wallet: Add msatoshi_to_us_min and msatoshi_to_us_max statistics for channels.

So we know how much counterparty could theoretically steal from us
 (msatoshi_to_us - msatoshi_to_us_min) and how much we could
 theoretically steal from counterparty (msatoshi_to_us_max -
 msatoshi_to_us).
For more piloting goodness.

lightningd/channel.c

@@ -139,6 +139,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    /* NULL or stolen */
 			    struct short_channel_id *scid,
 			    u64 our_msatoshi,
+			    u64 msatoshi_to_us_min,
+			    u64 msatoshi_to_us_max,
 			    /* Stolen */
 			    struct bitcoin_tx *last_tx,
 			    const secp256k1_ecdsa_signature *last_sig,
@@ -196,6 +198,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->remote_funding_locked = remote_funding_locked;
 	channel->scid = tal_steal(channel, scid);
 	channel->our_msatoshi = our_msatoshi;
+	channel->msatoshi_to_us_min = msatoshi_to_us_min;
+	channel->msatoshi_to_us_max = msatoshi_to_us_max;
 	channel->last_tx = tal_steal(channel, last_tx);
 	channel->last_sig = *last_sig;
 	channel->last_htlc_sigs = tal_steal(channel, last_htlc_sigs);

lightningd/channel.h

@@ -66,6 +66,9 @@ struct channel {
 
 	/* Amount going to us, not counting unfinished HTLCs; if we have one. */
 	u64 our_msatoshi;
+	/* Statistics for min and max our_msatoshi. */
+	u64 msatoshi_to_us_min;
+	u64 msatoshi_to_us_max;
 
 	/* Last tx they gave us. */
 	struct bitcoin_tx *last_tx;
@@ -117,6 +120,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    /* NULL or stolen */
 			    struct short_channel_id *scid,
 			    u64 our_msatoshi,
+			    u64 msatoshi_to_us_min,
+			    u64 msatoshi_to_us_max,
 			    /* Stolen */
 			    struct bitcoin_tx *last_tx,
 			    const secp256k1_ecdsa_signature *last_sig,

lightningd/opening_control.c

@@ -203,7 +203,13 @@ wallet_commit_channel(struct lightningd *ld,
 			      push_msat,
 			      false, /* !remote_funding_locked */
 			      NULL, /* no scid yet */
+			      /* The three arguments below are msatoshi_to_us,
+			       * msatoshi_to_us_min, and msatoshi_to_us_max.
+			       * Because, this is a newly-funded channel,
+			       * all three are same value. */
 			      our_msatoshi,
+			      our_msatoshi, /* msatoshi_to_us_min */
+			      our_msatoshi, /* msatoshi_to_us_max */
 			      remote_commit,
 			      remote_commit_sig,
 			      NULL, /* No HTLC sigs yet */

lightningd/peer_control.c

@@ -678,6 +678,10 @@ static void gossipd_getpeers_complete(struct subd *gossip, const u8 *msg,
 				      &channel->funding_txid);
 			json_add_u64(response, "msatoshi_to_us",
 				     channel->our_msatoshi);
+			json_add_u64(response, "msatoshi_to_us_min",
+				     channel->msatoshi_to_us_min);
+			json_add_u64(response, "msatoshi_to_us_max",
+				     channel->msatoshi_to_us_max);
 			json_add_u64(response, "msatoshi_total",
 				     channel->funding_satoshi * 1000);
 

lightningd/peer_htlcs.c

@@ -843,6 +843,8 @@ static void remove_htlc_in(struct channel *channel, struct htlc_in *hin)
 			  channel->our_msatoshi,
 			  channel->our_msatoshi + hin->msatoshi);
 		channel->our_msatoshi += hin->msatoshi;
+		if (channel->our_msatoshi > channel->msatoshi_to_us_max)
+			channel->msatoshi_to_us_max = channel->our_msatoshi;
 	}
 
 	tal_free(hin);
@@ -867,6 +869,8 @@ static void remove_htlc_out(struct channel *channel, struct htlc_out *hout)
 			  channel->our_msatoshi,
 			  channel->our_msatoshi - hout->msatoshi);
 		channel->our_msatoshi -= hout->msatoshi;
+		if (channel->our_msatoshi < channel->msatoshi_to_us_min)
+			channel->msatoshi_to_us_min = channel->our_msatoshi;
 	}
 
 	tal_free(hout);

wallet/db.c

@@ -282,6 +282,14 @@ char *dbmigrations[] = {
     /* https://bitcoinfees.github.io/#1d says Dec 17 peak was ~1M sat/kb
      * which is 250,000 sat/Sipa */
     "UPDATE channels SET min_possible_feerate=0, max_possible_feerate=250000;",
+    /* -- Min and max msatoshi_to_us -- */
+    "ALTER TABLE channels ADD msatoshi_to_us_min INTEGER;",
+    "ALTER TABLE channels ADD msatoshi_to_us_max INTEGER;",
+    "UPDATE channels"
+    "   SET msatoshi_to_us_min = msatoshi_local"
+    "     , msatoshi_to_us_max = msatoshi_local"
+    "     ;",
+    /* -- Min and max msatoshi_to_us ends -- */
     NULL,
 };
 

