target/linux/generic/backport-6.1/600-v6.9-03-net-gro-add-flush-check-in-udp_gro_receive_segment.patch

   1 From: Richard Gobert <richardbgobert@gmail.com>
   2 Date: Tue, 30 Apr 2024 16:35:55 +0200
   3 Subject: [PATCH] net: gro: add flush check in udp_gro_receive_segment
   4
   5 GRO-GSO path is supposed to be transparent and as such L3 flush checks are
   6 relevant to all UDP flows merging in GRO. This patch uses the same logic
   7 and code from tcp_gro_receive, terminating merge if flush is non zero.
   8
   9 Fixes: e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.")
  10 Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
  11 Reviewed-by: Willem de Bruijn <willemb@google.com>
  12 Signed-off-by: Paolo Abeni <pabeni@redhat.com>
  13 ---
  14
  15 --- a/net/ipv4/udp_offload.c
  16 +++ b/net/ipv4/udp_offload.c
  17 @@ -463,6 +463,7 @@ static struct sk_buff *udp_gro_receive_s
  18         struct sk_buff *p;
  19         unsigned int ulen;
  20         int ret = 0;
  21 +       int flush;
  22
  23         /* requires non zero csum, for symmetry with GSO */
  24         if (!uh->check) {
  25 @@ -496,13 +497,22 @@ static struct sk_buff *udp_gro_receive_s
  26                         return p;
  27                 }
  28
  29 +               flush = NAPI_GRO_CB(p)->flush;
  30 +
  31 +               if (NAPI_GRO_CB(p)->flush_id != 1 ||
  32 +                   NAPI_GRO_CB(p)->count != 1 ||
  33 +                   !NAPI_GRO_CB(p)->is_atomic)
  34 +                       flush |= NAPI_GRO_CB(p)->flush_id;
  35 +               else
  36 +                       NAPI_GRO_CB(p)->is_atomic = false;
  37 +
  38                 /* Terminate the flow on len mismatch or if it grow "too much".
  39                  * Under small packet flood GRO count could elsewhere grow a lot
  40                  * leading to excessive truesize values.
  41                  * On len mismatch merge the first packet shorter than gso_size,
  42                  * otherwise complete the GRO packet.
  43                  */
  44 -               if (ulen > ntohs(uh2->len)) {
  45 +               if (ulen > ntohs(uh2->len) || flush) {
  46                         pp = p;
  47                 } else {
  48                         if (NAPI_GRO_CB(skb)->is_flist) {