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@xxxxxxxxxxx/
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,
--
Antonio Quartulli
OpenVPN Inc.
