add mDNS lookup method to libosmo-mslookup
Add the first actually useful lookup method to the mslookup library: multicast
DNS.
The server side is added in a subsequent commit, when the mslookup server is
implemented for the osmo-hlr program.
Use custom DNS encoding instead of libc-ares (which we use in OsmoSGSN
already), because libc-ares is only a DNS client implementation and we will
need both client and server.
Related: OS#4237
Patch-by: osmith, nhofmeyr
Change-Id: I03a0ffa1d4dc1b24ac78a5ad0975bca90a49c728
diff --git a/include/osmocom/mslookup/mdns_sock.h b/include/osmocom/mslookup/mdns_sock.h
new file mode 100644
index 0000000..615e971
--- /dev/null
+++ b/include/osmocom/mslookup/mdns_sock.h
@@ -0,0 +1,33 @@
+/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include <netdb.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/select.h>
+
+struct osmo_mdns_sock {
+ struct osmo_fd osmo_fd;
+ struct addrinfo *ai;
+};
+
+struct osmo_mdns_sock *osmo_mdns_sock_init(void *ctx, const char *ip, unsigned int port,
+ int (*cb)(struct osmo_fd *fd, unsigned int what),
+ void *data, unsigned int priv_nr);
+int osmo_mdns_sock_send(const struct osmo_mdns_sock *mdns_sock, struct msgb *msg);
+void osmo_mdns_sock_cleanup(struct osmo_mdns_sock *mdns_sock);