Re: [PATCH 2.6.12-rc4] IPv4/IPv6: UDP Large Send Offload feature

["David S. Miller" <davem@davemloft.net>]

From: ravinandan.arakali@neterion.com
Date: Thu, 26 May 2005 16:20:06 -0700 (PDT)

> Attached below is a kernel patch to provide UDP LSO(Large Send Offload) 
> feature.

Interesting patch, thanks a lot.  Some quick review:

1) I think you can use skb_shinfo(skb)->tso_size, and UDP packet
   with this non-zero will never be sent unless the driver
   indicates the capability.

2) I think NETIF_F_USO is a nicer name and consistent with
   the existing NETIF_F_TSO macro name.  Please change it.

3) Make NETIF_F_USO require both NETIF_F_SG and checksumming
   capability.  Check this at device registry, and ethtool operation
   time, so that you need not verify it during packet send.

For #3, it should be a simple change to net/core/dev.c and
net/core/ethtool.c, for example see this test we have in
net/core/dev.c:register_netdevice()

	/* TSO requires that SG is present as well. */
	if ((dev->features & NETIF_F_TSO) &&
	    !(dev->features & NETIF_F_SG)) {
		printk("%s: Dropping NETIF_F_TSO since no SG feature.\n",
		       dev->name);
		dev->features &= ~NETIF_F_TSO;
	}

Just make the same exact check for NETIF_F_USO.

Similarly, you'll need to add the necessary ethtool machinery
(missing from your patch, but really needed) then do something
similar to net/core/ethtool.c:ethtool_set_tso() for ethtool setting
of NETIF_F_USO.  Probably you'll name this function ethtool_set_uso()
:-)