blob: 443b3f89192f5841f78e7783874f9c8b9b479020 [file] [log] [blame]
/*
* 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 <net/inet_frag.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/inet.h>
#include <linux/netfilter_ipv4.h>
/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
* code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
* as well. Or notify me, at least. --ANK
*/
int sysctl_ipfrag_max_dist __read_mostly = 64;
struct ipfrag_skb_cb
{
struct inet_skb_parm h;
int offset;
};
#define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb))
/* Describe an entry in the "incomplete datagrams" queue. */
struct ipq {
struct inet_frag_queue q;
u32 user;
__be32 saddr;
__be32 daddr;
__be16 id;
u8 protocol;
int iif;
unsigned int rid;
struct inet_peer *peer;
};
struct inet_frags_ctl ip4_frags_ctl __read_mostly = {
/*
* 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.
*/
.high_thresh = 256 * 1024,
.low_thresh = 192 * 1024,
/*
* Important NOTE! Fragment queue must be destroyed before MSL expires.
* RFC791 is wrong proposing to prolongate timer each fragment arrival
* by TTL.
*/
.timeout = IP_FRAG_TIME,
.secret_interval = 10 * 60 * HZ,
};
static struct inet_frags ip4_frags;
int ip_frag_nqueues(void)
{
return ip4_frags.nqueues;
}
int ip_frag_mem(void)
{
return atomic_read(&ip4_frags.mem);
}
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
struct net_device *dev);
static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
{
return jhash_3words((__force u32)id << 16 | prot,
(__force u32)saddr, (__force u32)daddr,
ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
}
static unsigned int ip4_hashfn(struct inet_frag_queue *q)
{
struct ipq *ipq;
ipq = container_of(q, struct ipq, q);
return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
}
/* Memory Tracking Functions. */
static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
{
if (work)
*work -= skb->truesize;
atomic_sub(skb->truesize, &ip4_frags.mem);
kfree_skb(skb);
}
static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
{
struct ipq *qp;
qp = container_of(q, struct ipq, q);
if (qp->peer)
inet_putpeer(qp->peer);
kfree(qp);
}
static __inline__ struct ipq *frag_alloc_queue(void)
{
struct ipq *qp = kzalloc(sizeof(struct ipq), GFP_ATOMIC);
if (!qp)
return NULL;
atomic_add(sizeof(struct ipq), &ip4_frags.mem);
return qp;
}
/* Destruction primitives. */
static __inline__ void ipq_put(struct ipq *ipq)
{
inet_frag_put(&ipq->q, &ip4_frags);
}
/* Kill ipq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static void ipq_kill(struct ipq *ipq)
{
inet_frag_kill(&ipq->q, &ip4_frags);
}
/* Memory limiting on fragments. Evictor trashes the oldest
* fragment queue until we are back under the threshold.
*/
static void ip_evictor(void)
{
int evicted;
evicted = inet_frag_evictor(&ip4_frags);
if (evicted)
IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS, evicted);
}
/*
* Oops, a fragment queue timed out. Kill it and send an ICMP reply.
*/
static void ip_expire(unsigned long arg)
{
struct ipq *qp = (struct ipq *) arg;
spin_lock(&qp->q.lock);
if (qp->q.last_in & COMPLETE)
goto out;
ipq_kill(qp);
IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {
struct sk_buff *head = qp->q.fragments;
/* Send an ICMP "Fragment Reassembly Timeout" message. */
if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
dev_put(head->dev);
}
}
out:
spin_unlock(&qp->q.lock);
ipq_put(qp);
}
/* Creation primitives. */
static struct ipq *ip_frag_intern(struct ipq *qp_in)
{
struct ipq *qp;
#ifdef CONFIG_SMP
struct hlist_node *n;
#endif
unsigned int hash;
write_lock(&ip4_frags.lock);
hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
qp_in->protocol);
#ifdef CONFIG_SMP
/* With SMP race we have to recheck hash table, because
* such entry could be created on other cpu, while we
* promoted read lock to write lock.
