df-open: commands to update a PSBT or submit a signed PSBT

`openchannel_signed` and `openchannel_update` which allow a user to
continue a openchannel or kick off the completion of a openchannel.

`openchannel_update` should be called until it returns with
`commitments_secured`.

contrib/pyln-client/pyln/client/lightning.py

@@ -957,6 +957,36 @@ class LightningRpc(UnixDomainSocketRpc):
         }
         return self.call("pay", payload)
 
+    def openchannel_init(self, node_id, channel_amount, psbt, feerate=None, funding_feerate=None, announce=True, close_to=None, *args, **kwargs):
+        """Initiate an openchannel with a peer """
+        payload = {
+            "id": node_id,
+            "amount": channel_amount,
+            "initialpsbt": psbt,
+            "commitment_feerate": feerate,
+            "funding_feerate": funding_feerate,
+            "announce": announce,
+            "close_to": close_to,
+        }
+        return self.call("openchannel_init", payload)
+
+    def openchannel_signed(self, channel_id, signed_psbt, *args, **kwargs):
+        """ Send the funding transaction signatures to the peer, finish
+            the channel open """
+        payload = {
+            "channel_id": channel_id,
+            "signed_psbt": signed_psbt,
+        }
+        return self.call("openchannel_signed", payload)
+
+    def openchannel_update(self, channel_id, psbt, *args, **kwargs):
+        """Update an openchannel with a peer """
+        payload = {
+            "channel_id": channel_id,
+            "psbt": psbt,
+        }
+        return self.call("openchannel_update", payload)
+
     def paystatus(self, bolt11=None):
         """Detail status of attempts to pay {bolt11} or any."""
         payload = {

doc/Makefile

@@ -41,6 +41,8 @@ MANPAGES := doc/lightning-cli.1 \
 	doc/lightning-multiwithdraw.7 \
 	doc/lightning-newaddr.7 \
 	doc/lightning-openchannel_init.7 \
+	doc/lightning-openchannel_signed.7 \
+	doc/lightning-openchannel_update.7 \
 	doc/lightning-pay.7 \
 	doc/lightning-plugin.7 \
 	doc/lightning-reserveinputs.7 \
@@ -67,7 +69,7 @@ MANPAGES := doc/lightning-cli.1 \
 	doc/lightning-listnodes.7 \
 	doc/lightning-listconfigs.7 \
 	doc/lightning-help.7 \
-	doc/lightning-getlog.7 
+	doc/lightning-getlog.7
 
 doc-all: $(MANPAGES) doc/index.rst
 

doc/index.rst

@@ -69,6 +69,8 @@ c-lightning Documentation
    lightning-multiwithdraw <lightning-multiwithdraw.7.md>
    lightning-newaddr <lightning-newaddr.7.md>
    lightning-openchannel_init <lightning-openchannel_init.7.md>
+   lightning-openchannel_signed <lightning-openchannel_signed.7.md>
+   lightning-openchannel_update <lightning-openchannel_update.7.md>
    lightning-pay <lightning-pay.7.md>
    lightning-ping <lightning-ping.7.md>
    lightning-plugin <lightning-plugin.7.md>

doc/lightning-openchannel_signed.7

@@ -0,0 +1,68 @@
+.TH "LIGHTNING-OPENCHANNEL_SIGNED" "7" "" "" "lightning-openchannel_signed"
+.SH NAME
+lightning-openchannel_signed - Command to conclude a channel open
+.SH SYNOPSIS
+
+\fBopenchannel_signed\fR \fIid\fR \fIsigned_psbt\fR
+
+.SH DESCRIPTION
+
+\fBopenchannel_signed\fR is a low level RPC command which concludes a channel
+open with the specified peer\. It uses the v2 openchannel protocol, which
+allows for interactive transaction construction\.
+
+
+This command should be called after \fBopenchannel_update\fR returns
+\fIcommitments_secured\fR \fBtrue\fR\.
+
+
+This command will broadcast the finalized funding transaction,
+if we receive valid signatures from the peer\.
+
+
+\fIid\fR is the node id of the remote peer\.
+
+
+\fIsigned_psbt\fR is the PSBT returned from \fBopenchannel_update\fR (where
+\fIcommitments_secured\fR was true) with partial signatures or finalized
+witness stacks included for every input that we contributed to the
+PSBT\.
+
+.SH RETURN VALUE
+
+On success, returns the \fIchannel_id\fR for this channel; hex \fItx\fR of the
+published funding transaction; and \fItxid\fR of the funding transaction\.
+
+
+On error, the returned object will contain \fBcode\fR and \fBmessage\fR properties,
+with \fBcode\fR being one of the following:
+
+.RS
+.IP \[bu]
+-32602: If the given parameters are wrong\.
+.IP \[bu]
+-1: Catchall nonspecific error\.
+.IP \[bu]
+303: Funding transaction broadcast failed\.
+.IP \[bu]
+306: Unknown peer id\.
+.IP \[bu]
+309: PSBT missing required fields\.
+
+.RE
+.SH SEE ALSO
+
+lightning-openchannel_\fBupdate\fR(7), lightning-openchannel_\fBsigned\fR(7),
+lightning-fundchannel_\fBstart\fR(7), lightning-fundchannel_\fBcomplete\fR(7),
+\fBlightning-fundchannel\fR(7), \fBlightning-fundpsbt\fR(7), \fBlightning-utxopsbt\fR(7),
+\fBlightning-multifundchannel\fR(7)
+
+.SH AUTHOR
+
+@niftynei \fI<niftynei@gmail.com\fR> is mainly responsible\.
+
+.SH RESOURCES
+
+Main web site: \fIhttps://github.com/ElementsProject/lightning\fR
+
+\" SHA256STAMP:68fb78430a5ee3707fdb1324ba46373dd3dfaf325fe4e1bd3dcdc1589d80435c

doc/lightning-openchannel_signed.7.md

@@ -0,0 +1,60 @@
+lightning-openchannel\_signed -- Command to conclude a channel open
+===================================================================
+
+SYNOPSIS
+--------
+
+**openchannel_signed** *id* *signed_psbt*
+
+DESCRIPTION
+-----------
+
+`openchannel_signed` is a low level RPC command which concludes a channel
+open with the specified peer. It uses the v2 openchannel protocol, which
+allows for interactive transaction construction.
+
+This command should be called after `openchannel_update` returns
+*commitments_secured* `true`.
+
+This command will broadcast the finalized funding transaction,
+if we receive valid signatures from the peer.
+
+*id* is the node id of the remote peer.
+
+*signed_psbt* is the PSBT returned from `openchannel_update` (where
+*commitments_secured* was true) with partial signatures or finalized
+witness stacks included for every input that we contributed to the
+PSBT.
+
+RETURN VALUE
+------------
+
+On success, returns the *channel_id* for this channel; hex *tx* of the
+published funding transaction; and *txid* of the funding transaction.
+
+On error, the returned object will contain `code` and `message` properties,
+with `code` being one of the following:
+
+- -32602: If the given parameters are wrong.
+- -1: Catchall nonspecific error.
+- 303: Funding transaction broadcast failed.
+- 306: Unknown peer id.
+- 309: PSBT missing required fields.
+
+SEE ALSO
+--------
+
+lightning-openchannel\_update(7), lightning-openchannel\_signed(7),
+lightning-fundchannel\_start(7), lightning-fundchannel\_complete(7),
+lightning-fundchannel(7), lightning-fundpsbt(7), lightning-utxopsbt(7),
+lightning-multifundchannel(7)
+
+AUTHOR
+------
+
+@niftynei <<niftynei@gmail.com>> is mainly responsible.
+
+RESOURCES
+---------
+
+Main web site: <https://github.com/ElementsProject/lightning>

doc/lightning-openchannel_update.7

@@ -0,0 +1,66 @@
+.TH "LIGHTNING-OPENCHANNEL_UPDATE" "7" "" "" "lightning-openchannel_update"
+.SH NAME
+lightning-openchannel_update - Command to update a collab channel open
+.SH SYNOPSIS
+
+\fBopenchannel_update\fR \fIid\fR \fIpsbt\fR
+
+.SH DESCRIPTION
+
+\fBopenchannel_update\fR is a low level RPC command which continues an open
+channel with peer, as specified by \fIid\fR\. An updated  \fIpsbt\fR is passed in; any
+changes from the PSBT last returned (either from \fBopenchannel_init\fR or
+a previous call to \fBopenchannel_update\fR) will be communicated to the peer\.
+
+
+Must be called after \fBopenchannel_init\fR and before \fBopenchannel_signed\fR\.
+
+
+Must be called until \fIcommitments_secured\fR is returned as true, at which point
+\fBopenchannel_signed\fR should be called with a signed version of the PSBT
+returned by the last call to \fBopenchannel_update\fR\.
+
+
+\fIid\fR is the node id of the remote peer\.
+
+
+\fIpsbt\fR is the updated PSBT to be sent to the peer\. May be identical to
+the PSBT last returned by either \fBopenchannel_init\fR or \fBopenchannel_update\fR\.
+
+.SH RETURN VALUE
+
+On success, returns the \fIchannel_id\fR for this channel; an updated, potentially
+complete \fIpsbt\fR for this channel's funding transaction; and the flag
+\fIcommitments_secured\fR, which indicates the completeness of the returned \fIpsbt\fR\.
+If \fIcommitments_secured\fR is true, caller should proceed with signing the
+returned PSBT and calling \fBopenchannel_signed\fR to complete the channel open\.
+
+.RS
+.IP \[bu]
+-32602: If the given parameters are wrong\.
+.IP \[bu]
+-1: Catchall nonspecific error\.
+.IP \[bu]
+305: Peer is not connected\.
+.IP \[bu]
+306: Unknown peer id\.
+.IP \[bu]
+309: PSBT missing required fields
+
+.RE
+.SH SEE ALSO
+
+lightning-openchannel_\fBupdate\fR(7), lightning-openchannel_\fBsigned\fR(7),
+lightning-fundchannel_\fBstart\fR(7), lightning-fundchannel_\fBcomplete\fR(7),
+\fBlightning-fundchannel\fR(7), \fBlightning-fundpsbt\fR(7), \fBlightning-utxopsbt\fR(7),
+\fBlightning-multifundchannel\fR(7)
+
+.SH AUTHOR
+
+@niftynei \fI<niftynei@gmail.com\fR> is mainly responsible\.
+
+.SH RESOURCES
+
+Main web site: \fIhttps://github.com/ElementsProject/lightning\fR
+
+\" SHA256STAMP:dcf253e7b1658e71a9721fccee76a6bb07af7579ca4b0413428d2a1e8c9613bc

doc/lightning-openchannel_update.7.md

@@ -0,0 +1,59 @@
+lightning-openchannel\_update -- Command to update a collab channel open
+========================================================================
+
+SYNOPSIS
+--------
+
+**openchannel_update** *id* *psbt*
+
+DESCRIPTION
+-----------
+
+`openchannel_update` is a low level RPC command which continues an open
+channel with peer, as specified by *id*. An updated  *psbt* is passed in; any
+changes from the PSBT last returned (either from `openchannel_init` or
+a previous call to `openchannel_update`) will be communicated to the peer.
+
+Must be called after `openchannel_init` and before `openchannel_signed`.
+
+Must be called until *commitments_secured* is returned as true, at which point
+`openchannel_signed` should be called with a signed version of the PSBT
+returned by the last call to `openchannel_update`.
+
+*id* is the node id of the remote peer.
+
+*psbt* is the updated PSBT to be sent to the peer. May be identical to
+the PSBT last returned by either `openchannel_init` or `openchannel_update`.
+
+RETURN VALUE
+------------
+
+On success, returns the *channel_id* for this channel; an updated, potentially
+complete *psbt* for this channel's funding transaction; and the flag
+*commitments_secured*, which indicates the completeness of the returned *psbt*.
+If *commitments_secured* is true, caller should proceed with signing the
+returned PSBT and calling `openchannel_signed` to complete the channel open.
+
+- -32602: If the given parameters are wrong.
+- -1: Catchall nonspecific error.
+- 305: Peer is not connected.
+- 306: Unknown peer id.
+- 309: PSBT missing required fields
+
+SEE ALSO
+--------
+
+lightning-openchannel\_update(7), lightning-openchannel\_signed(7),
+lightning-fundchannel\_start(7), lightning-fundchannel\_complete(7),
+lightning-fundchannel(7), lightning-fundpsbt(7), lightning-utxopsbt(7),
+lightning-multifundchannel(7)
+
+AUTHOR
+------
+
+@niftynei <<niftynei@gmail.com>> is mainly responsible.
+
+RESOURCES
+---------
+
+Main web site: <https://github.com/ElementsProject/lightning>

