add rate limiter

internal/net/net.go

@@ -1,5 +1,28 @@
 package net
 
+import (
+	"net"
+	"syscall"
+)
+
+type SetBuffer interface {
+	SetReadBuffer(bytes int) error
+	SetWriteBuffer(bytes int) error
+}
+
+type SyscallConn interface {
+	SyscallConn() (syscall.RawConn, error)
+}
+
+type RemoteAddr interface {
+	RemoteAddr() net.Addr
+}
+
+// tcpraw.TCPConn
+type SetDSCP interface {
+	SetDSCP(int) error
+}
+
 func IsIPv4(address string) bool {
 	return address != "" && address[0] != ':' && address[0] != '['
 }