11da177e4SLinus Torvalds /* 21da177e4SLinus Torvalds * INET An implementation of the TCP/IP protocol suite for the LINUX 31da177e4SLinus Torvalds * operating system. INET is implemented using the BSD Socket 41da177e4SLinus Torvalds * interface as the means of communication with the user level. 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * The IP fragmentation functionality. 71da177e4SLinus Torvalds * 81da177e4SLinus Torvalds * Version: $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $ 91da177e4SLinus Torvalds * 101da177e4SLinus Torvalds * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG> 111da177e4SLinus Torvalds * Alan Cox <Alan.Cox@linux.org> 121da177e4SLinus Torvalds * 131da177e4SLinus Torvalds * Fixes: 141da177e4SLinus Torvalds * Alan Cox : Split from ip.c , see ip_input.c for history. 151da177e4SLinus Torvalds * David S. Miller : Begin massive cleanup... 161da177e4SLinus Torvalds * Andi Kleen : Add sysctls. 171da177e4SLinus Torvalds * xxxx : Overlapfrag bug. 181da177e4SLinus Torvalds * Ultima : ip_expire() kernel panic. 191da177e4SLinus Torvalds * Bill Hawes : Frag accounting and evictor fixes. 201da177e4SLinus Torvalds * John McDonald : 0 length frag bug. 211da177e4SLinus Torvalds * Alexey Kuznetsov: SMP races, threading, cleanup. 221da177e4SLinus Torvalds * Patrick McHardy : LRU queue of frag heads for evictor. 231da177e4SLinus Torvalds */ 241da177e4SLinus Torvalds 2589cee8b1SHerbert Xu #include <linux/compiler.h> 261da177e4SLinus Torvalds #include <linux/module.h> 271da177e4SLinus Torvalds #include <linux/types.h> 281da177e4SLinus Torvalds #include <linux/mm.h> 291da177e4SLinus Torvalds #include <linux/jiffies.h> 301da177e4SLinus Torvalds #include <linux/skbuff.h> 311da177e4SLinus Torvalds #include <linux/list.h> 321da177e4SLinus Torvalds #include <linux/ip.h> 331da177e4SLinus Torvalds #include <linux/icmp.h> 341da177e4SLinus Torvalds #include <linux/netdevice.h> 351da177e4SLinus Torvalds #include <linux/jhash.h> 361da177e4SLinus Torvalds #include <linux/random.h> 371da177e4SLinus Torvalds #include <net/sock.h> 381da177e4SLinus Torvalds #include <net/ip.h> 391da177e4SLinus Torvalds #include <net/icmp.h> 401da177e4SLinus Torvalds #include <net/checksum.h> 4189cee8b1SHerbert Xu #include <net/inetpeer.h> 425ab11c98SPavel Emelyanov #include <net/inet_frag.h> 431da177e4SLinus Torvalds #include <linux/tcp.h> 441da177e4SLinus Torvalds #include <linux/udp.h> 451da177e4SLinus Torvalds #include <linux/inet.h> 461da177e4SLinus Torvalds #include <linux/netfilter_ipv4.h> 471da177e4SLinus Torvalds 481da177e4SLinus Torvalds /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 491da177e4SLinus Torvalds * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c 501da177e4SLinus Torvalds * as well. Or notify me, at least. --ANK 511da177e4SLinus Torvalds */ 521da177e4SLinus Torvalds 53ab32ea5dSBrian Haley int sysctl_ipfrag_max_dist __read_mostly = 64; 5489cee8b1SHerbert Xu 551da177e4SLinus Torvalds struct ipfrag_skb_cb 561da177e4SLinus Torvalds { 571da177e4SLinus Torvalds struct inet_skb_parm h; 581da177e4SLinus Torvalds int offset; 591da177e4SLinus Torvalds }; 601da177e4SLinus Torvalds 611da177e4SLinus Torvalds #define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb)) 621da177e4SLinus Torvalds 631da177e4SLinus Torvalds /* Describe an entry in the "incomplete datagrams" queue. */ 641da177e4SLinus Torvalds struct ipq { 655ab11c98SPavel Emelyanov struct inet_frag_queue q; 665ab11c98SPavel Emelyanov 671da177e4SLinus Torvalds u32 user; 6818277770SAl Viro __be32 saddr; 6918277770SAl Viro __be32 daddr; 7018277770SAl Viro __be16 id; 711da177e4SLinus Torvalds u8 protocol; 7289cee8b1SHerbert Xu int iif; 7389cee8b1SHerbert Xu unsigned int rid; 7489cee8b1SHerbert Xu struct inet_peer *peer; 751da177e4SLinus Torvalds }; 761da177e4SLinus Torvalds 7704128f23SPavel Emelyanov struct inet_frags_ctl ip4_frags_ctl __read_mostly = { 7804128f23SPavel Emelyanov /* 7904128f23SPavel Emelyanov * Fragment cache limits. We will commit 256K at one time. Should we 8004128f23SPavel Emelyanov * cross that limit we will prune down to 192K. This should cope with 8104128f23SPavel Emelyanov * even the most extreme cases without allowing an attacker to 8204128f23SPavel Emelyanov * measurably harm machine performance. 8304128f23SPavel Emelyanov */ 8404128f23SPavel Emelyanov .high_thresh = 256 * 1024, 8504128f23SPavel Emelyanov .low_thresh = 192 * 1024, 8604128f23SPavel Emelyanov 8704128f23SPavel Emelyanov /* 8804128f23SPavel Emelyanov * Important NOTE! Fragment queue must be destroyed before MSL expires. 