splicing: Adds the features needed to enable collaborative splicing & resizing of active channels.

.github/workflows/ci.yaml

@@ -263,6 +263,15 @@ jobs:
             TEST_NETWORK: regtest
             DEVELOPER: 1
             EXPERIMENTAL_DUAL_FUND: 1
+          # And splicing!
+          - NAME: splicing
+            CFG: gcc-dev1
+            TEST_DB_PROVIDER: sqlite3
+            COMPILER: gcc
+            TEST_NETWORK: regtest
+            DEVELOPER: 1
+            EXPERIMENTAL_DUAL_FUND: 1
+            EXPERIMENTAL_SPLICING: 1
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -290,6 +299,7 @@ jobs:
           DEVELOPER: ${{ matrix.DEVELOPER }}
           COMPILER: ${{ matrix.COMPILER }}
           EXPERIMENTAL_DUAL_FUND: ${{ matrix.EXPERIMENTAL_DUAL_FUND }}
+          EXPERIMENTAL_SPLICING: ${{ matrix.EXPERIMENTAL_SPLICING }}
           COMPAT: 1
           CFG: ${{ matrix.CFG }}
           SLOW_MACHINE: 1
@@ -391,7 +401,7 @@ jobs:
           - NAME: ASan/UBSan (01/10)
             PYTEST_OPTS: --test-group=1  --test-group-count=10
           - NAME: ASan/UBSan (02/10)
-            PYTEST_OPTS: --test-group=2  --test-group-count=10
+            PYTEST_OPTS: --test-group=2  --test-group-count=10 -n 1
           - NAME: ASan/UBSan (03/10)
             PYTEST_OPTS: --test-group=3  --test-group-count=10
           - NAME: ASan/UBSan (04/10)

.msggen.json

@@ -182,6 +182,7 @@
         "ListpeerchannelsChannelsState": {
             "AWAITING_UNILATERAL": 6,
             "CHANNELD_AWAITING_LOCKIN": 1,
+            "CHANNELD_AWAITING_SPLICE": 11,
             "CHANNELD_NORMAL": 2,
             "CHANNELD_SHUTTING_DOWN": 3,
             "CLOSINGD_COMPLETE": 5,
@@ -1131,6 +1132,7 @@
             "ListPeerChannels.channels[].inflight[].funding_txid": 1,
             "ListPeerChannels.channels[].inflight[].our_funding_msat": 5,
             "ListPeerChannels.channels[].inflight[].scratch_txid": 6,
+            "ListPeerChannels.channels[].inflight[].splice_amount": 7,
             "ListPeerChannels.channels[].inflight[].total_funding_msat": 4
         },
         "ListpeerchannelsChannelsState_changes": {
@@ -1241,6 +1243,7 @@
             "ListPeers.peers[].channels[].inflight[].funding_txid": 1,
             "ListPeers.peers[].channels[].inflight[].our_funding_msat": 5,
             "ListPeers.peers[].channels[].inflight[].scratch_txid": 6,
+            "ListPeers.peers[].channels[].inflight[].splice_amount": 7,
             "ListPeers.peers[].channels[].inflight[].total_funding_msat": 4
         },
         "ListpeersPeersLog": {
@@ -4078,6 +4081,10 @@
             "added": "v23.02",
             "deprecated": false
         },
+        "ListPeerChannels.channels[].inflight[].splice_amount": {
+            "added": "v23.08",
+            "deprecated": false
+        },
         "ListPeerChannels.channels[].inflight[].total_funding_msat": {
             "added": "v23.02",
             "deprecated": false
@@ -4422,6 +4429,10 @@
             "added": "pre-v0.10.1",
             "deprecated": false
         },
+        "ListPeers.peers[].channels[].inflight[].splice_amount": {
+            "added": "v23.08",
+            "deprecated": false
+        },
         "ListPeers.peers[].channels[].inflight[].total_funding_msat": {
             "added": "pre-v0.10.1",
             "deprecated": false

bitcoin/psbt.c

@@ -95,7 +95,7 @@ bool psbt_is_finalized(const struct wally_psbt *psbt)
 }
 
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
-					struct wally_tx_input *input,
+					const struct wally_tx_input *input,
 				       	size_t insert_at)
 {
 	const u32 flags = WALLY_PSBT_FLAG_NON_FINAL; /* Skip script/witness */
@@ -322,6 +322,15 @@ void psbt_input_set_utxo(struct wally_psbt *psbt, size_t in,
 	assert(wally_err == WALLY_OK);
 }
 
