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netfilter: bridge: forward IPv6 fragmented packets
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IPv6 fragmented packets are not forwarded on an ethernet bridge
with netfilter ip6_tables loaded. e.g. steps to reproduce

1) create a simple bridge like this

        modprobe br_netfilter
        brctl addbr br0
        brctl addif br0 eth0
        brctl addif br0 eth2
        ifconfig eth0 up
        ifconfig eth2 up
        ifconfig br0 up

2) place a host with an IPv6 address on each side of the bridge

        set IPv6 address on host A:
        ip -6 addr add fd01:2345:6789:1::1/64 dev eth0

        set IPv6 address on host B:
        ip -6 addr add fd01:2345:6789:1::2/64 dev eth0

3) run a simple ping command on host A with packets > MTU

        ping6 -s 4000 fd01:2345:6789:1::2

4) wait some time and run e.g. "ip6tables -t nat -nvL" on the bridge

IPv6 fragmented packets traverse the bridge cleanly until somebody runs.
"ip6tables -t nat -nvL". As soon as it is run (and netfilter modules are
loaded) IPv6 fragmented packets do not traverse the bridge any more (you
see no more responses in ping's output).

After applying this patch IPv6 fragmented packets traverse the bridge
cleanly in above scenario.

Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at>
[pablo@netfilter.org: small changes to br_nf_dev_queue_xmit]
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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@bthaler @ummakynes
bthaler authored and ummakynes committed Jun 12, 2015
1 parent a4611d3 commit efb6de9
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Showing 4 changed files with 108 additions and 42 deletions.
2 changes: 2 additions & 0 deletions include/linux/netfilter_ipv6.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ struct nf_ipv6_ops {
int (*chk_addr)(struct net *net, const struct in6_addr *addr,
const struct net_device *dev, int strict);
void (*route_input)(struct sk_buff *skb);
int (*fragment)(struct sock *sk, struct sk_buff *skb,
int (*output)(struct sock *, struct sk_buff *));
};

extern const struct nf_ipv6_ops __rcu *nf_ipv6_ops;
Expand Down
139 changes: 99 additions & 40 deletions net/bridge/br_netfilter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@

#include <net/ip.h>
#include <net/ipv6.h>
#include <net/addrconf.h>
#include <net/route.h>
#include <net/netfilter/br_netfilter.h>

Expand Down Expand Up @@ -320,6 +321,55 @@ static int check_hbh_len(struct sk_buff *skb)
return -1;
}

/* Equivalent to br_validate_ipv4 for IPv6 */
static int br_validate_ipv6(struct sk_buff *skb)
{
const struct ipv6hdr *hdr;
struct net_device *dev = skb->dev;
struct inet6_dev *idev = in6_dev_get(skb->dev);
u32 pkt_len;
u8 ip6h_len = sizeof(struct ipv6hdr);

if (!pskb_may_pull(skb, ip6h_len))
goto inhdr_error;

if (skb->len < ip6h_len)
goto drop;

hdr = ipv6_hdr(skb);

if (hdr->version != 6)
goto inhdr_error;

pkt_len = ntohs(hdr->payload_len);

if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
if (pkt_len + ip6h_len > skb->len) {
IP6_INC_STATS_BH(dev_net(dev), idev,
IPSTATS_MIB_INTRUNCATEDPKTS);
goto drop;
}
if (pskb_trim_rcsum(skb, pkt_len + ip6h_len)) {
IP6_INC_STATS_BH(dev_net(dev), idev,
IPSTATS_MIB_INDISCARDS);
goto drop;
}
}
if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
goto drop;

memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
/* No IP options in IPv6 header; however it should be
* checked if some next headers need special treatment
*/
return 0;

inhdr_error:
IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
drop:
return -1;
}

static void nf_bridge_update_protocol(struct sk_buff *skb)
{
switch (skb->nf_bridge->orig_proto) {
Expand Down Expand Up @@ -405,6 +455,8 @@ static int br_nf_pre_routing_finish_ipv6(struct sock *sk, struct sk_buff *skb)
struct net_device *dev = skb->dev;
const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();

nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;

if (nf_bridge->pkt_otherhost) {
skb->pkt_type = PACKET_OTHERHOST;
nf_bridge->pkt_otherhost = false;
Expand Down Expand Up @@ -606,35 +658,15 @@ static struct net_device *setup_pre_routing(struct sk_buff *skb)
}

/* Replicate the checks that IPv6 does on packet reception and pass the packet
* to ip6tables, which doesn't support NAT, so things are fairly simple. */
* to ip6tables.
*/
static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct nf_bridge_info *nf_bridge;
const struct ipv6hdr *hdr;
u32 pkt_len;

if (skb->len < sizeof(struct ipv6hdr))
return NF_DROP;

if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
return NF_DROP;

hdr = ipv6_hdr(skb);

if (hdr->version != 6)
return NF_DROP;

pkt_len = ntohs(hdr->payload_len);

if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
return NF_DROP;
if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
return NF_DROP;
}
if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
if (br_validate_ipv6(skb))
return NF_DROP;

nf_bridge_put(skb->nf_bridge);
Expand Down Expand Up @@ -738,9 +770,11 @@ static int br_nf_forward_finish(struct sock *sk, struct sk_buff *skb)

if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {

if (skb->protocol == htons(ETH_P_IP)) {
if (skb->protocol == htons(ETH_P_IP))
nf_bridge->frag_max_size = IPCB(skb)->frag_max_size;
}

if (skb->protocol == htons(ETH_P_IPV6))
nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;

in = nf_bridge->physindev;
if (nf_bridge->pkt_otherhost) {
Expand Down Expand Up @@ -808,6 +842,12 @@ static unsigned int br_nf_forward_ip(const struct nf_hook_ops *ops,
IPCB(skb)->frag_max_size = nf_bridge->frag_max_size;
}

if (pf == NFPROTO_IPV6) {
if (br_validate_ipv6(skb))
return NF_DROP;
IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;
}

nf_bridge->physoutdev = skb->dev;
if (pf == NFPROTO_IPV4)
skb->protocol = htons(ETH_P_IP);
Expand Down Expand Up @@ -855,7 +895,7 @@ static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
return NF_STOLEN;
}

#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
static int br_nf_push_frag_xmit(struct sock *sk, struct sk_buff *skb)
{
struct brnf_frag_data *data;
Expand All @@ -875,6 +915,7 @@ static int br_nf_push_frag_xmit(struct sock *sk, struct sk_buff *skb)
nf_bridge_info_free(skb);
return br_dev_queue_push_xmit(sk, skb);
}
#endif

static int br_nf_ip_fragment(struct sock *sk, struct sk_buff *skb,
int (*output)(struct sock *, struct sk_buff *))
Expand All @@ -897,21 +938,23 @@ static int br_nf_ip_fragment(struct sock *sk, struct sk_buff *skb,

static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
{
int ret;
struct nf_bridge_info *nf_bridge;
unsigned int mtu_reserved;

if (skb_is_gso(skb) || skb->protocol != htons(ETH_P_IP)) {
mtu_reserved = nf_bridge_mtu_reduction(skb);

if (skb_is_gso(skb) || skb->len + mtu_reserved <= skb->dev->mtu) {
nf_bridge_info_free(skb);
return br_dev_queue_push_xmit(sk, skb);
}

mtu_reserved = nf_bridge_mtu_reduction(skb);
nf_bridge = nf_bridge_info_get(skb);

#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
/* This is wrong! We should preserve the original fragment
* boundaries by preserving frag_list rather than refragmenting.
*/
if (skb->len + mtu_reserved > skb->dev->mtu) {
if (skb->protocol == htons(ETH_P_IP)) {
struct brnf_frag_data *data;

if (br_validate_ipv4(skb))
Expand All @@ -928,21 +971,37 @@ static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
data->size);

ret = br_nf_ip_fragment(sk, skb, br_nf_push_frag_xmit);
} else {
nf_bridge_info_free(skb);
ret = br_dev_queue_push_xmit(sk, skb);
return br_nf_ip_fragment(sk, skb, br_nf_push_frag_xmit);
}
#endif
#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
if (skb->protocol == htons(ETH_P_IPV6)) {
const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
struct brnf_frag_data *data;

return ret;
}
#else
static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
{
if (br_validate_ipv6(skb))
return NF_DROP;

IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;

nf_bridge_update_protocol(skb);

data = this_cpu_ptr(&brnf_frag_data_storage);
data->encap_size = nf_bridge_encap_header_len(skb);
data->size = ETH_HLEN + data->encap_size;

skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
data->size);

if (v6ops)
return v6ops->fragment(sk, skb, br_nf_push_frag_xmit);
else
return -EMSGSIZE;
}
#endif
nf_bridge_info_free(skb);
return br_dev_queue_push_xmit(sk, skb);
}
#endif

/* PF_BRIDGE/POST_ROUTING ********************************************/
static unsigned int br_nf_post_routing(const struct nf_hook_ops *ops,
Expand Down
6 changes: 5 additions & 1 deletion net/bridge/br_private.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#include <linux/netpoll.h>
#include <linux/u64_stats_sync.h>
#include <net/route.h>
#include <net/ip6_fib.h>
#include <linux/if_vlan.h>

#define BR_HASH_BITS 8
Expand Down Expand Up @@ -214,7 +215,10 @@ struct net_bridge
spinlock_t hash_lock;
struct hlist_head hash[BR_HASH_SIZE];
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
struct rtable fake_rtable;
union {
struct rtable fake_rtable;
struct rt6_info fake_rt6_info;
};
bool nf_call_iptables;
bool nf_call_ip6tables;
bool nf_call_arptables;
Expand Down
3 changes: 2 additions & 1 deletion net/ipv6/netfilter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -191,7 +191,8 @@ static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,

static const struct nf_ipv6_ops ipv6ops = {
.chk_addr = ipv6_chk_addr,
.route_input = ip6_route_input
.route_input = ip6_route_input,
.fragment = ip6_fragment
};

static const struct nf_afinfo nf_ip6_afinfo = {
Expand Down

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