device: allow compiling with Go 1.15

Until we depend on Go 1.16 (which isn't released yet), alias our own
variable to the private member of the net package. This will allow an
easy find replace to make this go away when we eventually switch to
1.16.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

4 files changed, 19 insertions, 6 deletions

diff --git a/conn/conn_linux.go b/conn/conn_linux.go
index 642ad7d..c32ee0d 100644
--- a/conn/conn_linux.go
+++ b/conn/conn_linux.go
@@ -204,7 +204,7 @@ func (bind *nativeBind) ReceiveIPv6(buff []byte) (int, Endpoint, error) {
 
 	var end NativeEndpoint
 	if bind.sock6 == -1 {
-		return 0, nil, net.ErrClosed
+		return 0, nil, NetErrClosed
 	}
 	n, err := receive6(
 		bind.sock6,
@@ -220,7 +220,7 @@ func (bind *nativeBind) ReceiveIPv4(buff []byte) (int, Endpoint, error) {
 
 	var end NativeEndpoint
 	if bind.sock4 == -1 {
-		return 0, nil, net.ErrClosed
+		return 0, nil, NetErrClosed
 	}
 	n, err := receive4(
 		bind.sock4,
@@ -237,12 +237,12 @@ func (bind *nativeBind) Send(buff []byte, end Endpoint) error {
 	nend := end.(*NativeEndpoint)
 	if !nend.isV6 {
 		if bind.sock4 == -1 {
-			return net.ErrClosed
+			return NetErrClosed
 		}
 		return send4(bind.sock4, nend, buff)
 	} else {
 		if bind.sock6 == -1 {
-			return net.ErrClosed
+			return NetErrClosed
 		}
 		return send6(bind.sock6, nend, buff)
 	}
diff --git a/conn/net_err_closed.go b/conn/net_err_closed.go
new file mode 100644
index 0000000..e4dcfae
--- /dev/null
+++ b/conn/net_err_closed.go
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2021 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+import _ "unsafe"
+
+//TODO: replace this with net.ErrClosed for Go 1.16
+
+//go:linkname NetErrClosed internal/poll.ErrNetClosing
+var NetErrClosed error
diff --git a/device/receive.go b/device/receive.go
index 701e308..605303e 100644
--- a/device/receive.go
+++ b/device/receive.go
@@ -112,7 +112,7 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
 
 		if err != nil {
 			device.PutMessageBuffer(buffer)
-			if errors.Is(err, net.ErrClosed) {
+			if errors.Is(err, conn.NetErrClosed) {
 				return
 			}
 			device.log.Error.Printf("Failed to receive packet: %v", err)
diff --git a/go.mod b/go.mod
index 7b2c60f..10c0163 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module golang.zx2c4.com/wireguard
 
-go 1.16
+go 1.15
 
 require (
 	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad