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<font size="+1"><tt>Hi everyone,<br>
<br>
Does anyone know/remember how to make pppd ignore certain strings on
receive? IIRC the asyncmap function was to make pppd escape out
certain sequences of data which could be interpreted by a modem to hang
up. E.g. +++ATH0<br>
<br>
NO CARRIER<br>
<br>
<br>
Just kidding. Anyway I have a piece of communications gear that
sometimes inserts a string of bits into the bitstream that comes in on
a serial port to pppd. This string of bits is always these 8 bytes: "</tt></font><font
size="+1"><tt>e9 c5 00 ca 00 02 00 40" They really screw up the PPP
frames and of course cause a frame checksum error and a TCP
retransmission from the other end for whatever data was corrupted.
Here is the beginning of a normal PPP+IP frame:<br>
<br>
0000 21 45 08 00 34 be 46 40 00 40 06 68 73 ... and so on and so forth<br>
</tt></font><font size="+1"><tt><br>
Here is the same PPP+IP frame but containing the unwanted sequence of
bits at the beginning of the frame. It's not always at the beginning,
but regardless of where in the frame it appears, it is messed up.<br>
<br>
0000 e9 c5 00 ca 00 02 00 40 21 45 08 00 34 be 46 40 .......@
!E..@..@<br>
<br>
I captured the packet traces using pppd's record option. I'm wondering
if any of you know or can suggest a way to make pppd ignore these byte
sequences which are inserted by a piece of serial communications gear?
Since it's always the same 8 bytes it should be pretty easy to
recognize.<br>
<br>
Thanks,<br>
Jim<br>
</tt></font>
<pre class="moz-signature" cols="72">--
Jim Ockers, P.Eng. (<a class="moz-txt-link-abbreviated" href="mailto:ockers@ockers.net">ockers@ockers.net</a>)
Contact info: <a class="moz-txt-link-freetext" href="http://www.ockers.ca/pason.html">http://www.ockers.ca/pason.html</a>
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