From 5e9056a35641d06bacc0e73864cba6d659869f9c Mon Sep 17 00:00:00 2001
From: Percy Wegmann <percy@tailscale.com>
Date: Thu, 23 Jan 2025 09:08:54 -0600
Subject: [PATCH] derp: move Conn interface to derp.go

This interface is used both by the DERP client as well as the server.
Defining the interface in derp.go makes it clear that it is shared.

Updates tailscale/corp#26045

Signed-off-by: Percy Wegmann <percy@tailscale.com>
---
 derp/derp.go        | 12 ++++++++++++
 derp/derp_server.go | 12 ------------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/derp/derp.go b/derp/derp.go
index 6a7b3b735..65acd4321 100644
--- a/derp/derp.go
+++ b/derp/derp.go
@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"time"
 )
 
@@ -254,3 +255,14 @@ func writeFrame(bw *bufio.Writer, t frameType, b []byte) error {
 	}
 	return bw.Flush()
 }
+
+// Conn is the subset of the underlying net.Conn the DERP Server needs.
+// It is a defined type so that non-net connections can be used.
+type Conn interface {
+	io.WriteCloser
+	LocalAddr() net.Addr
+	// The *Deadline methods follow the semantics of net.Conn.
+	SetDeadline(time.Time) error
+	SetReadDeadline(time.Time) error
+	SetWriteDeadline(time.Time) error
+}
diff --git a/derp/derp_server.go b/derp/derp_server.go
index 983b5dc00..4b5cc2f78 100644
--- a/derp/derp_server.go
+++ b/derp/derp_server.go
@@ -23,7 +23,6 @@ import (
 	"math"
 	"math/big"
 	"math/rand/v2"
-	"net"
 	"net/http"
 	"net/netip"
 	"os"
@@ -341,17 +340,6 @@ type PacketForwarder interface {
 	String() string
 }
 
-// Conn is the subset of the underlying net.Conn the DERP Server needs.
-// It is a defined type so that non-net connections can be used.
-type Conn interface {
-	io.WriteCloser
-	LocalAddr() net.Addr
-	// The *Deadline methods follow the semantics of net.Conn.
-	SetDeadline(time.Time) error
-	SetReadDeadline(time.Time) error
-	SetWriteDeadline(time.Time) error
-}
-
 var packetsDropped = metrics.NewMultiLabelMap[dropReasonKindLabels](
 	"derp_packets_dropped",
 	"counter",