plugins/fundchannel: make 'all' do the right thing for wumbo.

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

doc/lightning-fundchannel.7

@@ -27,11 +27,12 @@ for the channel\.
 
 \fIamount\fR is the amount in satoshis taken from the internal wallet to
 fund the channel\. The string \fIall\fR can be used to specify all available
-funds (or 16777215 satoshi if more is available)\. Otherwise, it is in
+funds (or 16777215 satoshi if more is available and large channels were not negotiated with the peer)\. Otherwise, it is in
 satoshi precision; it can be a whole number, a whole number ending in
 \fIsat\fR, a whole number ending in \fI000msat\fR, or a number with 1 to 8
 decimal places ending in \fIbtc\fR\. The value cannot be less than the dust
-limit, currently set to 546, nor more than 16777215 satoshi\.
+limit, currently set to 546, nor more than 16777215 satoshi (unless large
+channels were negotiated with the peer)\.
 
 
 \fIfeerate\fR is an optional feerate used for the opening transaction and as

doc/lightning-fundchannel.7.md

@@ -27,11 +27,12 @@ for the channel.
 
 *amount* is the amount in satoshis taken from the internal wallet to
 fund the channel. The string *all* can be used to specify all available
-funds (or 16777215 satoshi if more is available). Otherwise, it is in
+funds (or 16777215 satoshi if more is available and large channels were not negotiated with the peer). Otherwise, it is in
 satoshi precision; it can be a whole number, a whole number ending in
 *sat*, a whole number ending in *000msat*, or a number with 1 to 8
 decimal places ending in *btc*. The value cannot be less than the dust
-limit, currently set to 546, nor more than 16777215 satoshi.
+limit, currently set to 546, nor more than 16777215 satoshi (unless large
+channels were negotiated with the peer).
 
 *feerate* is an optional feerate used for the opening transaction and as
 initial feerate for commitment and HTLC transactions. It can be one of

plugins/fundchannel.c

@@ -5,6 +5,7 @@
 #include <ccan/tal/str/str.h>
 #include <common/addr.h>
 #include <common/amount.h>
+#include <common/features.h>
 #include <common/json_stream.h>
 #include <common/json_tok.h>
 #include <common/type_to_string.h>
@@ -25,6 +26,9 @@ struct funding_req {
 	bool funding_all;
 	struct amount_msat *push_msat;
 
+	/* Features offered by this peer. */
+	const u8 *features;
+
 	bool *announce_channel;
 	u32 *minconf;
 
@@ -329,7 +333,10 @@ static struct command_result *post_dryrun(struct command *cmd,
 		plugin_err(cmd->plugin, "Error creating placebo funding tx, funding_out not found. %s", hex);
 
 	/* Update funding to actual amount */
-	if (fr->funding_all && amount_sat_greater(funding, chainparams->max_funding))
+	if (fr->funding_all
+	    && !feature_negotiated(plugin_feature_set(cmd->plugin),
+				   fr->features, OPT_LARGE_CHANNELS)
+	    && amount_sat_greater(funding, chainparams->max_funding))
 		funding = chainparams->max_funding;
 
 	fr->funding_str = type_to_string(fr, struct amount_sat, &funding);
@@ -341,9 +348,21 @@ static struct command_result *exec_dryrun(struct command *cmd,
 					  const jsmntok_t *result,
 					  struct funding_req *fr)
 {
-	struct out_req *req = jsonrpc_request_start(cmd->plugin, cmd, "txprepare",
+	struct out_req *req;
-						    post_dryrun, forward_error,
+	const jsmntok_t *t;
-						    fr);
+
+	/* Stash features so we can wumbo. */
+	t = json_get_member(buf, result, "features");
+	if (!t)
+		plugin_err(cmd->plugin, "No features found in connect response?");
+	fr->features = json_tok_bin_from_hex(fr, buf, t);
+	if (!fr->features)
+		plugin_err(cmd->plugin, "Bad features '%.*s' in connect response?",
+			   t->end - t->start, buf + t->start);
+
+	req = jsonrpc_request_start(cmd->plugin, cmd, "txprepare",
+				    post_dryrun, forward_error,
+				    fr);
 
 	/* Now that we've tried connecting, we do a 'dry-run' of txprepare,
 	 * so we can get an accurate idea of the funding amount */

tests/test_connection.py

@@ -2264,3 +2264,17 @@ def test_wumbo_channels(node_factory, bitcoind):
     # Make sure l2 sees correct size.
     wait_for(lambda: [c['amount_msat'] for c in l2.rpc.listchannels(l1.get_channel_scid(l3))['channels']]
              == [Millisatoshi(str((1 << 24) - 1) + "sat")] * 2)
+
+    # Make sure 'all' works with wumbo peers.
+    l1.rpc.close(l2.info['id'])
+    bitcoind.generate_block(1, wait_for_mempool=1)
+    wait_for(lambda: l1.channel_state(l2) == 'ONCHAIN')
+
+    l1.rpc.connect(l2.info['id'], 'localhost', port=l2.port)
+    l1.rpc.fundchannel(l2.info['id'], 'all')
+    bitcoind.generate_block(1, wait_for_mempool=1)
+    wait_for(lambda: 'CHANNELD_NORMAL' in [c['state'] for c in only_one(l1.rpc.listpeers(l2.info['id'])['peers'])['channels']])
+
+    # Exact amount depends on fees, but it will be wumbo!
+    amount = [c['funding_msat'][l1.info['id']] for c in only_one(l1.rpc.listpeers(l2.info['id'])['peers'])['channels'] if c['state'] == 'CHANNELD_NORMAL'][0]
+    assert Millisatoshi(amount) > Millisatoshi(str((1 << 24) - 1) + "sat")