// SPDX-License-Identifier: GPL-2.0 /* * INET An implementation of the TCP/IP protocol suite for the LINUX * operating system. INET is implemented using the BSD Socket * interface as the means of communication with the user level. * * The IP fragmentation functionality. * * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG> * Alan Cox <alan@lxorguk.ukuu.org.uk> * * Fixes: * Alan Cox : Split from ip.c , see ip_input.c for history. * David S. Miller : Begin massive cleanup... * Andi Kleen : Add sysctls. * xxxx : Overlapfrag bug. * Ultima : ip_expire() kernel panic. * Bill Hawes : Frag accounting and evictor fixes. * John McDonald : 0 length frag bug. * Alexey Kuznetsov: SMP races, threading, cleanup. * Patrick McHardy : LRU queue of frag heads for evictor. */ #define pr_fmt(fmt) "IPv4: " fmt #include <linux/compiler.h> #include <linux/module.h> #include <linux/types.h> #include <linux/mm.h> #include <linux/jiffies.h> #include <linux/skbuff.h> #include <linux/list.h> #include <linux/ip.h> #include <linux/icmp.h> #include <linux/netdevice.h> #include <linux/jhash.h> #include <linux/random.h> #include <linux/slab.h> #include <net/route.h> #include <net/dst.h> #include <net/sock.h> #include <net/ip.h> #include <net/icmp.h> #include <net/checksum.h> #include <net/inetpeer.h> #include <net/inet_frag.h> #include <linux/tcp.h> #include <linux/udp.h> #include <linux/inet.h> #include <linux/netfilter_ipv4.h> #include <net/inet_ecn.h> #include <net/l3mdev.h> /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c * as well. Or notify me, at least. --ANK */ static const char ip_frag_cache_name[] = "ip4-frags"; /* Describe an entry in the "incomplete datagrams" queue. */ struct ipq { struct inet_frag_queue q; u8 ecn; /* RFC3168 support */ u16 max_df_size; /* largest frag with DF set seen */ int iif; unsigned int rid; struct inet_peer *peer; }; static u8 ip4_frag_ecn(u8 tos) { return 1 << (tos & INET_ECN_MASK); } static struct inet_frags ip4_frags; static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, struct net_device *dev); static void ip4_frag_init(struct inet_frag_queue *q, const void *a) { struct ipq *qp = container_of(q, struct ipq, q); struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4, frags); struct net *net = container_of(ipv4, struct net, ipv4); const struct frag_v4_compare_key *key = a; q->key.v4 = *key; qp->ecn = 0; qp->peer = q->net->max_dist ? inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) : NULL; } static void ip4_frag_free(struct inet_frag_queue *q) { struct ipq *qp; qp = container_of(q, struct ipq, q); if (qp->peer) inet_putpeer(qp->peer); } /* Destruction primitives. */ static void ipq_put(struct ipq *ipq) { inet_frag_put(&ipq->q); } /* Kill ipq entry. It is not destroyed immediately, * because caller (and someone more) holds reference count. */ static void ipq_kill(struct ipq *ipq) { inet_frag_kill(&ipq->q); } static bool frag_expire_skip_icmp(u32 user) { return user == IP_DEFRAG_AF_PACKET || ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN, __IP_DEFRAG_CONNTRACK_IN_END) || ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN, __IP_DEFRAG_CONNTRACK_BRIDGE_IN); } /* * Oops, a fragment queue timed out. Kill it and send an ICMP reply. */ static void ip_expire(struct timer_list *t) { struct inet_frag_queue *frag = from_timer(frag, t, timer); const struct iphdr *iph; struct sk_buff *head; struct net *net; struct ipq *qp; int err; qp = container_of(frag, struct ipq, q); net = container_of(qp->q.net, struct net, ipv4.frags); rcu_read_lock(); spin_lock(&qp->q.lock); if (qp->q.flags & INET_FRAG_COMPLETE) goto out; ipq_kill(qp); __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); head = qp->q.fragments; __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT); if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !head) goto out; head->dev = dev_get_by_index_rcu(net, qp->iif); if (!head->dev) goto out; /* skb has no dst, perform route lookup again */ iph = ip_hdr(head); err = ip_route_input_noref(head, iph->daddr, iph->saddr, iph->tos, head->dev); if (err) goto out; /* Only an end host needs to send an ICMP * "Fragment Reassembly Timeout" message, per RFC792. */ if (frag_expire_skip_icmp(qp->q.key.v4.user) && (skb_rtable(head)->rt_type != RTN_LOCAL)) goto out; skb_get(head); spin_unlock(&qp->q.lock); icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); kfree_skb(head); goto out_rcu_unlock; out: spin_unlock(&qp->q.lock); out_rcu_unlock: rcu_read_unlock(); ipq_put(qp); } /* Find the correct entry in the "incomplete datagrams" queue for * this IP datagram, and create new one, if nothing is found. */ static struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user, int vif) { struct frag_v4_compare_key key = { .saddr = iph->saddr, .daddr = iph->daddr, .user = user, .vif = vif, .id = iph->id, .protocol = iph->protocol, }; struct inet_frag_queue *q; q = inet_frag_find(&net->ipv4.frags, &key); if (!q) return NULL; return container_of(q, struct ipq, q); } /* Is the fragment too far ahead to be part of ipq? */ static int ip_frag_too_far(struct ipq *qp) { struct inet_peer *peer = qp->peer; unsigned int max = qp->q.net->max_dist; unsigned int start, end; int rc; if (!peer || !max) return 0; start = qp->rid; end = atomic_inc_return(&peer->rid); qp->rid = end; rc = qp->q.fragments && (end - start) > max; if (rc) { struct net *net; net = container_of(qp->q.net, struct net, ipv4.frags); __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); } return rc; } static int ip_frag_reinit(struct ipq *qp) { struct sk_buff *fp; unsigned int sum_truesize = 0; if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) { refcount_inc(&qp->q.refcnt); return -ETIMEDOUT; } fp = qp->q.fragments; do { struct sk_buff *xp = fp->next; sum_truesize += fp->truesize; kfree_skb(fp); fp = xp; } while (fp); sub_frag_mem_limit(qp->q.net, sum_truesize); qp->q.flags = 0; qp->q.len = 0; qp->q.meat = 0; qp->q.fragments = NULL; qp->q.fragments_tail = NULL; qp->iif = 0; qp->ecn = 0; return 0; } /* Add new segment to existing queue. */ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) { struct sk_buff *prev, *next; struct net_device *dev; unsigned int fragsize; int flags, offset; int ihl, end; int err = -ENOENT; u8 ecn; if (qp->q.flags & INET_FRAG_COMPLETE) goto err; if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) && unlikely(ip_frag_too_far(qp)) && unlikely(err = ip_frag_reinit(qp))) { ipq_kill(qp); goto err; } ecn = ip4_frag_ecn(ip_hdr(skb)->tos); offset = ntohs(ip_hdr(skb)->frag_off); flags = offset & ~IP_OFFSET; offset &= IP_OFFSET; offset <<= 3; /* offset is in 8-byte chunks */ ihl = ip_hdrlen(skb); /* Determine the position of this fragment. */ end = offset + skb->len - skb_network_offset(skb) - ihl; err = -EINVAL; /* Is this the final fragment? */ if ((flags & IP_MF) == 0) { /* If we already have some bits beyond end * or have different end, the segment is corrupted. */ if (end < qp->q.len || ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len)) goto err; qp->q.flags |= INET_FRAG_LAST_IN; qp->q.len = end; } else { if (end&7) { end &= ~7; if (skb->ip_summed != CHECKSUM_UNNECESSARY) skb->ip_summed = CHECKSUM_NONE; } if (end > qp->q.len) { /* Some bits beyond end -> corruption. */ if (qp->q.flags & INET_FRAG_LAST_IN) goto err; qp->q.len = end; } } if (end == offset) goto err; err = -ENOMEM; if (!pskb_pull(skb, skb_network_offset(skb) + ihl)) goto err; err = pskb_trim_rcsum(skb, end - offset); if (err) 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 = qp->q.fragments_tail; if (!prev || prev->ip_defrag_offset < offset) { next = NULL; goto found; } prev = NULL; for (next = qp->q.fragments; next != NULL; next = next->next) { if (next->ip_defrag_offset >= offset) break; /* bingo! */ prev = next; } found: /* We found where to put this one. Check for overlap with * preceding fragment, and, if needed, align things so that * any overlaps are eliminated. */ if (prev) { int i = (prev->ip_defrag_offset + prev->len) - offset; if (i > 0) { offset += i; err = -EINVAL; if (end <= offset) goto err; err = -ENOMEM; if (!pskb_pull(skb, i)) goto err; if (skb->ip_summed != CHECKSUM_UNNECESSARY) skb->ip_summed = CHECKSUM_NONE; } } err = -ENOMEM; while (next && next->ip_defrag_offset < end) { int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */ if (i < next->len) { /* Eat head of the next overlapped fragment * and leave the loop. The next ones cannot overlap. */ if (!pskb_pull(next, i)) goto err; next->ip_defrag_offset += i; qp->q.meat -= i; if (next->ip_summed != CHECKSUM_UNNECESSARY) next->ip_summed = CHECKSUM_NONE; break; } else { struct sk_buff *free_it = next; /* Old fragment is completely overridden with * new one drop it. */ next = next->next; if (prev) prev->next = next; else qp->q.fragments = next; qp->q.meat -= free_it->len; sub_frag_mem_limit(qp->q.net, free_it->truesize); kfree_skb(free_it); } } /* Note : skb->ip_defrag_offset and skb->dev share the same location */ dev = skb->dev; if (dev) qp->iif = dev->ifindex; /* Makes sure compiler wont do silly aliasing games */ barrier(); skb->ip_defrag_offset = offset; /* Insert this fragment in the chain of fragments. */ skb->next = next; if (!next) qp->q.fragments_tail = skb; if (prev) prev->next = skb; else qp->q.fragments = skb; qp->q.stamp = skb->tstamp; qp->q.meat += skb->len; qp->ecn |= ecn; add_frag_mem_limit(qp->q.net, skb->truesize); if (offset == 0) qp->q.flags |= INET_FRAG_FIRST_IN; fragsize = skb->len + ihl; if (fragsize > qp->q.max_size) qp->q.max_size = fragsize; if (ip_hdr(skb)->frag_off & htons(IP_DF) && fragsize > qp->max_df_size) qp->max_df_size = fragsize; if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && qp->q.meat == qp->q.len) { unsigned long orefdst = skb->_skb_refdst; skb->_skb_refdst = 0UL; err = ip_frag_reasm(qp, prev, dev); skb->_skb_refdst = orefdst; return err; } skb_dst_drop(skb); return -EINPROGRESS; err: kfree_skb(skb); return err; } /* Build a new IP datagram from all its fragments. */ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, struct net_device *dev) { struct net *net = container_of(qp->q.net, struct net, ipv4.frags); struct iphdr *iph; struct sk_buff *fp, *head = qp->q.fragments; int len; int ihlen; int err; u8 ecn; ipq_kill(qp); ecn = ip_frag_ecn_table[qp->ecn]; if (unlikely(ecn == 0xff)) { err = -EINVAL; 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_nomem; fp->next = head->next; if (!fp->next) qp->q.fragments_tail = fp; prev->next = fp; skb_morph(head, qp->q.fragments); head->next = qp->q.fragments->next; consume_skb(qp->q.fragments); qp->q.fragments = head; } WARN_ON(!head); WARN_ON(head->ip_defrag_offset != 0); /* Allocate a new buffer for the datagram. */ ihlen = ip_hdrlen(head); len = ihlen + qp->q.len; err = -E2BIG; if (len > 65535) goto out_oversize; /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) goto out_nomem; /* 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_nomem; 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(qp->q.net, clone->truesize); } skb_shinfo(head)->frag_list = head->next; 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(qp->q.net, head->truesize); head->next = NULL; head->dev = dev; head->tstamp = qp->q.stamp; IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size); iph = ip_hdr(head); iph->tot_len = htons(len); iph->tos |= ecn; /* When we set IP_DF on a refragmented skb we must also force a * call to ip_fragment to avoid forwarding a DF-skb of size s while * original sender only sent fragments of size f (where f < s). * * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest * frag seen to avoid sending tiny DF-fragments in case skb was built * from one very small df-fragment and one large non-df frag. */ if (qp->max_df_size == qp->q.max_size) { IPCB(head)->flags |= IPSKB_FRAG_PMTU; iph->frag_off = htons(IP_DF); } else { iph->frag_off = 0; } ip_send_check(iph); __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS); qp->q.fragments = NULL; qp->q.fragments_tail = NULL; return 0; out_nomem: net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp); err = -ENOMEM; goto out_fail; out_oversize: net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr); out_fail: __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); return err; } /* Process an incoming IP datagram fragment. */ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user) { struct net_device *dev = skb->dev ? : skb_dst(skb)->dev; int vif = l3mdev_master_ifindex_rcu(dev); struct ipq *qp; __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS); skb_orphan(skb); /* Lookup (or create) queue header */ qp = ip_find(net, ip_hdr(skb), user, vif); if (qp) { int ret; spin_lock(&qp->q.lock); ret = ip_frag_queue(qp, skb); spin_unlock(&qp->q.lock); ipq_put(qp); return ret; } __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); kfree_skb(skb); return -ENOMEM; } EXPORT_SYMBOL(ip_defrag); struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user) { struct iphdr iph; int netoff; u32 len; if (skb->protocol != htons(ETH_P_IP)) return skb; netoff = skb_network_offset(skb); if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0) return skb; if (iph.ihl < 5 || iph.version != 4) return skb; len = ntohs(iph.tot_len); if (skb->len < netoff + len || len < (iph.ihl * 4)) return skb; if (ip_is_fragment(&iph)) { skb = skb_share_check(skb, GFP_ATOMIC); if (skb) { if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) return skb; if (pskb_trim_rcsum(skb, netoff + len)) return skb; memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); if (ip_defrag(net, skb, user)) return NULL; skb_clear_hash(skb); } } return skb; } EXPORT_SYMBOL(ip_check_defrag); #ifdef CONFIG_SYSCTL static int dist_min; static struct ctl_table ip4_frags_ns_ctl_table[] = { { .procname = "ipfrag_high_thresh", .data = &init_net.ipv4.frags.high_thresh, .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, .extra1 = &init_net.ipv4.frags.low_thresh }, { .procname = "ipfrag_low_thresh", .data = &init_net.ipv4.frags.low_thresh, .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, .extra2 = &init_net.ipv4.frags.high_thresh }, { .procname = "ipfrag_time", .data = &init_net.ipv4.frags.timeout, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { .procname = "ipfrag_max_dist", .data = &init_net.ipv4.frags.max_dist, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &dist_min, }, { } }; /* secret interval has been deprecated */ static int ip4_frags_secret_interval_unused; static struct ctl_table ip4_frags_ctl_table[] = { { .procname = "ipfrag_secret_interval", .data = &ip4_frags_secret_interval_unused, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { } }; static int __net_init ip4_frags_ns_ctl_register(struct net *net) { struct ctl_table *table; struct ctl_table_header *hdr; table = ip4_frags_ns_ctl_table; if (!net_eq(net, &init_net)) { table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL); if (!table) goto err_alloc; table[0].data = &net->ipv4.frags.high_thresh; table[0].extra1 = &net->ipv4.frags.low_thresh; table[0].extra2 = &init_net.ipv4.frags.high_thresh; table[1].data = &net->ipv4.frags.low_thresh; table[1].extra2 = &net->ipv4.frags.high_thresh; table[2].data = &net->ipv4.frags.timeout; table[3].data = &net->ipv4.frags.max_dist; } hdr = register_net_sysctl(net, "net/ipv4", table); if (!hdr) goto err_reg; net->ipv4.frags_hdr = hdr; return 0; err_reg: if (!net_eq(net, &init_net)) kfree(table); err_alloc: return -ENOMEM; } static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net) { struct ctl_table *table; table = net->ipv4.frags_hdr->ctl_table_arg; unregister_net_sysctl_table(net->ipv4.frags_hdr); kfree(table); } static void __init ip4_frags_ctl_register(void) { register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table); } #else static int ip4_frags_ns_ctl_register(struct net *net) { return 0; } static void ip4_frags_ns_ctl_unregister(struct net *net) { } static void __init ip4_frags_ctl_register(void) { } #endif static int __net_init ipv4_frags_init_net(struct net *net) { int res; /* Fragment cache limits. * * The fragment memory accounting code, (tries to) account for * the real memory usage, by measuring both the size of frag * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue)) * and the SKB's truesize. * * A 64K fragment consumes 129736 bytes (44*2944)+200 * (1500 truesize == 2944, sizeof(struct ipq) == 200) * * We will commit 4MB at one time. Should we cross that limit * we will prune down to 3MB, making room for approx 8 big 64K * fragments 8x128k. */ net->ipv4.frags.high_thresh = 4 * 1024 * 1024; net->ipv4.frags.low_thresh = 3 * 1024 * 1024; /* * Important NOTE! Fragment queue must be destroyed before MSL expires. * RFC791 is wrong proposing to prolongate timer each fragment arrival * by TTL. */ net->ipv4.frags.timeout = IP_FRAG_TIME; net->ipv4.frags.max_dist = 64; net->ipv4.frags.f = &ip4_frags; res = inet_frags_init_net(&net->ipv4.frags); if (res < 0) return res; res = ip4_frags_ns_ctl_register(net); if (res < 0) inet_frags_exit_net(&net->ipv4.frags); return res; } static void __net_exit ipv4_frags_exit_net(struct net *net) { ip4_frags_ns_ctl_unregister(net); inet_frags_exit_net(&net->ipv4.frags); } static struct pernet_operations ip4_frags_ops = { .init = ipv4_frags_init_net, .exit = ipv4_frags_exit_net, }; static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed) { return jhash2(data, sizeof(struct frag_v4_compare_key) / sizeof(u32), seed); } static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed) { const struct inet_frag_queue *fq = data; return jhash2((const u32 *)&fq->key.v4, sizeof(struct frag_v4_compare_key) / sizeof(u32), seed); } static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr) { const struct frag_v4_compare_key *key = arg->key; const struct inet_frag_queue *fq = ptr; return !!memcmp(&fq->key, key, sizeof(*key)); } static const struct rhashtable_params ip4_rhash_params = { .head_offset = offsetof(struct inet_frag_queue, node), .key_offset = offsetof(struct inet_frag_queue, key), .key_len = sizeof(struct frag_v4_compare_key), .hashfn = ip4_key_hashfn, .obj_hashfn = ip4_obj_hashfn, .obj_cmpfn = ip4_obj_cmpfn, .automatic_shrinking = true, }; void __init ipfrag_init(void) { ip4_frags.constructor = ip4_frag_init; ip4_frags.destructor = ip4_frag_free; ip4_frags.qsize = sizeof(struct ipq); ip4_frags.frag_expire = ip_expire; ip4_frags.frags_cache_name = ip_frag_cache_name; ip4_frags.rhash_params = ip4_rhash_params; if (inet_frags_init(&ip4_frags)) panic("IP: failed to allocate ip4_frags cache\n"); ip4_frags_ctl_register(); register_pernet_subsys(&ip4_frags_ops); }