[asterisk-dev] Correct IAX2 VNAK behavior (IAX2 draft discrepancy)

Mihai Balea mihai at hates.ms
Tue Apr 3 12:53:10 MST 2007

Hi all,

I'm trying to add proper VNAK support to iaxclient (http:// 
sourceforge.net/projects/iaxclient) and I am seeing conflicting  
information... on one hand, the latest iax2 draft states:

"On receipt of a VNAK, a peer MUST retransmit all frames with a  
higher sequence number than the VNAK message's iseqno." (draft-guy- 
iax-02.txt, paragraph 6.11.3)

On the other hand, the relevant chan_iax2.c code looks like this:

static void vnak_retransmit(int callno, int last)
	struct iax_frame *f;

	AST_LIST_TRAVERSE(&iaxq.queue, f, list) {
		/* Send a copy immediately */
		if ((f->callno == callno) && iaxs[f->callno] &&
			(f->oseqno >= last)) {

... which basically means that frames higher OR EQUAL than iseqno are  

Can anybody shed some light on what is the correct behavior?

Also, I am not very familiar with chan_iax2.c, so maybe I'm missing  
something, but does this code take into account the possibility that  
sequence numbers are unsigned chars that wrap around? Doesn't seem so  
to me....


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