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author | Antoine Tenart <atenart@kernel.org> | 2020-11-23 18:49:02 +0100 |
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committer | Jakub Kicinski <kuba@kernel.org> | 2020-11-28 11:46:51 -0800 |
commit | 44f64f23bae2f0fad25503bc7ab86cd08d04cd47 (patch) | |
tree | 0f3478c5336f67d4c948b3f18df214b8afcdfa5e /net/bridge/br_netfilter_hooks.c | |
parent | c84e1efae022071a4fcf9f1899bf71777c49943a (diff) | |
download | linux-44f64f23bae2f0fad25503bc7ab86cd08d04cd47.tar.gz linux-44f64f23bae2f0fad25503bc7ab86cd08d04cd47.tar.bz2 linux-44f64f23bae2f0fad25503bc7ab86cd08d04cd47.zip |
netfilter: bridge: reset skb->pkt_type after NF_INET_POST_ROUTING traversal
Netfilter changes PACKET_OTHERHOST to PACKET_HOST before invoking the
hooks as, while it's an expected value for a bridge, routing expects
PACKET_HOST. The change is undone later on after hook traversal. This
can be seen with pairs of functions updating skb>pkt_type and then
reverting it to its original value:
For hook NF_INET_PRE_ROUTING:
setup_pre_routing / br_nf_pre_routing_finish
For hook NF_INET_FORWARD:
br_nf_forward_ip / br_nf_forward_finish
But the third case where netfilter does this, for hook
NF_INET_POST_ROUTING, the packet type is changed in br_nf_post_routing
but never reverted. A comment says:
/* We assume any code from br_dev_queue_push_xmit onwards doesn't care
* about the value of skb->pkt_type. */
But when having a tunnel (say vxlan) attached to a bridge we have the
following call trace:
br_nf_pre_routing
br_nf_pre_routing_ipv6
br_nf_pre_routing_finish
br_nf_forward_ip
br_nf_forward_finish
br_nf_post_routing <- pkt_type is updated to PACKET_HOST
br_nf_dev_queue_xmit <- but not reverted to its original value
vxlan_xmit
vxlan_xmit_one
skb_tunnel_check_pmtu <- a check on pkt_type is performed
In this specific case, this creates issues such as when an ICMPv6 PTB
should be sent back. When CONFIG_BRIDGE_NETFILTER is enabled, the PTB
isn't sent (as skb_tunnel_check_pmtu checks if pkt_type is PACKET_HOST
and returns early).
If the comment is right and no one cares about the value of
skb->pkt_type after br_dev_queue_push_xmit (which isn't true), resetting
it to its original value should be safe.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Reviewed-by: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/r/20201123174902.622102-1-atenart@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/bridge/br_netfilter_hooks.c')
-rw-r--r-- | net/bridge/br_netfilter_hooks.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 04c3f9a82650..8edfb98ae1d5 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -735,6 +735,11 @@ static int br_nf_dev_queue_xmit(struct net *net, struct sock *sk, struct sk_buff mtu_reserved = nf_bridge_mtu_reduction(skb); mtu = skb->dev->mtu; + if (nf_bridge->pkt_otherhost) { + skb->pkt_type = PACKET_OTHERHOST; + nf_bridge->pkt_otherhost = false; + } + if (nf_bridge->frag_max_size && nf_bridge->frag_max_size < mtu) mtu = nf_bridge->frag_max_size; @@ -835,8 +840,6 @@ static unsigned int br_nf_post_routing(void *priv, else return NF_ACCEPT; - /* We assume any code from br_dev_queue_push_xmit onwards doesn't care - * about the value of skb->pkt_type. */ if (skb->pkt_type == PACKET_OTHERHOST) { skb->pkt_type = PACKET_HOST; nf_bridge->pkt_otherhost = true; |