[PATCH iproute2-next v2] mptcp: add support for implicit flag

[Andrea Claudi <aclaudi@redhat.com>]

Kernel supports implicit flag since commit d045b9eb95a9 ("mptcp:
introduce implicit endpoints"), included in v5.18.

Let's add support for displaying it to iproute2.

Before this change:
$ ip mptcp endpoint show
10.0.2.2 id 1 rawflags 10

After this change:
$ ip mptcp endpoint show
10.0.2.2 id 1 implicit

Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
---
v2: added implicit to ip-mptcp man page, as suggested by David Ahern

 ip/ipmptcp.c        | 1 +
 man/man8/ip-mptcp.8 | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/ip/ipmptcp.c b/ip/ipmptcp.c
index beba7a41..9847f95b 100644
--- a/ip/ipmptcp.c
+++ b/ip/ipmptcp.c
@@ -58,6 +58,7 @@ static const struct {
 	{ "subflow",		MPTCP_PM_ADDR_FLAG_SUBFLOW },
 	{ "backup",		MPTCP_PM_ADDR_FLAG_BACKUP },
 	{ "fullmesh",		MPTCP_PM_ADDR_FLAG_FULLMESH },
+	{ "implicit",		MPTCP_PM_ADDR_FLAG_IMPLICIT },
 	{ "nobackup",		MPTCP_PM_ADDR_FLAG_NONE },
 	{ "nofullmesh",		MPTCP_PM_ADDR_FLAG_NONE }
 };
diff --git a/man/man8/ip-mptcp.8 b/man/man8/ip-mptcp.8
index 72762f49..b427065c 100644
--- a/man/man8/ip-mptcp.8
+++ b/man/man8/ip-mptcp.8
@@ -176,6 +176,15 @@ endpoint. When the peer does announce addresses, each received ADD_ADDR
 sub-option will trigger creation of an additional subflow to generate a
 full mesh topology.
 
+.TP
+.BR implicit
+In some scenarios, an MPTCP
+.BR subflow
+can use a local address mapped by a implicit endpoint created by the
+in-kernel path manager. Once set, the implicit flag cannot be removed, but
+other flags can be added to the endpoint. Implicit endpoints cannot be
+created from user-space.
+
 .sp
 .PP
 The
-- 
2.40.1