lightningd/channel.h

@@ -3,6 +3,7 @@
 #include "config.h"
 #include <ccan/list/list.h>
 #include <common/channel_id.h>
+#include <common/per_peer_state.h>
 #include <lightningd/channel_state.h>
 #include <lightningd/peer_htlcs.h>
 #include <wallet/wallet.h>
@@ -146,6 +147,13 @@ struct channel {
 
 	/* Our position in the round-robin list.  */
 	u64 rr_number;
+
+	/* PSBT, for v2 channels. Saved until it's sent */
+	const struct wally_psbt *psbt;
+
+	/* Stashed pps, saved until channeld is started.
+	 * Needed only for v2 channel open flow */
+	struct per_peer_state *pps;
 };
 
 struct channel *new_channel(struct peer *peer, u64 dbid,

lightningd/dual_open_control.c

@@ -703,6 +703,7 @@ static void opener_psbt_changed(struct subd *dualopend,
 	json_add_bool(response, "commitments_secured", false);
 
 	uc->fc->inflight = true;
+	uc->fc->cmd = NULL;
 	was_pending(command_success(cmd, response));
 }
 
@@ -918,6 +919,7 @@ static void opener_commit_received(struct subd *dualopend,
 		goto failed;
 	}
 
+	channel->pps = tal_steal(channel, pps);
 	if (pbase)
 		wallet_penalty_base_add(ld->wallet, channel->dbid, pbase);
 
@@ -1004,6 +1006,128 @@ static void accepter_got_offer(struct subd *dualopend,
 	plugin_hook_call_openchannel2(dualopend->ld, payload);
 }
 
