Re: Bridges

[Jonathan Tripathy <jonnyt@abpni.co.uk>]

On 23/08/10 09:22, Pascal Hambourg wrote:
> Jonathan Tripathy a écrit :
>    
>>> "IP routing" may have different meanings. It can be a synonym for "IP
>>> forwarding", like in "IP routers do IP routing". But in the context of
>>> the Linux IP stack, it rather means the handling of an IP packet
>>> according to the routing table. In short :
>>> - for an incoming packet, determine whether it is for local delivery or
>>> to be forwarded ;
>>> - for an outgoing or forwarded packet, determine the output interface
>>> and gateway.
>>>        
>> I definitely still want link to do that though, with my bridge traffic...
>>      
> Do what ? I don't understand, sorry.
>    

Sorry, I'm not wording my questions very well. Let me start from the 
top. Thanks everyone for the fantastic help by the way :)

Ok, so as I understand Linux, and please correct me if I'm wrong, when a 
packet comes into a physical interface on a Linux machine, regardless of 
the status of the net.ipv4.conf.<interface>.forwarding, Linux will 
always put the packet onto a "chain". This will either be the INPUT 
chain or the FORWARD chain. Is that correct?

Next, if the packet it destined for an IP of one of the local 
interfaces, it puts it onto the INPUT chain, correct?

However if the packet it destined for a non-local host, it puts it onto 
the FORWARD chain, correct?

Then, when the packet is on the forward chain, it depends on if the 
incoming interface is connected to a bridge or not. If it is connected 
to a bridge, the packet will transverse the FORWARD chain and go out the 
interface which must be part of the same bridge, correct?

If, however, the incoming interface is not connected to a bridge, Linux 
will fordward the packet out of another interface which is thinks is 
correct (as defined by the routing table), but it will only do this if 
net.ipv4.conf.<interface>.forwarding is set to 1, correct?

Before I go on with my next set of question, I'd just like someone to 
correct the above if it is wrong

Many Thanks