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4ae45b10
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Ermal Luçi
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# RTP - Real-time Transport Protocol - RFC 3550
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66f2dd0e
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Ermal Lu?i
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# Pattern attributes: ok overmatch undermatch fast fast
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4ae45b10
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Ermal Luçi
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# Protocol groups: streaming_video ietf_internet_standard
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# Wiki: http://www.protocolinfo.org/wiki/RTP
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66f2dd0e
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Ermal Lu?i
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# Copyright (C) 2008 Matthew Strait, Ethan Sommer; See ../LICENSE
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4ae45b10
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Ermal Luçi
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#
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# RTP headers are *very* short and compact. They have almost nothing in
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66f2dd0e
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Ermal Lu?i
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# them that can be matched by l7-filter. As RTP connections take place
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# between even numbered ports, you should probably check for that before
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# applying this pattern. If you want to match them along with their
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# associated SIP packets, you might try setting up some iptables rules
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# that watch for SIP packets and then also match any other UDP packets
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# that are going between the same two IP addresses.
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4ae45b10
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Ermal Luçi
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#
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# I think we can count on the first bit being 1 and the second bit being
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# 0 (meaning protocol version 2). The next two bits could go either way,
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# but in the example I've seen, they are zero, so I'll assume they are
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# usually zero. The next four bits are a count of "contributing source
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# identifiers". I'm not sure how big that could be, but in the example
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# I've seen, they're zero, so I'll assume they're usually zero. So that
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66f2dd0e
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Ermal Lu?i
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# gives us ^\x80. The next bit is a tossup. Next is the payload type, 7
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# bits. I've taken likely values from the WireShark code: 0-34, 96-127
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# (decimal). The rest of the header is random numbers (sequence number,
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# timestamp, synchronization source identifier), so that's no help at
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# all.
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4ae45b10
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Ermal Luçi
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rtp
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66f2dd0e
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Ermal Lu?i
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^\x80[\x01-"`-\x7f\x80-\xa2\xe0-\xff]?..........*\x80
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4ae45b10
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Ermal Luçi
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# Might also try this. It's a bit slower (one packet and not too much extra
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# regexec load) and a bit more accurate:
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66f2dd0e
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Ermal Lu?i
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#^\x80[\x01-"`-\x7f\x80-\xa2\xe0-\xff]?..........*\x80.*\x80
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