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DEFINITIONS
This source file includes following definitions.
- nf_hashfn
- nf_skb_free
- frag_kfree_skb
- fq_put
- fq_kill
- nf_ct_frag6_evictor
- nf_ct_frag6_expire
- fq_find
- nf_ct_frag6_queue
- nf_ct_frag6_reasm
- find_prev_fhdr
- nf_ct_frag6_gather
- nf_ct_frag6_output
- nf_ct_frag6_init
- nf_ct_frag6_cleanup
/*
* IPv6 fragment reassembly for connection tracking
*
* Copyright (C)2004 USAGI/WIDE Project
*
* Author:
* Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
*
* Based on: net/ipv6/reassembly.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.
*/
#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 <net/sock.h>
#include <net/snmp.h>
#include <net/inet_frag.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>
#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
#include <linux/sysctl.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <linux/kernel.h>
#include <linux/module.h>
#define NF_CT_FRAG6_HIGH_THRESH 262144 /* == 256*1024 */
#define NF_CT_FRAG6_LOW_THRESH 196608 /* == 192*1024 */
#define NF_CT_FRAG6_TIMEOUT IPV6_FRAG_TIMEOUT
struct nf_ct_frag6_skb_cb
{
struct inet6_skb_parm h;
int offset;
struct sk_buff *orig;
};
#define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb*)((skb)->cb))
struct nf_ct_frag6_queue
{
struct inet_frag_queue q;
__be32 id; /* fragment id */
struct in6_addr saddr;
struct in6_addr daddr;
unsigned int csum;
__u16 nhoffset;
};
static struct inet_frags nf_frags;
static struct netns_frags nf_init_frags;
#ifdef CONFIG_SYSCTL
struct ctl_table nf_ct_ipv6_sysctl_table[] = {
{
.procname = "nf_conntrack_frag6_timeout",
.data = &nf_init_frags.timeout,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec_jiffies,
},
{
.ctl_name = NET_NF_CONNTRACK_FRAG6_LOW_THRESH,
.procname = "nf_conntrack_frag6_low_thresh",
.data = &nf_init_frags.low_thresh,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = NET_NF_CONNTRACK_FRAG6_HIGH_THRESH,
.procname = "nf_conntrack_frag6_high_thresh",
.data = &nf_init_frags.high_thresh,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{ .ctl_name = 0 }
};
#endif
static unsigned int nf_hashfn(struct inet_frag_queue *q)
{
const struct nf_ct_frag6_queue *nq;
nq = container_of(q, struct nf_ct_frag6_queue, q);
return inet6_hash_frag(nq->id, &nq->saddr, &nq->daddr, nf_frags.rnd);
}
static void nf_skb_free(struct sk_buff *skb)
{
if (NFCT_FRAG6_CB(skb)->orig)
kfree_skb(NFCT_FRAG6_CB(skb)->orig);
}
/* Memory Tracking Functions. */
static inline void frag_kfree_skb(struct sk_buff *skb, unsigned int *work)
{
if (work)
*work -= skb->truesize;
atomic_sub(skb->truesize, &nf_init_frags.mem);
nf_skb_free(skb);
kfree_skb(skb);
}
/* Destruction primitives. */
static __inline__ void fq_put(struct nf_ct_frag6_queue *fq)
{
inet_frag_put(&fq->q, &nf_frags);
}
/* Kill fq entry. It is not destroyed immediately,
* because caller (and someone more) holds reference count.
