chore: err_reason for initial_channel_tx initial_commit_tx

common/initial_channel.c

@@ -73,7 +73,8 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
 				      const u8 **wscript,
 				      const struct channel *channel,
 				      const struct pubkey *per_commitment_point,
-				      enum side side)
+				      enum side side,
+				      char** err_reason)
 {
 	struct keyset keyset;
 
@@ -83,8 +84,10 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
 	if (!derive_keyset(per_commitment_point,
 			   &channel->basepoints[side],
 			   &channel->basepoints[!side],
-			   &keyset))
+			   &keyset)){
+		*err_reason = "Cannot derive keyset";
 		return NULL;
+	}
 
 	*wscript = bitcoin_redeem_2of2(ctx,
 				       &channel->funding_pubkey[side],
@@ -103,7 +106,8 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
 				 channel->view[side].owed[!side],
 				 channel->config[!side].channel_reserve,
 				 0 ^ channel->commitment_number_obscurer,
-				 side);
+				 side,
+				 err_reason);
 }
 
 static char *fmt_channel_view(const tal_t *ctx, const struct channel_view *view)

common/initial_channel.h

@@ -111,6 +111,7 @@ struct channel *new_initial_channel(const tal_t *ctx,
  * @channel: The channel to evaluate
  * @per_commitment_point: Per-commitment point to determine keys
  * @side: which side to get the commitment transaction for
+ * @err_reason: When NULL is returned, this will point to a human readable reason.
  *
  * Returns the unsigned initial commitment transaction for @side, or NULL
  * if the channel size was insufficient to cover fees or reserves.
@@ -119,6 +120,7 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
 				      const u8 **wscript,
 				      const struct channel *channel,
 				      const struct pubkey *per_commitment_point,
-				      enum side side);
+				      enum side side,
+				      char** err_reason);
 
 #endif /* LIGHTNING_COMMON_INITIAL_CHANNEL_H */

common/initial_commit_tx.c

@@ -72,7 +72,8 @@ struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
 				     struct amount_msat other_pay,
 				     struct amount_sat self_reserve,
 				     u64 obscured_commitment_number,
-				     enum side side)
+				     enum side side,
+				     char** err_reason)
 {
 	struct amount_sat base_fee;
 	struct bitcoin_tx *tx;
@@ -112,6 +113,7 @@ struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
 		 *   - it considers `feerate_per_kw` too small for timely
 		 *     processing or unreasonably large.
 		 */
+		*err_reason = "Funder cannot afford fee on initial commitment transaction";
 		status_unusual("Funder cannot afford fee"
 			       " on initial commitment transaction");
 		return NULL;
@@ -127,6 +129,8 @@ struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
 	 */
 	if (!amount_msat_greater_sat(self_pay, self_reserve)
 	    && !amount_msat_greater_sat(other_pay, self_reserve)) {
+		*err_reason = "Neither self amount nor other amount exceed reserve on "
+				   "initial commitment transaction";
 		status_unusual("Neither self amount %s"
 			       " nor other amount %s"
 			       " exceed reserve %s"

common/initial_commit_tx.h

@@ -61,6 +61,7 @@ static inline struct amount_sat commit_tx_base_fee(u32 feerate_per_kw,
  * @self_reserve: reserve the other side insisted we have
  * @obscured_commitment_number: number to encode in commitment transaction
  * @side: side to generate commitment transaction for.
+ * @err_reason: When NULL is returned, this will point to a human readable reason.
  *
  * We need to be able to generate the remote side's tx to create signatures,
  * but the BOLT is expressed in terms of generating our local commitment
@@ -79,7 +80,8 @@ struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
 				     struct amount_msat other_pay,
 				     struct amount_sat self_reserve,
 				     u64 obscured_commitment_number,
-				     enum side side);
+				     enum side side,
+				     char** err_reason);
 
 /* try_subtract_fee - take away this fee from the funder (and return true), or all if insufficient (and return false). */
 bool try_subtract_fee(enum side funder, enum side side,

openingd/openingd.c

@@ -445,6 +445,7 @@ static u8 *funder_channel(struct state *state,
 	struct bitcoin_tx *funding;
 	const u8 *wscript;
 	struct amount_msat local_msat;
+	char* err_reason;
 
 	/*~ For symmetry, we calculate our own reserve even though lightningd
 	 * could do it for the we-are-funding case. */
@@ -668,12 +669,12 @@ static u8 *funder_channel(struct state *state,
 	/* This gives us their first commitment transaction. */
 	tx = initial_channel_tx(state, &wscript, state->channel,
 				&state->first_per_commitment_point[REMOTE],
-				REMOTE);
+				REMOTE, &err_reason);
 	if (!tx) {
 		/* This should not happen: we should never create channels we
 		 * can't afford the fees for after reserve. */
 		negotiation_failed(state, true,
-				   "Could not meet their fees and reserve");
+				   "Could not meet their fees and reserve: %s", err_reason);
 		goto fail_2;
 	}
 
@@ -775,10 +776,10 @@ static u8 *funder_channel(struct state *state,
 	 * signature they sent against that. */
 	tx = initial_channel_tx(state, &wscript, state->channel,
 				&state->first_per_commitment_point[LOCAL],
-				LOCAL);
+				LOCAL, &err_reason);
 	if (!tx) {
 		negotiation_failed(state, true,
-				   "Could not meet our fees and reserve");
+				   "Could not meet our fees and reserve: %s", err_reason);
 		goto fail_2;
 	}
 
@@ -844,6 +845,7 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 	u8 *msg;
 	const u8 *wscript;
 	u8 channel_flags;
+	char* err_reason;
 
 	/* BOLT #2:
 	 *
@@ -1070,11 +1072,11 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 	 */
 	local_commit = initial_channel_tx(state, &wscript, state->channel,
 					  &state->first_per_commitment_point[LOCAL],
-					  LOCAL);
+					  LOCAL, &err_reason);
 	/* This shouldn't happen either, AFAICT. */
 	if (!local_commit) {
 		negotiation_failed(state, false,
-				   "Could not meet our fees and reserve");
+				   "Could not meet our fees and reserve: %s", err_reason);
 		return NULL;
 	}
 
@@ -1130,10 +1132,10 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 	 */
 	remote_commit = initial_channel_tx(state, &wscript, state->channel,
 					   &state->first_per_commitment_point[REMOTE],
-					   REMOTE);
+					   REMOTE, &err_reason);
 	if (!remote_commit) {
 		negotiation_failed(state, false,
-				   "Could not meet their fees and reserve");
+				   "Could not meet their fees and reserve: %s", err_reason);
 		return NULL;
 	}