2.11BSD/sys/netinet/ip_input.c
/*
* Copyright (c) 1982, 1986 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that this notice is preserved and that due credit is given
* to the University of California at Berkeley. The name of the University
* may not be used to endorse or promote products derived from this
* software without specific prior written permission. This software
* is provided ``as is'' without express or implied warranty.
*
* @(#)ip_input.c 7.9.2 (2.11BSD GTE) 1995/10/09
*/
#include "param.h"
#include "systm.h"
#include "mbuf.h"
#include "domain.h"
#include "protosw.h"
#include "socket.h"
#include "errno.h"
#include "time.h"
#include "kernel.h"
#include "../net/if.h"
#include "../net/route.h"
#include "in.h"
#include "in_pcb.h"
#include "in_systm.h"
#include "in_var.h"
#include "ip.h"
#include "ip_var.h"
#include "ip_icmp.h"
#include "tcp.h"
extern int ipforwarding, ipsendredirects, ipforward_srcrt, ip_defttl;
u_char ip_protox[IPPROTO_MAX];
int ipqmaxlen = IFQ_MAXLEN;
int ipprintfs = 0;
struct in_ifaddr *in_ifaddr; /* first inet address */
/*
* 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.
*/
int ip_nhops = 0;
static struct ip_srcrt {
char nop; /* one NOP to align */
char srcopt[IPOPT_OFFSET + 1]; /* OPTVAL, OLEN and OFFSET */
struct in_addr route[MAX_IPOPTLEN];
} ip_srcrt;
/*
* IP initialization: fill in IP protocol switch table.
* All protocols not implemented in kernel go to raw IP protocol handler.
*/
ip_init()
{
register struct protosw *pr;
register int i;
extern struct timeval time;
struct timeval nettime;
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;
ipq.next = ipq.prev = &ipq;
cpfromkern(&time, &nettime, sizeof (struct timeval));
ip_id = nettime.tv_sec & 0xffffL;
ipintrq.ifq_maxlen = ipqmaxlen;
}
u_char ipcksum = 1;
struct ip *ip_reass();
struct sockaddr_in ipaddr = { AF_INET };
struct route ipforward_rt;
/*
* Ip input routine. Checksum and byte swap header. If fragmented
* try to reassamble. If complete and fragment queue exists, discard.
* Process options. Pass to next level.
*/
ipintr()
{
register struct ip *ip;
register struct mbuf *m;
struct mbuf *m0;
register int i;
register struct ipq *fp;
register struct in_ifaddr *ia;
struct ifnet *ifp;
int hlen, s;
next:
/*
* Get next datagram off input queue and get IP header
* in first mbuf.
*/
s = splimp();
IF_DEQUEUEIF(&ipintrq, m, ifp);
splx(s);
if (m == 0)
return;
/*
* If no IP addresses have been set yet but the interfaces
* are receiving, can't do anything with incoming packets yet.
*/
if (in_ifaddr == NULL)
goto bad;
ipstat.ips_total++;
if ((m->m_off > MMAXOFF || m->m_len < sizeof (struct ip)) &&
(m = m_pullup(m, sizeof (struct ip))) == 0) {
ipstat.ips_toosmall++;
goto next;
}
ip = mtod(m, struct ip *);
hlen = ip->ip_hl << 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++;
goto next;
}
ip = mtod(m, struct ip *);
}
if (ipcksum)
if (ip->ip_sum = in_cksum(m, hlen)) {
ipstat.ips_badsum++;
goto bad;
}
/*
* Convert fields to host representation.
*/
ip->ip_len = ntohs((u_short)ip->ip_len);
if (ip->ip_len < hlen) {
ipstat.ips_badlen++;
goto bad;
}
ip->ip_id = ntohs(ip->ip_id);
ip->ip_off = ntohs((u_short)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.
*/
i = -(u_short)ip->ip_len;
m0 = m;
for (;;) {
i += m->m_len;
if (m->m_next == 0)
break;
m = m->m_next;
}
if (i != 0) {
if (i < 0) {
ipstat.ips_tooshort++;
m = m0;
goto bad;
}
if (i <= m->m_len)
m->m_len -= i;
else
m_adj(m0, -i);
}
m = m0;
/*
* 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(ip, ifp))
goto next;
/*
* Check our list of addresses, to see if the packet is for us.
*/
for (ia = in_ifaddr; ia; ia = ia->ia_next) {
#define satosin(sa) ((struct sockaddr_in *)(sa))
if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_dst.s_addr)
goto ours;
if (
#ifdef DIRECTED_BROADCAST
ia->ia_ifp == ifp &&
#endif
(ia->ia_ifp->if_flags & IFF_BROADCAST)) {
u_long t;
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;
/*
* Look for all-0's host part (old broadcast addr),
* either for subnet or net.
