Hi,
On 2026/4/27 17:45, Antonio Quartulli wrote:
Hi Qingfang,
thanks for the patch!
On 27/04/2026 06:00, Qingfang Deng wrote:
After decapsulating a packet, the skb->mac_header still points to the
outer transport header. Call skb_reset_mac_header() in
ovpn_netdev_write() to ensure the MAC header points to the beginning of
the inner IP packet.
May you elaborate on what this is exactly fixing?
Did you encounter a bug triggered by this missing line?
I am asking because I wonder what is "expected" as MAC header for a
packet not having one at all (packets delivered to the ovpn interface
are L3 only, as per the interface type itself).
For L3-only devices, the net core expects skb->mac_header ==
skb->network_header.
For example, in __netif_receive_skb_core(), skb_reset_mac_len() sets
skb->mac_len to (skb->network_header - skb->mac_header).
If skb->mac_header still has a stale value, this will incorrectly assign
a non-zero value to skb->mac_len.
Also, if generic XDP or SOCK_PACKET is used, either will do
skb_push(skb, skb->data - skb_mac_header(skb));
Thanks!
Regards,
Reported-by: Minqiang Chen <[email protected]>
Fixes: 8534731dbf2d ("ovpn: implement packet processing")
Signed-off-by: Qingfang Deng <[email protected]>
---
drivers/net/ovpn/io.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index db43a1f8a07a..d92bb87be2b2 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -85,6 +85,7 @@ static void ovpn_netdev_write(struct ovpn_peer
*peer, struct sk_buff *skb)
skb_scrub_packet(skb, true);
/* network header reset in ovpn_decrypt_post() */
+ skb_reset_mac_header(skb);
skb_reset_transport_header(skb);
skb_reset_inner_headers(skb);
+Cc: netdev
Regards,
Qingfang
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