8904128f23SPavel Emelyanov * RFC791 is wrong proposing to prolongate timer each fragment arrival 9004128f23SPavel Emelyanov * by TTL. 9104128f23SPavel Emelyanov */ 9204128f23SPavel Emelyanov .timeout = IP_FRAG_TIME, 9304128f23SPavel Emelyanov .secret_interval = 10 * 60 * HZ, 9404128f23SPavel Emelyanov }; 9504128f23SPavel Emelyanov 967eb95156SPavel Emelyanov static struct inet_frags ip4_frags; 971da177e4SLinus Torvalds 987eb95156SPavel Emelyanov int ip_frag_nqueues(void) 997eb95156SPavel Emelyanov { 1007eb95156SPavel Emelyanov return ip4_frags.nqueues; 1017eb95156SPavel Emelyanov } 1021da177e4SLinus Torvalds 1037eb95156SPavel Emelyanov int ip_frag_mem(void) 1047eb95156SPavel Emelyanov { 1057eb95156SPavel Emelyanov return atomic_read(&ip4_frags.mem); 1067eb95156SPavel Emelyanov } 1071da177e4SLinus Torvalds 1081706d587SHerbert Xu static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, 1091706d587SHerbert Xu struct net_device *dev); 1101706d587SHerbert Xu 11118277770SAl Viro static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot) 1121da177e4SLinus Torvalds { 11318277770SAl Viro return jhash_3words((__force u32)id << 16 | prot, 11418277770SAl Viro (__force u32)saddr, (__force u32)daddr, 1157eb95156SPavel Emelyanov ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1); 1161da177e4SLinus Torvalds } 1171da177e4SLinus Torvalds 1181da177e4SLinus Torvalds static void ipfrag_secret_rebuild(unsigned long dummy) 1191da177e4SLinus Torvalds { 1201da177e4SLinus Torvalds unsigned long now = jiffies; 1211da177e4SLinus Torvalds int i; 1221da177e4SLinus Torvalds 1237eb95156SPavel Emelyanov write_lock(&ip4_frags.lock); 1247eb95156SPavel Emelyanov get_random_bytes(&ip4_frags.rnd, sizeof(u32)); 1257eb95156SPavel Emelyanov for (i = 0; i < INETFRAGS_HASHSZ; i++) { 1261da177e4SLinus Torvalds struct ipq *q; 127e7c8a41eSYasuyuki Kozakai struct hlist_node *p, *n; 1281da177e4SLinus Torvalds 1297eb95156SPavel Emelyanov hlist_for_each_entry_safe(q, p, n, &ip4_frags.hash[i], q.list) { 1301da177e4SLinus Torvalds unsigned int hval = ipqhashfn(q->id, q->saddr, 1311da177e4SLinus Torvalds q->daddr, q->protocol); 1321da177e4SLinus Torvalds 1331da177e4SLinus Torvalds if (hval != i) { 1345ab11c98SPavel Emelyanov hlist_del(&q->q.list); 1351da177e4SLinus Torvalds 1361da177e4SLinus Torvalds /* Relink to new hash chain. */ 1377eb95156SPavel Emelyanov hlist_add_head(&q->q.list, &ip4_frags.hash[hval]); 1381da177e4SLinus Torvalds } 1391da177e4SLinus Torvalds } 1401da177e4SLinus Torvalds } 1417eb95156SPavel Emelyanov write_unlock(&ip4_frags.lock); 1421da177e4SLinus Torvalds 14304128f23SPavel Emelyanov mod_timer(&ip4_frags.secret_timer, now + ip4_frags_ctl.secret_interval); 1441da177e4SLinus Torvalds } 1451da177e4SLinus Torvalds 1461da177e4SLinus Torvalds /* Memory Tracking Functions. */ 1471da177e4SLinus Torvalds static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work) 1481da177e4SLinus Torvalds { 1491da177e4SLinus Torvalds if (work) 1501da177e4SLinus Torvalds *work -= skb->truesize; 1517eb95156SPavel Emelyanov atomic_sub(skb->truesize, &ip4_frags.mem); 1521da177e4SLinus Torvalds kfree_skb(skb); 1531da177e4SLinus Torvalds } 1541da177e4SLinus Torvalds 1551da177e4SLinus Torvalds static __inline__ void frag_free_queue(struct ipq *qp, int *work) 1561da177e4SLinus Torvalds { 1571da177e4SLinus Torvalds if (work) 1581da177e4SLinus Torvalds *work -= sizeof(struct ipq); 1597eb95156SPavel Emelyanov atomic_sub(sizeof(struct ipq), &ip4_frags.mem); 1601da177e4SLinus Torvalds kfree(qp); 1611da177e4SLinus Torvalds } 1621da177e4SLinus Torvalds 1631da177e4SLinus Torvalds static __inline__ struct ipq *frag_alloc_queue(void) 1641da177e4SLinus Torvalds { 1651da177e4SLinus Torvalds struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC); 1661da177e4SLinus Torvalds 1671da177e4SLinus Torvalds if (!qp) 1681da177e4SLinus Torvalds return NULL; 1697eb95156SPavel Emelyanov atomic_add(sizeof(struct ipq), &ip4_frags.mem); 1701da177e4SLinus Torvalds return qp; 1711da177e4SLinus Torvalds } 1721da177e4SLinus Torvalds 1731da177e4SLinus Torvalds 1741da177e4SLinus Torvalds /* Destruction primitives. */ 1751da177e4SLinus Torvalds 1761da177e4SLinus Torvalds /* Complete destruction of ipq. */ 1771da177e4SLinus Torvalds static void ip_frag_destroy(struct ipq *qp, int *work) 1781da177e4SLinus Torvalds { 1791da177e4SLinus Torvalds struct sk_buff *fp; 1801da177e4SLinus Torvalds 1815ab11c98SPavel Emelyanov BUG_TRAP(qp->q.last_in&COMPLETE); 1825ab11c98SPavel Emelyanov BUG_TRAP(del_timer(&qp->q.timer) == 0); 1831da177e4SLinus