Re: Offloading features in VLAN interfaces

["Olivier Crameri" <olivier.crameri@gmail.com>]

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Same thing but with the patch this time.

Sorry about that,
Olivier Crameri

On 9/29/06, Olivier Crameri <olivier.crameri@gmail.com> wrote:
> Hi,
>
> after running some experiments, we realised that using VLAN support in
> Linux caused some overhead. It turned out to be that the offloading
> features of our NIC (tso, sg, checksum offloading) were not beeing
> used.
>
> After digging a little bit in the code, we realised that the VLAN code
> did not set the features parameter of the net_device structure for the
> virtual interface. Attached is a patch with a suggested solution to
> this problem.
>
> Please let us know if this is an acceptable patch.
>
> Thanks,
> Olivier Crameri, HP Labs
>

[-- Attachment #2: vlan.patch --]
[-- Type: application/octet-stream, Size: 1780 bytes --]

--- net/8021q/vlan.c.orig	2006-09-29 16:20:01.000000000 -0700
+++ net/8021q/vlan.c	2006-09-29 17:16:31.000000000 -0700
@@ -10,7 +10,9 @@
  *              Fix for packet capture - Nick Eggleston <nick@dccinc.com>;
  *		Add HW acceleration hooks - David S. Miller <davem@redhat.com>;
  *		Correct all the locking - David S. Miller <davem@redhat.com>;
- *		Use hash table for VLAN groups - David S. Miller <davem@redhat.com>
+ *		Use hash table for VLAN groups - David S. Miller <davem@redhat.com>;
+ *		Advertise real device's features - Olivier Crameri, Hewlett-Packard 
+ *		<olivier.crameri@epfl.ch>
  *
  *		This program is free software; you can redistribute it and/or
  *		modify it under the terms of the GNU General Public License
@@ -512,6 +514,15 @@ static struct net_device *register_vlan_
 	}
 	new_dev->hard_header_parse = real_dev->hard_header_parse;
 
+	/* Advertise the same offloading features than the real device */
+	new_dev->features = real_dev->features & 
+				(NETIF_F_IP_CSUM |
+				 NETIF_F_NO_CSUM |
+				 NETIF_F_HW_CSUM |
+				 NETIF_F_SG |
+				 NETIF_F_FRAGLIST |
+				 NETIF_F_TSO );
+	
 	VLAN_DEV_INFO(new_dev)->vlan_id = VLAN_ID; /* 1 through VLAN_VID_MASK */
 	VLAN_DEV_INFO(new_dev)->real_dev = real_dev;
 	VLAN_DEV_INFO(new_dev)->dent = NULL;
@@ -663,6 +674,23 @@ static int vlan_device_event(struct noti
 				break;
 		}
 		break;
+	
+	case NETDEV_FEAT_CHANGE:
+		/* Propagate feature changes to VLAN devices */
+		for (i = 0; i < VLAN_GROUP_ARRAY_LEN; i++) {
+			vlandev = grp->vlan_devices[i];
+			if (!vlandev)
+				continue;
+			vlandev->features = dev->features & ( 
+					NETIF_F_IP_CSUM |
+				 	NETIF_F_NO_CSUM |
+				 	NETIF_F_HW_CSUM |
+				 	NETIF_F_SG |
+				 	NETIF_F_FRAGLIST |
+				 	NETIF_F_TSO );
+		}
+		break;
+
 	};
 
 out: