Drop tokio/macros dependency in lightning-net-tokio, fix MSRV

Cargo.toml

@@ -14,6 +14,7 @@ exclude = [
     "lightning-custom-message",
     "lightning-transaction-sync",
     "no-std-check",
+    "msrv-no-dev-deps-check",
     "bench",
 ]
 

ci/ci-tests.sh

@@ -4,18 +4,33 @@ set -eox pipefail
 RUSTC_MINOR_VERSION=$(rustc --version | awk '{ split($2,a,"."); print a[2] }')
 HOST_PLATFORM="$(rustc --version --verbose | grep "host:" | awk '{ print $2 }')"
 
-# Tokio MSRV on versions 1.17 through 1.26 is rustc 1.49. Above 1.26 MSRV is 1.56.
-[ "$RUSTC_MINOR_VERSION" -lt 49 ] && cargo update -p tokio --precise "1.14.1" --verbose
-[[ "$RUSTC_MINOR_VERSION" -gt 48  &&  "$RUSTC_MINOR_VERSION" -lt 56 ]] && cargo update -p tokio --precise "1.25.1" --verbose
+# Some crates require pinning to meet our MSRV even for our downstream users,
+# which we do here.
+# Further crates which appear only as dev-dependencies are pinned further down.
+function PIN_RELEASE_DEPS {
+	# Tokio MSRV on versions 1.17 through 1.26 is rustc 1.49. Above 1.26 MSRV is 1.56.
+	[ "$RUSTC_MINOR_VERSION" -lt 49 ] && cargo update -p tokio --precise "1.14.1" --verbose
+	[[ "$RUSTC_MINOR_VERSION" -gt 48  &&  "$RUSTC_MINOR_VERSION" -lt 56 ]] && cargo update -p tokio --precise "1.25.1" --verbose
 
-# Sadly the log crate is always a dependency of tokio until 1.20, and has no reasonable MSRV guarantees
-[ "$RUSTC_MINOR_VERSION" -lt 49 ] && cargo update -p log --precise "0.4.18" --verbose
+	# Sadly the log crate is always a dependency of tokio until 1.20, and has no reasonable MSRV guarantees
+	[ "$RUSTC_MINOR_VERSION" -lt 49 ] && cargo update -p log --precise "0.4.18" --verbose
+
+	# The serde_json crate switched to Rust edition 2021 starting with v1.0.101, i.e., has MSRV of 1.56
+	[ "$RUSTC_MINOR_VERSION" -lt 56 ] && cargo update -p serde_json --precise "1.0.100" --verbose
+
+	return 0 # Don't fail the script if our rustc is higher than the last check
+}
+
+PIN_RELEASE_DEPS # pin the release dependencies in our main workspace
 
 # The addr2line v0.20 crate (a dependency of `backtrace` starting with 0.3.68) relies on 1.55+
 [ "$RUSTC_MINOR_VERSION" -lt 55 ] && cargo update -p backtrace --precise "0.3.67" --verbose
 
-# The serde_json crate switched to Rust edition 2021 starting with v1.0.101, i.e., has MSRV of 1.56
-[ "$RUSTC_MINOR_VERSION" -lt 56 ] && cargo update -p serde_json --precise "1.0.100" --verbose
+# The quote crate switched to Rust edition 2021 starting with v1.0.31, i.e., has MSRV of 1.56
+[ "$RUSTC_MINOR_VERSION" -lt 56 ] && cargo update -p quote --precise "1.0.30" --verbose
+
+# The proc-macro2 crate switched to Rust edition 2021 starting with v1.0.66, i.e., has MSRV of 1.56
+[ "$RUSTC_MINOR_VERSION" -lt 56 ] && cargo update -p proc-macro2 --precise "1.0.65" --verbose
 
 [ "$LDK_COVERAGE_BUILD" != "" ] && export RUSTFLAGS="-C link-dead-code"
 
