netdev - [PATCH net-next] ip6_tunnel: enable to change proto of fb tunnels

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Message-ID: <20250617160126.1093435-1-nicolas.dichtel@6wind.com>
Date: Tue, 17 Jun 2025 18:01:25 +0200
From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
To: "David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: [PATCH net-next] ip6_tunnel: enable to change proto of fb tunnels

This is possible via the ioctl API:
> ip -6 tunnel change ip6tnl0 mode any

Let's align the netlink API:
> ip link set ip6tnl0 type ip6tnl mode any

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
---
 net/ipv6/ip6_tunnel.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 894d3158a6f0..03ad45189621 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -2053,8 +2053,17 @@ static int ip6_tnl_changelink(struct net_device *dev, struct nlattr *tb[],
 	struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
 	struct ip_tunnel_encap ipencap;
 
-	if (dev == ip6n->fb_tnl_dev)
-		return -EINVAL;
+	if (dev == ip6n->fb_tnl_dev) {
+		if (!data[IFLA_IPTUN_PROTO]) {
+			NL_SET_ERR_MSG(extack,
+				       "Only protocol can be changed for fallback tunnel");
+			return -EINVAL;
+		}
+
+		ip6_tnl_netlink_parms(data, &p);
+		ip6_tnl0_update(netdev_priv(ip6n->fb_tnl_dev), &p);
+		return 0;
+	}
 
 	if (ip_tunnel_netlink_encap_parms(data, &ipencap)) {
 		int err = ip6_tnl_encap_setup(t, &ipencap);
-- 
2.47.1