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>

5 files changed, 57 insertions, 16 deletions

diff --git a/include/linux/udp.h b/include/linux/udp.h
index 247cfdcc4b08..ee3277593222 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -49,7 +49,11 @@ struct udp_sock {
         unsigned int     corkflag;      /* Cork is required */
         __u8             encap_type;    /* Is this an Encapsulation socket? */
         unsigned char    no_check6_tx:1,/* Send zero UDP6 checksums on TX? */
-                         no_check6_rx:1;/* Allow zero UDP6 checksums on RX? */
+                         no_check6_rx:1,/* Allow zero UDP6 checksums on RX? */
+                         convert_csum:1;/* On receive, convert checksum
+                                         * unnecessary to checksum complete
+                                         * if possible.
+                                         */
         /*
          * Following member retains the information to create a UDP header
          * when the socket is uncorked.
@@ -98,6 +102,16 @@ static inline bool udp_get_no_check6_rx(struct sock *sk)
         return udp_sk(sk)->no_check6_rx;
 }
 
+static inline void udp_set_convert_csum(struct sock *sk, bool val)
+{
+        udp_sk(sk)->convert_csum = val;
+}
+
+static inline bool udp_get_convert_csum(struct sock *sk)
+{
+        return udp_sk(sk)->convert_csum;
+}
+
 #define udp_portaddr_for_each_entry(__sk, node, list) \
         hlist_nulls_for_each_entry(__sk, node, list, __sk_common.skc_portaddr_node)
 
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)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 12fcce8fba46..f6ba535b6feb 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -891,6 +891,10 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
                         goto csum_error;
                 }
 
+                if (udp_sk(sk)->convert_csum && uh->check && !IS_UDPLITE(sk))
+                        skb_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
+                                                 ip6_compute_pseudo);
+
                 ret = udpv6_queue_rcv_skb(sk, skb);
                 sock_put(sk);
 
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index b13e377e9c53..89cb9a9b8537 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -134,16 +134,26 @@ static struct sk_buff **udp6_gro_receive(struct sk_buff **head,
 {
         struct udphdr *uh = udp_gro_udphdr(skb);
 
+        if (unlikely(!uh))
+                goto flush;
+
         /* 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,
-                                                  ip6_gro_compute_pseudo))) {
-                NAPI_GRO_CB(skb)->flush = 1;
-                return NULL;
-        }
+        if (!NAPI_GRO_CB(skb)->flush)
+                goto skip;
 
+        if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
+                                                 ip6_gro_compute_pseudo))
+                goto flush;
+        else if (uh->check)
+                skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
+                                             ip6_gro_compute_pseudo);
+
+skip:
         return udp_gro_receive(head, skb, uh);
+
+flush:
+        NAPI_GRO_CB(skb)->flush = 1;
+        return NULL;
 }
 
 int udp6_gro_complete(struct sk_buff *skb, int nhoff)