*/
t = ntohl(ip->ip_dst.s_addr);
if (t == ia->ia_subnet)
goto ours;
if (t == ia->ia_net)
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(ip, ifp, 0);
goto next;
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_DF) {
/*
* Look for queue of fragments
* of this datagram.
*/
for (fp = ipq.next; fp != &ipq; 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;
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;
((struct ipasfrag *)ip)->ipf_mff = 0;
if (ip->ip_off & IP_MF)
((struct ipasfrag *)ip)->ipf_mff = 1;
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 (((struct ipasfrag *)ip)->ipf_mff || ip->ip_off) {
ipstat.ips_fragments++;
ip = ip_reass((struct ipasfrag *)ip, fp);
if (ip == 0)
goto next;
m = dtom(ip);
} else
if (fp)
ip_freef(fp);
} else
ip->ip_len -= hlen;
/*
* Switch out to protocol's input routine.
*/
(*inetsw[ip_protox[ip->ip_p]].pr_input)(m, ifp);
goto next;
bad:
m_freem(m);
goto next;
}
/*
* 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.
*/
struct ip *
ip_reass(ip, fp)
register struct ipasfrag *ip;
register struct ipq *fp;
{
register struct mbuf *m = dtom(ip);
register struct ipasfrag *q;
struct mbuf *t;
int hlen = ip->ip_hl << 2;
int i, next;
/*
* Presence of header sizes in mbufs
* would confuse code below.
*/
m->m_off += 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, &ipq);
fp->ipq_ttl = IPFRAGTTL;
fp->ipq_p = ip->ip_p;
fp->ipq_id = ip->ip_id;
fp->ipq_next = fp->ipq_prev = (struct ipasfrag *)fp;
fp->ipq_src = ((struct ip *)ip)->ip_src;
fp->ipq_dst = ((struct ip *)ip)->ip_dst;
q = (struct ipasfrag *)fp;
goto insert;
}
/*
* Find a segment which begins after this one does.
*/
for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next)
if (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 (q->ipf_prev != (struct ipasfrag *)fp) {
i = q->ipf_prev->ip_off + q->ipf_prev->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.
*/
while (q != (struct ipasfrag *)fp && ip->ip_off + ip->ip_len > q->ip_off) {
i = (ip->ip_off + ip->ip_len) - q->ip_off;
if (i < q->ip_len) {
q->ip_len -= i;
q->ip_off += i;
m_adj(dtom(q), i);
break;
}
q = q->ipf_next;
m_freem(dtom(q->ipf_prev));
ip_deq(q->ipf_prev);
}
insert:
/*
* Stick new segment in its place;
* check for complete reassembly.
*/
ip_enq(ip, q->ipf_prev);
next = 0;
for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next) {
if (q->ip_off != next)
return (0);
next += q->ip_len;
}
if (q->ipf_prev->ipf_mff)
return (0);
/*
* Reassembly is complete; concatenate fragments.
*/
q = fp->ipq_next;
m = dtom(q);
t = m->m_next;
m->m_next = 0;
m_cat(m, t);
q = q->ipf_next;
while (q != (struct ipasfrag *)fp) {
t = dtom(q);
q = q->ipf_next;
m_cat(m, t);
}
/*
* Create header for new ip packet by
* modifying header of first packet;
* dequeue and discard fragment reassembly header.
* Make header visible.
*/
ip = fp->ipq_next;
ip->ip_len = next;
((struct ip *)ip)->ip_src = fp->ipq_src;
((struct ip *)ip)->ip_dst = fp->ipq_dst;
remque(fp);
(void) m_free(dtom(fp));
m = dtom(ip);
m->m_len += (ip->ip_hl << 2);
m->m_off -= (ip->ip_hl << 2);
return ((struct ip *)ip);
dropfrag:
ipstat.ips_fragdropped++;
m_freem(m);
return (0);
}
/*
* Free a fragment reassembly header and all
* associated datagrams.
*/
ip_freef(fp)
struct ipq *fp;
{
register struct ipasfrag *q, *p;
for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = p) {
p = q->ipf_next;
ip_deq(q);
m_freem(dtom(q));
}
remque(fp);
(void) m_free(dtom(fp));
}
/*
* Put an ip fragment on a reassembly chain.
* Like insque, but pointers in middle of structure.
