Re: SCTP client discarding INIT_ACK sent with different remote IP address from multihomed SCTP server

Pau Espin Pedrol <[email protected]>
Newsgroups org.kernel.vger.linux-sctp
Message-ID <[email protected]>
Hi,

On 12/2/25 16:27, Andreas Fink wrote:
> that sounds correct but how about the client? how is that one calling ? 
> is it having -h 127.0.0.1 -b 127.0.0.1 ?
> 

I'm not sure I'm following you Andreas, since I think I already 
mentioned the working vs non-working scenario in the initial email, and 
shared a pcap file for the non-working one afterwards, so I'm not sure 
what information is missing or was not clear from my side.
By the way, I think you probably don't mean "-b", which is a --bindx-rem 
"remove" param.

working case:
"sctp_darn -H 127.0.0.1 -P 8000 -c 127.0.0.1 -p 2905 -s"

non-working case:
"sctp_darn -H 127.0.0.1 -P 8000 -c 127.0.0.2 -p 2905 -s"


I don't really think it's possible to make an even simpler scenario.
Server listens on addresses A and B, and client connects (tx INIT) to B, 
while server decides to answer (INIT_ACK) using address A.
AFAICT, if my sctp linux stack client receives an INIT_ACK with a src 
addr != INIT dst addr it seems to drop it.

So IMHO either client or server sctp stack (or both) needs 
fixing/improving, since the stack in my system doesn't seem to be able 
to interopt with itself in a simple setup on the loopback interface 
anymore (it seems it did/does on other versions, we currently run fine 
the same setup in jenkins).


-- 
- Pau Espin Pedrol <[email protected]>         http://www.sysmocom.de/
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