linux-kernel - [PATCH net-next v4 1/4] net: udp: add freebind option to udp_sock

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Message-Id: <20250717115412.11424-2-richardbgobert@gmail.com>
Date: Thu, 17 Jul 2025 13:54:09 +0200
From: Richard Gobert <richardbgobert@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org,
	dsahern@...nel.org,
	razor@...ckwall.org,
	idosch@...dia.com,
	petrm@...dia.com,
	menglong8.dong@...il.com,
	richardbgobert@...il.com,
	daniel@...earbox.net,
	martin.lau@...nel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH net-next v4 1/4] net: udp: add freebind option to udp_sock_create

udp_sock_create creates a UDP socket and binds it according to
udp_port_cfg.

Add a freebind option to udp_port_cfg that allows a socket to be bound
as though IP_FREEBIND is set.

This change is required for binding vxlan sockets to their local address
when the outgoing interface is down.

Signed-off-by: Richard Gobert <richardbgobert@...il.com>
---
 include/net/udp_tunnel.h   | 3 ++-
 net/ipv4/udp_tunnel_core.c | 1 +
 net/ipv6/ip6_udp_tunnel.c  | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h
index 9acef2fbd2fd..6c1362aa3576 100644
--- a/include/net/udp_tunnel.h
+++ b/include/net/udp_tunnel.h
@@ -34,7 +34,8 @@ struct udp_port_cfg {
 	unsigned int		use_udp_checksums:1,
 				use_udp6_tx_checksums:1,
 				use_udp6_rx_checksums:1,
-				ipv6_v6only:1;
+				ipv6_v6only:1,
+				freebind:1;
 };
 
 int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
diff --git a/net/ipv4/udp_tunnel_core.c b/net/ipv4/udp_tunnel_core.c
index fce945f23069..147fd8ff4f49 100644
--- a/net/ipv4/udp_tunnel_core.c
+++ b/net/ipv4/udp_tunnel_core.c
@@ -28,6 +28,7 @@ int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
 	udp_addr.sin_family = AF_INET;
 	udp_addr.sin_addr = cfg->local_ip;
 	udp_addr.sin_port = cfg->local_udp_port;
+	inet_assign_bit(FREEBIND, sock->sk, cfg->freebind);
 	err = kernel_bind(sock, (struct sockaddr *)&udp_addr,
 			  sizeof(udp_addr));
 	if (err < 0)
diff --git a/net/ipv6/ip6_udp_tunnel.c b/net/ipv6/ip6_udp_tunnel.c
index 0ff547a4bff7..65ff44c274b8 100644
--- a/net/ipv6/ip6_udp_tunnel.c
+++ b/net/ipv6/ip6_udp_tunnel.c
@@ -40,6 +40,7 @@ int udp_sock_create6(struct net *net, struct udp_port_cfg *cfg,
 	memcpy(&udp6_addr.sin6_addr, &cfg->local_ip6,
 	       sizeof(udp6_addr.sin6_addr));
 	udp6_addr.sin6_port = cfg->local_udp_port;
+	inet_assign_bit(FREEBIND, sock->sk, cfg->freebind);
 	err = kernel_bind(sock, (struct sockaddr *)&udp6_addr,
 			  sizeof(udp6_addr));
 	if (err < 0)
-- 
2.36.1