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freebsd-skq/sys/netinet/ip_input.c
Doug Rabson 6effc71332 Re-implement tcp and ip fragment reassembly to not store pointers in the 
ip header which can't work on alpha since pointers are too big.

Reviewed by: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
1998-08-24 07:47:39 +00:00

1593 lines
38 KiB
C
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/*
* Copyright (c) 1982, 1986, 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)ip_input.c 8.2 (Berkeley) 1/4/94
* $Id: ip_input.c,v 1.99 1998/08/23 03:07:14 wollman Exp $
* $ANA: ip_input.c,v 1.5 1996/09/18 14:34:59 wollman Exp $
*/
#define _IP_VHL
#include "opt_bootp.h"
#include "opt_ipfw.h"
#include "opt_ipdivert.h"
#include "opt_ipfilter.h"
#include <stddef.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/netisr.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <machine/in_cksum.h>
#include <sys/socketvar.h>
#ifdef IPFIREWALL
#include <netinet/ip_fw.h>
#endif
int rsvp_on = 0;
static int ip_rsvp_on;
struct socket *ip_rsvpd;
int ipforwarding = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_FORWARDING, forwarding, CTLFLAG_RW,
&ipforwarding, 0, "");
static int ipsendredirects = 1; /* XXX */
SYSCTL_INT(_net_inet_ip, IPCTL_SENDREDIRECTS, redirect, CTLFLAG_RW,
&ipsendredirects, 0, "");
int ip_defttl = IPDEFTTL;
SYSCTL_INT(_net_inet_ip, IPCTL_DEFTTL, ttl, CTLFLAG_RW,
&ip_defttl, 0, "");
static int ip_dosourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
&ip_dosourceroute, 0, "");
static int ip_acceptsourceroute = 0;
SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
CTLFLAG_RW, &ip_acceptsourceroute, 0, "");
#ifdef DIAGNOSTIC
static int ipprintfs = 0;
#endif
extern struct domain inetdomain;
extern struct protosw inetsw[];
u_char ip_protox[IPPROTO_MAX];
static int ipqmaxlen = IFQ_MAXLEN;
struct in_ifaddrhead in_ifaddrhead; /* first inet address */
struct ifqueue ipintrq;
SYSCTL_INT(_net_inet_ip, IPCTL_INTRQMAXLEN, intr_queue_maxlen, CTLFLAG_RD,
&ipintrq.ifq_maxlen, 0, "");
SYSCTL_INT(_net_inet_ip, IPCTL_INTRQDROPS, intr_queue_drops, CTLFLAG_RD,
&ipintrq.ifq_drops, 0, "");
struct ipstat ipstat;
SYSCTL_STRUCT(_net_inet_ip, IPCTL_STATS, stats, CTLFLAG_RD,
&ipstat, ipstat, "");
/* Packet reassembly stuff */
#define IPREASS_NHASH_LOG2 6
#define IPREASS_NHASH (1 << IPREASS_NHASH_LOG2)
#define IPREASS_HMASK (IPREASS_NHASH - 1)
#define IPREASS_HASH(x,y) \
((((x) & 0xF | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)
static struct ipq ipq[IPREASS_NHASH];
static int nipq = 0; /* total # of reass queues */
static int maxnipq;
#ifdef IPCTL_DEFMTU
SYSCTL_INT(_net_inet_ip, IPCTL_DEFMTU, mtu, CTLFLAG_RW,
&ip_mtu, 0, "");
#endif
#if !defined(COMPAT_IPFW) || COMPAT_IPFW == 1
#undef COMPAT_IPFW
#define COMPAT_IPFW 1
#else
#undef COMPAT_IPFW
#endif
#ifdef COMPAT_IPFW
#include <netinet/ip_fw.h>
/* Firewall hooks */
ip_fw_chk_t *ip_fw_chk_ptr;
ip_fw_ctl_t *ip_fw_ctl_ptr;
/* IP Network Address Translation (NAT) hooks */
ip_nat_t *ip_nat_ptr;
ip_nat_ctl_t *ip_nat_ctl_ptr;
#endif
#if defined(IPFILTER_LKM) || defined(IPFILTER)
int iplattach __P((void));
int (*fr_checkp) __P((struct ip *, int, struct ifnet *, int, struct mbuf **)) = NULL;
#endif
/*
* We need to save the IP options in case a protocol wants to respond
* to an incoming packet over the same route if the packet got here
* using IP source routing. This allows connection establishment and
* maintenance when the remote end is on a network that is not known
* to us.
*/
static int ip_nhops = 0;
static struct ip_srcrt {
struct in_addr dst; /* final destination */
char nop; /* one NOP to align */
char srcopt[IPOPT_OFFSET + 1]; /* OPTVAL, OLEN and OFFSET */
struct in_addr route[MAX_IPOPTLEN/sizeof(struct in_addr)];
} ip_srcrt;
#ifdef IPDIVERT
/*
* Shared variable between ip_input() and ip_reass() to communicate
* about which packets, once assembled from fragments, get diverted,
* and to which port.
*/
static u_short frag_divert_port;
#endif
struct sockaddr_in *ip_fw_fwd_addr;
static void save_rte __P((u_char *, struct in_addr));
static int ip_dooptions __P((struct mbuf *));
static void ip_forward __P((struct mbuf *, int));
static void ip_freef __P((struct ipq *));
static struct ip *
ip_reass __P((struct mbuf *, struct ipq *, struct ipq *));
static struct in_ifaddr *
ip_rtaddr __P((struct in_addr));
static void ipintr __P((void));
/*
* IP initialization: fill in IP protocol switch table.
* All protocols not implemented in kernel go to raw IP protocol handler.
