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eddc9ec53b
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
748 lines
17 KiB
C
748 lines
17 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* The IP fragmentation functionality.
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*
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* Version: $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
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*
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* Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
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* Alan Cox <Alan.Cox@linux.org>
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*
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* Fixes:
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* Alan Cox : Split from ip.c , see ip_input.c for history.
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* David S. Miller : Begin massive cleanup...
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* Andi Kleen : Add sysctls.
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* xxxx : Overlapfrag bug.
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* Ultima : ip_expire() kernel panic.
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* Bill Hawes : Frag accounting and evictor fixes.
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* John McDonald : 0 length frag bug.
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* Alexey Kuznetsov: SMP races, threading, cleanup.
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* Patrick McHardy : LRU queue of frag heads for evictor.
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*/
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#include <linux/compiler.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/jiffies.h>
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#include <linux/skbuff.h>
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#include <linux/list.h>
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#include <linux/ip.h>
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#include <linux/icmp.h>
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#include <linux/netdevice.h>
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#include <linux/jhash.h>
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#include <linux/random.h>
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#include <net/sock.h>
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#include <net/ip.h>
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#include <net/icmp.h>
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#include <net/checksum.h>
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#include <net/inetpeer.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <linux/inet.h>
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#include <linux/netfilter_ipv4.h>
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/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
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* code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
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* as well. Or notify me, at least. --ANK
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*/
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/* Fragment cache limits. We will commit 256K at one time. Should we
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* cross that limit we will prune down to 192K. This should cope with
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* even the most extreme cases without allowing an attacker to measurably
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* harm machine performance.
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*/
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int sysctl_ipfrag_high_thresh __read_mostly = 256*1024;
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int sysctl_ipfrag_low_thresh __read_mostly = 192*1024;
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int sysctl_ipfrag_max_dist __read_mostly = 64;
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/* Important NOTE! Fragment queue must be destroyed before MSL expires.
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* RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
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*/
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int sysctl_ipfrag_time __read_mostly = IP_FRAG_TIME;
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struct ipfrag_skb_cb
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{
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struct inet_skb_parm h;
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int offset;
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};
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#define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb))
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/* Describe an entry in the "incomplete datagrams" queue. */
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struct ipq {
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struct hlist_node list;
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struct list_head lru_list; /* lru list member */
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u32 user;
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__be32 saddr;
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__be32 daddr;
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__be16 id;
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u8 protocol;
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u8 last_in;
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#define COMPLETE 4
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#define FIRST_IN 2
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#define LAST_IN 1
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struct sk_buff *fragments; /* linked list of received fragments */
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int len; /* total length of original datagram */
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int meat;
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spinlock_t lock;
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atomic_t refcnt;
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struct timer_list timer; /* when will this queue expire? */
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ktime_t stamp;
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int iif;
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unsigned int rid;
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struct inet_peer *peer;
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};
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/* Hash table. */
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#define IPQ_HASHSZ 64
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/* Per-bucket lock is easy to add now. */
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static struct hlist_head ipq_hash[IPQ_HASHSZ];
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static DEFINE_RWLOCK(ipfrag_lock);
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static u32 ipfrag_hash_rnd;
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static LIST_HEAD(ipq_lru_list);
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int ip_frag_nqueues = 0;
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static __inline__ void __ipq_unlink(struct ipq *qp)
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{
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hlist_del(&qp->list);
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list_del(&qp->lru_list);
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ip_frag_nqueues--;
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}
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static __inline__ void ipq_unlink(struct ipq *ipq)
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{
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write_lock(&ipfrag_lock);
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__ipq_unlink(ipq);
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write_unlock(&ipfrag_lock);
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}
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static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
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{
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return jhash_3words((__force u32)id << 16 | prot,
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(__force u32)saddr, (__force u32)daddr,
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ipfrag_hash_rnd) & (IPQ_HASHSZ - 1);
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}
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static struct timer_list ipfrag_secret_timer;
