netdev - Re: [PATCH v2 net] bridge: Add extack warning when enabling STP in netns.

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Message-ID: <ZK7RdhQ6fBkOY/F+@shredder>
Date: Wed, 12 Jul 2023 19:14:46 +0300
From: Ido Schimmel <idosch@...sch.org>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Roopa Prabhu <roopa@...dia.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
	bridge@...ts.linux-foundation.org,
	Harry Coin <hcoin@...etfountain.com>
Subject: Re: [PATCH v2 net] bridge: Add extack warning when enabling STP in
 netns.

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@...etfountain.com>
> Link: https://lore.kernel.org/netdev/0f531295-e289-022d-5add-5ceffa0df9bc@quietfountain.com/
> Suggested-by: Ido Schimmel <idosch@...sch.org>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Reviewed-by: Ido Schimmel <idosch@...dia.com>