*/
void
ip_init()
{
register struct protosw *pr;
register int i;
TAILQ_INIT(&in_ifaddrhead);
pr = pffindproto(PF_INET, IPPROTO_RAW, SOCK_RAW);
if (pr == 0)
panic("ip_init");
for (i = 0; i < IPPROTO_MAX; i++)
ip_protox[i] = pr - inetsw;
for (pr = inetdomain.dom_protosw;
pr < inetdomain.dom_protoswNPROTOSW; pr++)
if (pr->pr_domain->dom_family == PF_INET &&
pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW)
ip_protox[pr->pr_protocol] = pr - inetsw;
for (i = 0; i < IPREASS_NHASH; i++)
ipq[i].next = ipq[i].prev = &ipq[i];
maxnipq = nmbclusters/4;
ip_id = time_second & 0xffff;
ipintrq.ifq_maxlen = ipqmaxlen;
#ifdef IPFIREWALL
ip_fw_init();
#endif
#ifdef IPNAT
ip_nat_init();
#endif
#ifdef IPFILTER
iplattach();
#endif
}
static struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
static struct route ipforward_rt;
/*
* Ip input routine. Checksum and byte swap header. If fragmented
* try to reassemble. Process options. Pass to next level.
*/
void
ip_input(struct mbuf *m)
{
struct ip *ip;
struct ipq *fp;
struct ipqent *ipqe;
struct in_ifaddr *ia;
int i, hlen, mff;
u_short sum;
#ifdef DIAGNOSTIC
if (m == NULL || (m->m_flags & M_PKTHDR) == 0)
panic("ip_input no HDR");
#endif
/*
* If no IP addresses have been set yet but the interfaces
* are receiving, can't do anything with incoming packets yet.
* XXX This is broken! We should be able to receive broadcasts
* and multicasts even without any local addresses configured.
*/
if (TAILQ_EMPTY(&in_ifaddrhead))
goto bad;
ipstat.ips_total++;
if (m->m_pkthdr.len < sizeof(struct ip))
goto tooshort;
if (m->m_len < sizeof (struct ip) &&
(m = m_pullup(m, sizeof (struct ip))) == 0) {
ipstat.ips_toosmall++;
return;
}
ip = mtod(m, struct ip *);
if (IP_VHL_V(ip->ip_vhl) != IPVERSION) {
ipstat.ips_badvers++;
goto bad;
}
hlen = IP_VHL_HL(ip->ip_vhl) << 2;
if (hlen < sizeof(struct ip)) { /* minimum header length */
ipstat.ips_badhlen++;
goto bad;
}
if (hlen > m->m_len) {
if ((m = m_pullup(m, hlen)) == 0) {
ipstat.ips_badhlen++;
return;
}
ip = mtod(m, struct ip *);
}
if (hlen == sizeof(struct ip)) {
sum = in_cksum_hdr(ip);
} else {
sum = in_cksum(m, hlen);
}
if (sum) {
ipstat.ips_badsum++;
goto bad;
}
/*
* Convert fields to host representation.
*/
NTOHS(ip->ip_len);
if (ip->ip_len < hlen) {
ipstat.ips_badlen++;
goto bad;
}
NTOHS(ip->ip_id);
NTOHS(ip->ip_off);
/*
* Check that the amount of data in the buffers
* is as at least much as the IP header would have us expect.
* Trim mbufs if longer than we expect.
* Drop packet if shorter than we expect.
*/
if (m->m_pkthdr.len < ip->ip_len) {
tooshort:
ipstat.ips_tooshort++;
goto bad;
}
if (m->m_pkthdr.len > ip->ip_len) {
if (m->m_len == m->m_pkthdr.len) {
m->m_len = ip->ip_len;
m->m_pkthdr.len = ip->ip_len;
} else
m_adj(m, ip->ip_len - m->m_pkthdr.len);
}
/*
* IpHack's section.
* Right now when no processing on packet has done
* and it is still fresh out of network we do our black
* deals with it.
* - Firewall: deny/allow/divert
* - Xlate: translate packet's addr/port (NAT).
* - Wrap: fake packet's addr/port <unimpl.>
* - Encapsulate: put it in another IP and send out. <unimp.>
*/
#if defined(IPFILTER) || defined(IPFILTER_LKM)
/*
* Check if we want to allow this packet to be processed.
* Consider it to be bad if not.
*/
if (fr_checkp) {
struct mbuf *m1 = m;
if ((*fr_checkp)(ip, hlen, m->m_pkthdr.rcvif, 0, &m1) || !m1)
return;
ip = mtod(m = m1, struct ip *);
}
#endif
#ifdef COMPAT_IPFW
if (ip_fw_chk_ptr) {
u_int16_t port;
#ifdef IPFIREWALL_FORWARD
/*
* If we've been forwarded from the output side, then
* skip the firewall a second time
*/
if (ip_fw_fwd_addr)
goto ours;
#endif /* IPFIREWALL_FORWARD */
#ifdef IPDIVERT
port = (*ip_fw_chk_ptr)(&ip, hlen, NULL, &ip_divert_cookie,
&m, &ip_fw_fwd_addr);
if (port) {
/* Divert packet */
frag_divert_port = port;
goto ours;
}
#else /* !DIVERT */
/*
* If ipfw says divert, we have to just drop packet
* Use port as a dummy argument.
*/
port = 0;
if ((*ip_fw_chk_ptr)(&ip, hlen, NULL, &port,
&m, &ip_fw_fwd_addr)) {
m_freem(m);
m = NULL;
}
#endif /* !DIVERT */
if (!m)
return;
}
if (ip_nat_ptr && !(*ip_nat_ptr)(&ip, &m, m->m_pkthdr.rcvif, IP_NAT_IN))
return;
#endif /* !COMPAT_IPFW */
/*
* Process options and, if not destined for us,
* ship it on. ip_dooptions returns 1 when an
* error was detected (causing an icmp message
* to be sent and the original packet to be freed).
