Merge branch 'mptcp-pm-netlink-announce-server-side-flag'

Matthieu Baerts says:

====================
mptcp: pm: netlink: announce server-side flag

Now that the 'flags' attribute is used, it seems interesting to add one
flag for 'server-side', a boolean value.

Here are a few patches related to the 'server-side' attribute:

- Patch 1: only announce this attribute on the server side.

- Patch 2: announce the 'server-side' flag when this is the case.

- Patch 3: deprecate the 'server-side' attribute.

- Patch 4: use the 'server-side' flag in the selftests.

- Patches 5, 6: small cleanups when working on code around.
====================

Link: https://patch.msgid.link/20250919-net-next-mptcp-server-side-flag-v1-0-a97a5d561a8b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

7 files changed, 28 insertions, 17 deletions

diff --git a/Documentation/netlink/specs/mptcp_pm.yaml b/Documentation/netlink/specs/mptcp_pm.yaml
index d1b4829b580a..ba30a40b9dbf 100644
--- a/Documentation/netlink/specs/mptcp_pm.yaml
+++ b/Documentation/netlink/specs/mptcp_pm.yaml
@@ -28,13 +28,13 @@ definitions:
           traffic-patterns it can take a long time until the
           MPTCP_EVENT_ESTABLISHED is sent.
           Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6, sport,
-          dport, server-side, [flags].
+          dport, [server-side], [flags].
       -
         name: established
         doc: >-
           A MPTCP connection is established (can start new subflows).
           Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6, sport,
-          dport, server-side, [flags].
+          dport, [server-side], [flags].
       -
         name: closed
         doc: >-
@@ -266,6 +266,7 @@ attribute-sets:
       -
         name: server-side
         type: u8
+        doc: "Deprecated: use 'flags'"
 
 operations:
   list:
diff --git a/include/uapi/linux/mptcp.h b/include/uapi/linux/mptcp.h
index 5fd5b4cf75ca..15eef878690b 100644
--- a/include/uapi/linux/mptcp.h
+++ b/include/uapi/linux/mptcp.h
@@ -32,12 +32,13 @@
 #define MPTCP_INFO_FLAG_REMOTE_KEY_RECEIVED	_BITUL(1)
 
 #define MPTCP_PM_EV_FLAG_DENY_JOIN_ID0		_BITUL(0)
+#define MPTCP_PM_EV_FLAG_SERVER_SIDE		_BITUL(1)
 
-#define MPTCP_PM_ADDR_FLAG_SIGNAL                      (1 << 0)
-#define MPTCP_PM_ADDR_FLAG_SUBFLOW                     (1 << 1)
-#define MPTCP_PM_ADDR_FLAG_BACKUP                      (1 << 2)
-#define MPTCP_PM_ADDR_FLAG_FULLMESH                    (1 << 3)
-#define MPTCP_PM_ADDR_FLAG_IMPLICIT                    (1 << 4)
+#define MPTCP_PM_ADDR_FLAG_SIGNAL		_BITUL(0)
+#define MPTCP_PM_ADDR_FLAG_SUBFLOW		_BITUL(1)
+#define MPTCP_PM_ADDR_FLAG_BACKUP		_BITUL(2)
+#define MPTCP_PM_ADDR_FLAG_FULLMESH		_BITUL(3)
+#define MPTCP_PM_ADDR_FLAG_IMPLICIT		_BITUL(4)
 
 struct mptcp_info {
 	__u8	mptcpi_subflows;
diff --git a/include/uapi/linux/mptcp_pm.h b/include/uapi/linux/mptcp_pm.h
index 7359d34da446..bf44a5cf5b5a 100644
--- a/include/uapi/linux/mptcp_pm.h
+++ b/include/uapi/linux/mptcp_pm.h
@@ -16,10 +16,10 @@
  *   good time to allocate memory and send ADD_ADDR if needed. Depending on the
  *   traffic-patterns it can take a long time until the MPTCP_EVENT_ESTABLISHED
  *   is sent. Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6,
- *   sport, dport, server-side, [flags].
+ *   sport, dport, [server-side], [flags].
  * @MPTCP_EVENT_ESTABLISHED: A MPTCP connection is established (can start new
  *   subflows). Attributes: token, family, saddr4 | saddr6, daddr4 | daddr6,
- *   sport, dport, server-side, [flags].
+ *   sport, dport, [server-side], [flags].
  * @MPTCP_EVENT_CLOSED: A MPTCP connection has stopped. Attribute: token.
  * @MPTCP_EVENT_ANNOUNCED: A new address has been announced by the peer.
  *   Attributes: token, rem_id, family, daddr4 | daddr6 [, dport].
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 483ddbb9ec40..d5b383870f79 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -413,8 +413,13 @@ static int mptcp_event_created(struct sk_buff *skb,
 	if (err)
 		return err;
 