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int sysctl_ipfrag_secret_interval __read_mostly = 10 * 60 * HZ;
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static void ipfrag_secret_rebuild(unsigned long dummy)
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{
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unsigned long now = jiffies;
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int i;
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write_lock(&ipfrag_lock);
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get_random_bytes(&ipfrag_hash_rnd, sizeof(u32));
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for (i = 0; i < IPQ_HASHSZ; i++) {
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struct ipq *q;
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struct hlist_node *p, *n;
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hlist_for_each_entry_safe(q, p, n, &ipq_hash[i], list) {
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unsigned int hval = ipqhashfn(q->id, q->saddr,
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q->daddr, q->protocol);
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if (hval != i) {
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hlist_del(&q->list);
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/* Relink to new hash chain. */
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hlist_add_head(&q->list, &ipq_hash[hval]);
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}
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}
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}
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write_unlock(&ipfrag_lock);
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mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
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}
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atomic_t ip_frag_mem = ATOMIC_INIT(0); /* Memory used for fragments */
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/* Memory Tracking Functions. */
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static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
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{
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if (work)
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*work -= skb->truesize;
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atomic_sub(skb->truesize, &ip_frag_mem);
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kfree_skb(skb);
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}
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static __inline__ void frag_free_queue(struct ipq *qp, int *work)
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{
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if (work)
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*work -= sizeof(struct ipq);
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atomic_sub(sizeof(struct ipq), &ip_frag_mem);
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kfree(qp);
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}
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static __inline__ struct ipq *frag_alloc_queue(void)
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{
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struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
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if (!qp)
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return NULL;
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atomic_add(sizeof(struct ipq), &ip_frag_mem);
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return qp;
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}
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/* Destruction primitives. */
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/* Complete destruction of ipq. */
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static void ip_frag_destroy(struct ipq *qp, int *work)
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{
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struct sk_buff *fp;
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BUG_TRAP(qp->last_in&COMPLETE);
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BUG_TRAP(del_timer(&qp->timer) == 0);
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if (qp->peer)
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inet_putpeer(qp->peer);
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/* Release all fragment data. */
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fp = qp->fragments;
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while (fp) {
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struct sk_buff *xp = fp->next;
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frag_kfree_skb(fp, work);
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fp = xp;
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}
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/* Finally, release the queue descriptor itself. */
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frag_free_queue(qp, work);
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}
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static __inline__ void ipq_put(struct ipq *ipq, int *work)
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{
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if (atomic_dec_and_test(&ipq->refcnt))
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ip_frag_destroy(ipq, work);
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}
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/* Kill ipq entry. It is not destroyed immediately,
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* because caller (and someone more) holds reference count.
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*/
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static void ipq_kill(struct ipq *ipq)
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{
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if (del_timer(&ipq->timer))
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atomic_dec(&ipq->refcnt);
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if (!(ipq->last_in & COMPLETE)) {
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ipq_unlink(ipq);
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atomic_dec(&ipq->refcnt);
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ipq->last_in |= COMPLETE;
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}
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}
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/* Memory limiting on fragments. Evictor trashes the oldest
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* fragment queue until we are back under the threshold.
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*/
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static void ip_evictor(void)
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{
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struct ipq *qp;
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struct list_head *tmp;
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int work;
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work = atomic_read(&ip_frag_mem) - sysctl_ipfrag_low_thresh;
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if (work <= 0)
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return;
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while (work > 0) {
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read_lock(&ipfrag_lock);
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if (list_empty(&ipq_lru_list)) {
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read_unlock(&ipfrag_lock);
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return;
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}
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tmp = ipq_lru_list.next;
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qp = list_entry(tmp, struct ipq, lru_list);
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atomic_inc(&qp->refcnt);
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read_unlock(&ipfrag_lock);
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spin_lock(&qp->lock);
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if (!(qp->last_in&COMPLETE))
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ipq_kill(qp);
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spin_unlock(&qp->lock);
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ipq_put(qp, &work);
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IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
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}
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}
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/*
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* Oops, a fragment queue timed out. Kill it and send an ICMP reply.
