On Wed, Jul 12, 2023 at 08:44:49AM -0700, Kuniyuki Iwashima wrote:
> When we create an L2 loop on a bridge in netns, we will see packets storm
> even if STP is enabled.
>
> # unshare -n
> # ip link add br0 type bridge
> # ip link add veth0 type veth peer name veth1
> # ip link set veth0 master br0 up
> # ip link set veth1 master br0 up
> # ip link set br0 type bridge stp_state 1
> # ip link set br0 up
> # sleep 30
> # ip -s link show br0
> 2: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
> link/ether b6:61:98:1c:1c:b5 brd ff:ff:ff:ff:ff:ff
> RX: bytes packets errors dropped missed mcast
> 956553768 12861249 0 0 0 12861249 <-. Keep
> TX: bytes packets errors dropped carrier collsns | increasing
> 1027834 11951 0 0 0 0 <-' rapidly
>
> This is because llc_rcv() drops all packets in non-root netns and BPDU
> is dropped.
>
> Let's add extack warning when enabling STP in netns.
>
> # unshare -n
> # ip link add br0 type bridge
> # ip link set br0 type bridge stp_state 1
> Warning: bridge: STP does not work in non-root netns.
>
> Note this commit will be reverted later when we namespacify the whole LLC
> infra.
>
> Fixes: e730c15519d0 ("[NET]: Make packet reception network namespace safe")
> Suggested-by: Harry Coin <hcoin@xxxxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/netdev/0f531295-e289-022d-5add-5ceffa0df9bc@xxxxxxxxxxxxxxxxx/
> Suggested-by: Ido Schimmel <idosch@xxxxxxxxxx>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Reviewed-by: Ido Schimmel <idosch@xxxxxxxxxx>
