slirp/src/ip_input.c

   1 /* SPDX-License-Identifier: BSD-3-Clause */
   2 /*
   3  * Copyright (c) 1982, 1986, 1988, 1993
   4  *      The Regents of the University of California.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. Neither the name of the University nor the names of its contributors
  15  *    may be used to endorse or promote products derived from this software
  16  *    without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
  31  * ip_input.c,v 1.11 1994/11/16 10:17:08 jkh Exp
  32  */
  33
  34 /*
  35  * Changes and additions relating to SLiRP are
  36  * Copyright (c) 1995 Danny Gasparovski.
  37  */
  38
  39 #include "slirp.h"
  40 #include "ip_icmp.h"
  41
  42 static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp);
  43 static void ip_freef(Slirp *slirp, struct ipq *fp);
  44 static void ip_enq(register struct ipasfrag *p,
  45                    register struct ipasfrag *prev);
  46 static void ip_deq(register struct ipasfrag *p);
  47
  48 /*
  49  * IP initialization: fill in IP protocol switch table.
  50  * All protocols not implemented in kernel go to raw IP protocol handler.
  51  */
  52 void
  53 ip_init(Slirp *slirp)
  54 {
  55     slirp->ipq.ip_link.next = slirp->ipq.ip_link.prev = &slirp->ipq.ip_link;
  56     udp_init(slirp);
  57     tcp_init(slirp);
  58     icmp_init(slirp);
  59 }
  60
  61 void ip_cleanup(Slirp *slirp)
  62 {
  63     udp_cleanup(slirp);
  64     tcp_cleanup(slirp);
  65     icmp_cleanup(slirp);
  66 }
  67
  68 /*
  69  * Ip input routine.  Checksum and byte swap header.  If fragmented
  70  * try to reassemble.  Process options.  Pass to next level.
  71  */
  72 void
  73 ip_input(struct mbuf *m)
  74 {
  75         Slirp *slirp = m->slirp;
  76         register struct ip *ip;
  77         int hlen;
  78
  79         if (!slirp->in_enabled) {
  80                 goto bad;
  81         }
  82
  83         DEBUG_CALL("ip_input");
  84         DEBUG_ARG("m = %p", m);
  85         DEBUG_ARG("m_len = %d", m->m_len);
  86
  87         if (m->m_len < sizeof (struct ip)) {
  88                 goto bad;
  89         }
  90
  91         ip = mtod(m, struct ip *);
  92
  93         if (ip->ip_v != IPVERSION) {
  94                 goto bad;
  95         }
  96
  97         hlen = ip->ip_hl << 2;
  98         if (hlen<sizeof(struct ip ) || hlen>m->m_len) {/* min header length */
  99           goto bad;                                  /* or packet too short */
 100         }
 101
 102         /* keep ip header intact for ICMP reply
 103          * ip->ip_sum = cksum(m, hlen);
 104          * if (ip->ip_sum) {
 105          */
 106         if(cksum(m,hlen)) {
 107           goto bad;
 108         }
 109
 110         /*
 111          * Convert fields to host representation.
 112          */
 113         NTOHS(ip->ip_len);
 114         if (ip->ip_len < hlen) {
 115                 goto bad;
 116         }
 117         NTOHS(ip->ip_id);
 118         NTOHS(ip->ip_off);
 119
 120         /*
 121          * Check that the amount of data in the buffers
 122          * is as at least much as the IP header would have us expect.
 123          * Trim mbufs if longer than we expect.
 124          * Drop packet if shorter than we expect.
 125          */
 126         if (m->m_len < ip->ip_len) {
 127                 goto bad;
 128         }
 129
 130         /* Should drop packet if mbuf too long? hmmm... */
 131         if (m->m_len > ip->ip_len)
 132            m_adj(m, ip->ip_len - m->m_len);
 133
 134         /* check ip_ttl for a correct ICMP reply */
 135         if (ip->ip_ttl == 0) {
 136             icmp_send_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, "ttl");
 137             goto bad;
 138         }
 139
 140         /*
 141          * If offset or IP_MF are set, must reassemble.