Torvalds 18489cee8b1SHerbert Xu if (qp->peer) 18589cee8b1SHerbert Xu inet_putpeer(qp->peer); 18689cee8b1SHerbert Xu 1871da177e4SLinus Torvalds /* Release all fragment data. */ 1885ab11c98SPavel Emelyanov fp = qp->q.fragments; 1891da177e4SLinus Torvalds while (fp) { 1901da177e4SLinus Torvalds struct sk_buff *xp = fp->next; 1911da177e4SLinus Torvalds 1921da177e4SLinus Torvalds frag_kfree_skb(fp, work); 1931da177e4SLinus Torvalds fp = xp; 1941da177e4SLinus Torvalds } 1951da177e4SLinus Torvalds 1961da177e4SLinus Torvalds /* Finally, release the queue descriptor itself. */ 1971da177e4SLinus Torvalds frag_free_queue(qp, work); 1981da177e4SLinus Torvalds } 1991da177e4SLinus Torvalds 2001da177e4SLinus Torvalds static __inline__ void ipq_put(struct ipq *ipq, int *work) 2011da177e4SLinus Torvalds { 2025ab11c98SPavel Emelyanov if (atomic_dec_and_test(&ipq->q.refcnt)) 2031da177e4SLinus Torvalds ip_frag_destroy(ipq, work); 2041da177e4SLinus Torvalds } 2051da177e4SLinus Torvalds 2061da177e4SLinus Torvalds /* Kill ipq entry. It is not destroyed immediately, 2071da177e4SLinus Torvalds * because caller (and someone more) holds reference count. 2081da177e4SLinus Torvalds */ 2091da177e4SLinus Torvalds static void ipq_kill(struct ipq *ipq) 2101da177e4SLinus Torvalds { 211277e650dSPavel Emelyanov inet_frag_kill(&ipq->q, &ip4_frags); 2121da177e4SLinus Torvalds } 2131da177e4SLinus Torvalds 2141da177e4SLinus Torvalds /* Memory limiting on fragments. Evictor trashes the oldest 2151da177e4SLinus Torvalds * fragment queue until we are back under the threshold. 2161da177e4SLinus Torvalds */ 2171da177e4SLinus Torvalds static void ip_evictor(void) 2181da177e4SLinus Torvalds { 2191da177e4SLinus Torvalds struct ipq *qp; 2201da177e4SLinus Torvalds struct list_head *tmp; 2211da177e4SLinus Torvalds int work; 2221da177e4SLinus Torvalds 22304128f23SPavel Emelyanov work = atomic_read(&ip4_frags.mem) - ip4_frags_ctl.low_thresh; 2241da177e4SLinus Torvalds if (work <= 0) 2251da177e4SLinus Torvalds return; 2261da177e4SLinus Torvalds 2271da177e4SLinus Torvalds while (work > 0) { 2287eb95156SPavel Emelyanov read_lock(&ip4_frags.lock); 2297eb95156SPavel Emelyanov if (list_empty(&ip4_frags.lru_list)) { 2307eb95156SPavel Emelyanov read_unlock(&ip4_frags.lock); 2311da177e4SLinus Torvalds return; 2321da177e4SLinus Torvalds } 2337eb95156SPavel Emelyanov tmp = ip4_frags.lru_list.next; 2345ab11c98SPavel Emelyanov qp = list_entry(tmp, struct ipq, q.lru_list); 2355ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 2367eb95156SPavel Emelyanov read_unlock(&ip4_frags.lock); 2371da177e4SLinus Torvalds 2385ab11c98SPavel Emelyanov spin_lock(&qp->q.lock); 2395ab11c98SPavel Emelyanov if (!(qp->q.last_in&COMPLETE)) 2401da177e4SLinus Torvalds ipq_kill(qp); 2415ab11c98SPavel Emelyanov spin_unlock(&qp->q.lock); 2421da177e4SLinus Torvalds 2431da177e4SLinus Torvalds ipq_put(qp, &work); 2441da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 2451da177e4SLinus Torvalds } 2461da177e4SLinus Torvalds } 2471da177e4SLinus Torvalds 2481da177e4SLinus Torvalds /* 2491da177e4SLinus Torvalds * Oops, a fragment queue timed out. Kill it and send an ICMP reply. 2501da177e4SLinus Torvalds */ 2511da177e4SLinus Torvalds static void ip_expire(unsigned long arg) 2521da177e4SLinus Torvalds { 2531da177e4SLinus Torvalds struct ipq *qp = (struct ipq *) arg; 2541da177e4SLinus Torvalds 2555ab11c98SPavel Emelyanov spin_lock(&qp->q.lock); 2561da177e4SLinus Torvalds 2575ab11c98SPavel Emelyanov if (qp->q.last_in & COMPLETE) 2581da177e4SLinus Torvalds goto out; 2591da177e4SLinus Torvalds 2601da177e4SLinus Torvalds ipq_kill(qp); 2611da177e4SLinus Torvalds 2621da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT); 2631da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 2641da177e4SLinus Torvalds 2655ab11c98SPavel Emelyanov if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) { 2665ab11c98SPavel Emelyanov struct sk_buff *head = qp->q.fragments; 2671da177e4SLinus Torvalds /* Send an ICMP "Fragment Reassembly Timeout" message. */ 268881d966bSEric W. Biederman if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) { 2691da177e4SLinus Torvalds icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); 2701da177e4SLinus Torvalds dev_put(head->dev); 2711da177e4SLinus Torvalds } 2721da177e4SLinus Torvalds } 2731da177e4SLinus Torvalds out: 2745ab11c98SPavel Emelyanov spin_unlock(&qp->q.lock); 2751da177e4SLinus Torvalds ipq_put(qp, NULL); 2761da177e4SLinus Torvalds } 2771da177e4SLinus Torvalds 2781da177e4SLinus Torvalds /* Creation primitives. */ 