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 251da177e4SLinus Torvalds #include <linux/config.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> 411da177e4SLinus Torvalds #include <linux/tcp.h> 421da177e4SLinus Torvalds #include <linux/udp.h> 431da177e4SLinus Torvalds #include <linux/inet.h> 441da177e4SLinus Torvalds #include <linux/netfilter_ipv4.h> 451da177e4SLinus Torvalds 461da177e4SLinus Torvalds /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 471da177e4SLinus Torvalds * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c 481da177e4SLinus Torvalds * as well. Or notify me, at least. --ANK 491da177e4SLinus Torvalds */ 501da177e4SLinus Torvalds 511da177e4SLinus Torvalds /* Fragment cache limits. We will commit 256K at one time. Should we 521da177e4SLinus Torvalds * cross that limit we will prune down to 192K. This should cope with 531da177e4SLinus Torvalds * even the most extreme cases without allowing an attacker to measurably 541da177e4SLinus Torvalds * harm machine performance. 551da177e4SLinus Torvalds */ 561da177e4SLinus Torvalds int sysctl_ipfrag_high_thresh = 256*1024; 571da177e4SLinus Torvalds int sysctl_ipfrag_low_thresh = 192*1024; 581da177e4SLinus Torvalds 591da177e4SLinus Torvalds /* Important NOTE! Fragment queue must be destroyed before MSL expires. 601da177e4SLinus Torvalds * RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL. 611da177e4SLinus Torvalds */ 621da177e4SLinus Torvalds int sysctl_ipfrag_time = IP_FRAG_TIME; 631da177e4SLinus Torvalds 641da177e4SLinus Torvalds struct ipfrag_skb_cb 651da177e4SLinus Torvalds { 661da177e4SLinus Torvalds struct inet_skb_parm h; 671da177e4SLinus Torvalds int offset; 681da177e4SLinus Torvalds }; 691da177e4SLinus Torvalds 701da177e4SLinus Torvalds #define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb)) 711da177e4SLinus Torvalds 721da177e4SLinus Torvalds /* Describe an entry in the "incomplete datagrams" queue. */ 731da177e4SLinus Torvalds struct ipq { 74e7c8a41eSYasuyuki Kozakai struct hlist_node list; 751da177e4SLinus Torvalds struct list_head lru_list; /* lru list member */ 761da177e4SLinus Torvalds u32 user; 771da177e4SLinus Torvalds u32 saddr; 781da177e4SLinus Torvalds u32 daddr; 791da177e4SLinus Torvalds u16 id; 801da177e4SLinus Torvalds u8 protocol; 811da177e4SLinus Torvalds u8 last_in; 821da177e4SLinus Torvalds #define COMPLETE 4 831da177e4SLinus Torvalds #define FIRST_IN 2 841da177e4SLinus Torvalds #define LAST_IN 1 851da177e4SLinus Torvalds 861da177e4SLinus Torvalds struct sk_buff *fragments; /* linked list of received fragments */ 871da177e4SLinus Torvalds int len; /* total length of original datagram */ 881da177e4SLinus Torvalds int meat; 891da177e4SLinus Torvalds spinlock_t lock; 901da177e4SLinus Torvalds atomic_t refcnt; 911da177e4SLinus Torvalds struct timer_list timer; /* when will this queue expire? */ 921da177e4SLinus Torvalds int iif; 931da177e4SLinus Torvalds struct timeval stamp; 941da177e4SLinus Torvalds }; 951da177e4SLinus Torvalds 961da177e4SLinus Torvalds /* Hash table. */ 971da177e4SLinus Torvalds 981da177e4SLinus Torvalds #define IPQ_HASHSZ 64 991da177e4SLinus Torvalds 1001da177e4SLinus Torvalds /* Per-bucket lock is easy to add now. */ 101e7c8a41eSYasuyuki Kozakai static struct hlist_head ipq_hash[IPQ_HASHSZ]; 1021da177e4SLinus Torvalds static DEFINE_RWLOCK(ipfrag_lock); 1031da177e4SLinus Torvalds static u32 ipfrag_hash_rnd; 1041da177e4SLinus Torvalds static LIST_HEAD(ipq_lru_list); 1051da177e4SLinus Torvalds int ip_frag_nqueues = 0; 1061da177e4SLinus Torvalds 1071da177e4SLinus Torvalds static __inline__ void __ipq_unlink(struct ipq *qp) 1081da177e4SLinus Torvalds { 109e7c8a41eSYasuyuki Kozakai hlist_del(&qp->list); 1101da177e4SLinus Torvalds list_del(&qp->lru_list); 1111da177e4SLinus Torvalds ip_frag_nqueues--; 1121da177e4SLinus Torvalds } 1131da177e4SLinus Torvalds 1141da177e4SLinus Torvalds static __inline__ void ipq_unlink(struct ipq *ipq) 