V10/sys/inet/ip_input.c
/* ip_input.c 6.1 83/08/16 */
#include "sys/param.h"
#include "sys/systm.h"
#include "sys/stream.h"
#include "sys/inet/in.h"
#include "sys/inet/ip.h"
#include "sys/inet/ip_var.h"
int ipqmaxlen = 50;
struct ipq ipq; /* ip reass. queue */
u_char ipcksum = 1;
struct block *ip_reass();
/*
* 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.
*/
ip_input(bp)
register struct block *bp;
{
register struct ip *ip;
register int i;
int hlen;
if (bp == 0)
return;
if (BLEN(bp) < sizeof (struct ip) &&
(bp = bp_pullup(bp, sizeof (struct ip))) == 0) {
ipstat.ips_toosmall++;
return;
}
ip = (struct ip *)bp->rptr;
if ((hlen = ip->ip_hl << 2) > BLEN(bp)) {
if ((bp = bp_pullup(bp, hlen)) == 0) {
ipstat.ips_badhlen++;
return;
}
ip = (struct ip *)bp->rptr;
}
if (ipcksum)
if (ip->ip_sum = in_cksum(bp, 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 blocks if longer than we expect.
* Drop packet if shorter than we expect.
*/
i = bp_len(bp) - ip->ip_len;
if (i < 0) {
ipstat.ips_tooshort++;
goto bad;
}
if (i > 0)
bp_adj(bp, -i);
/*
* 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).
*/
ip->ip_dst = ntohl(ip->ip_dst);
ip->ip_src = ntohl(ip->ip_src);
if (hlen > sizeof (struct ip) && ip_dooptions(ip))
return;
if (ip_ifwithaddr(ip->ip_dst) == 0) {
ip_forward(bp);
return;
}
/*
* Adjust ip_len to not reflect header,
* set ip_tos if more fragments are expected,
* convert offset of this to bytes.
*/
ip->ip_len -= hlen;
ip->ip_tos = 0;
if (ip->ip_off & IP_MF)
ip->ip_tos = 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.
*/
bp = ip_reass(bp);
if (bp == 0)
return;
ip = (struct ip *) bp->rptr;
/*
* Switch out to protocol's input routine.
*/
ipdrint(bp, (unsigned int)(ip->ip_p));
return;
bad:
bp_free(bp);
}
/*
* Take incoming datagram fragment and try to
* reassemble it into whole datagram.
*/
#define ASIPQ(x) ((struct ipq *)(x)->rptr)
#define ASFRAG(x) ((struct ipasfrag *)(x)->rptr)
struct block *
ip_reass(bp)
register struct block *bp;
{
register struct block *fp;
register struct ip *ip = (struct ip *) bp->rptr;
register struct block *pqbp, *qbp, *nqbp;
int i, next;
/*
* Look for queue of fragments
* of this datagram.
*/
for(fp=ipq.next; fp!=(struct block *)0; fp=ASIPQ(fp)->next)
if (ip->ip_id == ASIPQ(fp)->ipq_id &&
ip->ip_src == ASIPQ(fp)->ipq_src &&
ip->ip_dst == ASIPQ(fp)->ipq_dst &&
ip->ip_p == ASIPQ(fp)->ipq_p)
break;
/* if this datagram is not a fragment then toss out fragments
* for this connection.
*/
if (!ip->ip_tos && ip->ip_off == 0) {
if(fp != (struct block *)0)
ip_freef(fp);
return(bp);
}
/*
* If first fragment to arrive, create a reassembly queue.
*/
if (fp == 0) {
if ((fp = bp_get()) == NULL)
goto dropfrag;
fp->wptr += sizeof(struct ipq); /* not really necessary */
/* no fragments yet */
fp->next = 0;
/* insque(fp, &ipq); */
if (ipq.next != (struct block *)0)
ASIPQ(ipq.next)->prev = fp;
else
ipq.prev = fp;
ASIPQ(fp)->next = ipq.next;
ASIPQ(fp)->prev = 0;
ipq.next = fp;
ASIPQ(fp)->ipq_ttl = IPFRAGTTL;
ASIPQ(fp)->ipq_p = ip->ip_p;
ASIPQ(fp)->ipq_id = ip->ip_id;
ASIPQ(fp)->ipq_src = ((struct ip *)ip)->ip_src;
ASIPQ(fp)->ipq_dst = ((struct ip *)ip)->ip_dst;
pqbp = 0;
qbp = 0;
goto insert;
}
/*
* Find a segment which begins at or after this one does.
*/
for (pqbp=(struct block *)0,qbp=fp->next; qbp!=(struct block *)0;
pqbp=qbp,qbp=ASFRAG(qbp)->ipf_next)
if (ASFRAG(qbp)->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 that preceding
* segment. If it provides all of our data, drop us.
*/
if (pqbp!=(struct block *)0) {
i = ASFRAG(pqbp)->ip_off + ASFRAG(pqbp)->ip_len - ip->ip_off;
if (i > 0) {
if (i >= ip->ip_len)
goto dropfrag;
ASFRAG(pqbp)->ip_len -= i;
bp_adj(pqbp, -i);
}
}
/*
* While we overlap succeeding segments trim us or,
* if they are completely covered, dequeue them.
*/
while (qbp!=0 && (i = (ip->ip_off + ip->ip_len) - ASFRAG(qbp)->ip_off) > 0) {
if (i < ASFRAG(qbp)->ip_len) {
ip->ip_len -= i;
bp_adj(bp, -i);
break;
}
if (pqbp == (struct block *)0)
nqbp = fp->next = ASFRAG(qbp)->ipf_next;
else
nqbp = ASFRAG(pqbp)->ipf_next = ASFRAG(qbp)->ipf_next;
bp_free(qbp);
qbp = nqbp;
}
insert:
/*
* Stick new segment in its place;
* check for complete reassembly.
*/
if (pqbp == (struct block *)0) {
ASFRAG(bp)->ipf_next = fp->next;
fp->next = bp;
} else {
ASFRAG(bp)->ipf_next = ASFRAG(pqbp)->ipf_next;
ASFRAG(pqbp)->ipf_next = bp;
}
next = 0;
for (pqbp=0,qbp=fp->next; qbp!=(struct block *)0;
pqbp=qbp,qbp=ASFRAG(qbp)->ipf_next) {
if (ASFRAG(qbp)->ip_off != next)
return (0);
next += ASFRAG(qbp)->ip_len;
}
if (pqbp != (struct block *)0 && ASFRAG(pqbp)->ip_tos)
return (0);
/*
* Reassembly is complete; concatenate fragments by removing all
* ip headers.
*/
ASFRAG(fp->next)->ip_len = next;
for (qbp=ASFRAG(fp->next)->ipf_next; qbp!=(struct block *)0; qbp=nqbp) {
nqbp = ASFRAG(qbp)->ipf_next;
qbp->rptr += ((struct ip *)qbp->rptr)->ip_hl<<2;
bp_cat(fp->next, qbp);
}
/*
* Create header for new ip packet by
* modifying header of first packet;
* dequeue and discard fragment reassembly header.
* Make header visible.
*/
bp = fp->next;
((struct ip *)bp->rptr)->ip_src = ASIPQ(fp)->ipq_src;
((struct ip *)bp->rptr)->ip_dst = ASIPQ(fp)->ipq_dst;
((struct ip *)bp->rptr)->ip_tos = 0;
fp->next = 0;
ip_freef(fp);
return (bp);
dropfrag:
bp_free(bp);
return (0);
}
/*
* Free a fragment reassembly header and all
* associated datagrams.
*/
ip_freef(fp)
struct block *fp;
{
register struct block *q, *p;
for (p = fp->next; p != 0; p = q) {
q = ASFRAG(p)->ipf_next;
bp_free(p);
}
p = ASIPQ(fp)->prev;
q = ASIPQ(fp)->next;
if (p != (struct block *)0)
ASIPQ(p)->next = q;
else
ipq.next = q;
if (q != (struct block *)0)
ASIPQ(q)->prev = p;
else
ipq.prev = p;
freeb(fp);
}
/*
* IP timer processing;
* if a timer expires on a reassembly
* queue, discard it.