+void psbt_input_set_outpoint(struct wally_psbt *psbt, size_t in,
+			     struct bitcoin_outpoint outpoint)
+{
+	assert(in < psbt->num_inputs);
+	psbt->inputs[in].index = outpoint.n;
+	memcpy(psbt->inputs[in].txhash, &outpoint.txid,
+	       sizeof(struct bitcoin_txid));
+}
+
 void psbt_input_set_witscript(struct wally_psbt *psbt, size_t in, const u8 *wscript)
 {
 	int wally_err;
@@ -446,6 +455,28 @@ struct amount_sat psbt_input_get_amount(const struct wally_psbt *psbt,
 	return val;
 }
 
+size_t psbt_input_get_weight(const struct wally_psbt *psbt,
+			     size_t in)
+{
+	size_t weight;
+	const struct wally_map_item *redeem_script;
+
+	redeem_script = wally_map_get_integer(&psbt->inputs[in].psbt_fields, /* PSBT_IN_REDEEM_SCRIPT */ 0x04);
+
+	/* txid + txout + sequence */
+	weight = (32 + 4 + 4) * 4;
+	if (redeem_script) {
+		weight +=
+			(redeem_script->value_len +
+				varint_size(redeem_script->value_len)) * 4;
+	} else {
+		/* zero scriptSig length */
+		weight += varint_size(0) * 4;
+	}
+
+	return weight;
+}
+
 struct amount_sat psbt_output_get_amount(const struct wally_psbt *psbt,
 					 size_t out)
 {
@@ -456,6 +487,13 @@ struct amount_sat psbt_output_get_amount(const struct wally_psbt *psbt,
 	return amount_asset_to_sat(&asset);
 }
 
+size_t psbt_output_get_weight(const struct wally_psbt *psbt,
+			      size_t outnum)
+{
+	return (8 /* amount*/ + varint_size(psbt->outputs[outnum].script_len) +
+		psbt->outputs[outnum].script_len) * 4;
+}
+
 static void add(u8 **key, const void *mem, size_t len)
 {
 	size_t oldlen = tal_count(*key);
@@ -733,6 +771,12 @@ const u8 *psbt_get_bytes(const tal_t *ctx, const struct wally_psbt *psbt,
 	return bytes;
 }
 
+bool validate_psbt(const struct wally_psbt *psbt)
+{
+	size_t len;
+	return wally_psbt_get_length(psbt, 0, &len) == WALLY_OK;
+}
+
 struct wally_psbt *psbt_from_bytes(const tal_t *ctx, const u8 *bytes,
 				   size_t byte_len)
 {

bitcoin/psbt.h

@@ -108,7 +108,7 @@ struct wally_tx *psbt_final_tx(const tal_t *ctx, const struct wally_psbt *psbt);
 u8 *psbt_make_key(const tal_t *ctx, u8 key_subtype, const u8 *key_data);
 
 struct wally_psbt_input *psbt_add_input(struct wally_psbt *psbt,
-					struct wally_tx_input *input,
+					const struct wally_tx_input *input,
 					size_t insert_at);
 
 /* One stop shop for adding an input + metadata to a PSBT */
@@ -127,6 +127,9 @@ void psbt_input_set_wit_utxo(struct wally_psbt *psbt, size_t in,
 void psbt_input_set_utxo(struct wally_psbt *psbt, size_t in,
 			 const struct wally_tx *prev_tx);
 