1151da177e4SLinus Torvalds { 1161da177e4SLinus Torvalds write_lock(&ipfrag_lock); 1171da177e4SLinus Torvalds __ipq_unlink(ipq); 1181da177e4SLinus Torvalds write_unlock(&ipfrag_lock); 1191da177e4SLinus Torvalds } 1201da177e4SLinus Torvalds 1211da177e4SLinus Torvalds static unsigned int ipqhashfn(u16 id, u32 saddr, u32 daddr, u8 prot) 1221da177e4SLinus Torvalds { 1231da177e4SLinus Torvalds return jhash_3words((u32)id << 16 | prot, saddr, daddr, 1241da177e4SLinus Torvalds ipfrag_hash_rnd) & (IPQ_HASHSZ - 1); 1251da177e4SLinus Torvalds } 1261da177e4SLinus Torvalds 1271da177e4SLinus Torvalds static struct timer_list ipfrag_secret_timer; 1281da177e4SLinus Torvalds int sysctl_ipfrag_secret_interval = 10 * 60 * HZ; 1291da177e4SLinus Torvalds 1301da177e4SLinus Torvalds static void ipfrag_secret_rebuild(unsigned long dummy) 1311da177e4SLinus Torvalds { 1321da177e4SLinus Torvalds unsigned long now = jiffies; 1331da177e4SLinus Torvalds int i; 1341da177e4SLinus Torvalds 1351da177e4SLinus Torvalds write_lock(&ipfrag_lock); 1361da177e4SLinus Torvalds get_random_bytes(&ipfrag_hash_rnd, sizeof(u32)); 1371da177e4SLinus Torvalds for (i = 0; i < IPQ_HASHSZ; i++) { 1381da177e4SLinus Torvalds struct ipq *q; 139e7c8a41eSYasuyuki Kozakai struct hlist_node *p, *n; 1401da177e4SLinus Torvalds 141e7c8a41eSYasuyuki Kozakai hlist_for_each_entry_safe(q, p, n, &ipq_hash[i], list) { 1421da177e4SLinus Torvalds unsigned int hval = ipqhashfn(q->id, q->saddr, 1431da177e4SLinus Torvalds q->daddr, q->protocol); 1441da177e4SLinus Torvalds 1451da177e4SLinus Torvalds if (hval != i) { 146e7c8a41eSYasuyuki Kozakai hlist_del(&q->list); 1471da177e4SLinus Torvalds 1481da177e4SLinus Torvalds /* Relink to new hash chain. */ 149e7c8a41eSYasuyuki Kozakai hlist_add_head(&q->list, &ipq_hash[hval]); 1501da177e4SLinus Torvalds } 1511da177e4SLinus Torvalds } 1521da177e4SLinus Torvalds } 1531da177e4SLinus Torvalds write_unlock(&ipfrag_lock); 1541da177e4SLinus Torvalds 1551da177e4SLinus Torvalds mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval); 1561da177e4SLinus Torvalds } 1571da177e4SLinus Torvalds 1581da177e4SLinus Torvalds atomic_t ip_frag_mem = ATOMIC_INIT(0); /* Memory used for fragments */ 1591da177e4SLinus Torvalds 1601da177e4SLinus Torvalds /* Memory Tracking Functions. */ 1611da177e4SLinus Torvalds static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work) 1621da177e4SLinus Torvalds { 1631da177e4SLinus Torvalds if (work) 1641da177e4SLinus Torvalds *work -= skb->truesize; 1651da177e4SLinus Torvalds atomic_sub(skb->truesize, &ip_frag_mem); 1661da177e4SLinus Torvalds kfree_skb(skb); 1671da177e4SLinus Torvalds } 1681da177e4SLinus Torvalds 1691da177e4SLinus Torvalds static __inline__ void frag_free_queue(struct ipq *qp, int *work) 1701da177e4SLinus Torvalds { 1711da177e4SLinus Torvalds if (work) 1721da177e4SLinus Torvalds *work -= sizeof(struct ipq); 1731da177e4SLinus Torvalds atomic_sub(sizeof(struct ipq), &ip_frag_mem); 1741da177e4SLinus Torvalds kfree(qp); 1751da177e4SLinus Torvalds } 1761da177e4SLinus Torvalds 1771da177e4SLinus Torvalds static __inline__ struct ipq *frag_alloc_queue(void) 1781da177e4SLinus Torvalds { 1791da177e4SLinus Torvalds struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC); 1801da177e4SLinus Torvalds 1811da177e4SLinus Torvalds if(!qp) 1821da177e4SLinus Torvalds return NULL; 1831da177e4SLinus Torvalds atomic_add(sizeof(struct ipq), &ip_frag_mem); 1841da177e4SLinus Torvalds return qp; 1851da177e4SLinus Torvalds } 1861da177e4SLinus Torvalds 1871da177e4SLinus Torvalds 1881da177e4SLinus Torvalds /* Destruction primitives. */ 1891da177e4SLinus Torvalds 1901da177e4SLinus Torvalds /* Complete destruction of ipq. */ 1911da177e4SLinus Torvalds static void ip_frag_destroy(struct ipq *qp, int *work) 1921da177e4SLinus Torvalds { 1931da177e4SLinus Torvalds struct sk_buff *fp; 1941da177e4SLinus Torvalds 1951da177e4SLinus Torvalds BUG_TRAP(qp->last_in&COMPLETE); 1961da177e4SLinus Torvalds BUG_TRAP(del_timer(&qp->timer) == 0); 1971da177e4SLinus Torvalds 1981da177e4SLinus Torvalds /* Release all fragment data. */ 1991da177e4SLinus Torvalds fp = qp->fragments; 2001da177e4SLinus Torvalds while (fp) { 2011da177e4SLinus Torvalds struct sk_buff *xp = fp->next; 2021da177e4SLinus Torvalds 2031da177e4SLinus Torvalds frag_kfree_skb(fp, work); 2041da177e4SLinus Torvalds fp = xp; 2051da177e4SLinus Torvalds } 2061da177e4SLinus Torvalds 2071da177e4SLinus Torvalds /* Finally, release the queue descriptor itself. */ 2081da177e4SLinus Torvalds frag_free_queue(qp, work); 2091da177e4SLinus Torvalds } 2101da177e4SLinus Torvalds 2111da177e4SLinus Torvalds static __inline__ void ipq_put(struct ipq *ipq, int *work) 2121da177e4SLinus Torvalds { 2131da177e4SLinus Torvalds if (atomic_dec_and_test(&ipq->refcnt)) 2141da177e4SLinus Torvalds ip_frag_destroy(ipq, work); 2151da177e4SLinus Torvalds } 2161da177e4SLinus Torvalds 2171da177e4SLinus Torvalds /* Kill ipq entry. It is not destroyed immediately, 2181da177e4SLinus Torvalds * because caller (and someone more) holds reference count. 2191da177e4SLinus Torvalds */ 2201da177e4SLinus Torvalds static void ipq_kill(struct ipq *ipq) 2211da177e4SLinus Torvalds { 2221da177e4SLinus Torvalds if (del_timer(&ipq->timer)) 2231da177e4SLinus Torvalds atomic_dec(&ipq->refcnt); 2241da177e4SLinus Torvalds 2251da177e4SLinus Torvalds if (!(ipq->last_in & COMPLETE)) { 2261da177e4SLinus Torvalds ipq_unlink(ipq); 2271da177e4SLinus Torvalds atomic_dec(&ipq->refcnt); 2281da177e4SLinus Torvalds ipq->last_in |= COMPLETE; 2291da177e4SLinus Torvalds } 2301da177e4SLinus Torvalds } 2311da177e4SLinus Torvalds 2321da177e4SLinus Torvalds /* Memory limiting on fragments. Evictor trashes the oldest 2331da177e4SLinus Torvalds * fragment queue until we are back under the threshold. 2341da177e4SLinus Torvalds */ 2351da177e4SLinus Torvalds static void ip_evictor(void) 2361da177e4SLinus Torvalds { 2371da177e4SLinus Torvalds struct ipq *qp; 2381da177e4SLinus Torvalds struct list_head *tmp; 2391da177e4SLinus Torvalds int work; 2401da177e4SLinus Torvalds 2411da177e4SLinus Torvalds work = atomic_read(&ip_frag_mem) - sysctl_ipfrag_low_thresh; 2421da177e4SLinus Torvalds if (work <= 0) 2431da177e4SLinus Torvalds return; 2441da177e4SLinus Torvalds 2451da177e4SLinus Torvalds while (work > 0) { 2461da177e4SLinus Torvalds read_lock(&ipfrag_lock); 2471da177e4SLinus Torvalds if (list_empty(&ipq_lru_list)) { 2481da177e4SLinus Torvalds read_unlock(&ipfrag_lock); 2491da177e4SLinus Torvalds return; 2501da177e4SLinus Torvalds } 2511da177e4SLinus Torvalds tmp = ipq_lru_list.next; 2521da177e4SLinus Torvalds qp = list_entry(tmp, struct ipq, lru_list); 2531da177e4SLinus Torvalds atomic_inc(&qp->refcnt); 2541da177e4SLinus Torvalds read_unlock(&ipfrag_lock); 2551da177e4SLinus Torvalds 2561da177e4SLinus Torvalds spin_lock(&qp->lock); 2571da177e4SLinus Torvalds if (!(qp->last_in&COMPLETE)) 2581da177e4SLinus Torvalds ipq_kill(qp); 2591da177e4SLinus Torvalds spin_unlock(&qp->lock); 2601da177e4SLinus Torvalds 2611da177e4SLinus Torvalds ipq_put(qp, &work); 2621da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 2631da177e4SLinus Torvalds } 2641da177e4SLinus Torvalds } 2651da177e4SLinus Torvalds 2661da177e4SLinus Torvalds /* 2671da177e4SLinus Torvalds * Oops, a fragment queue timed out. Kill it and send an ICMP reply. 2681da177e4SLinus Torvalds */ 2691da177e4SLinus Torvalds static void ip_expire(unsigned long arg) 2701da177e4SLinus Torvalds { 2711da177e4SLinus Torvalds struct ipq *qp = (struct ipq *) arg; 2721da177e4SLinus Torvalds 2731da177e4SLinus Torvalds spin_lock(&qp->lock); 2741da177e4SLinus Torvalds 2751da177e4SLinus Torvalds if (qp->last_in & COMPLETE) 2761da177e4SLinus Torvalds goto out; 2771da177e4SLinus Torvalds 2781da177e4SLinus Torvalds ipq_kill(qp); 2791da177e4SLinus Torvalds 2801da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT); 2811da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 