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*/
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static void ip_expire(unsigned long arg)
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{
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struct ipq *qp = (struct ipq *) arg;
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spin_lock(&qp->lock);
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if (qp->last_in & COMPLETE)
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goto out;
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ipq_kill(qp);
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IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
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IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
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if ((qp->last_in&FIRST_IN) && qp->fragments != NULL) {
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struct sk_buff *head = qp->fragments;
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/* Send an ICMP "Fragment Reassembly Timeout" message. */
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if ((head->dev = dev_get_by_index(qp->iif)) != NULL) {
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icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
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dev_put(head->dev);
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}
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}
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out:
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spin_unlock(&qp->lock);
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ipq_put(qp, NULL);
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}
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/* Creation primitives. */
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static struct ipq *ip_frag_intern(struct ipq *qp_in)
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{
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struct ipq *qp;
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#ifdef CONFIG_SMP
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struct hlist_node *n;
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#endif
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unsigned int hash;
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write_lock(&ipfrag_lock);
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hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
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qp_in->protocol);
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#ifdef CONFIG_SMP
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/* With SMP race we have to recheck hash table, because
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* such entry could be created on other cpu, while we
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* promoted read lock to write lock.
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*/
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hlist_for_each_entry(qp, n, &ipq_hash[hash], list) {
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if (qp->id == qp_in->id &&
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qp->saddr == qp_in->saddr &&
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qp->daddr == qp_in->daddr &&
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qp->protocol == qp_in->protocol &&
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qp->user == qp_in->user) {
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atomic_inc(&qp->refcnt);
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write_unlock(&ipfrag_lock);
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qp_in->last_in |= COMPLETE;
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ipq_put(qp_in, NULL);
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return qp;
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}
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}
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#endif
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qp = qp_in;
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if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time))
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atomic_inc(&qp->refcnt);
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atomic_inc(&qp->refcnt);
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hlist_add_head(&qp->list, &ipq_hash[hash]);
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INIT_LIST_HEAD(&qp->lru_list);
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list_add_tail(&qp->lru_list, &ipq_lru_list);
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ip_frag_nqueues++;
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write_unlock(&ipfrag_lock);
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return qp;
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}
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/* Add an entry to the 'ipq' queue for a newly received IP datagram. */
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static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
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{
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struct ipq *qp;
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if ((qp = frag_alloc_queue()) == NULL)
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goto out_nomem;
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qp->protocol = iph->protocol;
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qp->last_in = 0;
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qp->id = iph->id;
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qp->saddr = iph->saddr;
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qp->daddr = iph->daddr;
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qp->user = user;
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qp->len = 0;
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qp->meat = 0;
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qp->fragments = NULL;
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qp->iif = 0;
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qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
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/* Initialize a timer for this entry. */
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init_timer(&qp->timer);
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qp->timer.data = (unsigned long) qp; /* pointer to queue */
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qp->timer.function = ip_expire; /* expire function */
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spin_lock_init(&qp->lock);
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atomic_set(&qp->refcnt, 1);
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return ip_frag_intern(qp);
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out_nomem:
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LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
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return NULL;
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}
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/* Find the correct entry in the "incomplete datagrams" queue for
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* this IP datagram, and create new one, if nothing is found.
