[pjsip] DTLS-SRTP. No SRTP transmission

Christian Scheid cscheid at appguard.us
Wed Apr 11 11:16:03 EDT 2018


Guys,

the good people from pjsip support pointed me in the right direction: the
offerer wasn't initiating the DTLS-SRTP handshake.
The reason was that the RTPEngine needed to be configured with a DTLS role
of 'active', which was 'passive' before.

Hope this helps others.

Cheers,

Chris

On Tue, Apr 10, 2018 at 5:08 PM, Christian Scheid <cscheid at appguard.us>
wrote:

> Guys,
>
> we are currently trying to get DTLS-SRTP working with two Android clients
> and a Kamailio/RTPEngine server. It's been a bit rough, to say the least.
> So I could use some help. I also pledge to buy anyone who can assist a six
> pack of beer. I'll Paypal it to you. :)
>
> So what's happening? In short: nothing. No sound. Which is what I'm
> desperately craving for!
> The DTLS handshake completes fine between the two parties but when it
> comes to transmitting srtp, the sender gives me:
> Error sending RTP: Invalid operatiion (PJ_EINVALIDOP)
>
> In the receiver logs with DTLS_DEBUG turned on I see:
> DTLS-SRTP ssl_on_recv_packet
> dtls0x7bcd47568000  SSL_read() error: Unknown OpenSSL error 0
> dtls0x7bcd47568000  SSL_get_error: 5: Unknown OpenSSL error 0
> dtls0x7bcd47568000  DTLS-SRTP ssl_flush_wbio
> strm0x7bcd3b927c28 !Error sending RTP: Invalid operation (PJ_EINVALIDOP)
> dtls0x7bcd47568000 !DTLS-SRTP receiving 1045 bytes
>
> SSL_get_error 5 means: SSL_ERROR_SYSCALL. Some non-recoverable I/O error
> occurred.
> Uhhhh, ugly!
>
> In the Wireshark output I see UDP packets from the receiver but nothing
> from the sender. Hmm. Perhaps a RTPEngine config issue?
>
> So I uploaded sender, receiver and wireshark logs here:
> https://www.dropbox.com/s/bwigoqa54ih1blx/Export.zip?dl=0
>
> If anyone could give me a hint on where to go from here, I'd be eternally
> grateful, Since... I've... banged... my... head... against... the... walll.
> with this one... a lot.
>
> You wanna ask a stupid question? Don't be shy, go ask a stupid question.
> I'm a pj beginner. Any stupid quest may put me on the right track.
>
> Thanks!
>
> Chris
>
>
>
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