gro: Clean up tcpX_gro_receive checksum verification

This patch simplifies the checksum verification in tcpX_gro_receive
by reusing the CHECKSUM_COMPLETE code for CHECKSUM_NONE.  All it
does for CHECKSUM_NONE is compute the partial checksum and then
treat it as if it came from the hardware (CHECKSUM_COMPLETE).
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Cheers,
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_offload.c

@@ -274,35 +274,29 @@ static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *
 {
 	const struct iphdr *iph = skb_gro_network_header(skb);
 	__wsum wsum;
-	__sum16 sum;
 
 	/* Don't bother verifying checksum if we're going to flush anyway. */
 	if (NAPI_GRO_CB(skb)->flush)
 		goto skip_csum;
 
+	wsum = skb->csum;
+
 	switch (skb->ip_summed) {
+	case CHECKSUM_NONE:
+		wsum = skb_checksum(skb, skb_gro_offset(skb), skb_gro_len(skb),
+				    0);
+
+		/* fall through */
+
 	case CHECKSUM_COMPLETE:
 		if (!tcp_v4_check(skb_gro_len(skb), iph->saddr, iph->daddr,
-				  skb->csum)) {
+				  wsum)) {
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 			break;
 		}
-flush:
+
 		NAPI_GRO_CB(skb)->flush = 1;
 		return NULL;
-
-	case CHECKSUM_NONE:
-		wsum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
-					  skb_gro_len(skb), IPPROTO_TCP, 0);
-		sum = csum_fold(skb_checksum(skb,
-					     skb_gro_offset(skb),
-					     skb_gro_len(skb),
-					     wsum));
-		if (sum)
-			goto flush;
-
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-		break;
 	}
 
 skip_csum:

net/ipv6/tcpv6_offload.c

@@ -37,36 +37,29 @@ static struct sk_buff **tcp6_gro_receive(struct sk_buff **head,
 {
 	const struct ipv6hdr *iph = skb_gro_network_header(skb);
 	__wsum wsum;
-	__sum16 sum;
 
 	/* Don't bother verifying checksum if we're going to flush anyway. */
 	if (NAPI_GRO_CB(skb)->flush)
 		goto skip_csum;
 
+	wsum = skb->csum;
+
 	switch (skb->ip_summed) {
+	case CHECKSUM_NONE:
+		wsum = skb_checksum(skb, skb_gro_offset(skb), skb_gro_len(skb),
+				    wsum);
+
+		/* fall through */
+
 	case CHECKSUM_COMPLETE:
 		if (!tcp_v6_check(skb_gro_len(skb), &iph->saddr, &iph->daddr,
-				  skb->csum)) {
+				  wsum)) {
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 			break;
 		}
-flush:
+
 		NAPI_GRO_CB(skb)->flush = 1;
 		return NULL;
-
-	case CHECKSUM_NONE:
-		wsum = ~csum_unfold(csum_ipv6_magic(&iph->saddr, &iph->daddr,
-						    skb_gro_len(skb),
-						    IPPROTO_TCP, 0));
-		sum = csum_fold(skb_checksum(skb,
-					     skb_gro_offset(skb),
-					     skb_gro_len(skb),
-					     wsum));
-		if (sum)
-			goto flush;
-
-		skb->ip_summed = CHECKSUM_UNNECESSARY;
-		break;
 	}
 
 skip_csum: