[NET]: Fix CHECKSUM_HW GSO problems.

Fix checksum problems in the GSO code path for CHECKSUM_HW packets.

The ipv4 TCP pseudo header checksum has to be adjusted for GSO
segmented packets.

The adjustment is needed because the length field in the pseudo-header
changes.  However, because we have the inequality oldlen > newlen, we
know that delta = (u16)~oldlen + newlen is still a 16-bit quantity.
This also means that htonl(delta) + th->check still fits in 32 bits.
Therefore we don't have to use csum_add on this operations.

This is based on a patch by Michael Chan <mchan@broadcom.com>.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 11 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 0e029c4e2903..c04176be7ed1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2166,7 +2166,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg)
         if (!pskb_may_pull(skb, thlen))
                 goto out;
 
-        oldlen = ~htonl(skb->len);
+        oldlen = (u16)~skb->len;
         __skb_pull(skb, thlen);
 
         segs = skb_segment(skb, sg);
@@ -2174,7 +2174,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg)
                 goto out;
 
         len = skb_shinfo(skb)->gso_size;
-        delta = csum_add(oldlen, htonl(thlen + len));
+        delta = htonl(oldlen + (thlen + len));
 
         skb = segs;
         th = skb->h.th;
@@ -2183,10 +2183,10 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg)
         do {
                 th->fin = th->psh = 0;
 
-                if (skb->ip_summed == CHECKSUM_NONE) {
-                        th->check = csum_fold(csum_partial(
-                                skb->h.raw, thlen, csum_add(skb->csum, delta)));
-                }
+                th->check = ~csum_fold(th->check + delta);
+                if (skb->ip_summed != CHECKSUM_HW)
+                        th->check = csum_fold(csum_partial(skb->h.raw, thlen,
+                                                           skb->csum));
 
                 seq += len;
                 skb = skb->next;
@@ -2196,11 +2196,11 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int sg)
                 th->cwr = 0;
         } while (skb->next);
 
-        if (skb->ip_summed == CHECKSUM_NONE) {
-                delta = csum_add(oldlen, htonl(skb->tail - skb->h.raw));
-                th->check = csum_fold(csum_partial(
-                        skb->h.raw, thlen, csum_add(skb->csum, delta)));
-        }
+        delta = htonl(oldlen + (skb->tail - skb->h.raw) + skb->data_len);
+        th->check = ~csum_fold(th->check + delta);
+        if (skb->ip_summed != CHECKSUM_HW)
+                th->check = csum_fold(csum_partial(skb->h.raw, thlen,
+                                                   skb->csum));
 
 out:
         return segs;