// SPDX-License-Identifier: GPL-2.0-or-later
/*
* IPv6 fragment reassembly for connection tracking
*
* Copyright (C)2004 USAGI/WIDE Project
*
* Author:
* Yasuyuki Kozakai @USAGI <[email protected]>
*
* Based on: net/ipv6/reassembly.c
*/
#define pr_fmt(fmt) "IPv6-nf: " fmt
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/ipv6.h>
#include <linux/slab.h>
#include <net/ipv6_frag.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>
#include <net/netns/generic.h>
static const char nf_frags_cache_name[] = "nf-frags";
static unsigned int nf_frag_pernet_id __read_mostly;
static struct inet_frags nf_frags;
static struct nft_ct_frag6_pernet *nf_frag_pernet(struct net *net)
{
return net_generic(net, nf_frag_pernet_id);
}
#ifdef CONFIG_SYSCTL
static struct ctl_table nf_ct_frag6_sysctl_table[] = {
{
.procname = "nf_conntrack_frag6_timeout",
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
{
.procname = "nf_conntrack_frag6_low_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{
.procname = "nf_conntrack_frag6_high_thresh",
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
};
static int nf_ct_frag6_sysctl_register(struct net *net)
{
struct nft_ct_frag6_pernet *nf_frag;
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;
}
nf_frag = nf_frag_pernet(net);
table[0].data = &nf_frag->fqdir->timeout;
table[1].data = &nf_frag->fqdir->low_thresh;
table[1].extra2 = &nf_frag->fqdir->high_thresh;
table[2].data = &nf_frag->fqdir->high_thresh;
table[2].extra1 = &nf_frag->fqdir->low_thresh;
hdr = register_net_sysctl_sz(net, "net/netfilter", table,
ARRAY_SIZE(nf_ct_frag6_sysctl_table));
if (hdr == NULL)
goto err_reg;
nf_frag->nf_frag_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 nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
const struct ctl_table *table;
table = nf_frag->nf_frag_frags_hdr->ctl_table_arg;
unregister_net_sysctl_table(nf_frag->nf_frag_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 int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev);
static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
{
return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
}
static void nf_ct_frag6_expire(struct timer_list *t)
{
struct inet_frag_queue *frag = from_timer(frag, t, timer);
struct frag_queue *fq;
fq = container_of(frag, struct frag_queue, q);
ip6frag_expire_frag_queue(fq->q.fqdir->net, fq);
}
/* Creation primitives. */
static struct frag_queue *fq_find(struct net *net, __be32 id, u32 user,
const struct ipv6hdr *hdr, int iif)
{
struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
struct frag_v6_compare_key key = {
.id = id,
.saddr = hdr->saddr,
.daddr = hdr->daddr,
.user = user,
.iif = iif,
};
struct inet_frag_queue *q;
if (!(ipv6_addr_type(&hdr->daddr) & (IPV6_ADDR_MULTICAST |
IPV6_ADDR_LINKLOCAL)))
key.iif = 0;
q = inet_frag_find(nf_frag->fqdir, &key);
if (!q)
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)
{
unsigned int payload_len;
struct net_device *dev;
struct sk_buff *prev;
int offset, end, err;
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);
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;
}
/* Note : skb->rbnode and skb->dev share the same location. */
dev = skb->dev;
/* Makes sure compiler wont do silly aliasing games */
barrier();
prev = fq->q.fragments_tail;
err = inet_frag_queue_insert(&fq->q, skb, offset, end);
if (err) {
if (err == IPFRAG_DUP) {
/* No error for duplicates, pretend they got queued. */
kfree_skb_reason(skb, SKB_DROP_REASON_DUP_FRAG);
return -EINPROGRESS;
}
goto insert_error;
}
if (dev)
fq->iif = dev->ifindex;
fq->q.stamp = skb->tstamp;
fq->q.tstamp_type = skb->tstamp_type;
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.fqdir, 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;
}
if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
fq->q.meat == fq->q.len) {
unsigned long orefdst = skb->_skb_refdst;
skb->_skb_refdst = 0UL;
err = nf_ct_frag6_reasm(fq, skb, prev, dev);
skb->_skb_refdst = orefdst;
/* After queue has assumed skb ownership, only 0 or
* -EINPROGRESS must be returned.
