744 lines
19 KiB
C
744 lines
19 KiB
C
/*
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* Copyright (c) 1982, 1986, 1988, 1993
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* The Regents of the University of California.
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* Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG.
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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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* 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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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ipstealth.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/mbuf.h>
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#include <sys/domain.h>
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#include <sys/protosw.h>
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#include <sys/socket.h>
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#include <sys/time.h>
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#include <sys/kernel.h>
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#include <sys/syslog.h>
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#include <sys/sysctl.h>
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#include <net/if.h>
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#include <net/if_types.h>
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#include <net/if_var.h>
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#include <net/if_dl.h>
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#include <net/route.h>
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#include <net/netisr.h>
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#include <net/vnet.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/in_var.h>
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#include <netinet/ip.h>
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#include <netinet/in_pcb.h>
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#include <netinet/ip_var.h>
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#include <netinet/ip_options.h>
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#include <netinet/ip_icmp.h>
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#include <machine/in_cksum.h>
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#include <sys/socketvar.h>
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static int ip_dosourceroute = 0;
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SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
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&ip_dosourceroute, 0, "Enable forwarding source routed IP packets");
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static int ip_acceptsourceroute = 0;
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SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
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CTLFLAG_RW, &ip_acceptsourceroute, 0,
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"Enable accepting source routed IP packets");
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int ip_doopts = 1; /* 0 = ignore, 1 = process, 2 = reject */
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SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_RW,
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&ip_doopts, 0, "Enable IP options processing ([LS]SRR, RR, TS)");
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static void save_rte(struct mbuf *m, u_char *, struct in_addr);
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/*
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* Do option processing on a datagram, possibly discarding it if bad options
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* are encountered, or forwarding it if source-routed.
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*
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* The pass argument is used when operating in the IPSTEALTH mode to tell
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* what options to process: [LS]SRR (pass 0) or the others (pass 1). The
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* reason for as many as two passes is that when doing IPSTEALTH, non-routing
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* options should be processed only if the packet is for us.
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*
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* Returns 1 if packet has been forwarded/freed, 0 if the packet should be
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* processed further.
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*/
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int
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ip_dooptions(struct mbuf *m, int pass)
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{
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struct ip *ip = mtod(m, struct ip *);
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u_char *cp;
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struct in_ifaddr *ia;
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int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
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struct in_addr *sin, dst;
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uint32_t ntime;
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struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
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/* Ignore or reject packets with IP options. */
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if (ip_doopts == 0)
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return 0;
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else if (ip_doopts == 2) {
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type = ICMP_UNREACH;
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code = ICMP_UNREACH_FILTER_PROHIB;
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goto bad;
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}
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dst = ip->ip_dst;
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cp = (u_char *)(ip + 1);
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cnt = (ip->ip_hl << 2) - sizeof (struct ip);
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for (; cnt > 0; cnt -= optlen, cp += optlen) {
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opt = cp[IPOPT_OPTVAL];
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if (opt == IPOPT_EOL)
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break;
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if (opt == IPOPT_NOP)
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optlen = 1;
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else {
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if (cnt < IPOPT_OLEN + sizeof(*cp)) {
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code = &cp[IPOPT_OLEN] - (u_char *)ip;
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goto bad;
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}
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optlen = cp[IPOPT_OLEN];
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if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
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code = &cp[IPOPT_OLEN] - (u_char *)ip;
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goto bad;
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}
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}
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switch (opt) {
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default:
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break;
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/*
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* Source routing with record. Find interface with current
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* destination address. If none on this machine then drop if
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* strictly routed, or do nothing if loosely routed. Record
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* interface address and bring up next address component. If
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* strictly routed make sure next address is on directly
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* accessible net.
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*/
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case IPOPT_LSRR:
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case IPOPT_SSRR:
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#ifdef IPSTEALTH
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if (V_ipstealth && pass > 0)
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break;
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#endif
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if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
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code = &cp[IPOPT_OLEN] - (u_char *)ip;
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goto bad;
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}
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if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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ipaddr.sin_addr = ip->ip_dst;
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if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
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== 0) {
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if (opt == IPOPT_SSRR) {
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type = ICMP_UNREACH;
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code = ICMP_UNREACH_SRCFAIL;
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goto bad;
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}
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if (!ip_dosourceroute)
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goto nosourcerouting;
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/*
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* Loose routing, and not at next destination
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* yet; nothing to do except forward.
