/* $OpenBSD: frag6.c,v 1.89 2024/07/29 12:41:30 bluhm Exp $ */ /* $KAME: frag6.c,v 1.40 2002/05/27 21:40:31 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 /* for ECN definitions */ /* Protects `frag6_queue', `frag6_nfragpackets' and `frag6_nfrags'. */ struct mutex frag6_mutex = MUTEX_INITIALIZER(IPL_SOFTNET); u_int frag6_nfragpackets; u_int frag6_nfrags; TAILQ_HEAD(ip6q_head, ip6q) frag6_queue; /* ip6 reassemble queue */ void frag6_freef(struct ip6q *); void frag6_unlink(struct ip6q *, struct ip6q_head *); struct pool ip6af_pool; struct pool ip6q_pool; /* * Initialise reassembly queue and pools. */ void frag6_init(void) { pool_init(&ip6af_pool, sizeof(struct ip6asfrag), 0, IPL_SOFTNET, 0, "ip6af", NULL); pool_init(&ip6q_pool, sizeof(struct ip6q), 0, IPL_SOFTNET, 0, "ip6q", NULL); TAILQ_INIT(&frag6_queue); } /* * 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(struct mbuf **mp, int *offp, int proto, int af) { struct mbuf *m = *mp, *t; struct ip6_hdr *ip6; struct ip6_frag *ip6f; struct ip6q *q6; struct ip6asfrag *af6, *ip6af, *naf6, *paf6; int offset = *offp, nxt, i, next; int first_frag = 0; int fragoff, frgpartlen; /* must be larger than u_int16_t */ u_int8_t ecn, ecn0; ip6 = mtod(m, struct ip6_hdr *); IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f)); if (ip6f == NULL) return IPPROTO_DONE; /* jumbo payload can't contain a fragment header */ if (ip6->ip6_plen == 0) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset); 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)); return IPPROTO_DONE; } ip6stat_inc(ip6s_fragments); /* offset now points to data portion */ offset += sizeof(struct ip6_frag); /* * RFC6946: A host that receives an IPv6 packet which includes * a Fragment Header with the "Fragment Offset" equal to 0 and * the "M" bit equal to 0 MUST process such packet in isolation * from any other packets/fragments. */ fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK); if (fragoff == 0 && !(ip6f->ip6f_offlg & IP6F_MORE_FRAG)) { ip6stat_inc(ip6s_reassembled); *offp = offset; return ip6f->ip6f_nxt; } /* Ignore empty non atomic fragment, do not classify as overlapping. */ if (sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) <= offset) { m_freem(m); return IPPROTO_DONE; } mtx_enter(&frag6_mutex); /* * Enforce upper bound on number of fragments. * If maxfrag is 0, never accept fragments. * If maxfrag is -1, accept all fragments without limitation. */ if (ip6_maxfrags >= 0 && frag6_nfrags >= (u_int)ip6_maxfrags) { mtx_leave(&frag6_mutex); goto dropfrag; } TAILQ_FOREACH(q6, &frag6_queue, ip6q_queue) 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 == NULL) { /* * the first fragment to arrive, create a reassembly queue. */ first_frag = 1; /* * Enforce upper bound on number of fragmented packets * for which we attempt reassembly; * If maxfragpackets is 0, never accept fragments. * If maxfragpackets is -1, accept all fragments without * limitation. */ if (ip6_maxfragpackets >= 0 && frag6_nfragpackets >= (u_int)ip6_maxfragpackets) { mtx_leave(&frag6_mutex); goto dropfrag; } frag6_nfragpackets++; q6 = pool_get(&ip6q_pool, PR_NOWAIT | PR_ZERO); if (q6 == NULL) { mtx_leave(&frag6_mutex); goto dropfrag; } TAILQ_INSERT_HEAD(&frag6_queue, q6, ip6q_queue); /* ip6q_nxt will be filled afterwards, from 1st fragment */ LIST_INIT(&q6->ip6q_asfrag); q6->ip6q_ident = ip6f->ip6f_ident; q6->ip6q_ttl = IPV6_FRAGTTL; q6->ip6q_src = ip6->ip6_src; q6->ip6q_dst = ip6->ip6_dst; q6->ip6q_ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK; q6->ip6q_unfrglen = -1; /* The 1st fragment has not arrived. */ q6->ip6q_nfrag = 0; } /* * If it's the 1st fragment, record the length of the * unfragmentable part and the next header of the fragment header. */ 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) { mtx_leave(&frag6_mutex); 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) { mtx_leave(&frag6_mutex); 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) { LIST_FOREACH_SAFE(af6, &q6->ip6q_asfrag, ip6af_list, naf6) { if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen > IPV6_MAXPACKET) { struct mbuf *merr = af6->ip6af_m; struct ip6_hdr *ip6err; int erroff = af6->ip6af_offset; /* dequeue the fragment. */ LIST_REMOVE(af6, ip6af_list); pool_put(&ip6af_pool, af6); /* 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 = pool_get(&ip6af_pool, PR_NOWAIT | PR_ZERO); if (ip6af == NULL) { mtx_leave(&frag6_mutex); goto dropfrag; } ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG; ip6af->ip6af_off = fragoff; ip6af->ip6af_frglen = frgpartlen; ip6af->ip6af_offset = offset; ip6af->ip6af_m = m; if (first_frag) { paf6 = NULL; goto insert; } /* * Handle ECN by comparing this segment with the first one; * if CE is set, do not lose CE. * drop if CE and not-ECT are mixed for the same packet. */ ecn = (ntohl(ip6->ip6_flow) >> 20) & IPTOS_ECN_MASK; ecn0 = q6->ip6q_ecn; if (ecn == IPTOS_ECN_CE) { if (ecn0 == IPTOS_ECN_NOTECT) { mtx_leave(&frag6_mutex); pool_put(&ip6af_pool, ip6af); goto dropfrag; } if (ecn0 != IPTOS_ECN_CE) q6->ip6q_ecn = IPTOS_ECN_CE; } if (ecn == IPTOS_ECN_NOTECT && ecn0 != IPTOS_ECN_NOTECT) { mtx_leave(&frag6_mutex); pool_put(&ip6af_pool, ip6af); goto dropfrag; } /* * Find a segment which begins after this one does. */ for (paf6 = NULL, af6 = LIST_FIRST(&q6->ip6q_asfrag); af6 != NULL; paf6 = af6, af6 = LIST_NEXT(af6, ip6af_list)) if (af6->ip6af_off > ip6af->ip6af_off) break; /* * RFC 5722, Errata 3089: When reassembling an IPv6 datagram, if one * or more its constituent fragments is determined to be an overlapping * fragment, the entire datagram (and any constituent fragments) MUST * be silently discarded. */ if (paf6 != NULL) { i = (paf6->ip6af_off + paf6->ip6af_frglen) - ip6af->ip6af_off; if (i > 0) goto flushfrags; } if (af6 != NULL) { i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off; if (i > 0) goto flushfrags; } 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. */ if (paf6 != NULL) LIST_INSERT_AFTER(paf6, ip6af, ip6af_list); else LIST_INSERT_HEAD(&q6->ip6q_asfrag, ip6af, ip6af_list); frag6_nfrags++; q6->ip6q_nfrag++; next = 0; for (paf6 = NULL, af6 = LIST_FIRST(&q6->ip6q_asfrag); af6 != NULL; paf6 = af6, af6 = LIST_NEXT(af6, ip6af_list)) { if (af6->ip6af_off != next) { mtx_leave(&frag6_mutex); return IPPROTO_DONE; } next += af6->ip6af_frglen; } if (paf6->ip6af_mff) { mtx_leave(&frag6_mutex); return IPPROTO_DONE; } /* * Reassembly is complete; concatenate fragments. */ ip6af = LIST_FIRST(&q6->ip6q_asfrag); LIST_REMOVE(ip6af, ip6af_list); t = m = ip6af->ip6af_m; while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) { LIST_REMOVE(af6, ip6af_list); while (t->m_next) t = t->m_next; t->m_next = af6->ip6af_m; m_adj(t->m_next, af6->ip6af_offset); m_removehdr(t->m_next); pool_put(&ip6af_pool, af6); } /* adjust offset to point where the original next header starts */ offset = ip6af->ip6af_offset - sizeof(struct ip6_frag); pool_put(&ip6af_pool, ip6af); next += offset - sizeof(struct ip6_hdr); if ((u_int)next > IPV6_MAXPACKET) { TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue); frag6_nfrags -= q6->ip6q_nfrag; frag6_nfragpackets--; mtx_leave(&frag6_mutex); pool_put(&ip6q_pool, q6); goto