From 937f6ba95528d35c570c101ffa5a2d6b90f4e3fa Mon Sep 17 00:00:00 2001
From: Matthew Ellison <matt@arroyonetworks.com>
Date: Tue, 23 May 2017 14:58:32 -0400
Subject: [PATCH] linux: Refactors Owner/Group to DevicePermissions

---
 params_linux.go   | 30 +++++++++++++++++-------------
 syscalls_linux.go | 14 +++++++-------
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/params_linux.go b/params_linux.go
index a0533f7..41203f6 100644
--- a/params_linux.go
+++ b/params_linux.go
@@ -2,6 +2,18 @@
 
 package water
 
+type DevicePermissions struct {
+	// ID of the user which will be granted ownership of the device.
+	// If set to a negative value, the owner value will not be changed.
+	// By default, Linux sets the owner to -1, which allows any user.
+	Owner uint
+
+	// ID of the group which will be granted access to the device.
+	// If set to a negative value, the group value will not be changed.
+	// By default, Linux sets the group to -1, which allows any group.
+	Group uint
+}
+
 // PlatformSpecificParams defines parameters in Config that are specific to
 // Linux. A zero-value of such type is valid, yielding an interface
 // with OS defined name.
@@ -15,20 +27,12 @@ type PlatformSpecificParams struct {
 	// Enable or disable persistence mode for the interface device.
 	Persist bool
 
-	// ID of the user which will be granted ownership of the device.
-	// If set to a negative value, the owner value will not be changed.
-	// By default, Linux sets the owner to -1, which allows any user.
-	Owner int
-
-	// ID of the group which will be granted access to the device.
-	// If set to a negative value, the group value will not be changed.
-	// By default, Linux sets the group to -1, which allows any group.
-	Group int
+	// Owner and Group permissions for the device.
+	// A zero-value of this field, i.e. nil, indicates that no changes to owner
+	// or group will be made.
+	Permissions *DevicePermissions
 }
 
 func defaultPlatformSpecificParams() PlatformSpecificParams {
-	return PlatformSpecificParams{
-		Owner: -1,
-		Group: -1,
-	}
+	return PlatformSpecificParams{}
 }
diff --git a/syscalls_linux.go b/syscalls_linux.go
index 4d97fd4..50a945c 100644
--- a/syscalls_linux.go
+++ b/syscalls_linux.go
@@ -81,16 +81,16 @@ func createInterface(fd uintptr, ifName string, flags uint16) (createdIFName str
 
 func setDeviceOptions(fd uintptr, config Config) (err error) {
 
-	// Set Device Owner
-	if config.Owner >= 0 {
-		if err = ioctl(fd, syscall.TUNSETOWNER, uintptr(config.Owner)); err != nil {
+	// Device Permissions
+	if config.Permissions != nil {
+
+		// Set Owner
+		if err = ioctl(fd, syscall.TUNSETOWNER, uintptr(config.Permissions.Owner)); err != nil {
 			return
 		}
-	}
 
-	// Set Device Group
-	if config.Group >= 0 {
-		if err = ioctl(fd, syscall.TUNSETGROUP, uintptr(config.Group)); err != nil {
+		// Set Group
+		if err = ioctl(fd, syscall.TUNSETGROUP, uintptr(config.Permissions.Group)); err != nil {
 			return
 		}
 	}