RFC: wg syncpeers wg0 wireguard.conf

[Kalin KOZHUHAROV]

On Tue, Jun 11, 2019 at 11:08 PM Lonnie Abelbeck
<lists at lonnie.abelbeck.com> wrote:
> > On Jun 11, 2019, at 12:28 PM, Jason A. Donenfeld <Jason at zx2c4.com> wrote:
> >
> > One of the things that always goes wrong with "sync" algorithms in
> > software -- and the commit above at the moment is no exception -- is
> > that they're kind of racey. In order to synchronize, we have to read
> > the current state, compare it, and then set our new state. But in
> > between, the state could have changed out from underneath us. One
> > strategy for this is to just do nothing and put some notice in the man
> > page. Another strategy is to read back the result at the end, compare
> > it, and loop like this until we reach the stable state. This then
> > requires implementing some equality function.
>
> If "wg" does not offer "syncconf", users will be hacking together their own sync solution and it will no doubt be more racey than your tight code.
>
+1

> > The other thing I was wondering is: aside from performance and races
> > as described above, why not just make this the functionality of
> > `setconf`? Then there's be no need to introduce a new subcommand. In
> > otherwords, the idea would be to make `setconf` not destroy existing
> > peers if we're going to be re-adding them again.
>
> I vote to keep "setconf" as is, with the addition of the "syncconf" subcommand.
> This keeps "setconf" faster, and unchanged, typically used for initial configuration.
> Then "syncconf" would typically be used for followup live updates.
>
I guess you've seen Cisco (an other) network devices having running
and the startup config. I think this is quite similar idea here.
While I understand the need to sync, looking at the code it is more of
an `updateconf` (i.e. file -> memory) operation, while I'd expect sync
to be 2-way sync where startup/saved/disk/file/whatever config is
equal to the running/current/memory/state/whatever config by some
automagic algorithm.

Looking from a high place, a bit tired and before going to bed, these
are my thoughts:

AFAIR, the way to save config is `wg showconf wg0 >wg0.conf` (running
-> startup)...
Then why is `wg setconf` requiring a file, i.e. why not `wg setconf
wg0 <wg0.conf` ??  (to be able to use easily sudo?) If nothing
special, I'd rather see `wg setconf` read from STDIN.
We have also `wg addconf` ... hmm

I'd suggest drop addconf altogether and rename the proposed syncconf
to `updateconf` (other software uses reload, but it is not clear in
this usecase).
Do we need the reverse of `wg setconf` without the redirect like `wg
saveconf wg0 wg0.conf` ? I don't think so.
Yes, I am sure it "will break userspace", but it is better to do it
now than later.

Cheers,
Kalin.