*/
ip_nhops = 0; /* for source routed packets */
if (hlen > sizeof (struct ip) && ip_dooptions(m))
return;
/* greedy RSVP, snatches any PATH packet of the RSVP protocol and no
* matter if it is destined to another node, or whether it is
* a multicast one, RSVP wants it! and prevents it from being forwarded
* anywhere else. Also checks if the rsvp daemon is running before
* grabbing the packet.
*/
if (rsvp_on && ip->ip_p==IPPROTO_RSVP)
goto ours;
/*
* Check our list of addresses, to see if the packet is for us.
*/
for (ia = TAILQ_FIRST(&in_ifaddrhead); ia;
ia = TAILQ_NEXT(ia, ia_link)) {
#define satosin(sa) ((struct sockaddr_in *)(sa))
if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_dst.s_addr)
goto ours;
#ifdef BOOTP_COMPAT
if (IA_SIN(ia)->sin_addr.s_addr == INADDR_ANY)
goto ours;
#endif
#ifdef IPFIREWALL_FORWARD
/*
* If the addr to forward to is one of ours, we pretend to
* be the destination for this packet.
*/
if (ip_fw_fwd_addr != NULL &&
IA_SIN(ia)->sin_addr.s_addr ==
ip_fw_fwd_addr->sin_addr.s_addr)
goto ours;
#endif
if (ia->ia_ifp && ia->ia_ifp->if_flags & IFF_BROADCAST) {
if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
ip->ip_dst.s_addr)
goto ours;
if (ip->ip_dst.s_addr == ia->ia_netbroadcast.s_addr)
goto ours;
}
}
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
struct in_multi *inm;
if (ip_mrouter) {
/*
* If we are acting as a multicast router, all
* incoming multicast packets are passed to the
* kernel-level multicast forwarding function.
* The packet is returned (relatively) intact; if
* ip_mforward() returns a non-zero value, the packet
* must be discarded, else it may be accepted below.
*
* (The IP ident field is put in the same byte order
* as expected when ip_mforward() is called from
* ip_output().)
*/
ip->ip_id = htons(ip->ip_id);
if (ip_mforward(ip, m->m_pkthdr.rcvif, m, 0) != 0) {
ipstat.ips_cantforward++;
m_freem(m);
return;
}
ip->ip_id = ntohs(ip->ip_id);
/*
* The process-level routing demon needs to receive
* all multicast IGMP packets, whether or not this
* host belongs to their destination groups.
*/
if (ip->ip_p == IPPROTO_IGMP)
goto ours;
ipstat.ips_forward++;
}
/*
* See if we belong to the destination multicast group on the
* arrival interface.
*/
IN_LOOKUP_MULTI(ip->ip_dst, m->m_pkthdr.rcvif, inm);
if (inm == NULL) {
ipstat.ips_notmember++;
m_freem(m);
return;
}
goto ours;
}
if (ip->ip_dst.s_addr == (u_long)INADDR_BROADCAST)
goto ours;
if (ip->ip_dst.s_addr == INADDR_ANY)
goto ours;
/*
* Not for us; forward if possible and desirable.
*/
if (ipforwarding == 0) {
ipstat.ips_cantforward++;
m_freem(m);
} else
ip_forward(m, 0);
return;
ours:
/*
* If offset or IP_MF are set, must reassemble.
* Otherwise, nothing need be done.
* (We could look in the reassembly queue to see
* if the packet was previously fragmented,
* but it's not worth the time; just let them time out.)
*/
if (ip->ip_off & (IP_MF | IP_OFFMASK | IP_RF)) {
if (m->m_flags & M_EXT) { /* XXX */
if ((m = m_pullup(m, sizeof (struct ip))) == 0) {
ipstat.ips_toosmall++;
#ifdef IPDIVERT
frag_divert_port = 0;
ip_divert_cookie = 0;
#endif
return;
}
ip = mtod(m, struct ip *);
}
sum = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
/*
* Look for queue of fragments
* of this datagram.
*/
for (fp = ipq[sum].next; fp != &ipq[sum]; fp = fp->next)
if (ip->ip_id == fp->ipq_id &&
ip->ip_src.s_addr == fp->ipq_src.s_addr &&
ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
ip->ip_p == fp->ipq_p)
goto found;
fp = 0;
/* check if there's a place for the new queue */
if (nipq > maxnipq) {
/*
* drop something from the tail of the current queue
* before proceeding further
*/
if (ipq[sum].prev == &ipq[sum]) { /* gak */
for (i = 0; i < IPREASS_NHASH; i++) {
if (ipq[i].prev != &ipq[i]) {
ip_freef(ipq[i].prev);
break;
}
}
} else
ip_freef(ipq[sum].prev);
}
found:
/*
* Adjust ip_len to not reflect header,
* set ip_mff if more fragments are expected,
* convert offset of this to bytes.
*/
ip->ip_len -= hlen;
mff = (ip->ip_off & IP_MF) != 0;
if (mff) {
/*
* Make sure that fragments have a data length
* that's a non-zero multiple of 8 bytes.
*/
if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0) {
ipstat.ips_toosmall++; /* XXX */
goto bad;
}
m->m_flags |= M_FRAG;
}
ip->ip_off <<= 3;
/*
* If datagram marked as having more fragments
* or if this is not the first fragment,
* attempt reassembly; if it succeeds, proceed.
