On Sat, 6 May 2023 10:15:29 +0800, Hao Chen <chenh@xxxxxxxxxx> wrote:Yes.
When VIRTIO_NET_F_MTU(3) Device maximum MTU reporting is supported.
If offered by the device, device advises driver about the value of its
maximum MTU. If negotiated, the driver uses mtu as the maximum
MTU value. But there the driver also uses it as default mtu,
some devices may have a maximum MTU greater than 1500, this may
cause some large packages to be discarded,
You mean tx packet?
In the current code, if the maximum MTU supported by the virtio net hardware is 9000, the default MTU of the virtio net driver will also be set to 9000. When sending packets through "ping -s 5000", if the peer router does not support negotiating a path MTU through ICMP packets, the packets will be discarded. If the peer router supports negotiating path mtu through ICMP packets, the host side will perform packet sharding processing based on the negotiated path mtu, which is generally within 1500.
If yes, I do not think this is the problem of driver.
Maybe you should give more details about the discard.
so I changed the MTU to a more
general 1500 when 'Device maximum MTU' bigger than 1500.
Signed-off-by: Hao Chen <chenh@xxxxxxxxxx>
---
drivers/net/virtio_net.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8d8038538fc4..e71c7d1b5f29 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -4040,7 +4040,10 @@ static int virtnet_probe(struct virtio_device *vdev)
goto free;
}
- dev->mtu = mtu;
+ if (mtu > 1500)
s/1500/ETH_DATA_LEN/
Thanks.
+ dev->mtu = 1500;
+ else
+ dev->mtu = mtu;
dev->max_mtu = mtu;
}
--
2.27.0