I have a *nasty* ppp problem I'm trying to solve, but I'm running
out of steam debugging it.
Environment:
- Laptop running kernel 2.1.125, latest Debian slink, ppp 2.3.5. Fails.
- Desktop running kernel 2.1.125, latest Debian slink, ppp 2.3.5. Works.
In addition to my usual desktop ppp connection, I set up the exact same
modem, cables, etc. on an extra serial port aand configured and tested
the laptop's ppp connection from my desktop. Fine.
The laptop also boots Windows. PPP works fine from there. :-(
>From the laptop, however, it seems like it is never receiving TCP
packets from the middle of a connection. It sends packets fine, and
gets SYN or FIN packets fine, but even though when running with kdebug
9, I can see bytes arrive that look like a login prompt when I telnet
in to somewhere, the packets never arrive as far as tcpdump and the
application are concerned.
I can ping the laptop fine, and TCP connects to it have the same
"nothing after the initial SYN gets through" problem.
I'm starting to suspect a VJ header compression bug (since I know it
doesn't compress SYN or FIN packets). But it should also send retransmits
uncompressed, and retransmits aren't getting through.
I moved ppp on the laptop from a loadable module to compiled-in like
the desktop was, and did a "make clean", but that hasn't helped. I'm
not getting any "Bad TCP checksum" messages that I'd expect from bad
decompression.
I'm diving into kernel debugging at the moment.
But if anyone has any ideas, I'm certainly interested.
I'm going to check which compilers the kernels are compiled with.
(I think it's egcs on the desktop and gcc on the laptop, so there's
a possible discrepancy I can eliminate.)
--
-Colin
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