channeld: include last sent commit and last revoke in init message.

It's easiest to have the master keep the last commit we sent, for
re-transmission.  We could recalculate it, but it's made more difficult
by the before/after revoke case.

And because revoke_and_ack changes the channel state, we need to
remember which order we sent them in for re-transmission.

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

lightningd/channel/channel.c

@@ -1219,7 +1219,8 @@ static void init_channel(struct peer *peer)
 	u64 local_msatoshi;
 	struct pubkey funding_pubkey[NUM_SIDES];
 	struct sha256_double funding_txid;
-	bool am_funder;
+	bool am_funder, last_was_revoke;
+	struct changed_htlc *last_sent_commit;
 	u8 *funding_signed;
 	u8 *msg;
 
@@ -1243,6 +1244,8 @@ static void init_channel(struct peer *peer)
 				   &peer->node_ids[REMOTE],
 				   &peer->commit_msec,
 				   &peer->cltv_delta,
+				   &last_was_revoke,
+				   &last_sent_commit,
 				   &funding_signed))
 		status_failed(WIRE_CHANNEL_BAD_COMMAND, "Init: %s",
 			      tal_hex(msg, msg));

lightningd/channel/channel_wire.csv

@@ -40,6 +40,9 @@ channel_init,,local_node_id,struct pubkey
 channel_init,,remote_node_id,struct pubkey
 channel_init,,commit_msec,4
 channel_init,,cltv_delta,u16
+channel_init,,last_was_revoke,bool
+channel_init,,num_last_sent_commit,u16
+channel_init,,last_sent_commit,num_last_sent_commit*struct changed_htlc
 channel_init,,init_peer_pkt_len,u16
 channel_init,,init_peer_pkt,init_peer_pkt_len*u8
 

lightningd/peer_control.c

@@ -297,6 +297,8 @@ void add_peer(struct lightningd *ld, u64 unique_id,
 	peer->state = UNINITIALIZED;
 	peer->channel_info = NULL;
 	peer->next_per_commitment_point = NULL;
+	peer->last_was_revoke = false;
+	peer->last_sent_commit = NULL;
 	peer->num_commits_sent = peer->num_commits_received
 		= peer->num_revocations_received = 0;
 	shachain_init(&peer->their_shachain);
@@ -960,6 +962,8 @@ static bool peer_start_channeld_hsmfd(struct subd *hsm, const u8 *resp,
 				      &peer->id,
 				      time_to_msec(cfg->commit_time),
 				      cfg->deadline_blocks,
+				      peer->last_was_revoke,
+				      peer->last_sent_commit,
 				      peer->funding_signed);
 
 	/* Don't need this any more (we never re-transmit it) */

lightningd/peer_control.h

@@ -86,6 +86,10 @@ struct peer {
 
 	/* Gossip client fd, forwarded to the respective owner */
 	int gossip_client_fd;
+
+	/* Reestablishment stuff: last sent commit and revocation details. */
+	bool last_was_revoke;
+	struct changed_htlc *last_sent_commit;
 };
 
 static inline bool peer_can_add_htlc(const struct peer *peer)

lightningd/peer_htlcs.c

@@ -793,6 +793,11 @@ int peer_sending_commitsig(struct peer *peer, const u8 *msg)
 
 	peer->num_commits_sent++;
 
+	/* Last was commit. */
+	peer->last_was_revoke = false;
+	tal_free(peer->last_sent_commit);
+	peer->last_sent_commit = tal_steal(peer, changed_htlcs);
+
 	/* Tell it we've got it, and to go ahead with commitment_signed. */
 	subd_send_msg(peer->owner,
 		      take(towire_channel_sending_commitsig_reply(msg)));
@@ -860,6 +865,7 @@ static bool peer_sending_revocation(struct peer *peer,
 		}
 	}
 
+	peer->last_was_revoke = true;
 	return true;
 }