Re: policy routing on locally generated packets

[Patrick McHardy <kaber@trash.net>]

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lartc@manchotnetworks.net wrote:

>The statement would force a new routing decision to be made using the
>properties of the packet as it traverses the nat table, respecting any
>marking, tos, etc.
>
>Could any of you be kind enough to offer an analysis of such a new
>target, i.e. would it work, would it be terribly complex, ...
>

A new lookup is performed for outgoing packet if any key affecting
routing decision is changed. However source address is not influenced
by this lookup, for locally originating packets it is set to rt_src in
ip_queue_xmit and ip_build_and_send_pkt but it doesn't happen
automatically with a new lookup. I'm not sure if it would be possible
to set a new source address, sockets which are bound to interfaces
might not accept packets anymore. You could try this patch, it changes
the packets source after the routing key changed, please make sure
both unbound and bound sockets work correctly.

Bye
Patrick

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>Sincerely Yours,
>
>Charles Shick
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===== net/core/netfilter.c 1.23 vs edited =====
--- 1.23/net/core/netfilter.c	Thu Jul 31 01:57:26 2003
+++ edited/net/core/netfilter.c	Mon Aug 25 14:25:19 2003
@@ -645,6 +645,7 @@
 		/* Drop old route. */
 		dst_release((*pskb)->dst);
 		(*pskb)->dst = &rt->u.dst;
+		iph->saddr = rt->rt_src;
 	} else {
 		/* non-local src, find valid iif to satisfy
 		 * rp-filter when calling ip_route_input. */