feerates: new command to inject/query fee estimates.

This is useful mainly in the case where bitcoind is not giving estimates,
but can also be used to bias results if you want.

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

CHANGELOG.md

@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Sending lightningd a SIGHUP will make it reopen its `log-file`, if any.
 - Protocol: `option_data_loss_protect` now supported to protect peers
   against being out-of-date.
+- JSON API: `feerates` command to inject fee estimates manually.
 
 ### Changed
 
@@ -42,6 +43,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - We now try to connect to all known addresses for a peer, not just
   the one given or the first one announced.
 - Crash logs are now placed one-per file like `crash.log.20180822233752`
+- We will no longer allow withdrawing funds or funding channels if we
+  do not have a fee estimate (eg. bitcoind not synced).
 
 ### Deprecated
 
@@ -56,7 +59,7 @@ changes.
   used to exist and set to `GOSSIPING` before we opened a channel).
   `connected` will indicate if we're connected, and the `channels`
   array indicates individual channel states (if any).
-- Options: `default-fee-rate` is no longer available.
+- Options: `default-fee-rate` is no longer available; use `feerates`.
 - Removed all Deprecated options from 0.6.
 
 ### Fixed

contrib/pylightning/lightning/lightning.py

@@ -448,3 +448,15 @@ class LightningRpc(UnixDomainSocketRpc):
             "id": peer_id,
         }
         return self.call("disconnect", payload)
+
+    def feerates(self, style, urgent=None, normal=None, slow=None):
+        """
+        Supply feerate estimates manually.
+        """
+        payload = {
+            "style": style,
+            "urgent": urgent,
+            "normal": normal,
+            "slow": slow
+        }
+        return self.call("feerates", payload)

lightningd/chaintopology.c

@@ -20,6 +20,7 @@
 #include <lightningd/channel_control.h>
 #include <lightningd/gossip_control.h>
 #include <lightningd/json.h>
+#include <lightningd/jsonrpc_errors.h>
 #include <lightningd/param.h>
 
 /* Mutual recursion via timer. */
@@ -388,6 +389,84 @@ static void start_fee_estimate(struct chain_topology *topo)
 			       update_feerates, topo);
 }
 
+static void json_feerates(struct command *cmd,
+			    const char *buffer, const jsmntok_t *params)
+{
+	struct chain_topology *topo = cmd->ld->topology;
+	struct json_result *response;
+	u32 *urgent, *normal, *slow, feerates[NUM_FEERATES];
+	bool missing;
+	const jsmntok_t *style;
+	bool bitcoind_style;
+
+	if (!param(cmd, buffer, params,
+		   p_req("style", json_tok_tok, &style),
+		   p_opt("urgent", json_tok_number, &urgent),
+		   p_opt("normal", json_tok_number, &normal),
+		   p_opt("slow", json_tok_number, &slow),
+		   NULL))
+		return;
+
+	/* update_feerates uses 0 as "don't know" */
+	feerates[FEERATE_URGENT] = urgent ? *urgent : 0;
+	feerates[FEERATE_NORMAL] = normal ? *normal : 0;
+	feerates[FEERATE_SLOW] = slow ? *slow : 0;
+
+	if (json_tok_streq(buffer, style, "sipa"))
+		bitcoind_style = false;
+	else if (json_tok_streq(buffer, style, "bitcoind")) {
+		/* Everyone uses satoshi per kbyte, but we use satoshi per ksipa
+		 * (don't round down to zero though)! */
+		for (size_t i = 0; i < ARRAY_SIZE(feerates); i++)
+			feerates[i] = (feerates[i] + 3) / 4;
+		bitcoind_style = true;
+	} else {
+		command_fail(cmd, JSONRPC2_INVALID_PARAMS, "invalid style");
+		return;
+	}
+
+	log_info(topo->log,
+		 "feerates: inserting feerates in sipa/kb %u/%u/%u",
+		 feerates[FEERATE_URGENT],
+		 feerates[FEERATE_NORMAL],
+		 feerates[FEERATE_SLOW]);
+
+	update_feerates(topo->bitcoind, feerates, topo);
+
+	missing = false;
+	for (size_t i = 0; i < ARRAY_SIZE(feerates); i++) {
+		feerates[i] = try_get_feerate(topo, i);
+		if (!feerates[i])
+			missing = true;
+		if (bitcoind_style)
+			feerates[i] *= 4;
+	}
+
+	response = new_json_result(cmd);
+	json_object_start(response, NULL);
+	json_object_start(response, bitcoind_style ? "bitcoind" : "sipa");
+	for (size_t i = 0; i < ARRAY_SIZE(feerates); i++) {
+		if (!feerates[i])
+			continue;
+		json_add_num(response, feerate_name(i), feerates[i]);
+	}
+	json_object_end(response);
+
+	if (missing)
+		json_add_string(response, "warning",
+				"Some fee estimates unavailable: bitcoind startup?");
+	json_object_end(response);
+
+	command_success(cmd, response);
+}
+
+static const struct json_command feerates_command = {
+	"feerates",
+	json_feerates,
+	"Add/query feerate estimates, either satoshi-per-kw ({style} sipa) or satoshi-per-kb ({style} bitcoind) for {urgent}, {normal} and {slow}."
+};
+AUTODATA(json_command, &feerates_command);
+
 static void next_updatefee_timer(struct chain_topology *topo)
 {
 	/* This takes care of its own lifetime. */

