On 12/18/2014 12:51 AM, Jason Wang wrote:

----- Original Message -----

quoted

Now that UFO is split into v4 and v6 parts, we can bring
back v4 support without any trouble.

Continue to handle legacy applications by selecting the
IPv6 fragment id but do not change the gso type.  Thist
makes sure that two legacy VMs may still communicate.

Based on original work from Ben Hutchings.

Fixes: 88e0e0e5aa7a ("drivers/net: Disable UFO through virtio")
CC: Ben Hutchings <redacted>
Signed-off-by: Vladislav Yasevich <redacted>
---
 drivers/net/tun.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9dd3746..8c32fca 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c

@@ -175,7 +175,7 @@ struct tun_struct {
 	struct net_device	*dev;
 	netdev_features_t	set_features;
 #define TUN_USER_FEATURES (NETIF_F_HW_CSUM|NETIF_F_TSO_ECN|NETIF_F_TSO| \
-			  NETIF_F_TSO6)
+			  NETIF_F_TSO6|NETIF_F_UFO)
 
 	int			vnet_hdr_sz;
 	int			sndbuf;

@@ -1152,20 +1152,15 @@ static ssize_t tun_get_user(struct tun_struct *tun,

struct tun_file *tfile,
 			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
-		{
-			static bool warned;
-
-			if (!warned) {
-				warned = true;
-				netdev_warn(tun->dev,
-					    "%s: using disabled UFO feature; please fix this program\n",
-					    current->comm);
-			}
 			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
-			if (skb->protocol == htons(ETH_P_IPV6))
+			if (vlan_get_protocol(skb) == htons(ETH_P_IPV6)) {

This probably means UDPv6 with vlan does not work well, looks like another
independent fixe and also for stable.

Ok.  I can split this out.

quoted

+				/* This allows legacy application to work.
+				 * Do not change the gso_type as it may
+				 * not be upderstood by legacy applications.
+				 */

Isn't this an issue that we use SKB_GSO_UDP for a UDPv6 packet? Especially
consider we want to fix UFOv6 in the future? We probably can use
SKB_GSO_UDP6 here and try to fix it in tun_put_user() if a legacy userspace
is detected.

There is a slight problem with this.  This will force fragmentation of IPv6
traffic between VMs since UFO6 wouldn't be enabled on a destination device.
So, suddenly older VMs will see a performance regression for large UDPv6 traffic.

With this code, a legacy VM will continue to receive large UDPv6 traffic.
New VMs will have an updated virtio-net which will reset the gso type on input.

quoted

 				ipv6_proxy_select_ident(skb);

Question still for vlan, is network header correctly set here? Looks like
ipv6_proxy_select_ident() depends on correct network header to work.

quoted

+	

Yes, you are right...  I wonder how that worked.  I'll re-test.

Thanks
-vlad
		}

quoted

 			break;
-		}
 		default:
 			tun->dev->stats.rx_frame_errors++;
 			kfree_skb(skb);

@@ -1273,6 +1268,8 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 				gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
 			else if (sinfo->gso_type & SKB_GSO_TCPV6)
 				gso.gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+			else if (sinfo->gso_type & SKB_GSO_UDP)
+				gso.gso_type = VIRTIO_NET_HDR_GSO_UDP;
 			else {
 				pr_err("unexpected GSO type: "
 				       "0x%x, gso_size %d, hdr_len %d\n",

@@ -1780,6 +1777,11 @@ static int set_offload(struct tun_struct *tun,

unsigned long arg)
 				features |= NETIF_F_TSO6;
 			arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
 		}
+
+		if (arg & TUN_F_UFO) {
+			features |= NETIF_F_UFO;
+			arg &= ~TUN_F_UFO;
+		}
 	}
 
 	/* This gives the user a way to test for new features in future by
--
1.9.3

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