/* $NetBSD: frag6.c,v 1.76.2.2 2024/09/13 14:42:16 martin 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 __KERNEL_RCSID(0, "$NetBSD: frag6.c,v 1.76.2.2 2024/09/13 14:42:16 martin Exp $"); #ifdef _KERNEL_OPT #include "opt_net_mpsafe.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * IPv6 reassembly queue structure. Each fragment being reassembled is * attached to one of these structures. * * XXX: Would be better to use TAILQ. */ struct ip6q { u_int32_t ip6q_head; u_int16_t ip6q_len; u_int8_t ip6q_nxt; /* ip6f_nxt in first fragment */ u_int8_t ip6q_hlim; struct ip6asfrag *ip6q_down; struct ip6asfrag *ip6q_up; u_int32_t ip6q_ident; u_int8_t ip6q_ttl; struct in6_addr ip6q_src, ip6q_dst; struct ip6q *ip6q_next; struct ip6q *ip6q_prev; int ip6q_unfrglen; /* len of unfragmentable part */ int ip6q_nfrag; /* # of fragments */ int ip6q_ipsec; /* IPsec flags */ }; struct ip6asfrag { u_int32_t ip6af_head; u_int16_t ip6af_len; u_int8_t ip6af_nxt; u_int8_t ip6af_hlim; /* must not override the above members during reassembling */ struct ip6asfrag *ip6af_down; struct ip6asfrag *ip6af_up; struct mbuf *ip6af_m; int ip6af_offset; /* offset in ip6af_m to next header */ int ip6af_frglen; /* fragmentable part length */ int ip6af_off; /* fragment offset */ bool ip6af_mff; /* more fragment bit in frag off */ }; static void frag6_enq(struct ip6asfrag *, struct ip6asfrag *); static void frag6_deq(struct ip6asfrag *); static void frag6_insque(struct ip6q *, struct ip6q *); static void frag6_remque(struct ip6q *); static void frag6_freef(struct ip6q *); static int frag6_drainwanted; static u_int frag6_nfragpackets; static u_int frag6_nfrags; static struct ip6q ip6q; /* ip6 reassembly queue */ /* Protects ip6q */ static kmutex_t frag6_lock __cacheline_aligned; /* * Initialise reassembly queue and fragment identifier. */ void frag6_init(void) { ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q; mutex_init(&frag6_lock, MUTEX_DEFAULT, IPL_NONE); } static void frag6_dropfrag(struct ip6q *q6) { frag6_remque(q6); frag6_nfrags -= q6->ip6q_nfrag; kmem_intr_free(q6, sizeof(*q6)); frag6_nfragpackets--; } /* * IPv6 fragment input. * * 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? * * XXX: It would be better to use a pool, rather than kmem. */ int frag6_input(struct mbuf **mp, int *offp, int proto) { struct rtentry *rt; 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 ipsecflags = m->m_flags & (M_DECRYPTED|M_AUTHIPHDR); int first_frag = 0; int fragoff, frgpartlen; /* must be larger than u_int16_t */ struct ifnet *dstifp; static struct route ro; union { struct sockaddr dst; struct sockaddr_in6 dst6; } u; ip6 = mtod(m, struct ip6_hdr *); IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f)); if (ip6f == NULL) return IPPROTO_DONE; dstifp = NULL; /* find the destination interface of the packet. */ sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); if ((rt = rtcache_lookup(&ro, &u.dst)) != NULL) dstifp = ((struct in6_ifaddr *)rt->rt_ifa)->ia_ifp; /* 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); goto done; } /* * Check whether fragment packet's fragment length is non-zero and * multiple of 8 octets. * sizeof(struct ip6_frag) == 8 * sizeof(struct ip6_hdr) = 40 */ frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset - sizeof(struct ip6_frag); if ((frgpartlen == 0) || ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) && (frgpartlen & 0x7) != 0)) { icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offsetof(struct ip6_hdr, ip6_plen)); in6_ifstat_inc(dstifp, ifs6_reass_fail); goto done; } IP6_STATINC(IP6_STAT_FRAGMENTS); in6_ifstat_inc(dstifp, ifs6_reass_reqd); /* 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. * * XXX: Would be better to remove this fragment header entirely, * for us not to get confused later when looking back at the * previous headers in the chain. */ fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK); if (fragoff == 0 && !