[vlc] Re: vlm experiences

[Rémi Denis-Courmont]

Le Vendredi 23 Décembre 2005 08:39, Marian Durkovic a écrit :
> Well, not necessarily. A decent OS is expected to send back ICMP
> PORT_UNREACHABLE message if it receives packet for which no
> application is listening. This is how e.g. traceroute works.

Yes and no. Most OSes will send an ICMP port unreachable error if the 
application is closed, but not if there are behind a firewall (most of 
which drop port unreachable to circumvent UDP port scanning), or if the 
whole system stopped/got unplugged, in which case we might get an ICMP 
destination unreachable error instead.

We could consider handling these errors in the UDP stream output plugin 
(ECONNREFUSED and EDSTUNREACH errors respectively). However, I am 
afraid many users wrongly relies on these errors NOT being handled by 
VLC so far. As an example, someone might want to stream to a 
destination regardless of whether the destination is currently 
listening, rather than have to restart the stream every time the 
destination starts listening (though that will be raw UDP or RTSP-less 
RTP in that case).

Also, it fails to solve the problem when behind a firewall, or in front 
of a malicious user. Finally, I am not sure how easy it would be to 
spoof these ICMP errors, which would raise yet another DoS condition.

-- 
Rémi Denis-Courmont
http://www.simphalempin.com/home/
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