chore(all): make code compilable for other platforms than Linux

Author: qdm12

cmd/gluetun/main.go

@@ -581,7 +581,7 @@ type Linker interface {
 	LinkDel(link netlink.Link) (err error)
 	LinkSetUp(link netlink.Link) (linkIndex int, err error)
 	LinkSetDown(link netlink.Link) (err error)
-	LinkSetMTU(link netlink.Link, mtu int) error
+	LinkSetMTU(link netlink.Link, mtu uint32) error
 }
 
 type clier interface {

internal/netlink/address.go

@@ -1,5 +1,3 @@
-//go:build linux || darwin
-
 package netlink
 
 import (

internal/netlink/address_unspecified.go

@@ -4,12 +4,6 @@ import (
 	"fmt"
 )
 
-const (
-	FamilyAll = 0
-	FamilyV4  = 2
-	FamilyV6  = 10
-)
-
 func FamilyToString(family int) string {
 	switch family {
 	case FamilyAll:

internal/netlink/family.go

@@ -0,0 +1,9 @@
+package netlink
+
+import "golang.org/x/sys/unix"
+
+const (
+	FamilyAll = unix.AF_UNSPEC
+	FamilyV4  = unix.AF_INET
+	FamilyV6  = unix.AF_INET6
+)

internal/netlink/family_linux.go

@@ -1,5 +1,3 @@
-//go:build linux || darwin
-
 package netlink
 
 import "github.com/vishvananda/netlink"
@@ -62,8 +60,8 @@ func (n *NetLink) LinkSetDown(link Link) (err error) {
 	return netlink.LinkSetDown(linkToNetlinkLink(&link))
 }
 
-func (n *NetLink) LinkSetMTU(link Link, mtu int) error {
-	return netlink.LinkSetMTU(linkToNetlinkLink(&link), mtu)
+func (n *NetLink) LinkSetMTU(link Link, mtu uint32) error {
+	return netlink.LinkSetMTU(linkToNetlinkLink(&link), int(mtu))
 }
 
 type netlinkLinkImpl struct {

internal/netlink/link.go

@@ -0,0 +1,31 @@
+//go:build !linux
+
+package netlink
+
+const (
+	// FamilyAll is a placeholder only and should not
+	// be used.
+	FamilyAll = iota
+	// FamilyV4 is a placeholder only and should not
+	// be used.
+	FamilyV4
+	// FamilyV6 is a placeholder only and should not
+	// be used.
+	FamilyV6
+)
+
+func (n *NetLink) RuleList(family int) (rules []Rule, err error) {
+	panic("not implemented")
+}
+
+func (n *NetLink) RuleAdd(rule Rule) error {
+	panic("not implemented")
+}
+
+func (n *NetLink) RuleDel(rule Rule) error {
+	panic("not implemented")
+}
+
+func (n *NetLink) IsWireguardSupported() bool {
+	panic("not implemented")
+}

internal/netlink/link_unspecified.go

@@ -1,5 +1,3 @@
-//go:build linux || darwin
-
 package netlink
 
 import (