> On 7. Jun 2020, at 14:18, Andreas Fink <afink@xxxxxxxxxxxxx> wrote: > > Hello folks, > > I run into a strange issue with SCTP under Linux and I'm not sure whats the right approach to fix this. > > I have a listener thread which listens on a port for multiple inbound connections > I have a sender thread which sends packets to peers by using the same socket and doing a sctp_sendv call. > Sockets are always in non blocking mode. So a single SOCK_SEQPACKET socket for sending and receiving, right? > > When the remote side gets stopped (process killed), the sctp_sendv starts returning 0 and errno is set to EAGAIN and we constantly retry. When it returns 0, you can't look at errno. errno is only set to a correct value, if -1 is returned. If you killed the peer, I would assume that there is an SCTP message containing an ABORT chunk in the wire. Is that true? If that is true, you could subscribe to SCTP_ASSOC_CHANGE notification, which should tell you. Best regards Michael > We somehow didn't catch that this socket was down and end up in a busy loop (which we now fail after a certain amount of retries). > > My question to you is whats the correct way to deal with EAGAIN here? Why are we not catching the assoc being down? > We have a sender thread and a receiver thread. The receiver thread is listening to events and should know. > Furthermore if the assoc is down the sctp_sendv could simply return something like socket not connected error instead of EAGAIN. > > Or what am I missing here? > > > Andreas > > PS: above was under Linux Debian Kernel 5.4.0-0.bpo.4.