*/
hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
if (qp->id == qp_in->id &&
qp->saddr == qp_in->saddr &&
qp->daddr == qp_in->daddr &&
qp->protocol == qp_in->protocol &&
qp->user == qp_in->user) {
atomic_inc(&qp->q.refcnt);
write_unlock(&ip4_frags.lock);
qp_in->q.last_in |= COMPLETE;
ipq_put(qp_in);
return qp;
}
}
#endif
qp = qp_in;
if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout))
atomic_inc(&qp->q.refcnt);
atomic_inc(&qp->q.refcnt);
hlist_add_head(&qp->q.list, &ip4_frags.hash[hash]);
INIT_LIST_HEAD(&qp->q.lru_list);
list_add_tail(&qp->q.lru_list, &ip4_frags.lru_list);
ip4_frags.nqueues++;
write_unlock(&ip4_frags.lock);
return qp;
}
/* Add an entry to the 'ipq' queue for a newly received IP datagram. */
static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
{
struct ipq *qp;
if ((qp = frag_alloc_queue()) == NULL)
goto out_nomem;
qp->protocol = iph->protocol;
qp->id = iph->id;
qp->saddr = iph->saddr;
qp->daddr = iph->daddr;
qp->user = user;
qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
/* Initialize a timer for this entry. */
init_timer(&qp->q.timer);
qp->q.timer.data = (unsigned long) qp; /* pointer to queue */
qp->q.timer.function = ip_expire; /* expire function */
spin_lock_init(&qp->q.lock);
atomic_set(&qp->q.refcnt, 1);
return ip_frag_intern(qp);
out_nomem:
LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
return NULL;
}
/* Find the correct entry in the "incomplete datagrams" queue for
* this IP datagram, and create new one, if nothing is found.
*/
static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
{
__be16 id = iph->id;
__be32 saddr = iph->saddr;
__be32 daddr = iph->daddr;
__u8 protocol = iph->protocol;
unsigned int hash;
struct ipq *qp;
struct hlist_node *n;
read_lock(&ip4_frags.lock);
hash = ipqhashfn(id, saddr, daddr, protocol);
hlist_for_each_entry(qp, n, &ip4_frags.hash[hash], q.list) {
if (qp->id == id &&
qp->saddr == saddr &&
qp->daddr == daddr &&
qp->protocol == protocol &&
qp->user == user) {
atomic_inc(&qp->q.refcnt);
read_unlock(&ip4_frags.lock);
return qp;
}
}
read_unlock(&ip4_frags.lock);
return ip_frag_create(iph, user);
}
/* Is the fragment too far ahead to be part of ipq? */
static inline int ip_frag_too_far(struct ipq *qp)
{
struct inet_peer *peer = qp->peer;
unsigned int max = sysctl_ipfrag_max_dist;
unsigned int start, end;
int rc;
if (!peer || !max)
return 0;
start = qp->rid;
end = atomic_inc_return(&peer->rid);
qp->rid = end;
rc = qp->q.fragments && (end - start) > max;
if (rc) {
IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
}
return rc;
}
static int ip_frag_reinit(struct ipq *qp)
{
struct sk_buff *fp;
if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) {
atomic_inc(&qp->q.refcnt);
return -ETIMEDOUT;
}
fp = qp->q.fragments;
do {
struct sk_buff *xp = fp->next;
frag_kfree_skb(fp, NULL);
fp = xp;
} while (fp);
qp->q.last_in = 0;
qp->q.len = 0;
qp->q.meat = 0;
qp->q.fragments = NULL;
qp->iif = 0;
return 0;
}
/* Add new segment to existing queue. */
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
{
struct sk_buff *prev, *next;
struct net_device *dev;
int flags, offset;
int ihl, end;
int err = -ENOENT;
if (qp->q.last_in & COMPLETE)
goto err;
if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
unlikely(ip_frag_too_far(qp)) &&
unlikely(err = ip_frag_reinit(qp))) {
ipq_kill(qp);
goto err;
}
offset = ntohs(ip_hdr(skb)->frag_off);
flags = offset & ~IP_OFFSET;
offset &= IP_OFFSET;
offset <<= 3; /* offset is in 8-byte chunks */
ihl = ip_hdrlen(skb);
/* Determine the position of this fragment. */
end = offset + skb->len - ihl;
err = -EINVAL;
/* Is this the final fragment? */
if ((flags & IP_MF) == 0) {
/* If we already have some bits beyond end
* or have different end, the segment is corrrupted.
*/
if (end < qp->q.len ||
((qp->q.last_in & LAST_IN) && end != qp->q.len))
goto err;
qp->q.last_in |= LAST_IN;
qp->q.len = end;
} else {
if (end&7) {
end &= ~7;
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
skb->ip_summed = CHECKSUM_NONE;
}
if (end > qp->q.len) {
/* Some bits beyond end -> corruption. */
if (qp->q.last_in & LAST_IN)
goto err;
qp->q.len = end;
}
}
if (end == offset)
goto err;
err = -ENOMEM;
if (pskb_pull(skb, ihl) == NULL)
goto err;
err = pskb_trim_rcsum(skb, end - offset);
if (err)
goto err;
/* Find out which fragments are in front and at the back of us
* in the chain of fragments so far. We must know where to put
* this fragment, right?
