Re: SCTP multi-homed association (::1)->(::1+127.0.0.1) attempting HEARTBEAT on 127.0.0.1->127.0.0.1

[Pau Espin Pedrol <pespin@sysmocom.de>]

Hi Andreas,

My point is that the failure is in the client, which is creating an
AF_INET6 socket and only binding on ::1, so it should never try to use
"127.0.0.1" as local IP imho. Your comments may apply to the server,
which is actually behaving fine.

On 8/24/20 12:12 PM, Andreas Fink wrote:
> The problem might be that your socket(AF_INET6,SCTP,STREAM) gives you an
> IPv6 only socket
> but you are binding an IPv4 address to it with sctp_bindx. This will
> probably fail and thus you are binding to "any".

It doesn't fail, I'm checking the result of sctp_bindx() and
/proc/net/sctp/eps I initially attached to the bug tracker shows it's
binding fine as expected.

> 
> If you want IPv4+IPv6 in one socket, you need to specify a IPv4 address
> in  IPv6 compatibility format
> So you should sctp_bindx to   "::ffff:127.0.0.1" not to  "127.0.0.1"
>  (well in any case you should pass a struck sockaddr_in6 and not a
> struct sockaddr_in)

Not really. I'm creating an addr buffer containing both struct
sockaddr_in and struct sockaddr_in6 (see [1] if interested) after having
looked at how libsctp and the kernel handle the sctp_bindx call, and
it's working fine as backed by what /proc/net/sctp/eps shows.

[1]
https://git.osmocom.org/libosmocore/tree/src/socket.c?idí42a889004730beb26ce61ee462244b2bad6be9#n470

-- 
- Pau Espin Pedrol <pespin@sysmocom.de>         http://www.sysmocom.de/
===================================* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Director: Harald Welte