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*/
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static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
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{
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__be16 id = iph->id;
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__be32 saddr = iph->saddr;
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__be32 daddr = iph->daddr;
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__u8 protocol = iph->protocol;
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unsigned int hash;
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struct ipq *qp;
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struct hlist_node *n;
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read_lock(&ipfrag_lock);
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hash = ipqhashfn(id, saddr, daddr, protocol);
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hlist_for_each_entry(qp, n, &ipq_hash[hash], list) {
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if (qp->id == id &&
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qp->saddr == saddr &&
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qp->daddr == daddr &&
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qp->protocol == protocol &&
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qp->user == user) {
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atomic_inc(&qp->refcnt);
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read_unlock(&ipfrag_lock);
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return qp;
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}
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}
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read_unlock(&ipfrag_lock);
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|
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return ip_frag_create(iph, user);
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}
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/* Is the fragment too far ahead to be part of ipq? */
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static inline int ip_frag_too_far(struct ipq *qp)
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{
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struct inet_peer *peer = qp->peer;
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unsigned int max = sysctl_ipfrag_max_dist;
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unsigned int start, end;
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|
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int rc;
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|
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if (!peer || !max)
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return 0;
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|
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start = qp->rid;
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end = atomic_inc_return(&peer->rid);
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qp->rid = end;
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|
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rc = qp->fragments && (end - start) > max;
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|
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if (rc) {
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IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
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}
|
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|
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return rc;
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}
|
|
|
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static int ip_frag_reinit(struct ipq *qp)
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{
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struct sk_buff *fp;
|
|
|
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if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time)) {
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atomic_inc(&qp->refcnt);
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return -ETIMEDOUT;
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}
|
|
|
|
fp = qp->fragments;
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do {
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struct sk_buff *xp = fp->next;
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frag_kfree_skb(fp, NULL);
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fp = xp;
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} while (fp);
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|
|
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qp->last_in = 0;
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qp->len = 0;
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qp->meat = 0;
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qp->fragments = NULL;
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qp->iif = 0;
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|
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return 0;
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}
|
|
|
|
/* Add new segment to existing queue. */
|
|
static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
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{
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struct sk_buff *prev, *next;
|
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int flags, offset;
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int ihl, end;
|
|
|
|
if (qp->last_in & COMPLETE)
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goto err;
|
|
|
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if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
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unlikely(ip_frag_too_far(qp)) && unlikely(ip_frag_reinit(qp))) {