*/
if (mff || ip->ip_off) {
ipstat.ips_fragments++;
m->m_pkthdr.header = ip;
ip = ip_reass(m, fp, &ipq[sum]);
if (ip == 0) {
#ifdef IPFIREWALL_FORWARD
ip_fw_fwd_addr = NULL;
#endif
return;
}
/* Get the length of the reassembled packets header */
hlen = IP_VHL_HL(ip->ip_vhl) << 2;
ipstat.ips_reassembled++;
m = dtom(ip);
#ifdef IPDIVERT
if (frag_divert_port) {
ip->ip_len += hlen;
HTONS(ip->ip_len);
HTONS(ip->ip_off);
HTONS(ip->ip_id);
ip->ip_sum = 0;
ip->ip_sum = in_cksum_hdr(ip);
NTOHS(ip->ip_id);
NTOHS(ip->ip_off);
NTOHS(ip->ip_len);
ip->ip_len -= hlen;
}
#endif
} else
if (fp)
ip_freef(fp);
} else
ip->ip_len -= hlen;
#ifdef IPDIVERT
/*
* Divert reassembled packets to the divert protocol if required
* If divert port is null then cookie should be too,
* so we shouldn't need to clear them here. Assume ip_divert does so.
*/
if (frag_divert_port) {
ipstat.ips_delivered++;
ip_divert_port = frag_divert_port;
frag_divert_port = 0;
(*inetsw[ip_protox[IPPROTO_DIVERT]].pr_input)(m, hlen);
return;
}
/* Don't let packets divert themselves */
if (ip->ip_p == IPPROTO_DIVERT) {
ipstat.ips_noproto++;
goto bad;
}
#endif
/*
* Switch out to protocol's input routine.
*/
ipstat.ips_delivered++;
(*inetsw[ip_protox[ip->ip_p]].pr_input)(m, hlen);
#ifdef IPFIREWALL_FORWARD
ip_fw_fwd_addr = NULL; /* tcp needed it */
#endif
return;
bad:
#ifdef IPFIREWALL_FORWARD
ip_fw_fwd_addr = NULL;
#endif
m_freem(m);
}
/*
* IP software interrupt routine - to go away sometime soon
*/
static void
ipintr(void)
{
int s;
struct mbuf *m;
while(1) {
s = splimp();
IF_DEQUEUE(&ipintrq, m);
splx(s);
if (m == 0)
return;
ip_input(m);
}
}
NETISR_SET(NETISR_IP, ipintr);
/*
* Take incoming datagram fragment and try to
* reassemble it into whole datagram. If a chain for
* reassembly of this datagram already exists, then it
* is given as fp; otherwise have to make a chain.
*/
static struct ip *
ip_reass(m, fp, where)
register struct mbuf *m;
register struct ipq *fp;
struct ipq *where;
{
struct ip *ip = mtod(m, struct ip *);
register struct mbuf *p = 0, *q, *nq;
struct mbuf *t;
int hlen = IP_VHL_HL(ip->ip_vhl) << 2;
int i, next;
/*
* Presence of header sizes in mbufs
* would confuse code below.
*/
m->m_data += hlen;
m->m_len -= hlen;
/*
* If first fragment to arrive, create a reassembly queue.
*/
if (fp == 0) {
if ((t = m_get(M_DONTWAIT, MT_FTABLE)) == NULL)
goto dropfrag;
fp = mtod(t, struct ipq *);
insque(fp, where);
nipq++;
fp->ipq_ttl = IPFRAGTTL;
fp->ipq_p = ip->ip_p;
fp->ipq_id = ip->ip_id;
fp->ipq_src = ip->ip_src;
fp->ipq_dst = ip->ip_dst;
fp->ipq_frags = 0;
#ifdef IPDIVERT
fp->ipq_divert = 0;
fp->ipq_div_cookie = 0;
#endif
q = 0;
goto insert;
}
#define GETIP(m) ((struct ip*)((m)->m_pkthdr.header))
/*
* Find a segment which begins after this one does.
*/
for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
if (GETIP(q)->ip_off > ip->ip_off)
break;
/*
* If there is a preceding segment, it may provide some of
* our data already. If so, drop the data from the incoming
* segment. If it provides all of our data, drop us.
*/
if (p) {
i = GETIP(p)->ip_off + GETIP(p)->ip_len - ip->ip_off;
if (i > 0) {
if (i >= ip->ip_len)
goto dropfrag;
m_adj(dtom(ip), i);
ip->ip_off += i;
ip->ip_len -= i;
}
}
/*
* While we overlap succeeding segments trim them or,
* if they are completely covered, dequeue them.
*/
for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
p = q, q = nq) {
i = (ip->ip_off + ip->ip_len) -
GETIP(q)->ip_off;
if (i < GETIP(q)->ip_len) {
GETIP(q)->ip_len -= i;
GETIP(q)->ip_off += i;
m_adj(q, i);
break;
}
nq = q->m_nextpkt;
if (p)
p->m_nextpkt = nq;
else
fp->ipq_frags = nq;
m_freem(q);
}
insert:
#ifdef IPDIVERT
/*
* Any fragment diverting causes the whole packet to divert
*/
if (frag_divert_port) {
fp->ipq_divert = frag_divert_port;
fp->ipq_div_cookie = ip_divert_cookie;
}
frag_divert_port = 0;
ip_divert_cookie = 0;
#endif
/*
* Stick new segment in its place;
* check for complete reassembly.
*/
if (p == NULL) {
m->m_nextpkt = fp->ipq_frags;
fp->ipq_frags = m;
} else {
m->m_nextpkt = p->m_nextpkt;
p->m_nextpkt = m;
}
next = 0;
for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt) {
if (GETIP(q)->ip_off != next)
return (0);
next += GETIP(q)->ip_len;
}
/* Make sure the last packet didn't have the IP_MF flag */
if (p->m_flags & M_FRAG)
return (0);
/*
* Reassembly is complete. Make sure the packet is a sane size.