*/
prev = NULL;
for (next = qp->q.fragments; next != NULL; next = next->next) {
if (FRAG_CB(next)->offset >= offset)
break; /* bingo! */
prev = next;
}
/* We found where to put this one. Check for overlap with
* preceding fragment, and, if needed, align things so that
* any overlaps are eliminated.
*/
if (prev) {
int i = (FRAG_CB(prev)->offset + prev->len) - offset;
if (i > 0) {
offset += i;
err = -EINVAL;
if (end <= offset)
goto err;
err = -ENOMEM;
if (!pskb_pull(skb, i))
goto err;
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
skb->ip_summed = CHECKSUM_NONE;
}
}
err = -ENOMEM;
while (next && FRAG_CB(next)->offset < end) {
int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
if (i < next->len) {
/* Eat head of the next overlapped fragment
* and leave the loop. The next ones cannot overlap.
*/
if (!pskb_pull(next, i))
goto err;
FRAG_CB(next)->offset += i;
qp->q.meat -= i;
if (next->ip_summed != CHECKSUM_UNNECESSARY)
next->ip_summed = CHECKSUM_NONE;
break;
} else {
struct sk_buff *free_it = next;
/* Old fragment is completely overridden with
* new one drop it.
*/
next = next->next;
if (prev)
prev->next = next;
else
qp->q.fragments = next;
qp->q.meat -= free_it->len;
frag_kfree_skb(free_it, NULL);
}
}
FRAG_CB(skb)->offset = offset;
/* Insert this fragment in the chain of fragments. */
skb->next = next;
if (prev)
prev->next = skb;
else
qp->q.fragments = skb;
dev = skb->dev;
if (dev) {
qp->iif = dev->ifindex;
skb->dev = NULL;
}
qp->q.stamp = skb->tstamp;
qp->q.meat += skb->len;
atomic_add(skb->truesize, &ip4_frags.mem);
if (offset == 0)
qp->q.last_in |= FIRST_IN;
if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)
return ip_frag_reasm(qp, prev, dev);
write_lock(&ip4_frags.lock);
list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list);
write_unlock(&ip4_frags.lock);
return -EINPROGRESS;
err:
kfree_skb(skb);
return err;
}
/* Build a new IP datagram from all its fragments. */
static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
struct net_device *dev)
{
struct iphdr *iph;
struct sk_buff *fp, *head = qp->q.fragments;
int len;
int ihlen;
int err;
ipq_kill(qp);
/* Make the one we just received the head. */
if (prev) {
head = prev->next;
fp = skb_clone(head, GFP_ATOMIC);
if (!fp)
goto out_nomem;
fp->next = head->next;
prev->next = fp;
skb_morph(head, qp->q.fragments);
head->next = qp->q.fragments->next;
kfree_skb(qp->q.fragments);
qp->q.fragments = head;
}
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->q.len;
err = -E2BIG;
if (len > 65535)
goto out_oversize;
/* Head of list must not be cloned. */
err = -ENOMEM;
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, &ip4_frags.mem);
}
skb_shinfo(head)->frag_list = head->next;
skb_push(head, head->data - skb_network_header(head));
atomic_sub(head->truesize, &ip4_frags.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, &ip4_frags.mem);
}
head->next = NULL;
head->dev = dev;
head->tstamp = qp->q.stamp;
iph = ip_hdr(head);
iph->frag_off = 0;
iph->tot_len = htons(len);
IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
qp->q.fragments = NULL;
return 0;
out_nomem:
LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
"queue %p\n", qp);
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 err;
}
/* Process an incoming IP datagram fragment. */
int ip_defrag(struct sk_buff *skb, u32 user)
{
struct ipq *qp;
IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
/* Start by cleaning up the memory. */
if (atomic_read(&ip4_frags.mem) > ip4_frags_ctl.high_thresh)
ip_evictor();
/* Lookup (or create) queue header */
if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
int ret;
spin_lock(&qp->q.lock);
ret = ip_frag_queue(qp, skb);
spin_unlock(&qp->q.lock);
ipq_put(qp);
return ret;
}
IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
kfree_skb(skb);
return -ENOMEM;
}
void __init ipfrag_init(void)
{
ip4_frags.ctl = &ip4_frags_ctl;
ip4_frags.hashfn = ip4_hashfn;
ip4_frags.destructor = ip4_frag_free;
ip4_frags.skb_free = NULL;
ip4_frags.qsize = sizeof(struct ipq);
inet_frags_init(&ip4_frags);
}
EXPORT_SYMBOL(ip_defrag);