2791da177e4SLinus Torvalds 28055c0022eSDavid S. Miller static struct ipq *ip_frag_intern(struct ipq *qp_in) 2811da177e4SLinus Torvalds { 2821da177e4SLinus Torvalds struct ipq *qp; 283e7c8a41eSYasuyuki Kozakai #ifdef CONFIG_SMP 284e7c8a41eSYasuyuki Kozakai struct hlist_node *n; 285e7c8a41eSYasuyuki Kozakai #endif 28655c0022eSDavid S. Miller unsigned int hash; 28755c0022eSDavid S. Miller 2887eb95156SPavel Emelyanov write_lock(&ip4_frags.lock); 28955c0022eSDavid S. Miller hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr, 29055c0022eSDavid S. Miller qp_in->protocol); 2911da177e4SLinus Torvalds #ifdef CONFIG_SMP 2921da177e4SLinus Torvalds /* With SMP race we have to recheck hash table, because 2931da177e4SLinus Torvalds * such entry could be created on other cpu, while we 2941da177e4SLinus Torvalds * promoted read lock to write lock. 2951da177e4SLinus Torvalds */ 2967eb95156SPavel Emelyanov hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) { 2971da177e4SLinus Torvalds if (qp->id == qp_in->id && 2981da177e4SLinus Torvalds qp->saddr == qp_in->saddr && 2991da177e4SLinus Torvalds qp->daddr == qp_in->daddr && 3001da177e4SLinus Torvalds qp->protocol == qp_in->protocol && 3011da177e4SLinus Torvalds qp->user == qp_in->user) { 3025ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 3037eb95156SPavel Emelyanov write_unlock(&ip4_frags.lock); 3045ab11c98SPavel Emelyanov qp_in->q.last_in |= COMPLETE; 3051da177e4SLinus Torvalds ipq_put(qp_in, NULL); 3061da177e4SLinus Torvalds return qp; 3071da177e4SLinus Torvalds } 3081da177e4SLinus Torvalds } 3091da177e4SLinus Torvalds #endif 3101da177e4SLinus Torvalds qp = qp_in; 3111da177e4SLinus Torvalds 31204128f23SPavel Emelyanov if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) 3135ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 3141da177e4SLinus Torvalds 3155ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 3167eb95156SPavel Emelyanov hlist_add_head(&qp->q.list, &ip4_frags.hash[hash]); 3175ab11c98SPavel Emelyanov INIT_LIST_HEAD(&qp->q.lru_list); 3187eb95156SPavel Emelyanov list_add_tail(&qp->q.lru_list, &ip4_frags.lru_list); 3197eb95156SPavel Emelyanov ip4_frags.nqueues++; 3207eb95156SPavel Emelyanov write_unlock(&ip4_frags.lock); 3211da177e4SLinus Torvalds return qp; 3221da177e4SLinus Torvalds } 3231da177e4SLinus Torvalds 3241da177e4SLinus Torvalds /* Add an entry to the 'ipq' queue for a newly received IP datagram. */ 32555c0022eSDavid S. Miller static struct ipq *ip_frag_create(struct iphdr *iph, u32 user) 3261da177e4SLinus Torvalds { 3271da177e4SLinus Torvalds struct ipq *qp; 3281da177e4SLinus Torvalds 3291da177e4SLinus Torvalds if ((qp = frag_alloc_queue()) == NULL) 3301da177e4SLinus Torvalds goto out_nomem; 3311da177e4SLinus Torvalds 3321da177e4SLinus Torvalds qp->protocol = iph->protocol; 3335ab11c98SPavel Emelyanov qp->q.last_in = 0; 3341da177e4SLinus Torvalds qp->id = iph->id; 3351da177e4SLinus Torvalds qp->saddr = iph->saddr; 3361da177e4SLinus Torvalds qp->daddr = iph->daddr; 3371da177e4SLinus Torvalds qp->user = user; 3385ab11c98SPavel Emelyanov qp->q.len = 0; 3395ab11c98SPavel Emelyanov qp->q.meat = 0; 3405ab11c98SPavel Emelyanov qp->q.fragments = NULL; 3411da177e4SLinus Torvalds qp->iif = 0; 34289cee8b1SHerbert Xu qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL; 3431da177e4SLinus Torvalds 3441da177e4SLinus Torvalds /* Initialize a timer for this entry. */ 3455ab11c98SPavel Emelyanov init_timer(&qp->q.timer); 3465ab11c98SPavel Emelyanov qp->q.timer.data = (unsigned long) qp; /* pointer to queue */ 3475ab11c98SPavel Emelyanov qp->q.timer.function = ip_expire; /* expire function */ 3485ab11c98SPavel Emelyanov spin_lock_init(&qp->q.lock); 3495ab11c98SPavel Emelyanov atomic_set(&qp->q.refcnt, 1); 3501da177e4SLinus Torvalds 35155c0022eSDavid S. Miller return ip_frag_intern(qp); 3521da177e4SLinus Torvalds 3531da177e4SLinus Torvalds out_nomem: 35464ce2073SPatrick McHardy LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n"); 3551da177e4SLinus Torvalds return NULL; 3561da177e4SLinus Torvalds } 3571da177e4SLinus Torvalds 3581da177e4SLinus Torvalds /* Find the correct entry in the "incomplete datagrams" queue for 3591da177e4SLinus Torvalds * this IP datagram, and create new one, if nothing is found. 