*/
ip_enq(p, prev)
register struct ipasfrag *p, *prev;
{
p->ipf_prev = prev;
p->ipf_next = prev->ipf_next;
prev->ipf_next->ipf_prev = p;
prev->ipf_next = p;
}
/*
* To ip_enq as remque is to insque.
*/
ip_deq(p)
register struct ipasfrag *p;
{
p->ipf_prev->ipf_next = p->ipf_next;
p->ipf_next->ipf_prev = p->ipf_prev;
}
/*
* IP timer processing;
* if a timer expires on a reassembly
* queue, discard it.
*/
ip_slowtimo()
{
register struct ipq *fp;
int s = splnet();
fp = ipq.next;
if (fp == 0) {
splx(s);
return;
}
while (fp != &ipq) {
--fp->ipq_ttl;
fp = fp->next;
if (fp->prev->ipq_ttl == 0) {
ipstat.ips_fragtimeout++;
ip_freef(fp->prev);
}
}
splx(s);
}
/*
* Drain off all datagram fragments.
*/
ip_drain()
{
while (ipq.next != &ipq) {
ipstat.ips_fragdropped++;
ip_freef(ipq.next);
}
}
extern struct in_ifaddr *ifptoia();
struct in_ifaddr *ip_rtaddr();
/*
* Do option processing on a datagram,
* possibly discarding it if bad options
* are encountered.
*/
ip_dooptions(ip, ifp)
register struct ip *ip;
struct ifnet *ifp;
{
register u_char *cp;
int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
register struct ip_timestamp *ipt;
register struct in_ifaddr *ia;
struct in_addr *sin;
n_time ntime, iptime();
cp = (u_char *)(ip + 1);
cnt = (ip->ip_hl << 2) - sizeof (struct ip);
for (; cnt > 0; cnt -= optlen, cp += optlen) {
opt = UCHAR(cp[IPOPT_OPTVAL]);
if (opt == IPOPT_EOL)
break;
if (opt == IPOPT_NOP)
optlen = 1;
else {
optlen = UCHAR(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 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;
}
/*
* 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.
*/
save_rte(cp, ip->ip_src);
break;
}
/*
* locate outgoing interface
*/
bcopy((caddr_t)(cp + off), (caddr_t)&ipaddr.sin_addr,
sizeof(ipaddr.sin_addr));
if ((opt == IPOPT_SSRR &&
in_iaonnetof(in_netof(ipaddr.sin_addr)) == 0) ||
(ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_SRCFAIL;
goto bad;
}
ip->ip_dst = ipaddr.sin_addr;
bcopy((caddr_t)&(IA_SIN(ia)->sin_addr),
(caddr_t)(cp + off), sizeof(struct in_addr));
cp[IPOPT_OFFSET] += sizeof(struct in_addr);
/*
* Since 2.11 will never have multicasting so the following line from 4.4
* is effectively always 1.
*/
forward = !IN_MULTICAST(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;
bcopy((caddr_t)(&ip->ip_dst), (caddr_t)&ipaddr.sin_addr,
sizeof(ipaddr.sin_addr));
/*
* locate outgoing interface
*/
if ((ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_HOST;
goto bad;
}
bcopy((caddr_t)&(IA_SIN(ia)->sin_addr),
(caddr_t)(cp + off), 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 (long)) {
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 + sizeof(n_time) +
sizeof(struct in_addr) > ipt->ipt_len)
goto bad;
ia = ifptoia(ifp);
bcopy((caddr_t)&IA_SIN(ia)->sin_addr,
(caddr_t)sin, sizeof(struct in_addr));
ipt->ipt_ptr += sizeof(struct in_addr);
break;
case IPOPT_TS_PRESPEC:
if (ipt->ipt_ptr + sizeof(n_time) +
sizeof(struct in_addr) > ipt->ipt_len)
goto bad;
bcopy((caddr_t)sin, (caddr_t)&ipaddr.sin_addr,
sizeof(struct in_addr));
if (ifa_ifwithaddr((struct sockaddr *)&ipaddr) == 0)
continue;
ipt->ipt_ptr += sizeof(struct in_addr);
break;
default:
goto bad;
}
ntime = iptime();
bcopy((caddr_t)&ntime, (caddr_t)cp + ipt->ipt_ptr - 1,
sizeof(n_time));
ipt->ipt_ptr += sizeof(n_time);
}
}
if (forward) {
if (ipforward_srcrt == 0) {
type = ICMP_UNREACH;
code = ICMP_UNREACH_SRCFAIL;
goto bad;
}
ip_forward(ip, ifp, 1);
return(1);
}
return (0);
bad:
ip->ip_len -= ip->ip_hl << 2; /* XXX icmp_error adds in hdr length */
icmp_error(ip, type, code, ifp);
return (1);
}
/*
* Given address of next destination (final or next hop),
* return internet address info of interface to be used to get there.
