/* * IPv6 fragment reassembly * Linux INET6 implementation * * Authors: * Pedro Roque * * Based on: net/ipv4/ip_fragment.c * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ /* * Fixes: * Andi Kleen Make it work with multiple hosts. * More RFC compliance. * * Horst von Brand Add missing #include * Alexey Kuznetsov SMP races, threading, cleanup. * Patrick McHardy LRU queue of frag heads for evictor. * Mitsuru KANDA @USAGI Register inet6_protocol{}. * David Stevens and * YOSHIFUJI,H. @USAGI Always remove fragment header to * calculate ICV correctly. */ #define pr_fmt(fmt) "IPv6: " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static const char ip6_frag_cache_name[] = "ip6-frags"; struct ip6frag_skb_cb { struct inet6_skb_parm h; int offset; }; #define FRAG6_CB(skb) ((struct ip6frag_skb_cb *)((skb)->cb)) static u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) { return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); } static struct inet_frags ip6_frags; static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_device *dev); /* * callers should be careful not to use the hash value outside the ipfrag_lock * as doing so could race with ipfrag_hash_rnd being recalculated. */ static unsigned int inet6_hash_frag(__be32 id, const struct in6_addr *saddr, const struct in6_addr *daddr) { net_get_random_once(&ip6_frags.rnd, sizeof(ip6_frags.rnd)); return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr), (__force u32)id, ip6_frags.rnd); } static unsigned int ip6_hashfn(const struct inet_frag_queue *q) { const struct frag_queue *fq; fq = container_of(q, struct frag_queue, q); return inet6_hash_frag(fq->id, &fq->saddr, &fq->daddr); } bool ip6_frag_match(const struct inet_frag_queue *q, const void *a) { const struct frag_queue *fq; const struct ip6_create_arg *arg = a; fq = container_of(q, struct frag_queue, q); return fq->id == arg->id && fq->user == arg->user && ipv6_addr_equal(&fq->saddr, arg->src) && ipv6_addr_equal(&fq->daddr, arg->dst); } EXPORT_SYMBOL(ip6_frag_match); void ip6_frag_init(struct inet_frag_queue *q, const void *a) { struct frag_queue *fq = container_of(q, struct frag_queue, q); const struct ip6_create_arg *arg = a; fq->id = arg->id; fq->user = arg->user; fq->saddr = *arg->src; fq->daddr = *arg->dst; fq->ecn = arg->ecn; } EXPORT_SYMBOL(ip6_frag_init); void ip6_expire_frag_queue(struct net *net, struct frag_queue *fq, struct inet_frags *frags) { struct net_device *dev = NULL; spin_lock(&fq->q.lock); if (fq->q.flags & INET_FRAG_COMPLETE) goto out; inet_frag_kill(&fq->q, frags); rcu_read_lock(); dev = dev_get_by_index_rcu(net, fq->iif); if (!dev) goto out_rcu_unlock; IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS); if (fq->q.flags & INET_FRAG_EVICTED) goto out_rcu_unlock; IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMTIMEOUT); /* Don't send error if the first segment did not arrive. */ if (!(fq->q.flags & INET_FRAG_FIRST_IN) || !fq->q.fragments) goto out_rcu_unlock; /* But use as source device on which LAST ARRIVED * segment was received. And do not use fq->dev * pointer directly, device might already disappeared. */ fq->q.fragments->dev = dev; icmpv6_send(fq->q.fragments, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0); out_rcu_unlock: rcu_read_unlock(); out: spin_unlock(&fq->q.lock); inet_frag_put(&fq->q, frags); } EXPORT_SYMBOL(ip6_expire_frag_queue); static void ip6_frag_expire(unsigned long data) { struct frag_queue *fq; struct net *net; fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q); net = container_of(fq->q.net, struct net, ipv6.frags); ip6_expire_frag_queue(net, fq, &ip6_frags); } static struct frag_queue * fq_find(struct net *net, __be32 id, const struct in6_addr *src, const struct in6_addr *dst, u8 ecn) { struct inet_frag_queue *q; struct ip6_create_arg arg; unsigned int hash; arg.id = id; arg.user = IP6_DEFRAG_LOCAL_DELIVER; arg.src = src; arg.dst = dst; arg.ecn = ecn; hash = inet6_hash_frag(id, src, dst); q = inet_frag_find(&net->ipv6.frags, &ip6_frags, &arg, hash); if (IS_ERR_OR_NULL(q)) { inet_frag_maybe_warn_overflow(q, pr_fmt()); return NULL; } return container_of(q, struct frag_queue, q); } static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, struct frag_hdr *fhdr, int nhoff) { struct sk_buff *prev, *next; struct net_device *dev; int offset, end; struct net *net = dev_net(skb_dst(skb)->dev); u8 ecn; if (fq->q.flags & INET_FRAG_COMPLETE) goto err; offset = ntohs(fhdr->frag_off) & ~0x7; end = offset + (ntohs(ipv6_hdr(skb)->payload_len) - ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1))); if ((unsigned int)end > IPV6_MAXPLEN) { IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INHDRERRORS); icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, ((u8 *)&fhdr->frag_off - skb_network_header(skb))); return -1; } ecn = ip6_frag_ecn(ipv6_hdr(skb)); if (skb->ip_summed == CHECKSUM_COMPLETE) { const unsigned char *nh = skb_network_header(skb); skb->csum = csum_sub(skb->csum, csum_partial(nh, (u8 *)(fhdr + 1) - nh, 0)); } /* Is this the final fragment? */ if (!(fhdr->frag_off & htons(IP6_MF))) { /* If we already have some bits beyond end * or have different end, the segment is corrupted. */ if (end < fq->q.len || ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) goto err; fq->q.flags |= INET_FRAG_LAST_IN; fq->q.len = end; } else { /* Check if the fragment is rounded to 8 bytes. * Required by the RFC. */ if (end & 0x7) { /* RFC2460 says always send parameter problem in * this case. -DaveM */ IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INHDRERRORS); icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, offsetof(struct ipv6hdr, payload_len)); return -1; } if (end > fq->q.len) { /* Some bits beyond end -> corruption. */ if (fq->q.flags & INET_FRAG_LAST_IN) goto err; fq->q.len = end; } } if (end == offset) goto err; /* Point into the IP datagram 'data' part. */ if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) goto err; if (pskb_trim_rcsum(skb, end - offset)) goto err; /* Find out which fragments are in front and at the back of us * in the chain of fragments so far. We must know where to put * this fragment, right? */ prev = fq->q.fragments_tail; if (!prev || FRAG6_CB(prev)->offset < offset) { next = NULL; goto found; } prev = NULL; for (next = fq->q.fragments; next != NULL; next = next->next) { if (FRAG6_CB(next)->offset >= offset) break; /* bingo! */ prev = next; } found: /* RFC5722, Section 4, amended by Errata ID : 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. */ /* Check for overlap with preceding fragment. */ if (prev && (FRAG6_CB(prev)->offset + prev->len) > offset) goto discard_fq; /* Look for overlap with succeeding segment. */ if (next && FRAG6_CB(next)->offset < end) goto discard_fq; FRAG6_CB(skb)->offset = offset; /* Insert this fragment in the chain of fragments. */ skb->next = next; if (!next) fq->q.fragments_tail = skb; if (prev) prev->next = skb; else fq->q.fragments = skb; dev = skb->dev; if (dev) { fq->iif = dev->ifindex; skb->dev = NULL; } fq->q.stamp = skb->tstamp; fq->q.meat += skb->len; fq->ecn |= ecn; add_frag_mem_limit(fq->q.net, skb->truesize); /* The first fragment. * nhoffset is obtained from the first fragment, of course. */ if (offset == 0) { fq->nhoffset = nhoff; fq->q.flags |= INET_FRAG_FIRST_IN; } if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && fq->q.meat == fq->q.len) { int res; unsigned long orefdst = skb->_skb_refdst; skb->_skb_refdst = 0UL; res = ip6_frag_reasm(fq, prev, dev); skb->_skb_refdst = orefdst; return res; } skb_dst_drop(skb); return -1; discard_fq: inet_frag_kill(&fq->q, &ip6_frags); err: IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS); kfree_skb(skb); return -1; } /* * Check if this packet is complete. * Returns NULL on failure by any reason, and pointer * to current nexthdr field in reassembled frame. * * It is called with locked fq, and caller must check that * queue is eligible for reassembly i.e. it is not COMPLETE, * the last and the first frames arrived and all the bits are here. */ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_device *dev) { struct net *net = container_of(fq->q.net, struct net, ipv6.frags); struct sk_buff *fp, *head = fq->q.fragments; int payload_len; unsigned int nhoff; int sum_truesize; u8 ecn; inet_frag_kill(&fq->q, &ip6_frags); ecn = ip_frag_ecn_table[fq->ecn]; if (unlikely(ecn == 0xff)) goto out_fail; /* Make the one we just received the head. */ if (prev) { head = prev->next; fp = skb_clone(head, GFP_ATOMIC); if (!fp) goto out_oom; fp->next = head->next; if (!fp->next) fq->q.fragments_tail = fp; prev->next = fp; skb_morph(head, fq->q.fragments); head->next = fq->q.fragments->next; consume_skb(fq->q.fragments); fq->q.fragments = head; } WARN_ON(head == NULL); WARN_ON(FRAG6_CB(head)->offset != 0); /* Unfragmented part is taken from the first segment. */ payload_len = ((head->data - skb_network_header(head)) - sizeof(struct ipv6hdr) + fq->q.len - sizeof(struct frag_hdr)); if (payload_len > IPV6_MAXPLEN) goto out_oversize; /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) goto out_oom; /* If the first fragment is fragmented itself, we split * it to two chunks: the first with data and paged part * and the second, holding only fragments. */ if (skb_has_frag_list(head)) { struct sk_buff *clone; int i, plen = 0; clone = alloc_skb(0, GFP_ATOMIC); if (!clone) goto out_oom; clone->next = head->next; head->next = clone; skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; skb_frag_list_init(head); for (i = 0; i < skb_shinfo(head)->nr_frags; i++) plen += skb_frag_size(&skb_shinfo(head)->frags[i]); clone->len = clone->data_len = head->data_len - plen; head->data_len -= clone->len; head->len -= clone->len; clone->csum = 0; clone->ip_summed = head->ip_summed; add_frag_mem_limit(fq->q.net, clone->truesize); } /* We have to remove fragment header from datagram and to relocate * header in order to calculate ICV correctly. */ nhoff = fq->nhoffset; skb_network_header(head)[nhoff] = skb_transport_header(head)[0]; memmove(head->head + sizeof(struct frag_hdr), head->head, (head->data - head->head) - sizeof(struct frag_hdr)); head->mac_header += sizeof(struct frag_hdr); head->network_header += sizeof(struct frag_hdr); skb_reset_transport_header(head); skb_push(head, head->data - skb_network_header(head)); sum_truesize = head->truesize; for (fp = head->next; fp;) { bool headstolen; int delta; struct sk_buff *next = fp->next; sum_truesize += fp->truesize; if (head->ip_summed != fp->ip_summed) head->ip_summed = CHECKSUM_NONE; else if (head->ip_summed == CHECKSUM_COMPLETE) head->csum = csum_add(head->csum, fp->csum); if (skb_try_coalesce(head, fp, &headstolen, &delta)) { kfree_skb_partial(fp, headstolen); } else { if (!skb_shinfo(head)->frag_list) skb_shinfo(head)->frag_list = fp; head->data_len += fp->len; head->len += fp->len; head->truesize += fp->truesize; } fp = next; } sub_frag_mem_limit(fq->q.net, sum_truesize); head->next = NULL; head->dev = dev; head->tstamp = fq->q.stamp; ipv6_hdr(head)->payload_len = htons(payload_len); ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn); IP6CB(head)->nhoff = nhoff; IP6CB(head)->flags |= IP6SKB_FRAGMENTED; /* Yes, and fold redundant checksum back. 8) */ if (head->ip_summed == CHECKSUM_COMPLETE) head->csum = csum_partial(skb_network_header(head), skb_network_header_len(head), head->csum); rcu_read_lock(); IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS); rcu_read_unlock(); fq->q.fragments = NULL; fq->q.fragments_tail = NULL; return 1; out_oversize: net_dbg_ratelimited("ip6_frag_reasm: payload len = %d\n", payload_len); goto out_fail; out_oom: net_dbg_ratelimited("ip6_frag_reasm: no memory for reassembly\n"); out_fail: rcu_read_lock(); IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMFAILS); rcu_read_unlock(); return -1; } static int ipv6_frag_rcv(struct sk_buff *skb) { struct frag_hdr *fhdr; struct frag_queue *fq; const struct ipv6hdr *hdr = ipv6_hdr(skb); struct net *net = dev_net(skb_dst(skb)->dev); if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED) goto fail_hdr; IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS); /* Jumbo payload inhibits frag. header */ if (hdr->payload_len == 0) goto fail_hdr; if (!pskb_may_pull(skb, (skb_transport_offset(skb) + sizeof(struct frag_hdr)))) goto fail_hdr; hdr = ipv6_hdr(skb); fhdr = (struct frag_hdr *)skb_transport_header(skb); if (!