*/
ip_slowtimo()
{
register struct block *fp, *nfp;
int s = spl6();
for (fp=ipq.next; fp!=(struct block *)0; fp=nfp) {
nfp = ASIPQ(fp)->next;
if (--ASIPQ(fp)->ipq_ttl == 0)
ip_freef(fp);
}
timeout(ip_slowtimo, (caddr_t)0, HZ);
splx(s);
}
#if NOTDEF
/* who calls this? */
/*
* Drain off all datagram fragments.
*/
ip_drain()
{
while (ipq.next != (struct block *)0)
ip_freef(ipq.next);
}
#endif
/*
* Do option processing on a datagram,
* possibly discarding it if bad options
* are encountered.
*/
ip_dooptions(ip)
struct ip *ip;
{
register u_char *cp;
int opt, optlen, cnt;
cp = (u_char *)(ip + 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)
optlen = 1;
else
optlen = cp[1];
switch (opt) {
default:
break;
#ifdef FAT_CHANCE
/*
* 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 (cp[2] < 4 || cp[2] > optlen - (sizeof (long) - 1))
break;
sin = (struct in_addr *)(cp + cp[2]);
ipaddr.sin_addr = *sin;
ifp = if_ifwithaddr((struct sockaddr *)&ipaddr);
type = ICMP_UNREACH, code = ICMP_UNREACH_SRCFAIL;
if (ifp == 0) {
if (opt == IPOPT_SSRR)
goto bad;
break;
}
t = ip->ip_dst; ip->ip_dst = *sin; *sin = t;
cp[2] += 4;
if (cp[2] > optlen - (sizeof (long) - 1))
break;
ip->ip_dst = sin[1];
if (opt == IPOPT_SSRR &&
if_ifonnetof(in_netof(ip->ip_dst)) == 0)
goto bad;
break;
case IPOPT_TS:
code = cp - (u_char *)ip;
type = ICMP_PARAMPROB;
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+cp[2]);
switch (ipt->ipt_flg) {
case IPOPT_TS_TSONLY:
break;
case IPOPT_TS_TSANDADDR:
if (ipt->ipt_ptr + 8 > ipt->ipt_len)
goto bad;
if (ifinet == 0)
goto bad; /* ??? */
*sin++ = ((struct sockaddr_in *)&ifinet->if_addr)->sin_addr;
break;
case IPOPT_TS_PRESPEC:
ipaddr.sin_addr = *sin;
if (if_ifwithaddr((struct sockaddr *)&ipaddr) == 0)
continue;
if (ipt->ipt_ptr + 8 > ipt->ipt_len)
goto bad;
ipt->ipt_ptr += 4;
break;
default:
goto bad;
}
*(n_time *)sin = iptime();
ipt->ipt_ptr += 4;
#endif FATCHANCE
}
}
return (0);
}
/*
* 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(bp, blopt)
register struct block *bp, *blopt;
{
struct ip *ip = (struct ip *) bp->rptr;
register int i;
int olen;
olen = (ip->ip_hl<<2) - sizeof (struct ip);
ip++;
if (blopt) {
blopt->wptr = blopt->base + olen;
blopt->rptr = blopt->base;
bcopy((caddr_t)ip, (caddr_t)blopt->rptr, (unsigned)olen);
}
i = BLEN(bp) - (sizeof (struct ip) + olen);
bcopy((caddr_t)ip+olen, (caddr_t)ip, (unsigned)i);
bp->wptr -= olen;
}
int ipforwarding = 1;
extern ipprintfs;
/*
* Forward a packet. If some error occurs return the sender
* and icmp packet. Note we can't always generate a meaningful
* icmp message because icmp doesn't have a large enough repetoire
* of codes and types.
*/
ip_forward(bp)
register struct block *bp;
{
register struct ip *ip = (struct ip *) bp->rptr;
struct block *blopt;
if(ipprintfs)
printf("forward: src %x dst %x ttl %x\n", ip->ip_src,
ip->ip_dst, ip->ip_ttl);
if (ipforwarding == 0) {
bp_free(bp);
return;
}
if (ip->ip_ttl < IPTTLDEC) {
bp_free(bp);
return;
}
ip->ip_ttl -= IPTTLDEC;
blopt = bp_get();
if (blopt == NULL) {
bp_free(bp);
return;
}
blopt->next = 0;
ip_stripoptions(bp, blopt);
ip_output(bp, blopt, IP_FORWARDING);
}