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*/
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break;
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}
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off--; /* 0 origin */
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if (off > optlen - (int)sizeof(struct in_addr)) {
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/*
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* End of source route. Should be for us.
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*/
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if (!ip_acceptsourceroute)
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goto nosourcerouting;
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save_rte(m, cp, ip->ip_src);
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break;
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}
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#ifdef IPSTEALTH
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if (V_ipstealth)
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goto dropit;
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#endif
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if (!ip_dosourceroute) {
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if (V_ipforwarding) {
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char buf[16]; /* aaa.bbb.ccc.ddd\0 */
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/*
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* Acting as a router, so generate
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* ICMP
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*/
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nosourcerouting:
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strcpy(buf, inet_ntoa(ip->ip_dst));
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log(LOG_WARNING,
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"attempted source route from %s to %s\n",
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inet_ntoa(ip->ip_src), buf);
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type = ICMP_UNREACH;
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code = ICMP_UNREACH_SRCFAIL;
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goto bad;
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} else {
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/*
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* Not acting as a router, so
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* silently drop.
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*/
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#ifdef IPSTEALTH
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dropit:
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#endif
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IPSTAT_INC(ips_cantforward);
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m_freem(m);
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return (1);
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}
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}
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/*
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* locate outgoing interface
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*/
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(void)memcpy(&ipaddr.sin_addr, cp + off,
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sizeof(ipaddr.sin_addr));
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if (opt == IPOPT_SSRR) {
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#define INA struct in_ifaddr *
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#define SA struct sockaddr *
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if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
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ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
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} else
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/* XXX MRT 0 for routing */
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ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
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if (ia == NULL) {
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type = ICMP_UNREACH;
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code = ICMP_UNREACH_SRCFAIL;
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goto bad;
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}
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ip->ip_dst = ipaddr.sin_addr;
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(void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
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sizeof(struct in_addr));
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ifa_free(&ia->ia_ifa);
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cp[IPOPT_OFFSET] += sizeof(struct in_addr);
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/*
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* Let ip_intr's mcast routing check handle mcast pkts
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*/
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forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
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break;
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case IPOPT_RR:
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#ifdef IPSTEALTH
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if (V_ipstealth && pass == 0)
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break;
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#endif
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if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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/*
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* If no space remains, ignore.
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*/
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off--; /* 0 origin */
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if (off > optlen - (int)sizeof(struct in_addr))
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break;
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(void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
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sizeof(ipaddr.sin_addr));
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/*
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* Locate outgoing interface; if we're the
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* destination, use the incoming interface (should be
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* same).
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*/
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if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
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(ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
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type = ICMP_UNREACH;
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code = ICMP_UNREACH_HOST;
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goto bad;
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}
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(void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
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sizeof(struct in_addr));
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ifa_free(&ia->ia_ifa);
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cp[IPOPT_OFFSET] += sizeof(struct in_addr);
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break;
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case IPOPT_TS:
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#ifdef IPSTEALTH
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if (V_ipstealth && pass == 0)
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break;
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#endif
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code = cp - (u_char *)ip;
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if (optlen < 4 || optlen > 40) {
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code = &cp[IPOPT_OLEN] - (u_char *)ip;
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goto bad;
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}
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if ((off = cp[IPOPT_OFFSET]) < 5) {
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code = &cp[IPOPT_OLEN] - (u_char *)ip;
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goto bad;
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}
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if (off > optlen - (int)sizeof(int32_t)) {
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cp[IPOPT_OFFSET + 1] += (1 << 4);
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if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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break;
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}
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off--; /* 0 origin */
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sin = (struct in_addr *)(cp + off);
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switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
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case IPOPT_TS_TSONLY:
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break;
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case IPOPT_TS_TSANDADDR:
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if (off + sizeof(uint32_t) +
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sizeof(struct in_addr) > optlen) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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ipaddr.sin_addr = dst;
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ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
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m->m_pkthdr.rcvif);
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if (ia == NULL)
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continue;
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(void)memcpy(sin, &IA_SIN(ia)->sin_addr,
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sizeof(struct in_addr));
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ifa_free(&ia->ia_ifa);
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cp[IPOPT_OFFSET] += sizeof(struct in_addr);
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off += sizeof(struct in_addr);
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break;
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case IPOPT_TS_PRESPEC:
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if (off + sizeof(uint32_t) +
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sizeof(struct in_addr) > optlen) {
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code = &cp[IPOPT_OFFSET] - (u_char *)ip;
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goto bad;
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}
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(void)memcpy(&ipaddr.sin_addr, sin,
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sizeof(struct in_addr));
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if (ifa_ifwithaddr((SA)&ipaddr) == NULL)
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continue;
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cp[IPOPT_OFFSET] += sizeof(struct in_addr);
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off += sizeof(struct in_addr);
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break;
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default:
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code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
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goto bad;
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}
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ntime = iptime();
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(void)memcpy(cp + off, &ntime, sizeof(uint32_t));
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cp[IPOPT_OFFSET] += sizeof(uint32_t);
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}
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}
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if (forward && V_ipforwarding) {
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ip_forward(m, 1);
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return (1);
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}
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return (0);
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bad:
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icmp_error(m, type, code, 0, 0);
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IPSTAT_INC(ips_badoptions);
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return (1);
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}
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/*
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* Save incoming source route for use in replies, to be picked up later by
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* ip_srcroute if the receiver is interested.
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*/
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static void
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save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
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{
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unsigned olen;
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struct ipopt_tag *opts;
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opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
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sizeof(struct ipopt_tag), M_NOWAIT);
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if (opts == NULL)
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return;
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olen = option[IPOPT_OLEN];
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if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
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m_tag_free((struct m_tag *)opts);
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return;
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}
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bcopy(option, opts->ip_srcrt.srcopt, olen);
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opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
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opts->ip_srcrt.dst = dst;
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m_tag_prepend(m, (struct m_tag *)opts);
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}
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/*
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* Retrieve incoming source route for use in replies, in the same form used
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* by setsockopt. The first hop is placed before the options, will be
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* removed later.
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*/
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struct mbuf *
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ip_srcroute(struct mbuf *m0)
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{
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struct in_addr *p, *q;
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struct mbuf *m;
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struct ipopt_tag *opts;
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opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
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if (opts == NULL)
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return (NULL);
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if (opts->ip_nhops == 0)
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return (NULL);
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m = m_get(M_DONTWAIT, MT_DATA);
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if (m == NULL)
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return (NULL);
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#define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
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/* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
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m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
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sizeof(struct in_addr) + OPTSIZ;
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/*
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* First, save first hop for return route.
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*/
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p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
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*(mtod(m, struct in_addr *)) = *p--;
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/*
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* Copy option fields and padding (nop) to mbuf.
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*/
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opts->ip_srcrt.nop = IPOPT_NOP;
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opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
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(void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
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&(opts->ip_srcrt.nop), OPTSIZ);
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q = (struct in_addr *)(mtod(m, caddr_t) +
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sizeof(struct in_addr) + OPTSIZ);
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#undef OPTSIZ
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/*
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* Record return path as an IP source route, reversing the path
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* (pointers are now aligned).
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*/
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while (p >= opts->ip_srcrt.route) {
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*q++ = *p--;
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}
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/*
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* Last hop goes to final destination.
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*/
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*q = opts->ip_srcrt.dst;
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m_tag_delete(m0, (struct m_tag *)opts);
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return (m);
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}
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/*
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* Strip out IP options, at higher level protocol in the kernel. Second
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* argument is buffer to which options will be moved, and return value is
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* their length.
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*
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* XXX should be deleted; last arg currently ignored.
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*/
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void
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ip_stripoptions(struct mbuf *m, struct mbuf *mopt)
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{
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int i;
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struct ip *ip = mtod(m, struct ip *);
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caddr_t opts;
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int olen;
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olen = (ip->ip_hl << 2) - sizeof (struct ip);
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opts = (caddr_t)(ip + 1);
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i = m->m_len - (sizeof (struct ip) + olen);
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bcopy(opts + olen, opts, (unsigned)i);
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m->m_len -= olen;
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if (m->m_flags & M_PKTHDR)
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m->m_pkthdr.len -= olen;
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ip->ip_v = IPVERSION;
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ip->ip_hl = sizeof(struct ip) >> 2;
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}
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/*
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* Insert IP options into preformed packet. Adjust IP destination as
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* required for IP source routing, as indicated by a non-zero in_addr at the
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* start of the options.
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*
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* XXX This routine assumes that the packet has no options in place.
