Re: [PATCH v1 net] bridge: Return an error when enabling STP in netns.
From: Ido Schimmel <hidden>
Date: 2023-07-12 14:48:28
Also in:
bridge
Subsystem:
ethernet bridge, networking [general], the rest · Maintainers:
Nikolay Aleksandrov, Ido Schimmel, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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 <redacted>
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:
# 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,
quoted hunk ↗ jump to hunk
Link: https://lore.kernel.org/netdev/0f531295-e289-022d-5add-5ceffa0df9bc@quietfountain.com/ (local) Signed-off-by: Kuniyuki Iwashima <redacted> --- 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