lightningd: save previous short_channel_ids during splice, and keep in db.

There can be any number of these, and it will be useful to allow
routing by older scids (when other nodes haven't seen our gossip, or
even before we *can* announce the new post-splice channel).

Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

lightningd/channel.c

@@ -242,6 +242,19 @@ struct open_attempt *new_channel_open_attempt(struct channel *channel)
 	return oa;
 }
 
+void channel_add_old_scid(struct channel *channel,
+			  struct short_channel_id old_scid)
+{
+	/* If this is not public, we skip */
+	if (!(channel->channel_flags & CHANNEL_FLAGS_ANNOUNCE_CHANNEL))
+		return;
+
+	if (!channel->old_scids)
+		channel->old_scids = tal_dup(channel, struct short_channel_id, &old_scid);
+	else
+		tal_arr_expand(&channel->old_scids, old_scid);
+}
+
 struct channel *new_unsaved_channel(struct peer *peer,
 				    u32 feerate_base,
 				    u32 feerate_ppm)
@@ -275,6 +288,7 @@ struct channel *new_unsaved_channel(struct peer *peer,
 	channel->last_htlc_sigs = NULL;
 	channel->remote_channel_ready = false;
 	channel->scid = NULL;
+	channel->old_scids = NULL;
 	channel->next_index[LOCAL] = 1;
 	channel->next_index[REMOTE] = 1;
 	channel->next_htlc_id = 0;
@@ -411,6 +425,7 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    bool remote_channel_ready,
 			    /* NULL or stolen */
 			    struct short_channel_id *scid,
+			    struct short_channel_id *old_scids TAKES,
 			    struct short_channel_id *alias_local TAKES,
 			    struct short_channel_id *alias_remote STEALS,
 			    struct channel_id *cid,
@@ -538,6 +553,7 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->our_funds = our_funds;
 	channel->remote_channel_ready = remote_channel_ready;
 	channel->scid = tal_steal(channel, scid);
+	channel->old_scids = tal_dup_talarr(channel, struct short_channel_id, old_scids);
 	channel->alias[LOCAL] = tal_dup_or_null(channel, struct short_channel_id, alias_local);
 	/* We always make sure this is set (historical channels from db might not) */
 	if (!channel->alias[LOCAL]) {

lightningd/channel.h

@@ -214,6 +214,8 @@ struct channel {
 	bool remote_channel_ready;
 	/* Channel if locked locally. */
 	struct short_channel_id *scid;
+	/* Old scids if we were spliced */
+	struct short_channel_id *old_scids;
 
 	/* Alias used for option_zeroconf, or option_scid_alias, if
 	 * present. LOCAL are all the alias we told the peer about and
@@ -388,6 +390,7 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    bool remote_channel_ready,
 			    /* NULL or stolen */
 			    struct short_channel_id *scid STEALS,
+			    struct short_channel_id *old_scids TAKES,
 			    struct short_channel_id *alias_local STEALS,
 			    struct short_channel_id *alias_remote STEALS,
 			    struct channel_id *cid,
@@ -487,6 +490,10 @@ u32 channel_last_funding_feerate(const struct channel *channel);
 /* Only set completely_eliminate for never-existed channels */
 void delete_channel(struct channel *channel STEALS, bool completely_eliminate);
 
+/* Add a historic (public) short_channel_id to this channel */
+void channel_add_old_scid(struct channel *channel,
+			  struct short_channel_id old_scid);
+
 const char *channel_state_name(const struct channel *channel);
 const char *channel_state_str(enum channel_state state);
 

lightningd/channel_control.c

@@ -815,12 +815,16 @@ bool depthcb_update_scid(struct channel *channel,
 			lockin_has_completed(channel, false);
 
