Wrap MsgHeader in MsgHeaderWrapper for Known/Unknown msg type support (#2791)

* wrap MsgHeader in MsgHeaderWrapper for Known/Unknown msg type support.
* cleanup based on feedback

p2p/src/conn.rs

@@ -28,7 +28,10 @@ use std::{cmp, thread, time};
 
 use crate::core::ser;
 use crate::core::ser::FixedLength;
-use crate::msg::{read_body, read_header, read_item, write_to_buf, MsgHeader, Type};
+use crate::msg::{
+	read_body, read_discard, read_header, read_item, write_to_buf, MsgHeader, MsgHeaderWrapper,
+	Type,
+};
 use crate::types::Error;
 use crate::util::read_write::{read_exact, write_all};
 use crate::util::{RateCounter, RwLock};
@@ -251,27 +254,34 @@ fn poll<H>(
 			let mut retry_send = Err(());
 			loop {
 				// check the read end
-				if let Some(h) = try_break!(read_header(&mut reader, None)) {
-					let msg = Message::from_header(h, &mut reader);
+				match try_break!(read_header(&mut reader, None)) {
+					Some(MsgHeaderWrapper::Known(header)) => {
+						let msg = Message::from_header(header, &mut reader);
 
-					trace!(
-						"Received message header, type {:?}, len {}.",
-						msg.header.msg_type,
-						msg.header.msg_len
-					);
+						trace!(
+							"Received message header, type {:?}, len {}.",
+							msg.header.msg_type,
+							msg.header.msg_len
+						);
 
-					// Increase received bytes counter
-					let received = received_bytes.clone();
-					{
-						let mut received_bytes = received_bytes.write();
-						received_bytes.inc(MsgHeader::LEN as u64 + msg.header.msg_len);
+						// Increase received bytes counter
+						received_bytes
+							.write()
+							.inc(MsgHeader::LEN as u64 + msg.header.msg_len);
+
+						if let Some(Some(resp)) =
+							try_break!(handler.consume(msg, &mut writer, received_bytes.clone()))
+						{
+							try_break!(resp.write(sent_bytes.clone()));
+						}
 					}
+					Some(MsgHeaderWrapper::Unknown(msg_len)) => {
+						// Increase received bytes counter
+						received_bytes.write().inc(MsgHeader::LEN as u64 + msg_len);
 
-					if let Some(Some(resp)) =
-						try_break!(handler.consume(msg, &mut writer, received))
-					{
-						try_break!(resp.write(sent_bytes.clone()));
+						try_break!(read_discard(msg_len, &mut reader));
 					}
+					None => {}
 				}
 
 				// check the write end, use or_else so try_recv is lazily eval'd

p2p/src/msg.rs

@@ -82,6 +82,11 @@ fn max_block_size() -> u64 {
 	(global::max_block_weight() / consensus::BLOCK_OUTPUT_WEIGHT * 708) as u64
 }
 
+// Max msg size when msg type is unknown.
+fn default_max_msg_size() -> u64 {
+	max_block_size()
+}
+
 // Max msg size for each msg type.
 fn max_msg_size(msg_type: Type) -> u64 {
 	match msg_type {
@@ -120,24 +125,20 @@ fn magic() -> [u8; 2] {
 /// Read a header from the provided stream without blocking if the
 /// underlying stream is async. Typically headers will be polled for, so
 /// we do not want to block.
-pub fn read_header(stream: &mut dyn Read, msg_type: Option<Type>) -> Result<MsgHeader, Error> {
+///
+/// Note: We return a MsgHeaderWrapper here as we may encounter an unknown msg type.
+///
+pub fn read_header(
+	stream: &mut dyn Read,
+	msg_type: Option<Type>,
+) -> Result<MsgHeaderWrapper, Error> {
 	let mut head = vec![0u8; MsgHeader::LEN];
 	if Some(Type::Hand) == msg_type {
 		read_exact(stream, &mut head, time::Duration::from_millis(10), true)?;
 	} else {
 		read_exact(stream, &mut head, time::Duration::from_secs(10), false)?;
 	}
-	let header = ser::deserialize::<MsgHeader>(&mut &head[..])?;
-	let max_len = max_msg_size(header.msg_type);
-
-	// TODO 4x the limits for now to leave ourselves space to change things
-	if header.msg_len > max_len * 4 {
-		error!(
-			"Too large read {}, had {}, wanted {}.",
-			header.msg_type as u8, max_len, header.msg_len
-		);
-		return Err(Error::Serialization(ser::Error::TooLargeReadErr));
-	}
+	let header = ser::deserialize::<MsgHeaderWrapper>(&mut &head[..])?;
 	Ok(header)
 }
 
@@ -159,13 +160,28 @@ pub fn read_body<T: Readable>(h: &MsgHeader, stream: &mut dyn Read) -> Result<T,
 	ser::deserialize(&mut &body[..]).map_err(From::from)
 }
 
