gprs: fix has_valid_nsvc(): permit local udp port 0

NSVC local port 0 is actually a valid value, which tells the PCU to
pick a random port for bind()ing.  It was supported before 315af2f9e,
but now osmo-bsc would simply ignore NSVCs with 'local udp port 0'
and leave the respective MOs unconfigured in the BTS.

Change-Id: I0afd83e77f3daeeb082e7db911610428b5bc587c
Fixes: 315af2f9e "bts: ipa/osmo-bts/sysmobts: MO: add support for the second NSVC"
Related: OS#5979
---
M src/osmo-bsc/nm_gprs_nsvc_fsm.c
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/osmo-bsc/nm_gprs_nsvc_fsm.c b/src/osmo-bsc/nm_gprs_nsvc_fsm.c
index 5186082..906ba2a 100644
--- a/src/osmo-bsc/nm_gprs_nsvc_fsm.c
+++ b/src/osmo-bsc/nm_gprs_nsvc_fsm.c
@@ -90,12 +90,17 @@
 	}
 }
 
-static bool has_valid_nsvc(struct gsm_gprs_nsvc *nsvc)
+static bool has_valid_nsvc(const struct gsm_gprs_nsvc *nsvc)
 {
+	/* remote address must be valid */
+	if (osmo_sockaddr_is_any(&nsvc->remote))
+		return false;
+	/* remote port must be valid */
 	switch (nsvc->remote.u.sa.sa_family) {
 	case AF_INET:
+		return nsvc->remote.u.sin.sin_port != 0;
 	case AF_INET6:
-		return (nsvc->local_port > 0 && !osmo_sockaddr_is_any(&nsvc->remote));
+		return nsvc->remote.u.sin6.sin6_port != 0;
 	default:
 		return false;
 	}

