insert debugging code

[unix-history] / usr / src / sys / netinet / ip_input.c

/* ip_input.c 1.9 81/10/29 */

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/clock.h"
#include "../h/mbuf.h"
#include "../inet/inet.h"
#include "../inet/inet_systm.h"
#include "../inet/imp.h"
#include "../inet/ip.h"                 /* belongs before inet.h */
#include "../inet/ip_icmp.h"
#include "../inet/tcp.h"

int     nosum = 0;

struct  ip *ip_reass();

/*
* Ip input routines.
*/

/*
* 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(m0)
       struct mbuf *m0;
{
       register int i;
       register struct ip *ip, *q;
       register struct ipq *fp;
       register struct mbuf *m = m0;
       int hlen;

COUNT(IP_INPUT);
       /*
        * Check header and byteswap.
        */
       ip = mtod(m, struct ip *);
       if ((hlen = ip->ip_hl << 2) > m->m_len) {
               printf("ip hdr ovflo\n");
               m_freem(m);
               return;
       }
       i = ip->ip_sum;
       ip->ip_sum = 0;
#ifdef vax
       if (hlen == sizeof (struct ip)) {
               asm("movl r10,r0; movl (r0)+,r1; addl2 (r0)+,r1");
               asm("adwc (r0)+,r1; adwc (r0)+,r1; adwc (r0)+,r1");
               asm("adwc $0,r1; ashl $-16,r1,r0; addw2 r0,r1");
               asm("adwc $0,r1");              /* ### */
               asm("mcoml r1,r1; movzwl r1,r1; subl2 r1,r11");
       } else
#endif
               i -= cksum(m, hlen);
       if (i) {
               netstat.ip_badsum++;
               if (!nosum) {
                       m_freem(m);
                       return;
               }
       }
       ip->ip_len = ntohs(ip->ip_len);
       ip->ip_id = ntohs(ip->ip_id);
       ip->ip_off = 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.
        */
       i = 0;
       for (; m != NULL; m = m->m_next)
               i += m->m_len;
       m = m0;
       if (i != ip->ip_len) {
               if (i < ip->ip_len) {
                       printf("ip_input: short packet\n");
                       m_freem(m);
                       return;
               }
               m_adj(m, ip->ip_len - i);
       }

       /*
        * Process options and, if not destined for us,
        * ship it on.
        */
       if (hlen > sizeof (struct ip))
               ip_dooptions(ip, hlen);
       if (ip->ip_dst.s_addr != n_lhost.s_addr) {
               if (--ip->ip_ttl == 0) {
                       icmp_error(ip, ICMP_TIMXCEED);
                       return;
               }
               ip_output(dtom(ip));
               return;
       }

       /*
        * 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;
       ip->ip_mff = 0;
       if (ip->ip_off & IP_MF)
               ip->ip_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 (ip->ip_mff || ip->ip_off) {
               ip = ip_reass(ip, fp);
               if (ip == 0)
                       return;
               hlen = ip->ip_hl << 2;
               m = dtom(ip);
       } else
               if (fp)
                       (void) ip_freef(fp);

       /*
        * Switch out to protocol specific routine.
        * SHOULD GO THROUGH PROTOCOL SWITCH TABLE
        */
       switch (ip->ip_p) {

       case IPPROTO_ICMP:
               icmp_input(m);
               break;

       case IPPROTO_TCP:
               if (hlen > sizeof (struct ip))
                       ip_stripoptions(ip, hlen);
               tcp_input(m);
               break;

       case IPPROTO_UDP:
               if (hlen > sizeof (struct ip))
                       ip_stripoptions(ip, hlen);
               udp_input(m);
               break;

       default:
               raw_input(m);
               break;
       }
}

/*
* Take incoming datagram fragment and try to
* reassamble 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 ip *ip;
       register struct ipq *fp;
{
       register struct mbuf *m = dtom(ip);
       register struct ip *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(1)) == NULL)
                       goto dropfrag;
               t->m_off = MMINOFF;
               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 ip *)fp;
               fp->ipq_src = ip->ip_src;
               fp->ipq_dst = ip->ip_dst;
       }

       /*
        * Find a segment which begins after this one does.
        */
       for (q = fp->ipq_next; q != (struct ip *)fp; q = q->ip_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->ip_prev != (struct ip *)fp) {
               i = q->ip_prev->ip_off + q->ip_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 ip *)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;
                       m_adj(dtom(q), i);
                       break;
               }
               q = q->ip_next;
               m_freem(dtom(q->ip_prev));
               ip_deq(q->ip_prev);
       }

       /*
        * Stick new segment in its place;
        * check for complete reassembly.
        */
       ip_enq(ip, q->ip_prev);
       next = 0;
       for (q = fp->ipq_next; q != (struct ip *)fp; q = q->ip_next) {
               if (q->ip_off != next)
                       return (0);
               next += q->ip_len;
       }
       if (q->ip_prev->ip_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);
       while ((q = q->ip_next) != (struct ip *)fp)
               m_cat(m, dtom(q));