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*/
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struct mbuf *
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ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
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{
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struct ipoption *p = mtod(opt, struct ipoption *);
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struct mbuf *n;
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struct ip *ip = mtod(m, struct ip *);
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unsigned optlen;
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optlen = opt->m_len - sizeof(p->ipopt_dst);
|
|
if (optlen + ip->ip_len > IP_MAXPACKET) {
|
|
*phlen = 0;
|
|
return (m); /* XXX should fail */
|
|
}
|
|
if (p->ipopt_dst.s_addr)
|
|
ip->ip_dst = p->ipopt_dst;
|
|
if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
|
|
MGETHDR(n, M_DONTWAIT, MT_DATA);
|
|
if (n == NULL) {
|
|
*phlen = 0;
|
|
return (m);
|
|
}
|
|
M_MOVE_PKTHDR(n, m);
|
|
n->m_pkthdr.rcvif = NULL;
|
|
n->m_pkthdr.len += optlen;
|
|
m->m_len -= sizeof(struct ip);
|
|
m->m_data += sizeof(struct ip);
|
|
n->m_next = m;
|
|
m = n;
|
|
m->m_len = optlen + sizeof(struct ip);
|
|
m->m_data += max_linkhdr;
|
|
bcopy(ip, mtod(m, void *), sizeof(struct ip));
|
|
} else {
|
|
m->m_data -= optlen;
|
|
m->m_len += optlen;
|
|
m->m_pkthdr.len += optlen;
|
|
bcopy(ip, mtod(m, void *), sizeof(struct ip));
|
|
}
|
|
ip = mtod(m, struct ip *);
|
|
bcopy(p->ipopt_list, ip + 1, optlen);
|
|
*phlen = sizeof(struct ip) + optlen;
|
|
ip->ip_v = IPVERSION;
|
|
ip->ip_hl = *phlen >> 2;
|
|
ip->ip_len += optlen;
|
|
return (m);
|
|
}
|
|
|
|
/*
|
|
* Copy options from ip to jp, omitting those not copied during
|
|
* fragmentation.
|
|
*/
|
|
int
|
|
ip_optcopy(struct ip *ip, struct ip *jp)
|
|
{
|
|
u_char *cp, *dp;
|
|
int opt, optlen, cnt;
|
|
|
|
cp = (u_char *)(ip + 1);
|
|
dp = (u_char *)(jp + 1);
|
|
cnt = (ip->ip_hl << 2) - sizeof (struct ip);
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[0];
|
|
if (opt == IPOPT_EOL)
|
|
break;
|
|
if (opt == IPOPT_NOP) {
|
|
/* Preserve for IP mcast tunnel's LSRR alignment. */
|
|
*dp++ = IPOPT_NOP;
|
|
optlen = 1;
|
|
continue;
|
|
}
|
|
|
|
KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
|
|
("ip_optcopy: malformed ipv4 option"));
|
|
optlen = cp[IPOPT_OLEN];
|
|
KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
|
|
("ip_optcopy: malformed ipv4 option"));
|
|
|
|
/* Bogus lengths should have been caught by ip_dooptions. */
|
|
if (optlen > cnt)
|
|
optlen = cnt;
|
|
if (IPOPT_COPIED(opt)) {
|
|
bcopy(cp, dp, optlen);
|
|
dp += optlen;
|
|
}
|
|
}
|
|
for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
|
|
*dp++ = IPOPT_EOL;
|
|
return (optlen);
|
|
}
|
|
|
|
/*
|
|
* Set up IP options in pcb for insertion in output packets. Store in mbuf
|
|
* with pointer in pcbopt, adding pseudo-option with destination address if
|
|
* source routed.
|
|
*/
|
|
int
|
|
ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
|
|
{
|
|
int cnt, optlen;
|
|
u_char *cp;
|
|
struct mbuf **pcbopt;
|
|
u_char opt;
|
|
|
|
INP_WLOCK_ASSERT(inp);
|
|
|
|
pcbopt = &inp->inp_options;
|
|
|
|
/* turn off any old options */
|
|
if (*pcbopt)
|
|
(void)m_free(*pcbopt);
|
|
*pcbopt = 0;
|
|
if (m == NULL || m->m_len == 0) {
|
|
/*
|
|
* Only turning off any previous options.
|
|
*/
|
|
if (m != NULL)
|
|
(void)m_free(m);
|
|
return (0);
|
|
}
|
|
|
|
if (m->m_len % sizeof(int32_t))
|
|
goto bad;
|
|
/*
|
|
* IP first-hop destination address will be stored before actual
|
|
* options; move other options back and clear it when none present.
