commit 2f4ad6437420a56d016b5d1ac5eb61c2a7234254
from: Oliver Lowe <o@olowe.co>
date: Sat Nov 20 00:19:50 2021 UTC

Use the message length field to only read that much

Using io.ReadAll doesn't work properly. The socket has a queue that
may be entirely drained by this call, which means we could
accidentally read a bit of the next message if there is one in the
queue.

commit - c245affd0ab63714b15dc1e6bd67307059e8da4f
commit + 2f4ad6437420a56d016b5d1ac5eb61c2a7234254
blob - 96f445fbb2f41e17da146512daa63c93863a8556
blob + f44e64273879b3325edd87fc38bac547e6fe57b0
--- dns.go
+++ dns.go
@@ -87,9 +87,18 @@ func dnsStreamExchange(b []byte, conn net.Conn) ([]byt
 	if _, err := conn.Write(m); err != nil {
 		return nil, err
 	}
-	buf, err := io.ReadAll(conn)
+
+	b = make([]byte, 1280)
+	if _, err := io.ReadFull(conn, b[:2]); err != nil {
+		return nil, fmt.Errorf("read length: %w", err)
+	}
+	l := int(b[0])<<8 | int(b[1])
+	if l > len(b) {
+		b = make([]byte, l)
+	}
+	n, err := io.ReadFull(conn, b[:l])
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("read after length: %w", err)
 	}
-	return buf[2:], nil
+	return b[:n], nil
 }