/*
* 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.
*/
#define pr_fmt(fmt) "IPv6-nf: " fmt
#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/slab.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/inet_ecn.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>
#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
static const char nf_frags_cache_name[] = "nf-frags";
struct nf_ct_frag6_skb_cb
{
struct inet6_skb_parm h;
int offset;
};
#define NFCT_FRAG6_CB(skb) ((struct nf_ct_frag6_skb_cb *)((skb)->cb))
static struct inet_frags nf_frags;
#ifdef CONFIG_SYSCTL
static int zero;
static struct ctl_table nf_ct_frag6_sysctl_table[] = {
{
.procname = "nf_conntrack_frag6_timeout",
.data = &init_net.nf_frag.frags.timeout,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
{
.procname = "nf_conntrack_frag6_low_thresh",
.data = &init_net.nf_frag.frags.low_thresh,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
.extra2 = &init_net.nf_frag.frags.high_thresh
},
{
.procname = "nf_conntrack_frag6_high_thresh",
.data = &init_net.nf_frag.frags.high_thresh,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &init_net.nf_frag.frags.low_thresh
},
{ }
};
static int nf_ct_frag6_sysctl_register(struct net *net)
{
struct ctl_table *table;
struct ctl_table_header *hdr;
table = nf_ct_frag6_sysctl_table;
if (!net_eq(net, &init_net)) {
table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
GFP_KERNEL);
if (table == NULL)
goto err_alloc;
table[0].data = &net->nf_frag.frags.timeout;
table[1].data = &net->nf_frag.frags.low_thresh;
table[1].extra2 = &net->nf_frag.frags.high_thresh;
table[2].data = &net->nf_frag.frags.high_thresh;
table[2].extra1 = &net->nf_frag.frags.low_thresh;
table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
}
hdr = register_net_sysctl(net, "net/netfilter", table);
if (hdr == NULL)
goto err_reg;
net->nf_frag.sysctl.frags_hdr = hdr;
return 0;
err_reg:
if (!net_eq(net, &init_net))
kfree(table);
err_alloc:
return -ENOMEM;
}
static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
{
struct ctl_table *table;
table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg;
unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr);
if (!net_eq(net, &init_net))
kfree(table);
}
#else
static int nf_ct_frag6_sysctl_register(struct net *net)
{
return 0;
}
static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
{
}
#endif
static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
{
return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
}
static unsigned int nf_hash_frag(__be32 id, const struct in6_addr *saddr,
const struct in6_addr *daddr)
{
net_get_random_once(&nf_frags.rnd, sizeof(nf_frags.rnd));
return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr),
(__force u32)id, nf_frags.rnd);
}
static unsigned int nf_hashfn(const struct inet_frag_queue *q)
{
const struct frag_queue *nq;
nq = container_of(q, struct frag_queue, q);
return nf_hash_frag(nq->id, &nq->saddr, &nq->daddr);
}
static void nf_ct_frag6_expire(struct timer_list *t)
{
struct inet_frag_queue *frag = from_timer(frag, t, timer);
struct frag_queue *fq;
struct net *net;
fq = container_of(frag, struct frag_queue, q);
net = container_of(fq->q.net, struct net, nf_frag.frags);
ip6_expire_frag_queue(net, fq, &nf_frags);
}
/* Creation primitives. */
static inline struct frag_queue *fq_find(struct net *net, __be32 id,
u32 user, struct in6_addr *src,
struct in6_addr *dst, int iif, u8 ecn)
{
struct inet_frag_queue *q;
struct ip6_create_arg arg;
unsigned int hash;
arg.id = id;
arg.user = user;
arg.src = src;
arg.dst = dst;
arg.iif = iif;
arg.ecn = ecn;
local_bh_disable();
hash = nf_hash_frag(id, src, dst);
q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash);
local_bh_enable();
if (IS_ERR_OR_NULL(q)) {
inet_frag_maybe_warn_overflow(q, pr_fmt());
return NULL;
}
