splice: Changing encoding of TLV funding_txid

Using the wrong encoding flips the bytes. We have to use sha256 as the spec says to prevent them from flipping.

Author: ddustin

channeld/channeld.c

@@ -1202,7 +1202,7 @@ static u8 *send_commit_part(const tal_t *ctx,
 					  struct tlv_commitment_signed_tlvs_splice_info);
 
 		cs_tlv->splice_info->batch_size = batch_size;
-		derive_channel_id(&cs_tlv->splice_info->funding_txid, funding);
+		cs_tlv->splice_info->funding_txid = funding->txid;
 	}
 
 	txs = channel_txs(tmpctx, funding, funding_sats, &htlc_map,
@@ -1932,7 +1932,6 @@ static struct commitsig_info *handle_peer_commit_sig(struct peer *peer,
 	const u8 * msg2;
 	struct bitcoin_outpoint outpoint;
 	struct amount_sat funding_sats;
-	struct channel_id active_id;
 	const struct commitsig **commitsigs;
 	int remote_anchor_outnum;
 	struct pubkey funding_pubkeys[NUM_SIDES] =
@@ -1958,16 +1957,16 @@ static struct commitsig_info *handle_peer_commit_sig(struct peer *peer,
 	 * ...
 	 *     - MUST ignore `commitment_signed` messages where `splice_channel_id`
 	 *       does not match the `channel_id` of the confirmed splice. */
-	derive_channel_id(&active_id, &peer->channel->funding);
 	if (peer->splice_state->await_commitment_succcess
 	    && !tal_count(peer->splice_state->inflights) && cs_tlv && cs_tlv->splice_info) {
-		if (!channel_id_eq(&active_id,
-				   &cs_tlv->splice_info->funding_txid)) {
+	    	if (!bitcoin_txid_eq(&peer->channel->funding.txid,
+	    			     &cs_tlv->splice_info->funding_txid)) {
 			status_info("Ignoring stale commit_sig for channel_id"
 				    " %s, as %s is locked in now.",
-				    fmt_channel_id(tmpctx,
-				    		   &cs_tlv->splice_info->funding_txid),
-				    fmt_channel_id(tmpctx, &active_id));
+				    fmt_bitcoin_txid(tmpctx,
+				    		     &cs_tlv->splice_info->funding_txid),
+				    fmt_bitcoin_txid(tmpctx,
+				    		     &peer->channel->funding.txid));
 			return NULL;
 		}
 	}
@@ -2069,8 +2068,8 @@ static struct commitsig_info *handle_peer_commit_sig(struct peer *peer,
 				 fmt_bitcoin_outpoint(tmpctx, &outpoint),
 				 fmt_amount_sat(tmpctx, funding_sats),
 				 cs_tlv && cs_tlv->splice_info
-				 	? fmt_channel_id(tmpctx,
-							 &cs_tlv->splice_info->funding_txid)
+				 	? fmt_bitcoin_txid(tmpctx,
+							   &cs_tlv->splice_info->funding_txid)
 				 	: "N/A",
 				 peer->splice_state->await_commitment_succcess ? "yes"
 				 					: "no",

wire/peer_wire.csv

@@ -301,7 +301,7 @@ msgdata,commitment_signed,htlc_signature,signature,num_htlcs
 msgdata,commitment_signed,splice_channel_id,commitment_signed_tlvs,
 tlvtype,commitment_signed_tlvs,splice_info,0
 tlvdata,commitment_signed_tlvs,splice_info,batch_size,u16,
-tlvdata,commitment_signed_tlvs,splice_info,funding_txid,channel_id,
+tlvdata,commitment_signed_tlvs,splice_info,funding_txid,sha256,
 msgtype,revoke_and_ack,133
 msgdata,revoke_and_ack,channel_id,channel_id,
 msgdata,revoke_and_ack,per_commitment_secret,byte,32

wire/test/run-peer-wire.c

@@ -40,9 +40,9 @@ static void set_scid(struct short_channel_id *scid)
 	memset(scid, 2, sizeof(struct short_channel_id));
 }
 
-static void set_cid(struct channel_id *cid)
+static void set_bitcoin_txid(struct bitcoin_txid *cid)
 {
-	memset(cid, 2, sizeof(struct channel_id));
+	memset(cid, 2, sizeof(struct bitcoin_txid));
 }
 
 /* Size up to field. */
@@ -1028,7 +1028,7 @@ int main(int argc, char *argv[])
 	cs.tlvs = tlv_commitment_signed_tlvs_new(tmpctx);
 	cs.tlvs->splice_info = tal(ctx, struct tlv_commitment_signed_tlvs_splice_info);
 	cs.tlvs->splice_info->batch_size = 1;
-	set_cid(&cs.tlvs->splice_info->funding_txid);
+	set_bitcoin_txid(&cs.tlvs->splice_info->funding_txid);
 
 	msg = towire_struct_commitment_signed(ctx, &cs);
 	cs2 = fromwire_struct_commitment_signed(ctx, msg);