2821da177e4SLinus Torvalds 2831da177e4SLinus Torvalds if ((qp->last_in&FIRST_IN) && qp->fragments != NULL) { 2841da177e4SLinus Torvalds struct sk_buff *head = qp->fragments; 2851da177e4SLinus Torvalds /* Send an ICMP "Fragment Reassembly Timeout" message. */ 2861da177e4SLinus Torvalds if ((head->dev = dev_get_by_index(qp->iif)) != NULL) { 2871da177e4SLinus Torvalds icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); 2881da177e4SLinus Torvalds dev_put(head->dev); 2891da177e4SLinus Torvalds } 2901da177e4SLinus Torvalds } 2911da177e4SLinus Torvalds out: 2921da177e4SLinus Torvalds spin_unlock(&qp->lock); 2931da177e4SLinus Torvalds ipq_put(qp, NULL); 2941da177e4SLinus Torvalds } 2951da177e4SLinus Torvalds 2961da177e4SLinus Torvalds /* Creation primitives. */ 2971da177e4SLinus Torvalds 2981da177e4SLinus Torvalds static struct ipq *ip_frag_intern(unsigned int hash, struct ipq *qp_in) 2991da177e4SLinus Torvalds { 3001da177e4SLinus Torvalds struct ipq *qp; 301e7c8a41eSYasuyuki Kozakai #ifdef CONFIG_SMP 302e7c8a41eSYasuyuki Kozakai struct hlist_node *n; 303e7c8a41eSYasuyuki Kozakai #endif 3041da177e4SLinus Torvalds write_lock(&ipfrag_lock); 3051da177e4SLinus Torvalds #ifdef CONFIG_SMP 3061da177e4SLinus Torvalds /* With SMP race we have to recheck hash table, because 3071da177e4SLinus Torvalds * such entry could be created on other cpu, while we 3081da177e4SLinus Torvalds * promoted read lock to write lock. 3091da177e4SLinus Torvalds */ 310e7c8a41eSYasuyuki Kozakai hlist_for_each_entry(qp, n, &ipq_hash[hash], list) { 3111da177e4SLinus Torvalds if(qp->id == qp_in->id && 3121da177e4SLinus Torvalds qp->saddr == qp_in->saddr && 3131da177e4SLinus Torvalds qp->daddr == qp_in->daddr && 3141da177e4SLinus Torvalds qp->protocol == qp_in->protocol && 3151da177e4SLinus Torvalds qp->user == qp_in->user) { 3161da177e4SLinus Torvalds atomic_inc(&qp->refcnt); 3171da177e4SLinus Torvalds write_unlock(&ipfrag_lock); 3181da177e4SLinus Torvalds qp_in->last_in |= COMPLETE; 3191da177e4SLinus Torvalds ipq_put(qp_in, NULL); 3201da177e4SLinus Torvalds return qp; 3211da177e4SLinus Torvalds } 3221da177e4SLinus Torvalds } 3231da177e4SLinus Torvalds #endif 3241da177e4SLinus Torvalds qp = qp_in; 3251da177e4SLinus Torvalds 3261da177e4SLinus Torvalds if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time)) 3271da177e4SLinus Torvalds atomic_inc(&qp->refcnt); 3281da177e4SLinus Torvalds 3291da177e4SLinus Torvalds atomic_inc(&qp->refcnt); 330e7c8a41eSYasuyuki Kozakai hlist_add_head(&qp->list, &ipq_hash[hash]); 3311da177e4SLinus Torvalds INIT_LIST_HEAD(&qp->lru_list); 3321da177e4SLinus Torvalds list_add_tail(&qp->lru_list, &ipq_lru_list); 3331da177e4SLinus Torvalds ip_frag_nqueues++; 3341da177e4SLinus Torvalds write_unlock(&ipfrag_lock); 3351da177e4SLinus Torvalds return qp; 3361da177e4SLinus Torvalds } 3371da177e4SLinus Torvalds 3381da177e4SLinus Torvalds /* Add an entry to the 'ipq' queue for a newly received IP datagram. */ 3391da177e4SLinus Torvalds static struct ipq *ip_frag_create(unsigned hash, struct iphdr *iph, u32 user) 3401da177e4SLinus Torvalds { 3411da177e4SLinus Torvalds struct ipq *qp; 3421da177e4SLinus Torvalds 3431da177e4SLinus Torvalds if ((qp = frag_alloc_queue()) == NULL) 3441da177e4SLinus Torvalds goto out_nomem; 3451da177e4SLinus Torvalds 3461da177e4SLinus Torvalds qp->protocol = iph->protocol; 3471da177e4SLinus Torvalds qp->last_in = 0; 3481da177e4SLinus Torvalds qp->id = iph->id; 3491da177e4SLinus Torvalds qp->saddr = iph->saddr; 3501da177e4SLinus Torvalds qp->daddr = iph->daddr; 3511da177e4SLinus Torvalds qp->user = user; 3521da177e4SLinus Torvalds qp->len = 0; 3531da177e4SLinus Torvalds qp->meat = 0; 3541da177e4SLinus Torvalds qp->fragments = NULL; 3551da177e4SLinus Torvalds qp->iif = 0; 3561da177e4SLinus Torvalds 3571da177e4SLinus Torvalds /* Initialize a timer for this entry. */ 3581da177e4SLinus Torvalds init_timer(&qp->timer); 3591da177e4SLinus Torvalds