daemon: fix close fee negotiation.

We always set *matches to false (outside the branch, oops).  We also
distinguish the case where we ack from the case where they acked,
which removes a FIXME and makes it work.

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

daemon/packets.c

@@ -405,6 +405,8 @@ void queue_pkt_close_signature(struct peer *peer)
 	peer_sign_mutual_close(peer, close_tx, &our_close_sig);
 	c->sig = signature_to_proto(c, &our_close_sig);
 	c->close_fee = peer->closing.our_fee;
+	log_info(peer->log, "queue_pkt_close_signature: offered close fee %"
+		 PRIu64, c->close_fee);
 
 	queue_pkt(peer, PKT__PKT_CLOSE_SIGNATURE, c);
 }
@@ -748,12 +750,17 @@ Pkt *accept_pkt_close_clearing(struct peer *peer, const Pkt *pkt)
 	return NULL;
 }
 
-Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt, bool *matches)
+Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt, bool *acked,
+			  bool *we_agree)
 {
 	const CloseSignature *c = pkt->close_signature;
 	struct bitcoin_tx *close_tx;
 	struct bitcoin_signature theirsig;
 
+	log_info(peer->log, "accept_pkt_close_sig: they offered close fee %"
+		 PRIu64, c->close_fee);
+	*acked = *we_agree = false;
+
 	/* BOLT #2:
 	 *
 	 * The sender MUST set `close_fee` lower than or equal to the fee of the
@@ -805,7 +812,8 @@ Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt, bool *matches)
 	peer->closing.their_fee = c->close_fee;
 
 	if (peer->closing.our_fee == peer->closing.their_fee) {
-		*matches = true;
+		log_info(peer->log, "accept_pkt_close_sig: That's an ack");
+		*acked = true;
 	} else {
 		/* Adjust our fee to close on their fee. */
 		u64 sum;
@@ -817,10 +825,13 @@ Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt, bool *matches)
 		if (peer->closing.our_fee & 1)
 			peer->closing.our_fee++;
 
-		/* FIXME: Fees may *now* be equal, and they'll
-		 * consider this an ACK! */
+		log_info(peer->log, "accept_pkt_close_sig: we change to %"PRIu64,
+			 peer->closing.our_fee);
+
+		/* Corner case: we may now agree with them. */
+		if (peer->closing.our_fee == peer->closing.their_fee)
+			*we_agree = true;
 	}
-	*matches = false;
 
 	/* FIXME: Dynamic fee! */
 	return NULL;

state.c

@@ -516,13 +516,21 @@ enum command_status state(struct peer *peer,
 		break;
 	case STATE_WAIT_FOR_CLOSE_SIG:
 		if (input_is(input, PKT_CLOSE_SIGNATURE)) {
-			bool matches;
-			err = accept_pkt_close_sig(peer, idata->pkt, &matches);
+			bool acked, we_agree;
+			err = accept_pkt_close_sig(peer, idata->pkt,
+						   &acked, &we_agree);
 			if (err)
 				goto err_start_unilateral_close;
 
-			/* Did they offer the same fee we did? */
-			if (matches) {
+			/* Are we about to offer the same fee they did? */
+			if (we_agree) {
+				/* Offer the new fee. */
+				queue_pkt_close_signature(peer);
+				acked = true;
+			}
+
+			/* Do fees now match? */
+			if (acked) {
 				peer_unwatch_close_timeout(peer,
 						   INPUT_CLOSE_COMPLETE_TIMEOUT);
 

state.h

@@ -110,7 +110,8 @@ Pkt *accept_pkt_commit(struct peer *peer, const Pkt *pkt);
 
 Pkt *accept_pkt_revocation(struct peer *peer, const Pkt *pkt);
 Pkt *accept_pkt_close_clearing(struct peer *peer, const Pkt *pkt);
-Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt, bool *matches);
+Pkt *accept_pkt_close_sig(struct peer *peer, const Pkt *pkt,
+			  bool *acked, bool *we_agree);
 
 /**
  * committed_to_htlcs: do we have any locked-in HTLCs?