On 3/31/16 7:34 AM, Roel van Meer wrote:
Hi list!
I have a problem where SIP packets sent by Asterisk do not hit the
wire, and I don't know what could cause this.
I'm running Asterisk 1.8.28_cert5 with full SIP debug. At the same
time, I'm doing a tcpdump of the traffic on the network interface. I
can see in the SIP debug log that asterisk is sending packets. Most of
the time, I can see those packets in the tcpdump, as you would expect.
However, sometimes Asterisk sends a packet that *does not show up* in the
tcpdump. Asterisk then does several retransmits (that also don't show
up).
The next packet that is not a retransmit does show up again.
This causes Asterisk to log the peer it was sending packets to
temporarily as Lagged or unreachable.
There is no outgoing firewall on this box.
Could anyone give me some pointers where to look?
A word of advice. I have been stumped before with tcpdump not showing
all packets. It turns out that the kernel can indeed prevent packets
from being captured if it is overwhelmed. The first sign of trouble is
when you hit control-C when finishing up tcpdump and get messages like
'kernel dropped X packets'. It turns out tcpdump by default tries to do
reverse DNS queries on all IPs and simply does not have enough time
under high packet loads. The solution is generally to run "tcpdump -nn"
to avoid DNS lookups.
If Asterisk logs "VERBOSE[13019] chan_sip.c: Reliably Transmitting
(NAT) to x.x.x.x:" you would expect to see that packet in a tcpdump
trace, right? What could cause this not to be so? Are there network
statistics I could look at? Is there a counter in /proc or /sys for
problems with sending packets? Anything?
If more information is necessary please do let me know.
Thanks a lot in advance,
Roel
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Technical Support
http://www.telesip.net
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