From 4d5819183e218e040fa0a73df560b4a4a9a768d7 Mon Sep 17 00:00:00 2001
From: Michael Zeltner <m@niij.org>
Date: Wed, 17 Jul 2019 23:04:01 +0200
Subject: [PATCH] tun: openbsd: don't change MTU when it's already the expected
 size

Allows for running wireguard-go as non-root user.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 tun/tun_openbsd.go | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/tun/tun_openbsd.go b/tun/tun_openbsd.go
index 1e6191f..bbc0432 100644
--- a/tun/tun_openbsd.go
+++ b/tun/tun_openbsd.go
@@ -173,10 +173,13 @@ func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
 
 	go tun.routineRouteListener(tunIfindex)
 
-	err = tun.setMTU(mtu)
-	if err != nil {
-		tun.Close()
-		return nil, err
+	currentMTU, err := tun.MTU()
+	if err != nil || currentMTU != mtu {
+		err = tun.setMTU(mtu)
+		if err != nil {
+			tun.Close()
+			return nil, err
+		}
 	}
 
 	return tun, nil