[PATCH net-next v2] ipv6: make IPV6_FREEBIND and IPV6_TRANSPARENT setsockopt lockless

[Xuanqiang Luo <xuanqiang.luo@linux.dev>]

From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>

IPV6_FREEBIND and IPV6_TRANSPARENT still take the socket lock despite
using inet_assign_bit() to update the flags shared with IP_FREEBIND
and IP_TRANSPARENT. IPv6 TCP and UDP sockets can already update these
flags without the lock through the corresponding SOL_IP options.

Move both options to the lockless setsockopt path.

Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
---
Changes:
v2:
  - Squash the two patches into one and drop the cover letter.
    (Eric Dumazet.)

v1: https://lore.kernel.org/all/20260911102418.157071-1-xuanqiang.luo@linux.dev/

 net/ipv6/ipv6_sockglue.c | 36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 1f68fb64a43ef..4b3536571c980 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -398,6 +398,21 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 
 	/* Handle options that can be set without locking the socket. */
 	switch (optname) {
+	case IPV6_FREEBIND:
+		if (optlen < sizeof(int))
+			return -EINVAL;
+		/* Shared with IP_FREEBIND. */
+		inet_assign_bit(FREEBIND, sk, valbool);
+		return 0;
+	case IPV6_TRANSPARENT:
+		if (valbool && !sockopt_ns_capable(net->user_ns, CAP_NET_RAW) &&
+		    !sockopt_ns_capable(net->user_ns, CAP_NET_ADMIN))
+			return -EPERM;
+		if (optlen < sizeof(int))
+			return -EINVAL;
+		/* Shared with IP_TRANSPARENT. */
+		inet_assign_bit(TRANSPARENT, sk, valbool);
+		return 0;
 	case IPV6_UNICAST_HOPS:
 		if (optlen < sizeof(int))
 			return -EINVAL;
@@ -666,27 +681,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		retv = 0;
 		break;
 
-	case IPV6_TRANSPARENT:
-		if (valbool && !sockopt_ns_capable(net->user_ns, CAP_NET_RAW) &&
-		    !sockopt_ns_capable(net->user_ns, CAP_NET_ADMIN)) {
-			retv = -EPERM;
-			break;
-		}
-		if (optlen < sizeof(int))
-			goto e_inval;
-		/* we don't have a separate transparent bit for IPV6 we use the one in the IPv4 socket */
-		inet_assign_bit(TRANSPARENT, sk, valbool);
-		retv = 0;
-		break;
-
-	case IPV6_FREEBIND:
-		if (optlen < sizeof(int))
-			goto e_inval;
-		/* we also don't have a separate freebind bit for IPV6 */
-		inet_assign_bit(FREEBIND, sk, valbool);
-		retv = 0;
-		break;
-
 	case IPV6_RECVORIGDSTADDR:
 		if (optlen < sizeof(int))
 			goto e_inval;

base-commit: 348ea4642f56ab3dc93621c8e3ab0ccd0e5f1782
-- 
2.43.0