3601da177e4SLinus Torvalds */ 3611da177e4SLinus Torvalds static inline struct ipq *ip_find(struct iphdr *iph, u32 user) 3621da177e4SLinus Torvalds { 36376ab608dSAlexey Dobriyan __be16 id = iph->id; 36418277770SAl Viro __be32 saddr = iph->saddr; 36518277770SAl Viro __be32 daddr = iph->daddr; 3661da177e4SLinus Torvalds __u8 protocol = iph->protocol; 36755c0022eSDavid S. Miller unsigned int hash; 3681da177e4SLinus Torvalds struct ipq *qp; 369e7c8a41eSYasuyuki Kozakai struct hlist_node *n; 3701da177e4SLinus Torvalds 3717eb95156SPavel Emelyanov read_lock(&ip4_frags.lock); 37255c0022eSDavid S. Miller hash = ipqhashfn(id, saddr, daddr, protocol); 3737eb95156SPavel Emelyanov hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) { 3741da177e4SLinus Torvalds if (qp->id == id && 3751da177e4SLinus Torvalds qp->saddr == saddr && 3761da177e4SLinus Torvalds qp->daddr == daddr && 3771da177e4SLinus Torvalds qp->protocol == protocol && 3781da177e4SLinus Torvalds qp->user == user) { 3795ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 3807eb95156SPavel Emelyanov read_unlock(&ip4_frags.lock); 3811da177e4SLinus Torvalds return qp; 3821da177e4SLinus Torvalds } 3831da177e4SLinus Torvalds } 3847eb95156SPavel Emelyanov read_unlock(&ip4_frags.lock); 3851da177e4SLinus Torvalds 38655c0022eSDavid S. Miller return ip_frag_create(iph, user); 3871da177e4SLinus Torvalds } 3881da177e4SLinus Torvalds 38989cee8b1SHerbert Xu /* Is the fragment too far ahead to be part of ipq? */ 39089cee8b1SHerbert Xu static inline int ip_frag_too_far(struct ipq *qp) 39189cee8b1SHerbert Xu { 39289cee8b1SHerbert Xu struct inet_peer *peer = qp->peer; 39389cee8b1SHerbert Xu unsigned int max = sysctl_ipfrag_max_dist; 39489cee8b1SHerbert Xu unsigned int start, end; 39589cee8b1SHerbert Xu 39689cee8b1SHerbert Xu int rc; 39789cee8b1SHerbert Xu 39889cee8b1SHerbert Xu if (!peer || !max) 39989cee8b1SHerbert Xu return 0; 40089cee8b1SHerbert Xu 40189cee8b1SHerbert Xu start = qp->rid; 40289cee8b1SHerbert Xu end = atomic_inc_return(&peer->rid); 40389cee8b1SHerbert Xu qp->rid = end; 40489cee8b1SHerbert Xu 4055ab11c98SPavel Emelyanov rc = qp->q.fragments && (end - start) > max; 40689cee8b1SHerbert Xu 40789cee8b1SHerbert Xu if (rc) { 40889cee8b1SHerbert Xu IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 40989cee8b1SHerbert Xu } 41089cee8b1SHerbert Xu 41189cee8b1SHerbert Xu return rc; 41289cee8b1SHerbert Xu } 41389cee8b1SHerbert Xu 41489cee8b1SHerbert Xu static int ip_frag_reinit(struct ipq *qp) 41589cee8b1SHerbert Xu { 41689cee8b1SHerbert Xu struct sk_buff *fp; 41789cee8b1SHerbert Xu 41804128f23SPavel Emelyanov if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) { 4195ab11c98SPavel Emelyanov atomic_inc(&qp->q.refcnt); 42089cee8b1SHerbert Xu return -ETIMEDOUT; 42189cee8b1SHerbert Xu } 42289cee8b1SHerbert Xu 4235ab11c98SPavel Emelyanov fp = qp->q.fragments; 42489cee8b1SHerbert Xu do { 42589cee8b1SHerbert Xu struct sk_buff *xp = fp->next; 42689cee8b1SHerbert Xu frag_kfree_skb(fp, NULL); 42789cee8b1SHerbert Xu fp = xp; 42889cee8b1SHerbert Xu } while (fp); 42989cee8b1SHerbert Xu 4305ab11c98SPavel Emelyanov qp->q.last_in = 0; 4315ab11c98SPavel Emelyanov qp->q.len = 0; 4325ab11c98SPavel Emelyanov qp->q.meat = 0; 4335ab11c98SPavel Emelyanov qp->q.fragments = NULL; 43489cee8b1SHerbert Xu qp->iif = 0; 43589cee8b1SHerbert Xu 43689cee8b1SHerbert Xu return 0; 43789cee8b1SHerbert Xu } 43889cee8b1SHerbert Xu 4391da177e4SLinus Torvalds /* Add new segment to existing queue. */ 4401706d587SHerbert Xu static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) 4411da177e4SLinus Torvalds { 4421da177e4SLinus Torvalds struct sk_buff *prev, *next; 4431706d587SHerbert Xu struct net_device *dev; 4441da177e4SLinus Torvalds int flags, offset; 4451da177e4SLinus Torvalds int ihl, end; 4461706d587SHerbert Xu int err = -ENOENT; 4471da177e4SLinus Torvalds 4485ab11c98SPavel Emelyanov if (qp->q.last_in & COMPLETE) 4491da177e4SLinus Torvalds goto err; 4501da177e4SLinus Torvalds 45189cee8b1SHerbert Xu if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) && 4521706d587SHerbert Xu unlikely(ip_frag_too_far(qp)) && 4531706d587SHerbert Xu unlikely(err = ip_frag_reinit(qp))) { 45489cee8b1SHerbert Xu ipq_kill(qp); 45589cee8b1SHerbert Xu goto err; 45689cee8b1SHerbert Xu } 45789cee8b1SHerbert Xu 458eddc9ec5SArnaldo Carvalho de Melo offset = ntohs(ip_hdr(skb)->frag_off); 4591da177e4SLinus Torvalds flags = offset & ~IP_OFFSET; 4601da177e4SLinus Torvalds offset &= IP_OFFSET; 4611da177e4SLinus Torvalds offset <<= 3; /* offset is in 8-byte chunks */ 462c9bdd4b5SArnaldo Carvalho de Melo ihl = ip_hdrlen(skb); 4631da177e4SLinus Torvalds 4641da177e4SLinus Torvalds /* Determine the position of this fragment. */ 4651da177e4SLinus Torvalds end = offset + skb->len - ihl; 4661706d587SHerbert Xu err = -EINVAL; 4671da177e4SLinus Torvalds 4681da177e4SLinus Torvalds /* Is this the final fragment? */ 4691da177e4SLinus Torvalds if ((flags & IP_MF) == 0) { 4701da177e4SLinus Torvalds /* If we already have some bits beyond end 4711da177e4SLinus Torvalds * or have different end, the segment is corrrupted. 