/* $OpenBSD: frag6.c,v 1.5 2000/02/04 18:11:38 itojun Exp $ */ /* * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Define it to get a correct behavior on per-interface statistics. * You will need to perform an extra routing table lookup, per fragment, * to do it. This may, or may not be, a performance hit. */ #define IN6_IFSTAT_STRICT static void frag6_enq __P((struct ip6asfrag *, struct ip6asfrag *)); static void frag6_deq __P((struct ip6asfrag *)); static void frag6_insque __P((struct ip6q *, struct ip6q *)); static void frag6_remque __P((struct ip6q *)); static void frag6_freef __P((struct ip6q *)); int frag6_doing_reass; u_int frag6_nfragpackets; struct ip6q ip6q; /* ip6 reassemble queue */ #ifndef offsetof /* XXX */ #define offsetof(type, member) ((size_t)(&((type *)0)->member)) #endif /* * Initialise reassembly queue and fragment identifier. */ void frag6_init() { ip6_id = arc4random(); ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q; } /* * In RFC2460, fragment and reassembly rule do not agree with each other, * in terms of next header field handling in fragment header. * While the sender will use the same value for all of the fragmented packets, * receiver is suggested not to check the consistency. * * fragment rule (p20): * (2) A Fragment header containing: * The Next Header value that identifies the first header of * the Fragmentable Part of the original packet. * -> next header field is same for all fragments * * reassembly rule (p21): * The Next Header field of the last header of the Unfragmentable * Part is obtained from the Next Header field of the first * fragment's Fragment header. * -> should grab it from the first fragment only * * The following note also contradicts with fragment rule - noone is going to * send different fragment with different next header field. * * additional note (p22): * The Next Header values in the Fragment headers of different * fragments of the same original packet may differ. Only the value * from the Offset zero fragment packet is used for reassembly. * -> should grab it from the first fragment only * * There is no explicit reason given in the RFC. Historical reason maybe? */ /* * Fragment input */ int frag6_input(mp, offp, proto) struct mbuf **mp; int *offp, proto; { struct mbuf *m = *mp, *t; struct ip6_hdr *ip6; struct ip6_frag *ip6f; struct ip6q *q6; struct ip6asfrag *af6, *ip6af, *af6dwn; int offset = *offp, nxt, i, next; int first_frag = 0; int fragoff, frgpartlen; /* must be larger than u_int16_t */ struct ifnet *dstifp; #ifdef IN6_IFSTAT_STRICT static struct route_in6 ro; struct sockaddr_in6 *dst; #endif ip6 = mtod(m, struct ip6_hdr *); #ifndef PULLDOWN_TEST IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE); ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset); #else IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f)); if (ip6f == NULL) return IPPROTO_DONE; #endif dstifp = NULL; #ifdef IN6_IFSTAT_STRICT /* find the destination interface of the packet. */ dst = (struct sockaddr_in6 *)&ro.ro_dst; if (ro.ro_rt && ((ro.ro_rt->rt_flags & RTF_UP) == 0 || !IN6_ARE_ADDR_EQUAL(&dst->sin6_addr, &ip6->ip6_dst))) { RTFREE(ro.ro_rt); ro.ro_rt = (struct rtentry *)0; } if (ro.ro_rt == NULL) { bzero(dst, sizeof(*dst)); dst->sin6_family = AF_INET6; dst->sin6_len = sizeof(struct sockaddr_in6); dst->sin6_addr = ip6->ip6_dst; } rtalloc((struct route *)&ro); if (ro.ro_rt != NULL && ro.ro_rt->rt_ifa != NULL) dstifp = ((struct in6_ifaddr *)ro.ro_rt->rt_ifa)->ia_ifp; #else /* we are violating the spec, this is not the destination interface */ if ((m->m_flags & M_PKTHDR) != 0) dstifp = m->m_pkthdr.rcvif; #endif /* jumbo payload can't contain a fragment header */ if (ip6->ip6_plen == 0) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset); in6_ifstat_inc(dstifp, ifs6_reass_fail); return IPPROTO_DONE; } /* * check whether fragment packet's fragment length is * multiple of 8 octets. * sizeof(struct ip6_frag) == 8 * sizeof(struct ip6_hdr) = 40 */ if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) && (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offsetof(struct ip6_hdr, ip6_plen)); in6_ifstat_inc(dstifp, ifs6_reass_fail); return IPPROTO_DONE; } ip6stat.ip6s_fragments++; in6_ifstat_inc(dstifp, ifs6_reass_reqd); /* offset now points to data portion */ offset += sizeof(struct ip6_frag); for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next) if (ip6f->ip6f_ident == q6->ip6q_ident && IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) && IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst)) break; if (q6 == &ip6q) { /* * the first fragment to arrive, create a reassembly queue. */ first_frag = 1; frag6_nfragpackets++; /* * Enforce upper bound on number of fragmented packets * for which we attempt reassembly; * If maxfrag is 0, never accept fragments. * If maxfrag is -1, accept all fragments without limitation. */ if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets) { ip6stat.ip6s_fragoverflow++; in6_ifstat_inc(dstifp, ifs6_reass_fail); frag6_freef(ip6q.ip6q_prev); } q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE, M_DONTWAIT); if (q6 == NULL) goto dropfrag; bzero(q6, sizeof(*q6)); frag6_insque(q6, &ip6q); /* ip6q_nxt will be filled afterwards, from 1st fragment */ q6->ip6q_down = q6->ip6q_up = (struct ip6asfrag *)q6; #ifdef notyet q6->ip6q_nxtp = (u_char *)nxtp; #endif q6->ip6q_ident = ip6f->ip6f_ident; q6->ip6q_arrive = 0; /* Is it used anywhere? */ q6->ip6q_ttl = IPV6_FRAGTTL; q6->ip6q_src = ip6->ip6_src; q6->ip6q_dst = ip6->ip6_dst; q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */ } /* * If it's the 1st fragment, record the length of the * unfragmentable part and the next header of the fragment header. */ fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK); if (fragoff == 0) { q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr) - sizeof(struct ip6_frag); q6->ip6q_nxt = ip6f->ip6f_nxt; } /* * Check that the reassembled packet would not exceed 65535 bytes * in size. * If it would exceed, discard the fragment and return an ICMP error. */ frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset; if (q6->ip6q_unfrglen >= 0) { /* The 1st fragment has already arrived. */ if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset - sizeof(struct ip6_frag) + offsetof(struct ip6_frag, ip6f_offlg)); return(IPPROTO_DONE); } } else if (fragoff + frgpartlen > IPV6_MAXPACKET) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset - sizeof(struct ip6_frag) + offsetof(struct ip6_frag, ip6f_offlg)); return(IPPROTO_DONE); } /* * If it's the first fragment, do the above check for each * fragment already stored in the reassembly queue. */ if (fragoff == 0) { for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = af6dwn) { af6dwn = af6->ip6af_down; if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen > IPV6_MAXPACKET) { struct mbuf *merr = IP6_REASS_MBUF(af6); struct ip6_hdr *ip6err; int erroff = af6->ip6af_offset; /* dequeue the fragment. */ frag6_deq(af6); free(af6, M_FTABLE); /* adjust pointer. */ ip6err = mtod(merr, struct ip6_hdr *); /* * Restore source and destination addresses * in the erroneous IPv6 header. */ ip6err->ip6_src = q6->ip6q_src; ip6err->ip6_dst = q6->ip6q_dst; icmp6_error(merr, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, erroff - sizeof(struct ip6_frag) + offsetof(struct ip6_frag, ip6f_offlg)); } } } ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE, M_DONTWAIT); if (ip6af == NULL) goto dropfrag; bzero(ip6af, sizeof(*ip6af)); ip6af->ip6af_head = ip6->ip6_flow; ip6af->ip6af_len = ip6->ip6_plen; ip6af->ip6af_nxt = ip6->ip6_nxt; ip6af->ip6af_hlim = ip6->ip6_hlim; ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG; ip6af->ip6af_off = fragoff; ip6af->ip6af_frglen = frgpartlen; ip6af->ip6af_offset = offset; IP6_REASS_MBUF(ip6af) = m; if (first_frag) { af6 = (struct ip6asfrag *)q6; goto insert; } /* * Find a segment which begins after this one does. */ for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = af6->ip6af_down) if (af6->ip6af_off > ip6af->ip6af_off) break; #if 0 /* * 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 (af6->ip6af_up != (struct ip6asfrag *)q6) { i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen - ip6af->ip6af_off; if (i > 0) { if (i >= ip6af->ip6af_frglen) goto dropfrag; m_adj(IP6_REASS_MBUF(ip6af), i); ip6af->ip6af_off += i; ip6af->ip6af_frglen -= i; } } /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (af6 != (struct ip6asfrag *)q6 && ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) { i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off; if (i < af6->ip6af_frglen) { af6->ip6af_frglen -= i; af6->ip6af_off += i; m_adj(IP6_REASS_MBUF(af6), i); break; } af6 = af6->ip6af_down; m_freem(IP6_REASS_MBUF(af6->ip6af_up)); frag6_deq(af6->ip6af_up); } #else /* * If the incoming framgent overlaps some existing fragments in * the reassembly queue, drop it, since it is dangerous to override * existing fragments from a security point of view. */ if (af6->ip6af_up != (struct ip6asfrag *)q6) { i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen - ip6af->ip6af_off; if (i > 0) { log(LOG_ERR, "%d bytes of a fragment from %s " "overlaps the previous fragment\n", i, ip6_sprintf(&q6->ip6q_src)); goto dropfrag; } } if (af6 != (struct ip6asfrag *)q6) { i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off; if (i > 0) { log(LOG_ERR, "%d bytes of a fragment from %s " "overlaps the succeeding fragment", i, ip6_sprintf(&q6->ip6q_src)); goto dropfrag; } } #endif insert: /* * Stick new segment in its place; * check for complete reassembly. * Move to front of packet queue, as we are * the most recently active fragmented packet. */ frag6_enq(ip6af, af6->ip6af_up); #if 0 /* xxx */ if (q6 != ip6q.ip6q_next) { frag6_remque(q6); frag6_insque(q6, &ip6q); } #endif next = 0; for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = af6->ip6af_down) { if (af6->ip6af_off != next) { frag6_doing_reass = 0; return IPPROTO_DONE; } next += af6->ip6af_frglen; } if (af6->ip6af_up->ip6af_mff) { frag6_doing_reass = 0; return IPPROTO_DONE; } /* * Reassembly is complete; concatenate fragments. */ ip6af = q6->ip6q_down; t = m = IP6_REASS_MBUF(ip6af); af6 = ip6af->ip6af_down; frag6_deq(ip6af); while (af6 != (struct ip6asfrag *)q6) { af6dwn = af6->ip6af_down; frag6_deq(af6); while (t->m_next) t = t->m_next; t->m_next = IP6_REASS_MBUF(af6); m_adj(t->m_next, af6->ip6af_offset); free(af6, M_FTABLE); af6 = af6dwn; } /* adjust offset to point where the original next header starts */ offset = ip6af->ip6af_offset - sizeof(struct ip6_frag); free(ip6af, M_FTABLE); ip6 = mtod(m, struct ip6_hdr *); ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr)); ip6->ip6_src = q6->ip6q_src; ip6->ip6_dst = q6->ip6q_dst; nxt = q6->ip6q_nxt; #ifdef notyet *q6->ip6q_nxtp = (u_char)(nxt & 0xff); #endif /* * Delete frag6 header with as a few cost as possible. */ if (offset < m->m_len) { ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag), offset); m->m_data += sizeof(struct ip6_frag); m->m_len -= sizeof(struct ip6_frag); } else { /* this comes with no copy if the boundary is on cluster */ if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) { frag6_remque(q6); free(q6, M_FTABLE); frag6_nfragpackets--; goto dropfrag; } m_adj(t, sizeof(struct ip6_frag)); m_cat(m, t); } /* * Store NXT to the original. */ { char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */ *prvnxtp = nxt; } frag6_remque(q6); free(q6, M_FTABLE); frag6_nfragpackets--; if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */ int plen = 0; for (t = m; t; t = t->m_next) plen += t->m_len; m->m_pkthdr.len = plen; } ip6stat.ip6s_reassembled++; in6_ifstat_inc(dstifp, ifs6_reass_ok); /* * Tell launch routine the next header */ *mp = m; *offp = offset; frag6_doing_reass = 0; return nxt; dropfrag: in6_ifstat_inc(dstifp, ifs6_reass_fail); ip6stat.ip6s_fragdropped++; m_freem(m); return IPPROTO_DONE; } /* * Free a fragment reassembly header and all * associated datagrams. */ void frag6_freef(q6) struct ip6q *q6; { struct ip6asfrag *af6, *down6; for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = down6) { struct mbuf *m = IP6_REASS_MBUF(af6); down6 = af6->ip6af_down; frag6_deq(af6); /* * Return ICMP time exceeded error for the 1st fragment. * Just free other fragments. */ if (af6->ip6af_off == 0) { struct ip6_hdr *ip6; /* adjust pointer */ ip6 = mtod(m, struct ip6_hdr *); /* restoure source and destination addresses */ ip6->ip6_src = q6->ip6q_src; ip6->ip6_dst = q6->ip6q_dst; icmp6_error(m, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_REASSEMBLY, 0); } else m_freem(m); free(af6, M_FTABLE); } frag6_remque(q6); free(q6, M_FTABLE); frag6_nfragpackets--; } /* * Put an ip fragment on a reassembly chain. * Like insque, but pointers in middle of structure. */ void frag6_enq(af6, up6) struct ip6asfrag *af6, *up6; { af6->ip6af_up = up6; af6->ip6af_down = up6->ip6af_down; up6->ip6af_down->ip6af_up = af6; up6->ip6af_down = af6; } /* * To frag6_enq as remque is to insque. */ void frag6_deq(af6) struct ip6asfrag *af6; { af6->ip6af_up->ip6af_down = af6->ip6af_down; af6->ip6af_down->ip6af_up = af6->ip6af_up; } void frag6_insque(new, old) struct ip6q *new, *old; { new->ip6q_prev = old; new->ip6q_next = old->ip6q_next; old->ip6q_next->ip6q_prev= new; old->ip6q_next = new; } void frag6_remque(p6) struct ip6q *p6; { p6->ip6q_prev->ip6q_next = p6->ip6q_next; p6->ip6q_next->ip6q_prev = p6->ip6q_prev; } /* * IP timer processing; * if a timer expires on a reassembly * queue, discard it. */ void frag6_slowtimo() { struct ip6q *q6; int s = splnet(); #if 0 extern struct route_in6 ip6_forward_rt; #endif frag6_doing_reass = 1; q6 = ip6q.ip6q_next; if (q6) while (q6 != &ip6q) { --q6->ip6q_ttl; q6 = q6->ip6q_next; if (q6->ip6q_prev->ip6q_ttl == 0) { ip6stat.ip6s_fragtimeout++; /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */ frag6_freef(q6->ip6q_prev); } } /* * If we are over the maximum number of fragments * (due to the limit being lowered), drain off * enough to get down to the new limit. */ while (frag6_nfragpackets > (u_int)ip6_maxfragpackets) { ip6stat.ip6s_fragoverflow++; /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */ frag6_freef(ip6q.ip6q_prev); } frag6_doing_reass = 0; #if 0 /* * Routing changes might produce a better route than we last used; * make sure we notice eventually, even if forwarding only for one * destination and the cache is never replaced. */ if (ip6_forward_rt.ro_rt) { RTFREE(ip6_forward_rt.ro_rt); ip6_forward_rt.ro_rt = 0; } if (ipsrcchk_rt.ro_rt) { RTFREE(ipsrcchk_rt.ro_rt); ipsrcchk_rt.ro_rt = 0; } #endif splx(s); } /* * Drain off all datagram fragments. */ void frag6_drain() { if (frag6_doing_reass) return; while (ip6q.ip6q_next != &ip6q) { ip6stat.ip6s_fragdropped++; /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */ frag6_freef(ip6q.ip6q_next); } }