On 20/01/2025 11:09, Sabrina Dubroca wrote:
2025-01-19, 14:12:05 +0100, Antonio Quartulli wrote:
On 17/01/2025 18:12, Sabrina Dubroca wrote:
2025-01-17, 13:59:35 +0100, Antonio Quartulli wrote:
On 17/01/2025 12:48, Sabrina Dubroca wrote:
2025-01-13, 10:31:39 +0100, Antonio Quartulli wrote:
int ovpn_nl_peer_new_doit(struct sk_buff *skb, struct genl_info *info) {
- return -EOPNOTSUPP;
- struct nlattr *attrs[OVPN_A_PEER_MAX + 1];
- struct ovpn_priv *ovpn = info->user_ptr[0];
- struct ovpn_socket *ovpn_sock;
- struct socket *sock = NULL;
- struct ovpn_peer *peer;
- u32 sockfd, peer_id;
- int ret;
- /* peers can only be added when the interface is up and running */
- if (!netif_running(ovpn->dev))
return -ENETDOWN;Since we're not under rtnl_lock here, the device could go down while we're creating this peer, and we may end up with a down device that has a peer anyway.
hmm, indeed. This means we must hold the rtnl_lock to prevent ending up in an inconsistent state.
I'm not sure what this (and the peer flushing on NETDEV_DOWN) is trying to accomplish. Is it a problem to keep peers when the netdevice is down?
This is the result of my discussion with Sergey that started in v23 5/23:
https://lore.kernel.org/r/netdev/20241029-b4-ovpn-v11-5-de4698c73a25@openvpn...
The idea was to match operational state with actual connectivity to peer(s).
Originally I wanted to simply kee the carrier always on, but after further discussion (including the meaning of the openvpn option --persist-tun) we agreed on following the logic where an UP device has a peer connected (logic is slightly different between MP and P2P).
I am not extremely happy with the resulting complexity, but it seemed to be blocker for Sergey.
[after re-reading that discussion with Sergey]
I don't understand why "admin does 'ip link set tun0 down'" means "we should get rid of all peers. For me the carrier situation goes the other way: no peer, no carrier (as if I unplugged the cable from my ethernet card), and it's independent of what the user does (ip link set XXX up/down). You have that with netif_carrier_{on,off}, but flushing peers when the admin does "ip link set tun0 down" is separate IMO.
The reasoning was "the user is asking the VPN to go down - it should be assumed that from that moment on no VPN traffic whatsoever should flow in either direction". Similarly to when you bring an Eth interface dwn - the phy link goes down as well.
Does it make sense?
I'm not sure. If I turn the ovpn interface down for a second, the peers are removed. Will they come back when I bring the interface back up? That'd have to be done by userspace (which could also watch for the DOWN events and tell the kernel to flush the peers) - but some of the peers could have timed out in the meantime.
If I set the VPN interface down, I expect no packets flowing through that interface (dropping the peers isn't necessary for that), but all non-data (key exchange etc sent by openvpn's userspace) should still go through, and IMO peer keepalive fits in that "non-data" category.
This was my original thought too and my original proposal followed this idea :-)
However Sergey had a strong opinion about "the user expect no traffic whatsoever".
I'd be happy about going again with your proposed approach, but I need to be sure that on the next revision nobody will come asking to revert this logic again :(
What does openvpn currently do if I do ip link set tun0 down ; sleep 5 ; ip link set tun0 up with a tuntap interface?
I think nothing happens, because userspace doesn't monitor the netdev status. Therefore, unless tun closed the socket (which I think it does only when the interface is destroyed), userspace does not even realize that the interface went down.
Regards,