4721da177e4SLinus Torvalds */ 4735ab11c98SPavel Emelyanov if (end < qp->q.len || 4745ab11c98SPavel Emelyanov ((qp->q.last_in & LAST_IN) && end != qp->q.len)) 4751da177e4SLinus Torvalds goto err; 4765ab11c98SPavel Emelyanov qp->q.last_in |= LAST_IN; 4775ab11c98SPavel Emelyanov qp->q.len = end; 4781da177e4SLinus Torvalds } else { 4791da177e4SLinus Torvalds if (end&7) { 4801da177e4SLinus Torvalds end &= ~7; 4811da177e4SLinus Torvalds if (skb->ip_summed != CHECKSUM_UNNECESSARY) 4821da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 4831da177e4SLinus Torvalds } 4845ab11c98SPavel Emelyanov if (end > qp->q.len) { 4851da177e4SLinus Torvalds /* Some bits beyond end -> corruption. */ 4865ab11c98SPavel Emelyanov if (qp->q.last_in & LAST_IN) 4871da177e4SLinus Torvalds goto err; 4885ab11c98SPavel Emelyanov qp->q.len = end; 4891da177e4SLinus Torvalds } 4901da177e4SLinus Torvalds } 4911da177e4SLinus Torvalds if (end == offset) 4921da177e4SLinus Torvalds goto err; 4931da177e4SLinus Torvalds 4941706d587SHerbert Xu err = -ENOMEM; 4951da177e4SLinus Torvalds if (pskb_pull(skb, ihl) == NULL) 4961da177e4SLinus Torvalds goto err; 4971706d587SHerbert Xu 4981706d587SHerbert Xu err = pskb_trim_rcsum(skb, end - offset); 4991706d587SHerbert Xu if (err) 5001da177e4SLinus Torvalds goto err; 5011da177e4SLinus Torvalds 5021da177e4SLinus Torvalds /* Find out which fragments are in front and at the back of us 5031da177e4SLinus Torvalds * in the chain of fragments so far. We must know where to put 5041da177e4SLinus Torvalds * this fragment, right? 5051da177e4SLinus Torvalds */ 5061da177e4SLinus Torvalds prev = NULL; 5075ab11c98SPavel Emelyanov for (next = qp->q.fragments; next != NULL; next = next->next) { 5081da177e4SLinus Torvalds if (FRAG_CB(next)->offset >= offset) 5091da177e4SLinus Torvalds break; /* bingo! */ 5101da177e4SLinus Torvalds prev = next; 5111da177e4SLinus Torvalds } 5121da177e4SLinus Torvalds 5131da177e4SLinus Torvalds /* We found where to put this one. Check for overlap with 5141da177e4SLinus Torvalds * preceding fragment, and, if needed, align things so that 5151da177e4SLinus Torvalds * any overlaps are eliminated. 5161da177e4SLinus Torvalds */ 5171da177e4SLinus Torvalds if (prev) { 5181da177e4SLinus Torvalds int i = (FRAG_CB(prev)->offset + prev->len) - offset; 5191da177e4SLinus Torvalds 5201da177e4SLinus Torvalds if (i > 0) { 5211da177e4SLinus Torvalds offset += i; 5221706d587SHerbert Xu err = -EINVAL; 5231da177e4SLinus Torvalds if (end <= offset) 5241da177e4SLinus Torvalds goto err; 5251706d587SHerbert Xu err = -ENOMEM; 5261da177e4SLinus Torvalds if (!pskb_pull(skb, i)) 5271da177e4SLinus Torvalds goto err; 5281da177e4SLinus Torvalds if (skb->ip_summed != CHECKSUM_UNNECESSARY) 5291da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 5301da177e4SLinus Torvalds } 5311da177e4SLinus Torvalds } 5321da177e4SLinus Torvalds 5331706d587SHerbert Xu err = -ENOMEM; 5341706d587SHerbert Xu 5351da177e4SLinus Torvalds while (next && FRAG_CB(next)->offset < end) { 5361da177e4SLinus Torvalds int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */ 5371da177e4SLinus Torvalds 5381da177e4SLinus Torvalds if (i < next->len) { 5391da177e4SLinus Torvalds /* Eat head of the next overlapped fragment 5401da177e4SLinus Torvalds * and leave the loop. The next ones cannot overlap. 5411da177e4SLinus Torvalds */ 5421da177e4SLinus Torvalds if (!pskb_pull(next, i)) 5431da177e4SLinus Torvalds goto err; 5441da177e4SLinus Torvalds FRAG_CB(next)->offset += i; 5455ab11c98SPavel Emelyanov qp->q.meat -= i; 5461da177e4SLinus Torvalds if (next->ip_summed != CHECKSUM_UNNECESSARY) 5471da177e4SLinus Torvalds next->ip_summed = CHECKSUM_NONE; 5481da177e4SLinus Torvalds break; 5491da177e4SLinus Torvalds } else { 5501da177e4SLinus Torvalds struct sk_buff *free_it = next; 5511da177e4SLinus Torvalds 55247c6bf77SPeter Zijlstra /* Old fragment is completely overridden with 5531da177e4SLinus Torvalds * new one drop it. 5541da177e4SLinus Torvalds */ 5551da177e4SLinus Torvalds next = next->next; 5561da177e4SLinus Torvalds 5571da177e4SLinus Torvalds if (prev) 5581da177e4SLinus Torvalds prev->next = next; 5591da177e4SLinus Torvalds else 5605ab11c98SPavel Emelyanov qp->q.fragments = next; 5611da177e4SLinus Torvalds 5625ab11c98SPavel Emelyanov qp->q.meat -= free_it->len; 5631da177e4SLinus Torvalds frag_kfree_skb(free_it, NULL); 