udp: Add support for doing checksum unnecessary conversion

Add support for doing CHECKSUM_UNNECESSARY to CHECKSUM_COMPLETE
conversion in UDP tunneling path.

In the normal UDP path, we call skb_checksum_try_convert after locating
the UDP socket. The check is that checksum conversion is enabled for
the socket (new flag in UDP socket) and that checksum field is
non-zero.

In the UDP GRO path, we call skb_gro_checksum_try_convert after
checksum is validated and checksum field is non-zero. Since this is
already in GRO we assume that checksum conversion is always wanted.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 21 insertions, 8 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3549c21fe5f7..0da3849fd35b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1788,6 +1788,10 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
         if (sk != NULL) {
                 int ret;
 
+                if (udp_sk(sk)->convert_csum && uh->check && !IS_UDPLITE(sk))
+                        skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
+                                                 inet_compute_pseudo);
+
                 ret = udp_queue_rcv_skb(sk, skb);
                 sock_put(sk);
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index a6adff98382a..84e0e05c9c0e 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -290,16 +290,25 @@ static struct sk_buff **udp4_gro_receive(struct sk_buff **head,
 {
         struct udphdr *uh = udp_gro_udphdr(skb);
 
-        /* Don't bother verifying checksum if we're going to flush anyway. */
-        if (unlikely(!uh) ||
-            (!NAPI_GRO_CB(skb)->flush &&
-             skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
-                                                  inet_gro_compute_pseudo))) {
-                NAPI_GRO_CB(skb)->flush = 1;
-                return NULL;
-        }
+        if (unlikely(!uh))
+                goto flush;
 
+        /* Don't bother verifying checksum if we're going to flush anyway. */
+        if (!NAPI_GRO_CB(skb)->flush)
+                goto skip;
+
+        if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
+                                                 inet_gro_compute_pseudo))
+                goto flush;
+        else if (uh->check)
+                skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
+                                             inet_gro_compute_pseudo);
+skip:
         return udp_gro_receive(head, skb, uh);
+
+flush:
+        NAPI_GRO_CB(skb)->flush = 1;
+        return NULL;
 }
 
 int udp_gro_complete(struct sk_buff *skb, int nhoff)