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ipq_kill(qp);
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goto err;
|
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}
|
|
|
|
offset = ntohs(ip_hdr(skb)->frag_off);
|
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flags = offset & ~IP_OFFSET;
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offset &= IP_OFFSET;
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offset <<= 3; /* offset is in 8-byte chunks */
|
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ihl = ip_hdrlen(skb);
|
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|
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/* Determine the position of this fragment. */
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end = offset + skb->len - ihl;
|
|
|
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/* Is this the final fragment? */
|
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if ((flags & IP_MF) == 0) {
|
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/* If we already have some bits beyond end
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* or have different end, the segment is corrrupted.
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|
*/
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if (end < qp->len ||
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((qp->last_in & LAST_IN) && end != qp->len))
|
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goto err;
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qp->last_in |= LAST_IN;
|
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qp->len = end;
|
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} else {
|
|
if (end&7) {
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end &= ~7;
|
|
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
|
|
skb->ip_summed = CHECKSUM_NONE;
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|
}
|
|
if (end > qp->len) {
|
|
/* Some bits beyond end -> corruption. */
|
|
if (qp->last_in & LAST_IN)
|
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goto err;
|
|
qp->len = end;
|
|
}
|
|
}
|
|
if (end == offset)
|
|
goto err;
|
|
|
|
if (pskb_pull(skb, ihl) == NULL)
|
|
goto err;
|
|
if (pskb_trim_rcsum(skb, end-offset))
|
|
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->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;
|
|
if (end <= offset)
|
|
goto err;
|
|
if (!pskb_pull(skb, i))
|
|
goto err;
|
|
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
|
|
skb->ip_summed = CHECKSUM_NONE;
|
|
}
|
|
}
|
|
|
|
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->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->fragments = next;
|
|
|
|
qp->meat -= free_it->len;
|
|
frag_kfree_skb(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->fragments = skb;
|
|
|
|
if (skb->dev)
|
|
qp->iif = skb->dev->ifindex;
|
|
skb->dev = NULL;
|
|
qp->stamp = skb->tstamp;
|
|
qp->meat += skb->len;
|
|
atomic_add(skb->truesize, &ip_frag_mem);
|
|
if (offset == 0)
|
|
qp->last_in |= FIRST_IN;
|
|
|
|
write_lock(&ipfrag_lock);
|
|
list_move_tail(&qp->lru_list, &ipq_lru_list);
|
|
write_unlock(&ipfrag_lock);
|
|
|
|
return;
|
|
|
|
err:
|
|
kfree_skb(skb);
|
|
}
|
|
|
|
|
|
/* Build a new IP datagram from all its fragments. */
|
|
|
|
static struct sk_buff *ip_frag_reasm(struct ipq *qp, struct net_device *dev)
|
|
{
|
|
struct iphdr *iph;
|
|
struct sk_buff *fp, *head = qp->fragments;
|
|
int len;
|
|
int ihlen;
|
|
|
|
ipq_kill(qp);
|
|
|
|
BUG_TRAP(head != NULL);
|
|
BUG_TRAP(FRAG_CB(head)->offset == 0);
|
|
|
|
/* Allocate a new buffer for the datagram. */
|
|
ihlen = ip_hdrlen(head);
|
|
len = ihlen + qp->len;
|
|
|
|
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_shinfo(head)->frag_list) {
|
|
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_shinfo(head)->frag_list = NULL;
|
|
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, &ip_frag_mem);
|
|
}
|
|
|
|
skb_shinfo(head)->frag_list = head->next;
|
|
skb_push(head, head->data - skb_network_header(head));
|
|
atomic_sub(head->truesize, &ip_frag_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, &ip_frag_mem);
|
|
}
|
|
|
|
head->next = NULL;
|
|
head->dev = dev;
|
|
head->tstamp = qp->stamp;
|
|
|
|
iph = ip_hdr(head);
|
|
iph->frag_off = 0;
|
|
iph->tot_len = htons(len);
|
|
IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
|
|
qp->fragments = NULL;
|
|
return head;
|
|
|
|
out_nomem:
|
|
LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
|
|
"queue %p\n", qp);
|
|
goto out_fail;
|
|
out_oversize:
|
|
if (net_ratelimit())
|
|
printk(KERN_INFO
|
|
"Oversized IP packet from %d.%d.%d.%d.\n",
|
|
NIPQUAD(qp->saddr));
|
|
out_fail:
|
|
IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
|
|
return NULL;
|
|
}
|
|
|
|
/* Process an incoming IP datagram fragment. */
|
|
struct sk_buff *ip_defrag(struct sk_buff *skb, u32 user)
|
|
{
|
|
struct ipq *qp;
|
|
struct net_device *dev;
|
|
|
|
IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
|
|
|
|
/* Start by cleaning up the memory. */
|
|
if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh)
|
|
ip_evictor();
|
|
|
|
dev = skb->dev;
|
|
|
|
/* Lookup (or create) queue header */
|
|
if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
|
|
struct sk_buff *ret = NULL;
|
|
|
|
spin_lock(&qp->lock);
|
|
|
|
ip_frag_queue(qp, skb);
|
|
|
|
if (qp->last_in == (FIRST_IN|LAST_IN) &&
|
|
qp->meat == qp->len)
|
|
ret = ip_frag_reasm(qp, dev);
|
|
|
|
spin_unlock(&qp->lock);
|
|
ipq_put(qp, NULL);
|
|
return ret;
|
|
}
|
|
|
|
IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
|
|
kfree_skb(skb);
|
|
return NULL;
|
|
}
|
|
|
|
void __init ipfrag_init(void)
|
|
{
|
|
ipfrag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
|
|
(jiffies ^ (jiffies >> 6)));
|
|
|
|
init_timer(&ipfrag_secret_timer);
|
|
ipfrag_secret_timer.function = ipfrag_secret_rebuild;
|
|
ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval;
|
|
add_timer(&ipfrag_secret_timer);
|
|
}
|
|
|
|
EXPORT_SYMBOL(ip_defrag);
|