[PATCH] bpf: in bpf_skb_adjust_room correct inner protocol for vxlan

[huangxuesen <hxseverything@gmail.com>]

From: huangxuesen <huangxuesen@kuaishou.com>

When pushing vxlan tunnel header, set inner protocol as ETH_P_TEB in skb
to avoid HW device disabling udp tunnel segmentation offload, just like
vxlan_build_skb does.

Drivers for NIC may invoke vxlan_features_check to check the
inner_protocol in skb for vxlan packets to decide whether to disable
NETIF_F_GSO_MASK. Currently it sets inner_protocol as the original
skb->protocol, that will make mlx5_core disable TSO and lead to huge
performance degradation.

Signed-off-by: huangxuesen <huangxuesen@kuaishou.com>
Signed-off-by: chengzhiyong <chengzhiyong@kuaishou.com>
Signed-off-by: wangli <wangli09@kuaishou.com>
---
 net/core/filter.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 255aeee72402..f8d3ba3fe10f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3466,7 +3466,12 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
 		skb->inner_mac_header = inner_net - inner_mac_len;
 		skb->inner_network_header = inner_net;
 		skb->inner_transport_header = inner_trans;
-		skb_set_inner_protocol(skb, skb->protocol);
+
+		if (flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP &&
+		    inner_mac_len == ETH_HLEN)
+			skb_set_inner_protocol(skb, htons(ETH_P_TEB));
+		else
+			skb_set_inner_protocol(skb, skb->protocol);
 
 		skb->encapsulation = 1;
 		skb_set_network_header(skb, mac_len);
-- 
2.28.0