peer: save txid -> commit_num mapping.

This is in preparation for placing it in a database.

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

daemon/peer.c

@@ -56,6 +56,15 @@ static bool command_htlc_fail(struct peer *peer, struct htlc *htlc);
 static bool command_htlc_fulfill(struct peer *peer, struct htlc *htlc);
 static void try_commit(struct peer *peer);
 
+void peer_add_their_commit(struct peer *peer,
+			   const struct sha256_double *txid, u64 commit_num)
+{
+	struct their_commit *tc = tal(peer, struct their_commit);
+	tc->txid = *txid;
+	tc->commit_num = commit_num;
+	list_add_tail(&peer->their_commits, &tc->list);
+}
+
 /* Create a bitcoin close tx, using last signature they sent. */
 static const struct bitcoin_tx *bitcoin_close(struct peer *peer)
 {
@@ -1733,6 +1742,8 @@ static void do_commit(struct peer *peer, struct command *jsoncmd)
 	/* Switch to the new commitment. */
 	peer->remote.commit = ci;
 
+	peer_add_their_commit(peer, &ci->txid, ci->commit_num);
+	
 	queue_pkt_commit(peer);
 	if (peer->state == STATE_CLEARING) {
 		set_peer_state(peer, STATE_CLEARING_COMMITTING, __func__);
@@ -1792,6 +1803,7 @@ static struct peer *new_peer(struct lightningd_state *dstate,
 	peer->commit_jsoncmd = NULL;
 	list_head_init(&peer->outgoing_txs);
 	list_head_init(&peer->pay_commands);
+	list_head_init(&peer->their_commits);
 	peer->anchor.ok_depth = -1;
 	peer->cur_commit.watch = NULL;
 	peer->closing.their_sig = NULL;

daemon/peer.h

@@ -55,6 +55,18 @@ struct anchor_input {
 	struct wallet *w;
 };
 
+/* Information we remember for their commitment txs which we signed.
+ *
+ * Given the commit_num, we can use shachain to derive the revocation preimage
+ * (if we've received it yet: we might have not, for the last).
+ */
+struct their_commit {
+	struct list_node list;
+
+	struct sha256_double txid;
+	u64 commit_num;
+};
+	
 struct commit_info {
 	/* Previous one, if any. */
 	struct commit_info *prev;
@@ -137,6 +149,9 @@ struct peer {
 	/* Queue of output packets. */
 	Pkt **outpkt;
 
+	/* Their commitments we have signed (which could appear on chain). */
+	struct list_head their_commits;
+	
 	/* Anchor tx output */
 	struct {
 		struct sha256_double txid;
@@ -226,6 +241,10 @@ struct peer *find_peer(struct lightningd_state *dstate, const struct pubkey *id)
 /* Populates very first peer->{local,remote}.commit->{tx,cstate} */
 bool setup_first_commit(struct peer *peer);
 
+/* Whenever we send a signature, remember the txid -> commit_num mapping */
+void peer_add_their_commit(struct peer *peer,
+			   const struct sha256_double *txid, u64 commit_num);
+
 /* Allocate a new commit_info struct. */
 struct commit_info *new_commit_info(const tal_t *ctx);
 

state.c

@@ -154,6 +154,8 @@ enum state state(struct peer *peer,
 			peer->remote.commit->sig->stype = SIGHASH_ALL;
 			peer_sign_theircommit(peer, peer->remote.commit->tx,
 					      &peer->remote.commit->sig->sig);
+			peer_add_their_commit(peer, &peer->remote.commit->txid,
+					      peer->remote.commit->commit_num);
 
 			queue_pkt_open_commit_sig(peer);
 			peer_watch_anchor(peer,