linux-kernel - [PATCH net-next v20 23/25] ovpn: notify userspace when a peer is deleted

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Message-Id: <20250227-b4-ovpn-v20-23-93f363310834@openvpn.net>
Date: Thu, 27 Feb 2025 02:21:48 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Donald Hunter <donald.hunter@...il.com>, 
 Antonio Quartulli <antonio@...nvpn.net>, Shuah Khan <shuah@...nel.org>, 
 sd@...asysnail.net, ryazanov.s.a@...il.com, 
 Andrew Lunn <andrew+netdev@...n.ch>
Cc: Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>
Subject: [PATCH net-next v20 23/25] ovpn: notify userspace when a peer is
 deleted

Whenever a peer is deleted, send a notification to userspace so that it
can react accordingly.

This is most important when a peer is deleted due to ping timeout,
because it all happens in kernelspace and thus userspace has no direct
way to learn about it.

Signed-off-by: Antonio Quartulli <antonio@...nvpn.net>
---
 drivers/net/ovpn/netlink.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/netlink.h |  1 +
 drivers/net/ovpn/peer.c    |  1 +
 3 files changed, 67 insertions(+)

diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c
index 0838b65212aa4b077a8ecb0b21807f886a397193..efe787b15c9d9d6271da670506b5e6396f744e37 100644
--- a/drivers/net/ovpn/netlink.c
+++ b/drivers/net/ovpn/netlink.c
@@ -1094,6 +1094,71 @@ int ovpn_nl_key_del_doit(struct sk_buff *skb, struct genl_info *info)
 	return 0;
 }
 
+/**
+ * ovpn_nl_peer_del_notify - notify userspace about peer being deleted
+ * @peer: the peer being deleted
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+int ovpn_nl_peer_del_notify(struct ovpn_peer *peer)
+{
+	struct ovpn_socket *sock;
+	struct sk_buff *msg;
+	struct nlattr *attr;
+	int ret = -EMSGSIZE;
+	void *hdr;
+
+	netdev_info(peer->ovpn->dev, "deleting peer with id %u, reason %d\n",
+		    peer->id, peer->delete_reason);
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &ovpn_nl_family, 0, OVPN_CMD_PEER_DEL_NTF);
+	if (!hdr) {
+		ret = -ENOBUFS;
+		goto err_free_msg;
+	}
+
+	if (nla_put_u32(msg, OVPN_A_IFINDEX, peer->ovpn->dev->ifindex))
+		goto err_cancel_msg;
+
+	attr = nla_nest_start(msg, OVPN_A_PEER);
+	if (!attr)
+		goto err_cancel_msg;
+
+	if (nla_put_u8(msg, OVPN_A_PEER_DEL_REASON, peer->delete_reason))
+		goto err_cancel_msg;
+
+	if (nla_put_u32(msg, OVPN_A_PEER_ID, peer->id))
+		goto err_cancel_msg;
+
+	nla_nest_end(msg, attr);
+
+	genlmsg_end(msg, hdr);
+
+	rcu_read_lock();
+	sock = rcu_dereference(peer->sock);
+	if (!sock) {
+		ret = -EINVAL;
+		goto err_unlock;
+	}
+	genlmsg_multicast_netns(&ovpn_nl_family, sock_net(sock->sock->sk),
+				msg, 0, OVPN_NLGRP_PEERS, GFP_ATOMIC);
+	rcu_read_unlock();
+
+	return 0;
+
+err_unlock:
+	rcu_read_unlock();
+err_cancel_msg:
+	genlmsg_cancel(msg, hdr);
+err_free_msg:
+	nlmsg_free(msg);
+	return ret;
+}
+
 /**
  * ovpn_nl_key_swap_notify - notify userspace peer's key must be renewed
  * @peer: the peer whose key needs to be renewed
diff --git a/drivers/net/ovpn/netlink.h b/drivers/net/ovpn/netlink.h
index 5dc84c8e5e803014053faa0d892fc3a7259d40e5..8615dfc3c4720a2a550b5cd1a8454ccc58a3c6ba 100644
--- a/drivers/net/ovpn/netlink.h
+++ b/drivers/net/ovpn/netlink.h
@@ -12,6 +12,7 @@
 int ovpn_nl_register(void);
 void ovpn_nl_unregister(void);
 
+int ovpn_nl_peer_del_notify(struct ovpn_peer *peer);
 int ovpn_nl_key_swap_notify(struct ovpn_peer *peer, u8 key_id);
 
 #endif /* _NET_OVPN_NETLINK_H_ */
diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index cfe5396da584fb2b6ecbd84cd9b65446e123b6f3..b3cbe070bdfe2d129fb4b8f94401004b55cf32d5 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -689,6 +689,7 @@ static void ovpn_peer_remove(struct ovpn_peer *peer,
 	}
 
 	peer->delete_reason = reason;
+	ovpn_nl_peer_del_notify(peer);
 
 	/* append to provided list for later socket release and ref drop */
 	llist_add(&peer->release_entry, release_list);

-- 
2.45.3