-	if (nla_put_u8(skb, MPTCP_ATTR_SERVER_SIDE, READ_ONCE(msk->pm.server_side)))
-		return -EMSGSIZE;
+	if (READ_ONCE(msk->pm.server_side)) {
+		flags |= MPTCP_PM_EV_FLAG_SERVER_SIDE;
+
+		/* Deprecated, and only set when it is the server side */
+		if (nla_put_u8(skb, MPTCP_ATTR_SERVER_SIDE, 1))
+			return -EMSGSIZE;
+	}
 
 	if (READ_ONCE(msk->pm.remote_deny_join_id0))
 		flags |= MPTCP_PM_EV_FLAG_DENY_JOIN_ID0;
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d9fbddb99ad0..735a209d4072 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -545,11 +545,10 @@ static void mptcp_cleanup_rbuf(struct mptcp_sock *msk, int copied)
 	}
 }
 
-static bool mptcp_check_data_fin(struct sock *sk)
+static void mptcp_check_data_fin(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	u64 rcv_data_fin_seq;
-	bool ret = false;
 
 	/* Need to ack a DATA_FIN received from a peer while this side
 	 * of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
@@ -588,12 +587,10 @@ static bool mptcp_check_data_fin(struct sock *sk)
 			break;
 		}
 
-		ret = true;
 		if (!__mptcp_check_fallback(msk))
 			mptcp_send_ack(msk);
 		mptcp_close_wake_up(sk);
 	}
-	return ret;
 }
 
 static void mptcp_dss_corruption(struct mptcp_sock *msk, struct sock *ssk)
diff --git a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
index 93fea3442216..d4981b76693b 100644
--- a/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
+++ b/tools/testing/selftests/net/mptcp/pm_nl_ctl.c
@@ -2,6 +2,7 @@
 
 #include <errno.h>
 #include <error.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -113,6 +114,8 @@ static int capture_events(int fd, int event_group)
 		error(1, errno, "could not join the " MPTCP_PM_EV_GRP_NAME " mcast group");
 
 	do {
+		bool server_side = false;
+
 		FD_ZERO(&rfds);
 		FD_SET(fd, &rfds);
 		res_len = NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
@@ -187,18 +190,22 @@ static int capture_events(int fd, int event_group)
 				else if (attrs->rta_type == MPTCP_ATTR_ERROR)
 					fprintf(stderr, ",error:%u", *(__u8 *)RTA_DATA(attrs));
 				else if (attrs->rta_type == MPTCP_ATTR_SERVER_SIDE)
-					fprintf(stderr, ",server_side:%u", *(__u8 *)RTA_DATA(attrs));
+					server_side = !!*(__u8 *)RTA_DATA(attrs);
 				else if (attrs->rta_type == MPTCP_ATTR_FLAGS) {
 					__u16 flags = *(__u16 *)RTA_DATA(attrs);
 
 					/* only print when present, easier */
 					if (flags & MPTCP_PM_EV_FLAG_DENY_JOIN_ID0)
 						fprintf(stderr, ",deny_join_id0:1");
+					if (flags & MPTCP_PM_EV_FLAG_SERVER_SIDE)
+						server_side = true;
 				}
 
 				attrs = RTA_NEXT(attrs, msg_len);
 			}
 		}
+		if (server_side)
+			fprintf(stderr, ",server_side:1");
 		fprintf(stderr, "\n");
 	} while (1);
 
diff --git a/tools/testing/selftests/net/mptcp/userspace_pm.sh b/tools/testing/selftests/net/mptcp/userspace_pm.sh
index 3d45991f24ed..87323942cb8a 100755
--- a/tools/testing/selftests/net/mptcp/userspace_pm.sh
+++ b/tools/testing/selftests/net/mptcp/userspace_pm.sh
@@ -241,7 +241,7 @@ make_connection()
 
 	print_test "Established IP${is_v6} MPTCP Connection ns2 => ns1"
 	if [ "${client_token}" != "" ] && [ "${server_token}" != "" ] &&
-	   [ "${client_serverside}" = 0 ] && [ "${server_serverside}" = 1 ] &&
+	   [ "${client_serverside:-0}" = 0 ] && [ "${server_serverside:-0}" = 1 ] &&
 	   [ "${client_nojoin:-0}" = 0 ] && [ "${server_nojoin:-0}" = 1 ]
 	then
 		test_pass