Fix insufficient UDP buffer size, add byte count log

The previous buffer size of 1024 meant that data would be dropped for
UDP packets larger than 1024 bytes, since each ReadFromUDP dequeues the
entire packet (no partial reads to be continue on the next call like in
TCP; i.e. TCP buffers bytes, UDP buffers whole packets).

Author: isobit

internal/schemes/udp/udp.go

@@ -38,7 +38,12 @@ func Listen(cfg ndog.ListenConfig) error {
 
 	streams := map[string]ndog.Stream{}
 
-	buf := make([]byte, 1024)
+	// ReadFromUDP dequeues an entire packet from the socket each time it's
+	// called, so the buffer needs to have enough space to read entire packets
+	// at once. 65535 bytes is the maximum possible packet size; ndog doesn't
+	// know anything about the expected inner protocol, so best to use this
+	// maximum size as the buffer size.
+	buf := make([]byte, 65535)
 	for {
 		nr, remoteAddr, err := conn.ReadFromUDP(buf)
 		if err != nil {
@@ -48,6 +53,7 @@ func Listen(cfg ndog.ListenConfig) error {
 			return err
 		}
 		remoteAddrStr := remoteAddr.String()
+		ndog.Logf(10, "%d bytes from %s", nr, remoteAddrStr)
 
 		var stream ndog.Stream
 		if existingStream, ok := streams[remoteAddrStr]; ok {