*/
static __inline__ void fq_kill(struct nf_ct_frag6_queue *fq)
{
inet_frag_kill(&fq->q, &nf_frags);
}
static void nf_ct_frag6_evictor(void)
{
local_bh_disable();
inet_frag_evictor(&nf_init_frags, &nf_frags);
local_bh_enable();
}
static void nf_ct_frag6_expire(unsigned long data)
{
struct nf_ct_frag6_queue *fq;
fq = container_of((struct inet_frag_queue *)data,
struct nf_ct_frag6_queue, q);
spin_lock(&fq->q.lock);
if (fq->q.last_in & INET_FRAG_COMPLETE)
goto out;
fq_kill(fq);
out:
spin_unlock(&fq->q.lock);
fq_put(fq);
}
/* Creation primitives. */
static __inline__ struct nf_ct_frag6_queue *
fq_find(__be32 id, struct in6_addr *src, struct in6_addr *dst)
{
struct inet_frag_queue *q;
struct ip6_create_arg arg;
unsigned int hash;
arg.id = id;
arg.src = src;
arg.dst = dst;
read_lock_bh(&nf_frags.lock);
hash = inet6_hash_frag(id, src, dst, nf_frags.rnd);
q = inet_frag_find(&nf_init_frags, &nf_frags, &arg, hash);
local_bh_enable();
if (q == NULL)
goto oom;
return container_of(q, struct nf_ct_frag6_queue, q);
oom:
pr_debug("Can't alloc new queue\n");
return NULL;
}
static int nf_ct_frag6_queue(struct nf_ct_frag6_queue *fq, struct sk_buff *skb,
const struct frag_hdr *fhdr, int nhoff)
{
struct sk_buff *prev, *next;
int offset, end;
if (fq->q.last_in & INET_FRAG_COMPLETE) {
pr_debug("Allready completed\n");
goto err;
}
offset = ntohs(fhdr->frag_off) & ~0x7;
end = offset + (ntohs(ipv6_hdr(skb)->payload_len) -
((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
if ((unsigned int)end > IPV6_MAXPLEN) {
pr_debug("offset is too large.\n");
return -1;
}
if (skb->ip_summed == CHECKSUM_COMPLETE) {
const unsigned char *nh = skb_network_header(skb);
skb->csum = csum_sub(skb->csum,
csum_partial(nh, (u8 *)(fhdr + 1) - nh,
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->q.len ||
((fq->q.last_in & INET_FRAG_LAST_IN) && end != fq->q.len)) {
pr_debug("already received last fragment\n");
goto err;
}
fq->q.last_in |= INET_FRAG_LAST_IN;
fq->q.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
*/
pr_debug("end of fragment not rounded to 8 bytes.\n");
return -1;
}
if (end > fq->q.len) {
/* Some bits beyond end -> corruption. */
if (fq->q.last_in & INET_FRAG_LAST_IN) {
pr_debug("last packet already reached.\n");
goto err;
}
fq->q.len = end;
}
}
if (end == offset)
goto err;
/* Point into the IP datagram 'data' part. */
if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
pr_debug("queue: message is too short.\n");
goto err;
}
if (pskb_trim_rcsum(skb, end - offset)) {
pr_debug("Can't trim\n");
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->q.fragments; next != NULL; next = next->next) {
if (NFCT_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 = (NFCT_FRAG6_CB(prev)->offset + prev->len) - offset;
if (i > 0) {
offset += i;
if (end <= offset) {
pr_debug("overlap\n");
goto err;
}
if (!pskb_pull(skb, i)) {
pr_debug("Can't pull\n");
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 && NFCT_FRAG6_CB(next)->offset < end) {
/* overlap is 'i' bytes */
int i = end - NFCT_FRAG6_CB(next)->offset;
if (i < next->len) {
/* Eat head of the next overlapped fragment
* and leave the loop. The next ones cannot overlap.
*/
pr_debug("Eat head of the overlapped parts.: %d", i);
if (!pskb_pull(next, i))
goto err;
/* next fragment */
NFCT_FRAG6_CB(next)->offset += i;
fq->q.meat -= i;
if (next->ip_summed != CHECKSUM_UNNECESSARY)
next->ip_summed = CHECKSUM_NONE;
break;
} else {
struct sk_buff *free_it = next;
/* Old fragmnet is completely overridden with
* new one drop it.
*/
next = next->next;
if (prev)
prev->next = next;
else
fq->q.fragments = next;
fq->q.meat -= free_it->len;
frag_kfree_skb(free_it, NULL);
}
}
NFCT_FRAG6_CB(skb)->offset = offset;
/* Insert this fragment in the chain of fragments. */
skb->next = next;
if (prev)
prev->next = skb;
else
fq->q.fragments = skb;
skb->dev = NULL;
fq->q.stamp = skb->tstamp;
fq->q.meat += skb->len;
atomic_add(skb->truesize, &nf_init_frags.mem);
/* The first fragment.
* nhoffset is obtained from the first fragment, of course.
*/
if (offset == 0) {
fq->nhoffset = nhoff;
fq->q.last_in |= INET_FRAG_FIRST_IN;
}
write_lock(&nf_frags.lock);
list_move_tail(&fq->q.lru_list, &nf_init_frags.lru_list);
write_unlock(&nf_frags.lock);
return 0;
err:
return -1;
}
/*
* 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 struct sk_buff *
nf_ct_frag6_reasm(struct nf_ct_frag6_queue *fq, struct net_device *dev)
{
struct sk_buff *fp, *op, *head = fq->q.fragments;
int payload_len;
fq_kill(fq);
WARN_ON(head == NULL);
WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
/* Unfragmented part is taken from the first segment. */
payload_len = ((head->data - skb_network_header(head)) -
sizeof(struct ipv6hdr) + fq->q.len -
sizeof(struct frag_hdr));
if (payload_len > IPV6_MAXPLEN) {
pr_debug("payload len is too large.\n");
goto out_oversize;
}
/* Head of list must not be cloned. */
if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC)) {
pr_debug("skb is cloned but can't expand head");
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) {
pr_debug("Can't alloc skb\n");
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;
NFCT_FRAG6_CB(clone)->orig = NULL;
atomic_add(clone->truesize, &nf_init_frags.mem);
}
/* We have to remove fragment header from datagram and to relocate
* header in order to calculate ICV correctly. */
skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
memmove(head->head + sizeof(struct frag_hdr), head->head,
(head->data - head->head) - sizeof(struct frag_hdr));
head->mac_header += sizeof(struct frag_hdr);
head->network_header += sizeof(struct frag_hdr);
skb_shinfo(head)->frag_list = head->next;
skb_reset_transport_header(head);
skb_push(head, head->data - skb_network_header(head));
atomic_sub(head->truesize, &nf_init_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, &nf_init_frags.mem);
}
head->next = NULL;
head->dev = dev;
head->tstamp = fq->q.stamp;
ipv6_hdr(head)->payload_len = htons(payload_len);
/* Yes, and fold redundant checksum back. 8) */
if (head->ip_summed == CHECKSUM_COMPLETE)
head->csum = csum_partial(skb_network_header(head),
skb_network_header_len(head),
head->csum);
fq->q.fragments = NULL;
/* all original skbs are linked into the NFCT_FRAG6_CB(head).orig */
fp = skb_shinfo(head)->frag_list;
if (NFCT_FRAG6_CB(fp)->orig == NULL)
/* at above code, head skb is divided into two skbs. */
fp = fp->next;
op = NFCT_FRAG6_CB(head)->orig;
for (; fp; fp = fp->next) {
struct sk_buff *orig = NFCT_FRAG6_CB(fp)->orig;
op->next = orig;
op = orig;
NFCT_FRAG6_CB(fp)->orig = NULL;
}
return head;
out_oversize:
if (net_ratelimit())
printk(KERN_DEBUG "nf_ct_frag6_reasm: payload len = %d\n", payload_len);
goto out_fail;
out_oom:
if (net_ratelimit())
printk(KERN_DEBUG "nf_ct_frag6_reasm: no memory for reassembly\n");
out_fail:
return NULL;
}
/*
* find the header just before Fragment Header.
*
* if success return 0 and set ...
* (*prevhdrp): the value of "Next Header Field" in the header
* just before Fragment Header.
* (*prevhoff): the offset of "Next Header Field" in the header
* just before Fragment Header.
* (*fhoff) : the offset of Fragment Header.