+/// Read (an unknown) message from the provided stream and discard it.
+pub fn read_discard(msg_len: u64, stream: &mut dyn Read) -> Result<(), Error> {
+	let mut buffer = vec![0u8; msg_len as usize];
+	read_exact(stream, &mut buffer, time::Duration::from_secs(20), true)?;
+	Ok(())
+}
+
 /// Reads a full message from the underlying stream.
 pub fn read_message<T: Readable>(stream: &mut dyn Read, msg_type: Type) -> Result<T, Error> {
-	let header = read_header(stream, Some(msg_type))?;
-	if header.msg_type != msg_type {
-		return Err(Error::BadMessage);
+	match read_header(stream, Some(msg_type))? {
+		MsgHeaderWrapper::Known(header) => {
+			if header.msg_type == msg_type {
+				read_body(&header, stream)
+			} else {
+				Err(Error::BadMessage)
+			}
+		}
+		MsgHeaderWrapper::Unknown(msg_len) => {
+			read_discard(msg_len, stream)?;
+			Err(Error::BadMessage)
+		}
 	}
-	read_body(&header, stream)
 }
 
 pub fn write_to_buf<T: Writeable>(msg: T, msg_type: Type) -> Result<Vec<u8>, Error> {
@@ -192,7 +208,19 @@ pub fn write_message<T: Writeable>(
 	Ok(())
 }
 
+/// A wrapper around a message header. If the header is for an unknown msg type
+/// then we will be unable to parse the msg itself (just a bunch of random bytes).
+/// But we need to know how many bytes to discard to discard the full message.
+#[derive(Clone)]
+pub enum MsgHeaderWrapper {
+	/// A "known" msg type with deserialized msg header.
+	Known(MsgHeader),
+	/// An unknown msg type with corresponding msg size in bytes.
+	Unknown(u64),
+}
+
 /// Header of any protocol message, used to identify incoming messages.
+#[derive(Clone)]
 pub struct MsgHeader {
 	magic: [u8; 2],
 	/// Type of the message.
@@ -213,7 +241,8 @@ impl MsgHeader {
 }
 
 impl FixedLength for MsgHeader {
-	const LEN: usize = 1 + 1 + 1 + 8;
+	// 2 magic bytes + 1 type byte + 8 bytes (msg_len)
+	const LEN: usize = 2 + 1 + 8;
 }
 
 impl Writeable for MsgHeader {
@@ -229,19 +258,49 @@ impl Writeable for MsgHeader {
 	}
 }
 
-impl Readable for MsgHeader {
-	fn read(reader: &mut dyn Reader) -> Result<MsgHeader, ser::Error> {
+impl Readable for MsgHeaderWrapper {
+	fn read(reader: &mut dyn Reader) -> Result<MsgHeaderWrapper, ser::Error> {
 		let m = magic();
 		reader.expect_u8(m[0])?;
 		reader.expect_u8(m[1])?;
-		let (t, len) = ser_multiread!(reader, read_u8, read_u64);
+
+		// Read the msg header.
+		// We do not yet know if the msg type is one we support locally.
+		let (t, msg_len) = ser_multiread!(reader, read_u8, read_u64);
+
+		// Attempt to convert the msg type byte into one of our known msg type enum variants.
+		// Check the msg_len while we are at it.
 		match Type::from_u8(t) {
-			Some(ty) => Ok(MsgHeader {
-				magic: m,
-				msg_type: ty,
-				msg_len: len,
-			}),
-			None => Err(ser::Error::CorruptedData),
+			Some(msg_type) => {
+				// TODO 4x the limits for now to leave ourselves space to change things.
+				let max_len = max_msg_size(msg_type) * 4;
+				if msg_len > max_len {
+					error!(
+						"Too large read {:?}, max_len: {}, msg_len: {}.",
+						msg_type, max_len, msg_len
+					);
+					return Err(ser::Error::TooLargeReadErr);
+				}
+
+				Ok(MsgHeaderWrapper::Known(MsgHeader {
+					magic: m,
+					msg_type,
+					msg_len,
+				}))
+			}
+			None => {
+				// Unknown msg type, but we still want to limit how big the msg is.
+				let max_len = default_max_msg_size() * 4;
+				if msg_len > max_len {
+					error!(
+						"Too large read (unknown msg type) {:?}, max_len: {}, msg_len: {}.",
+						t, max_len, msg_len
+					);
+					return Err(ser::Error::TooLargeReadErr);
+				}
+
+				Ok(MsgHeaderWrapper::Unknown(msg_len))
+			}
 		}
 	}
 }

p2p/src/protocol.rs

@@ -353,9 +353,8 @@ impl MessageHandler for Protocol {
 
 				Ok(None)
 			}
-
-			_ => {
-				debug!("unknown message type {:?}", msg.header.msg_type);
+			Type::Error | Type::Hand | Type::Shake => {
+				debug!("Received an unexpected msg: {:?}", msg.header.msg_type);
 				Ok(None)
 			}
 		}