[PATCH ovpn net v3 1/6] ovpn: preserve IPv6 scope id for netlink peer endpoints

ovpn accepts OVPN_A_PEER_REMOTE_IPV6_SCOPE_ID and reports
bind->remote.in6.sin6_scope_id in peer dumps, but the netlink endpoint
parser never copied the attribute into the sockaddr_in6 used to create or
update the peer bind.

As a result, an IPv6 link-local remote endpoint configured through
netlink loses its interface scope, unlike on the peer float path where
ipv6_iface_scope_id populates the field. The UDPv6 output path then
builds a flow with flowi6_oif set to zero and route lookup can fail or
select the wrong interface.

Copy the scope id when parsing non-v4-mapped IPv6 remote endpoints. The
existing precheck already rejects the scope-id attribute for IPv4 and
v4-mapped IPv6 remotes.

Fixes: 1d36a36f6d53 ("ovpn: implement peer add/get/dump/delete via netlink")
Signed-off-by: Ralf Lici <[email protected]>
---
No changes since v2 https://lore.kernel.org/openvpn-devel/87f7c1a6eea0005a067889e9b6f73fc6bd4f40e1.1785308184.git.ralf@mandelbit.com/

No changes since v1 https://lore.kernel.org/openvpn-devel/87f7c1a6eea0005a067889e9b6f73fc6bd4f40e1.1785253480.git.ralf@mandelbit.com/

 drivers/net/ovpn/netlink.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ovpn/netlink.c b/drivers/net/ovpn/netlink.c
index 4dad85294198..2ba762082acc 100644
--- a/drivers/net/ovpn/netlink.c
+++ b/drivers/net/ovpn/netlink.c
@@ -100,6 +100,8 @@ static bool ovpn_nl_attr_sockaddr_remote(struct nlattr **attrs,
 	struct sockaddr_in6 *sin6;
 	struct sockaddr_in *sin;
 	struct in6_addr *in6;
+	struct nlattr *scope;
+	u32 scope_id = 0;
 	__be16 port = 0;
 	__be32 *in;
 
@@ -114,6 +116,9 @@ static bool ovpn_nl_attr_sockaddr_remote(struct nlattr **attrs,
 	} else if (attrs[OVPN_A_PEER_REMOTE_IPV6]) {
 		ss->ss_family = AF_INET6;
 		in6 = nla_data(attrs[OVPN_A_PEER_REMOTE_IPV6]);
+		scope = attrs[OVPN_A_PEER_REMOTE_IPV6_SCOPE_ID];
+		if (scope)
+			scope_id = nla_get_u32(scope);
 	} else {
 		return false;
 	}
@@ -126,6 +131,7 @@ static bool ovpn_nl_attr_sockaddr_remote(struct nlattr **attrs,
 		if (!ipv6_addr_v4mapped(in6)) {
 			sin6 = (struct sockaddr_in6 *)ss;
 			sin6->sin6_port = port;
+			sin6->sin6_scope_id = scope_id;
 			memcpy(&sin6->sin6_addr, in6, sizeof(*in6));
 			break;
 		}
-- 
2.55.0