*
* Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
*
*/
static int
find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
{
u8 nexthdr = ipv6_hdr(skb)->nexthdr;
const int netoff = skb_network_offset(skb);
u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
int start = netoff + sizeof(struct ipv6hdr);
int len = skb->len - start;
u8 prevhdr = NEXTHDR_IPV6;
while (nexthdr != NEXTHDR_FRAGMENT) {
struct ipv6_opt_hdr hdr;
int hdrlen;
if (!ipv6_ext_hdr(nexthdr)) {
return -1;
}
if (len < (int)sizeof(struct ipv6_opt_hdr)) {
pr_debug("too short\n");
return -1;
}
if (nexthdr == NEXTHDR_NONE) {
pr_debug("next header is none\n");
return -1;
}
if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
BUG();
if (nexthdr == NEXTHDR_AUTH)
hdrlen = (hdr.hdrlen+2)<<2;
else
hdrlen = ipv6_optlen(&hdr);
prevhdr = nexthdr;
prev_nhoff = start;
nexthdr = hdr.nexthdr;
len -= hdrlen;
start += hdrlen;
}
if (len < 0)
return -1;
*prevhdrp = prevhdr;
*prevhoff = prev_nhoff;
*fhoff = start;
return 0;
}
struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb)
{
struct sk_buff *clone;
struct net_device *dev = skb->dev;
struct frag_hdr *fhdr;
struct nf_ct_frag6_queue *fq;
struct ipv6hdr *hdr;
int fhoff, nhoff;
u8 prevhdr;
struct sk_buff *ret_skb = NULL;
/* Jumbo payload inhibits frag. header */
if (ipv6_hdr(skb)->payload_len == 0) {
pr_debug("payload len = 0\n");
return skb;
}
if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
return skb;
clone = skb_clone(skb, GFP_ATOMIC);
if (clone == NULL) {
pr_debug("Can't clone skb\n");
return skb;
}
NFCT_FRAG6_CB(clone)->orig = skb;
if (!pskb_may_pull(clone, fhoff + sizeof(*fhdr))) {
pr_debug("message is too short.\n");
goto ret_orig;
}
skb_set_transport_header(clone, fhoff);
hdr = ipv6_hdr(clone);
fhdr = (struct frag_hdr *)skb_transport_header(clone);
if (!(fhdr->frag_off & htons(0xFFF9))) {
pr_debug("Invalid fragment offset\n");
/* It is not a fragmented frame */
goto ret_orig;
}
if (atomic_read(&nf_init_frags.mem) > nf_init_frags.high_thresh)
nf_ct_frag6_evictor();
fq = fq_find(fhdr->identification, &hdr->saddr, &hdr->daddr);
if (fq == NULL) {
pr_debug("Can't find and can't create new queue\n");
goto ret_orig;
}
spin_lock_bh(&fq->q.lock);
if (nf_ct_frag6_queue(fq, clone, fhdr, nhoff) < 0) {
spin_unlock_bh(&fq->q.lock);
pr_debug("Can't insert skb to queue\n");
fq_put(fq);
goto ret_orig;
}
if (fq->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
fq->q.meat == fq->q.len) {
ret_skb = nf_ct_frag6_reasm(fq, dev);
if (ret_skb == NULL)
pr_debug("Can't reassemble fragmented packets\n");
}
spin_unlock_bh(&fq->q.lock);
fq_put(fq);
return ret_skb;
ret_orig:
kfree_skb(clone);
return skb;
}
void nf_ct_frag6_output(unsigned int hooknum, struct sk_buff *skb,
struct net_device *in, struct net_device *out,
int (*okfn)(struct sk_buff *))
{
struct sk_buff *s, *s2;
for (s = NFCT_FRAG6_CB(skb)->orig; s;) {
nf_conntrack_put_reasm(s->nfct_reasm);
nf_conntrack_get_reasm(skb);
s->nfct_reasm = skb;
s2 = s->next;
s->next = NULL;
NF_HOOK_THRESH(PF_INET6, hooknum, s, in, out, okfn,
NF_IP6_PRI_CONNTRACK_DEFRAG + 1);
s = s2;
}
nf_conntrack_put_reasm(skb);
}
int nf_ct_frag6_init(void)
{
nf_frags.hashfn = nf_hashfn;
nf_frags.constructor = ip6_frag_init;
nf_frags.destructor = NULL;
nf_frags.skb_free = nf_skb_free;
nf_frags.qsize = sizeof(struct nf_ct_frag6_queue);
nf_frags.match = ip6_frag_match;
nf_frags.frag_expire = nf_ct_frag6_expire;
nf_frags.secret_interval = 10 * 60 * HZ;
nf_init_frags.timeout = IPV6_FRAG_TIMEOUT;
nf_init_frags.high_thresh = 256 * 1024;
nf_init_frags.low_thresh = 192 * 1024;
inet_frags_init_net(&nf_init_frags);
inet_frags_init(&nf_frags);
return 0;
}
void nf_ct_frag6_cleanup(void)
{
inet_frags_fini(&nf_frags);
nf_init_frags.low_thresh = 0;
nf_ct_frag6_evictor();
}