Friday, July 28, 2006

grumpy and wireless

Having much more success with the WG111T now on grumpy. I attached it to the supplied cable and left it on the TV cabinet, instead of connecting straight to the PC. Transferred several hundred MB of movie files with no issues whatsoever. I get about 830kByte/s (7MBit/s) actual throughput on wlan0 when copying files via scp. Not great, but perfectly sufficient for the occasional file transfer and daily program guide updates.

Some fun with ARP and routing

grumpy has eth0 on my internal network, and wlan0 on the WG111T. My wireless LAN is a separate leg off the firewall. Originally, it was an open WLAN with its own IP space, DHCP, etc. I set this up this way so that others can use my connection if they are within reach. However, with all the multimedia equipment now on the WLAN (and the Linux drivers supporting encryption), I turned on WEP. Not perfect security, I know, not even close, but better than nothing. But I disgress...

So, when grumpy has wlan0 enabled, I can ping grumpy.wlan from the wired network iff I ifdown eth0.
Looks like either the kernel on grumpy sees the directly attached network and tries to reply to ICMP requests originating on the wired LAN via eth0, even though they were sent to wlan0 via the firewall. This happens even when the cable is disconnected, resulting in an (incomplete) ARP entry. So, in order to access grumpy from the wired LAN, eth0 needs to be ifdown when the cable is disconnected.
However, I want it up if the cable is connected. Now, how do I do that?
ifplugd to the rescue. It's very straight-forward, easy to configure. It detects when the network cable is plugged in and configures and unconfigures eth0 accordingly.
The catch?
MythTV is configured to use the IP address of eth0 for the backend server. If I unconfigure the interface, mythfrontend is getting *very* unhappy. *sigh*
Let's use for now...

After leaving grumpy running overnight in this config, wlan0 was dead _again_ this morning. rmmod ehci_hcd . Let's see if it's really the ehci module causing issues. Of course, that drops the transfer rate to a measly 230kByte/s.

grumpy has been running for two weeks with no wireless drops. So it really is the ehci_hcd kernel module giving me grief. I wonder if going to kernel 2.6.17 would help, but ah, the pain of rebuilding all the drivers for the TV cards. otoh, going to ivtv 0.6.x might fix closed captioning support. Hmmmm.

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