*/
q = fp->ipq_frags;
ip = GETIP(q);
if (next + (IP_VHL_HL(ip->ip_vhl) << 2) > IP_MAXPACKET) {
ipstat.ips_toolong++;
ip_freef(fp);
return (0);
}
/*
* Concatenate fragments.
*/
m = q;
t = m->m_next;
m->m_next = 0;
m_cat(m, t);
nq = q->m_nextpkt;
for (q = nq; q != NULL; q = nq) {
nq = q->m_nextpkt;
m_cat(m, q);
}
#ifdef IPDIVERT
/*
* extract divert port for packet, if any
*/
frag_divert_port = fp->ipq_divert;
ip_divert_cookie = fp->ipq_div_cookie;
#endif
/*
* Create header for new ip packet by
* modifying header of first packet;
* dequeue and discard fragment reassembly header.
* Make header visible.
*/
ip->ip_len = next;
ip->ip_src = fp->ipq_src;
ip->ip_dst = fp->ipq_dst;
remque(fp);
nipq--;
(void) m_free(dtom(fp));
m->m_len += (IP_VHL_HL(ip->ip_vhl) << 2);
m->m_data -= (IP_VHL_HL(ip->ip_vhl) << 2);
/* some debugging cruft by sklower, below, will go away soon */
if (m->m_flags & M_PKTHDR) { /* XXX this should be done elsewhere */
register int plen = 0;
for (t = m; m; m = m->m_next)
plen += m->m_len;
t->m_pkthdr.len = plen;
}
return (ip);
dropfrag:
#ifdef IPDIVERT
frag_divert_port = 0;
ip_divert_cookie = 0;
#endif
ipstat.ips_fragdropped++;
m_freem(m);
return (0);
#undef GETIP
}
/*
* Free a fragment reassembly header and all
* associated datagrams.
*/
static void
ip_freef(fp)
struct ipq *fp;
{
register struct mbuf *q;
while (fp->ipq_frags) {
q = fp->ipq_frags;
fp->ipq_frags = q->m_nextpkt;
m_freem(q);
}
remque(fp);
(void) m_free(dtom(fp));
nipq--;
}
/*
* IP timer processing;
* if a timer expires on a reassembly
* queue, discard it.
*/
void
ip_slowtimo()
{
register struct ipq *fp;
int s = splnet();
int i;
for (i = 0; i < IPREASS_NHASH; i++) {
fp = ipq[i].next;
if (fp == 0)
continue;
while (fp != &ipq[i]) {
--fp->ipq_ttl;
fp = fp->next;
if (fp->prev->ipq_ttl == 0) {
ipstat.ips_fragtimeout++;
ip_freef(fp->prev);
}
}
}
ipflow_slowtimo();
splx(s);
}
/*
* Drain off all datagram fragments.
*/
void
ip_drain()
{
int i;
for (i = 0; i < IPREASS_NHASH; i++) {
while (ipq[i].next != &ipq[i]) {
ipstat.ips_fragdropped++;
ip_freef(ipq[i].next);
}
}
in_rtqdrain();
}
/*
* Do option processing on a datagram,
* possibly discarding it if bad options are encountered,
* or forwarding it if source-routed.
* Returns 1 if packet has been forwarded/freed,
* 0 if the packet should be processed further.
*/
static int
ip_dooptions(m)
struct mbuf *m;
{
register struct ip *ip = mtod(m, struct ip *);
register u_char *cp;
register struct ip_timestamp *ipt;
register struct in_ifaddr *ia;
int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
struct in_addr *sin, dst;
n_time ntime;
dst = ip->ip_dst;
cp = (u_char *)(ip + 1);
cnt = (IP_VHL_HL(ip->ip_vhl) << 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 {
optlen = cp[IPOPT_OLEN];
if (optlen <= 0 || optlen > cnt) {
code = &cp[IPOPT_OLEN] - (u_char *)ip;
goto bad;
}
}
switch (opt) {
default:
break;
/*
* Source routing with record.
* Find interface with current destination address.
* If none on this machine then drop if strictly routed,
* or do nothing if loosely routed.
* Record interface address and bring up next address
* component. If strictly routed make sure next
* address is on directly accessible net.
*/
case IPOPT_LSRR:
case IPOPT_SSRR:
if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
code = &cp[IPOPT_OFFSET] - (u_char *)ip;
goto bad;
}
ipaddr.sin_addr = ip->ip_dst;
ia = (struct in_ifaddr *)
ifa_ifwithaddr((struct sockaddr *)&ipaddr);
if (ia == 0) {
if (opt == IPOPT_SSRR) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_SRCFAIL;
goto bad;
}
if (!ip_dosourceroute)
goto nosourcerouting;
/*
* Loose routing, and not at next destination
* yet; nothing to do except forward.
*/
break;
}
off--; /* 0 origin */
if (off > optlen - sizeof(struct in_addr)) {
/*
* End of source route. Should be for us.
*/
if (!ip_acceptsourceroute)
goto nosourcerouting;
save_rte(cp, ip->ip_src);
break;
}
if (!ip_dosourceroute) {
if (ipforwarding) {
char buf[16]; /* aaa.bbb.ccc.ddd\0 */
/*
* Acting as a router, so generate ICMP
*/
nosourcerouting:
strcpy(buf, inet_ntoa(ip->ip_dst));
log(LOG_WARNING,
"attempted source route from %s to %s\n",
inet_ntoa(ip->ip_src), buf);
type = ICMP_UNREACH;
code = ICMP_UNREACH_SRCFAIL;
goto bad;
} else {
/*
* Not acting as a router, so silently drop.