qp->timer.data = (unsigned long) qp; /* pointer to queue */ 3601da177e4SLinus Torvalds qp->timer.function = ip_expire; /* expire function */ 3611da177e4SLinus Torvalds spin_lock_init(&qp->lock); 3621da177e4SLinus Torvalds atomic_set(&qp->refcnt, 1); 3631da177e4SLinus Torvalds 3641da177e4SLinus Torvalds return ip_frag_intern(hash, qp); 3651da177e4SLinus Torvalds 3661da177e4SLinus Torvalds out_nomem: 36764ce2073SPatrick McHardy LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n"); 3681da177e4SLinus Torvalds return NULL; 3691da177e4SLinus Torvalds } 3701da177e4SLinus Torvalds 3711da177e4SLinus Torvalds /* Find the correct entry in the "incomplete datagrams" queue for 3721da177e4SLinus Torvalds * this IP datagram, and create new one, if nothing is found. 3731da177e4SLinus Torvalds */ 3741da177e4SLinus Torvalds static inline struct ipq *ip_find(struct iphdr *iph, u32 user) 3751da177e4SLinus Torvalds { 3761da177e4SLinus Torvalds __u16 id = iph->id; 3771da177e4SLinus Torvalds __u32 saddr = iph->saddr; 3781da177e4SLinus Torvalds __u32 daddr = iph->daddr; 3791da177e4SLinus Torvalds __u8 protocol = iph->protocol; 3801da177e4SLinus Torvalds unsigned int hash = ipqhashfn(id, saddr, daddr, protocol); 3811da177e4SLinus Torvalds struct ipq *qp; 382e7c8a41eSYasuyuki Kozakai struct hlist_node *n; 3831da177e4SLinus Torvalds 3841da177e4SLinus Torvalds read_lock(&ipfrag_lock); 385e7c8a41eSYasuyuki Kozakai hlist_for_each_entry(qp, n, &ipq_hash[hash], list) { 3861da177e4SLinus Torvalds if(qp->id == id && 3871da177e4SLinus Torvalds qp->saddr == saddr && 3881da177e4SLinus Torvalds qp->daddr == daddr && 3891da177e4SLinus Torvalds qp->protocol == protocol && 3901da177e4SLinus Torvalds qp->user == user) { 3911da177e4SLinus Torvalds atomic_inc(&qp->refcnt); 3921da177e4SLinus Torvalds read_unlock(&ipfrag_lock); 3931da177e4SLinus Torvalds return qp; 3941da177e4SLinus Torvalds } 3951da177e4SLinus Torvalds } 3961da177e4SLinus Torvalds read_unlock(&ipfrag_lock); 3971da177e4SLinus Torvalds 3981da177e4SLinus Torvalds return ip_frag_create(hash, iph, user); 3991da177e4SLinus Torvalds } 4001da177e4SLinus Torvalds 4011da177e4SLinus Torvalds /* Add new segment to existing queue. */ 4021da177e4SLinus Torvalds static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb) 4031da177e4SLinus Torvalds { 4041da177e4SLinus Torvalds struct sk_buff *prev, *next; 4051da177e4SLinus Torvalds int flags, offset; 4061da177e4SLinus Torvalds int ihl, end; 4071da177e4SLinus Torvalds 4081da177e4SLinus Torvalds if (qp->last_in & COMPLETE) 4091da177e4SLinus Torvalds goto err; 4101da177e4SLinus Torvalds 4111da177e4SLinus Torvalds offset = ntohs(skb->nh.iph->frag_off); 4121da177e4SLinus Torvalds flags = offset & ~IP_OFFSET; 4131da177e4SLinus Torvalds offset &= IP_OFFSET; 4141da177e4SLinus Torvalds offset <<= 3; /* offset is in 8-byte chunks */ 4151da177e4SLinus Torvalds ihl = skb->nh.iph->ihl * 4; 4161da177e4SLinus Torvalds 4171da177e4SLinus Torvalds /* Determine the position of this fragment. */ 4181da177e4SLinus Torvalds end = offset + skb->len - ihl; 4191da177e4SLinus Torvalds 4201da177e4SLinus Torvalds /* Is this the final fragment? */ 4211da177e4SLinus Torvalds if ((flags & IP_MF) == 0) { 4221da177e4SLinus Torvalds /* If we already have some bits beyond end 4231da177e4SLinus Torvalds * or have different end, the segment is corrrupted. 4241da177e4SLinus Torvalds */ 4251da177e4SLinus Torvalds if (end < qp->len || 4261da177e4SLinus Torvalds ((qp->last_in & LAST_IN) && end != qp->len)) 4271da177e4SLinus Torvalds goto err; 4281da177e4SLinus Torvalds qp->last_in |= LAST_IN; 4291da177e4SLinus Torvalds qp->len = end; 4301da177e4SLinus Torvalds } else { 4311da177e4SLinus Torvalds if (end&7) { 4321da177e4SLinus Torvalds end &= ~7; 4331da177e4SLinus Torvalds if (skb->ip_summed != CHECKSUM_UNNECESSARY) 4341da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 4351da177e4SLinus Torvalds } 4361da177e4SLinus Torvalds if (end > qp->len) { 