Subject: Re: [PATCH] [IPVS] transparent proxying

From: Thomas Graf <[email-masked]>
Date: Wed, 29 Nov 2006 15:15:23 +0100

* Horms <[email-masked]> 2006-11-29 15:21
> This seems to be a pretty clean solution to a real problem.
> 
> Ultimately I would like to see IPVS move into the forward chain.
> This seems to be a nice way to explore that, without breaking
> any existing setups.
> 
> -- 
> Horms
>   H: http://www.vergenet.net/~horms/
>   W: http://www.valinux.co.jp/en/
> 
> [IPVS] transparent proxying
> 
> Patch from Jinhua Luo <[email-masked]> to allow a web cluseter using
> transparent proxying. It works by simply grabing packets that have the
> fwmark set and have not already been processed by ipvs (ip_vs_out) and
> throwing them into ip_vs_in.
> 
> See: http://archive.linuxvirtualserver.org/html/lvs-users/2006-11/msg00261.html
> 
> Normally LVS packets are processed by ip_vs_in fron on the INPUT chain,
> and packets that are processed in this way never show up on the FORWARD
> chain, so they won't hit this rule.
> 
> This patch seems like a good precursor to moving LVS permanantly to
> the FORWARD chain. As I'm struggling to think how it could break things.
> 
> The changes to the original patch are:
> 
> * Reformated to use tabs for indentation (instead of 4 spaces)
> * Reformated to be < 80 columns wide
> * Added some comments
> * Rewrote description (this text)
> 
> Signed-off-by: Simon Horman <[email-masked]>
> Signed-off-by: Jinhua Luo <[email-masked]>
> 
> Index: linux-2.6/net/ipv4/ipvs/ip_vs_core.c
> ===================================================================
> --- linux-2.6.orig/net/ipv4/ipvs/ip_vs_core.c	2006-11-28 15:30:00.000000000 +0900
> +++ linux-2.6/net/ipv4/ipvs/ip_vs_core.c	2006-11-29 10:27:49.000000000 +0900
> @@ -23,7 +23,9 @@
>   * Changes:
>   *	Paul `Rusty' Russell		properly handle non-linear skbs
>   *	Harald Welte			don't use nfcache
> - *
> + *	Jinhua Luo                      redirect packets with fwmark on
> + *					NF_IP_FORWARD chain to ip_vs_in(),
> + *					mainly for transparent cache cluster
>   */
>  
>  #include <linux/module.h>
> @@ -1070,6 +1072,26 @@
>  	return ip_vs_in_icmp(pskb, &r, hooknum);
>  }
>  
> +/*
> + * 	This is hooked into the NF_IP_FORWARD. It catches
> + * 	packets that have not already been handled by ipvs (out)
> + * 	and have a fwmark set. This is to allow transparent proxying
> + * 	of fwmark virtual services.
> + *
> + * 	It will not process packets that are handled by ipvs (in)
> + * 	as they never traverse the NF_IP_FORWARD.
> + */
> +static unsigned int
> +ip_vs_forward_with_fwmark(unsigned int hooknum, struct sk_buff **pskb,
> +			  const struct net_device *in,
> +			  const struct net_device *out,
> +			  int (*okfn)(struct sk_buff *))
> +{
> +	if ((*pskb)->ipvs_property || ! (*pskb)->nfmark)
> +		return NF_ACCEPT;

This patch seems to be based on an old tree, I've renamed nfmark
to mark in net-2.6.20. The term fwmark and nfmark shouldn't be
used anymore.