wallet: Hook into the hsm_funding_sig to extract change outputs

This is the step where we broadcast the transaction to the network and
a nice place to extract the change from the transaction.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

lightningd/peer_control.c

@@ -1378,6 +1378,7 @@ static void opening_got_hsm_funding_sig(struct funding_channel *fc,
 {
 	secp256k1_ecdsa_signature *sigs;
 	struct bitcoin_tx *tx = fc->funding_tx;
+	u64 change_satoshi;
 	size_t i;
 
 	if (!fromwire_hsmctl_sign_funding_reply(fc, resp, NULL, &sigs))
@@ -1407,6 +1408,9 @@ static void opening_got_hsm_funding_sig(struct funding_channel *fc,
 	watch_tx(fc->peer, fc->peer->ld->topology, fc->peer, tx,
 		 funding_lockin_cb, NULL);
 
+	/* Extract the change output and add it to the DB */
+	wallet_extract_owned_outputs(fc->peer->ld->wallet, tx, &change_satoshi);
+
 	/* FIXME: Remove arg from cb? */
 	watch_txo(fc->peer, fc->peer->ld->topology, fc->peer,
 		  fc->peer->funding_txid, fc->peer->funding_outnum,

tests/test_lightningd.py

@@ -1056,6 +1056,25 @@ class LightningDTests(BaseLightningDTests):
         c.execute('SELECT COUNT(*) FROM outputs WHERE status=2')
         assert(c.fetchone()[0] == 2)
 
+    def test_funding_change(self):
+        """Add some funds, fund a channel, and make sure we remember the change
+        """
+        l1, l2 = self.connect()
+        addr = l1.rpc.newaddr()['address']
+        txid = l1.bitcoin.rpc.sendtoaddress(addr, 0.1)
+        tx = l1.bitcoin.rpc.getrawtransaction(txid)
+        l1.rpc.addfunds(tx)
+        outputs = l1.db_query('SELECT value FROM outputs WHERE status=0;')
+        assert len(outputs) == 1 and outputs[0]['value'] == 10000000
+
+        l1.rpc.fundchannel(l2.info['id'], 1000000)
+        outputs = {r['status']: r['value'] for r in l1.db_query(
+            'SELECT status, SUM(value) AS value FROM outputs GROUP BY status;')}
+
+        # The 10m out is spent and we have a change output of 9m-fee
+        assert outputs[0] >   8990000
+        assert outputs[2] == 10000000
+
     def test_channel_persistence(self):
         # Start two nodes and open a channel (to remember)
         l1, l2 = self.connect()