Let invoice command specify exact channel(s) to share.

common/jsonrpc_errors.h

@@ -45,5 +45,6 @@
 /* Errors from `invoice` command */
 #define INVOICE_LABEL_ALREADY_EXISTS	900
 #define INVOICE_PREIMAGE_ALREADY_EXISTS	901
+#define INVOICE_HINTS_GAVE_NO_ROUTES	902
 
 #endif /* LIGHTNING_COMMON_JSONRPC_ERRORS_H */

doc/lightning-invoice.7.md

@@ -54,7 +54,9 @@ should not be used unless explicitly needed.
 If specified, *exposeprivatechannels* overrides the default route hint
 logic, which will use unpublished channels only if there are no
 published channels. If *true* unpublished channels are always considered
-as a route hint candidate; if *false*, never.
+as a route hint candidate; if *false*, never.  If it is a short channel id
+(e.g. *1x1x3*) or array of short channel ids, only those specific channels
+will be considered candidates, even if they are public.
 
 The route hint is selected from the set of incoming channels of which:
 peer’s balance minus their reserves is at least *msatoshi*, state is
@@ -79,13 +81,14 @@ The following error codes may occur:
 - -1: Catchall nonspecific error.
 - 900: An invoice with the given *label* already exists.
 - 901: An invoice with the given *preimage* already exists.
+- 902: None of the specified *exposeprivatechannels* were usable.
 
 One of the following warnings may occur (on success):
 - *warning\_offline* if no channel with a currently connected peer has
     the incoming capacity to pay this invoice
-- *warning\_capacity* if there is no channel that has both sufficient
-    incoming capacity and has a peer that is publicly connected (i.e.
-    not a dead end)
+- *warning\_capacity* if there is no channel that has sufficient
+    incoming capacity
+- *warning\_deadends* if there is no channel that is not a dead-end
 
 AUTHOR
 ------

gossipd/gossip_wire.csv

@@ -128,12 +128,15 @@ msgdata,gossip_dev_compact_store_reply,success,bool,
 
 # master -> gossipd: get route_info for our incoming channels
 msgtype,gossip_get_incoming_channels,3025
-msgdata,gossip_get_incoming_channels,private_too,?bool,
 
 # gossipd -> master: here they are.
 msgtype,gossip_get_incoming_channels_reply,3125
-msgdata,gossip_get_incoming_channels_reply,num,u16,
-msgdata,gossip_get_incoming_channels_reply,route_info,route_info,num
+msgdata,gossip_get_incoming_channels_reply,num_public,u16,
+msgdata,gossip_get_incoming_channels_reply,public_route_info,route_info,num_public
+msgdata,gossip_get_incoming_channels_reply,public_deadends,bool,num_public
+msgdata,gossip_get_incoming_channels_reply,num_private,u16,
+msgdata,gossip_get_incoming_channels_reply,private_route_info,route_info,num_private
+msgdata,gossip_get_incoming_channels_reply,private_deadends,bool,num_private
 
 # master -> gossipd: blockheight increased.
 msgtype,gossip_new_blockheight,3026

gossipd/gossipd.c

@@ -1188,18 +1188,6 @@ static bool node_has_public_channels(const struct node *peer,
 	return false;
 }
 
-/*~ The `exposeprivate` flag is a trinary: NULL == dynamic, otherwise
- * value decides.  Thus, we provide two wrappers for clarity: */
-static bool never_expose(bool *exposeprivate)
-{
-	return exposeprivate && !*exposeprivate;
-}
-
-static bool always_expose(bool *exposeprivate)
-{
-	return exposeprivate && *exposeprivate;
-}
-
 /*~ For routeboost, we offer payers a hint of what incoming channels might
  * have capacity for their payment.  To do this, lightningd asks for the
  * information about all channels to this node; but gossipd doesn't know about
@@ -1211,14 +1199,12 @@ static struct io_plan *get_incoming_channels(struct io_conn *conn,
 	struct node *node;
 	struct route_info *public = tal_arr(tmpctx, struct route_info, 0);
 	struct route_info *private = tal_arr(tmpctx, struct route_info, 0);
-	bool has_public;
-	bool *exposeprivate;
+	bool *priv_deadends = tal_arr(tmpctx, bool, 0);
+	bool *pub_deadends = tal_arr(tmpctx, bool, 0);
 
-	if (!fromwire_gossip_get_incoming_channels(tmpctx, msg, &exposeprivate))
+	if (!fromwire_gossip_get_incoming_channels(msg))
 		master_badmsg(WIRE_GOSSIP_GET_INCOMING_CHANNELS, msg);
 
-	has_public = always_expose(exposeprivate);
-
 	node = get_node(daemon->rstate, &daemon->rstate->local_id);
 	if (node) {
 		struct chan_map_iter i;
@@ -1227,6 +1213,7 @@ static struct io_plan *get_incoming_channels(struct io_conn *conn,
 		for (c = first_chan(node, &i); c; c = next_chan(node, &i)) {
 			const struct half_chan *hc;
 			struct route_info ri;
+			bool deadend;
 
 			hc = &c->half[half_chan_to(node, c)];
 
@@ -1239,25 +1226,21 @@ static struct io_plan *get_incoming_channels(struct io_conn *conn,
 			ri.fee_proportional_millionths = hc->proportional_fee;
 			ri.cltv_expiry_delta = hc->delay;
 
-			has_public |= is_chan_public(c);
-
-			/* If peer doesn't have other public channels,
-			 * no point giving route */
-			if (!node_has_public_channels(other_node(node, c), c))
-				continue;
-
-			if (always_expose(exposeprivate) || is_chan_public(c))
+			deadend = !node_has_public_channels(other_node(node, c),
+							    c);
+			if (is_chan_public(c)) {
 				tal_arr_expand(&public, ri);
-			else
+				tal_arr_expand(&pub_deadends, deadend);
+			} else {
 				tal_arr_expand(&private, ri);
+				tal_arr_expand(&priv_deadends, deadend);
+			}
 		}
 	}
 
-	/* If no public channels (even deadend ones!), share private ones. */
-	if (!has_public && !never_expose(exposeprivate))
-		msg = towire_gossip_get_incoming_channels_reply(NULL, private);
-	else
-		msg = towire_gossip_get_incoming_channels_reply(NULL, public);
+	msg = towire_gossip_get_incoming_channels_reply(NULL,
+							public, pub_deadends,
+							private, priv_deadends);
 	daemon_conn_send(daemon->master, take(msg));
 
 	return daemon_conn_read_next(conn, daemon->master);