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linux/net/ipv6/reassembly.c

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/*
* IPv6 fragment reassembly
* Linux INET6 implementation
*
* Authors:
* Pedro Roque <roque@di.fc.ul.pt>
*
* $Id: reassembly.c,v 1.26 2001/03/07 22:00:57 davem Exp $
*
* Based on: net/ipv4/ip_fragment.c
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
/*
* Fixes:
* Andi Kleen Make it work with multiple hosts.
* More RFC compliance.
*
* Horst von Brand Add missing #include <linux/string.h>
* Alexey Kuznetsov SMP races, threading, cleanup.
* Patrick McHardy LRU queue of frag heads for evictor.
* Mitsuru KANDA @USAGI Register inet6_protocol{}.
* David Stevens and
* YOSHIFUJI,H. @USAGI Always remove fragment header to
* calculate ICV correctly.
*/
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/jiffies.h>
#include <linux/net.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <linux/random.h>
#include <linux/jhash.h>
#include <net/sock.h>
#include <net/snmp.h>
#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
int sysctl_ip6frag_high_thresh = 256*1024;
int sysctl_ip6frag_low_thresh = 192*1024;
int sysctl_ip6frag_time = IPV6_FRAG_TIMEOUT;
struct ip6frag_skb_cb
{
struct inet6_skb_parm h;
int offset;
};
#define FRAG6_CB(skb) ((struct ip6frag_skb_cb*)((skb)->cb))
/*
* Equivalent of ipv4 struct ipq
*/
struct frag_queue
{
struct hlist_node list;
struct list_head lru_list; /* lru list member */
__u32 id; /* fragment id */
struct in6_addr saddr;
struct in6_addr daddr;
spinlock_t lock;
atomic_t refcnt;
struct timer_list timer; /* expire timer */
struct sk_buff *fragments;
int len;
int meat;
int iif;
struct timeval stamp;
unsigned int csum;
__u8 last_in; /* has first/last segment arrived? */
#define COMPLETE 4
#define FIRST_IN 2
#define LAST_IN 1
__u16 nhoffset;
};
/* Hash table. */
#define IP6Q_HASHSZ 64
static struct hlist_head ip6_frag_hash[IP6Q_HASHSZ];
static DEFINE_RWLOCK(ip6_frag_lock);
static u32 ip6_frag_hash_rnd;
static LIST_HEAD(ip6_frag_lru_list);
int ip6_frag_nqueues = 0;
static __inline__ void __fq_unlink(struct frag_queue *fq)
{
hlist_del(&fq->list);
list_del(&fq->lru_list);
ip6_frag_nqueues--;
}
static __inline__ void fq_unlink(struct frag_queue *fq)
{
write_lock(&ip6_frag_lock);
__fq_unlink(fq);
write_unlock(&ip6_frag_lock);
}
static unsigned int ip6qhashfn(u32 id, struct in6_addr *saddr,
struct in6_addr *daddr)
{
u32 a, b, c;
a = saddr->s6_addr32[0];
b = saddr->s6_addr32[1];
c = saddr->s6_addr32[2];
a += JHASH_GOLDEN_RATIO;
b += JHASH_GOLDEN_RATIO;
c += ip6_frag_hash_rnd;
__jhash_mix(a, b, c);
a += saddr->s6_addr32[3];
b += daddr->s6_addr32[0];
c += daddr->s6_addr32[1];
__jhash_mix(a, b, c);
a += daddr->s6_addr32[2];
b += daddr->s6_addr32[3];
c += id;
__jhash_mix(a, b, c);
return c & (IP6Q_HASHSZ - 1);
}
static struct timer_list ip6_frag_secret_timer;
int sysctl_ip6frag_secret_interval = 10 * 60 * HZ;
static void ip6_frag_secret_rebuild(unsigned long dummy)
{
unsigned long now = jiffies;
int i;
write_lock(&ip6_frag_lock);
get_random_bytes(&ip6_frag_hash_rnd, sizeof(u32));
for (i = 0; i < IP6Q_HASHSZ; i++) {
struct frag_queue *q;
struct hlist_node *p, *n;
hlist_for_each_entry_safe(q, p, n, &ip6_frag_hash[i], list) {
unsigned int hval = ip6qhashfn(q->id,
&q->saddr,
&q->daddr);
if (hval != i) {
hlist_del(&q->list);
/* Relink to new hash chain. */
hlist_add_head(&q->list,
&ip6_frag_hash[hval]);
}
}
}
write_unlock(&ip6_frag_lock);
mod_timer(&ip6_frag_secret_timer, now + sysctl_ip6frag_secret_interval);
}
atomic_t ip6_frag_mem = ATOMIC_INIT(0);
/* Memory Tracking Functions. */
static inline void frag_kfree_skb(struct sk_buff *skb, int *work)
{
if (work)
*work -= skb->truesize;
atomic_sub(skb->truesize, &ip6_frag_mem);
kfree_skb(skb);
