[PATCH v2 2/2] tools: ynl: add unicast notification receive support

[Minxi Hou <houminxi@gmail.com>]

Add ntf_listen() method to YnlFamily for binding the netlink
socket without joining a multicast group. This enables receiving
unicast notifications through the existing poll_ntf/check_ntf
path.

The OVS packet family sends MISS and ACTION upcalls via
genlmsg_unicast() to a per-vport PID rather than through a
multicast group. The existing ntf_subscribe() couples bind()
with setsockopt(ADD_MEMBERSHIP), which does not fit the unicast
case. ntf_listen() provides the bind-only alternative.

Signed-off-by: Minxi Hou <houminxi@gmail.com>
---
 tools/net/ynl/pyynl/lib/ynl.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/net/ynl/pyynl/lib/ynl.py b/tools/net/ynl/pyynl/lib/ynl.py
index f63c6f828735..04743a79a7a3 100644
--- a/tools/net/ynl/pyynl/lib/ynl.py
+++ b/tools/net/ynl/pyynl/lib/ynl.py
@@ -680,6 +680,7 @@ class YnlFamily(SpecFamily):
     Notification API:
 
       ynl.ntf_subscribe(mcast_name)      -- join a multicast group
+      ynl.ntf_listen()                   -- bind socket for unicast notifications
       ynl.check_ntf()                    -- drain pending notifications
       ynl.poll_ntf(duration=None)        -- yield notifications
 
@@ -748,6 +749,10 @@ class YnlFamily(SpecFamily):
         self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_ADD_MEMBERSHIP,
                              mcast_id)
 
+    def ntf_listen(self):
+        """Bind socket for receiving unicast notifications."""
+        self.sock.bind((0, 0))
+
     def set_recv_dbg(self, enabled):
         self._recv_dbg = enabled
 
-- 
2.54.0