channeld: tell lightningd about local anchor for each commitment tx.

It's going to want to remember these, in case it encounters peers'
commitment tx and needs to boost it with CPFP on the anchor.

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

channeld/channeld.c

@@ -1501,14 +1501,17 @@ static bool want_blockheight_update(const struct peer *peer, u32 *height)
 	return true;
 }
 
-static u8 *send_commit_part(struct peer *peer,
+/* Returns commitment_signed msg, sets @local_anchor */
-			     const struct bitcoin_outpoint *funding,
+static u8 *send_commit_part(const tal_t *ctx,
-			     struct amount_sat funding_sats,
+			    struct peer *peer,
-			     const struct htlc **changed_htlcs,
+			    const struct bitcoin_outpoint *funding,
-			     bool notify_master,
+			    struct amount_sat funding_sats,
-			     s64 splice_amnt,
+			    const struct htlc **changed_htlcs,
-			     s64 remote_splice_amnt,
+			    bool notify_master,
-			     u64 remote_index)
+			    s64 splice_amnt,
+			    s64 remote_splice_amnt,
+			    u64 remote_index,
+			    struct local_anchor_info **anchor)
 {
 	u8 *msg;
 	struct bitcoin_signature commit_sig, *htlc_sigs;
@@ -1517,6 +1520,7 @@ static u8 *send_commit_part(struct peer *peer,
 	const struct htlc **htlc_map;
 	struct wally_tx_output *direct_outputs[NUM_SIDES];
 	struct penalty_base *pbase;
+	int local_anchor_outnum;
 	struct tlv_commitment_signed_tlvs *cs_tlv
 		= tlv_commitment_signed_tlvs_new(tmpctx);
 
@@ -1537,7 +1541,7 @@ static u8 *send_commit_part(struct peer *peer,
 			  direct_outputs, &funding_wscript,
 			  peer->channel, &peer->remote_per_commit,
 			  remote_index, REMOTE,
-			  splice_amnt, remote_splice_amnt);
+			  splice_amnt, remote_splice_amnt, &local_anchor_outnum);
 	htlc_sigs =
 	    calc_commitsigs(tmpctx, peer, txs, funding_wscript, htlc_map,
 			    remote_index, &commit_sig);
@@ -1552,6 +1556,16 @@ static u8 *send_commit_part(struct peer *peer,
 	}  else
 		pbase = NULL;
 
+	if (local_anchor_outnum == -1) {
+		*anchor = NULL;
+	} else {
+		*anchor = tal(ctx, struct local_anchor_info);
+		bitcoin_txid(txs[0], &(*anchor)->anchor_point.txid);
+		(*anchor)->anchor_point.n = local_anchor_outnum;
+		(*anchor)->commitment_weight = bitcoin_tx_weight(txs[0]);
+		(*anchor)->commitment_fee = bitcoin_tx_compute_fee(txs[0]);
+	}
+
 	if (peer->dev_disable_commit) {
 		(*peer->dev_disable_commit)--;
 		if (*peer->dev_disable_commit == 0)
@@ -1574,7 +1588,7 @@ static u8 *send_commit_part(struct peer *peer,
 			     tal_count(htlc_sigs));
 	}
 
-	msg = towire_commitment_signed(NULL, &peer->channel_id,
+	msg = towire_commitment_signed(ctx, &peer->channel_id,
 				       &commit_sig.s,
 				       raw_sigs(tmpctx, htlc_sigs),
 				       cs_tlv);
@@ -1594,6 +1608,7 @@ static void send_commit(struct peer *peer)
 	u32 feerate_target;
 	u8 **msgs = tal_arr(tmpctx, u8*, 1);
 	u8 *msg;
+	struct local_anchor_info *local_anchor, *anchors_info;
 
 	if (peer->dev_disable_commit && !*peer->dev_disable_commit) {
 		peer->commit_timer = NULL;
@@ -1705,9 +1720,13 @@ static void send_commit(struct peer *peer)
 		return;
 	}
 
-	msgs[0] = send_commit_part(peer, &peer->channel->funding,
+	anchors_info = tal_arr(tmpctx, struct local_anchor_info, 0);
+	msgs[0] = send_commit_part(msgs, peer, &peer->channel->funding,
 				   peer->channel->funding_sats, changed_htlcs,
-				   true, 0, 0, peer->next_index[REMOTE]);
+				   true, 0, 0, peer->next_index[REMOTE],
+				   &local_anchor);
+	if (local_anchor)
+		tal_arr_expand(&anchors_info, *local_anchor);
 