+void psbt_input_set_outpoint(struct wally_psbt *psbt, size_t in,
+			     struct bitcoin_outpoint outpoint);
+
 /* psbt_elements_input_set_asset - Set the asset/value fields for an
  * 				   Elements PSBT (PSET, technically */
 void psbt_elements_input_set_asset(struct wally_psbt *psbt, size_t in,
@@ -211,6 +214,10 @@ void psbt_output_set_unknown(const tal_t *ctx,
 struct amount_sat psbt_input_get_amount(const struct wally_psbt *psbt,
 					size_t in);
 
+/* psbt_input_get_weight - Calculate the tx weight for input index `in` */
+size_t psbt_input_get_weight(const struct wally_psbt *psbt,
+			     size_t in);
+
 /* psbt_output_get_amount - Returns the value of this output
  *
  * @psbt - psbt
@@ -219,6 +226,10 @@ struct amount_sat psbt_input_get_amount(const struct wally_psbt *psbt,
 struct amount_sat psbt_output_get_amount(const struct wally_psbt *psbt,
 					 size_t out);
 
+/* psbt_output_get_weight - Calculate the tx weight for output index `outnum` */
+size_t psbt_output_get_weight(const struct wally_psbt *psbt,
+			      size_t outnum);
+
 /* psbt_compute_fee - Returns value of fee for PSBT
  *
  * @psbt -psbt
@@ -266,6 +277,7 @@ struct wally_psbt *psbt_from_b64(const tal_t *ctx,
 char *psbt_to_b64(const tal_t *ctx, const struct wally_psbt *psbt);
 const u8 *psbt_get_bytes(const tal_t *ctx, const struct wally_psbt *psbt,
 			 size_t *bytes_written);
+bool validate_psbt(const struct wally_psbt *psbt);
 struct wally_psbt *psbt_from_bytes(const tal_t *ctx, const u8 *bytes,
 				   size_t byte_len);
 void towire_wally_psbt(u8 **pptr, const struct wally_psbt *psbt);

channeld/Makefile

@@ -13,6 +13,8 @@ CHANNELD_HEADERS :=			\
 CHANNELD_SRC := channeld/channeld.c	\
 	channeld/commit_tx.c			\
 	channeld/full_channel.c			\
+	channeld/splice.c			\
+	channeld/inflight.c			\
 	channeld/channeld_wiregen.c		\
 	channeld/watchtower.c
 
@@ -25,8 +27,13 @@ ALL_C_HEADERS += $(CHANNELD_HEADERS)
 ALL_PROGRAMS += lightningd/lightning_channeld
 
 # Here's what lightningd depends on
-LIGHTNINGD_CONTROL_HEADERS += channeld/channeld_wiregen.h
-LIGHTNINGD_CONTROL_OBJS += channeld/channeld_wiregen.o
+LIGHTNINGD_CONTROL_HEADERS += \
+	channeld/channeld_wiregen.h \
+	channeld/inflight.h
+LIGHTNINGD_CONTROL_OBJS +=  \
+	channeld/channeld_wiregen.o \
+	channeld/inflight.o
+
 
 # Common source we use.
 CHANNELD_COMMON_OBJS :=				\
@@ -53,6 +60,7 @@ CHANNELD_COMMON_OBJS :=				\
 	common/status_wiregen.o			\
 	common/gossip_store.o			\
 	common/hmac.o				\
+	common/interactivetx.o			\
 	common/htlc_state.o			\
 	common/htlc_trim.o			\
 	common/htlc_tx.o			\
@@ -73,6 +81,7 @@ CHANNELD_COMMON_OBJS :=				\
 	common/ping.o				\
 	common/psbt_keypath.o		\
 	common/psbt_open.o			\
+	common/psbt_internal.o			\
 	common/private_channel_announcement.o	\
 	common/pseudorand.o			\
 	common/read_peer_msg.o			\