On 21 November 2011 12:08, Nick Kossifidis <mickflemm@xxxxxxxxx> wrote: > Some time ago we had a few reports of AR2413 cards being unable to > encrypt packets of specific lengths. > > From https://bugs.launchpad.net/ubuntu/+source/linux/+bug/568090, user > Musaraigne did some further investigation/debuging on this: > > "The cause of the high and unpredictable latencies is that packets are > dropped depending on their size. According to my tests, packet sizes > of the form > size = 128*k + 81 + m > or > size = 128*k + 105 + m > for any k>=2 and 0<=m<=7 > > are dropped randomly in 90-95% of the cases. Conversely, all other > packet sizes work fine. That seems a bit odd. Erm, how do they fail? * Does the hardware just plain fail at encrypting the frame? * Does the hardware just plain fail to _TX_ the frame of that size? (ie, if you disable crypto and take padding into account, does it fail?) * What about other encryption types? AES? TKIP? WEP? None? :-) * This is a PCIe NIC, right? Are there some kind of weird bus bugs that you're seeing with this particular NIC and this particular bus glue? Since Madwifi works, I wonder if FreeBSD also works. If so, there's only a few places I'd bet you'll find weird stuff: * how the bus is setup during attach (eg overriding PCI values); * which crypto key slots are allocated; * are you still doing split keys on that hardware? or are they combined like the ar5416+ chips are? * are you perhaps doing multi-descriptor TX frames and you've not set the encryption bits correctly? IIRC, the enctype field needs to match on all descriptors of a frame (eg, if your packet is a chain rather than a single skb, you need to make sure you're copying the descriptor fields right.) * what about the frame and header length fields? and encryption padding? are they all setup the same with madwifi versus ath5k? I bet a bit of methodical poking is going to reveal this bug. I find it rather annoying that ath5k/ath9k have lots of encryption issues but I've not had any reports of encryption on FreeBSD failing (save where the AP is totally lying about which keyidx a frame is encrypted with.) It's possible that you're seeing these errors because more people are using ath5k then FreeBSD, but still: * does freebsd-9 (wifi) work on the same hardware? Nick, can you find out if someone can send us one of these weird NICs? I'll throw it into my pile-o-old-stuff-to-test and do some regression testing with it. Adrian -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
