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bridge: Do not send empty IFLA_AF_SPEC attribute 

commit 9b134b1694 upstream.

After commit b6c02ef549 ("bridge: Netlink interface fix."),
br_fill_ifinfo() started to send an empty IFLA_AF_SPEC attribute when a
bridge vlan dump is requested but an interface does not have any vlans
configured.

iproute2 ignores such an empty attribute since commit b262a9becbcb
("bridge: Fix output with empty vlan lists") but older iproute2 versions as
well as other utilities have their output changed by the cited kernel
commit, resulting in failed test cases. Regardless, emitting an empty
attribute is pointless and inefficient.

Avoid this change by canceling the attribute if no AF_SPEC data was added.

Fixes: b6c02ef549 ("bridge: Netlink interface fix.")
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://lore.kernel.org/r/20220725001236.95062-1-bpoirier@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Benjamin Poirier 2022-07-25 09:12:36 +09:00 committed by Greg Kroah-Hartman
parent 95226ea870
commit 3636f62f6e
1 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/bridge/br_netlink.c
View File

@ -589,9 +589,13 @@ static int br_fill_ifinfo(struct sk_buff *skb,
}
done:
if (af) {
if (nlmsg_get_pos(skb) - (void *)af > nla_attr_size(0))
nla_nest_end(skb, af);
else
nla_nest_cancel(skb, af);
}
if (af)
nla_nest_end(skb, af);
nlmsg_end(skb, nlh);
return 0;