 	/* Loop over current inflights
 	 * BOLT-0d8b701614b09c6ee4172b04da2203e73deec7e2 #2:
@@ -1725,15 +1744,23 @@ static void send_commit(struct peer *peer)
 					- peer->splice_state->inflights[i]->splice_amnt;
 
 		tal_arr_expand(&msgs,
-			       send_commit_part(peer,
+			       send_commit_part(msgs, peer,
 						&peer->splice_state->inflights[i]->outpoint,
 						peer->splice_state->inflights[i]->amnt,
 						changed_htlcs, false,
 						peer->splice_state->inflights[i]->splice_amnt,
 						remote_splice_amnt,
-						peer->next_index[REMOTE]));
+						peer->next_index[REMOTE],
+						&local_anchor));
+		if (local_anchor)
+			tal_arr_expand(&anchors_info, *local_anchor);
 	}
 
+	/* Now, tell master about the anchor on each of their commitments */
+	msg = towire_channeld_local_anchor_info(NULL, peer->next_index[REMOTE],
+						anchors_info);
+	wire_sync_write(MASTER_FD, take(msg));
+
 	peer->next_index[REMOTE]++;
 
 	for(u32 i = 0; i < tal_count(msgs); i++)
@@ -1967,6 +1994,7 @@ static struct commitsig *handle_peer_commit_sig(struct peer *peer,
 	struct amount_sat funding_sats;
 	struct channel_id active_id;
 	const struct commitsig **commitsigs;
+	int remote_anchor_outnum;
 
 	status_debug("handle_peer_commit_sig(splice: %d, remote_splice: %d)",
 		     (int)splice_amnt, (int)remote_splice_amnt);
@@ -2051,7 +2079,7 @@ static struct commitsig *handle_peer_commit_sig(struct peer *peer,
 			  NULL, &funding_wscript, peer->channel,
 			  &peer->next_local_per_commit,
 			  peer->next_index[LOCAL], LOCAL, splice_amnt,
-			  remote_splice_amnt);
+			  remote_splice_amnt, &remote_anchor_outnum);
 
 	/* Set the commit_sig on the commitment tx psbt */
 	if (!psbt_input_set_signature(txs[0]->psbt, 0,
@@ -4382,6 +4410,7 @@ static void resend_commitment(struct peer *peer, struct changed_htlc *last)
 	size_t i;
 	u8 *msg;
 	u8 **msgs = tal_arr(tmpctx, u8*, 1);
+	struct local_anchor_info *local_anchor;
 
 	status_debug("Retransmitting commitment, feerate LOCAL=%u REMOTE=%u,"
 		     " blockheight LOCAL=%u REMOTE=%u",
@@ -4472,9 +4501,10 @@ static void resend_commitment(struct peer *peer, struct changed_htlc *last)
 		}
 	}
 
-	msgs[0] = send_commit_part(peer, &peer->channel->funding,
+	msgs[0] = send_commit_part(msgs, peer, &peer->channel->funding,
 				   peer->channel->funding_sats, NULL,
-				   false, 0, 0, peer->next_index[REMOTE] - 1);
+				   false, 0, 0, peer->next_index[REMOTE] - 1,
+				   &local_anchor);
 
 	/* Loop over current inflights
 	 * BOLT-0d8b701614b09c6ee4172b04da2203e73deec7e2 #2:
@@ -4492,13 +4522,14 @@ static void resend_commitment(struct peer *peer, struct changed_htlc *last)
 					- peer->splice_state->inflights[i]->splice_amnt;
 
 		tal_arr_expand(&msgs,
-			       send_commit_part(peer,
+			       send_commit_part(msgs, peer,
 						&peer->splice_state->inflights[i]->outpoint,
 						peer->splice_state->inflights[i]->amnt,
 						NULL, false,
 						peer->splice_state->inflights[i]->splice_amnt,
 						remote_splice_amnt,
-						peer->next_index[REMOTE] - 1));
+						peer->next_index[REMOTE] - 1,
+						&local_anchor));
 	}
 
 	for(i = 0; i < tal_count(msgs); i++)
@@ -5782,6 +5813,7 @@ static void req_in(struct peer *peer, const u8 *msg)
 	case WIRE_CHANNELD_UPDATE_INFLIGHT:
 	case WIRE_CHANNELD_GOT_INFLIGHT:
 	case WIRE_CHANNELD_SPLICE_STATE_ERROR:
+	case WIRE_CHANNELD_LOCAL_ANCHOR_INFO:
 		break;
 	}
 	master_badmsg(-1, msg);

channeld/channeld_wire.csv

@@ -128,6 +128,18 @@ msgdata,channeld_got_splice_locked,locked_txid,bitcoin_txid,
 
