tcp: move logic out of tcp_v[64]_gso_send_check

In tcp_v[46]_gso_send_check the TCP checksum is initialized to the
pseudo header checksum using __tcp_v[46]_send_check. We can move this
logic into new tcp[46]_gso_segment functions to be done when
ip_summed != CHECKSUM_PARTIAL (ip_summed == CHECKSUM_PARTIAL should be
the common case, possibly always true when taking GSO path). After this
change tcp_v[46]_gso_send_check is no-op.

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

2 files changed, 47 insertions, 29 deletions

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 72912533a191..7cd12b0458ff 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -29,6 +29,28 @@ static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
         }
 }
 
+struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
+                                 netdev_features_t features)
+{
+        if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
+                return ERR_PTR(-EINVAL);
+
+        if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
+                const struct iphdr *iph = ip_hdr(skb);
+                struct tcphdr *th = tcp_hdr(skb);
+
+                /* Set up checksum pseudo header, usually expect stack to
+                 * have done this already.
+                 */
+
+                th->check = 0;
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
+        }
+
+        return tcp_gso_segment(skb, features);
+}
+
 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
                                 netdev_features_t features)
 {
@@ -44,9 +66,6 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
         __sum16 newcheck;
         bool ooo_okay, copy_destructor;
 
-        if (!pskb_may_pull(skb, sizeof(*th)))
-                goto out;
-
         th = tcp_hdr(skb);
         thlen = th->doff * 4;
         if (thlen < sizeof(*th))
@@ -271,18 +290,6 @@ EXPORT_SYMBOL(tcp_gro_complete);
 
 static int tcp_v4_gso_send_check(struct sk_buff *skb)
 {
-        const struct iphdr *iph;
-        struct tcphdr *th;
-
-        if (!pskb_may_pull(skb, sizeof(*th)))
-                return -EINVAL;
-
-        iph = ip_hdr(skb);
-        th = tcp_hdr(skb);
-
-        th->check = 0;
-        skb->ip_summed = CHECKSUM_PARTIAL;
-        __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
         return 0;
 }
 
@@ -314,7 +321,7 @@ static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
 static const struct net_offload tcpv4_offload = {
         .callbacks = {
                 .gso_send_check =       tcp_v4_gso_send_check,
-                .gso_segment    =       tcp_gso_segment,
+                .gso_segment    =       tcp4_gso_segment,
                 .gro_receive    =       tcp4_gro_receive,
                 .gro_complete   =       tcp4_gro_complete,
         },
diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
index dbb3d9262bf6..96253154db3a 100644
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -17,18 +17,6 @@
 
 static int tcp_v6_gso_send_check(struct sk_buff *skb)
 {
-        const struct ipv6hdr *ipv6h;
-        struct tcphdr *th;
-
-        if (!pskb_may_pull(skb, sizeof(*th)))
-                return -EINVAL;
-
-        ipv6h = ipv6_hdr(skb);
-        th = tcp_hdr(skb);
-
-        th->check = 0;
-        skb->ip_summed = CHECKSUM_PARTIAL;
-        __tcp_v6_send_check(skb, &ipv6h->saddr, &ipv6h->daddr);
         return 0;
 }
 
@@ -58,10 +46,33 @@ static int tcp6_gro_complete(struct sk_buff *skb, int thoff)
         return tcp_gro_complete(skb);
 }
 
+struct sk_buff *tcp6_gso_segment(struct sk_buff *skb,
+                                 netdev_features_t features)
+{
+        struct tcphdr *th;
+
+        if (!pskb_may_pull(skb, sizeof(*th)))
+                return ERR_PTR(-EINVAL);
+
+        if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
+                const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+                struct tcphdr *th = tcp_hdr(skb);
+
+                /* Set up pseudo header, usually expect stack to have done
+                 * this.
+                 */
+
+                th->check = 0;
+                skb->ip_summed = CHECKSUM_PARTIAL;
+                __tcp_v6_send_check(skb, &ipv6h->saddr, &ipv6h->daddr);
+        }
+
+        return tcp_gso_segment(skb, features);
+}
 static const struct net_offload tcpv6_offload = {
         .callbacks = {
                 .gso_send_check =       tcp_v6_gso_send_check,
-                .gso_segment    =       tcp_gso_segment,
+                .gso_segment    =       tcp6_gso_segment,
                 .gro_receive    =       tcp6_gro_receive,
                 .gro_complete   =       tcp6_gro_complete,
         },