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, 5 insertions, 8 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 381a2d8d8a81..192c91c8e799 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -227,7 +227,7 @@ static void set_skb_frag(struct sk_buff *skb, struct page *page,
         skb->len += size;
         skb->truesize += PAGE_SIZE;
         skb_shinfo(skb)->nr_frags++;
-        skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
+        skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
         *len -= size;
 }
 
@@ -387,18 +387,16 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
                  ntohs(skb->protocol), skb->len, skb->pkt_type);
 
         if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
-                unsigned short gso_type = 0;
-
                 pr_debug("GSO!\n");
                 switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
                 case VIRTIO_NET_HDR_GSO_TCPV4:
-                        gso_type = SKB_GSO_TCPV4;
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
                         break;
                 case VIRTIO_NET_HDR_GSO_UDP:
-                        gso_type = SKB_GSO_UDP;
+                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
                         break;
                 case VIRTIO_NET_HDR_GSO_TCPV6:
-                        gso_type = SKB_GSO_TCPV6;
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
                         break;
                 default:
                         net_warn_ratelimited("%s: bad gso type %u.\n",
@@ -407,7 +405,7 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
                 }
 
                 if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
-                        gso_type |= SKB_GSO_TCP_ECN;
+                        skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
 
                 skb_shinfo(skb)->gso_size = hdr->hdr.gso_size;
                 if (skb_shinfo(skb)->gso_size == 0) {
@@ -415,7 +413,6 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
                         goto frame_err;
                 }
 
-                skb_shinfo(skb)->gso_type |= gso_type;
                 /* Header must be checked, and gso_segs computed. */
                 skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
                 skb_shinfo(skb)->gso_segs = 0;