/* * 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. */ #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 <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> /* 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 int sysctl_ipfrag_max_dist __read_mostly = 64; struct ipfrag_skb_cb { struct inet_skb_parm h; int offset; }; #define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb)) /* Describe an entry in the "incomplete datagrams" queue. */ struct ipq { struct inet_frag_queue q; u32 user; __be32 saddr; __be32 daddr; __be16 id; u8 protocol; int iif; unsigned int rid; struct inet_peer *peer; }; static struct inet_frags ip4_frags; int ip_frag_nqueues(struct net *net) { return net->ipv4.frags.nqueues; } int ip_frag_mem(struct net *net) { return atomic_read(&net->ipv4.frags.mem); } static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, struct net_device *dev); struct ip4_create_arg { struct iphdr *iph; u32 user; }; static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot) { return jhash_3words((__force u32)id << 16 | prot, (__force u32)saddr, (__force u32)daddr, ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1); } static unsigned int ip4_hashfn(struct inet_frag_queue *q) { struct ipq *ipq; ipq = container_of(q, struct ipq, q); return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol); } static int ip4_frag_match(struct inet_frag_queue *q, void *a) { struct ipq *qp; struct ip4_create_arg *arg = a; qp = container_of(q, struct ipq, q); return (qp->id == arg->iph->id && qp->saddr == arg->iph->saddr && qp->daddr == arg->iph->daddr && qp->protocol == arg->iph->protocol && qp->user == arg->user); } /* Memory Tracking Functions. */ static __inline__ void frag_kfree_skb(struct netns_frags *nf, struct sk_buff *skb, int *work) { if (work) *work -= skb->truesize; atomic_sub(skb->truesize, &nf->mem); kfree_skb(skb); } static void ip4_frag_init(struct inet_frag_queue *q, void *a) { struct ipq *qp = container_of(q, struct ipq, q); struct ip4_create_arg *arg = a; qp->protocol = arg->iph->protocol; qp->id = arg->iph->id; qp->saddr = arg->iph->saddr; qp->daddr = arg->iph->daddr; qp->user = arg->user; qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(arg->iph->saddr, 1) : NULL; } static __inline__ 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 __inline__ void ipq_put(struct ipq *ipq) { inet_frag_put(&ipq->q, &ip4_frags); } /* 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, &ip4_frags); } /* Memory limiting on fragments. Evictor trashes the oldest * fragment queue until we are back under the threshold. */ static void ip_evictor(struct net *net) { int evicted; evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags); if (evicted) IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted); } /* * Oops, a fragment queue timed out. Kill it and send an ICMP reply. */ static void ip_expire(unsigned long arg) { struct ipq *qp; struct net *net; qp = container_of((struct inet_frag_queue *) arg, struct ipq, q); net = container_of(qp->q.net, struct net, ipv4.frags); spin_lock(&qp->q.lock); if (qp->q.last_in & INET_FRAG_COMPLETE) goto out; ipq_kill(qp); IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT); IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) { struct sk_buff *head = qp->q.fragments; rcu_read_lock(); head->dev = dev_get_by_index_rcu(net, qp->iif); if (!head->dev) goto out_rcu_unlock; /* * Only search router table for the head fragment, * when defraging timeout at PRE_ROUTING HOOK. */ if (qp->user == IP_DEFRAG_CONNTRACK_IN && !skb_dst(head)) { const struct iphdr *iph = ip_hdr(head); int err = ip_route_input(head, iph->daddr, iph->saddr, iph->tos, head->dev); if (unlikely(err)) goto out_rcu_unlock; /* * Only an end host needs to send an ICMP * "Fragment Reassembly Timeout" message, per RFC792. */ if (skb_rtable(head)->rt_type != RTN_LOCAL) goto out_rcu_unlock; } /* Send an ICMP "Fragment Reassembly Timeout" message. */ icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); out_rcu_unlock: rcu_read_unlock(); } out: spin_unlock(&qp->q.lock); 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 inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user) { struct inet_frag_queue *q; struct ip4_create_arg arg; unsigned int hash; arg.iph = iph; arg.user = user; read_lock(&ip4_frags.lock); hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol); q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash); if (q == NULL) goto out_nomem; return container_of(q, struct ipq, q); out_nomem: LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n"); return NULL; } /* Is the fragment too far ahead to be part of ipq? */ static inline int ip_frag_too_far(struct ipq *qp) { struct inet_peer *peer = qp->peer; unsigned int max = sysctl_ipfrag_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_BH(net, IPSTATS_MIB_REASMFAILS); } return rc; } static int ip_frag_reinit(struct ipq *qp) { struct sk_buff *fp; if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) { atomic_inc(&qp->q.refcnt); return -ETIMEDOUT; } fp = qp->q.fragments; do { struct sk_buff *xp = fp->next; frag_kfree_skb(qp->q.net, fp, NULL); fp = xp; } while (fp); qp->q.last_in = 0; qp->q.len = 0; qp->q.meat = 0; qp->q.fragments = NULL; qp->iif = 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; int flags, offset; int ihl, end; int err = -ENOENT; if (qp->q.last_in & 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; } 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 - 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 corrrupted. */ if (end < qp->q.len || ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len)) goto err; qp->q.last_in |= 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.last_in & INET_FRAG_LAST_IN) goto err; qp->q.len = end; } } if (end == offset) goto err; err = -ENOMEM; if (pskb_pull(skb, ihl) == NULL) 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 = NULL; for (next = qp->q.fragments; next != NULL; next = next->next) { if (FRAG_CB(next)->offset >= offset) break; /* bingo! */ prev = next; } /* 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 = (FRAG_CB(prev)->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 && FRAG_CB(next)->offset < end) { int i = end - FRAG_CB(next)->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; FRAG_CB(next)->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; frag_kfree_skb(qp->q.net, free_it, NULL); } } FRAG_CB(skb)->offset = offset; /* Insert this fragment in the chain of fragments. */ skb->next = next; if (prev) prev->next = skb; else qp->q.fragments = skb; dev = skb->dev; if (dev) { qp->iif = dev->ifindex; skb->dev = NULL; } qp->q.stamp = skb->tstamp; qp->q.meat += skb->len; atomic_add(skb->truesize, &qp->q.net->mem); if (offset == 0) qp->q.last_in |= INET_FRAG_FIRST_IN; if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && qp->q.meat == qp->q.len) return ip_frag_reasm(qp, prev, dev); write_lock(&ip4_frags.lock); list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list); write_unlock(&ip4_frags.lock); 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; ipq_kill(qp); /* 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; prev->next = fp; skb_morph(head, qp->q.fragments); head->next = qp->q.fragments->next; kfree_skb(qp->q.fragments); qp->q.fragments = head; } WARN_ON(head == NULL); WARN_ON(FRAG_CB(head)->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_cloned(head) && pskb_expand_head(head, 0, 0, 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_frags(head)) { struct sk_buff *clone; int i, plen = 0; if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) 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_shinfo(head)->frags[i].size; 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; atomic_add(clone->truesize, &qp->q.net->mem); } skb_shinfo(head)->frag_list = head->next; skb_push(head, head->data - skb_network_header(head)); atomic_sub(head->truesize, &qp->q.net->mem); 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; atomic_sub(fp->truesize, &qp->q.net->mem); } head->next = NULL; head->dev = dev; head->tstamp = qp->q.stamp; iph = ip_hdr(head); iph->frag_off = 0; iph->tot_len = htons(len); IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); qp->q.fragments = NULL; return 0; out_nomem: LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing " "queue %p\n", qp); err = -ENOMEM; goto out_fail; out_oversize: if (net_ratelimit()) printk(KERN_INFO "Oversized IP packet from %pI4.\n", &qp->saddr); out_fail: IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS); return err; } /* Process an incoming IP datagram fragment. */ int ip_defrag(struct sk_buff *skb, u32 user) { struct ipq *qp; struct net *net; net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev); IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS); /* Start by cleaning up the memory. */ if (atomic_read(&net->ipv4.frags.mem) > net->ipv4.frags.high_thresh) ip_evictor(net); /* Lookup (or create) queue header */ if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) { 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_BH(net, IPSTATS_MIB_REASMFAILS); kfree_skb(skb); return -ENOMEM; } #ifdef CONFIG_SYSCTL static int zero; static struct ctl_table ip4_frags_ns_ctl_table[] = { { .procname = "ipfrag_high_thresh", .data = &init_net.ipv4.frags.high_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec }, { .procname = "ipfrag_low_thresh", .data = &init_net.ipv4.frags.low_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec }, { .procname = "ipfrag_time", .data = &init_net.ipv4.frags.timeout, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { } }; static struct ctl_table ip4_frags_ctl_table[] = { { .procname = "ipfrag_secret_interval", .data = &ip4_frags.secret_interval, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { .procname = "ipfrag_max_dist", .data = &sysctl_ipfrag_max_dist, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &zero }, { } }; 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 == NULL) goto err_alloc; table[0].data = &net->ipv4.frags.high_thresh; table[1].data = &net->ipv4.frags.low_thresh; table[2].data = &net->ipv4.frags.timeout; } hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table); if (hdr == NULL) 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 ip4_frags_ctl_register(void) { register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table); } #else static inline int ip4_frags_ns_ctl_register(struct net *net) { return 0; } static inline void ip4_frags_ns_ctl_unregister(struct net *net) { } static inline void ip4_frags_ctl_register(void) { } #endif static int __net_init ipv4_frags_init_net(struct net *net) { /* * Fragment cache limits. We will commit 256K at one time. Should we * cross that limit we will prune down to 192K. This should cope with * even the most extreme cases without allowing an attacker to * measurably harm machine performance. */ net->ipv4.frags.high_thresh = 256 * 1024; net->ipv4.frags.low_thresh = 192 * 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; inet_frags_init_net(&net->ipv4.frags); return ip4_frags_ns_ctl_register(net); } static void __net_exit ipv4_frags_exit_net(struct net *net) { ip4_frags_ns_ctl_unregister(net); inet_frags_exit_net(&net->ipv4.frags, &ip4_frags); } static struct pernet_operations ip4_frags_ops = { .init = ipv4_frags_init_net, .exit = ipv4_frags_exit_net, }; void __init ipfrag_init(void) { ip4_frags_ctl_register(); register_pernet_subsys(&ip4_frags_ops); ip4_frags.hashfn = ip4_hashfn; ip4_frags.constructor = ip4_frag_init; ip4_frags.destructor = ip4_frag_free; ip4_frags.skb_free = NULL; ip4_frags.qsize = sizeof(struct ipq); ip4_frags.match = ip4_frag_match; ip4_frags.frag_expire = ip_expire; ip4_frags.secret_interval = 10 * 60 * HZ; inet_frags_init(&ip4_frags); } EXPORT_SYMBOL(ip_defrag);