*/
ipstat.ips_cantforward++;
m_freem(m);
return (1);
}
}
/*
* locate outgoing interface
*/
(void)memcpy(&ipaddr.sin_addr, cp + off,
sizeof(ipaddr.sin_addr));
if (opt == IPOPT_SSRR) {
#define INA struct in_ifaddr *
#define SA struct sockaddr *
if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == 0)
ia = (INA)ifa_ifwithnet((SA)&ipaddr);
} else
ia = ip_rtaddr(ipaddr.sin_addr);
if (ia == 0) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_SRCFAIL;
goto bad;
}
ip->ip_dst = ipaddr.sin_addr;
(void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
sizeof(struct in_addr));
cp[IPOPT_OFFSET] += sizeof(struct in_addr);
/*
* Let ip_intr's mcast routing check handle mcast pkts
*/
forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
break;
case IPOPT_RR:
if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
code = &cp[IPOPT_OFFSET] - (u_char *)ip;
goto bad;
}
/*
* If no space remains, ignore.
*/
off--; /* 0 origin */
if (off > optlen - sizeof(struct in_addr))
break;
(void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
sizeof(ipaddr.sin_addr));
/*
* locate outgoing interface; if we're the destination,
* use the incoming interface (should be same).
*/
if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == 0 &&
(ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_HOST;
goto bad;
}
(void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
sizeof(struct in_addr));
cp[IPOPT_OFFSET] += sizeof(struct in_addr);
break;
case IPOPT_TS:
code = cp - (u_char *)ip;
ipt = (struct ip_timestamp *)cp;
if (ipt->ipt_len < 5)
goto bad;
if (ipt->ipt_ptr > ipt->ipt_len - sizeof(int32_t)) {
if (++ipt->ipt_oflw == 0)
goto bad;
break;
}
sin = (struct in_addr *)(cp + ipt->ipt_ptr - 1);
switch (ipt->ipt_flg) {
case IPOPT_TS_TSONLY:
break;
case IPOPT_TS_TSANDADDR:
if (ipt->ipt_ptr - 1 + sizeof(n_time) +
sizeof(struct in_addr) > ipt->ipt_len)
goto bad;
ipaddr.sin_addr = dst;
ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
m->m_pkthdr.rcvif);
if (ia == 0)
continue;
(void)memcpy(sin, &IA_SIN(ia)->sin_addr,
sizeof(struct in_addr));
ipt->ipt_ptr += sizeof(struct in_addr);
break;
case IPOPT_TS_PRESPEC:
if (ipt->ipt_ptr - 1 + sizeof(n_time) +
sizeof(struct in_addr) > ipt->ipt_len)
goto bad;
(void)memcpy(&ipaddr.sin_addr, sin,
sizeof(struct in_addr));
if (ifa_ifwithaddr((SA)&ipaddr) == 0)
continue;
ipt->ipt_ptr += sizeof(struct in_addr);
break;
default:
goto bad;
}
ntime = iptime();
(void)memcpy(cp + ipt->ipt_ptr - 1, &ntime,
sizeof(n_time));
ipt->ipt_ptr += sizeof(n_time);
}
}
if (forward && ipforwarding) {
ip_forward(m, 1);
return (1);
}
return (0);
bad:
ip->ip_len -= IP_VHL_HL(ip->ip_vhl) << 2; /* XXX icmp_error adds in hdr length */
icmp_error(m, type, code, 0, 0);
ipstat.ips_badoptions++;
return (1);
}
/*
* Given address of next destination (final or next hop),
* return internet address info of interface to be used to get there.
*/
static struct in_ifaddr *
ip_rtaddr(dst)
struct in_addr dst;
{
register struct sockaddr_in *sin;
sin = (struct sockaddr_in *) &ipforward_rt.ro_dst;
if (ipforward_rt.ro_rt == 0 || dst.s_addr != sin->sin_addr.s_addr) {
if (ipforward_rt.ro_rt) {
RTFREE(ipforward_rt.ro_rt);
ipforward_rt.ro_rt = 0;
}
sin->sin_family = AF_INET;
sin->sin_len = sizeof(*sin);
sin->sin_addr = dst;
rtalloc_ign(&ipforward_rt, RTF_PRCLONING);
}
if (ipforward_rt.ro_rt == 0)
return ((struct in_ifaddr *)0);
return ((struct in_ifaddr *) ipforward_rt.ro_rt->rt_ifa);
}
/*
* Save incoming source route for use in replies,
* to be picked up later by ip_srcroute if the receiver is interested.
*/
void
save_rte(option, dst)
u_char *option;
struct in_addr dst;
{
unsigned olen;
olen = option[IPOPT_OLEN];
#ifdef DIAGNOSTIC
if (ipprintfs)
printf("save_rte: olen %d\n", olen);
#endif
if (olen > sizeof(ip_srcrt) - (1 + sizeof(dst)))
return;
bcopy(option, ip_srcrt.srcopt, olen);
ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
ip_srcrt.dst = dst;
}
/*
* Retrieve incoming source route for use in replies,
* in the same form used by setsockopt.
* The first hop is placed before the options, will be removed later.
