluding options.
 2126          * The TCP checksum must be set to zero.
 2127          */
 2128         savecsum = th->th_sum;
 2129         th->th_sum = 0;
 2130         MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
 2131         th->th_sum = savecsum;
 2132 
 2133         /*
 2134          * Step 3: Update MD5 hash with TCP segment data.
 2135          *         Use m_apply() to avoid an early m_pullup().
 2136          */
 2137         if (len > 0)
 2138                 m_apply(m, doff, len, tcp_signature_apply, &ctx);
 2139 
 2140         /*
 2141          * Step 4: Update MD5 hash with shared secret.
 2142          */
 2143         MD5Update(&ctx, _KEYBUF(sav->key_auth), _KEYLEN(sav->key_auth));
 2144         MD5Final(buf, &ctx);
 2145 
 2146         key_sa_recordxfer(sav, m);
 2147         KEY_FREESAV(&sav);
 2148         return (0);
 2149 }
 2150 #endif /* TCP_SIGNATURE */
 2151 
 2152 static int
 2153 sysctl_drop(SYSCTL_HANDLER_ARGS)
 2154 {
 2155         /* addrs[0] is a foreign socket, addrs[1] is a local one. */
 2156         struct sockaddr_storage addrs[2];
 2157         struct inpcb *inp;
 2158         struct tcpcb *tp;
 2159         struct tcptw *tw;
 2160         struct sockaddr_in *fin, *lin;
 2161 #ifdef INET6
 2162         struct sockaddr_in6 *fin6, *lin6;
 2163         struct in6_addr f6, l6;
 2164 #endif
 2165         int error;
 2166 
 2167         inp = NULL;
 2168         fin = lin = NULL;
 2169 #ifdef INET6
 2170         fin6 = lin6 = NULL;
 2171 #endif
 2172         error = 0;
 2173 
 2174         if (req->oldptr != NULL || req->oldlen != 0)
 2175                 return (EINVAL);
 2176         if (req->newptr == NULL)
 2177                 return (EPERM);
 2178         if (req->newlen < sizeof(addrs))
 2179                 return (ENOMEM);
 2180         error = SYSCTL_IN(req, &addrs, sizeof(addrs));
 2181         if (error)
 2182                 return (error);
 2183 
 2184         switch (addrs[0].ss_family) {
 2185 #ifdef INET6
 2186         case AF_INET6:
 2187                 fin6 = (struct sockaddr_in6 *)&addrs[0];
 2188                 lin6 = (struct sockaddr_in6 *)&addrs[1];
 2189                 if (fin6->sin6_len != sizeof(struct sockaddr_in6) ||
 2190                     lin6->sin6_len != sizeof(struct sockaddr_in6))
 2191                         return (EINVAL);
 2192                 if (IN6_IS_ADDR_V4MAPPED(&fin6->sin6_addr)) {
 2193                         if (!IN6_IS_ADDR_V4MAPPED(&lin6->sin6_addr))
 2194                                 return (EINVAL);
 2195                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[0]);
 2196                         in6_sin6_2_sin_in_sock((struct sockaddr *)&addrs[1]);
 2197                         fin = (struct sockaddr_in *)&addrs[0];
 2198                         lin = (struct sockaddr_in *)&addrs[1];
 2199                         break;
 2200                 }
 2201                 error = sa6_embedscope(fin6, ip6_use_defzone);
 2202                 if (error)
 2203                         return (error);
 2204                 error = sa6_embedscope(lin6, ip6_use_defzone);
 2205                 if (error)
 2206                         return (error);
 2207                 break;
 2208 #endif
 2209         case AF_INET:
 2210                 fin = (struct sockaddr_in *)&addrs[0];
 2211                 lin = (struct sockaddr_in *)&addrs[1];
 2212                 if (fin->sin_len != sizeof(struct sockaddr_in) ||
 2213                     lin->sin_len != sizeof(struct sockaddr_in))
 2214                         return (EINVAL);
 2215                 break;
 2216         default:
 2217                 return (EINVAL);
 2218         }
 2219         INP_INFO_WLOCK(&tcbinfo);
 2220         switch (addrs[0].ss_family) {
 2221 #ifdef INET6
 2222         case AF_INET6:
 2223                 inp = in6_pcblookup_hash(&tcbinfo, &f6, fin6->sin6_port,
 2224                     &l6, lin6->sin6_port, 0, NULL);
 2225                 break;
 2226 #endif
 2227         case AF_INET:
 2228                 inp = in_pcblookup_hash(&tcbinfo, fin->sin_addr, fin->sin_port,
 2229                     lin->sin_addr, lin->sin_port, 0, NULL);
 2230                 break;
 2231         }
 2232         if (inp != NULL) {
 2233                 INP_LOCK(inp);
 2234                 if ((tw = intotw(inp)) &&
 2235                     (inp->inp_vflag & INP_TIMEWAIT) != 0) {
 2236                         (void) tcp_twclose(tw, 0);
 2237                 } else if ((tp = intotcpcb(inp)) &&
 2238                     ((inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
 2239                         tp = tcp_drop(tp, ECONNABORTED);
 2240                         if (tp != NULL)
 2241                                 INP_UNLOCK(inp);
 2242                 } else
 2243                         INP_UNLOCK(inp);
 2244         } else
 2245                 error = ESRCH;
 2246         INP_INFO_WUNLOCK(&tcbinfo);
 2247         return (error);
 2248 }
 2249 
 2250 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DROP, drop,
 2251     CTLTYPE_STRUCT|CTLFLAG_WR|CTLFLAG_SKIP, NULL,
 2252     0, sysctl_drop, "", "Drop TCP connection");

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