On Thu, 12 Jan 2017 14:01:07 +0100 "Jason A. Donenfeld" <ja...@zx2c4.com> wrote:
> Hey folks, > > A few months ago I switched away from using netlink in wireguard, > preferring instead to use ioctl. I had come up against limitations in > rtnetlink, and ioctl presented a straightforward hard to screw-up > alternative. The very simple API is documented here: > https://git.zx2c4.com/WireGuard/tree/src/uapi.h > > This works well, and I'm reluctant to change it, but as I do more > complicated things, and as kernel submission time looms nearer, I'm > kept up at night by the notion that maybe I ought to give netlink > another chance. But how? > > For each wireguard interface, there are three types of structures for > userspace to configure. There is one wgdevice for each interface. Each > wgdevice has a variable amount (up to 2^16) of wgpeers. Each wgpeer > has a variable amount (up to 2^16) of wgipmasks. I'd like an interface > to get and set all of these at once, atomically. > > Presently, with the ioctl, I just have a simple get ioctl and a simple > set ioctl. The set one passes a user space pointer, which is read > incrementally in kernel space. The get one will first return how much > userspace should allocate, and then when called again will write > incrementally into a provided userspace buffer up to a passed-in > maximum number of bytes. Very basic, I'm quite happy. > > When I had tried to do this priorly with netlink, I did it by defining > changelink and fill_info in rtnl_link_ops. For changelink, I iterated > through the netlink objects, and for fill_info, I filled in the skb > with netlink objects. This was a bit more complex but basically > worked. Except netlink skbs have a maximum size and are buffered, > which means things broke entirely when trying to read or write logs of > wgpeers or lots of wgipmasks. So, the meager interfaces afforded to me > by rtnl_link_ops are insufficient. Doing anything beyond this, either > by registering new rtnetlink messages, or by using generic netlink, > seemed overwhelmingly complex and undesirable. > > So I'm wondering -- is there a good way to be doing this with netlink? > Or am I right to stay with ioctl? > > Thanks, > Jason It is up to you but I doubt that code with new private ioctl's will be accepted upstream. If you want full review then post for inclusion upstream. If you just want to maintain it is a private fork, go ahead and do what you want and suffer the consequences.
