[PATCH iproute2-next 3/9] libnetlink: Add helper to add a group via setsockopt

[David Ahern <dsahern@kernel.org>]

From: David Ahern <dsahern@gmail.com>

groups > 31 have to be joined using the setsockopt. Since the nexthop
group is 32, add a helper to allow 'ip monitor' to listen for nexthop
messages.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/libnetlink.h | 3 ++-
 lib/libnetlink.c     | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/libnetlink.h b/include/libnetlink.h
index 503b3ec11bb6..599b2c592f68 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -45,7 +45,8 @@ int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
 int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
 			     int protocol)
 	__attribute__((warn_unused_result));
-
+int rtnl_add_nl_group(struct rtnl_handle *rth, unsigned int group)
+	__attribute__((warn_unused_result));
 void rtnl_close(struct rtnl_handle *rth);
 void rtnl_set_strict_dump(struct rtnl_handle *rth);
 
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 6ae51a9dba14..eb85bbdf01ee 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -173,6 +173,12 @@ void rtnl_set_strict_dump(struct rtnl_handle *rth)
 	rth->flags |= RTNL_HANDLE_F_STRICT_CHK;
 }
 
+int rtnl_add_nl_group(struct rtnl_handle *rth, unsigned int group)
+{
+	return setsockopt(rth->fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP,
+			  &group, sizeof(group));
+}
+
 void rtnl_close(struct rtnl_handle *rth)
 {
 	if (rth->fd >= 0) {
-- 
2.11.0