 	} else {
+		struct short_channel_id old_scid = *channel->scid;
+
 		/* We freaked out if required when original was
 		 * removed, so just update now */
 		log_info(channel->log, "Short channel id changed from %s->%s",
 			 fmt_short_channel_id(tmpctx, *channel->scid),
 			 fmt_short_channel_id(tmpctx, scid));
 		*channel->scid = scid;
+		/* In case we broadcast it before (e.g. splice!) */
+		channel_add_old_scid(channel, old_scid);
 		channel_gossip_scid_changed(channel);
 	}
 

lightningd/opening_control.c

@@ -189,6 +189,7 @@ wallet_commit_channel(struct lightningd *ld,
 			      local_funding,
 			      false, /* !remote_channel_ready */
 			      NULL, /* no scid yet */
+			      NULL, /* no old scids */
 			      NULL, /* assign random local alias */
 			      NULL, /* They haven't told us an alias yet */
 			      cid,
@@ -1579,6 +1580,7 @@ static struct channel *stub_chan(struct command *cmd,
 			      AMOUNT_SAT(0),
 			      true, /* remote_channel_ready */
 			      scid,
+			      NULL,
 			      scid,
 			      scid,
 			      &cid,

wallet/db.c

@@ -1042,6 +1042,7 @@ static struct migration dbmigrations[] = {
     {NULL, NULL}, /* Old, incorrect channel_htlcs_wait_indexes migration */
     {SQL("ALTER TABLE channel_funding_inflights ADD locked_scid BIGINT DEFAULT 0;"), NULL},
     {NULL, migrate_initialize_channel_htlcs_wait_indexes_and_fixup_forwards},
+    {SQL("ALTER TABLE channels ADD old_scids BLOB DEFAULT NULL;"), NULL},
 };
 
 /**

wallet/test/run-db.c

@@ -188,6 +188,7 @@ struct channel *new_channel(struct peer *peer UNNEEDED, u64 dbid UNNEEDED,
 			    bool remote_channel_ready UNNEEDED,
 			    /* NULL or stolen */
 			    struct short_channel_id *scid STEALS UNNEEDED,
+			    struct short_channel_id *old_scids TAKES UNNEEDED,
 			    struct short_channel_id *alias_local STEALS UNNEEDED,
 			    struct short_channel_id *alias_remote STEALS UNNEEDED,
 			    struct channel_id *cid UNNEEDED,

wallet/test/run-wallet.c

@@ -2026,7 +2026,8 @@ static bool test_channel_inflight_crud(struct lightningd *ld, const tal_t *ctx)
 			   &outpoint,
 			   funding_sats, AMOUNT_MSAT(0),
 			   our_sats,
-			   0, false,
+			   0, NULL,
+			   NULL, /* old scids */
 			   NULL, /* alias[LOCAL] */
 			   NULL, /* alias[REMOTE] */
 			   &cid,

wallet/wallet.c

@@ -1774,7 +1774,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 	struct channel_info channel_info;
 	struct fee_states *fee_states;
 	struct height_states *height_states;
-	struct short_channel_id *scid, *alias[NUM_SIDES];
+	struct short_channel_id *scid, *alias[NUM_SIDES], *old_scids;
 	struct channel_id cid;
 	struct channel *chan;
 	u64 peer_dbid;
@@ -1813,6 +1813,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 	}
 
 	scid = db_col_optional_scid(tmpctx, stmt, "scid");
+	old_scids = db_col_short_channel_id_arr(tmpctx, stmt, "old_scids");
 	alias[LOCAL] = db_col_optional_scid(tmpctx, stmt, "alias_local");
 	alias[REMOTE] = db_col_optional_scid(tmpctx, stmt, "alias_remote");
 
@@ -2027,6 +2028,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 			   our_funding_sat,
 			   db_col_int(stmt, "funding_locked_remote") != 0,
 			   scid,
+			   old_scids,
 			   alias[LOCAL],
 			   alias[REMOTE],
 			   &cid,
@@ -2241,6 +2243,7 @@ static bool wallet_channels_load_active(struct wallet *w)
 					"  id"
 					", peer_id"
 					", scid"
+					", old_scids"
 					", full_channel_id"
 					", channel_config_local"
 					", channel_config_remote"
@@ -2521,6 +2524,7 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 	stmt = db_prepare_v2(w->db, SQL("UPDATE channels SET"
 					"  shachain_remote_id=?,"
 					"  scid=?,"
+					"  old_scids=?,"
 					"  full_channel_id=?,"
 					"  state=?,"
 					"  funder=?,"
@@ -2580,6 +2584,7 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 	else
 		db_bind_null(stmt);
 
+	db_bind_short_channel_id_arr(stmt, chan->old_scids);
 	db_bind_channel_id(stmt, &chan->cid);
 	db_bind_int(stmt, channel_state_in_db(chan->state));
 	db_bind_int(stmt, chan->opener);