dropfrag; } ip6 = mtod(m, struct ip6_hdr *); ip6->ip6_plen = htons(next); ip6->ip6_src = q6->ip6q_src; ip6->ip6_dst = q6->ip6q_dst; if (q6->ip6q_ecn == IPTOS_ECN_CE) ip6->ip6_flow |= htonl(IPTOS_ECN_CE << 20); nxt = q6->ip6q_nxt; /* Delete frag6 header */ if (frag6_deletefraghdr(m, offset) != 0) { TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue); frag6_nfrags -= q6->ip6q_nfrag; frag6_nfragpackets--; mtx_leave(&frag6_mutex); pool_put(&ip6q_pool, q6); goto dropfrag; } TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue); frag6_nfrags -= q6->ip6q_nfrag; frag6_nfragpackets--; mtx_leave(&frag6_mutex); pool_put(&ip6q_pool, q6); m_calchdrlen(m); /* * Restore NXT to the original. */ { int prvnxt = ip6_get_prevhdr(m, offset); uint8_t *prvnxtp; IP6_EXTHDR_GET(prvnxtp, uint8_t *, m, prvnxt, sizeof(*prvnxtp)); if (prvnxtp == NULL) goto dropfrag; *prvnxtp = nxt; } ip6stat_inc(ip6s_reassembled); /* * Tell launch routine the next header */ *mp = m; *offp = offset; return nxt; flushfrags: TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue); frag6_nfrags -= q6->ip6q_nfrag; frag6_nfragpackets--; mtx_leave(&frag6_mutex); pool_put(&ip6af_pool, ip6af); while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) { LIST_REMOVE(af6, ip6af_list); m_freem(af6->ip6af_m); pool_put(&ip6af_pool, af6); } ip6stat_add(ip6s_fragdropped, q6->ip6q_nfrag + 1); pool_put(&ip6q_pool, q6); m_freem(m); return IPPROTO_DONE; dropfrag: ip6stat_inc(ip6s_fragdropped); m_freem(m); return IPPROTO_DONE; } /* * Delete fragment header after the unfragmentable header portions. */ int frag6_deletefraghdr(struct mbuf *m, int offset) { struct mbuf *t; if (m->m_len >= offset + sizeof(struct ip6_frag)) { memmove(mtod(m, caddr_t) + sizeof(struct ip6_frag), mtod(m, caddr_t), 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) return (ENOBUFS); m_adj(t, sizeof(struct ip6_frag)); m_cat(m, t); } return (0); } /* * Free a fragment reassembly header and all * associated datagrams. * The header must not be in any queue. */ void frag6_freef(struct ip6q *q6) { struct ip6asfrag *af6; while ((af6 = LIST_FIRST(&q6->ip6q_asfrag)) != NULL) { struct mbuf *m = af6->ip6af_m; LIST_REMOVE(af6, ip6af_list); /* * 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 *); /* restore source and destination addresses */ ip6->ip6_src = q6->ip6q_src; ip6->ip6_dst = q6->ip6q_dst; NET_LOCK_SHARED(); icmp6_error(m, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_REASSEMBLY, 0); NET_UNLOCK_SHARED(); } else m_freem(m); pool_put(&ip6af_pool, af6); } pool_put(&ip6q_pool, q6); } /* * Unlinks a fragment reassembly header from the reassembly queue * and inserts it into a given remove queue. */ void frag6_unlink(struct ip6q *q6, struct ip6q_head *rmq6) { MUTEX_ASSERT_LOCKED(&frag6_mutex); TAILQ_REMOVE(&frag6_queue, q6, ip6q_queue); TAILQ_INSERT_HEAD(rmq6, q6, ip6q_queue); frag6_nfrags -= q6->ip6q_nfrag; frag6_nfragpackets--; } /* * IPv6 reassembling timer processing; * if a timer expires on a reassembly * queue, discard it. */ void frag6_slowtimo(void) { struct ip6q_head rmq6; struct ip6q *q6, *nq6; TAILQ_INIT(&rmq6); mtx_enter(&frag6_mutex); TAILQ_FOREACH_SAFE(q6, &frag6_queue, ip6q_queue, nq6) { if (--q6->ip6q_ttl == 0) { ip6stat_inc(ip6s_fragtimeout); frag6_unlink(q6, &rmq6); } } /* * 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 && !TAILQ_EMPTY(&frag6_queue)) { ip6stat_inc(ip6s_fragoverflow); frag6_unlink(TAILQ_LAST(&frag6_queue, ip6q_head), &rmq6); } mtx_leave(&frag6_mutex); while ((q6 = TAILQ_FIRST(&rmq6)) != NULL) { TAILQ_REMOVE(&rmq6, q6, ip6q_queue); frag6_freef(q6); } }