daemon/watch: API to watch various bitcoin transactions.

This uses the functions in bitcoind to provide callbacks when various
things happen.

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

daemon/Makefile

@@ -22,7 +22,8 @@ DAEMON_SRC :=					\
 	daemon/netaddr.c			\
 	daemon/peer.c				\
 	daemon/secrets.c			\
-	daemon/timeout.c
+	daemon/timeout.c			\
+	daemon/watch.c
 DAEMON_OBJS := $(DAEMON_SRC:.c=.o)
 
 DAEMON_CLI_SRC := daemon/lightning-cli.c
@@ -44,7 +45,8 @@ DAEMON_HEADERS :=				\
 	daemon/peer.h				\
 	daemon/pseudorand.h			\
 	daemon/secrets.h			\
-	daemon/timeout.h
+	daemon/timeout.h			\
+	daemon/watch.h
 
 $(DAEMON_OBJS) $(DAEMON_LIB_OBJS) $(DAEMON_CLI_OBJS): $(DAEMON_HEADERS) $(DAEMON_JSMN_HEADERS) $(BITCOIN_HEADERS) $(CORE_HEADERS) $(GEN_HEADERS) $(CCAN_HEADERS)
 $(DAEMON_JSMN_OBJS): $(DAEMON_JSMN_HEADERS)

daemon/lightningd.c

@@ -121,6 +121,8 @@ static struct lightningd_state *lightningd_state(void)
 
 	list_head_init(&state->peers);
 	timers_init(&state->timers, time_now());
+	txwatch_hash_init(&state->txwatches);
+	txowatch_hash_init(&state->txowatches);
 	state->secpctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
 						  | SECP256K1_CONTEXT_SIGN);
 	default_config(&state->config);
@@ -203,6 +205,9 @@ int main(int argc, char *argv[])
 	/* Set up node ID and private key. */
 	secrets_init(state);
 
+	/* Create timer to do watches. */
+	setup_watch_timer(state);
+
 	log_info(state->base_log, "Hello world!");
 
 	/* If io_loop returns NULL, either a timer expired, or all fds closed */

daemon/lightningd.h

@@ -2,6 +2,7 @@
 #define LIGHTNING_DAEMON_LIGHTNING_H
 #include "config.h"
 #include "bitcoin/pubkey.h"
+#include "watch.h"
 #include <ccan/list/list.h>
 #include <ccan/short_types/short_types.h>
 #include <ccan/timer/timer.h>
@@ -63,5 +64,9 @@ struct lightningd_state {
 
 	/* Number of bitcoind commands outstanding. */
 	unsigned int bitcoind_in_progress;
+
+	/* Transactions/txos we are watching. */
+	struct txwatch_hash txwatches;
+	struct txowatch_hash txowatches;
 };
 #endif /* LIGHTNING_DAEMON_LIGHTNING_H */

daemon/peer.c

@@ -71,6 +71,7 @@ static struct peer *new_peer(struct lightningd_state *state,
 	peer->addr.protocol = addr_protocol;
 	peer->io_data = NULL;
 	peer->secrets = NULL;
+	list_head_init(&peer->watches);
 
 	/* FIXME: Attach IO logging for this peer. */
 	tal_add_destructor(peer, destroy_peer);

daemon/peer.h

@@ -1,6 +1,7 @@
 #ifndef LIGHTNING_DAEMON_PEER_H
 #define LIGHTNING_DAEMON_PEER_H
 #include "config.h"
+#include "bitcoin/pubkey.h"
 #include "lightning.pb-c.h"
 #include "netaddr.h"
 #include <ccan/list/list.h>
@@ -27,6 +28,9 @@ struct peer {
 	/* What happened. */
 	struct log *log;
 
+	/* Things we're watching for (see watches.c) */
+	struct list_head watches;
+	
 	/* Keys for transactions with this peer. */
 	struct pubkey their_commitkey, their_finalkey;
 	struct pubkey our_commitkey, our_finalkey;

daemon/watch.c

@@ -0,0 +1,230 @@
+/* Code to talk to bitcoind to watch for various events.
+ *
+ * Here's what we want to know:
+ *
+ * - An anchor tx:
+ *   - Reached given depth
+ *   - Times out.
+ *   - Is unspent after reaching given depth.
+ *
+ * - Our own commitment tx:
+ *   - Reached a given depth.
+ *
+ * - HTLC spend tx:
+ *   - Reached a given depth.
+ * 
+ * - Anchor tx output:
+ *   - Is spent by their current tx.
+ *   - Is spent by a revoked tx.
+ *
+ * - Commitment tx HTLC outputs:
+ *   - HTLC timed out
+ *   - HTLC spent
+ *
+ * We do this by adding the P2SH address to the wallet, and then querying
+ * that using listtransactions.
+ *
+ * WE ASSUME NO MALLEABILITY!  This requires segregated witness.
+ */
+#include "bitcoin/script.h"
+#include "bitcoin/tx.h"
+#include "bitcoind.h"
+#include "lightningd.h"
+#include "log.h"
+#include "peer.h"
+#include "timeout.h"
+#include "watch.h"
+#include <ccan/hash/hash.h>
+#include <ccan/structeq/structeq.h>
+
+const struct txwatch_output *txowatch_keyof(const struct txowatch *w)
+{
+	return &w->out;
+}
+
+size_t txo_hash(const struct txwatch_output *out)
+{
+	return hash(&out->txid, 1, out->index);
+}
+
+bool txowatch_eq(const struct txowatch *w, const struct txwatch_output *out)
+{
+	return structeq(&w->out.txid, &out->txid)
+		&& w->out.index == out->index;
+}
+
+static void destroy_txowatch(struct txowatch *w)
+{
+	txowatch_hash_del(&w->peer->state->txowatches, w);
+}
+
+/* Watch a txo. */
+static void insert_txo_watch(struct peer *peer,
+			     const struct sha256_double *txid,
+			     unsigned int txout,
+			     void (*cb)(struct peer *peer,
+					const struct bitcoin_tx *tx,
+					void *cbdata),
+			     void *cbdata)
+{
+	struct txowatch *w = tal(peer, struct txowatch);
+
+	w->out.txid = *txid;
+	w->out.index = txout;
+	w->peer = peer;
+	w->cb = cb;
+	w->cbdata = cbdata;
+
+	txowatch_hash_add(&w->peer->state->txowatches, w);
+	tal_add_destructor(w, destroy_txowatch);
+}
+
+const struct sha256_double *txwatch_keyof(const struct txwatch *w)
+{
+	return &w->txid;
+}
+
+size_t txid_hash(const struct sha256_double *txid)
+{
+	return hash(txid->sha.u.u8, sizeof(txid->sha.u.u8), 0);
+}
+
+bool txwatch_eq(const struct txwatch *w, const struct sha256_double *txid)
+{
+	return structeq(&w->txid, txid);
+}
+
+static void destroy_txwatch(struct txwatch *w)
+{
+	txwatch_hash_del(&w->state->txwatches, w);
+}
+
+static struct txwatch *insert_txwatch(const tal_t *ctx,
+				      struct lightningd_state *state,
+				      struct peer *peer,
+				      const struct sha256_double *txid,
+				      void (*cb)(struct peer *, int, void *),
+				      void *cbdata)
+{
+	struct txwatch *w;
+
+	/* We could have a null-watch on it because we saw it spend a TXO */
+	w = txwatch_hash_get(&state->txwatches, txid);
+	if (w) {
+		assert(!w->cb);
+		tal_free(w);
+	}
+
+	w = tal(ctx, struct txwatch);
+	w->depth = 0;
+	w->txid = *txid;
+	w->state = state;
+	w->peer = peer;
+	w->cb = cb;
+	w->cbdata = cbdata;
+
+	txwatch_hash_add(&w->state->txwatches, w);
+	tal_add_destructor(w, destroy_txwatch);
+
+	return w;
+}
+
+void add_anchor_watch_(struct peer *peer,
+		       const struct sha256_double *txid,
+		       unsigned int out,
+		       void (*anchor_cb)(struct peer *peer, int depth, void *),
+		       void (*spend_cb)(struct peer *peer,
+					const struct bitcoin_tx *, void *),
+		       void *cbdata)
+{
+	struct sha256 h;
+	struct ripemd160 redeemhash;
+	u8 *redeemscript;
+
+	insert_txwatch(peer, peer->state, peer, txid, anchor_cb, cbdata);
+	insert_txo_watch(peer, txid, out, spend_cb, cbdata);
+
+	redeemscript = bitcoin_redeem_2of2(peer, &peer->their_commitkey,
+					   &peer->our_commitkey);
+	sha256(&h, redeemscript, tal_count(redeemscript));
+	ripemd160(&redeemhash, h.u.u8, sizeof(h));
+	tal_free(redeemscript);
+
+	/* Telling bitcoind to watch the redeemhash address means
+	 * it'll tell is about the anchor itself (spend to that
+	 * address), and any commit txs (spend from that address).*/
+	bitcoind_watch_addr(peer->state, &redeemhash);
+}
+
+void add_commit_tx_watch_(struct peer *peer,
+			  const struct sha256_double *txid,
+			  void (*cb)(struct peer *peer, int depth, void *),
+			  void *cbdata)
+{
+	insert_txwatch(peer, peer->state, peer, txid, cb, cbdata);
+
+	/* We are already watching the anchor txo, so we don't need to
+	 * watch anything else. */
+}
+
+static void tx_watched_inputs(struct lightningd_state *state,
+			      const struct bitcoin_tx *tx, void *unused)
+{
+	size_t in;
+
+	for (in = 0; in < tx->input_count; in++) {
+		struct txwatch_output out;
+		struct txowatch *txow;
+
+		out.txid = tx->input[in].txid;
+		out.index = tx->input[in].index;
+
+		txow = txowatch_hash_get(&state->txowatches, &out);
+		if (txow)
+			txow->cb(txow->peer, tx, txow->cbdata);
+	}
+}
+
+static void watched_transaction(struct lightningd_state *state,
+				const struct sha256_double *txid,
+				int confirmations)
+{
+	struct txwatch *txw;
+
+	/* Are we watching this txid directly (or already reported)? */
+	txw = txwatch_hash_get(&state->txwatches, txid);
+	if (txw) {
+		if (confirmations != txw->depth) {
+			txw->depth = confirmations;
+			if (txw->cb)
+				txw->cb(txw->peer, txw->depth, txw->cbdata);
+		}
+		return;
+	}
+
+	/* Don't report about this txid twice. */
+	insert_txwatch(state, state, NULL, txid, NULL, NULL);
+
+	/* Maybe it spent an output we're watching? */
+	bitcoind_txid_lookup(state, txid, tx_watched_inputs, NULL);
+}
+
+static struct timeout watch_timeout;
+
+static void start_poll_transactions(struct lightningd_state *state)
+{
+	if (state->bitcoind_in_progress != 0) {
+		log_unusual(state->base_log,
+			    "Delaying start poll: %u commands in progress",
+			    state->bitcoind_in_progress);
+	} else
+		bitcoind_poll_transactions(state, watched_transaction);
+	refresh_timeout(state, &watch_timeout);
+}
+
+void setup_watch_timer(struct lightningd_state *state)
+{
+	init_timeout(&watch_timeout, 30, start_poll_transactions, state);
+	/* Run once immediately, in case there are issues. */
+	start_poll_transactions(state);
+}