4371da177e4SLinus Torvalds /* Some bits beyond end -> corruption. */ 4381da177e4SLinus Torvalds if (qp->last_in & LAST_IN) 4391da177e4SLinus Torvalds goto err; 4401da177e4SLinus Torvalds qp->len = end; 4411da177e4SLinus Torvalds } 4421da177e4SLinus Torvalds } 4431da177e4SLinus Torvalds if (end == offset) 4441da177e4SLinus Torvalds goto err; 4451da177e4SLinus Torvalds 4461da177e4SLinus Torvalds if (pskb_pull(skb, ihl) == NULL) 4471da177e4SLinus Torvalds goto err; 44848bc41a4SStephen Hemminger if (pskb_trim_rcsum(skb, end-offset)) 4491da177e4SLinus Torvalds goto err; 4501da177e4SLinus Torvalds 4511da177e4SLinus Torvalds /* Find out which fragments are in front and at the back of us 4521da177e4SLinus Torvalds * in the chain of fragments so far. We must know where to put 4531da177e4SLinus Torvalds * this fragment, right? 4541da177e4SLinus Torvalds */ 4551da177e4SLinus Torvalds prev = NULL; 4561da177e4SLinus Torvalds for(next = qp->fragments; next != NULL; next = next->next) { 4571da177e4SLinus Torvalds if (FRAG_CB(next)->offset >= offset) 4581da177e4SLinus Torvalds break; /* bingo! */ 4591da177e4SLinus Torvalds prev = next; 4601da177e4SLinus Torvalds } 4611da177e4SLinus Torvalds 4621da177e4SLinus Torvalds /* We found where to put this one. Check for overlap with 4631da177e4SLinus Torvalds * preceding fragment, and, if needed, align things so that 4641da177e4SLinus Torvalds * any overlaps are eliminated. 4651da177e4SLinus Torvalds */ 4661da177e4SLinus Torvalds if (prev) { 4671da177e4SLinus Torvalds int i = (FRAG_CB(prev)->offset + prev->len) - offset; 4681da177e4SLinus Torvalds 4691da177e4SLinus Torvalds if (i > 0) { 4701da177e4SLinus Torvalds offset += i; 4711da177e4SLinus Torvalds if (end <= offset) 4721da177e4SLinus Torvalds goto err; 4731da177e4SLinus Torvalds if (!pskb_pull(skb, i)) 4741da177e4SLinus Torvalds goto err; 4751da177e4SLinus Torvalds if (skb->ip_summed != CHECKSUM_UNNECESSARY) 4761da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 4771da177e4SLinus Torvalds } 4781da177e4SLinus Torvalds } 4791da177e4SLinus Torvalds 4801da177e4SLinus Torvalds while (next && FRAG_CB(next)->offset < end) { 4811da177e4SLinus Torvalds int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */ 4821da177e4SLinus Torvalds 4831da177e4SLinus Torvalds if (i < next->len) { 4841da177e4SLinus Torvalds /* Eat head of the next overlapped fragment 4851da177e4SLinus Torvalds * and leave the loop. The next ones cannot overlap. 4861da177e4SLinus Torvalds */ 4871da177e4SLinus Torvalds if (!pskb_pull(next, i)) 4881da177e4SLinus Torvalds goto err; 4891da177e4SLinus Torvalds FRAG_CB(next)->offset += i; 4901da177e4SLinus Torvalds qp->meat -= i; 4911da177e4SLinus Torvalds if (next->ip_summed != CHECKSUM_UNNECESSARY) 4921da177e4SLinus Torvalds next->ip_summed = CHECKSUM_NONE; 4931da177e4SLinus Torvalds break; 4941da177e4SLinus Torvalds } else { 4951da177e4SLinus Torvalds struct sk_buff *free_it = next; 4961da177e4SLinus Torvalds 4971da177e4SLinus Torvalds /* Old fragmnet is completely overridden with 4981da177e4SLinus Torvalds * new one drop it. 4991da177e4SLinus Torvalds */ 5001da177e4SLinus Torvalds next = next->next; 5011da177e4SLinus Torvalds 5021da177e4SLinus Torvalds if (prev) 5031da177e4SLinus Torvalds prev->next = next; 5041da177e4SLinus Torvalds else 5051da177e4SLinus Torvalds qp->fragments = next; 5061da177e4SLinus Torvalds 5071da177e4SLinus Torvalds qp->meat -= free_it->len; 5081da177e4SLinus Torvalds frag_kfree_skb(free_it, NULL); 5091da177e4SLinus Torvalds } 5101da177e4SLinus Torvalds } 5111da177e4SLinus Torvalds 5121da177e4SLinus Torvalds FRAG_CB(skb)->offset = offset; 5131da177e4SLinus Torvalds 5141da177e4SLinus Torvalds /* Insert this fragment in the chain of fragments. */ 5151da177e4SLinus Torvalds skb->next = next; 5161da177e4SLinus Torvalds if (prev) 5171da177e4SLinus Torvalds prev->next = skb; 5181da177e4SLinus Torvalds else 5191da177e4SLinus Torvalds qp->fragments = skb; 