*/
struct in_ifaddr *
ip_rtaddr(dst)
struct in_addr dst;
{
register struct sockaddr_in *sin;
register struct in_ifaddr *ia;
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_addr = dst;
rtalloc(&ipforward_rt);
}
if (ipforward_rt.ro_rt == 0)
return ((struct in_ifaddr *)0);
/*
* Find address associated with outgoing interface.
*/
for (ia = in_ifaddr; ia; ia = ia->ia_next)
if (ia->ia_ifp == ipforward_rt.ro_rt->rt_ifp)
break;
return (ia);
}
/*
* Save incoming source route for use in replies,
* to be picked up later by ip_srcroute if the receiver is interested.
*/
save_rte(option, dst)
u_char *option;
struct in_addr dst;
{
unsigned olen;
olen = option[IPOPT_OLEN];
if (olen > sizeof(ip_srcrt) - 1) {
if (ipprintfs)
printf("save_rte: olen %d\n", olen);
return;
}
bcopy((caddr_t)option, (caddr_t)ip_srcrt.srcopt, olen);
ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
ip_srcrt.route[ip_nhops++] = 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_SOOPTS);
if (m == 0)
return ((struct mbuf *)0);
m->m_len = ip_nhops * sizeof(struct in_addr) + IPOPT_OFFSET + 1 + 1;
/*
* First save first hop for return route
*/
p = &ip_srcrt.route[ip_nhops - 1];
*(mtod(m, struct in_addr *)) = *p--;
/*
* Copy option fields and padding (nop) to mbuf.
*/
ip_srcrt.nop = IPOPT_NOP;
bcopy((caddr_t)&ip_srcrt, mtod(m, caddr_t) + sizeof(struct in_addr),
IPOPT_OFFSET + 1 + 1);
q = (struct in_addr *)(mtod(m, caddr_t) +
sizeof(struct in_addr) + IPOPT_OFFSET + 1 + 1);
/*
* Record return path as an IP source route,
* reversing the path (pointers are now aligned).
*/
while (p >= ip_srcrt.route)
*q++ = *p--;
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.
*/
ip_stripoptions(ip, mopt)
struct ip *ip;
struct mbuf *mopt;
{
register int i;
register struct mbuf *m;
register caddr_t opts;
int olen;
olen = (ip->ip_hl<<2) - sizeof (struct ip);
m = dtom(ip);
opts = (caddr_t)(ip + 1);
if (mopt) {
mopt->m_len = olen;
mopt->m_off = MMINOFF;
bcopy(opts, mtod(mopt, caddr_t), (unsigned)olen);
}
i = m->m_len - (sizeof (struct ip) + olen);
bcopy(opts + olen, opts, (unsigned)i);
m->m_len -= olen;
ip->ip_hl = sizeof(struct ip) >> 2;
}
u_char inetctlerrmap[PRC_NCMDS] = {
0, 0, 0, 0,
0, 0, EHOSTDOWN, EHOSTUNREACH,
ENETUNREACH, EHOSTUNREACH, ECONNREFUSED, ECONNREFUSED,
EMSGSIZE, EHOSTUNREACH, 0, 0,
0, 0, 0, 0,
ENOPROTOOPT
};
extern int in_interfaces;
/*
* 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 (possibly because we have only a single external
* network), 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.
*/
ip_forward(ip, ifp, srcrt)
register struct ip *ip;
struct ifnet *ifp;
int srcrt;
{
register int error, type = 0, code;
register struct sockaddr_in *sin;
struct mbuf *mcopy;
struct in_addr dest;
dest.s_addr = 0;
if (ipprintfs)
printf("forward: src %X dst %X ttl %x\n", ntohl(ip->ip_src),
ntohl(ip->ip_dst), ip->ip_ttl);
ip->ip_id = htons(ip->ip_id);
if (in_canforward(ip->ip_dst) == 0) {
ipstat.ips_cantforward++;
m_freem(dtom(ip));
return;
}
if (ip->ip_ttl < IPTTLDEC) {
type = ICMP_TIMXCEED, code = ICMP_TIMXCEED_INTRANS;
goto sendicmp;
}
ip->ip_ttl -= IPTTLDEC;
sin = (struct sockaddr_in *)&ipforward_rt.ro_dst;
if (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_addr = ip->ip_dst;
rtalloc(&ipforward_rt);
if (ipforward_rt.ro_rt == 0) {
ip->ip_len -= ip->ip_hl << 2; /* icmp_error assumes this */
icmp_error(ip,ICMP_UNREACH,ICMP_UNREACH_HOST,ifp,dest);
return;
}
}
/*
* Save at most 64 bytes of the packet in case
* we need to generate an ICMP message to the src.
