ECMP hash keys?

[Adrian Chadd]

On 15 January 2014 01:18, Alexander V. Chernikov <melifaro at freebsd.org> wrote:
> On 14.01.2014 23:15, Nikolay Denev wrote:
>>
>> Hi,
>>
>> Currently it's implemented using Modulo-N Hash (RFC2991), see
>> radix_mpath.c:rtalloc_mpath_fib()
>
> Yup. I'm going to change this to use flowid.
>
>>
>> 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
>
> You can try http://static.ipfw.ru/patches/netisr_ip_flowid.diff to get
> flowid values generated by netisr.

Hm, this is interesting. I wonder if we should (finally) add in the
toeplitz hash here and then make sure we are hashing the frame based
on the right header contents and direction (so transmit and receive
path frames hash to the same value.)

What do you think?


-a