5201da177e4SLinus Torvalds 5211da177e4SLinus Torvalds if (skb->dev) 5221da177e4SLinus Torvalds qp->iif = skb->dev->ifindex; 5231da177e4SLinus Torvalds skb->dev = NULL; 524a61bbcf2SPatrick McHardy skb_get_timestamp(skb, &qp->stamp); 5251da177e4SLinus Torvalds qp->meat += skb->len; 5261da177e4SLinus Torvalds atomic_add(skb->truesize, &ip_frag_mem); 5271da177e4SLinus Torvalds if (offset == 0) 5281da177e4SLinus Torvalds qp->last_in |= FIRST_IN; 5291da177e4SLinus Torvalds 5301da177e4SLinus Torvalds write_lock(&ipfrag_lock); 5311da177e4SLinus Torvalds list_move_tail(&qp->lru_list, &ipq_lru_list); 5321da177e4SLinus Torvalds write_unlock(&ipfrag_lock); 5331da177e4SLinus Torvalds 5341da177e4SLinus Torvalds return; 5351da177e4SLinus Torvalds 5361da177e4SLinus Torvalds err: 5371da177e4SLinus Torvalds kfree_skb(skb); 5381da177e4SLinus Torvalds } 5391da177e4SLinus Torvalds 5401da177e4SLinus Torvalds 5411da177e4SLinus Torvalds /* Build a new IP datagram from all its fragments. */ 5421da177e4SLinus Torvalds 5431da177e4SLinus Torvalds static struct sk_buff *ip_frag_reasm(struct ipq *qp, struct net_device *dev) 5441da177e4SLinus Torvalds { 5451da177e4SLinus Torvalds struct iphdr *iph; 5461da177e4SLinus Torvalds struct sk_buff *fp, *head = qp->fragments; 5471da177e4SLinus Torvalds int len; 5481da177e4SLinus Torvalds int ihlen; 5491da177e4SLinus Torvalds 5501da177e4SLinus Torvalds ipq_kill(qp); 5511da177e4SLinus Torvalds 5521da177e4SLinus Torvalds BUG_TRAP(head != NULL); 5531da177e4SLinus Torvalds BUG_TRAP(FRAG_CB(head)->offset == 0); 5541da177e4SLinus Torvalds 5551da177e4SLinus Torvalds /* Allocate a new buffer for the datagram. */ 5561da177e4SLinus Torvalds ihlen = head->nh.iph->ihl*4; 5571da177e4SLinus Torvalds len = ihlen + qp->len; 5581da177e4SLinus Torvalds 5591da177e4SLinus Torvalds if(len > 65535) 5601da177e4SLinus Torvalds goto out_oversize; 5611da177e4SLinus Torvalds 5621da177e4SLinus Torvalds /* Head of list must not be cloned. */ 5631da177e4SLinus Torvalds if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) 5641da177e4SLinus Torvalds goto out_nomem; 5651da177e4SLinus Torvalds 5661da177e4SLinus Torvalds /* If the first fragment is fragmented itself, we split 5671da177e4SLinus Torvalds * it to two chunks: the first with data and paged part 5681da177e4SLinus Torvalds * and the second, holding only fragments. */ 5691da177e4SLinus Torvalds if (skb_shinfo(head)->frag_list) { 5701da177e4SLinus Torvalds struct sk_buff *clone; 5711da177e4SLinus Torvalds int i, plen = 0; 5721da177e4SLinus Torvalds 5731da177e4SLinus Torvalds if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL) 5741da177e4SLinus Torvalds goto out_nomem; 5751da177e4SLinus Torvalds clone->next = head->next; 5761da177e4SLinus Torvalds head->next = clone; 5771da177e4SLinus Torvalds skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list; 5781da177e4SLinus Torvalds skb_shinfo(head)->frag_list = NULL; 5791da177e4SLinus Torvalds for (i=0; i<skb_shinfo(head)->nr_frags; i++) 5801da177e4SLinus Torvalds plen += skb_shinfo(head)->frags[i].size; 5811da177e4SLinus Torvalds clone->len = clone->data_len = head->data_len - plen; 5821da177e4SLinus Torvalds head->data_len -= clone->len; 5831da177e4SLinus Torvalds head->len -= clone->len; 5841da177e4SLinus Torvalds clone->csum = 0; 5851da177e4SLinus Torvalds clone->ip_summed = head->ip_summed; 5861da177e4SLinus Torvalds atomic_add(clone->truesize, &ip_frag_mem); 5871da177e4SLinus Torvalds } 5881da177e4SLinus Torvalds 5891da177e4SLinus Torvalds skb_shinfo(head)->frag_list = head->next; 5901da177e4SLinus Torvalds skb_push(head, head->data - head->nh.raw); 5911da177e4SLinus Torvalds atomic_sub(head->truesize, &ip_frag_mem); 5921da177e4SLinus Torvalds 5931da177e4SLinus Torvalds for (fp=head->next; fp; fp = fp->next) { 5941da177e4SLinus Torvalds head->data_len += fp->len; 5951da177e4SLinus Torvalds head->len += fp->len; 5961da177e4SLinus Torvalds if (head->ip_summed != fp->ip_summed) 