ipv4: fix tunneled VM traffic over hw VXLAN/GRE GSO NIC

VM to VM GSO traffic is broken if it goes through VXLAN or GRE
tunnel and the physical NIC on the host supports hardware VXLAN/GRE
GSO offload (e.g. bnx2x and next-gen mlx4).

Two issues -
(VXLAN) VM traffic has SKB_GSO_DODGY and SKB_GSO_UDP_TUNNEL with
SKB_GSO_TCP/UDP set depending on the inner protocol. GSO header
integrity check fails in udp4_ufo_fragment if inner protocol is
TCP. Also gso_segs is calculated incorrectly using skb->len that
includes tunnel header. Fix: robust check should only be applied
to the inner packet.

(VXLAN & GRE) Once GSO header integrity check passes, NULL segs
is returned and the original skb is sent to hardware. However the
tunnel header is already pulled. Fix: tunnel header needs to be
restored so that hardware can perform GSO properly on the original
packet.

Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 44 insertions, 23 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 7514b9c37a39..5faaadb0c74f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3017,6 +3017,19 @@ static inline void netif_set_gso_max_size(struct net_device *dev,
         dev->gso_max_size = size;
 }
 
+static inline void skb_gso_error_unwind(struct sk_buff *skb, __be16 protocol,
+                                        int pulled_hlen, u16 mac_offset,
+                                        int mac_len)
+{
+        skb->protocol = protocol;
+        skb->encapsulation = 1;
+        skb_push(skb, pulled_hlen);
+        skb_reset_transport_header(skb);
+        skb->mac_header = mac_offset;
+        skb->network_header = skb->mac_header + mac_len;
+        skb->mac_len = mac_len;
+}
+
 static inline bool netif_is_macvlan(struct net_device *dev)
 {
         return dev->priv_flags & IFF_MACVLAN;
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index e5d436188464..2cd02f32f99f 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -28,6 +28,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         netdev_features_t enc_features;
         int ghl = GRE_HEADER_SECTION;
         struct gre_base_hdr *greh;
+        u16 mac_offset = skb->mac_header;
         int mac_len = skb->mac_len;
         __be16 protocol = skb->protocol;
         int tnl_hlen;
@@ -58,13 +59,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         } else
                 csum = false;
 
+        if (unlikely(!pskb_may_pull(skb, ghl)))
+                goto out;
+
         /* setup inner skb. */
         skb->protocol = greh->protocol;
         skb->encapsulation = 0;
 
-        if (unlikely(!pskb_may_pull(skb, ghl)))
-                goto out;
-
         __skb_pull(skb, ghl);
         skb_reset_mac_header(skb);
         skb_set_network_header(skb, skb_inner_network_offset(skb));
@@ -73,8 +74,10 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
         /* segment inner packet. */
         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
         segs = skb_mac_gso_segment(skb, enc_features);
-        if (!segs || IS_ERR(segs))
+        if (!segs || IS_ERR(segs)) {
+                skb_gso_error_unwind(skb, protocol, ghl, mac_offset, mac_len);
                 goto out;
+        }
 
         skb = segs;
         tnl_hlen = skb_tnl_header_len(skb);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index f140048334ce..a7e4729e974b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2478,6 +2478,7 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
                                        netdev_features_t features)
 {
         struct sk_buff *segs = ERR_PTR(-EINVAL);
+        u16 mac_offset = skb->mac_header;
         int mac_len = skb->mac_len;
         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
         __be16 protocol = skb->protocol;
@@ -2497,8 +2498,11 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
         /* segment inner packet. */
         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
         segs = skb_mac_gso_segment(skb, enc_features);
-        if (!segs || IS_ERR(segs))
+        if (!segs || IS_ERR(segs)) {
+                skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
+                                     mac_len);
                 goto out;
+        }
 
         outer_hlen = skb_tnl_header_len(skb);
         skb = segs;
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 83206de2bc76..79c62bdcd3c5 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -41,6 +41,14 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 {
         struct sk_buff *segs = ERR_PTR(-EINVAL);
         unsigned int mss;
+        int offset;
+        __wsum csum;
+
+        if (skb->encapsulation &&
+            skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) {
+                segs = skb_udp_tunnel_segment(skb, features);
+                goto out;
+        }
 
         mss = skb_shinfo(skb)->gso_size;
         if (unlikely(skb->len <= mss))
@@ -63,27 +71,20 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
                 goto out;
         }
 
+        /* Do software UFO. Complete and fill in the UDP checksum as
+         * HW cannot do checksum of UDP packets sent as multiple
+         * IP fragments.
+         */
+        offset = skb_checksum_start_offset(skb);
+        csum = skb_checksum(skb, offset, skb->len - offset, 0);
+        offset += skb->csum_offset;
+        *(__sum16 *)(skb->data + offset) = csum_fold(csum);
+        skb->ip_summed = CHECKSUM_NONE;
+
         /* Fragment the skb. IP headers of the fragments are updated in
          * inet_gso_segment()
          */
-        if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
-                segs = skb_udp_tunnel_segment(skb, features);
-        else {
-                int offset;
-                __wsum csum;
-
-                /* Do software UFO. Complete and fill in the UDP checksum as
-                 * HW cannot do checksum of UDP packets sent as multiple
-                 * IP fragments.
-                 */
-                offset = skb_checksum_start_offset(skb);
-                csum = skb_checksum(skb, offset, skb->len - offset, 0);
-                offset += skb->csum_offset;
-                *(__sum16 *)(skb->data + offset) = csum_fold(csum);
-                skb->ip_summed = CHECKSUM_NONE;
-
-                segs = skb_segment(skb, features);
-        }
+        segs = skb_segment(skb, features);
 out:
         return segs;
 }