fdtrack: temporary hack for tracking file descriptor usage

Package fdtrack logs statistics about open file descriptors.
This should help identify the source of #1549.

p2p/metrics.go

@@ -34,7 +34,7 @@ var (
 // meteredConn is a wrapper around a network TCP connection that meters both the
 // inbound and outbound network traffic.
 type meteredConn struct {
-	*net.TCPConn // Network connection to wrap with metering
+	net.Conn
 }
 
 // newMeteredConn creates a new metered connection, also bumping the ingress or
@@ -45,13 +45,13 @@ func newMeteredConn(conn net.Conn, ingress bool) net.Conn {
 	} else {
 		egressConnectMeter.Mark(1)
 	}
-	return &meteredConn{conn.(*net.TCPConn)}
+	return &meteredConn{conn}
 }
 
 // Read delegates a network read to the underlying connection, bumping the ingress
 // traffic meter along the way.
 func (c *meteredConn) Read(b []byte) (n int, err error) {
-	n, err = c.TCPConn.Read(b)
+	n, err = c.Conn.Read(b)
 	ingressTrafficMeter.Mark(int64(n))
 	return
 }
@@ -59,7 +59,7 @@ func (c *meteredConn) Read(b []byte) (n int, err error) {
 // Write delegates a network write to the underlying connection, bumping the
 // egress traffic meter along the way.
 func (c *meteredConn) Write(b []byte) (n int, err error) {
-	n, err = c.TCPConn.Write(b)
+	n, err = c.Conn.Write(b)
 	egressTrafficMeter.Mark(int64(n))
 	return
 }