ECMP hash keys?

[Nikolay Denev]

Hi,

Currently it's implemented using Modulo-N Hash (RFC2991), see
radix_mpath.c:rtalloc_mpath_fib()

And as hash the xor of source and destination IP is supplied, look for
rtalloc_mpath_fib() in ip_output.c :

   ...
   #ifdef RADIX_MPATH
                        rtalloc_mpath_fib(ro,
                            ntohl(ip->ip_src.s_addr ^ ip->ip_dst.s_addr),
                            inp ? inp->inp_inc.inc_fibnum : M_GETFIB(m));
   #else
   ...

I've tried to hack this to use m_pkthdr.flowid if it exists, but in my
case my network cards were not setting this (vr(4) on soekris) so I
did not saw any change. Maybe my idea was completely wrong, but the
XOR of src and dst IP is 4 bytes, and this is the size of the flowid
as well. (haven't tried with FLOWTABLE enabled though).

--Nikolay

On Tue, Jan 14, 2014 at 10:38 AM, Attila Nagy <bra at fsn.hu> wrote:
> Hi,
>
> Does equal cost multipath take only the destination address into
> consideration when choosing the route? (I've spent only about two minutes
> reading radix_mpath.h, but I've got this impression)
>
> What would be needed to use src and dst addresses and ports -if appropriate?
>
> Thanks,
>
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