lightningd: add option dev-strict-forwarding

Changelog-Add: add option dev-strict-forwarding

Signed-off-by: Lagrang3 <[email protected]>

Author: Lagrang3

lightningd/lightningd.c

@@ -151,6 +151,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	ld->dev_hsmd_no_preapprove_check = false;
 	ld->dev_hsmd_fail_preapprove = false;
 	ld->dev_handshake_no_reply = false;
+	ld->dev_strict_forwarding = false;
 
 	/*~ We try to ensure enough fds for twice the number of channels
 	 * we start with.  We have a developer option to change that factor

lightningd/lightningd.h

@@ -362,6 +362,10 @@ struct lightningd {
 	/* Tell connectd not to talk after handshake */
 	bool dev_handshake_no_reply;
 
+	/* Remove the freedom to choose select between parallel channels to
+	 * forward a payment. */
+	bool dev_strict_forwarding;
+
 	/* tor support */
 	struct wireaddr *proxyaddr;
 	bool always_use_proxy;

lightningd/options.c

@@ -956,6 +956,10 @@ static void dev_register_opts(struct lightningd *ld)
 		     opt_set_bool,
 		     &ld->dev_handshake_no_reply,
 		     "Don't send or read init message after connection");
+	clnopt_noarg("--dev-strict-forwarding", OPT_DEV,
+		     opt_set_bool,
+		     &ld->dev_strict_forwarding,
+		     "Forward HTLCs along the channel specified");
 	clnopt_noarg("--dev-throttle-gossip", OPT_DEV,
 		     opt_set_bool,
 		     &ld->dev_throttle_gossip,

lightningd/peer_htlcs.c

@@ -668,16 +668,6 @@ static struct channel *best_channel(struct lightningd *ld,
 				    struct amount_msat amt_to_forward,
 				    struct channel *hint)
 {
-	/* Prefer using hint if it can forward the request. */
-	if (hint && channel_state_can_add_htlc(hint->state)) {
-		struct amount_msat spendable;
-		spendable = channel_amount_spendable(hint);
-		if (amount_msat_greater_eq(
-			amt_to_forward,
-			hint->channel_info.their_config.htlc_minimum) &&
-		    amount_msat_less_eq(amt_to_forward, spendable))
-			return hint;
-	}
 	struct amount_msat best_spendable = AMOUNT_MSAT(0);
 	struct channel *channel, *best = hint;
 
@@ -1222,7 +1212,11 @@ static struct channel_id *calc_forwarding_channel(struct lightningd *ld,
 		c = NULL;
 	}
 
-	best = best_channel(ld, peer, p->amt_to_forward, c);
+	if (!ld->dev_strict_forwarding)
+		best = best_channel(ld, peer, p->amt_to_forward, c);
+	else
+		best = c;
+
 	if (!c) {
 		if (!best)
 			return NULL;

tests/test_pay.py

@@ -6065,10 +6065,16 @@ def start_channels(connections):
 
 def test_parallel_channels_reserve(node_factory):
     """Tests wether we are able to pay through parallel channels concurrently."""
+
     def direction(node1, node2):
         return 0 if node1.info["id"] < node2.info["id"] else 1
 
-    opts = {"disable-mpp": None, "fee-base": 0, "fee-per-satoshi": 0, "cltv-delta": 6}
+    opts = {
+        "fee-base": 0,
+        "fee-per-satoshi": 0,
+        "cltv-delta": 6,
+        "dev-strict-forwarding": None,
+    }
     l1, l2, l3 = node_factory.get_nodes(3, opts=opts)
 
     chan_ids = start_channels(