}
static inline void frag_free_queue(struct frag_queue *fq, int *work)
{
if (work)
*work -= sizeof(struct frag_queue);
atomic_sub(sizeof(struct frag_queue), &ip6_frag_mem);
kfree(fq);
}
static inline struct frag_queue *frag_alloc_queue(void)
{
struct frag_queue *fq = kmalloc(sizeof(struct frag_queue), GFP_ATOMIC);
if(!fq)
return NULL;
atomic_add(sizeof(struct frag_queue), &ip6_frag_mem);
return fq;
}
/* Destruction primitives. */
/* Complete destruction of fq. */
static void ip6_frag_destroy(struct frag_queue *fq, int *work)
{
struct sk_buff *fp;
BUG_TRAP(fq->last_in&COMPLETE);
BUG_TRAP(del_timer(&fq->timer) == 0);
/* Release all fragment data. */
fp = fq->fragments;
while (fp) {
struct sk_buff *xp = fp->next;
frag_kfree_skb(fp, work);
fp = xp;
}
frag_free_queue(fq, work);
}
static __inline__ void fq_put(struct frag_queue *fq, int *work)
{
if (atomic_dec_and_test(&fq->refcnt))
ip6_frag_destroy(fq, work);
}
/* Kill fq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static __inline__ void fq_kill(struct frag_queue *fq)
{
if (del_timer(&fq->timer))
atomic_dec(&fq->refcnt);
if (!(fq->last_in & COMPLETE)) {
fq_unlink(fq);
atomic_dec(&fq->refcnt);
fq->last_in |= COMPLETE;
}
}
static void ip6_evictor(void)
{
struct frag_queue *fq;
struct list_head *tmp;
int work;
work = atomic_read(&ip6_frag_mem) - sysctl_ip6frag_low_thresh;
if (work <= 0)
return;
while(work > 0) {
read_lock(&ip6_frag_lock);
if (list_empty(&ip6_frag_lru_list)) {
read_unlock(&ip6_frag_lock);
return;
}
tmp = ip6_frag_lru_list.next;
fq = list_entry(tmp, struct frag_queue, lru_list);
atomic_inc(&fq->refcnt);
read_unlock(&ip6_frag_lock);
spin_lock(&fq->lock);
if (!(fq->last_in&COMPLETE))
fq_kill(fq);
spin_unlock(&fq->lock);
fq_put(fq, &work);
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
}
}
static void ip6_frag_expire(unsigned long data)
{
struct frag_queue *fq = (struct frag_queue *) data;
spin_lock(&fq->lock);
if (fq->last_in & COMPLETE)
goto out;
fq_kill(fq);
IP6_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
/* Send error only if the first segment arrived. */
if (fq->last_in&FIRST_IN && fq->fragments) {
struct net_device *dev = dev_get_by_index(fq->iif);
/*
But use as source device on which LAST ARRIVED
segment was received. And do not use fq->dev
pointer directly, device might already disappeared.
*/
if (dev) {
fq->fragments->dev = dev;
icmpv6_send(fq->fragments, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0,
dev);
dev_put(dev);
}
}
out:
spin_unlock(&fq->lock);
fq_put(fq, NULL);
}
/* Creation primitives. */
static struct frag_queue *ip6_frag_intern(unsigned int hash,
struct frag_queue *fq_in)
{
struct frag_queue *fq;
#ifdef CONFIG_SMP
struct hlist_node *n;
#endif
write_lock(&ip6_frag_lock);
#ifdef CONFIG_SMP
hlist_for_each_entry(fq, n, &ip6_frag_hash[hash], list) {
if (fq->id == fq_in->id &&
ipv6_addr_equal(&fq_in->saddr, &fq->saddr) &&
ipv6_addr_equal(&fq_in->daddr, &fq->daddr)) {
atomic_inc(&fq->refcnt);
write_unlock(&ip6_frag_lock);
fq_in->last_in |= COMPLETE;
fq_put(fq_in, NULL);
return fq;
}
}
#endif
fq = fq_in;
if (!mod_timer(&fq->timer, jiffies + sysctl_ip6frag_time))
atomic_inc(&fq->refcnt);
atomic_inc(&fq->refcnt);
hlist_add_head(&fq->list, &ip6_frag_hash[hash]);
INIT_LIST_HEAD(&fq->lru_list);
list_add_tail(&fq->lru_list, &ip6_frag_lru_list);
ip6_frag_nqueues++;
write_unlock(&ip6_frag_lock);
return fq;
}
static struct frag_queue *
ip6_frag_create(unsigned int hash, u32 id, struct in6_addr *src, struct in6_addr *dst)
{
struct frag_queue *fq;
if ((fq = frag_alloc_queue()) == NULL)
goto oom;
memset(fq, 0, sizeof(struct frag_queue));
fq->id = id;
ipv6_addr_copy(&fq->saddr, src);
ipv6_addr_copy(&fq->daddr, dst);
init_timer(&fq->timer);
fq->timer.function = ip6_frag_expire;