 142          * Otherwise, nothing need be done.
 143          * (We could look in the reassembly queue to see
 144          * if the packet was previously fragmented,
 145          * but it's not worth the time; just let them time out.)
 146          *
 147          * XXX This should fail, don't fragment yet
 148          */
 149         if (ip->ip_off &~ IP_DF) {
 150           register struct ipq *fp;
 151       struct qlink *l;
 152                 /*
 153                  * Look for queue of fragments
 154                  * of this datagram.
 155                  */
 156                 for (l = slirp->ipq.ip_link.next; l != &slirp->ipq.ip_link;
 157                      l = l->next) {
 158             fp = container_of(l, struct ipq, ip_link);
 159             if (ip->ip_id == fp->ipq_id &&
 160                     ip->ip_src.s_addr == fp->ipq_src.s_addr &&
 161                     ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
 162                     ip->ip_p == fp->ipq_p)
 163                     goto found;
 164         }
 165         fp = NULL;
 166         found:
 167
 168                 /*
 169                  * Adjust ip_len to not reflect header,
 170                  * set ip_mff if more fragments are expected,
 171                  * convert offset of this to bytes.
 172                  */
 173                 ip->ip_len -= hlen;
 174                 if (ip->ip_off & IP_MF)
 175                   ip->ip_tos |= 1;
 176                 else
 177                   ip->ip_tos &= ~1;
 178
 179                 ip->ip_off <<= 3;
 180
 181                 /*
 182                  * If datagram marked as having more fragments
 183                  * or if this is not the first fragment,
 184                  * attempt reassembly; if it succeeds, proceed.
 185                  */
 186                 if (ip->ip_tos & 1 || ip->ip_off) {
 187                         ip = ip_reass(slirp, ip, fp);
 188                         if (ip == NULL)
 189                                 return;
 190                         m = dtom(slirp, ip);
 191                 } else
 192                         if (fp)
 193                            ip_freef(slirp, fp);
 194
 195         } else
 196                 ip->ip_len -= hlen;
 197
 198         /*
 199          * Switch out to protocol's input routine.
 200          */
 201         switch (ip->ip_p) {
 202          case IPPROTO_TCP:
 203                 tcp_input(m, hlen, (struct socket *)NULL, AF_INET);
 204                 break;
 205          case IPPROTO_UDP:
 206                 udp_input(m, hlen);
 207                 break;
 208          case IPPROTO_ICMP:
 209                 icmp_input(m, hlen);
 210                 break;
 211          default:
 212                 m_free(m);
 213         }
 214         return;
 215 bad:
 216         m_free(m);
 217 }
 218
 219 #define iptofrag(P) ((struct ipasfrag *)(((char*)(P)) - sizeof(struct qlink)))
 220 #define fragtoip(P) ((struct ip*)(((char*)(P)) + sizeof(struct qlink)))
 221 /*
 222  * Take incoming datagram fragment and try to
 223  * reassemble it into whole datagram.  If a chain for
 224  * reassembly of this datagram already exists, then it
 225  * is given as fp; otherwise have to make a chain.
 226  */
 227 static struct ip *
 228 ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp)
 229 {
 230         register struct mbuf *m = dtom(slirp, ip);
 231         register struct ipasfrag *q;
 232         int hlen = ip->ip_hl << 2;
 233         int i, next;
 234
 235         DEBUG_CALL("ip_reass");
 236         DEBUG_ARG("ip = %p", ip);
 237         DEBUG_ARG("fp = %p", fp);
 238         DEBUG_ARG("m = %p", m);
 239
 240         /*
 241          * Presence of header sizes in mbufs
 242          * would confuse code below.
 243          * Fragment m_data is concatenated.
 244          */
 245         m->m_data += hlen;
 246         m->m_len -= hlen;
 247
 248         /*
 249          * If first fragment to arrive, create a reassembly queue.
