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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* The IP fragmentation functionality.
*
* Version: $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
*
* Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
* Alan Cox <Alan.Cox@linux.org>
*
* Fixes:
* Alan Cox : Split from ip.c , see ip_input.c for history.
* David S. Miller : Begin massive cleanup...
* Andi Kleen : Add sysctls.
* xxxx : Overlapfrag bug.
* Ultima : ip_expire() kernel panic.
* Bill Hawes : Frag accounting and evictor fixes.
* John McDonald : 0 length frag bug.
* Alexey Kuznetsov: SMP races, threading, cleanup.
* Patrick McHardy : LRU queue of frag heads for evictor.
*/
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/jiffies.h>
#include <linux/skbuff.h>
#include <linux/list.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/checksum.h>
#include <net/inetpeer.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/inet.h>
#include <linux/netfilter_ipv4.h>
/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
* code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
* as well. Or notify me, at least. --ANK
*/
/* Fragment cache limits. We will commit 256K at one time. Should we
* cross that limit we will prune down to 192K. This should cope with
* even the most extreme cases without allowing an attacker to measurably
* harm machine performance.
*/
int sysctl_ipfrag_high_thresh = 256*1024;
int sysctl_ipfrag_low_thresh = 192*1024;
int sysctl_ipfrag_max_dist = 64;
/* Important NOTE! Fragment queue must be destroyed before MSL expires.
* RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
*/
int sysctl_ipfrag_time = IP_FRAG_TIME;
struct ipfrag_skb_cb
{
struct inet_skb_parm h;
int offset;
};
#define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb))
/* Describe an entry in the "incomplete datagrams" queue. */
struct ipq {
struct hlist_node list;
struct list_head lru_list; /* lru list member */
u32 user;
u32 saddr;
u32 daddr;
u16 id;
u8 protocol;
u8 last_in;
#define COMPLETE 4
#define FIRST_IN 2
#define LAST_IN 1
struct sk_buff *fragments; /* linked list of received fragments */
int len; /* total length of original datagram */
int meat;
spinlock_t lock;
atomic_t refcnt;
struct timer_list timer; /* when will this queue expire? */
struct timeval stamp;
int iif;
unsigned int rid;
struct inet_peer *peer;
};
/* Hash table. */
#define IPQ_HASHSZ 64
/* Per-bucket lock is easy to add now. */
static struct hlist_head ipq_hash[IPQ_HASHSZ];
static DEFINE_RWLOCK(ipfrag_lock);
static u32 ipfrag_hash_rnd;
static LIST_HEAD(ipq_lru_list);
int ip_frag_nqueues = 0;
static __inline__ void __ipq_unlink(struct ipq *qp)
{
hlist_del(&qp->list);
list_del(&qp->lru_list);
ip_frag_nqueues--;
}
static __inline__ void ipq_unlink(struct ipq *ipq)
{
write_lock(&ipfrag_lock);
__ipq_unlink(ipq);
write_unlock(&ipfrag_lock);
}
static unsigned int ipqhashfn(u16 id, u32 saddr, u32 daddr, u8 prot)
{
return jhash_3words((u32)id << 16 | prot, saddr, daddr,
ipfrag_hash_rnd) & (IPQ_HASHSZ - 1);
}
static struct timer_list ipfrag_secret_timer;
int sysctl_ipfrag_secret_interval = 10 * 60 * HZ;
static void ipfrag_secret_rebuild(unsigned long dummy)
{
unsigned long now = jiffies;
int i;
write_lock(&ipfrag_lock);
get_random_bytes(&ipfrag_hash_rnd, sizeof(u32));
for (i = 0; i < IPQ_HASHSZ; i++) {
struct ipq *q;
struct hlist_node *p, *n;
hlist_for_each_entry_safe(q, p, n, &ipq_hash[i], list) {
unsigned int hval = ipqhashfn(q->id, q->saddr,
q->daddr, q->protocol);
if (hval != i) {
hlist_del(&q->list);
/* Relink to new hash chain. */
hlist_add_head(&q->list, &ipq_hash[hval]);
}
}
}
write_unlock(&ipfrag_lock);
mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
}
atomic_t ip_frag_mem = ATOMIC_INIT(0); /* Memory used for fragments */
/* Memory Tracking Functions. */
static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
{
if (work)
*work -= skb->truesize;
atomic_sub(skb->truesize, &ip_frag_mem);
kfree_skb(skb);
}
static __inline__ void frag_free_queue(struct ipq *qp, int *work)
{
if (work)
*work -= sizeof(struct ipq);
atomic_sub(sizeof(struct ipq), &ip_frag_mem);
kfree(qp);
}
static __inline__ struct ipq *frag_alloc_queue(void)
{
struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
if(!qp)
return NULL;
atomic_add(sizeof(struct ipq), &ip_frag_mem);
return qp;
}
/* Destruction primitives. */
/* Complete destruction of ipq. */
static void ip_frag_destroy(struct ipq *qp, int *work)
{
struct sk_buff *fp;
BUG_TRAP(qp->last_in&COMPLETE);
BUG_TRAP(del_timer(&qp->timer) == 0);
if (qp->peer)
inet_putpeer(qp->peer);
/* Release all fragment data. */
fp = qp->fragments;
while (fp) {
struct sk_buff *xp = fp->next;
frag_kfree_skb(fp, work);
fp = xp;
}
/* Finally, release the queue descriptor itself. */
frag_free_queue(qp, work);
}
static __inline__ void ipq_put(struct ipq *ipq, int *work)
{
if (atomic_dec_and_test(&ipq->refcnt))
ip_frag_destroy(ipq, work);
}
/* Kill ipq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static void ipq_kill(struct ipq *ipq)
{
if (del_timer(&ipq->timer))
atomic_dec(&ipq->refcnt);
if (!(ipq->last_in & COMPLETE)) {
ipq_unlink(ipq);
atomic_dec
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