fq->timer.data = (long) fq;
spin_lock_init(&fq->lock);
atomic_set(&fq->refcnt, 1);
return ip6_frag_intern(hash, fq);
oom:
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
return NULL;
}
static __inline__ struct frag_queue *
fq_find(u32 id, struct in6_addr *src, struct in6_addr *dst)
{
struct frag_queue *fq;
struct hlist_node *n;
unsigned int hash = ip6qhashfn(id, src, dst);
read_lock(&ip6_frag_lock);
hlist_for_each_entry(fq, n, &ip6_frag_hash[hash], list) {
if (fq->id == id &&
ipv6_addr_equal(src, &fq->saddr) &&
ipv6_addr_equal(dst, &fq->daddr)) {
atomic_inc(&fq->refcnt);
read_unlock(&ip6_frag_lock);
return fq;
}
}
read_unlock(&ip6_frag_lock);
return ip6_frag_create(hash, id, src, dst);
}
static void ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
struct frag_hdr *fhdr, int nhoff)
{
struct sk_buff *prev, *next;
int offset, end;
if (fq->last_in & COMPLETE)
goto err;
offset = ntohs(fhdr->frag_off) & ~0x7;
end = offset + (ntohs(skb->nh.ipv6h->payload_len) -
((u8 *) (fhdr + 1) - (u8 *) (skb->nh.ipv6h + 1)));
if ((unsigned int)end > IPV6_MAXPLEN) {
IP6_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb,ICMPV6_HDR_FIELD, (u8*)&fhdr->frag_off - skb->nh.raw);
return;
}
if (skb->ip_summed == CHECKSUM_HW)
skb->csum = csum_sub(skb->csum,
csum_partial(skb->nh.raw, (u8*)(fhdr+1)-skb->nh.raw, 0));
/* Is this the final fragment? */
if (!(fhdr->frag_off & htons(IP6_MF))) {
/* If we already have some bits beyond end
* or have different end, the segment is corrupted.
*/
if (end < fq->len ||
((fq->last_in & LAST_IN) && end != fq->len))
goto err;
fq->last_in |= LAST_IN;
fq->len = end;
} else {
/* Check if the fragment is rounded to 8 bytes.
* Required by the RFC.
*/
if (end & 0x7) {
/* RFC2460 says always send parameter problem in
* this case. -DaveM
*/
IP6_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
offsetof(struct ipv6hdr, payload_len));
return;
}
if (end > fq->len) {
/* Some bits beyond end -> corruption. */
if (fq->last_in & LAST_IN)
goto err;
fq->len = end;
}
}
if (end == offset)
goto err;
/* Point into the IP datagram 'data' part. */
if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data))
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 = fq->fragments; next != NULL; next = next->next) {
if (FRAG6_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 = (FRAG6_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;
}
}
/* Look for overlap with succeeding segments.
* If we can merge fragments, do it.
*/
while (next && FRAG6_CB(next)->offset < end) {
int i = end - FRAG6_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;
FRAG6_CB(next)->offset += i; /* next fragment */
fq->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
fq->fragments = next;
fq->meat -= free_it->len;
frag_kfree_skb(free_it, NULL);
}
}
FRAG6_CB(skb)->offset = offset;
/* Insert this fragment in the chain of fragments. */
skb->next = next;
if (prev)
prev->next = skb;
else
fq->fragments = skb;
if (skb->dev)
fq->iif = skb->dev->ifindex;
skb->dev = NULL;
skb_get_timestamp(skb, &fq->stamp);
fq->meat += skb->len;
atomic_add(skb->truesize, &ip6_frag_mem);
/* The first fragment.
* nhoffset is obtained from the first fragment, of course.
*/
if (offset == 0) {
fq->nhoffset = nhoff;
fq->last_in |= FIRST_IN;
}
write_lock(&ip6_frag_lock);
list_move_tail(&fq->lru_list, &ip6_frag_lru_list);
write_unlock(&ip6_frag_lock);
return;
err:
IP6_INC_STATS(IPSTATS_MIB_REASMFAILS);
kfree_skb(skb);
}
/*
* Check if this packet is complete.
* Returns NULL on failure by any reason, and pointer
* to current nexthdr field in reassembled frame.
*
* It is called with locked fq, and caller must check that
* queue is eligible for reassembly i.e. it is not COMPLETE,
* the last and the first frames arrived and all the bits are here.
