Re: [PATCH v1 net] bridge: Return an error when enabling STP in netns.
From: Kuniyuki Iwashima <hidden>
Date: 2023-07-12 14:58:20
Also in:
bridge
From: Ido Schimmel <redacted> Date: Wed, 12 Jul 2023 17:48:20 +0300
On Tue, Jul 11, 2023 at 04:54:15PM -0700, Kuniyuki Iwashima wrote:quoted
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:
This is good to know and I also prefer this approach! I'll post v2. Thanks!
quoted hunk ↗ jump to hunk
# 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
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