@@ -62,7 +77,18 @@ popd
 echo -e "\n\nTesting no-std build on a downstream no-std crate"
 # check no-std compatibility across dependencies
 pushd no-std-check
-cargo check --verbose --color always --features lightning-transaction-sync
+if [[ $RUSTC_MINOR_VERSION -gt 67 ]]; then
+	# lightning-transaction-sync's MSRV is 1.67
+	cargo check --verbose --color always --features lightning-transaction-sync
+else
+	cargo check --verbose --color always
+fi
+popd
+
+# Test that we can build downstream code with only the "release pins".
+pushd msrv-no-dev-deps-check
+PIN_RELEASE_DEPS
+cargo check
 popd
 
 if [ -f "$(which arm-none-eabi-gcc)" ]; then

lightning-net-tokio/Cargo.toml

@@ -17,7 +17,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 [dependencies]
 bitcoin = "0.29.0"
 lightning = { version = "0.0.116-rc1", path = "../lightning" }
-tokio = { version = "1.0", features = [ "io-util", "macros", "rt", "sync", "net", "time" ] }
+tokio = { version = "1.0", features = [ "io-util", "rt", "sync", "net", "time" ] }
 
 [dev-dependencies]
 tokio = { version = "1.14", features = [ "io-util", "macros", "rt", "rt-multi-thread", "sync", "net", "time" ] }

lightning-net-tokio/src/lib.rs

@@ -42,16 +42,79 @@ use lightning::ln::peer_handler::APeerManager;
 use lightning::ln::msgs::NetAddress;
 
 use std::ops::Deref;
-use std::task;
+use std::task::{self, Poll};
+use std::future::Future;
 use std::net::SocketAddr;
 use std::net::TcpStream as StdTcpStream;
 use std::sync::{Arc, Mutex};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::time::Duration;
+use std::pin::Pin;
 use std::hash::Hash;
 
 static ID_COUNTER: AtomicU64 = AtomicU64::new(0);
 
