[NET] gso: Fix up GSO packets with broken checksums

Certain subsystems in the stack (e.g., netfilter) can break the partial
checksum on GSO packets.  Until they're fixed, this patch allows this to
work by recomputing the partial checksums through the GSO mechanism.

Once they've all been converted to update the partial checksum instead of
clearing it, this workaround can be removed.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 32 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 0096349ee38..4d2b5167d7f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1162,9 +1162,17 @@ int skb_checksum_help(struct sk_buff *skb, int inward)
 	unsigned int csum;
 	int ret = 0, offset = skb->h.raw - skb->data;
 
-	if (inward) {
-		skb->ip_summed = CHECKSUM_NONE;
-		goto out;
+	if (inward)
+		goto out_set_summed;
+
+	if (unlikely(skb_shinfo(skb)->gso_size)) {
+		static int warned;
+
+		WARN_ON(!warned);
+		warned = 1;
+
+		/* Let GSO fix up the checksum. */
+		goto out_set_summed;
 	}
 
 	if (skb_cloned(skb)) {
@@ -1181,6 +1189,8 @@ int skb_checksum_help(struct sk_buff *skb, int inward)
 	BUG_ON(skb->csum + 2 > offset);
 
 	*(u16*)(skb->h.raw + skb->csum) = csum_fold(csum);
+
+out_set_summed:
 	skb->ip_summed = CHECKSUM_NONE;
 out:	
 	return ret;
@@ -1201,17 +1211,35 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, int features)
 	struct sk_buff *segs = ERR_PTR(-EPROTONOSUPPORT);
 	struct packet_type *ptype;
 	int type = skb->protocol;
+	int err;
 
 	BUG_ON(skb_shinfo(skb)->frag_list);
-	BUG_ON(skb->ip_summed != CHECKSUM_HW);
 
 	skb->mac.raw = skb->data;
 	skb->mac_len = skb->nh.raw - skb->data;
 	__skb_pull(skb, skb->mac_len);
 
+	if (unlikely(skb->ip_summed != CHECKSUM_HW)) {
+		static int warned;
+
+		WARN_ON(!warned);
+		warned = 1;
+
+		if (skb_header_cloned(skb) &&
+		    (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+			return ERR_PTR(err);
+	}
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(ptype, &ptype_base[ntohs(type) & 15], list) {
 		if (ptype->type == type && !ptype->dev && ptype->gso_segment) {
+			if (unlikely(skb->ip_summed != CHECKSUM_HW)) {
+				err = ptype->gso_send_check(skb);
+				segs = ERR_PTR(err);
+				if (err || skb_gso_ok(skb, features))
+					break;
+				__skb_push(skb, skb->data - skb->nh.raw);
+			}
 			segs = ptype->gso_segment(skb, features);
 			break;
 		}