db225290c5
This fixes tcp-setmss action on little endian machines. PR: 225536 Submitted by: John Zielinski
247 lines
6.5 KiB
C
247 lines
6.5 KiB
C
/*-
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* Copyright (c) 2017 Yandex LLC
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* Copyright (c) 2017 Andrey V. Elsukov <ae@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "opt_inet.h"
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#include "opt_inet6.h"
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/errno.h>
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#include <sys/kernel.h>
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#include <sys/mbuf.h>
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#include <sys/module.h>
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#include <sys/socket.h>
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#include <net/if.h>
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#include <net/if_var.h>
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#include <net/pfil.h>
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#include <net/vnet.h>
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#include <netinet/in.h>
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#include <netinet/ip.h>
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#include <netinet/ip_var.h>
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#include <netinet/tcp.h>
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#include <netinet/ip_fw.h>
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#include <netinet/ip6.h>
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#include <netpfil/ipfw/ip_fw_private.h>
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#include <netpfil/ipfw/pmod/pmod.h>
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#include <machine/in_cksum.h>
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VNET_DEFINE_STATIC(uint16_t, tcpmod_setmss_eid) = 0;
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#define V_tcpmod_setmss_eid VNET(tcpmod_setmss_eid)
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static int
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tcpmod_setmss(struct mbuf **mp, struct tcphdr *tcp, int tlen, uint16_t mss)
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{
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struct mbuf *m;
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u_char *cp;
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int optlen, ret;
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uint16_t oldmss, csum;
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m = *mp;
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ret = IP_FW_DENY;
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if (m->m_len < m->m_pkthdr.len) {
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/*
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* We shouldn't have any data, IP packet contains only
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* TCP header with options.
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*/
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*mp = m = m_pullup(m, m->m_pkthdr.len);
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if (m == NULL)
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return (ret);
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}
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/* Parse TCP options. */
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for (tlen -= sizeof(struct tcphdr), cp = (u_char *)(tcp + 1);
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tlen > 0; tlen -= optlen, cp += optlen) {
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if (cp[0] == TCPOPT_EOL)
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break;
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if (cp[0] == TCPOPT_NOP) {
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optlen = 1;
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continue;
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}
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if (tlen < 2)
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break;
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optlen = cp[1];
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if (optlen < 2 || optlen > tlen)
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break;
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if (cp[0] == TCPOPT_MAXSEG) {
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if (optlen != TCPOLEN_MAXSEG)
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break;
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ret = 0; /* report success */
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bcopy(cp + 2, &oldmss, sizeof(oldmss));
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/* Do not update lower MSS value */
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if (ntohs(oldmss) <= ntohs(mss))
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break;
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bcopy(&mss, cp + 2, sizeof(mss));
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/* Update checksum if it is not delayed. */
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if ((m->m_pkthdr.csum_flags &
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(CSUM_TCP | CSUM_TCP_IPV6)) == 0) {
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bcopy(&tcp->th_sum, &csum, sizeof(csum));
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csum = cksum_adjust(csum, oldmss, mss);
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bcopy(&csum, &tcp->th_sum, sizeof(csum));
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}
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break;
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}
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}
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return (ret);
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}
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#ifdef INET6
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static int
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tcpmod_ipv6_setmss(struct mbuf **mp, uint16_t mss)
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{
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struct ip6_hdr *ip6;
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struct ip6_hbh *hbh;
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struct tcphdr *tcp;
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int hlen, plen, proto;
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ip6 = mtod(*mp, struct ip6_hdr *);
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hlen = sizeof(*ip6);
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proto = ip6->ip6_nxt;
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/*
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* Skip IPv6 extension headers and get the TCP header.
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* ipfw_chk() has already done this work. So we are sure that
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* we will not do an access to the out of bounds. For this
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* reason we skip some checks here.