 #include <common/penalty_base.h>
 
+subtype,local_anchor_info
+subtypedata,local_anchor_info,commitment_weight,u32,
+subtypedata,local_anchor_info,commitment_fee,amount_sat,
+subtypedata,local_anchor_info,anchor_point,bitcoin_outpoint,
+
+# lightningd needs to track our anchor outputs on remote txs.
+# This includes splices, so there could be more than one!
+msgtype,channeld_local_anchor_info,1003
+msgdata,channeld_local_anchor_info,remote_commitnum,u64,
+msgdata,channeld_local_anchor_info,num_anchors,u16,
+msgdata,channeld_local_anchor_info,anchors,local_anchor_info,num_anchors
+
 # When we send a commitment_signed message, tell master.
 msgtype,channeld_sending_commitsig,1020
 msgdata,channeld_sending_commitsig,commitnum,u64,
@@ -138,6 +150,7 @@ msgdata,channeld_sending_commitsig,blockheight_states,height_states,
 msgdata,channeld_sending_commitsig,num_changed,u16,
 msgdata,channeld_sending_commitsig,changed,changed_htlc,num_changed
 
+
 # Wait for reply, to make sure it's on disk before we send commit.
 msgtype,channeld_sending_commitsig_reply,1120
 

channeld/full_channel.c

@@ -309,13 +309,13 @@ struct bitcoin_tx **channel_txs(const tal_t *ctx,
 				u64 commitment_number,
 				enum side side,
 				s64 splice_amnt,
-				s64 remote_splice_amnt)
+				s64 remote_splice_amnt,
+				int *other_anchor_outnum)
 {
 	struct bitcoin_tx **txs;
 	const struct htlc **committed;
 	struct keyset keyset;
 	struct amount_msat side_pay, other_side_pay;
-	int local_anchor;
 
 	if (!derive_keyset(per_commitment_point,
 			   &channel->basepoints[side],
@@ -364,7 +364,7 @@ struct bitcoin_tx **channel_txs(const tal_t *ctx,
 	    commitment_number ^ channel->commitment_number_obscurer,
 	    channel_has(channel, OPT_ANCHOR_OUTPUTS),
 	    channel_has(channel, OPT_ANCHORS_ZERO_FEE_HTLC_TX),
-	    side, &local_anchor);
+	    side, other_anchor_outnum);
 
 	/* Set the remote/local pubkeys on the commitment tx psbt */
 	psbt_input_add_pubkey(txs[0]->psbt, 0,

channeld/full_channel.h

@@ -66,6 +66,7 @@ struct channel *new_full_channel(const tal_t *ctx,
  * @side: which side to get the commitment transaction for
  * @local_splice_amnt: how much is being spliced in (or out, if -ve) of local side.
  * @remote_splice_amnt: how much is being spliced in (or out, if -ve) of remote side.
+ * @other_anchor_outnum: which output (-1 if none) is the !!side anchor
  *
  * Returns the unsigned commitment transaction for the committed state
  * for @side, followed by the htlc transactions in output order and
@@ -82,7 +83,8 @@ struct bitcoin_tx **channel_txs(const tal_t *ctx,
 				u64 commitment_number,
 				enum side side,
 				s64 local_splice_amnt,
-				s64 remote_splice_amnt);
+				s64 remote_splice_amnt,
+				int *local_anchor_outnum);
 
 /**
  * actual_feerate: what is the actual feerate for the local side.

channeld/test/run-full_channel.c

@@ -541,7 +541,8 @@ int main(int argc, const char *argv[])
 
 	txs = channel_txs(tmpctx, &funding, funding_amount,
 			  &htlc_map, NULL, &funding_wscript_alt,
-			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0);
+			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0,
+			  &local_anchor);
 	assert(tal_count(txs) == 1);
 	assert(tal_count(htlc_map) == 2);
 	assert(scripteq(funding_wscript_alt, funding_wscript));
@@ -549,7 +550,8 @@ int main(int argc, const char *argv[])
 
 	txs2 = channel_txs(tmpctx, &funding, funding_amount,
 			   &htlc_map, NULL, &funding_wscript,
-			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0);
+			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0,
+			   &local_anchor);
 	txs_must_be_eq(txs, txs2);
 
