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44f64f23ba
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:
|
||
|---|---|---|
| .. | ||
| netfilter | ||
| br_arp_nd_proxy.c | ||
| br_device.c | ||
| br_fdb.c | ||
| br_forward.c | ||
| br_if.c | ||
| br_input.c | ||
| br_ioctl.c | ||
| br_mdb.c | ||
| br_mrp_netlink.c | ||
| br_mrp_switchdev.c | ||
| br_mrp.c | ||
| br_multicast.c | ||
| br_netfilter_hooks.c | ||
| br_netfilter_ipv6.c | ||
| br_netlink_tunnel.c | ||
| br_netlink.c | ||
| br_nf_core.c | ||
| br_private_mrp.h | ||
| br_private_stp.h | ||
| br_private_tunnel.h | ||
| br_private.h | ||
| br_stp_bpdu.c | ||
| br_stp_if.c | ||
| br_stp_timer.c | ||
| br_stp.c | ||
| br_switchdev.c | ||
| br_sysfs_br.c | ||
| br_sysfs_if.c | ||
| br_vlan_options.c | ||
| br_vlan_tunnel.c | ||
| br_vlan.c | ||
| br.c | ||
| Kconfig | ||
| Makefile | ||