tests/test_misc.py

@@ -858,6 +858,46 @@ def test_ipv4_and_ipv6(node_factory):
         assert int(bind[0]['port']) == port
 
 
+def test_feerates(node_factory):
+    l1 = node_factory.get_node(options={'log-level': 'io'}, start=False)
+    l1.bitcoind_cmd_override(cmd='estimatesmartfee',
+                             failscript="""echo '{ "errors": [ "Insufficient data or no feerate found" ], "blocks": 0 }'; exit 0""")
+    l1.start()
+
+    # Query feerates (shouldn't give any!)
+    feerates = l1.rpc.feerates('sipa')
+    assert len(feerates['sipa']) == 0
+    assert feerates['warning'] == 'Some fee estimates unavailable: bitcoind startup?'
+    assert 'bitcoind' not in feerates
+
+    feerates = l1.rpc.feerates('bitcoind')
+    assert len(feerates['bitcoind']) == 0
+    assert feerates['warning'] == 'Some fee estimates unavailable: bitcoind startup?'
+    assert 'sipa' not in feerates
+
+    # Now try setting them, one at a time.
+    feerates = l1.rpc.feerates('sipa', 15000)
+    assert len(feerates['sipa']) == 1
+    assert feerates['sipa']['urgent'] == 15000
+    assert feerates['warning'] == 'Some fee estimates unavailable: bitcoind startup?'
+    assert 'bitcoind' not in feerates
+
+    feerates = l1.rpc.feerates('bitcoind', normal=25000)
+    assert len(feerates['bitcoind']) == 2
+    assert feerates['bitcoind']['urgent'] == 15000 * 4
+    assert feerates['bitcoind']['normal'] == 25000
+    assert feerates['warning'] == 'Some fee estimates unavailable: bitcoind startup?'
+    assert 'sipa' not in feerates
+
+    feerates = l1.rpc.feerates('sipa', None, None, 5000)
+    assert len(feerates['sipa']) == 3
+    assert feerates['sipa']['urgent'] == 15000
+    assert feerates['sipa']['normal'] == 25000 // 4
+    assert feerates['sipa']['slow'] == 5000
+    assert 'warning' not in feerates
+    assert 'bitcoind' not in feerates
+
+
 def test_logging(node_factory):
     # Since we redirect, node.start() will fail: do manually.
     l1 = node_factory.get_node(options={'log-file': 'logfile'}, may_fail=True, start=False)