my (old) laptop is unable to establish a wireless link over a cardbus WLAN card. After disabling WLAN encryption, I am able to send an echo request and there is an echo response from the server. Using WireShark, I can see that the ICMP checksum is wrong because the ICMP data is corrupted. Typically, 4 bytes "62 63 64 65" are blanked to "00 00 00 00" in the ICMP data field. Always the same locations are blanked:
Echo request ICMP data: 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 61 62 63 64 65 66 67 68 69
Echo response ICMP data: 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 61 00 00 00 00 66 67 68 69
The laptop has WinXP SP3 installed. The cardbus card works fine in another laptop.
Thanks for help. manuel
asked 15 Jul '12, 14:52
The ICMP checksum is probably not really wrong, and neither is the ICMP data corrupt. What you're doing is capturing on a system that is sending out packets through a network card that helps the system by taking over certain tasks from the CPU. If that happens, the calculation of checksums for IP, TCP, ICMP etc. is done just in that last moment before the packet goes out on to the actual physical medium, which is way after Wireshark has already picked it up. Google for "checksum offloading" or take a look here: http://www.wireshark.org/docs/wsug_html_chunked/ChAdvChecksums.html
If you don't believe me you can easily check this: only packets going OUT are affected. Capture them at the other node (as incoming packets) and you'll see they'll have perfect checksums.
I guess the cardbus card has some issues when trying to establish an encryption when running on Windows XP (or does the other laptop also run Windows XP? In that case you need to find out what the difference between the two systems is).
If you can't find any other reason you should probably try to talk to the vendor about it.
answered 15 Jul '12, 21:07
edited 15 Jul '12, 21:09
There should be no data modification in the payload. Sounds like your PCCARD is broken. If the card works in another laptop, your PCCARD slot might be broken (or something else on that laptop). Could be a strange driver problem as well.
Try to boot the laptop with a linux distribution (maybe Ubuntu) and check if the PCCARD works there. The old ones will be detected quite well, if they are not too old ;-)
If it works on linux, it's a driver problem. Try to reinstall the driver. If it's the same on linux, I assume it's a hardware problem (see above).
answered 16 Jul '12, 12:52
Kurt Knochner ♦
edited 16 Jul '12, 13:00