Re: [LARTC] the routing cache and route selection; is this correct?

[Julian Anastasov <ja@ssi.bg>]

	Hello,

On Mon, 28 Oct 2002, Martin A. Brown wrote:

>   - If there is no routing cache entry, we continue with route selection
>     by consulting the RPDB and routing tables.
>
>     1 start traversing the RPDB at the highest priority
>     2 keep traversing the RPDB for the next matching entry

	Lookup the list with ip rules and match by using the following
keys:

- dest
- src
- tos (optional)
- fwmark (optional)
- iif (optional)

>     3 when a match is found, try to find a match for the destination
>       in the designated table

	In the designated table lookup for routes by using the following
keys:

- dest
- tos
- scope
- oif (optional)

> So, my question:
>
> Is the routing cache actually keyed on the above items?  If I understand
> Arthur's post of last Friday properly

	Yes, you listed the cache keys correctly.

> (http://mailman.ds9a.nl/pipermail/lartc/2002q4/005641.html), he's
> suggesting that the keys in the routing cache are src, dest, and tos.

> My empirical evidence: I know I'm using fwmark routing on a particular
> host, and packets are transmitted out the "correct" interfaces when I
> generate traffic for all of the fwmark'd routes.  What confuses me is the
> output of "ip route show cache ip.ad.dr.es".  There is no reference
> whatsoever to fwmark in this output.

	May be for compatibility reasons the fwmark is not
listed in the route cache entries.

> Can somebody confirm (as the evidence suggests) that the routing cache is
> keyed on the above five elements?

	Yes, this is my understanding reading the sources

> -Martin

Regards

--
Julian Anastasov <ja@ssi.bg>

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