/* * IPv6 fragment reassembly for connection tracking * * Copyright (C)2004 USAGI/WIDE Project * * Author: * Yasuyuki Kozakai @USAGI * * Based on: net/ipv6/reassembly.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. */ #define pr_fmt(fmt) "IPv6-nf: " 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 #include #include #include static const char nf_frags_cache_name[] = "nf-frags"; struct nf_ct_frag6_skb_cb { struct inet6_skb_parm h; int offset; struct sk_buff *orig; }; #define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb*)((skb)->cb)) static struct inet_frags nf_frags; #ifdef CONFIG_SYSCTL static int zero; static struct ctl_table nf_ct_frag6_sysctl_table[] = { { .procname = "nf_conntrack_frag6_timeout", .data = &init_net.nf_frag.frags.timeout, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { .procname = "nf_conntrack_frag6_low_thresh", .data = &init_net.nf_frag.frags.low_thresh, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &zero, .extra2 = &init_net.nf_frag.frags.high_thresh }, { .procname = "nf_conntrack_frag6_high_thresh", .data = &init_net.nf_frag.frags.high_thresh, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &init_net.nf_frag.frags.low_thresh }, { } }; static int nf_ct_frag6_sysctl_register(struct net *net) { struct ctl_table *table; struct ctl_table_header *hdr; table = nf_ct_frag6_sysctl_table; if (!net_eq(net, &init_net)) { table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table), GFP_KERNEL); if (table == NULL) goto err_alloc; table[0].data = &net->nf_frag.frags.timeout; table[1].data = &net->nf_frag.frags.low_thresh; table[1].extra2 = &net->nf_frag.frags.high_thresh; table[2].data = &net->nf_frag.frags.high_thresh; table[2].extra1 = &net->nf_frag.frags.low_thresh; table[2].extra2 = &init_net.nf_frag.frags.high_thresh; } hdr = register_net_sysctl(net, "net/netfilter", table); if (hdr == NULL) goto err_reg; net->nf_frag.sysctl.frags_hdr = hdr; return 0; err_reg: if (!net_eq(net, &init_net)) kfree(table); err_alloc: return -ENOMEM; } static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) { struct ctl_table *table; table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg; unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr); if (!net_eq(net, &init_net)) kfree(table); } #else static int nf_ct_frag6_sysctl_register(struct net *net) { return 0; } static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net) { } #endif static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h) { return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK); } static unsigned int nf_hash_frag(__be32 id, const struct in6_addr *saddr, const struct in6_addr *daddr) { net_get_random_once(&nf_frags.rnd, sizeof(nf_frags.rnd)); return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr), (__force u32)id, nf_frags.rnd); } static unsigned int nf_hashfn(const struct inet_frag_queue *q) { const struct frag_queue *nq; nq = container_of(q, struct frag_queue, q); return nf_hash_frag(nq->id, &nq->saddr, &nq->daddr); } static void nf_skb_free(struct sk_buff *skb) { if (NFCT_FRAG6_CB(skb)->orig) kfree_skb(NFCT_FRAG6_CB(skb)->orig); } static void nf_ct_frag6_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, nf_frag.frags); ip6_expire_frag_queue(net, fq, &nf_frags); } /* Creation primitives. */ static inline struct frag_queue *fq_find(struct net *net, __be32 id, u32 user, struct in6_addr *src, struct in6_addr *dst, int iif, u8 ecn) { struct inet_frag_queue *q; struct ip6_create_arg arg; unsigned int hash; arg.id = id; arg.user = user; arg.src = src; arg.dst = dst; arg.iif = iif; arg.ecn = ecn; local_bh_disable(); hash = nf_hash_frag(id, src, dst); q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash); local_bh_enable(); 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 nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb, const struct frag_hdr *fhdr, int nhoff) { struct sk_buff *prev, *next; unsigned int payload_len; int offset, end; u8 ecn; if (fq->q.flags & INET_FRAG_COMPLETE) { pr_debug("Already completed\n"); goto err; } payload_len = ntohs(ipv6_hdr(skb)->payload_len); offset = ntohs(fhdr->frag_off) & ~0x7; end = offset + (payload_len - ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1))); if ((unsigned int)end > IPV6_MAXPLEN) { pr_debug("offset is too large.