1. 31 Mar, 2021 2 commits
    • Paolo Abeni's avatar
      udp: skip L4 aggregation for UDP tunnel packets · 18f25dc3
      Paolo Abeni authored
      If NETIF_F_GRO_FRAGLIST or NETIF_F_GRO_UDP_FWD are enabled, and there
      are UDP tunnels available in the system, udp_gro_receive() could end-up
      doing L4 aggregation (either SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST) at
      the outer UDP tunnel level for packets effectively carrying and UDP
      tunnel header.
      
      That could cause inner protocol corruption. If e.g. the relevant
      packets carry a vxlan header, different vxlan ids will be ignored/
      aggregated to the same GSO packet. Inner headers will be ignored, too,
      so that e.g. TCP over vxlan push packets will be held in the GRO
      engine till the next flush, etc.
      
      Just skip the SKB_GSO_UDP_L4 and SKB_GSO_FRAGLIST code path if the
      current packet could land in a UDP tunnel, and let udp_gro_receive()
      do GRO via udp_sk(sk)->gro_receive.
      
      The check implemented in this patch is broader than what is strictly
      needed, as the existing UDP tunnel could be e.g. configured on top of
      a different device: we could end-up skipping GRO at-all for some packets.
      
      Anyhow, that is a very thin corner case and covering it will add quite
      a bit of complexity.
      
      v1 -> v2:
       - hopefully clarify the commit message
      
      Fixes: 9fd1ff5d ("udp: Support UDP fraglist GRO/GSO.")
      Fixes: 36707061 ("udp: allow forwarding of plain (non-fraglisted) UDP GRO packets")
      Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
      Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      18f25dc3
    • Paolo Abeni's avatar
      udp: fixup csum for GSO receive slow path · 000ac44d
      Paolo Abeni authored
      When UDP packets generated locally by a socket with UDP_SEGMENT
      traverse the following path:
      
      UDP tunnel(xmit) -> veth (segmentation) -> veth (gro) ->
      	UDP tunnel (rx) -> UDP socket (no UDP_GRO)
      
      ip_summed will be set to CHECKSUM_PARTIAL at creation time and
      such checksum mode will be preserved in the above path up to the
      UDP tunnel receive code where we have:
      
       __iptunnel_pull_header() -> skb_pull_rcsum() ->
      skb_postpull_rcsum() -> __skb_postpull_rcsum()
      
      The latter will convert the skb to CHECKSUM_NONE.
      
      The UDP GSO packet will be later segmented as part of the rx socket
      receive operation, and will present a CHECKSUM_NONE after segmentation.
      
      Additionally the segmented packets UDP CB still refers to the original
      GSO packet len. Overall that causes unexpected/wrong csum validation
      errors later in the UDP receive path.
      
      We could possibly address the issue with some additional checks and
      csum mangling in the UDP tunnel code. Since the issue affects only
      this UDP receive slow path, let's set a suitable csum status there.
      
      Note that SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST packets lacking an UDP
      encapsulation present a valid checksum when landing to udp_queue_rcv_skb(),
      as the UDP checksum has been validated by the GRO engine.
      
      v2 -> v3:
       - even more verbose commit message and comments
      
      v1 -> v2:
       - restrict the csum update to the packets strictly needing them
       - hopefully clarify the commit message and code comments
      Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
      Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      000ac44d
  2. 30 Mar, 2021 38 commits