*/
struct mbuf *
ip_srcroute()
{
register struct in_addr *p, *q;
register struct mbuf *m;
if (ip_nhops == 0)
return ((struct mbuf *)0);
m = m_get(M_DONTWAIT, MT_HEADER);
if (m == 0)
return ((struct mbuf *)0);
#define OPTSIZ (sizeof(ip_srcrt.nop) + sizeof(ip_srcrt.srcopt))
/* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
m->m_len = ip_nhops * sizeof(struct in_addr) + sizeof(struct in_addr) +
OPTSIZ;
#ifdef DIAGNOSTIC
if (ipprintfs)
printf("ip_srcroute: nhops %d mlen %d", ip_nhops, m->m_len);
#endif
/*
* First save first hop for return route
*/
p = &ip_srcrt.route[ip_nhops - 1];
*(mtod(m, struct in_addr *)) = *p--;
#ifdef DIAGNOSTIC
if (ipprintfs)
printf(" hops %lx", ntohl(mtod(m, struct in_addr *)->s_addr));
#endif
/*
* Copy option fields and padding (nop) to mbuf.
*/
ip_srcrt.nop = IPOPT_NOP;
ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
(void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
&ip_srcrt.nop, OPTSIZ);
q = (struct in_addr *)(mtod(m, caddr_t) +
sizeof(struct in_addr) + OPTSIZ);
#undef OPTSIZ
/*
* Record return path as an IP source route,
* reversing the path (pointers are now aligned).
*/
while (p >= ip_srcrt.route) {
#ifdef DIAGNOSTIC
if (ipprintfs)
printf(" %lx", ntohl(q->s_addr));
#endif
*q++ = *p--;
}
/*
* Last hop goes to final destination.
*/
*q = ip_srcrt.dst;
#ifdef DIAGNOSTIC
if (ipprintfs)
printf(" %lx\n", ntohl(q->s_addr));
#endif
return (m);
}
/*
* Strip out IP options, at higher
* level protocol in the kernel.
* Second argument is buffer to which options
* will be moved, and return value is their length.
* XXX should be deleted; last arg currently ignored.
*/
void
ip_stripoptions(m, mopt)
register struct mbuf *m;
struct mbuf *mopt;
{
register int i;
struct ip *ip = mtod(m, struct ip *);
register caddr_t opts;
int olen;
olen = (IP_VHL_HL(ip->ip_vhl) << 2) - sizeof (struct ip);
opts = (caddr_t)(ip + 1);
i = m->m_len - (sizeof (struct ip) + olen);
bcopy(opts + olen, opts, (unsigned)i);
m->m_len -= olen;
if (m->m_flags & M_PKTHDR)
m->m_pkthdr.len -= olen;
ip->ip_vhl = IP_MAKE_VHL(IPVERSION, sizeof(struct ip) >> 2);
}
u_char inetctlerrmap[PRC_NCMDS] = {
0, 0, 0, 0,
0, EMSGSIZE, EHOSTDOWN, EHOSTUNREACH,
EHOSTUNREACH, EHOSTUNREACH, ECONNREFUSED, ECONNREFUSED,
EMSGSIZE, EHOSTUNREACH, 0, 0,
0, 0, 0, 0,
ENOPROTOOPT
};
/*
* Forward a packet. If some error occurs return the sender
* an icmp packet. Note we can't always generate a meaningful
* icmp message because icmp doesn't have a large enough repertoire
* of codes and types.
*
* If not forwarding, just drop the packet. This could be confusing
* if ipforwarding was zero but some routing protocol was advancing
* us as a gateway to somewhere. However, we must let the routing
* protocol deal with that.
*
* The srcrt parameter indicates whether the packet is being forwarded
* via a source route.
*/
static void
ip_forward(m, srcrt)
struct mbuf *m;
int srcrt;
{
register struct ip *ip = mtod(m, struct ip *);
register struct sockaddr_in *sin;
register struct rtentry *rt;
int error, type = 0, code = 0;
struct mbuf *mcopy;
n_long dest;
struct ifnet *destifp;
dest = 0;
#ifdef DIAGNOSTIC
if (ipprintfs)
printf("forward: src %lx dst %lx ttl %x\n",
(u_long)ip->ip_src.s_addr, (u_long)ip->ip_dst.s_addr,
ip->ip_ttl);
#endif
if (m->m_flags & M_BCAST || in_canforward(ip->ip_dst) == 0) {
ipstat.ips_cantforward++;
m_freem(m);
return;
}
HTONS(ip->ip_id);
if (ip->ip_ttl <= IPTTLDEC) {
icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, dest, 0);
return;
}
ip->ip_ttl -= IPTTLDEC;
sin = (struct sockaddr_in *)&ipforward_rt.ro_dst;
if ((rt = ipforward_rt.ro_rt) == 0 ||
ip->ip_dst.s_addr != sin->sin_addr.s_addr) {
if (ipforward_rt.ro_rt) {
RTFREE(ipforward_rt.ro_rt);
ipforward_rt.ro_rt = 0;
}
sin->sin_family = AF_INET;
sin->sin_len = sizeof(*sin);
sin->sin_addr = ip->ip_dst;
rtalloc_ign(&ipforward_rt, RTF_PRCLONING);
if (ipforward_rt.ro_rt == 0) {
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, dest, 0);
return;
}
rt = ipforward_rt.ro_rt;
}
/*
* Save at most 64 bytes of the packet in case
* we need to generate an ICMP message to the src.
*/
mcopy = m_copy(m, 0, imin((int)ip->ip_len, 64));
/*
* If forwarding packet using same interface that it came in on,
* perhaps should send a redirect to sender to shortcut a hop.
* Only send redirect if source is sending directly to us,
* and if packet was not source routed (or has any options).
* Also, don't send redirect if forwarding using a default route
* or a route modified by a redirect.
