[LARTC] RTP packet filtering

[LARTC] RTP packet filtering

[Rafael Gustavo Gassner]

Hi all,

     I need to allow RTP packages on my network, but don´t want to 
allow all UDP (And then ill try to priorize it), so i think i could do 
that using u32. I can see that all packages that are RTP have a field 
80 00, as shown below (It is the protocol version and payload type):

0000 xx xx xx xx xx xx xx xx     xx xx xx xx xx xx xx xx
0010 xx xx xx xx xx xx xx xx     xx xx xx xx xx xx xx xx
0020 xx xx xx xx xx xx xx xx     xx xx 80 00 xx xx xx xx

     Could someone give me a tip on how should the u32 filter look like?

Thanks a lot,

Rafael Gustavo Gassner



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Re: [LARTC] RTP packet filtering

[Lawrence MacIntyre]

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I havent't tested this, but it should work:

tc filter ... \
	match ip protocol 17 0xff \
	match u16 0x8000 0xffff at nexthdr + 8

The first match selects udp and the second selects the protocol
information and payload type.  Note that there is more info there than
just the protocol version (no padding, no extension, no CSIDs).  Also,
why is the type 00?

On Tue, 2003-09-30 at 17:13, Rafael Gustavo Gassner wrote:
> Hi all,
> 
>      I need to allow RTP packages on my network, but don´t want to 
> allow all UDP (And then ill try to priorize it), so i think i could do 
> that using u32. I can see that all packages that are RTP have a field 
> 80 00, as shown below (It is the protocol version and payload type):
> 
> 0000 xx xx xx xx xx xx xx xx     xx xx xx xx xx xx xx xx
> 0010 xx xx xx xx xx xx xx xx     xx xx xx xx xx xx xx xx
> 0020 xx xx xx xx xx xx xx xx     xx xx 80 00 xx xx xx xx
> 
>      Could someone give me a tip on how should the u32 filter look like?
> 
> Thanks a lot,
> 
> Rafael Gustavo Gassner
> 
> 
> 
> _______________________________________________
> LARTC mailing list / LARTC@mailman.ds9a.nl
> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
-- 
    Lawrence MacIntyre     865.574.8696     lpz@ornl.gov
               Oak Ridge National Laboratory
High Performance Information Infrastructure Technology Group


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