5971da177e4SLinus Torvalds head->ip_summed = CHECKSUM_NONE; 5981da177e4SLinus Torvalds else if (head->ip_summed == CHECKSUM_HW) 5991da177e4SLinus Torvalds head->csum = csum_add(head->csum, fp->csum); 6001da177e4SLinus Torvalds head->truesize += fp->truesize; 6011da177e4SLinus Torvalds atomic_sub(fp->truesize, &ip_frag_mem); 6021da177e4SLinus Torvalds } 6031da177e4SLinus Torvalds 6041da177e4SLinus Torvalds head->next = NULL; 6051da177e4SLinus Torvalds head->dev = dev; 606a61bbcf2SPatrick McHardy skb_set_timestamp(head, &qp->stamp); 6071da177e4SLinus Torvalds 6081da177e4SLinus Torvalds iph = head->nh.iph; 6091da177e4SLinus Torvalds iph->frag_off = 0; 6101da177e4SLinus Torvalds iph->tot_len = htons(len); 6111da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS); 6121da177e4SLinus Torvalds qp->fragments = NULL; 6131da177e4SLinus Torvalds return head; 6141da177e4SLinus Torvalds 6151da177e4SLinus Torvalds out_nomem: 61664ce2073SPatrick McHardy LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing " 61764ce2073SPatrick McHardy "queue %p\n", qp); 6181da177e4SLinus Torvalds goto out_fail; 6191da177e4SLinus Torvalds out_oversize: 6201da177e4SLinus Torvalds if (net_ratelimit()) 6211da177e4SLinus Torvalds printk(KERN_INFO 6221da177e4SLinus Torvalds "Oversized IP packet from %d.%d.%d.%d.\n", 6231da177e4SLinus Torvalds NIPQUAD(qp->saddr)); 6241da177e4SLinus Torvalds out_fail: 6251da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 6261da177e4SLinus Torvalds return NULL; 6271da177e4SLinus Torvalds } 6281da177e4SLinus Torvalds 6291da177e4SLinus Torvalds /* Process an incoming IP datagram fragment. */ 6301da177e4SLinus Torvalds struct sk_buff *ip_defrag(struct sk_buff *skb, u32 user) 6311da177e4SLinus Torvalds { 6321da177e4SLinus Torvalds struct iphdr *iph = skb->nh.iph; 6331da177e4SLinus Torvalds struct ipq *qp; 6341da177e4SLinus Torvalds struct net_device *dev; 6351da177e4SLinus Torvalds 6361da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS); 6371da177e4SLinus Torvalds 6381da177e4SLinus Torvalds /* Start by cleaning up the memory. */ 6391da177e4SLinus Torvalds if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh) 6401da177e4SLinus Torvalds ip_evictor(); 6411da177e4SLinus Torvalds 6421da177e4SLinus Torvalds dev = skb->dev; 6431da177e4SLinus Torvalds 6441da177e4SLinus Torvalds /* Lookup (or create) queue header */ 6451da177e4SLinus Torvalds if ((qp = ip_find(iph, user)) != NULL) { 6461da177e4SLinus Torvalds struct sk_buff *ret = NULL; 6471da177e4SLinus Torvalds 6481da177e4SLinus Torvalds spin_lock(&qp->lock); 6491da177e4SLinus Torvalds 6501da177e4SLinus Torvalds ip_frag_queue(qp, skb); 6511da177e4SLinus Torvalds 6521da177e4SLinus Torvalds if (qp->last_in == (FIRST_IN|LAST_IN) && 6531da177e4SLinus Torvalds qp->meat == qp->len) 6541da177e4SLinus Torvalds ret = ip_frag_reasm(qp, dev); 6551da177e4SLinus Torvalds 6561da177e4SLinus Torvalds spin_unlock(&qp->lock); 6571da177e4SLinus Torvalds ipq_put(qp, NULL); 6581da177e4SLinus Torvalds return ret; 6591da177e4SLinus Torvalds } 6601da177e4SLinus Torvalds 6611da177e4SLinus Torvalds IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS); 6621da177e4SLinus Torvalds kfree_skb(skb); 6631da177e4SLinus Torvalds return NULL; 6641da177e4SLinus Torvalds } 6651da177e4SLinus Torvalds 6661da177e4SLinus Torvalds void ipfrag_init(void) 6671da177e4SLinus Torvalds { 6681da177e4SLinus Torvalds ipfrag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^ 6691da177e4SLinus Torvalds (jiffies ^ (jiffies >> 6))); 6701da177e4SLinus Torvalds 6711da177e4SLinus Torvalds init_timer(&ipfrag_secret_timer); 6721da177e4SLinus Torvalds ipfrag_secret_timer.function = ipfrag_secret_rebuild; 6731da177e4SLinus Torvalds ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval; 6741da177e4SLinus Torvalds add_timer(&ipfrag_secret_timer); 6751da177e4SLinus Torvalds } 6761da177e4SLinus Torvalds 6771da177e4SLinus Torvalds EXPORT_SYMBOL(ip_defrag); 678