wallet/wallet.c

@@ -636,6 +636,8 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 			   sqlite3_column_int(stmt, 15) != 0,
 			   scid,
 			   sqlite3_column_int64(stmt, 17),
+			   sqlite3_column_int64(stmt, 38), /* msatoshi_to_us_min */
+			   sqlite3_column_int64(stmt, 39), /* msatoshi_to_us_max */
 			   sqlite3_column_tx(tmpctx, stmt, 32),
 			   &last_sig,
 			   wallet_htlc_sigs_load(tmpctx, w,
@@ -654,22 +656,24 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 
 /* List of fields to retrieve from the channels DB table, in the order
  * that wallet_stmt2channel understands and will parse correctly */
+/* Numbers below are sqlite3_column indices for the first field
+ * of that line. */
 static const char *channel_fields =
-    "id, peer_id, short_channel_id, channel_config_local, "
+    /*0*/ "id, peer_id, short_channel_id, channel_config_local, "
-    "channel_config_remote, state, funder, channel_flags, "
+    /*4*/ "channel_config_remote, state, funder, channel_flags, "
-    "minimum_depth, "
+    /*8*/ "minimum_depth, "
-    "next_index_local, next_index_remote, "
+    /*9*/ "next_index_local, next_index_remote, "
-    "next_htlc_id, funding_tx_id, funding_tx_outnum, funding_satoshi, "
+    /*11*/ "next_htlc_id, funding_tx_id, funding_tx_outnum, funding_satoshi, "
-    "funding_locked_remote, push_msatoshi, msatoshi_local, "
+    /*15*/ "funding_locked_remote, push_msatoshi, msatoshi_local, "
-    "fundingkey_remote, revocation_basepoint_remote, "
+    /*18*/ "fundingkey_remote, revocation_basepoint_remote, "
-    "payment_basepoint_remote, htlc_basepoint_remote, "
+    /*20*/ "payment_basepoint_remote, htlc_basepoint_remote, "
-    "delayed_payment_basepoint_remote, per_commit_remote, "
+    /*22*/ "delayed_payment_basepoint_remote, per_commit_remote, "
-    "old_per_commit_remote, local_feerate_per_kw, remote_feerate_per_kw, shachain_remote_id, "
+    /*24*/ "old_per_commit_remote, local_feerate_per_kw, remote_feerate_per_kw, shachain_remote_id, "
-    "shutdown_scriptpubkey_remote, shutdown_keyidx_local, "
+    /*28*/ "shutdown_scriptpubkey_remote, shutdown_keyidx_local, "
-    "last_sent_commit_state, last_sent_commit_id, "
+    /*30*/ "last_sent_commit_state, last_sent_commit_id, "
-    "last_tx, last_sig, last_was_revoke, first_blocknum, "
+    /*32*/ "last_tx, last_sig, last_was_revoke, first_blocknum, "
-    " min_possible_feerate, max_possible_feerate";
+    /*36*/ "min_possible_feerate, max_possible_feerate, "
-
+    /*38*/ "msatoshi_to_us_min, msatoshi_to_us_max ";
 
 bool wallet_channels_load_active(const tal_t *ctx, struct wallet *w)
 {
@@ -924,7 +928,9 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 			  "  last_tx=?, last_sig=?,"
 			  "  last_was_revoke=?,"
 			  "  min_possible_feerate=?,"
-			  "  max_possible_feerate=?"
+			  "  max_possible_feerate=?,"
+			  "  msatoshi_to_us_min=?,"
+			  "  msatoshi_to_us_max=?"
 			  " WHERE id=?");
 	sqlite3_bind_int64(stmt, 1, chan->their_shachain.id);
 	if (chan->scid)
@@ -958,7 +964,9 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 	sqlite3_bind_int(stmt, 21, chan->last_was_revoke);
 	sqlite3_bind_int(stmt, 22, chan->min_possible_feerate);
 	sqlite3_bind_int(stmt, 23, chan->max_possible_feerate);
-	sqlite3_bind_int64(stmt, 24, chan->dbid);
+	sqlite3_bind_int64(stmt, 24, chan->msatoshi_to_us_min);
+	sqlite3_bind_int64(stmt, 25, chan->msatoshi_to_us_max);
+	sqlite3_bind_int64(stmt, 26, chan->dbid);
 	db_exec_prepared(w->db, stmt);
 
 	wallet_channel_config_save(w, &chan->channel_info.their_config);