*/
return err ? -EINPROGRESS : 0;
}
skb_dst_drop(skb);
skb_orphan(skb);
return -EINPROGRESS;
insert_error:
inet_frag_kill(&fq->q);
err:
skb_dst_drop(skb);
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.
*/
static int nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail, struct net_device *dev)
{
void *reasm_data;
int payload_len;
u8 ecn;
inet_frag_kill(&fq->q);
ecn = ip_frag_ecn_table[fq->ecn];
if (unlikely(ecn == 0xff))
goto err;
reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
if (!reasm_data)
goto err;
payload_len = -skb_network_offset(skb) -
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);
goto err;
}
/* We have to remove fragment header from datagram and to relocate
* header in order to calculate ICV correctly. */
skb_network_header(skb)[fq->nhoffset] = skb_transport_header(skb)[0];
memmove(skb->head + sizeof(struct frag_hdr), skb->head,
(skb->data - skb->head) - sizeof(struct frag_hdr));
skb->mac_header += sizeof(struct frag_hdr);
skb->network_header += sizeof(struct frag_hdr);
skb_reset_transport_header(skb);
inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
skb->ignore_df = 1;
skb->dev = dev;
ipv6_hdr(skb)->payload_len = htons(payload_len);
ipv6_change_dsfield(ipv6_hdr(skb), 0xff, ecn);
IP6CB(skb)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
/* Yes, and fold redundant checksum back. 8) */
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_partial(skb_network_header(skb),
skb_network_header_len(skb),
skb->csum);
fq->q.rb_fragments = RB_ROOT;
fq->q.fragments_tail = NULL;
fq->q.last_run_head = NULL;
return 0;
err:
inet_frag_kill(&fq->q);
return -EINVAL;
}
/*
* 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 = ipv6_authlen(&hdr);
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;
u8 nexthdr = NEXTHDR_FRAGMENT;
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;
/* Discard the first fragment if it does not include all headers
* RFC 8200, Section 4.5
*/
if (ipv6frag_thdr_truncated(skb, fhoff, &nexthdr)) {
pr_debug("Drop incomplete fragment\n");
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);
fq = fq_find(net, fhdr->identification, user, hdr,
skb->dev ? skb->dev->ifindex : 0);
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 == -EPROTO) {
skb->transport_header = savethdr;
ret = 0;
}
spin_unlock_bh(&fq->q.lock);
inet_frag_put(&fq->q);
return ret;
}
EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
static int nf_ct_net_init(struct net *net)
{
struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
int res;
res = fqdir_init(&nf_frag->fqdir, &nf_frags, net);
if (res < 0)
return res;
nf_frag->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
nf_frag->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
nf_frag->fqdir->timeout = IPV6_FRAG_TIMEOUT;
res = nf_ct_frag6_sysctl_register(net);
if (res < 0)
fqdir_exit(nf_frag->fqdir);
return res;
}
static void nf_ct_net_pre_exit(struct net *net)
{
struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
fqdir_pre_exit(nf_frag->fqdir);
}
static void nf_ct_net_exit(struct net *net)
{
struct nft_ct_frag6_pernet *nf_frag = nf_frag_pernet(net);
nf_ct_frags6_sysctl_unregister(net);
fqdir_exit(nf_frag->fqdir);
}
static struct pernet_operations nf_ct_net_ops = {
.init = nf_ct_net_init,
.pre_exit = nf_ct_net_pre_exit,
.exit = nf_ct_net_exit,
.id = &nf_frag_pernet_id,
.size = sizeof(struct nft_ct_frag6_pernet),
};
static const struct rhashtable_params nfct_rhash_params = {
.head_offset = offsetof(struct inet_frag_queue, node),
.hashfn = ip6frag_key_hashfn,
.obj_hashfn = ip6frag_obj_hashfn,
.obj_cmpfn = ip6frag_obj_cmpfn,
.automatic_shrinking = true,
};
int nf_ct_frag6_init(void)
{
int ret = 0;
nf_frags.constructor = ip6frag_init;
nf_frags.destructor = NULL;
nf_frags.qsize = sizeof(struct frag_queue);
nf_frags.frag_expire = nf_ct_frag6_expire;
nf_frags.frags_cache_name = nf_frags_cache_name;
nf_frags.rhash_params = nfct_rhash_params;
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);
}
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