Merge branch 'master' into gem-version-update

.circleci/config.yml

@@ -4,7 +4,7 @@ version: 2.1
 executors:
   go:
     docker:
-      - image: docker.mirror.hashicorp.services/circleci/golang:1.15
+      - image: docker.mirror.hashicorp.services/circleci/golang:1.16
     environment:
       - TEST_RESULTS: /tmp/test-results # path to where test results are saved
 

config.go

@@ -21,6 +21,17 @@ type Config struct {
 	// make a NetTransport using BindAddr and BindPort from this structure.
 	Transport Transport
 
+	// Label is an optional set of bytes to include on the outside of each
+	// packet and stream.
+	//
+	// If gossip encryption is enabled and this is set it is treated as GCM
+	// authenticated data.
+	Label string
+
+	// SkipInboundLabelCheck skips the check that inbound packets and gossip
+	// streams need to be label prefixed.
+	SkipInboundLabelCheck bool
+
 	// Configuration related to what address to bind to and ports to
 	// listen on. The port is used for both UDP and TCP gossip. It is
 	// assumed other nodes are running on this port, but they do not need

label.go

@@ -0,0 +1,178 @@
+package memberlist
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+)
+
+// General approach is to prefix all packets and streams with the same structure:
+//
+// magic type byte (244): uint8
+// length of label name:  uint8 (because labels can't be longer than 255 bytes)
+// label name:            []uint8
+
+// LabelMaxSize is the maximum length of a packet or stream label.
+const LabelMaxSize = 255
+
+// AddLabelHeaderToPacket prefixes outgoing packets with the correct header if
+// the label is not empty.
+func AddLabelHeaderToPacket(buf []byte, label string) ([]byte, error) {
+	if label == "" {
+		return buf, nil
+	}
+	if len(label) > LabelMaxSize {
+		return nil, fmt.Errorf("label %q is too long", label)
+	}
+
+	return makeLabelHeader(label, buf), nil
+}
+
+// RemoveLabelHeaderFromPacket removes any label header from the provided
+// packet and returns it along with the remaining packet contents.
+func RemoveLabelHeaderFromPacket(buf []byte) (newBuf []byte, label string, err error) {
+	if len(buf) == 0 {
+		return buf, "", nil // can't possibly be labeled
+	}
+
+	// [type:byte] [size:byte] [size bytes]
+
+	msgType := messageType(buf[0])
+	if msgType != hasLabelMsg {
+		return buf, "", nil
+	}
+
+	if len(buf) < 2 {
+		return nil, "", fmt.Errorf("cannot decode label; packet has been truncated")
+	}
+
+	size := int(buf[1])
+	if size < 1 {
+		return nil, "", fmt.Errorf("label header cannot be empty when present")
+	}
+
+	if len(buf) < 2+size {
+		return nil, "", fmt.Errorf("cannot decode label; packet has been truncated")
+	}
+
+	label = string(buf[2 : 2+size])
+	newBuf = buf[2+size:]
+
+	return newBuf, label, nil
+}
+
+// AddLabelHeaderToStream prefixes outgoing streams with the correct header if
+// the label is not empty.
+func AddLabelHeaderToStream(conn net.Conn, label string) error {
+	if label == "" {
+		return nil
+	}
+	if len(label) > LabelMaxSize {
+		return fmt.Errorf("label %q is too long", label)
+	}
+
+	header := makeLabelHeader(label, nil)
+
+	_, err := conn.Write(header)
+	return err
+}
+
+// RemoveLabelHeaderFromStream removes any label header from the beginning of
+// the stream if present and returns it along with an updated conn with that
+// header removed.
+//
+// Note that on error it is the caller's responsibility to close the
+// connection.
+func RemoveLabelHeaderFromStream(conn net.Conn) (net.Conn, string, error) {
+	br := bufio.NewReader(conn)
+
+	// First check for the type byte.
+	peeked, err := br.Peek(1)
+	if err != nil {
+		if err == io.EOF {
+			// It is safe to return the original net.Conn at this point because
+			// it never contained any data in the first place so we don't have
+			// to splice the buffer into the conn because both are empty.
+			return conn, "", nil
+		}
+		return nil, "", err
+	}
+
+	msgType := messageType(peeked[0])
+	if msgType != hasLabelMsg {
+		conn, err = newPeekedConnFromBufferedReader(conn, br, 0)
+		return conn, "", err
+	}
+
+	// We are guaranteed to get a size byte as well.
+	peeked, err = br.Peek(2)
+	if err != nil {
+		if err == io.EOF {
+			return nil, "", fmt.Errorf("cannot decode label; stream has been truncated")
+		}
+		return nil, "", err
+	}
+
+	size := int(peeked[1])
+	if size < 1 {
+		return nil, "", fmt.Errorf("label header cannot be empty when present")
+	}
+	// NOTE: we don't have to check this against LabelMaxSize because a byte
+	// already has a max value of 255.
+
+	// Once we know the size we can peek the label as well. Note that since we
+	// are using the default bufio.Reader size of 4096, the entire label header
+	// fits in the initial buffer fill so this should be free.
+	peeked, err = br.Peek(2 + size)
+	if err != nil {
+		if err == io.EOF {
+			return nil, "", fmt.Errorf("cannot decode label; stream has been truncated")
+		}
+		return nil, "", err
+	}
+
+	label := string(peeked[2 : 2+size])
+
+	conn, err = newPeekedConnFromBufferedReader(conn, br, 2+size)
+	if err != nil {
+		return nil, "", err
+	}
+
+	return conn, label, nil
+}
+
+// newPeekedConnFromBufferedReader will splice the buffer contents after the
+// offset into the provided net.Conn and return the result so that the rest of
+// the buffer contents are returned first when reading from the returned
+// peekedConn before moving on to the unbuffered conn contents.
+func newPeekedConnFromBufferedReader(conn net.Conn, br *bufio.Reader, offset int) (*peekedConn, error) {
+	// Extract any of the readahead buffer.
+	peeked, err := br.Peek(br.Buffered())
+	if err != nil {
+		return nil, err
+	}
+
+	return &peekedConn{
+		Peeked: peeked[offset:],
+		Conn:   conn,
+	}, nil
+}
+
+func makeLabelHeader(label string, rest []byte) []byte {
+	newBuf := make([]byte, 2, 2+len(label)+len(rest))
+	newBuf[0] = byte(hasLabelMsg)
+	newBuf[1] = byte(len(label))
+	newBuf = append(newBuf, []byte(label)...)
+	if len(rest) > 0 {
+		newBuf = append(newBuf, []byte(rest)...)
+	}
+	return newBuf
+}
+
+func labelOverhead(label string) int {
+	if label == "" {
+		return 0
+	}
+	return 2 + len(label)
+}