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>
---
v2:
- Just add extack instead of returning error (Ido Schimmel)
v1: https://lore.kernel.org/netdev/20230711235415.92166-1-kuniyu@xxxxxxxxxx/
---
net/bridge/br_stp_if.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 75204d36d7f9..b65962682771 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -201,6 +201,9 @@ 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 does not work in non-root netns");
+
if (br_mrp_enabled(br)) {
NL_SET_ERR_MSG_MOD(extack,
"STP can't be enabled if MRP is already enabled");
--
2.30.2