|
|
*/
|
|
if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
|
|
goto bad;
|
|
cnt = m->m_len;
|
|
m->m_len += sizeof(struct in_addr);
|
|
cp = mtod(m, u_char *) + sizeof(struct in_addr);
|
|
bcopy(mtod(m, void *), cp, (unsigned)cnt);
|
|
bzero(mtod(m, void *), sizeof(struct in_addr));
|
|
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[IPOPT_OPTVAL];
|
|
if (opt == IPOPT_EOL)
|
|
break;
|
|
if (opt == IPOPT_NOP)
|
|
optlen = 1;
|
|
else {
|
|
if (cnt < IPOPT_OLEN + sizeof(*cp))
|
|
goto bad;
|
|
optlen = cp[IPOPT_OLEN];
|
|
if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
|
|
goto bad;
|
|
}
|
|
switch (opt) {
|
|
|
|
default:
|
|
break;
|
|
|
|
case IPOPT_LSRR:
|
|
case IPOPT_SSRR:
|
|
/*
|
|
* User process specifies route as:
|
|
*
|
|
* ->A->B->C->D
|
|
*
|
|
* D must be our final destination (but we can't
|
|
* check that since we may not have connected yet).
|
|
* A is first hop destination, which doesn't appear
|
|
* in actual IP option, but is stored before the
|
|
* options.
|
|
*/
|
|
/* XXX-BZ PRIV_NETINET_SETHDROPTS? */
|
|
if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
|
|
goto bad;
|
|
m->m_len -= sizeof(struct in_addr);
|
|
cnt -= sizeof(struct in_addr);
|
|
optlen -= sizeof(struct in_addr);
|
|
cp[IPOPT_OLEN] = optlen;
|
|
/*
|
|
* Move first hop before start of options.
|
|
*/
|
|
bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
|
|
sizeof(struct in_addr));
|
|
/*
|
|
* Then copy rest of options back
|
|
* to close up the deleted entry.
|
|
*/
|
|
bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
|
|
&cp[IPOPT_OFFSET+1],
|
|
(unsigned)cnt - (IPOPT_MINOFF - 1));
|
|
break;
|
|
}
|
|
}
|
|
if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
|
|
goto bad;
|
|
*pcbopt = m;
|
|
return (0);
|
|
|
|
bad:
|
|
(void)m_free(m);
|
|
return (EINVAL);
|
|
}
|
|
|
|
/*
|
|
* Check for the presence of the IP Router Alert option [RFC2113]
|
|
* in the header of an IPv4 datagram.
|
|
*
|
|
* This call is not intended for use from the forwarding path; it is here
|
|
* so that protocol domains may check for the presence of the option.
|
|
* Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
|
|
* option does not have much relevance to the implementation, though this
|
|
* may change in future.
|
|
* Router alert options SHOULD be passed if running in IPSTEALTH mode and
|
|
* we are not the endpoint.
|
|
* Length checks on individual options should already have been peformed
|
|
* by ip_dooptions() therefore they are folded under INVARIANTS here.
|
|
*
|
|
* Return zero if not present or options are invalid, non-zero if present.
|
|
*/
|
|
int
|
|
ip_checkrouteralert(struct mbuf *m)
|
|
{
|
|
struct ip *ip = mtod(m, struct ip *);
|
|
u_char *cp;
|
|
int opt, optlen, cnt, found_ra;
|
|
|
|
found_ra = 0;
|
|
cp = (u_char *)(ip + 1);
|
|
cnt = (ip->ip_hl << 2) - sizeof (struct ip);
|
|
for (; cnt > 0; cnt -= optlen, cp += optlen) {
|
|
opt = cp[IPOPT_OPTVAL];
|
|
if (opt == IPOPT_EOL)
|
|
break;
|
|
if (opt == IPOPT_NOP)
|
|
optlen = 1;
|
|
else {
|
|
#ifdef INVARIANTS
|
|
if (cnt < IPOPT_OLEN + sizeof(*cp))
|
|
break;
|
|
#endif
|
|
optlen = cp[IPOPT_OLEN];
|
|
#ifdef INVARIANTS
|
|
if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
|
|
break;
|
|
#endif
|
|
}
|
|
switch (opt) {
|
|
case IPOPT_RA:
|
|
#ifdef INVARIANTS
|
|
if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
|
|
(*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
|
|
break;
|
|
else
|
|
#endif
|
|
found_ra = 1;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
return (found_ra);
|
|
}
|