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/tun.c b/drivers/net/tun.c
index b1038c0e2240..b6f45c5d84d5 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1019,7 +1019,6 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
                 skb->data_len += len;
                 skb->len += len;
                 skb->truesize += truesize;
-                skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
                 atomic_add(truesize, &skb->sk->sk_wmem_alloc);
                 while (len) {
                         int off = base & ~PAGE_MASK;
@@ -1165,18 +1164,16 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
         }
 
         if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
-                unsigned short gso_type = 0;
-
                 pr_debug("GSO!\n");
                 switch (gso.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_TCPV6:
-                        gso_type = SKB_GSO_TCPV6;
+                        skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
                         break;
                 case VIRTIO_NET_HDR_GSO_UDP:
-                        gso_type = SKB_GSO_UDP;
+                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
                         break;
                 default:
                         tun->dev->stats.rx_frame_errors++;
@@ -1185,10 +1182,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                 }
 
                 if (gso.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 = gso.gso_size;
-                skb_shinfo(skb)->gso_type |= gso_type;
                 if (skb_shinfo(skb)->gso_size == 0) {
                         tun->dev->stats.rx_frame_errors++;
                         kfree_skb(skb);
@@ -1204,6 +1200,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
         if (zerocopy) {
                 skb_shinfo(skb)->destructor_arg = msg_control;
                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+                skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
         }
 
         skb_reset_network_header(skb);