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*/
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while (proto == IPPROTO_HOPOPTS || proto == IPPROTO_ROUTING ||
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proto == IPPROTO_DSTOPTS) {
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hbh = mtodo(*mp, hlen);
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proto = hbh->ip6h_nxt;
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hlen += (hbh->ip6h_len + 1) << 3;
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}
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tcp = mtodo(*mp, hlen);
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plen = (*mp)->m_pkthdr.len - hlen;
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hlen = tcp->th_off << 2;
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/* We must have TCP options and enough data in a packet. */
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if (hlen <= sizeof(struct tcphdr) || hlen > plen)
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return (IP_FW_DENY);
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return (tcpmod_setmss(mp, tcp, hlen, mss));
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}
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#endif /* INET6 */
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#ifdef INET
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static int
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tcpmod_ipv4_setmss(struct mbuf **mp, uint16_t mss)
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{
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struct tcphdr *tcp;
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struct ip *ip;
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int hlen, plen;
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ip = mtod(*mp, struct ip *);
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hlen = ip->ip_hl << 2;
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tcp = mtodo(*mp, hlen);
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plen = (*mp)->m_pkthdr.len - hlen;
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hlen = tcp->th_off << 2;
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/* We must have TCP options and enough data in a packet. */
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if (hlen <= sizeof(struct tcphdr) || hlen > plen)
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return (IP_FW_DENY);
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return (tcpmod_setmss(mp, tcp, hlen, mss));
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}
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#endif /* INET */
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/*
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* ipfw external action handler.
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*/
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static int
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ipfw_tcpmod(struct ip_fw_chain *chain, struct ip_fw_args *args,
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ipfw_insn *cmd, int *done)
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{
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ipfw_insn *icmd;
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int ret;
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*done = 0; /* try next rule if not matched */
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ret = IP_FW_DENY;
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icmd = cmd + 1;
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if (cmd->opcode != O_EXTERNAL_ACTION ||
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cmd->arg1 != V_tcpmod_setmss_eid ||
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icmd->opcode != O_EXTERNAL_DATA ||
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icmd->len != F_INSN_SIZE(ipfw_insn))
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return (ret);
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/*
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* NOTE: ipfw_chk() can set f_id.proto from IPv6 fragment header,
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* but f_id._flags can be filled only from real TCP header.
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*
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* NOTE: ipfw_chk() drops very short packets in the PULLUP_TO()
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* macro. But we need to check that mbuf is contiguous more than
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* IP+IP_options/IP_extensions+tcphdr length, because TCP header
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* must have TCP options, and ipfw_chk() does PULLUP_TO() size of
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* struct tcphdr.
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*
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* NOTE: we require only the presence of SYN flag. User should
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* properly configure the rule to select the direction of packets,
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* that should be modified.
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*/
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if (args->f_id.proto != IPPROTO_TCP ||
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(args->f_id._flags & TH_SYN) == 0)
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return (ret);
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switch (args->f_id.addr_type) {
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#ifdef INET
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case 4:
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ret = tcpmod_ipv4_setmss(&args->m, htons(icmd->arg1));
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break;
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#endif
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#ifdef INET6
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case 6:
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ret = tcpmod_ipv6_setmss(&args->m, htons(icmd->arg1));
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break;
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#endif
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}
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/*
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* We return zero in both @ret and @done on success, and ipfw_chk()
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* will update rule counters. Otherwise a packet will not be matched
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* by rule.
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*/
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return (ret);
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}
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int
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tcpmod_init(struct ip_fw_chain *ch, int first)
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{
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V_tcpmod_setmss_eid = ipfw_add_eaction(ch, ipfw_tcpmod, "tcp-setmss");
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if (V_tcpmod_setmss_eid == 0)
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return (ENXIO);
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return (0);
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}
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void
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tcpmod_uninit(struct ip_fw_chain *ch, int last)
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{
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ipfw_del_eaction(ch, V_tcpmod_setmss_eid);
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V_tcpmod_setmss_eid = 0;
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}
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