 250          */
 251         if (fp == NULL) {
 252           struct mbuf *t = m_get(slirp);
 253
 254           if (t == NULL) {
 255               goto dropfrag;
 256           }
 257           fp = mtod(t, struct ipq *);
 258           insque(&fp->ip_link, &slirp->ipq.ip_link);
 259           fp->ipq_ttl = IPFRAGTTL;
 260           fp->ipq_p = ip->ip_p;
 261           fp->ipq_id = ip->ip_id;
 262           fp->frag_link.next = fp->frag_link.prev = &fp->frag_link;
 263           fp->ipq_src = ip->ip_src;
 264           fp->ipq_dst = ip->ip_dst;
 265           q = (struct ipasfrag *)fp;
 266           goto insert;
 267         }
 268
 269         /*
 270          * Find a segment which begins after this one does.
 271          */
 272         for (q = fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
 273             q = q->ipf_next)
 274                 if (q->ipf_off > ip->ip_off)
 275                         break;
 276
 277         /*
 278          * If there is a preceding segment, it may provide some of
 279          * our data already.  If so, drop the data from the incoming
 280          * segment.  If it provides all of our data, drop us.
 281          */
 282         if (q->ipf_prev != &fp->frag_link) {
 283         struct ipasfrag *pq = q->ipf_prev;
 284                 i = pq->ipf_off + pq->ipf_len - ip->ip_off;
 285                 if (i > 0) {
 286                         if (i >= ip->ip_len)
 287                                 goto dropfrag;
 288                         m_adj(dtom(slirp, ip), i);
 289                         ip->ip_off += i;
 290                         ip->ip_len -= i;
 291                 }
 292         }
 293
 294         /*
 295          * While we overlap succeeding segments trim them or,
 296          * if they are completely covered, dequeue them.
 297          */
 298         while (q != (struct ipasfrag*)&fp->frag_link &&
 299             ip->ip_off + ip->ip_len > q->ipf_off) {
 300                 i = (ip->ip_off + ip->ip_len) - q->ipf_off;
 301                 if (i < q->ipf_len) {
 302                         q->ipf_len -= i;
 303                         q->ipf_off += i;
 304                         m_adj(dtom(slirp, q), i);
 305                         break;
 306                 }
 307                 q = q->ipf_next;
 308                 m_free(dtom(slirp, q->ipf_prev));
 309                 ip_deq(q->ipf_prev);
 310         }
 311
 312 insert:
 313         /*
 314          * Stick new segment in its place;
 315          * check for complete reassembly.
 316          */
 317         ip_enq(iptofrag(ip), q->ipf_prev);
 318         next = 0;
 319         for (q = fp->frag_link.next; q != (struct ipasfrag*)&fp->frag_link;
 320             q = q->ipf_next) {
 321                 if (q->ipf_off != next)
 322                         return NULL;
 323                 next += q->ipf_len;
 324         }
 325         if (((struct ipasfrag *)(q->ipf_prev))->ipf_tos & 1)
 326                 return NULL;
 327
 328         /*
 329          * Reassembly is complete; concatenate fragments.
 330          */
 331     q = fp->frag_link.next;
 332         m = dtom(slirp, q);
 333
 334         q = (struct ipasfrag *) q->ipf_next;
 335         while (q != (struct ipasfrag*)&fp->frag_link) {
 336           struct mbuf *t = dtom(slirp, q);
 337           q = (struct ipasfrag *) q->ipf_next;
 338           m_cat(m, t);
 339         }
 340
 341         /*
 342          * Create header for new ip packet by
 343          * modifying header of first packet;
 344          * dequeue and discard fragment reassembly header.
 345          * Make header visible.
 346          */
 347         q = fp->frag_link.next;
 348
 349         /*
 350          * If the fragments concatenated to an mbuf that's
 351          * bigger than the total size of the fragment, then and
 352          * m_ext buffer was alloced. But fp->ipq_next points to
 353          * the old buffer (in the mbuf), so we must point ip
 354          * into the new buffer.