*/
#define satosin(sa) ((struct sockaddr_in *)(sa))
if (rt->rt_ifp == m->m_pkthdr.rcvif &&
(rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0 &&
satosin(rt_key(rt))->sin_addr.s_addr != 0 &&
ipsendredirects && !srcrt) {
#define RTA(rt) ((struct in_ifaddr *)(rt->rt_ifa))
u_long src = ntohl(ip->ip_src.s_addr);
if (RTA(rt) &&
(src & RTA(rt)->ia_subnetmask) == RTA(rt)->ia_subnet) {
if (rt->rt_flags & RTF_GATEWAY)
dest = satosin(rt->rt_gateway)->sin_addr.s_addr;
else
dest = ip->ip_dst.s_addr;
/* Router requirements says to only send host redirects */
type = ICMP_REDIRECT;
code = ICMP_REDIRECT_HOST;
#ifdef DIAGNOSTIC
if (ipprintfs)
printf("redirect (%d) to %lx\n", code, (u_long)dest);
#endif
}
}
error = ip_output(m, (struct mbuf *)0, &ipforward_rt,
IP_FORWARDING, 0);
if (error)
ipstat.ips_cantforward++;
else {
ipstat.ips_forward++;
if (type)
ipstat.ips_redirectsent++;
else {
if (mcopy) {
ipflow_create(&ipforward_rt, mcopy);
m_freem(mcopy);
}
return;
}
}
if (mcopy == NULL)
return;
destifp = NULL;
switch (error) {
case 0: /* forwarded, but need redirect */
/* type, code set above */
break;
case ENETUNREACH: /* shouldn't happen, checked above */
case EHOSTUNREACH:
case ENETDOWN:
case EHOSTDOWN:
default:
type = ICMP_UNREACH;
code = ICMP_UNREACH_HOST;
break;
case EMSGSIZE:
type = ICMP_UNREACH;
code = ICMP_UNREACH_NEEDFRAG;
if (ipforward_rt.ro_rt)
destifp = ipforward_rt.ro_rt->rt_ifp;
ipstat.ips_cantfrag++;
break;
case ENOBUFS:
type = ICMP_SOURCEQUENCH;
code = 0;
break;
}
icmp_error(mcopy, type, code, dest, destifp);
}
void
ip_savecontrol(inp, mp, ip, m)
register struct inpcb *inp;
register struct mbuf **mp;
register struct ip *ip;
register struct mbuf *m;
{
if (inp->inp_socket->so_options & SO_TIMESTAMP) {
struct timeval tv;
microtime(&tv);
*mp = sbcreatecontrol((caddr_t) &tv, sizeof(tv),
SCM_TIMESTAMP, SOL_SOCKET);
if (*mp)
mp = &(*mp)->m_next;
}
if (inp->inp_flags & INP_RECVDSTADDR) {
*mp = sbcreatecontrol((caddr_t) &ip->ip_dst,
sizeof(struct in_addr), IP_RECVDSTADDR, IPPROTO_IP);
if (*mp)
mp = &(*mp)->m_next;
}
#ifdef notyet
/* XXX
* Moving these out of udp_input() made them even more broken
* than they already were.
*/
/* options were tossed already */
if (inp->inp_flags & INP_RECVOPTS) {
*mp = sbcreatecontrol((caddr_t) opts_deleted_above,
sizeof(struct in_addr), IP_RECVOPTS, IPPROTO_IP);
if (*mp)
mp = &(*mp)->m_next;
}
/* ip_srcroute doesn't do what we want here, need to fix */
if (inp->inp_flags & INP_RECVRETOPTS) {
*mp = sbcreatecontrol((caddr_t) ip_srcroute(),
sizeof(struct in_addr), IP_RECVRETOPTS, IPPROTO_IP);
if (*mp)
mp = &(*mp)->m_next;
}
#endif
if (inp->inp_flags & INP_RECVIF) {
struct ifnet *ifp;
struct sdlbuf {
struct sockaddr_dl sdl;
u_char pad[32];
} sdlbuf;
struct sockaddr_dl *sdp;
struct sockaddr_dl *sdl2 = &sdlbuf.sdl;
if (((ifp = m->m_pkthdr.rcvif))
&& ( ifp->if_index && (ifp->if_index <= if_index))) {
sdp = (struct sockaddr_dl *)(ifnet_addrs
[ifp->if_index - 1]->ifa_addr);
/*
* Change our mind and don't try copy.
*/
if ((sdp->sdl_family != AF_LINK)
|| (sdp->sdl_len > sizeof(sdlbuf))) {
goto makedummy;
}
bcopy(sdp, sdl2, sdp->sdl_len);
} else {
makedummy:
sdl2->sdl_len
= offsetof(struct sockaddr_dl, sdl_data[0]);
sdl2->sdl_family = AF_LINK;
sdl2->sdl_index = 0;
sdl2->sdl_nlen = sdl2->sdl_alen = sdl2->sdl_slen = 0;
}
*mp = sbcreatecontrol((caddr_t) sdl2, sdl2->sdl_len,
IP_RECVIF, IPPROTO_IP);
if (*mp)
mp = &(*mp)->m_next;
}
}
int
ip_rsvp_init(struct socket *so)
{
if (so->so_type != SOCK_RAW ||
so->so_proto->pr_protocol != IPPROTO_RSVP)
return EOPNOTSUPP;
if (ip_rsvpd != NULL)
return EADDRINUSE;
ip_rsvpd = so;
/*
* This may seem silly, but we need to be sure we don't over-increment
* the RSVP counter, in case something slips up.
*/
if (!ip_rsvp_on) {
ip_rsvp_on = 1;
rsvp_on++;
}
return 0;
}
int
ip_rsvp_done(void)
{
ip_rsvpd = NULL;
/*
* This may seem silly, but we need to be sure we don't over-decrement
* the RSVP counter, in case something slips up.
*/
if (ip_rsvp_on) {
ip_rsvp_on = 0;
rsvp_on--;
}
return 0;
}
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