[asterisk-dev] [Code Review] 3603: func_jitterbuffer: fix errors and leaks caused by certain masquerade's

[Corey Farrell]

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Review request for Asterisk Developers.


Bugs: ASTERISK-22409
    https://issues.asterisk.org/jira/browse/ASTERISK-22409


Repository: Asterisk


Description
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During masquerade it is possible for the AST_JITTERBUFFER_FD to be cleared (set to -1).  This change adds a check when copying channel fd's to prevent clearing an FD with -1.  This seems to resolve the bad audio quality experienced after the masquerade.  When AST_JITTERBUFFER_FD was set to -1, this prevented the channel from polling that timer.  This caused RTP packets to be received late, and discarded.

The changes to func_jitterbuffer.c were created first.  ast_free(jbframe); is needed to prevent jbframe from leaking if it is rejected by jb_impl.  This ensures we don't start leaking packets if they are received too late or rejected by jb_impl for any other reason.

The second change to func_jitterbuffer prevents a leak of ast_null_frame's that were duplicated (ie with ast_frdup or ast_frisolate).  I believe this leak might actually be unrelated to the masquerade issue, and likely occurs for every single ast_null_frame.


Diffs
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  /branches/11/main/channel.c 415593 
  /branches/11/funcs/func_jitterbuffer.c 415593 

Diff: https://reviewboard.asterisk.org/r/3603/diff/


Testing
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Verified the scenario outlined in ASTERISK-22409 no longer experiences audio quality loss, and no longer causes leaks (tested under valgrind).  I patched asterisk to ensure that ast_frfree performed an immediate free to ensure valgrind would report any attempted use after free.

In early testing, I used debug messages instead of the added ast_frfree's - I verified the leaked frames reported by valgrind matched exactly to the number of debug messages.

For the masquerade fix I tested with some debug code that showed the old and new FD, this is how I found the valid FD being replaced by -1.  See JIRA ticket for example output.

I have not tested this issue or fix against 12+, but the relevant code is the same as 11 - func_jitterbuffer code was moved to core but still the same code.


Thanks,

Corey Farrell

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