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Re: [Question #276107]: Current CID in use

 

Question #276107 on rohc changed:
https://answers.launchpad.net/rohc/+question/276107

Didier Barvaux posted a new comment:
Hello,

> And at SIP BYE message sometimes if endpoint couldn't sent
> BYE message or a packet loss happens then that stream would
> be orphan and related CID will be still be occupied. At that
> point any idea to close the stream or CID ?

You may either do nothing (context recycling will happen until all
contexts are used, as now), or either implement some inactivity timeout.
N seconds without RTP packets will make the application consider that
the stream was interrupted without SIP BYE.

The timeout mechanism may work alone, without the DPI mechanism. It is
simpler and it should reach almost the same behavior. DPI detects the
end of RTP streams quicker, but with a small inactivity timeout there is
almost no difference. Because of the simplicity, it is worth a try!


> Does /proc/sys/net/ipv4/netfilter/ip_conntrack_udp_timeout_stream has anything to do at that point ?

This file controls the inactivity timeout for UDP streams in the
firewall/NAT rules handled by iptables/netfilter. There is no direct
link with the ROHC library. You may however use netfilter connection
tracking (conntrack) to detect inactivity among UDP streams. It would
avoid to re-implement the stream identification/tracking in the IP/ROHC
app.

The netfilter conntrack mechanism can warn the IP/ROHC app when a stream ends. The libnetfilter_conntrack library provides functions to do that:
* main page: https://www.netfilter.org/projects/libnetfilter_conntrack/index.html
* API documentation: http://www.netfilter.org/projects/libnetfilter_conntrack/doxygen/modules.html
* example printing creation/deletion of conntrack entries: https://git.netfilter.org/libnetfilter_conntrack/tree/examples/nfct-mnl-event.c


Regards,
Didier

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