From: Ido Schimmel <ido...@idosch.org>
Date: Wed, 12 Jul 2023 17:48:20 +0300
> On Tue, Jul 11, 2023 at 04:54:15PM -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 show an error when enabling STP in netns.
> >
> > # unshare -n
> > # ip link add br0 type bridge
> > # ip link set br0 type bridge stp_state 1
> > Error: bridge: STP can't be enabled 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 <hc...@quietfountain.com>
>
> I'm not sure that's accurate. I read his response in the link below and
> he says "I'd rather be warned than blocked" and "But better warned and
> awaiting a fix than blocked", which I agree with. The patch has the
> potential to cause a lot of regressions, but without actually fixing the
> problem.
>
> How about simply removing the error [1]? Since iproute2 commit
> 844c37b42373 ("libnetlink: Handle extack messages for non-error case"),
> it can print extack warnings and not only errors. With the diff below:
This is good to know and I also prefer this approach!
I'll post v2.
Thanks!
>
> # unshare -n
> # ip link add name br0 type bridge
> # ip link set dev br0 type bridge stp_state 1
> Warning: bridge: STP can't be enabled in non-root netns.
> # echo $?
> 0
>
> [1]
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index a807996ac56b..b5143de37938 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -201,10 +201,8 @@ int br_stp_set_enabled(struct net_bridge *br, unsigned
> long val,
> {
> ASSERT_RTNL();
>
> - if (!net_eq(dev_net(br->dev), &init_net)) {
> + if (!net_eq(dev_net(br->dev), &init_net))
> NL_SET_ERR_MSG_MOD(extack, "STP can't be enabled in non-root
> netns");
> - return -EINVAL;
> - }
>
> if (br_mrp_enabled(br)) {
> NL_SET_ERR_MSG_MOD(extack,
>
> > Link:
> > https://lore.kernel.org/netdev/0f531295-e289-022d-5add-5ceffa0df...@quietfountain.com/
> > Signed-off-by: Kuniyuki Iwashima <kun...@amazon.com>
> > ---
> > net/bridge/br_stp_if.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> > index 75204d36d7f9..a807996ac56b 100644
> > --- a/net/bridge/br_stp_if.c
> > +++ b/net/bridge/br_stp_if.c
> > @@ -201,6 +201,11 @@ int br_stp_set_enabled(struct net_bridge *br, unsigned
> > long val,
> > {
> > ASSERT_RTNL();
> >
> > + if (!net_eq(dev_net(br->dev), &init_net)) {
> > + NL_SET_ERR_MSG_MOD(extack, "STP can't be enabled in non-root
> > netns");
> > + return -EINVAL;
> > + }
> > +
> > if (br_mrp_enabled(br)) {
> > NL_SET_ERR_MSG_MOD(extack,
> > "STP can't be enabled if MRP is already
> > enabled");
> > --
> > 2.30.2
