Clean up network options.

It's become clear that our network options are insufficient, with the coming
addition of Tor and unix domain support.

Currently:

1. We always bind to local IPv4 and IPv6 sockets, unless --port=0, --offline,
   or any address is specified explicitly.  If they're routable, we announce.
2. --addr is used to announce, but not to control binding.

After this change:

1. --port is deprecated.
2. --addr controls what we bind to and announce.
3. --bind-addr/--announce-addr can be used to control one and not the other.
4. Unless --autolisten=0, we add local IPv4 & IPv6 port 9735 (and announce if they are routable).
5. --offline still overrides listening (though announcing is still the same).

This means we can bind to as many ports/interfaces as we want, and for
special effects we can announce different things (eg. we're sitting
behind a port forward or a proxy).

What remains to implement is semi-automatic binding: we should be able
to say '--addr=0.0.0.0:9999' and have the address resolve at bind
time, or even '--addr=0.0.0.0:0' and have the port autoresolve too
(you could determine what it was from 'lightning-cli getinfo'.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/wireaddr.h

@@ -37,10 +37,22 @@ struct wireaddr {
 	u16 port;
 };
 
+/* We use wireaddr to tell gossipd both what to listen on, and what to
+ * announce */
+enum addr_listen_announce {
+	ADDR_LISTEN = (1 << 0),
+	ADDR_ANNOUNCE = (1 << 1),
+	ADDR_LISTEN_AND_ANNOUNCE = ADDR_LISTEN|ADDR_ANNOUNCE
+};
+
 /* Inserts a single ADDR_TYPE_PADDING if addr is NULL */
 void towire_wireaddr(u8 **pptr, const struct wireaddr *addr);
 bool fromwire_wireaddr(const u8 **cursor, size_t *max, struct wireaddr *addr);
 
+enum addr_listen_announce fromwire_addr_listen_announce(const u8 **cursor,
+							size_t *max);
+void towire_addr_listen_announce(u8 **pptr, enum addr_listen_announce ala);
+
 bool parse_wireaddr(const char *arg, struct wireaddr *addr, u16 port, const char **err_msg);
 
 char *fmt_wireaddr(const tal_t *ctx, const struct wireaddr *a);