net: Fix possible wrong checksum generation.

Patch cef401de7be8c4e (net: fix possible wrong checksum
generation) fixed wrong checksum calculation but it broke TSO by
defining new GSO type but not a netdev feature for that type.
net_gso_ok() would not allow hardware checksum/segmentation
offload of such packets without the feature.

Following patch fixes TSO and wrong checksum. This patch uses
same logic that Eric Dumazet used. Patch introduces new flag
SKBTX_SHARED_FRAG if at least one frag can be modified by
the user. but SKBTX_SHARED_FRAG flag is kept in skb shared
info tx_flags rather than gso_type.

tx_flags is better compared to gso_type since we can have skb with
shared frag without gso packet. It does not link SHARED_FRAG to
GSO, So there is no need to define netdev feature for this.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 3 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 21a22cce6e53..6c1ad09f8796 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2326,8 +2326,7 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
 {
         int pos = skb_headlen(skb);
 
-        skb_shinfo(skb1)->gso_type = skb_shinfo(skb)->gso_type;
-
+        skb_shinfo(skb)->tx_flags = skb_shinfo(skb1)->tx_flags & SKBTX_SHARED_FRAG;
         if (len < pos)  /* Split line is inside header. */
                 skb_split_inside_header(skb, skb1, len, pos);
         else            /* Second chunk has no header, nothing to copy. */
@@ -2833,7 +2832,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
                 skb_copy_from_linear_data_offset(skb, offset,
                                                  skb_put(nskb, hsize), hsize);
 
-                skb_shinfo(nskb)->gso_type = skb_shinfo(skb)->gso_type;
+                skb_shinfo(nskb)->tx_flags = skb_shinfo(skb)->tx_flags & SKBTX_SHARED_FRAG;
 
                 while (pos < offset + len && i < nfrags) {
                         *frag = skb_shinfo(skb)->frags[i];