+static struct command_result *json_open_channel_signed(struct command *cmd,
+						       const char *buffer,
+						       const jsmntok_t *obj UNNEEDED,
+						       const jsmntok_t *params)
+{
+	struct wally_psbt *psbt;
+	struct node_id *id;
+	struct peer *peer;
+	struct channel *channel;
+	struct bitcoin_txid txid;
+
+	if (!param(cmd, buffer, params,
+		   p_req("id", param_node_id, &id),
+		   p_req("signed_psbt", param_psbt, &psbt),
+		   NULL))
+		return command_param_failed();
+
+	peer = peer_by_id(cmd->ld, id);
+	if (!peer)
+		return command_fail(cmd, FUNDING_UNKNOWN_PEER, "Unknown peer");
+
+	channel = peer_active_channel(peer);
+	if (!channel)
+		return command_fail(cmd, LIGHTNINGD,
+				    "Peer has no active channel");
+
+	if (!channel->pps)
+		return command_fail(cmd, LIGHTNINGD,
+				    "Missing per-peer-state for channel, "
+				    "are you in the right state to call "
+				    "this method?");
+
+	if (channel->psbt)
+		return command_fail(cmd, LIGHTNINGD,
+				    "Already have a finalized PSBT for "
+				    "this channel");
+
+	/* Verify that the psbt's txid matches that of the
+	 * funding txid for this channel */
+	psbt_txid(NULL, psbt, &txid, NULL);
+	if (!bitcoin_txid_eq(&txid, &channel->funding_txid))
+		return command_fail(cmd, FUNDING_PSBT_INVALID,
+				    "Txid for passed in PSBT does not match"
+				    " funding txid for channel. Expected %s, "
+				    "received %s",
+				    type_to_string(tmpctx, struct bitcoin_txid,
+						   &channel->funding_txid),
+				    type_to_string(tmpctx, struct bitcoin_txid,
+						   &txid));
+
+
+	/* Go ahead and try to finalize things, or what we can */
+	psbt_finalize(psbt);
+
+	/* Check that all of *our* outputs are finalized */
+	if (!psbt_side_finalized(cmd->ld->log, psbt, LOCAL))
+		return command_fail(cmd, FUNDING_PSBT_INVALID,
+				    "Local PSBT input(s) not finalized");
+
+	channel_watch_funding(cmd->ld, channel);
+
+	register_open_command(cmd->ld, cmd, channel);
+	peer_start_channeld(channel, channel->pps,
+			    NULL, psbt, false);
+	channel->pps = tal_free(channel->pps);
+
+	return command_still_pending(cmd);
+}
+
+static struct command_result *json_open_channel_update(struct command *cmd,
+						       const char *buffer,
+						       const jsmntok_t *obj UNNEEDED,
+						       const jsmntok_t *params)
+{
+	struct wally_psbt *psbt;
+	struct node_id *id;
+	struct peer *peer;
+	struct channel *channel;
+	struct channel_id chan_id_unused;
+	u8 *msg;
+
+	if (!param(cmd, buffer, params,
+		   p_req("id", param_node_id, &id),
+		   p_req("psbt", param_psbt, &psbt),
+		   NULL))
+		return command_param_failed();
+
+	peer = peer_by_id(cmd->ld, id);
+	if (!peer)
+		return command_fail(cmd, FUNDING_UNKNOWN_PEER, "Unknown peer");
+
+	channel = peer_active_channel(peer);
+	if (channel)
+		return command_fail(cmd, LIGHTNINGD, "Peer already %s",
+				    channel_state_name(channel));
+
+	if (!peer->uncommitted_channel)
+		return command_fail(cmd, FUNDING_PEER_NOT_CONNECTED,
+				    "Peer not connected");
+
+	if (!peer->uncommitted_channel->fc || !peer->uncommitted_channel->fc->inflight)
+		return command_fail(cmd, LIGHTNINGD, "No channel funding in progress");
+
+	if (peer->uncommitted_channel->fc->cmd)
+		return command_fail(cmd, LIGHTNINGD, "Channel funding in progress");
+
+	/* Add serials to PSBT */
+	psbt_add_serials(psbt, LOCAL);
+	if (!psbt_has_required_fields(psbt))
+		return command_fail(cmd, FUNDING_PSBT_INVALID,
+				    "PSBT is missing required fields %s",
+				    type_to_string(tmpctx, struct wally_psbt, psbt));
+
+	peer->uncommitted_channel->fc->cmd = cmd;
+
+	memset(&chan_id_unused, 0, sizeof(chan_id_unused));
+	msg = towire_dual_open_psbt_changed(NULL, &chan_id_unused, psbt);
+	subd_send_msg(peer->uncommitted_channel->open_daemon, take(msg));
+	return command_still_pending(cmd);
+}
+
+
 static struct command_result *json_open_channel_init(struct command *cmd,
 						     const char *buffer,
 						     const jsmntok_t *obj UNNEEDED,
@@ -1231,7 +1355,28 @@ static const struct json_command open_channel_init_command = {
 	"Init an open channel to {id} with {initialpsbt} for {amount} satoshis. "
 	"Returns updated {psbt} with (partial) contributions from peer"
 };
+
+static const struct json_command open_channel_update_command = {
+	"openchannel_update",
+	"channels",
+	json_open_channel_update,
+	"Update {channel_id} with {psbt}. "
+	"Returns updated {psbt} with (partial) contributions from peer. "
+	"If {commitments_secured} is true, next call should be to openchannel_signed"
+};
+
+static const struct json_command open_channel_signed_command = {
+	"openchannel_signed",
+	"channels",
+	json_open_channel_signed,
+	"Finish opening {channel_id} with {signed_psbt}. "
+};
+
+#if EXPERIMENTAL_FEATURES
 AUTODATA(json_command, &open_channel_init_command);
+AUTODATA(json_command, &open_channel_update_command);
+AUTODATA(json_command, &open_channel_signed_command);
+#endif /* EXPERIMENTAL_FEATURES */
 
 void peer_start_dualopend(struct peer *peer,
 			  struct per_peer_state *pps,

lightningd/opening_common.h

@@ -74,6 +74,10 @@ struct funding_channel {
 
 	/* Any commands trying to cancel us. */
 	struct command **cancels;
+
+	/* Place to stash the per-peer-state while we wait
+	 * for them to get back to us with signatures */
+	struct per_peer_state *pps;
 };
 
 struct uncommitted_channel *