5641da177e4SLinus Torvalds } 5651da177e4SLinus Torvalds } 5661da177e4SLinus Torvalds 5671da177e4SLinus Torvalds FRAG_CB(skb)->offset = offset; 5681da177e4SLinus Torvalds 5691da177e4SLinus Torvalds /* Insert this fragment in the chain of fragments. */ 5701da177e4SLinus Torvalds skb->next = next; 5711da177e4SLinus Torvalds if (prev) 5721da177e4SLinus Torvalds prev->next = skb; 5731da177e4SLinus Torvalds else 5745ab11c98SPavel Emelyanov qp->q.fragments = skb; 5751da177e4SLinus Torvalds 5761706d587SHerbert Xu dev = skb->dev; 5771706d587SHerbert Xu if (dev) { 5781706d587SHerbert Xu qp->iif = dev->ifindex; 5791da177e4SLinus Torvalds skb->dev = NULL; 5801706d587SHerbert Xu } 5815ab11c98SPavel Emelyanov qp->q.stamp = skb->tstamp; 5825ab11c98SPavel Emelyanov qp->q.meat += skb->len; 5837eb95156SPavel Emelyanov atomic_add(skb->truesize, &ip4_frags.mem); 5841da177e4SLinus Torvalds if (offset == 0) 5855ab11c98SPavel Emelyanov qp->q.last_in |= FIRST_IN; 5861da177e4SLinus Torvalds 5875ab11c98SPavel Emelyanov if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len) 5881706d587SHerbert Xu return ip_frag_reasm(qp, prev, dev); 5891706d587SHerbert Xu 5907eb95156SPavel Emelyanov write_lock(&ip4_frags.lock); 5917eb95156SPavel Emelyanov list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list); 5927eb95156SPavel Emelyanov write_unlock(&ip4_frags.lock); 5931706d587SHerbert Xu return -EINPROGRESS; 5941da177e4SLinus Torvalds 5951da177e4SLinus Torvalds err: 5961da177e4SLinus Torvalds kfree_skb(skb); 5971706d587SHerbert Xu return err; 5981da177e4SLinus Torvalds } 5991da177e4SLinus Torvalds 6001da177e4SLinus Torvalds 6011da177e4SLinus Torvalds /* Build a new IP datagram from all its fragments. */ 6021da177e4SLinus Torvalds 6031706d587SHerbert Xu static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, 6041706d587SHerbert Xu struct net_device *dev) 6051da177e4SLinus Torvalds { 6061da177e4SLinus Torvalds struct iphdr *iph; 6075ab11c98SPavel Emelyanov struct sk_buff *fp, *head = qp->q.fragments; 6081da177e4SLinus Torvalds int len; 6091da177e4SLinus Torvalds int ihlen; 6101706d587SHerbert Xu int err; 6111da177e4SLinus Torvalds 6121da177e4SLinus Torvalds ipq_kill(qp); 6131da177e4SLinus Torvalds 6141706d587SHerbert Xu /* Make the one we just received the head. */ 6151706d587SHerbert Xu if (prev) { 6161706d587SHerbert Xu head = prev->next; 6171706d587SHerbert Xu fp = skb_clone(head, GFP_ATOMIC); 6181706d587SHerbert Xu 6191706d587SHerbert Xu if (!fp) 6201706d587SHerbert Xu goto out_nomem; 6211706d587SHerbert Xu 6221706d587SHerbert Xu fp->next = head->next; 6231706d587SHerbert Xu prev->next = fp; 6241706d587SHerbert Xu 6255ab11c98SPavel Emelyanov skb_morph(head, qp->q.fragments); 6265ab11c98SPavel Emelyanov head->next = qp->q.fragments->next; 6271706d587SHerbert Xu 6285ab11c98SPavel Emelyanov kfree_skb(qp->q.fragments); 6295ab11c98SPavel Emelyanov qp->q.fragments = head; 6301706d587SHerbert Xu } 6311706d587SHerbert Xu 6321da177e4SLinus Torvalds BUG_TRAP(head != NULL); 6331da177e4SLinus Torvalds BUG_TRAP(FRAG_CB(head)->offset == 0); 6341da177e4SLinus Torvalds 6351da177e4SLinus Torvalds /* Allocate a new buffer for the datagram. */ 636c9bdd4b5SArnaldo Carvalho de Melo ihlen = ip_hdrlen(head); 6375ab11c98SPavel Emelyanov len = ihlen + qp->q.len; 6381da177e4SLinus Torvalds 6391706d587SHerbert Xu err = -E2BIG; 6401da177e4SLinus Torvalds if (len > 65535) 6411da177e4SLinus Torvalds goto out_oversize; 6421da177e4SLinus Torvalds 6431da177e4SLinus Torvalds /* Head of list must not be cloned. */ 6441706d587SHerbert Xu err = -ENOMEM; 6451da177e4SLinus Torvalds if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) 6461da177e4SLinus Torvalds goto out_nomem; 6471da177e4SLinus Torvalds 6481da177e4SLinus Torvalds /* If the first fragment is fragmented itself, we split 6491da177e4SLinus Torvalds * it to two chunks: the first with data and paged part 6501da177e4SLinus Torvalds * and the second, holding only fragments. */ 6511da177e4SLinus Torvalds if (skb_shinfo(head)->frag_list) { 6521da177e4SLinus Torvalds struct sk_buff *clone; 6531da177e4SLinus Torvalds int i, plen = 0; 6541da177e4SLinus Torvalds 6551da177e4SLinus Torvalds if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) 6561da177e4SLinus Torvalds goto out_nomem; 6571da177e4SLinus Torvalds clone->next = head->next; 6581da177e4SLinus Torvalds head->next = clone; 6591da177e4SLinus Torvalds skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 6601da177e4SLinus Torvalds skb_shinfo(head)->frag_list = NULL; 6611da177e4SLinus Torvalds for (i=0; i<skb_shinfo(head)->nr_frags; i++) 6621da177e4SLinus Torvalds plen += skb_shinfo(head)->frags[i].size; 6631da177e4SLinus Torvalds clone->len = clone->data_len = head->data_len - plen; 6641da177e4SLinus Torvalds head->data_len -= clone->len; 6651da177e4SLinus Torvalds head->len -= clone->len; 6661da177e4SLinus Torvalds clone->csum = 0; 6671da177e4SLinus Torvalds clone->ip_summed = head->ip_summed; 6687eb95156SPavel Emelyanov atomic_add(clone->truesize, &ip4_frags.mem); 6691da177e4SLinus Torvalds } 6701da177e4SLinus Torvalds 6711da177e4SLinus Torvalds skb_shinfo(head)->frag_list = head->next; 672d56f90a7SArnaldo Carvalho de Melo skb_push(head, head->data - skb_network_header(head)); 6737eb95156SPavel Emelyanov atomic_sub(head->truesize, &ip4_frags.mem); 6741da177e4SLinus Torvalds 6751da177e4SLinus Torvalds for (fp=head->next; fp; fp = fp->next) { 6761da177e4SLinus Torvalds head->data_len += fp->len; 6771da177e4SLinus Torvalds head->len += fp->len; 6781da177e4SLinus Torvalds if (head->ip_summed != fp->ip_summed) 6791da177e4SLinus Torvalds head->ip_summed = CHECKSUM_NONE; 68084fa7933SPatrick McHardy else if (head->ip_summed == CHECKSUM_COMPLETE) 6811da177e4SLinus Torvalds head->csum = csum_add(head->csum, fp->csum); 6821da177e4SLinus Torvalds head->truesize += fp->truesize; 6837eb95156SPavel Emelyanov atomic_sub(fp->truesize, &ip4_frags.mem); 6841da177e4SLinus Torvalds } 6851da177e4SLinus Torvalds 6861da177e4SLinus Torvalds head->next = NULL; 6871da177e4SLinus Torvalds head->dev = dev; 6885ab11c98SPavel Emelyanov head->tstamp = qp->q.stamp; 6891da177e4SLinus Torvalds 690eddc9ec5SArnaldo Carvalho de Melo iph = ip_hdr(head); 6911da177e4SLinus Torvalds iph->frag_off = 0; 6921da177e4SLinus Torvalds iph->tot_len = htons(len); 6931da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS); 6945ab11c98SPavel Emelyanov qp->q.fragments = NULL; 6951706d587SHerbert Xu return 0; 6961da177e4SLinus Torvalds 6971da177e4SLinus Torvalds out_nomem: 69864ce2073SPatrick McHardy LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing " 69964ce2073SPatrick McHardy "queue %p\n", qp); 7001da177e4SLinus Torvalds goto out_fail; 7011da177e4SLinus Torvalds out_oversize: 7021da177e4SLinus Torvalds if (net_ratelimit()) 7031da177e4SLinus Torvalds printk(KERN_INFO 7041da177e4SLinus Torvalds "Oversized IP packet from %d.%d.%d.%d.\n", 7051da177e4SLinus Torvalds NIPQUAD(qp->saddr)); 7061da177e4SLinus Torvalds out_fail: 7071da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 7081706d587SHerbert Xu return err; 7091da177e4SLinus Torvalds } 7101da177e4SLinus Torvalds 7111da177e4SLinus Torvalds /* Process an incoming IP datagram fragment. */ 712776c729eSHerbert Xu int ip_defrag(struct sk_buff *skb, u32 user) 7131da177e4SLinus Torvalds { 7141da177e4SLinus Torvalds struct ipq *qp; 7151da177e4SLinus Torvalds 7161da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS); 7171da177e4SLinus Torvalds 7181da177e4SLinus Torvalds /* Start by cleaning up the memory. */ 71904128f23SPavel Emelyanov if (atomic_read(&ip4_frags.mem) > ip4_frags_ctl.high_thresh) 7201da177e4SLinus Torvalds ip_evictor(); 7211da177e4SLinus Torvalds 7221da177e4SLinus Torvalds /* Lookup (or create) queue header */ 723eddc9ec5SArnaldo Carvalho de Melo if ((qp = ip_find(ip_hdr(skb), user)) != NULL) { 7241706d587SHerbert Xu int ret; 7251da177e4SLinus Torvalds 7265ab11c98SPavel Emelyanov spin_lock(&qp->q.lock); 7271da177e4SLinus Torvalds 7281706d587SHerbert Xu ret = ip_frag_queue(qp, skb); 7291da177e4SLinus Torvalds 7305ab11c98SPavel Emelyanov spin_unlock(&qp->q.lock); 7311da177e4SLinus Torvalds ipq_put(qp, NULL); 732776c729eSHerbert Xu return ret; 7331da177e4SLinus Torvalds } 7341da177e4SLinus Torvalds 7351da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 7361da177e4SLinus Torvalds kfree_skb(skb); 737776c729eSHerbert Xu return -ENOMEM; 7381da177e4SLinus Torvalds } 7391da177e4SLinus Torvalds 740b7aa0bf7SEric Dumazet void __init ipfrag_init(void) 7411da177e4SLinus Torvalds { 7427eb95156SPavel Emelyanov init_timer(&ip4_frags.secret_timer); 7437eb95156SPavel Emelyanov ip4_frags.secret_timer.function = ipfrag_secret_rebuild; 74404128f23SPavel Emelyanov ip4_frags.secret_timer.expires = jiffies + ip4_frags_ctl.secret_interval; 7457eb95156SPavel Emelyanov add_timer(&ip4_frags.secret_timer); 7461da177e4SLinus Torvalds 74704128f23SPavel Emelyanov ip4_frags.ctl = &ip4_frags_ctl; 7487eb95156SPavel Emelyanov inet_frags_init(&ip4_frags); 7491da177e4SLinus Torvalds } 7501da177e4SLinus Torvalds 7511da177e4SLinus Torvalds EXPORT_SYMBOL(ip_defrag); 752