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>

5 files changed, 6 insertions, 8 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 1aec92bf8018..e6e5d8506336 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1287,7 +1287,6 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
                        SKB_GSO_UDP |
                        SKB_GSO_DODGY |
                        SKB_GSO_TCP_ECN |
-                       SKB_GSO_SHARED_FRAG |
                        0)))
                 goto out;
 
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 3e98ed2bff55..5e12dca7b3dd 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -598,6 +598,7 @@ slow_path:
         /* for offloaded checksums cleanup checksum before fragmentation */
         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
                 goto fail;
+        iph = ip_hdr(skb);
 
         left = skb->len - hlen;         /* Space per frame */
         ptr = hlen;             /* Where to start from */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 801b07b796f0..1f0bedb8622f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -897,8 +897,7 @@ new_segment:
                         get_page(page);
                         skb_fill_page_desc(skb, i, page, offset, copy);
                 }
-
-                skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
+                skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
 
                 skb->len += copy;
                 skb->data_len += copy;
@@ -3044,7 +3043,6 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
                                SKB_GSO_DODGY |
                                SKB_GSO_TCP_ECN |
                                SKB_GSO_TCPV6 |
-                               SKB_GSO_SHARED_FRAG |
                                0) ||
                              !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
                         goto out;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d9bfaea34322..a759e19496d2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1239,13 +1239,13 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
          */
         if (!skb_shinfo(prev)->gso_size) {
                 skb_shinfo(prev)->gso_size = mss;
-                skb_shinfo(prev)->gso_type |= sk->sk_gso_type;
+                skb_shinfo(prev)->gso_type = sk->sk_gso_type;
         }
 
         /* CHECKME: To clear or not to clear? Mimics normal skb currently */
         if (skb_shinfo(skb)->gso_segs <= 1) {
                 skb_shinfo(skb)->gso_size = 0;
-                skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG;
+                skb_shinfo(skb)->gso_type = 0;
         }
 
         /* Difference in this won't matter, both ACKed by the same cumul. ACK */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 564bf89d9fd3..6182d90e97b0 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1133,7 +1133,6 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
                                  unsigned int mss_now)
 {
-        skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG;
         if (skb->len <= mss_now || !sk_can_gso(sk) ||
             skb->ip_summed == CHECKSUM_NONE) {
                 /* Avoid the costly divide in the normal
@@ -1141,10 +1140,11 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
                  */
                 skb_shinfo(skb)->gso_segs = 1;
                 skb_shinfo(skb)->gso_size = 0;
+                skb_shinfo(skb)->gso_type = 0;
         } else {
                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
                 skb_shinfo(skb)->gso_size = mss_now;
-                skb_shinfo(skb)->gso_type |= sk->sk_gso_type;
+                skb_shinfo(skb)->gso_type = sk->sk_gso_type;
         }
 }