return container_of(q, struct frag_queue, q);
}
static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
const struct frag_hdr *fhdr, int nhoff)
{
struct sk_buff *prev, *next;
unsigned int payload_len;
int offset, end;
u8 ecn;
if (fq->q.flags & INET_FRAG_COMPLETE) {
pr_debug("Already completed\n");
goto err;
}
payload_len = ntohs(ipv6_hdr(skb)->payload_len);
offset = ntohs(fhdr->frag_off) & ~0x7;
end = offset + (payload_len -
((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
if ((unsigned int)end > IPV6_MAXPLEN) {
pr_debug("offset is too large.\n");
return -EINVAL;
}
ecn = ip6_frag_ecn(ipv6_hdr(skb));
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.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
pr_debug("already received last fragment\n");
goto err;
}
fq->q.flags |= 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");
inet_frag_kill(&fq->q, &nf_frags);
return -EPROTO;
}
if (end > fq->q.len) {
/* Some bits beyond end -> corruption. */
if (fq->q.flags & 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 = fq->q.fragments_tail;
if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) {
next = NULL;
goto found;
}
prev = NULL;
for (next = fq->q.fragments; next != NULL; next = next->next) {
if (NFCT_FRAG6_CB(next)->offset >= offset)
break; /* bingo! */
prev = next;
}
found:
/* RFC5722, Section 4:
* When reassembling an IPv6 datagram, if
* one or more its constituent fragments is determined to be an
* overlapping fragment, the entire datagram (and any constituent
* fragments, including those not yet received) MUST be silently
* discarded.
*/
/* Check for overlap with preceding fragment. */
if (prev &&
(NFCT_FRAG6_CB(prev)->offset + prev->len) > offset)
goto discard_fq;
/* Look for overlap with succeeding segment. */
if (next && NFCT_FRAG6_CB(next)->offset < end)
goto discard_fq;
NFCT_FRAG6_CB(skb)->offset = offset;
/* Insert this fragment in the chain of fragments. */
skb->next = next;
if (!next)
fq->q.fragments_tail = skb;
if (prev)
prev->next = skb;
else
fq->q.fragments = skb;
if (skb->dev) {
fq->iif = skb->dev->ifindex;
skb->dev = NULL;
}
fq->q.stamp = skb->tstamp;
fq->q.meat += skb->len;
fq->ecn |= ecn;
if (payload_len > fq->q.max_size)
fq->q.max_size = payload_len;
add_frag_mem_limit(fq->q.net, skb->truesize);
/* The first fragment.
* nhoffset is obtained from the first fragment, of course.
*/
if (offset == 0) {
fq->nhoffset = nhoff;
fq->q.flags |= INET_FRAG_FIRST_IN;
}
return 0;
discard_fq:
inet_frag_kill(&fq->q, &nf_frags);
err:
return -EINVAL;
}
/*
* Check if this packet is complete.
*
* 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.
*
* returns true if *prev skb has been transformed into the reassembled
* skb, false otherwise.
*/
static bool
nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *prev, struct net_device *dev)
{
struct sk_buff *fp, *head = fq->q.fragments;
int payload_len;
u8 ecn;
inet_frag_kill(&fq->q, &nf_frags);
WARN_ON(head == NULL);
WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
ecn = ip_frag_ecn_table[fq->ecn];
if (unlikely(ecn == 0xff))
return false;
/* 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) {
net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
payload_len);
return false;
}
/* Head of list must not be cloned. */
if (skb_unclone(head, GFP_ATOMIC))
return false;
/* 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_has_frag_list(head)) {
struct sk_buff *clone;
int i, plen = 0;
clone = alloc_skb(0, GFP_ATOMIC);
if (clone == NULL)
return false;
clone->next = head->next;
head->next = clone;
skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
skb_frag_list_init(head);
for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
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;
add_frag_mem_limit(fq->q.net, clone->truesize);
}
/* morph head into last received skb: prev.
