[PATCH net] net: vrf: Fix ping failed when vrf mtu is set to 0

[linmiaohe <linmiaohe@huawei.com>]

From: Miaohe Lin <linmiaohe@huawei.com>

When the mtu of a vrf device is set to 0, it would cause ping
failed.So I think we should limit dev->min_mtu to ETH_MIN_MTU
to solve this problem. And if dev->max_mtu still be 0 can be
confusing, so I limit dev->max_mtu to ETH_MAX_MTU.

Here is the reproduce step:

1.Config vrf interface and set mtu to 0:
# ip link show vrf vrf1
3: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel
master vrf1 state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:9e:dd:c1 brd ff:ff:ff:ff:ff:ff
# ip link set vrf1 mtu 0

2.Ping peer:
# ip addr show enp4s0
3: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel
master vrf1 state UP group default qlen 1000
    link/ether 52:54:00:9e:dd:c1 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.1/16 scope global enp4s0
       valid_lft forever preferred_lft forever
# ip vrf exec vrf1 ping 10.0.0.2 -c 1
connect: Network is unreachable

3.Set mtu to default value, ping works:
# ip link set vrf1 mtu 65536
# ip vrf exec vrf1 ping 10.0.0.2 -c 1
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=1.88 ms

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 drivers/net/vrf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
index 7c1430ed0244..632d84fee366 100644
--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -1274,8 +1274,8 @@ static void vrf_setup(struct net_device *dev)
 	/* default to no qdisc; user can add if desired */
 	dev->priv_flags |= IFF_NO_QUEUE;

-	dev->min_mtu = 0;
-	dev->max_mtu = 0;
+	dev->min_mtu = ETH_MIN_MTU;
+	dev->max_mtu = ETH_MAX_MTU;
 }

 static int vrf_validate(struct nlattr *tb[], struct nlattr *data[],
-- 
2.19.1




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