daemon/watch.h

@@ -0,0 +1,98 @@
+#ifndef LIGHTNING_DAEMON_WATCH_H
+#define LIGHTNING_DAEMON_WATCH_H
+#include "config.h"
+#include "bitcoin/shadouble.h"
+#include <ccan/crypto/ripemd160/ripemd160.h>
+#include <ccan/htable/htable_type.h>
+#include <ccan/list/list.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/typesafe_cb/typesafe_cb.h>
+
+struct bitcoin_tx;
+struct lightningd_state;
+
+struct txwatch_output {
+	struct sha256_double txid;
+	unsigned int index;
+};
+
+/* Watching an output */
+struct txowatch {
+	/* Peer who owns us. */
+	struct peer *peer;
+	
+	/* Output to watch. */
+	struct txwatch_output out;
+
+	/* A new tx. */
+	void (*cb)(struct peer *peer,
+		   const struct bitcoin_tx *tx,
+		   void *cbdata);
+
+	void *cbdata;
+};
+
+const struct txwatch_output *txowatch_keyof(const struct txowatch *w);
+size_t txo_hash(const struct txwatch_output *out);
+bool txowatch_eq(const struct txowatch *w, const struct txwatch_output *out);
+
+HTABLE_DEFINE_TYPE(struct txowatch, txowatch_keyof, txo_hash, txowatch_eq,
+		   txowatch_hash);
+
+struct txwatch {
+	struct lightningd_state *state;
+
+	/* Peer who owns us. */
+	struct peer *peer;
+	
+	/* Transaction to watch. */
+	struct sha256_double txid;
+	int depth;
+
+	/* A new depth (-1 if conflicted) */
+	void (*cb)(struct peer *peer, int depth, void *cbdata);
+	void *cbdata;
+};
+
+const struct sha256_double *txwatch_keyof(const struct txwatch *w);
+size_t txid_hash(const struct sha256_double *txid);
+bool txwatch_eq(const struct txwatch *w, const struct sha256_double *txid);
+HTABLE_DEFINE_TYPE(struct txwatch, txwatch_keyof, txid_hash, txwatch_eq,
+		   txwatch_hash);
+
+
+void add_anchor_watch_(struct peer *peer,
+		       const struct sha256_double *txid,
+		       unsigned int out,
+		       void (*anchor_cb)(struct peer *peer, int depth, void *),
+		       void (*spend_cb)(struct peer *peer,
+					const struct bitcoin_tx *, void *),
+		       void *cbdata);
+
+#define add_anchor_watch(peer, txid, out, anchor_cb, spend_cb, cbdata)	\
+	add_anchor_watch_((peer), (txid), (out),			\
+			  typesafe_cb_preargs(void, void *,		\
+					      (anchor_cb), (cbdata),	\
+					      struct peer *,		\
+					      int depth),		\
+			  typesafe_cb_preargs(void, void *,		\
+					      (spend_cb), (cbdata),	\
+					      struct peer *,		\
+					      const struct bitcoin_tx *), \
+			  (cbdata))
+
+void add_commit_tx_watch_(struct peer *peer,
+			  const struct sha256_double *txid,
+			  void (*cb)(struct peer *peer, int depth, void *),
+			  void *cbdata);
+
+#define add_commit_tx_watch(peer, txid, cb, cbdata) \
+	add_commit_tx_watch_((peer), (txid),			  \
+			     typesafe_cb_preargs(void, void *,		\
+						 (cb), (cbdata),	\
+						 struct peer *,		\
+						 int depth),		\
+			     (cbdata))
+
+void setup_watch_timer(struct lightningd_state *state);
+#endif /* LIGHTNING_DAEMON_WATCH_H */