From ab7aa05c06ae340e5c7530bb78fa8d23794e460b Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Tue, 22 Sep 2026 16:12:39 +0300 Subject: [PATCH] vrf: Stop corrupting skb->csum when capturing CHECKSUM_COMPLETE packets The VRF device is an Ethernet device but it can have non-Ethernet ports such as IP tunnels. Before the cited commit, capturing packets from such ports on the VRF device resulted in these packets being detected as malformed since they lack an Ethernet header. The cited commit fixed it by pushing a dummy Ethernet header to such packets before the capture and pulling it afterwards. In the case of CHECKSUM_COMPLETE packets it also updated skb->csum with the checksum of the dummy Ethernet header. This is wrong as skb->csum should not include the checksum of the Ethernet header ("checksum of the _whole_ packet as seen by netif_rx()"). This also means that L4 protocols receive a corrupted skb->csum and potentially drop the packet, as is the case with UDP packets whose checksum was completed by software. Fix by removing the unnecessary call to skb_postpush_rcsum(). Fixes: 048939088220 ("vrf: add mac header for tunneled packets when sniffer is attached") Reported-by: Stefano Sasso Closes: https://lore.kernel.org/netdev/CALtE316UtL3x7LL6uxfXzx8rW6AbzYPeDOb478hqJCr_-dj=Wg@mail.gmail.com/ Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Reviewed-by: Eric Dumazet Reviewed-by: Andrea Mayer Link: https://patch.msgid.link/20260922131239.2509494-1-idosch@nvidia.com Signed-off-by: Jakub Kicinski --- drivers/net/vrf.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c index a0557a3a7026..d4dc6d690a75 100644 --- a/drivers/net/vrf.c +++ b/drivers/net/vrf.c @@ -1175,8 +1175,6 @@ static int vrf_prepare_mac_header(struct sk_buff *skb, skb->protocol = eth->h_proto; skb->pkt_type = PACKET_HOST; - skb_postpush_rcsum(skb, skb->data, ETH_HLEN); - skb_pull_inline(skb, ETH_HLEN); return 0;