(fhdr->frag_off & htons(0xFFF9))) { /* It is not a fragmented frame */ skb->transport_header += sizeof(struct frag_hdr); IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS); IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb); IP6CB(skb)->flags |= IP6SKB_FRAGMENTED; return 1; } fq = fq_find(net, fhdr->identification, &hdr->saddr, &hdr->daddr, ip6_frag_ecn(hdr)); if (fq) { int ret; spin_lock(&fq->q.lock); ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff); spin_unlock(&fq->q.lock); inet_frag_put(&fq->q, &ip6_frags); return ret; } IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMFAILS); kfree_skb(skb); return -1; fail_hdr: IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_INHDRERRORS); icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb_network_header_len(skb)); return -1; } static const struct inet6_protocol frag_protocol = { .handler = ipv6_frag_rcv, .flags = INET6_PROTO_NOPOLICY, }; #ifdef CONFIG_SYSCTL static int zero; static struct ctl_table ip6_frags_ns_ctl_table[] = { { .procname = "ip6frag_high_thresh", .data = &init_net.ipv6.frags.high_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &init_net.ipv6.frags.low_thresh }, { .procname = "ip6frag_low_thresh", .data = &init_net.ipv6.frags.low_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &zero, .extra2 = &init_net.ipv6.frags.high_thresh }, { .procname = "ip6frag_time", .data = &init_net.ipv6.frags.timeout, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { } }; /* secret interval has been deprecated */ static int ip6_frags_secret_interval_unused; static struct ctl_table ip6_frags_ctl_table[] = { { .procname = "ip6frag_secret_interval", .data = &ip6_frags_secret_interval_unused, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { } }; static int __net_init ip6_frags_ns_sysctl_register(struct net *net) { struct ctl_table *table; struct ctl_table_header *hdr; table = ip6_frags_ns_ctl_table; if (!net_eq(net, &init_net)) { table = kmemdup(table, sizeof(ip6_frags_ns_ctl_table), GFP_KERNEL); if (!table) goto err_alloc; table[0].data = &net->ipv6.frags.high_thresh; table[0].extra1 = &net->ipv6.frags.low_thresh; table[0].extra2 = &init_net.ipv6.frags.high_thresh; table[1].data = &net->ipv6.frags.low_thresh; table[1].extra2 = &net->ipv6.frags.high_thresh; table[2].data = &net->ipv6.frags.timeout; /* Don't export sysctls to unprivileged users */ if (net->user_ns != &init_user_ns) table[0].procname = NULL; } hdr = register_net_sysctl(net, "net/ipv6", table); if (!hdr) goto err_reg; net->ipv6.sysctl.frags_hdr = hdr; return 0; err_reg: if (!net_eq(net, &init_net)) kfree(table); err_alloc: return -ENOMEM; } static void __net_exit ip6_frags_ns_sysctl_unregister(struct net *net) { struct ctl_table *table; table = net->ipv6.sysctl.frags_hdr->ctl_table_arg; unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr); if (!net_eq(net, &init_net)) kfree(table); } static struct ctl_table_header *ip6_ctl_header; static int ip6_frags_sysctl_register(void) { ip6_ctl_header = register_net_sysctl(&init_net, "net/ipv6", ip6_frags_ctl_table); return ip6_ctl_header == NULL ? -ENOMEM : 0; } static void ip6_frags_sysctl_unregister(void) { unregister_net_sysctl_table(ip6_ctl_header); } #else static int ip6_frags_ns_sysctl_register(struct net *net) { return 0; } static void ip6_frags_ns_sysctl_unregister(struct net *net) { } static int ip6_frags_sysctl_register(void) { return 0; } static void ip6_frags_sysctl_unregister(void) { } #endif static int __net_init ipv6_frags_init_net(struct net *net) { net->ipv6.frags.high_thresh = IPV6_FRAG_HIGH_THRESH; net->ipv6.frags.low_thresh = IPV6_FRAG_LOW_THRESH; net->ipv6.frags.timeout = IPV6_FRAG_TIMEOUT; inet_frags_init_net(&net->ipv6.frags); return ip6_frags_ns_sysctl_register(net); } static void __net_exit ipv6_frags_exit_net(struct net *net) { ip6_frags_ns_sysctl_unregister(net); inet_frags_exit_net(&net->ipv6.frags, &ip6_frags); } static struct pernet_operations ip6_frags_ops = { .init = ipv6_frags_init_net, .exit = ipv6_frags_exit_net, }; int __init ipv6_frag_init(void) { int ret; ret = inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT); if (ret) goto out; ret = ip6_frags_sysctl_register(); if (ret) goto err_sysctl; ret = register_pernet_subsys(&ip6_frags_ops); if (ret) goto err_pernet; ip6_frags.hashfn = ip6_hashfn; ip6_frags.constructor = ip6_frag_init; ip6_frags.destructor = NULL; ip6_frags.skb_free = NULL; ip6_frags.qsize = sizeof(struct frag_queue); ip6_frags.match = ip6_frag_match; ip6_frags.frag_expire = ip6_frag_expire; ip6_frags.frags_cache_name = ip6_frag_cache_name; ret = inet_frags_init(&ip6_frags); if (ret) goto err_pernet; out: return ret; err_pernet: ip6_frags_sysctl_unregister(); err_sysctl: inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT); goto out; } void ipv6_frag_exit(void) { inet_frags_fini(&ip6_frags); ip6_frags_sysctl_unregister(); unregister_pernet_subsys(&ip6_frags_ops); inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT); }