[Linphone-developers] patch to improve handling of multiple streams with different media encryption

[Eli Burke]

This patch improves Linphone’s handling of incoming calls with multiple streams that specify different media encryption types. 

For example, if the incoming SDP specifies SAVP on stream 0, and AVP on stream 1

m=audio 31076 RTP/SAVP 9 3 0 8 101

m=audio 31076 RTP/AVP 9 3 0 8 101

the current implementation determines that SRTP is not available because stream 1 does not support it, and attempts to set crypto=None. That fails because stream 0’s media encryption does not match None. 

This occurs because the sal_media_description_has_NNNN() functions short circuit and return FALSE if they encounter a stream with a differing encryption type. We believe that the intent was actually to ensure that any offered media encryption type be available for each stream media type (Audio, Video, Text). 

My colleague Trevor Alpeter has re-written a couple of the sal_* functions to ensure that each media encryption type is detected as long as it is offered for each stream media type listed. In the example above, sal_media_description_has_strp() now returns TRUE.

multiple_streams_crypto.patch
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