Long outage when changing private key

[Jason A. Donenfeld]

Hi Derrick,

The fix is probably this:

diff --git a/src/netlink.c b/src/netlink.c
index 3458c817..6b6a3f7a 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -539,6 +539,7 @@ static int wg_set_device(struct sk_buff *skb, struct genl_info *info)
 					 peer_list) {
 			if (!wg_noise_precompute_static_static(peer))
 				wg_peer_remove(peer);
+			wg_noise_keypairs_clear(&peer->keypairs);
 		}
 		wg_cookie_checker_precompute_device_keys(&wg->cookie_checker);
 		up_write(&wg->static_identity.lock);

But the idea was originally that we wouldn't clear transport sessions
when the private key or peer preshared key changes, to allow for various
types of negotiated rotations with a grace period, in particular the
case of preshared keys for post quantum protocols. However, I can see
how the private key case causes problems for you, since changing the
public key on a peer is akin to removing and adding a different peer,
and so those transport sessions are lost in the process. In other words,
you might have a point.

Regards,
Jason