*/
static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff **skb_in,
unsigned int *nhoffp,
struct net_device *dev)
{
struct sk_buff *fp, *head = fq->fragments;
int payload_len;
unsigned int nhoff;
fq_kill(fq);
BUG_TRAP(head != NULL);
BUG_TRAP(FRAG6_CB(head)->offset == 0);
/* Unfragmented part is taken from the first segment. */
payload_len = (head->data - head->nh.raw) - sizeof(struct ipv6hdr) + fq->len - sizeof(struct frag_hdr);
if (payload_len > IPV6_MAXPLEN)
goto out_oversize;
/* Head of list must not be cloned. */
if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
goto out_oom;
/* 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_oom;
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, &ip6_frag_mem);
}
/* We have to remove fragment header from datagram and to relocate
* header in order to calculate ICV correctly. */
nhoff = fq->nhoffset;
head->nh.raw[nhoff] = head->h.raw[0];
memmove(head->head + sizeof(struct frag_hdr), head->head,
(head->data - head->head) - sizeof(struct frag_hdr));
head->mac.raw += sizeof(struct frag_hdr);
head->nh.raw += sizeof(struct frag_hdr);
skb_shinfo(head)->frag_list = head->next;
head->h.raw = head->data;
skb_push(head, head->data - head->nh.raw);
atomic_sub(head->truesize, &ip6_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_HW)
head->csum = csum_add(head->csum, fp->csum);
head->truesize += fp->truesize;
atomic_sub(fp->truesize, &ip6_frag_mem);
}
head->next = NULL;
head->dev = dev;
skb_set_timestamp(head, &fq->stamp);
head->nh.ipv6h->payload_len = htons(payload_len);
*skb_in = head;
/* Yes, and fold redundant checksum back. 8) */
if (head->ip_summed == CHECKSUM_HW)
head->csum = csum_partial(head->nh.raw, head->h.raw-head->nh.raw, head->csum);
IP6_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
fq->fragments = NULL;
*nhoffp = nhoff;
return 1;
out_oversize:
if (net_ratelimit())
printk(KERN_DEBUG "ip6_frag_reasm: payload len = %d\n", payload_len);
goto out_fail;
out_oom:
if (net_ratelimit())
printk(KERN_DEBUG "ip6_frag_reasm: no memory for reassembly\n");
out_fail:
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
return -1;
}
static int ipv6_frag_rcv(struct sk_buff **skbp, unsigned int *nhoffp)
{
struct sk_buff *skb = *skbp;
struct net_device *dev = skb->dev;
struct frag_hdr *fhdr;
struct frag_queue *fq;
struct ipv6hdr *hdr;
hdr = skb->nh.ipv6h;
IP6_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
/* Jumbo payload inhibits frag. header */
if (hdr->payload_len==0) {
IP6_INC_STATS(IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb->h.raw-skb->nh.raw);
return -1;
}
if (!pskb_may_pull(skb, (skb->h.raw-skb->data)+sizeof(struct frag_hdr))) {
IP6_INC_STATS(IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, skb->h.raw-skb->nh.raw);
return -1;
}
hdr = skb->nh.ipv6h;
fhdr = (struct frag_hdr *)skb->h.raw;
if (!(fhdr->frag_off & htons(0xFFF9))) {
/* It is not a fragmented frame */
skb->h.raw += sizeof(struct frag_hdr);
IP6_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
*nhoffp = (u8*)fhdr - skb->nh.raw;
return 1;
}
if (atomic_read(&ip6_frag_mem) > sysctl_ip6frag_high_thresh)
ip6_evictor();
if ((fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr)) != NULL) {
int ret = -1;
spin_lock(&fq->lock);
ip6_frag_queue(fq, skb, fhdr, *nhoffp);
if (fq->last_in == (FIRST_IN|LAST_IN) &&
fq->meat == fq->len)
ret = ip6_frag_reasm(fq, skbp, nhoffp, dev);
spin_unlock(&fq->lock);
fq_put(fq, NULL);
return ret;
}
IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
kfree_skb(skb);
return -1;
}
static struct inet6_protocol frag_protocol =
{
.handler = ipv6_frag_rcv,
.flags = INET6_PROTO_NOPOLICY,
};
void __init ipv6_frag_init(void)
{
if (inet6_add_protocol(&frag_protocol, IPPROTO_FRAGMENT) < 0)
printk(KERN_ERR "ipv6_frag_init: Could not register protocol\n");
ip6_frag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
(jiffies ^ (jiffies >> 6)));
init_timer(&ip6_frag_secret_timer);
ip6_frag_secret_timer.function = ip6_frag_secret_rebuild;
ip6_frag_secret_timer.expires = jiffies + sysctl_ip6frag_secret_interval;
add_timer(&ip6_frag_secret_timer);
}
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