❦ 23 février 2014 10:31 CET, Willy Tarreau <w...@1wt.eu> :
>> > It depends if you have some servers in common or not. The system will
>> > always allow multiple outgoing connections to share the same local
>> > source ip:port as long as they don't go to the same destination ip:ports
>> > since a connection is defined by (proto,srcip,sport,dstip,dport).
>>
>> Are you sure? I was thinking the same thing until I looked at the
>> sources. It seems that for an outgoing connection, only the source
>> address and source port are considered (see inet_csk_get_port() and
>> inet_csk_bind_conflict()).
>
> No, if you bind it yourself it's always OK. That's exactly why we
> introduced the port range in the source statement, to allow certain
> sites to reach 1M connections by having 64k per server. However, if
> you let the system choose a port for you, it totally depends on the
> kernel version, the algorithm has changed many times between something
> like 2.6.37 and 3.5. In earlier kernels it's exactly what you describe.
> I believe that 3.2 might be the first one capable of picking a port
> which is already used for another destination.
I suppose this is in combination with SO_REUSEADDR (otherwise, bind()
would fail). It's good to know:
tcp ESTAB 0 0 192.168.116.1:37544 74.125.132.104:80
tcp ESTAB 0 0 192.168.116.1:37544 74.125.132.106:80
As for getting the same stuff without explictely use bind(), I just
tried with a 3.2 and I am able to get in the same situation without
bind() nor SO_REUSEADDR option:
tcp ESTAB 0 0 10.234.78.65:61000 10.234.78.67:80
tcp ESTAB 0 0 10.234.78.65:61000 10.234.78.66:80
That's a relief ;-)
--
Modularise. Use subroutines.
- The Elements of Programming Style (Kernighan & Plauger)
