[PATCH net-next 07/10] veth: raise the max MTU above 65535

[Mariusz Klimek <maklimek97@gmail.com>]

This patch raises the maximum allowed MTU above 65535 to allow IPv6
jumbograms to pass through veth pairs. Raising the MTU above 65535 can
significantly improve throughput between connected namespaces. This is
particularly useful for docker containers, which are connected to the host
through veth pairs. This also serves as a way to test jumbogram handling in
the kernel.

Signed-off-by: Mariusz Klimek <maklimek97@gmail.com>
---
 drivers/net/veth.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 0cfb19b760dd..e34ffbc1d651 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1425,9 +1425,11 @@ static int veth_close(struct net_device *dev)
 	return 0;
 }
 
+#define MAX_MTU IP6_MAX_JUMBOGRAM_MTU
+
 static int is_valid_veth_mtu(int mtu)
 {
-	return mtu >= ETH_MIN_MTU && mtu <= ETH_MAX_MTU;
+	return mtu >= ETH_MIN_MTU && mtu <= MAX_MTU;
 }
 
 static int veth_alloc_queues(struct net_device *dev)
@@ -1628,7 +1630,7 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 
 			if (peer) {
 				peer->hw_features |= NETIF_F_GSO_SOFTWARE;
-				peer->max_mtu = ETH_MAX_MTU;
+				peer->max_mtu = MAX_MTU;
 			}
 		}
 		bpf_prog_put(old_prog);
@@ -1754,7 +1756,7 @@ static void veth_setup(struct net_device *dev)
 	dev->needs_free_netdev = true;
 	dev->priv_destructor = veth_dev_free;
 	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
-	dev->max_mtu = ETH_MAX_MTU;
+	dev->max_mtu = MAX_MTU;
 
 	dev->hw_features = VETH_FEATURES;
 	dev->hw_enc_features = VETH_FEATURES;
-- 
2.47.3