channeld: make channel_fulfill_htlc return the HTLC it fulfulled.

This is the same pattern as channel_fail_htlc, and in fact one caller
wanted it already.

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

channeld/channel.c

@@ -1472,7 +1472,7 @@ static void handle_peer_fulfill_htlc(struct peer *peer, const u8 *msg)
 			    "Bad update_fulfill_htlc %s", tal_hex(msg, msg));
 	}
 
-	e = channel_fulfill_htlc(peer->channel, LOCAL, id, &preimage);
+	e = channel_fulfill_htlc(peer->channel, LOCAL, id, &preimage, NULL);
 	switch (e) {
 	case CHANNEL_ERR_REMOVE_OK:
 		/* FIXME: We could send preimages to master immediately. */
@@ -1509,11 +1509,10 @@ static void handle_peer_fail_htlc(struct peer *peer, const u8 *msg)
 			    "Bad update_fulfill_htlc %s", tal_hex(msg, msg));
 	}
 
-	e = channel_fail_htlc(peer->channel, LOCAL, id, NULL);
+	e = channel_fail_htlc(peer->channel, LOCAL, id, &htlc);
 	switch (e) {
 	case CHANNEL_ERR_REMOVE_OK:
 		/* Save reason for when we tell master. */
-		htlc = channel_get_htlc(peer->channel, LOCAL, id);
 		htlc->fail = tal_steal(htlc, reason);
 		start_commit_timer(peer);
 		return;
@@ -2202,7 +2201,7 @@ static void handle_preimage(struct peer *peer, const u8 *inmsg)
 	if (!fromwire_channel_fulfill_htlc(inmsg, &id, &preimage))
 		master_badmsg(WIRE_CHANNEL_FULFILL_HTLC, inmsg);
 
-	switch (channel_fulfill_htlc(peer->channel, REMOTE, id, &preimage)) {
+	switch (channel_fulfill_htlc(peer->channel, REMOTE, id, &preimage, NULL)) {
 	case CHANNEL_ERR_REMOVE_OK:
 		msg = towire_update_fulfill_htlc(NULL, &peer->channel_id,
 						 id, &preimage);

channeld/full_channel.c

@@ -493,9 +493,10 @@ struct htlc *channel_get_htlc(struct channel *channel, enum side sender, u64 id)
 }
 
 enum channel_remove_err channel_fulfill_htlc(struct channel *channel,
-					      enum side owner,
-					      u64 id,
-					      const struct preimage *preimage)
+					     enum side owner,
+					     u64 id,
+					     const struct preimage *preimage,
+					     struct htlc **htlcp)
 {
 	struct sha256 hash;
 	struct htlc *htlc;
@@ -556,6 +557,9 @@ enum channel_remove_err channel_fulfill_htlc(struct channel *channel,
 
 	dump_htlc(htlc, "FULFILL:");
 
+	if (htlcp)
+		*htlcp = htlc;
+
 	return CHANNEL_ERR_REMOVE_OK;
 }
 

channeld/full_channel.h

@@ -129,6 +129,7 @@ enum channel_remove_err channel_fail_htlc(struct channel *channel,
  * @channel: The channel state
  * @owner: the side who offered the HTLC (opposite to that fulfilling it)
  * @id: unique HTLC id.
+ * @htlcp: optional pointer for resulting htlc: filled in if and only if CHANNEL_ERR_FULFILL_OK.
  *
  * If the htlc exists, is not already fulfilled, the preimage is correct and
  * HTLC committed at the recipient, this will add a pending change to
@@ -138,7 +139,8 @@ enum channel_remove_err channel_fail_htlc(struct channel *channel,
 enum channel_remove_err channel_fulfill_htlc(struct channel *channel,
 					     enum side owner,
 					     u64 id,
-					     const struct preimage *preimage);
+					     const struct preimage *preimage,
+					     struct htlc **htlcp);
 
 /**
  * approx_max_feerate: what's the max funder could raise fee rate to?

channeld/test/run-full_channel.c

@@ -250,7 +250,7 @@ static void send_and_fulfill_htlc(struct channel *channel,
 		assert(ret);
 		ret = channel_sending_revoke_and_ack(channel);
 		assert(!ret);
-		assert(channel_fulfill_htlc(channel, LOCAL, 1337, &r)
+		assert(channel_fulfill_htlc(channel, LOCAL, 1337, &r, NULL)
 		       == CHANNEL_ERR_REMOVE_OK);
 		ret = channel_rcvd_commit(channel, &changed_htlcs);
 		assert(ret);
@@ -271,7 +271,7 @@ static void send_and_fulfill_htlc(struct channel *channel,
 		assert(ret);
 		ret = channel_rcvd_revoke_and_ack(channel, &changed_htlcs);
 		assert(!ret);
-		assert(channel_fulfill_htlc(channel, REMOTE, 1337, &r)
+		assert(channel_fulfill_htlc(channel, REMOTE, 1337, &r, NULL)
 		       == CHANNEL_ERR_REMOVE_OK);
 		ret = channel_sending_commit(channel, &changed_htlcs);
 		assert(ret);