 	/* BOLT #3:
@@ -577,11 +579,13 @@ int main(int argc, const char *argv[])
 
 	txs = channel_txs(tmpctx, &funding, funding_amount,
 			  &htlc_map, NULL, &funding_wscript,
-			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0);
+			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0,
+			  &local_anchor);
 	assert(tal_count(txs) == 1);
 	txs2 = channel_txs(tmpctx, &funding, funding_amount,
 			   &htlc_map, NULL, &funding_wscript,
-			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0);
+			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0,
+			   &local_anchor);
 	txs_must_be_eq(txs, txs2);
 
 	update_feerate(lchannel, feerate_per_kw[LOCAL]);
@@ -597,11 +601,13 @@ int main(int argc, const char *argv[])
 
 	txs = channel_txs(tmpctx, &funding, funding_amount,
 			  &htlc_map, NULL, &funding_wscript,
-			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0);
+			  lchannel, &local_per_commitment_point, 42, LOCAL, 0, 0,
+			  &local_anchor);
 	assert(tal_count(txs) == 6);
 	txs2 = channel_txs(tmpctx, &funding, funding_amount,
 			   &htlc_map, NULL, &funding_wscript,
-			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0);
+			   rchannel, &local_per_commitment_point, 42, REMOTE, 0, 0,
+			   &local_anchor);
 	txs_must_be_eq(txs, txs2);
 
 	/* FIXME: Compare signatures! */
@@ -675,13 +681,15 @@ int main(int argc, const char *argv[])
 		txs = channel_txs(tmpctx, &funding, funding_amount,
 				  &htlc_map, NULL, &funding_wscript,
 				  lchannel, &local_per_commitment_point, 42,
-				  LOCAL, 0, 0);
+				  LOCAL, 0, 0,
+				  &local_anchor);
 		tx_must_be_eq(txs[0], raw_tx);
 
 		txs2 = channel_txs(tmpctx, &funding, funding_amount,
 				   &htlc_map, NULL, &funding_wscript,
 				   rchannel, &local_per_commitment_point,
-				   42, REMOTE, 0, 0);
+				   42, REMOTE, 0, 0,
+				   &local_anchor);
 		txs_must_be_eq(txs, txs2);
 	}
 

devtools/mkcommit.c

@@ -270,6 +270,7 @@ int main(int argc, char *argv[])
 	const struct channel_type *channel_type;
 	struct sha256_double hash;
 	u32 blockheight = 0;
+	int local_anchor_outnum;
 
 	setup_locale();
 	chainparams = chainparams_for_network("bitcoin");
@@ -425,7 +426,7 @@ int main(int argc, char *argv[])
 	local_txs = channel_txs(NULL, &channel->funding, channel->funding_sats,
 				&htlcmap, NULL, &funding_wscript, channel,
 				&local_per_commit_point, commitnum,
-				LOCAL, 0, 0);
+				LOCAL, 0, 0, &local_anchor_outnum);
 
 	printf("## local_commitment\n"
 	       "# input amount %s, funding_wscript %s, pubkey %s\n",
@@ -536,7 +537,7 @@ int main(int argc, char *argv[])
 	remote_txs = channel_txs(NULL, &channel->funding, channel->funding_sats,
 				 &htlcmap, NULL, &funding_wscript, channel,
 				 &remote_per_commit_point, commitnum,
-				 REMOTE, 0, 0);
+				 REMOTE, 0, 0, &local_anchor_outnum);
 
 	printf("## remote_commitment\n"
 	       "# input amount %s, funding_wscript %s, key %s\n",

lightningd/channel_control.c

@@ -1228,6 +1228,9 @@ static unsigned channel_msg(struct subd *sd, const u8 *msg, const int *fds)
 	case WIRE_CHANNELD_SENDING_COMMITSIG:
 		peer_sending_commitsig(sd->channel, msg);
 		break;
+	case WIRE_CHANNELD_LOCAL_ANCHOR_INFO:
+		/* FIXME */
+		break;
 	case WIRE_CHANNELD_GOT_COMMITSIG:
 		peer_got_commitsig(sd->channel, msg);
 		break;