ping?

On Sat, 20 Aug 2022 12:25:16 +0900, Shigeru Yoshida wrote:

The system hangs up when batman-adv soft-interface is created on hard-interface with small MTU. For example, the following commands create batman-adv soft-interface on dummy interface with zero MTU:

# ip link add name dummy0 type dummy # ip link set mtu 0 dev dummy0 # ip link set up dev dummy0 # ip link add name bat0 type batadv # ip link set dev dummy0 master bat0

These commands cause the system hang up with the following messages:

[ 90.578925][ T6689] batman_adv: bat0: Adding interface: dummy0 [ 90.580884][ T6689] batman_adv: bat0: The MTU of interface dummy0 is too small (0) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1560 would solve the problem. [ 90.586264][ T6689] batman_adv: bat0: Interface activated: dummy0 [ 90.590061][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320) [ 90.595517][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320) [ 90.598499][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)

This patch fixes this issue by returning error when enabling hard-interface with small MTU size.

Signed-off-by: Shigeru Yoshida syoshida@redhat.com

net/batman-adv/hard-interface.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index b8f8da7ee3de..dce5557800e9 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -700,6 +700,9 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface, int max_header_len = batadv_max_header_len(); int ret;

• if (hard_iface->net_dev->mtu < ETH_MIN_MTU + max_header_len)

• return -EINVAL;
  

• if (hard_iface->if_status != BATADV_IF_NOT_IN_USE) goto out;

-- 2.37.2