+// We only need to select over multiple futures in one place, and taking on the full `tokio/macros`
+// dependency tree in order to do so (which has broken our MSRV before) is excessive. Instead, we
+// define a trivial two- and three- select macro with the specific types we need and just use that.
+
+pub(crate) enum SelectorOutput {
+	A(Option<()>), B(Option<()>), C(tokio::io::Result<usize>),
+}
+
+pub(crate) struct TwoSelector<
+	A: Future<Output=Option<()>> + Unpin, B: Future<Output=Option<()>> + Unpin
+> {
+	pub a: A,
+	pub b: B,
+}
+
+impl<
+	A: Future<Output=Option<()>> + Unpin, B: Future<Output=Option<()>> + Unpin
+> Future for TwoSelector<A, B> {
+	type Output = SelectorOutput;
+	fn poll(mut self: Pin<&mut Self>, ctx: &mut task::Context<'_>) -> Poll<SelectorOutput> {
+		match Pin::new(&mut self.a).poll(ctx) {
+			Poll::Ready(res) => { return Poll::Ready(SelectorOutput::A(res)); },
+			Poll::Pending => {},
+		}
+		match Pin::new(&mut self.b).poll(ctx) {
+			Poll::Ready(res) => { return Poll::Ready(SelectorOutput::B(res)); },
+			Poll::Pending => {},
+		}
+		Poll::Pending
+	}
+}
+
+pub(crate) struct ThreeSelector<
+	A: Future<Output=Option<()>> + Unpin, B: Future<Output=Option<()>> + Unpin, C: Future<Output=tokio::io::Result<usize>> + Unpin
+> {
+	pub a: A,
+	pub b: B,
+	pub c: C,
+}
+
+impl<
+	A: Future<Output=Option<()>> + Unpin, B: Future<Output=Option<()>> + Unpin, C: Future<Output=tokio::io::Result<usize>> + Unpin
+> Future for ThreeSelector<A, B, C> {
+	type Output = SelectorOutput;
+	fn poll(mut self: Pin<&mut Self>, ctx: &mut task::Context<'_>) -> Poll<SelectorOutput> {
+		match Pin::new(&mut self.a).poll(ctx) {
+			Poll::Ready(res) => { return Poll::Ready(SelectorOutput::A(res)); },
+			Poll::Pending => {},
+		}
+		match Pin::new(&mut self.b).poll(ctx) {
+			Poll::Ready(res) => { return Poll::Ready(SelectorOutput::B(res)); },
+			Poll::Pending => {},
+		}
+		match Pin::new(&mut self.c).poll(ctx) {
+			Poll::Ready(res) => { return Poll::Ready(SelectorOutput::C(res)); },
+			Poll::Pending => {},
+		}
+		Poll::Pending
+	}
+}
+
 /// Connection contains all our internal state for a connection - we hold a reference to the
 /// Connection object (in an Arc<Mutex<>>) in each SocketDescriptor we create as well as in the
 /// read future (which is returned by schedule_read).
@@ -127,29 +190,44 @@ impl Connection {
 				}
 				us_lock.read_paused
 			};
-			tokio::select! {
-				v = write_avail_receiver.recv() => {
+			// TODO: Drop the Box'ing of the futures once Rust has pin-on-stack support.
+			let select_result = if read_paused {
+				TwoSelector {
+					a: Box::pin(write_avail_receiver.recv()),
+					b: Box::pin(read_wake_receiver.recv()),
+				}.await
+			} else {
+				ThreeSelector {
+					a: Box::pin(write_avail_receiver.recv()),
+					b: Box::pin(read_wake_receiver.recv()),
+					c: Box::pin(reader.read(&mut buf)),
+				}.await
+			};
+			match select_result {
+				SelectorOutput::A(v) => {
 					assert!(v.is_some()); // We can't have dropped the sending end, its in the us Arc!
 					if peer_manager.as_ref().write_buffer_space_avail(&mut our_descriptor).is_err() {
 						break Disconnect::CloseConnection;
 					}
 				},
-				_ = read_wake_receiver.recv() => {},
-				read = reader.read(&mut buf), if !read_paused => match read {
-					Ok(0) => break Disconnect::PeerDisconnected,
-					Ok(len) => {
-						let read_res = peer_manager.as_ref().read_event(&mut our_descriptor, &buf[0..len]);
-						let mut us_lock = us.lock().unwrap();
-						match read_res {
-							Ok(pause_read) => {
-								if pause_read {
-									us_lock.read_paused = true;
-								}
-							},
-							Err(_) => break Disconnect::CloseConnection,
-						}
-					},
-					Err(_) => break Disconnect::PeerDisconnected,
+				SelectorOutput::B(_) => {},
+				SelectorOutput::C(read) => {
+					match read {
+						Ok(0) => break Disconnect::PeerDisconnected,
+						Ok(len) => {
+							let read_res = peer_manager.as_ref().read_event(&mut our_descriptor, &buf[0..len]);
+							let mut us_lock = us.lock().unwrap();
+							match read_res {
+								Ok(pause_read) => {
+									if pause_read {
+										us_lock.read_paused = true;
+									}
+								},
+								Err(_) => break Disconnect::CloseConnection,
+							}
+						},
+						Err(_) => break Disconnect::PeerDisconnected,
+					}
 				},
 			}
 			let _ = event_waker.try_send(());

msrv-no-dev-deps-check/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "msrv-check"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+lightning = { path = "../lightning" }
+lightning-block-sync = { path = "../lightning-block-sync", features = [ "rest-client", "rpc-client" ] }
+lightning-invoice = { path = "../lightning-invoice" }
+lightning-net-tokio = { path = "../lightning-net-tokio" }
+lightning-persister = { path = "../lightning-persister" }
+lightning-background-processor = { path = "../lightning-background-processor", features = ["futures"] }
+lightning-rapid-gossip-sync = { path = "../lightning-rapid-gossip-sync" }