"Michael S. Tsirkin" <m...@redhat.com> writes: > On Mon, May 20, 2013 at 03:43:51PM +0200, Paolo Bonzini wrote: >> Is there a story behind skipping virtio-net feature bits 2..4? >> >> Paolo > > Bits 3-4 now :) > I'm curious too.
Not a good one :) The year is 2007. virtio_net was the posterchild of free expression and crazy experimentation. We were all so very young... The original host TSO bits in virtio_net were like so: #define VIRTIO_NET_F_TSO4 1 #define VIRTIO_NET_F_UFO 2 #define VIRTIO_NET_F_TSO4_ECN 3 #define VIRTIO_NET_F_TSO6 4 But I decided we might as well offer all or nothing, and if you couldn't handle one, you could just do it in software: #define VIRTIO_NET_F_GSO 6 Reading the git commits, it seems Linux didn't do UFO in software (at the time, at least), so the bits were split out again, with the explicit _HOST_ in the names: #define VIRTIO_NET_F_HOST_TSO4 11 /* Host can handle TSOv4 in. */ #define VIRTIO_NET_F_HOST_TSO6 12 /* Host can handle TSOv6 in. */ #define VIRTIO_NET_F_HOST_ECN 13 /* Host can handle TSO[6] w/ ECN in. */ #define VIRTIO_NET_F_HOST_UFO 14 /* Host can handle UFO in. */ This was all before there was a host implementation, so we were playing. ie. the bits are perfectly fine for reuse. Cheers, Rusty.