       /*
        * 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;
       ip->ip_src = fp->ipq_src;
       ip->ip_dst = fp->ipq_dst;
       remque(fp);
       m_free(dtom(fp));
       m = dtom(ip);
       m->m_len += sizeof (struct ip);
       m->m_off -= sizeof (struct ip);
       return (ip);

dropfrag:
       m_freem(m);
       return (0);
}

/*
* Free a fragment reassembly header and all
* associated datagrams.
*/
struct ipq *
ip_freef(fp)
       struct ipq *fp;
{
       register struct ip *q;
       struct mbuf *m;

       for (q = fp->ipq_next; q != (struct ip *)fp; q = q->ip_next)
               m_freem(dtom(q));
       m = dtom(fp);
       fp = fp->next;
       remque(fp->prev);
       m_free(m);
       return (fp);
}

/*
* Put an ip fragment on a reassembly chain.
* Like insque, but pointers in middle of structure.
*/
ip_enq(p, prev)
       register struct ip *p;
       register struct ip *prev;
{
COUNT(IP_ENQ);

       p->ip_prev = prev;
       p->ip_next = prev->ip_next;
       prev->ip_next->ip_prev = p;
       prev->ip_next = p;
}

/*
* To ip_enq as remque is to insque.
*/
ip_deq(p)
       register struct ip *p;
{
COUNT(IP_DEQ);

       p->ip_prev->ip_next = p->ip_next;
       p->ip_next->ip_prev = p->ip_prev;
}

/*
* IP timer processing;
* if a timer expires on a reassembly
* queue, discard it.
*/
ip_timeo()
{
       register struct ip *q;
       register struct ipq *fp;
       int s = splnet();
COUNT(IP_TIMEO);

       for (fp = ipq.next; fp != &ipq; )
               if (--fp->ipq_ttl == 0)
                       fp = ip_freef(fp);
               else
                       fp = fp->next;
       timeout(ip_timeo, 0, hz);
       splx(s);
}

/*
* 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, s;
       struct socket *sp;

       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;

               case IPOPT_LSRR:
               case IPOPT_SSRR:
                       if (cp[2] < 4 || cp[2] > optlen - 3)
                               break;
                       sp = (struct socket *)(cp+cp[2]);
                       if (n_lhost.s_addr == *(u_long *)sp) {
                               if (opt == IPOPT_SSRR) {
                                       /* make sure *sp directly accessible*/
                               }
                               ip->ip_dst = *sp;
                               *sp = n_lhost;
                               cp[2] += 4;
                       }
                       break;

               case IPOPT_TS:
                       if (cp[2] < 5)
                               goto bad;
                       if (cp[2] > cp[1] - 3) {
                               if ((cp[3] & 0xf0) == 0xf0)
                                       goto bad;
                               cp[3] += 0x10;
                               break;
                       }
                       sp = (struct socket *)(cp+cp[2]);
                       switch (cp[3] & 0xf) {

                       case IPOPT_TS_TSONLY:
                               break;

                       case IPOPT_TS_TSANDADDR:
                               if (cp[2] > cp[1] - 7)
                                       goto bad;
                               break;

                       case IPOPT_TS_PRESPEC:
                               if (*(u_long *)sp != n_lhost.s_addr)
                                       break;
                               if (cp[2] > cp[1] - 7)
                                       goto bad;
                               cp[1] += 4;
                               break;

                       default:
                               goto bad;
                       }
                       s = spl6();
                       *(int *)sp = (time % SECDAY) * 1000 + (lbolt*1000/hz);
                       splx(s);
                       cp[1] += 4;
               }
       }
       return (0);
bad:
       /* SHOULD FORCE ICMP MESSAGE */
       return (-1);
}

/*
* Strip out IP options, e.g. before passing
* to higher level protocol in the kernel.
*/
ip_stripoptions(ip)
       struct ip *ip;
{
       register int i;
       register struct mbuf *m;
       char *op;
       int olen;
COUNT(IP_OPT);

       olen = (ip->ip_hl<<2) - sizeof (struct ip);
       op = (caddr_t)ip + olen;
       m = dtom(++ip);
       i = m->m_len - (sizeof (struct ip) + olen);
       bcopy((caddr_t)ip+olen, (caddr_t)ip, i);
       m->m_len -= i;
}

/* stubs */

icmp_error(ip, error)
{

       m_freem(dtom(ip));
}

icmp_input(m)
       struct mbuf *m;
{

       printf("icmp_input %x\n", m);
}

udp_input(m)
       struct mbuf *m;
{

       printf("udp_input %x\n", m);
}

raw_input(m)
       struct mbuf *m;
{

       printf("raw_input %x\n", m);
}