*
* This allows callers of ipv6 conntrack defrag to continue
* to use the last skb(frag) passed into the reasm engine.
* The last skb frag 'silently' turns into the full reassembled skb.
*
* Since prev is also part of q->fragments we have to clone it first.
*/
if (head != prev) {
struct sk_buff *iter;
fp = skb_clone(prev, GFP_ATOMIC);
if (!fp)
return false;
fp->next = prev->next;
iter = head;
while (iter) {
if (iter->next == prev) {
iter->next = fp;
break;
}
iter = iter->next;
}
skb_morph(prev, head);
prev->next = head->next;
consume_skb(head);
head = prev;
}
/* 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));
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;
}
sub_frag_mem_limit(fq->q.net, head->truesize);
head->ignore_df = 1;
head->next = NULL;
head->dev = dev;
head->tstamp = fq->q.stamp;
ipv6_hdr(head)->payload_len = htons(payload_len);
ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);
IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
/* 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;
fq->q.fragments_tail = NULL;
return true;
}
/*
* 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 (nexthdr == NEXTHDR_NONE) {
pr_debug("next header is none\n");
return -1;
}
if (len < (int)sizeof(struct ipv6_opt_hdr)) {
pr_debug("too short\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;
}
int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
{
u16 savethdr = skb->transport_header;
struct net_device *dev = skb->dev;
int fhoff, nhoff, ret;
struct frag_hdr *fhdr;
struct frag_queue *fq;
struct ipv6hdr *hdr;
u8 prevhdr;
/* Jumbo payload inhibits frag. header */
if (ipv6_hdr(skb)->payload_len == 0) {
pr_debug("payload len = 0\n");
return 0;
}
if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
return 0;
if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
return -ENOMEM;
skb_set_transport_header(skb, fhoff);
hdr = ipv6_hdr(skb);
fhdr = (struct frag_hdr *)skb_transport_header(skb);
skb_orphan(skb);
fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr,
skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
if (fq == NULL) {
pr_debug("Can't find and can't create new queue\n");
return -ENOMEM;
}
spin_lock_bh(&fq->q.lock);
ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
if (ret < 0) {
if (ret == -EPROTO) {
skb->transport_header = savethdr;
ret = 0;
}
goto out_unlock;
}
/* after queue has assumed skb ownership, only 0 or -EINPROGRESS
* must be returned.
*/
ret = -EINPROGRESS;
if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
fq->q.meat == fq->q.len &&
nf_ct_frag6_reasm(fq, skb, dev))
ret = 0;
out_unlock:
spin_unlock_bh(&fq->q.lock);
inet_frag_put(&fq->q, &nf_frags);
return ret;
}
EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
static int nf_ct_net_init(struct net *net)
{
net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
inet_frags_init_net(&net->nf_frag.frags);
return nf_ct_frag6_sysctl_register(net);
}
static void nf_ct_net_exit(struct net *net)
{
nf_ct_frags6_sysctl_unregister(net);
inet_frags_exit_net(&net->nf_frag.frags, &nf_frags);
}
static struct pernet_operations nf_ct_net_ops = {
.init = nf_ct_net_init,
.exit = nf_ct_net_exit,
};
int nf_ct_frag6_init(void)
{
int ret = 0;
nf_frags.hashfn = nf_hashfn;
nf_frags.constructor = ip6_frag_init;
nf_frags.destructor = NULL;
nf_frags.qsize = sizeof(struct frag_queue);
nf_frags.match = ip6_frag_match;
nf_frags.frag_expire = nf_ct_frag6_expire;
nf_frags.frags_cache_name = nf_frags_cache_name;
ret = inet_frags_init(&nf_frags);
if (ret)
goto out;
ret = register_pernet_subsys(&nf_ct_net_ops);
if (ret)
inet_frags_fini(&nf_frags);
out:
return ret;
}
void nf_ct_frag6_cleanup(void)
{
unregister_pernet_subsys(&nf_ct_net_ops);
inet_frags_fini(&nf_frags);
}