(ip6f->ip6f_offlg & IP6F_MORE_FRAG)) { IP6_STATINC(IP6_STAT_REASSEMBLED); in6_ifstat_inc(dstifp, ifs6_reass_ok); *offp = offset; rtcache_unref(rt, &ro); return ip6f->ip6f_nxt; } mutex_enter(&frag6_lock); /* * 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) ; else if (frag6_nfrags >= (u_int)ip6_maxfrags) goto dropfrag; 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) { /* All fragments must have the same IPsec flags. */ if (q6->ip6q_ipsec != ipsecflags) { goto dropfrag; } } if (q6 == &ip6q) { /* * 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) ; else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets) goto dropfrag; frag6_nfragpackets++; q6 = kmem_intr_zalloc(sizeof(struct ip6q), KM_NOSLEEP); if (q6 == NULL) { goto dropfrag; } frag6_insque(q6, &ip6q); /* ip6q_nxt will be filled afterwards, from 1st fragment */ q6->ip6q_down = q6->ip6q_up = (struct ip6asfrag *)q6; 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_unfrglen = -1; /* The 1st fragment has not arrived. */ q6->ip6q_nfrag = 0; q6->ip6q_ipsec = ipsecflags; } /* * 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. */ if (q6->ip6q_unfrglen >= 0) { /* The 1st fragment has already arrived. */ if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) { mutex_exit(&frag6_lock); icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset - sizeof(struct ip6_frag) + offsetof(struct ip6_frag, ip6f_offlg)); goto done; } } else if (fragoff + frgpartlen > IPV6_MAXPACKET) { mutex_exit(&frag6_lock); icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset - sizeof(struct ip6_frag) + offsetof(struct ip6_frag, ip6f_offlg)); goto 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 = af6->ip6af_m; struct ip6_hdr *ip6err; int erroff = af6->ip6af_offset; /* dequeue the fragment. */ frag6_deq(af6); kmem_intr_free(af6, sizeof(struct ip6asfrag)); /* 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 = kmem_intr_zalloc(sizeof(struct ip6asfrag), KM_NOSLEEP); if (ip6af == NULL) { goto dropfrag; } 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) != 0; ip6af->ip6af_off = fragoff; ip6af->ip6af_frglen = frgpartlen; ip6af->ip6af_offset = offset; ip6af->ip6af_m = 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 the incoming fragment overlaps some existing fragments in * the reassembly queue - drop it as per RFC 5722. */ if (af6->ip6af_up != (struct ip6asfrag *)q6) { i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen - ip6af->ip6af_off; if (i > 0) { kmem_intr_free(ip6af, sizeof(struct ip6asfrag)); goto dropfrag; } } if (af6 != (struct ip6asfrag *)q6) { i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off; if (i > 0) { kmem_intr_free(ip6af, sizeof(struct ip6asfrag)); goto dropfrag; } } insert: /* * Stick new segment in its place. */ frag6_enq(ip6af, af6->ip6af_up); frag6_nfrags++; q6->ip6q_nfrag++; /* * Check for complete reassembly. */ next = 0; for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = af6->ip6af_down) { if (af6->ip6af_off != next) { mutex_exit(&frag6_lock); goto done; } next += af6->ip6af_frglen; } if (af6->ip6af_up->ip6af_mff) { mutex_exit(&frag6_lock); goto done; } /* * Reassembly is complete; concatenate fragments. */ ip6af = q6->ip6q_down; t = m = ip6af->ip6af_m; 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 = af6->ip6af_m; m_adj(t->m_next, af6->ip6af_offset); m_remove_pkthdr(t->m_next); kmem_intr_free(af6, sizeof(struct ip6asfrag)); af6 = af6dwn; } /* adjust offset to point where the original next header starts */ offset = ip6af->ip6af_offset - sizeof(struct ip6_frag); kmem_intr_free(ip6af, sizeof(struct ip6asfrag)); next += offset - sizeof(struct ip6_hdr); if ((u_int)next > IPV6_MAXPACKET) { frag6_dropfrag(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; nxt = q6->ip6q_nxt; /* * Delete frag6 header. */ if (m->m_len >= offset + sizeof(struct ip6_frag)) { memmove((char *)ip6 + sizeof(struct ip6_frag), ip6, 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_dropfrag(q6); goto dropfrag; } m_adj(t, sizeof(struct ip6_frag)); m_cat(m, t); } frag6_dropfrag(q6); { KASSERT(m->m_flags & M_PKTHDR); int plen = 0; for (t = m; t; t = t->m_next) { plen += t->m_len; } m->m_pkthdr.len = plen; /* XXX XXX: clear csum_flags? */ } /* * Restore NXT to the original. */ { const 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; } IP6_STATINC(IP6_STAT_REASSEMBLED); in6_ifstat_inc(dstifp, ifs6_reass_ok); rtcache_unref(rt, &ro); mutex_exit(&frag6_lock); /* * Tell launch routine the next header. */ *mp = m; *offp = offset; return nxt; dropfrag: mutex_exit(&frag6_lock); in6_ifstat_inc(dstifp, ifs6_reass_fail); IP6_STATINC(IP6_STAT_FRAGDROPPED); m_freem(m); done: rtcache_unref(rt, &ro); return IPPROTO_DONE; } int ip6_reass_packet(struct mbuf **mp, int offset) { if (frag6_input(mp, &offset, IPPROTO_IPV6) == IPPROTO_DONE) { *mp = NULL; return EINVAL; } return 0; } /* * Free a fragment reassembly header and all * associated datagrams. */ static void frag6_freef(struct ip6q *q6) { struct ip6asfrag *af6, *down6; KASSERT(mutex_owned(&frag6_lock)); for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6; af6 = down6) { struct mbuf *m = af6->ip6af_m; 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 *); /* restore 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); } kmem_intr_free(af6, sizeof(struct ip6asfrag)); } frag6_dropfrag(q6); } /* * Put an ip fragment on a reassembly chain. * Like insque, but pointers in middle of structure. */ void frag6_enq(struct ip6asfrag *af6, struct ip6asfrag *up6) { KASSERT(mutex_owned(&frag6_lock)); 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(struct ip6asfrag *af6) { KASSERT(mutex_owned(&frag6_lock)); af6->ip6af_up->ip6af_down = af6->ip6af_down; af6->ip6af_down->ip6af_up = af6->ip6af_up; } /* * Insert newq after oldq. */ void frag6_insque(struct ip6q *newq, struct ip6q *oldq) { KASSERT(mutex_owned(&frag6_lock)); newq->ip6q_prev = oldq; newq->ip6q_next = oldq->ip6q_next; oldq->ip6q_next->ip6q_prev = newq; oldq->ip6q_next = newq; } /* * Unlink p6. */ void frag6_remque(struct ip6q *p6) { KASSERT(mutex_owned(&frag6_lock)); p6->ip6q_prev->ip6q_next = p6->ip6q_next; p6->ip6q_next->ip6q_prev = p6->ip6q_prev; } void frag6_fasttimo(void) { SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE(); if (frag6_drainwanted) { frag6_drain(); frag6_drainwanted = 0; } SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE(); } /* * IPv6 reassembling timer processing; * if a timer expires on a reassembly * queue, discard it. */ void frag6_slowtimo(void) { struct ip6q *q6; SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE(); mutex_enter(&frag6_lock); q6 = ip6q.ip6q_next; if (q6) { while (q6 != &ip6q) { --q6->ip6q_ttl; q6 = q6->ip6q_next; if (q6->ip6q_prev->ip6q_ttl == 0) { IP6_STATINC(IP6_STAT_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 && ip6q.ip6q_prev) { IP6_STATINC(IP6_STAT_FRAGOVERFLOW); /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */ frag6_freef(ip6q.ip6q_prev); } mutex_exit(&frag6_lock); SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE(); #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. */ rtcache_free(&ip6_forward_rt); rtcache_free(&ipsrcchk_rt); #endif } void frag6_drainstub(void) { frag6_drainwanted = 1; } /* * Drain off all datagram fragments. */ void frag6_drain(void) { if (mutex_tryenter(&frag6_lock)) { while (ip6q.ip6q_next != &ip6q) { IP6_STATINC(IP6_STAT_FRAGDROPPED); /* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */ frag6_freef(ip6q.ip6q_next); } mutex_exit(&frag6_lock); } }