 355          */
 356         if (m->m_flags & M_EXT) {
 357           int delta = (char *)q - m->m_dat;
 358           q = (struct ipasfrag *)(m->m_ext + delta);
 359         }
 360
 361     ip = fragtoip(q);
 362         ip->ip_len = next;
 363         ip->ip_tos &= ~1;
 364         ip->ip_src = fp->ipq_src;
 365         ip->ip_dst = fp->ipq_dst;
 366         remque(&fp->ip_link);
 367         (void) m_free(dtom(slirp, fp));
 368         m->m_len += (ip->ip_hl << 2);
 369         m->m_data -= (ip->ip_hl << 2);
 370
 371         return ip;
 372
 373 dropfrag:
 374         m_free(m);
 375         return NULL;
 376 }
 377
 378 /*
 379  * Free a fragment reassembly header and all
 380  * associated datagrams.
 381  */
 382 static void
 383 ip_freef(Slirp *slirp, struct ipq *fp)
 384 {
 385         register struct ipasfrag *q, *p;
 386
 387         for (q = fp->frag_link.next; q != (struct ipasfrag*)&fp->frag_link; q = p) {
 388                 p = q->ipf_next;
 389                 ip_deq(q);
 390                 m_free(dtom(slirp, q));
 391         }
 392         remque(&fp->ip_link);
 393         (void) m_free(dtom(slirp, fp));
 394 }
 395
 396 /*
 397  * Put an ip fragment on a reassembly chain.
 398  * Like insque, but pointers in middle of structure.
 399  */
 400 static void
 401 ip_enq(register struct ipasfrag *p, register struct ipasfrag *prev)
 402 {
 403         DEBUG_CALL("ip_enq");
 404         DEBUG_ARG("prev = %p", prev);
 405         p->ipf_prev =  prev;
 406         p->ipf_next = prev->ipf_next;
 407         ((struct ipasfrag *)(prev->ipf_next))->ipf_prev = p;
 408         prev->ipf_next = p;
 409 }
 410
 411 /*
 412  * To ip_enq as remque is to insque.
 413  */
 414 static void
 415 ip_deq(register struct ipasfrag *p)
 416 {
 417         ((struct ipasfrag *)(p->ipf_prev))->ipf_next = p->ipf_next;
 418         ((struct ipasfrag *)(p->ipf_next))->ipf_prev = p->ipf_prev;
 419 }
 420
 421 /*
 422  * IP timer processing;
 423  * if a timer expires on a reassembly
 424  * queue, discard it.
 425  */
 426 void
 427 ip_slowtimo(Slirp *slirp)
 428 {
 429     struct qlink *l;
 430
 431         DEBUG_CALL("ip_slowtimo");
 432
 433     l = slirp->ipq.ip_link.next;
 434
 435         if (l == NULL)
 436            return;
 437
 438     while (l != &slirp->ipq.ip_link) {
 439         struct ipq *fp = container_of(l, struct ipq, ip_link);
 440         l = l->next;
 441                 if (--fp->ipq_ttl == 0) {
 442                         ip_freef(slirp, fp);
 443                 }
 444     }
 445 }
 446
 447 /*
 448  * Strip out IP options, at higher
 449  * level protocol in the kernel.
 450  * Second argument is buffer to which options
 451  * will be moved, and return value is their length.
 452  * (XXX) should be deleted; last arg currently ignored.
 453  */
 454 void
 455 ip_stripoptions(register struct mbuf *m, struct mbuf *mopt)
 456 {
 457         register int i;
 458         struct ip *ip = mtod(m, struct ip *);
 459         register char *opts;
 460         int olen;
 461
 462         olen = (ip->ip_hl<<2) - sizeof (struct ip);
 463         opts = (char *)(ip + 1);
 464         i = m->m_len - (sizeof (struct ip) + olen);
 465         memcpy(opts, opts  + olen, (unsigned)i);
 466         m->m_len -= olen;
 467
 468         ip->ip_hl = sizeof(struct ip) >> 2;
 469 }