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authorDavid Gwynne <dlg@cvs.openbsd.org>2024-11-14 01:51:58 +0000
committerDavid Gwynne <dlg@cvs.openbsd.org>2024-11-14 01:51:58 +0000
commit14b67a935975944976d9b11882248e792c7518e4 (patch)
treea3693901a3c947acaf255479116493d5ccdf4d55 /usr.sbin/nsd/zonec.h
parenta68ec967e3187390b53c55a1a4ed2565cc2fdab4 (diff)
provide a way to negotiate network offloads between the kernel and userland.
userland can request that network packets that are read from or written to the device special file get prepended with a "tun_hdr" struct. this struct contains bits which say what offloads are requested for the packet, including things like ip/tcp/udp/icmp checksums, tcp segmentation offloads, or ethernet vlan tags. userland can write a packet with any of these offloads requested into the kernel at any time, but has to request which ones it's able to handle coming from the kernel. enabling the tun_hdr struct and which offloads userland can handle is done with a new TUNSCAP ioctl. this is based on the virtio_net_hdr in linux, which jan@ actually implemented and had working with vmd. however, claudio@ and i strongly opposed to what feels like a layer violation by pulling virtio structures into the tun driver, and then trying to emulate virtio/linux semantics in our network stack, and playing catch up when the "upstream" projects decide to change the shape or meaning of these bits. tun_hdr is specific to the openbsd network stack and it's semantics, which simplifies our kernel implementation. jan has been pretty gracious about the extra work on the vmd side of things. tested by and ok jan@ ok claudio@
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