Merge branch 'remcsum_adjust'

Tom Herbert says:

====================
gue: Generalize remote checksum offload

The remote checksum offload is generalized by creating a common
function (remcsum_adjust) that does the work of modifying the
checksum in remote checksum offload. This function can be called
from normal or GRO path. GUE was modified to use this function.

Remote checksum offload is described in
https://tools.ietf.org/html/draft-herbert-remotecsumoffload-01

Tested by running 200 TCP_STREAM connections over GUE, did not see
any problems with remote checksum offload enabled.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/checksum.h

@@ -151,4 +151,20 @@ static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
 				 (__force __be32)to, pseudohdr);
 }
 
+static inline __wsum remcsum_adjust(void *ptr, __wsum csum,
+				    int start, int offset)
+{
+	__sum16 *psum = (__sum16 *)(ptr + offset);
+	__wsum delta;
+
+	/* Subtract out checksum up to start */
+	csum = csum_sub(csum, csum_partial(ptr, start, 0));
+
+	/* Set derived checksum in packet */
+	delta = csum_sub(csum_fold(csum), *psum);
+	*psum = csum_fold(csum);
+
+	return delta;
+}
+
 #endif

net/ipv4/fou.c

@@ -64,15 +64,13 @@ static int fou_udp_recv(struct sock *sk, struct sk_buff *skb)
 }
 
 static struct guehdr *gue_remcsum(struct sk_buff *skb, struct guehdr *guehdr,
-				  void *data, int hdrlen, u8 ipproto)
+				  void *data, size_t hdrlen, u8 ipproto)
 {
 	__be16 *pd = data;
-	u16 start = ntohs(pd[0]);
-	u16 offset = ntohs(pd[1]);
-	u16 poffset = 0;
-	u16 plen;
-	__wsum csum, delta;
-	__sum16 *psum;
+	size_t start = ntohs(pd[0]);
+	size_t offset = ntohs(pd[1]);
+	size_t plen = hdrlen + max_t(size_t, offset + sizeof(u16), start);
+	__wsum delta;
 
 	if (skb->remcsum_offload) {
 		/* Already processed in GRO path */
@@ -80,35 +78,15 @@ static struct guehdr *gue_remcsum(struct sk_buff *skb, struct guehdr *guehdr,
 		return guehdr;
 	}
 
-	if (start > skb->len - hdrlen ||
-	    offset > skb->len - hdrlen - sizeof(u16))
-		return NULL;
-
-	if (unlikely(skb->ip_summed != CHECKSUM_COMPLETE))
-		__skb_checksum_complete(skb);
-
-	plen = hdrlen + offset + sizeof(u16);
 	if (!pskb_may_pull(skb, plen))
 		return NULL;
 	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
 
-	if (ipproto == IPPROTO_IP && sizeof(struct iphdr) < plen) {
-		struct iphdr *ip = (struct iphdr *)(skb->data + hdrlen);
-
-		/* If next header happens to be IP we can skip that for the
-		 * checksum calculation since the IP header checksum is zero
-		 * if correct.
-		 */
-		poffset = ip->ihl * 4;
-	}
-
-	csum = csum_sub(skb->csum, skb_checksum(skb, poffset + hdrlen,
-						start - poffset - hdrlen, 0));
+	if (unlikely(skb->ip_summed != CHECKSUM_COMPLETE))
+		__skb_checksum_complete(skb);
 
-	/* Set derived checksum in packet */
-	psum = (__sum16 *)(skb->data + hdrlen + offset);
-	delta = csum_sub(csum_fold(csum), *psum);
-	*psum = csum_fold(csum);
+	delta = remcsum_adjust((void *)guehdr + hdrlen,
+			       skb->csum, start, offset);
 
 	/* Adjust skb->csum since we changed the packet */
 	skb->csum = csum_add(skb->csum, delta);
@@ -158,9 +136,6 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
 
 	ip_hdr(skb)->tot_len = htons(ntohs(ip_hdr(skb)->tot_len) - len);
 
-	/* Pull UDP header now, skb->data points to guehdr */
-	__skb_pull(skb, sizeof(struct udphdr));
-
 	/* Pull csum through the guehdr now . This can be used if
 	 * there is a remote checksum offload.
 	 */
@@ -188,7 +163,7 @@ static int gue_udp_recv(struct sock *sk, struct sk_buff *skb)
 	if (unlikely(guehdr->control))
 		return gue_control_message(skb, guehdr);
 
-	__skb_pull(skb, hdrlen);
+	__skb_pull(skb, sizeof(struct udphdr) + hdrlen);
 	skb_reset_transport_header(skb);
 
 	return -guehdr->proto_ctype;
@@ -248,24 +223,17 @@ static struct guehdr *gue_gro_remcsum(struct sk_buff *skb, unsigned int off,
 				      size_t hdrlen, u8 ipproto)
 {
 	__be16 *pd = data;
-	u16 start = ntohs(pd[0]);
-	u16 offset = ntohs(pd[1]);
-	u16 poffset = 0;
-	u16 plen;
-	void *ptr;
-	__wsum csum, delta;
-	__sum16 *psum;
+	size_t start = ntohs(pd[0]);
+	size_t offset = ntohs(pd[1]);
+	size_t plen = hdrlen + max_t(size_t, offset + sizeof(u16), start);
+	__wsum delta;
 
 	if (skb->remcsum_offload)
 		return guehdr;
 
-	if (start > skb_gro_len(skb) - hdrlen ||
-	    offset > skb_gro_len(skb) - hdrlen - sizeof(u16) ||
-	    !NAPI_GRO_CB(skb)->csum_valid || skb->remcsum_offload)
+	if (!NAPI_GRO_CB(skb)->csum_valid)
 		return NULL;
 
-	plen = hdrlen + offset + sizeof(u16);
-
 	/* Pull checksum that will be written */
 	if (skb_gro_header_hard(skb, off + plen)) {
 		guehdr = skb_gro_header_slow(skb, off + plen, off);
@@ -273,26 +241,8 @@ static struct guehdr *gue_gro_remcsum(struct sk_buff *skb, unsigned int off,
 			return NULL;
 	}
 
-	ptr = (void *)guehdr + hdrlen;
-
-	if (ipproto == IPPROTO_IP &&
-	    (hdrlen + sizeof(struct iphdr) < plen)) {
-		struct iphdr *ip = (struct iphdr *)(ptr + hdrlen);
-
-		/* If next header happens to be IP we can skip
-		 * that for the checksum calculation since the
-		 * IP header checksum is zero if correct.
-		 */
-		poffset = ip->ihl * 4;
-	}
-
-	csum = csum_sub(NAPI_GRO_CB(skb)->csum,
-			csum_partial(ptr + poffset, start - poffset, 0));
-
-	/* Set derived checksum in packet */
-	psum = (__sum16 *)(ptr + offset);
-	delta = csum_sub(csum_fold(csum), *psum);
-	*psum = csum_fold(csum);
+	delta = remcsum_adjust((void *)guehdr + hdrlen,
+			       NAPI_GRO_CB(skb)->csum, start, offset);
 
 	/* Adjust skb->csum since we changed the packet */
 	skb->csum = csum_add(skb->csum, delta);