srv6: Fix packet drop with GSO type mismatch #30732
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When the Pod generates a TCP stream larger than MSS, it may be sent as a GSO large packet. We observed in such a case, SRv6-encapsulated packet is dropped. The root cause was a misuse of ctx_adjust_hroom. We call it ctx_adjust_hroom(ctx, growth, BPF_ADJ_ROOM_MAC, 0), but this way, the helper is not aware of what kind of encapsulation we want to perform, so it doesn't adjust skb->inner_protocol (should be ETH_P_IP) and skb_shinfo->gso_type (should be SKB_GSO_IPXIP6 | SKB_GSO_TCPV4) appropriately. As a result, the packet will be dropped in ip4ip6_gso_segment due to the flag mismatch. Use BPF_F_ADJ_ROOM_ENCAP_L3_IPV6 flag which is introduced to solve this problem. Signed-off-by: Yutaro Hayakawa <yutaro.hayakawa@isovalent.com>
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When the Pod generates a TCP stream larger than MSS, it may be sent as a GSO large packet. We observed in such a case, SRv6-encapsulated packet is dropped.
The root cause was a misuse of
ctx_adjust_hroom. We call itctx_adjust_hroom(ctx, growth, BPF_ADJ_ROOM_MAC, 0), but this way, the helper is not aware of what kind of encapsulation we want to perform, so it doesn't adjustskb->inner_protocol(should beETH_P_IP) andskb_shinfo->gso_type(should beSKB_GSO_IPXIP6 | SKB_GSO_TCPV4) appropriately. As a result, the packet will be dropped inip4ip6_gso_segmentdue to the flag mismatch.Use
BPF_F_ADJ_ROOM_ENCAP_L3_IPV6flag which is introduced to solve this problem.