Hello everybody,

first of all, I apologize in advance if this may be a silly question (it probably is!), but I've just recently started studying the library and so I'm trying to understand how it could be used for what I need. I'm working on a WebRTC gateway, and I'm interested in implementing support for DataChannels. Since both Chrome and Firefox are using usrsctp for the purpose, it made sense to follow the same road.

That said, I've been studying the library and some examples, and there's a step that I'm missing that is currently confusing me. If I've understood correctly, the library provides a user space UDP encapsulation of SCTP messages. This means that the library itself takes care of sending and receiving UDP messages, and handling the SCTP stuff accordingly. In my case, though, considering the WebRTC scenario, ICE and DTLS are involved too: specifically, I'm using libnice for ICE and openssl for DTLS. This means that the actual communication is taken care of by libnice, and that the BIO I/O abstraction in openssl is used for implementing DTLS on top of it (since openssl can't take care of the network stuff either for the same reason).

This is where I got lost with usrsctp. Direct UDP encapsulation apparently is not viable, since the SCTP message should first of all be encrypted via DTLS, and only then transported to the destination (in my case, even using a different networking component). I guess that a way to do so could be to employ a local UDP "channel" for the sole purpose of retrieving the SCTP payload to then encapsulate in DTLS and then send to the peer, and viceversa, but I'm not sure this would work as expected.

Is there any way to configure usrsctp to work somehow like the openssl BIOs work, that is returning/handling SCTP messages that can be sent/received out-of-band on a virtual channel, or is the local UDP intermediary the only way to handle my specific scenario?

Thanks in avcance for any help you'll be able to provide me with,

Lorenzo