On 12 June 2013 07:04, Murphy McCauley <murphy.mccau...@gmail.com> wrote: > (Sorry this isn't an actual reply and is missing context -- I wasn't on the > list when it was originally posted.) > > Simon and I have been in touch about this, and I thought I'd share my > findings for what they're worth. > > The problem is from the commit Simon mentioned > (796223f5bc3a4896e6398733c798390158479400). Specifically, it's in > netdev-linux.c in netdev_linux_send(). > > The new version always sends using the "sender" socket made by > af_packet_sock() unless the interface is a tap, in which case it sends it > using the tap fd. This differs from the old version which sent using > whatever was in the fd field of the netdev if it was available. For tap > interfaces, this was the tap fd, so the result was the same as it is now. > But for other interfaces, this held the socket opened for receiving if the > interface was listening (which was maybe never "right" in some sense and > isn't convenient anymore since this socket descriptor is no longer stored in > the non-rx netdev). > > The comments indicate that the exception is made for tap interfaces since > writing to a tap interface with an AF_PACKET socket results in receiving the > packet you just wrote. However, I don't think this behavior is limited to > taps. Since the old version of the code sent and received with the same > socket descriptor, I think the loop was fixed by the check in > dev_queue_xmit_nit() in net/core/dev.c. Since they're two different socket > descriptors now, this no longer works and you get the loop.
Ahh, it turns out Ben explained this to me when I ran into a related issue with the FreeBSD userspace implementation. Ben's message in the thread is at http://openvswitch.org/pipermail/dev/2012-July/018806.html . > I fixed it (I think) by adding a BPF packet filter on the rx socket so that > it only receives incoming packets. There's probably a better fix, but you're > welcome to the patch if you want it. I think it's worth taking a look. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