\n"); 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)) { pr_debug("already received last fragment\n"); 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 */ pr_debug("end of fragment not rounded to 8 bytes.\n"); return -1; } if (end > fq->q.len) { /* Some bits beyond end -> corruption. */ if (fq->q.flags & INET_FRAG_LAST_IN) { pr_debug("last packet already reached.\n"); 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)) { pr_debug("queue: message is too short.\n"); goto err; } if (pskb_trim_rcsum(skb, end - offset)) { pr_debug("Can't trim\n"); 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 || NFCT_FRAG6_CB(prev)->offset < offset) { next = NULL; goto found; } prev = NULL; for (next = fq->q.fragments; next != NULL; next = next->next) { if (NFCT_FRAG6_CB(next)->offset >= offset) break; /* bingo! */ prev = next; } found: /* RFC5722, Section 4: * 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, including those not yet received) MUST be silently * discarded. */ /* Check for overlap with preceding fragment. */ if (prev && (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset) goto discard_fq; /* Look for overlap with succeeding segment. */ if (next && NFCT_FRAG6_CB(next)->offset < end) goto discard_fq; NFCT_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; if (skb->dev) { fq->iif = skb->dev->ifindex; skb->dev = NULL; } fq->q.stamp = skb->tstamp; fq->q.meat += skb->len; fq->ecn |= ecn; if (payload_len > fq->q.max_size) fq->q.max_size = payload_len; add_frag_mem_limit(&fq->q, 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; } return 0; discard_fq: inet_frag_kill(&fq->q, &nf_frags); err: 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 struct sk_buff * nf_ct_frag6_reasm(struct frag_queue *fq, struct net_device *dev) { struct sk_buff *fp, *op, *head = fq->q.fragments; int payload_len; u8 ecn; inet_frag_kill(&fq->q, &nf_frags); WARN_ON(head == NULL); WARN_ON(NFCT_FRAG6_CB(head)->offset != 0); ecn = ip_frag_ecn_table[fq->ecn]; if (unlikely(ecn == 0xff)) goto out_fail; /* 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) { pr_debug("payload len is too large.\n"); goto out_oversize; } /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) { pr_debug("skb is cloned but can't expand head"); 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 == NULL) 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; NFCT_FRAG6_CB(clone)->orig = NULL; add_frag_mem_limit(&fq->q, clone->truesize); } /* We have to remove fragment header from datagram and to relocate * header in order to calculate ICV correctly. */ skb_network_header(head)[fq->nhoffset] = 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_shinfo(head)->frag_list = head->next; skb_reset_transport_header(head); skb_push(head, head->data - skb_network_header(head)); for (fp=head->next; fp; fp = fp->next) { head->data_len += fp->len; head->len += fp->len; 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); head->truesize += fp->truesize; } sub_frag_mem_limit(&fq->q, head->truesize); head->ignore_df = 1; 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)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size; /* 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); fq->q.fragments = NULL; fq->q.fragments_tail = NULL; /* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */ fp = skb_shinfo(head)->frag_list; if (fp && NFCT_FRAG6_CB(fp)->orig == NULL) /* at above code, head skb is divided into two skbs. */ fp = fp->next; op = NFCT_FRAG6_CB(head)->orig; for (; fp; fp = fp->next) { struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig; op->next = orig; op = orig; NFCT_FRAG6_CB(fp)->orig = NULL; } return head; out_oversize: net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n", payload_len); goto out_fail; out_oom: net_dbg_ratelimited("nf_ct_frag6_reasm: no memory for reassembly\n"); out_fail: return NULL; } /* * find the header just before Fragment Header. * * if success return 0 and set ... * (*prevhdrp): the value of "Next Header Field" in the header * just before Fragment Header. * (*prevhoff): the offset of "Next Header Field" in the header * just before Fragment Header. * (*fhoff) : the offset of Fragment Header. * * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c * */ static int find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff) { u8 nexthdr = ipv6_hdr(skb)->nexthdr; const int netoff = skb_network_offset(skb); u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr); int start = netoff + sizeof(struct ipv6hdr); int len = skb->len - start; u8 prevhdr = NEXTHDR_IPV6; while (nexthdr != NEXTHDR_FRAGMENT) { struct ipv6_opt_hdr hdr; int hdrlen; if (!ipv6_ext_hdr(nexthdr)) { return -1; } if (nexthdr == NEXTHDR_NONE) { pr_debug("next header is none\n"); return -1; } if (len < (int)sizeof(struct ipv6_opt_hdr)) { pr_debug("too short\n"); return -1; } if (skb_copy_bits(skb, start, &hdr, sizeof(hdr))) BUG(); if (nexthdr == NEXTHDR_AUTH) hdrlen = (hdr.hdrlen+2)<<2; else hdrlen = ipv6_optlen(&hdr); prevhdr = nexthdr; prev_nhoff = start; nexthdr = hdr.nexthdr; len -= hdrlen; start += hdrlen; } if (len < 0) return -1; *prevhdrp = prevhdr; *prevhoff = prev_nhoff; *fhoff = start; return 0; } struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user) { struct sk_buff *clone; struct net_device *dev = skb->dev; struct net *net = skb_dst(skb) ? dev_net(skb_dst(skb)->dev) : dev_net(skb->dev); struct frag_hdr *fhdr; struct frag_queue *fq; struct ipv6hdr *hdr; int fhoff, nhoff; u8 prevhdr; struct sk_buff *ret_skb = NULL; /* Jumbo payload inhibits frag. header */ if (ipv6_hdr(skb)->payload_len == 0) { pr_debug("payload len = 0\n"); return skb; } if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0) return skb; clone = skb_clone(skb, GFP_ATOMIC); if (clone == NULL) { pr_debug("Can't clone skb\n"); return skb; } NFCT_FRAG6_CB(clone)->orig = skb; if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) { pr_debug("message is too short.\n"); goto ret_orig; } skb_set_transport_header(clone, fhoff); hdr = ipv6_hdr(clone); fhdr = (struct frag_hdr *)skb_transport_header(clone); fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr, skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr)); if (fq == NULL) { pr_debug("Can't find and can't create new queue\n"); goto ret_orig; } spin_lock_bh(&fq->q.lock); if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) { spin_unlock_bh(&fq->q.lock); pr_debug("Can't insert skb to queue\n"); inet_frag_put(&fq->q, &nf_frags); goto ret_orig; } if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && fq->q.meat == fq->q.len) { ret_skb = nf_ct_frag6_reasm(fq, dev); if (ret_skb == NULL) pr_debug("Can't reassemble fragmented packets\n"); } spin_unlock_bh(&fq->q.lock); inet_frag_put(&fq->q, &nf_frags); return ret_skb; ret_orig: kfree_skb(clone); return skb; } #if defined(CONFIG_BCM_KF_MAP) && (defined(CONFIG_BCM_MAP) || defined(CONFIG_BCM_MAP_MODULE)) EXPORT_SYMBOL_GPL(nf_ct_frag6_gather); #endif void nf_ct_frag6_consume_orig(struct sk_buff *skb) { struct sk_buff *s, *s2; for (s = NFCT_FRAG6_CB(skb)->orig; s;) { s2 = s->next; s->next = NULL; consume_skb(s); s = s2; } } #if defined(CONFIG_BCM_KF_MAP) && (defined(CONFIG_BCM_MAP) || defined(CONFIG_BCM_MAP_MODULE)) EXPORT_SYMBOL_GPL(nf_ct_frag6_consume_orig); #endif static int nf_ct_net_init(struct net *net) { net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH; net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH; net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT; inet_frags_init_net(&net->nf_frag.frags); return nf_ct_frag6_sysctl_register(net); } static void nf_ct_net_exit(struct net *net) { nf_ct_frags6_sysctl_unregister(net); inet_frags_exit_net(&net->nf_frag.frags, &nf_frags); } static struct pernet_operations nf_ct_net_ops = { .init = nf_ct_net_init, .exit = nf_ct_net_exit, }; int nf_ct_frag6_init(void) { int ret = 0; nf_frags.hashfn = nf_hashfn; nf_frags.constructor = ip6_frag_init; nf_frags.destructor = NULL; nf_frags.skb_free = nf_skb_free; nf_frags.qsize = sizeof(struct frag_queue); nf_frags.match = ip6_frag_match; nf_frags.frag_expire = nf_ct_frag6_expire; nf_frags.frags_cache_name = nf_frags_cache_name; ret = inet_frags_init(&nf_frags); if (ret) goto out; ret = register_pernet_subsys(&nf_ct_net_ops); if (ret) inet_frags_fini(&nf_frags); out: return ret; } void nf_ct_frag6_cleanup(void) { unregister_pernet_subsys(&nf_ct_net_ops); inet_frags_fini(&nf_frags); }