*/
mcopy = m_copy(dtom(ip), 0, MIN((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 modfied by a redirect.
*/
#define satosin(sa) ((struct sockaddr_in *)(sa))
if (ipforward_rt.ro_rt && ipforward_rt.ro_rt->rt_ifp == ifp &&
(ipforward_rt.ro_rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0 &&
satosin(&ipforward_rt.ro_rt->rt_dst)->sin_addr.s_addr != 0 &&
ipsendredirects && !srcrt && ip->ip_hl == (sizeof(struct ip) >> 2)){
struct in_ifaddr *ia;
u_long src = ntohl(ip->ip_src.s_addr);
u_long dst = ntohl(ip->ip_dst.s_addr);
if ((ia = ifptoia(ifp)) &&
(src & ia->ia_subnetmask) == ia->ia_subnet) {
if (ipforward_rt.ro_rt->rt_flags & RTF_GATEWAY)
dest = satosin(&ipforward_rt.ro_rt->rt_gateway)->sin_addr;
else
dest = ip->ip_dst;
/*
* If the destination is reached by a route to host,
* is on a subnet of a local net, or is directly
* on the attached net (!), use host redirect.
* (We may be the correct first hop for other subnets.)
*/
type = ICMP_REDIRECT;
code = ICMP_REDIRECT_NET;
if ((ipforward_rt.ro_rt->rt_flags & RTF_HOST) ||
(ipforward_rt.ro_rt->rt_flags & RTF_GATEWAY) == 0)
code = ICMP_REDIRECT_HOST;
else for (ia = in_ifaddr; ia = ia->ia_next; )
if ((dst & ia->ia_netmask) == ia->ia_net) {
if (ia->ia_subnetmask != ia->ia_netmask)
code = ICMP_REDIRECT_HOST;
break;
}
if (ipprintfs)
printf("redirect (%d) to %x\n", code, dest);
}
}
error = ip_output(dtom(ip), (struct mbuf *)0, &ipforward_rt,
IP_FORWARDING);
if (error)
ipstat.ips_cantforward++;
else if (type)
ipstat.ips_redirectsent++;
else {
if (mcopy)
m_freem(mcopy);
ipstat.ips_forward++;
return;
}
if (mcopy == NULL)
return;
ip = mtod(mcopy, struct ip *);
type = ICMP_UNREACH;
switch (error) {
case 0: /* forwarded, but need redirect */
type = ICMP_REDIRECT;
/* code set above */
break;
case ENETUNREACH:
case ENETDOWN:
if (in_localaddr(ip->ip_dst))
code = ICMP_UNREACH_HOST;
else
code = ICMP_UNREACH_NET;
break;
case EMSGSIZE:
code = ICMP_UNREACH_NEEDFRAG;
break;
case EPERM:
code = ICMP_UNREACH_PORT;
break;
case ENOBUFS:
type = ICMP_SOURCEQUENCH;
break;
case EHOSTDOWN:
case EHOSTUNREACH:
code = ICMP_UNREACH_HOST;
break;
}
sendicmp:
ip->ip_len -= ip->ip_hl << 2; /* icmp_error assumes this */
icmp_error(ip, type, code, ifp, dest);
}
int
ip_sysctl(name, namelen, oldp, oldlenp, newp, newlen)
int *name;
u_int namelen;
void *oldp;
size_t *oldlenp;
void *newp;
size_t newlen;
{
/* All sysctl names at this level are terminal. */
if (namelen != 1)
return (ENOTDIR);
switch (name[0]) {
case IPCTL_FORWARDING:
return (sysctl_int(oldp, oldlenp, newp, newlen, &ipforwarding));
case IPCTL_SENDREDIRECTS:
return (sysctl_int(oldp, oldlenp, newp, newlen,
&ipsendredirects));
case IPCTL_DEFTTL:
return (sysctl_int(oldp, oldlenp, newp, newlen, &ip_defttl));
#ifdef notyet
case IPCTL_DEFMTU:
return (sysctl_int(oldp, oldlenp, newp, newlen, &ip_mtu));
#endif
case IPCTL_FORWSRCRT:
return (sysctl_int(oldp, oldlenp, newp, newlen,
&ipforward_srcrt));
default:
return (EOPNOTSUPP);
}
/* NOTREACHED */
}