SGSN VTY: make missing GSUP server address+port fatal

On 'auth-policy remote', the SGSN requires GSUP server address and port. If it
was missing, the SGSN would print a VTY warning and run anyway. Make this error
more fatal: print an error (flattened a bit) to stderr and abort the program.

Move validation of the GSUP server data presence out of the VTY command itself
and into the config reading function. This way the GSUP server config can be
given anywhere, including below the auth-policy config (was required above).

Don't care about setting the auth-policy to remote with a telnet VTY, because
in that case the GSUP client won't be started anyway.

Change-Id: I4d8db910c32abd8579d3c9b9f0b2cb3a9a6dfe4c
diff --git a/openbsc/src/gprs/sgsn_vty.c b/openbsc/src/gprs/sgsn_vty.c
index a730635..6c8b640 100644
--- a/openbsc/src/gprs/sgsn_vty.c
+++ b/openbsc/src/gprs/sgsn_vty.c
@@ -638,17 +638,6 @@
 {
 	int val = get_string_value(sgsn_auth_pol_strs, argv[0]);
 	OSMO_ASSERT(val >= SGSN_AUTH_POLICY_OPEN && val <= SGSN_AUTH_POLICY_REMOTE);
-	if (val == SGSN_AUTH_POLICY_REMOTE) {
-		const char *err = "%% auth-policy remote requires";
-		if (!g_cfg->gsup_server_addr.sin_addr.s_addr) {
-			vty_out(vty, "%s 'gsup remote-ip'%s", err, VTY_NEWLINE);
-			return CMD_WARNING;
-		}
-		if (!g_cfg->gsup_server_port) {
-			vty_out(vty, "%s 'gsup remote-port'%s", err, VTY_NEWLINE);
-			return CMD_WARNING;
-		}
-	}
 	g_cfg->auth_policy = val;
 	g_cfg->require_authentication = (val == SGSN_AUTH_POLICY_REMOTE);
 	g_cfg->require_update_location = (val == SGSN_AUTH_POLICY_REMOTE);
@@ -1311,5 +1300,14 @@
 		return rc;
 	}
 
+	if (g_cfg->auth_policy == SGSN_AUTH_POLICY_REMOTE
+	    && !(g_cfg->gsup_server_addr.sin_addr.s_addr
+		 && g_cfg->gsup_server_port)) {
+		fprintf(stderr, "Configuration error:"
+			" 'auth-policy remote' requires both"
+			" 'gsup remote-ip' and 'gsup remote-port'\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }