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

/* ip_input.c 1.19 81/11/26 */

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/clock.h"
#include "../h/mbuf.h"
#include "../h/protosw.h"
#include "../h/socket.h"
#include "../net/in.h"
#include "../net/in_systm.h"
#include "../net/if.h"
#include "../net/ip.h"                  /* belongs before in.h */
#include "../net/ip_var.h"
#include "../net/ip_icmp.h"
#include "../net/tcp.h"

u_char  ip_protox[IPPROTO_MAX];

/*
* Ip initialization.
*/
ip_init()
{
       register struct protosw *pr;
       register int i;

COUNT(IP_INIT);
       pr = pffindproto(PF_INET, IPPROTO_RAW);
       if (pr == 0)
               panic("ip_init");
       for (i = 0; i < IPPROTO_MAX; i++)
               ip_protox[i] = pr - protosw;
       for (pr = protosw; pr <= protoswLAST; pr++)
               if (pr->pr_family == PF_INET &&
                   pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW)
                       ip_protox[pr->pr_protocol] = pr - protosw;
       ipq.next = ipq.prev = &ipq;
       ip_id = time & 0xffff;
}

u_char  ipcksum = 1;
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.
*/
ipintr()
{
       register struct ip *ip;
       register struct mbuf *m;
       struct mbuf *m0;
       register int i;
       register struct ipq *fp;
       int hlen, s;

COUNT(IPINTR);
next:
       /*
        * Get next datagram off input queue and get IP header
        * in first mbuf.
        */
       s = splimp();
       IF_DEQUEUE(&ipintrq, m);
       splx(s);
       if (m == 0)
               return;
       if (m->m_len < sizeof (struct ip) &&
           m_pullup(m, sizeof (struct ip)) == 0)
               goto bad;
       ip = mtod(m, struct ip *);
       if ((hlen = ip->ip_hl << 2) > m->m_len &&
           m_pullup(m, hlen) == 0)
               goto bad;
       if (ipcksum)
               if ((ip->ip_sum = in_cksum(m, hlen)) != 0xffff) {
                       printf("ip_sum %x\n", ip->ip_sum);
                       ipstat.ips_badsum++;
                       goto bad;
               }

       /*
        * Convert fields to host representation.
        */
       ip->ip_len = ntohs((u_short)ip->ip_len);
       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 = 0;
       for (m0 = m; m != NULL; m = m->m_next)
               i += m->m_len;
       m = m0;
       if (i != ip->ip_len) {
               if (i < ip->ip_len)
                       goto bad;
               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);
       if (ifnet && ip->ip_dst.s_addr != ifnet->if_addr.s_addr &&
           if_ifwithaddr(ip->ip_dst) == 0) {
               if (--ip->ip_ttl == 0) {
                       icmp_error(ip, ICMP_TIMXCEED, 0);
                       goto next;
               }
               ip_output(dtom(ip), (struct mbuf *)0);
               goto next;
       }

       /*
        * 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) {
               ip = ip_reass((struct ipasfrag *)ip, fp);
               if (ip == 0)
                       goto next;
               hlen = ip->ip_hl << 2;
               m = dtom(ip);
       } else
               if (fp)
                       (void) ip_freef(fp);

       /*
        * Switch out to protocol's input routine.
        */
       (*protosw[ip_protox[ip->ip_p]].pr_input)(m);
       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;
COUNT(IP_REASS);

       /*
        * 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 ipasfrag *)fp;
               fp->ipq_src = ((struct ip *)ip)->ip_src;
               fp->ipq_dst = ((struct ip *)ip)->ip_dst;
       }

       /*
        * 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;
                       m_adj(dtom(q), i);
                       break;
               }
               q = q->ipf_next;
               m_freem(dtom(q->ipf_prev));
               ip_deq(q->ipf_prev);
       }

       /*
        * 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);
       while ((q = q->ipf_next) != (struct ipasfrag *)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;
       ((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 += sizeof (struct ipasfrag);
       m->m_off -= sizeof (struct ipasfrag);
       return ((struct ip *)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 ipasfrag *q;
       struct mbuf *m;
COUNT(IP_FREEF);

       for (q = fp->ipq_next; q != (struct ipasfrag *)fp; q = q->ipf_next)
               m_freem(dtom(q));
       m = dtom(fp);
       fp = fp->next;
       remque(fp->prev);
       (void) 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 ipasfrag *p, *prev;
{

COUNT(IP_ENQ);
       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;
{

COUNT(IP_DEQ);
       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();

COUNT(IP_SLOWTIMO);
       for (fp = ipq.next; fp != &ipq; )
               if (--fp->ipq_ttl == 0)
                       fp = ip_freef(fp);
               else
                       fp = fp->next;
       splx(s);
}

/*
* Drain off all datagram fragments.
*/
ip_drain()
{

COUNT(IP_DRAIN);
       while (ipq.next != &ipq)
               (void) ip_freef(ipq.next);
}

/*
* 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;
       struct in_addr *sin;
       register struct ip_timestamp *ipt;
       register struct ifnet *ifp;
       struct in_addr t;

COUNT(IP_DOOPTIONS);
       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;

               /*
                * 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:
                       if (cp[2] < 4 || cp[2] > optlen - (sizeof (long) - 1))
                               break;
                       sin = (struct in_addr *)(cp + cp[2]);
                       ifp = if_ifwithaddr(*sin);
                       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(ip->ip_dst)==0)
                               goto bad;
                       break;

               case IPOPT_TS:
                       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;
                               /* stamp with ``first'' interface address */
                               *sin++ = ifnet->if_addr;
                               break;

                       case IPOPT_TS_PRESPEC:
                               if (if_ifwithaddr(*sin) == 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;
               }
       }
       return;
bad:
       /* SHOULD FORCE ICMP MESSAGE */
       return;
}

/*
* 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, cp)
       struct ip *ip;
       char *cp;
{
       register int i;
       register struct mbuf *m;
       int olen;
COUNT(IP_STRIPOPTIONS);

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