From 282beeddee6fc8617c7ebc16ee9490dbdae5d8eb Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Tue, 2 May 2023 16:40:12 -0700
Subject: [PATCH] Binding to an interface relies on Linux right now.

---
 server/ifi.go       | 43 +++++++++++--------------------------------
 server/ifi_linux.go | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 32 deletions(-)
 create mode 100644 server/ifi_linux.go

diff --git a/server/ifi.go b/server/ifi.go
index b70f388..50360b7 100644
--- a/server/ifi.go
+++ b/server/ifi.go
@@ -1,39 +1,18 @@
+// +build: !linux
+
 package server
 
 import (
+	"errors"
+	"fmt"
 	"net"
-	"syscall"
+	"runtime"
 )
 
-func BindInterface(ip net.IP, port int, dev string) (net.PacketConn, error) {
-	if port == 0 {
-		port = 67
-	}
-
-	udpAddr := &net.UDPAddr{
-		IP:   ip,
-		Port: port,
-	}
-
-	conn, err := net.ListenUDP("udp4", udpAddr)
-	if err != nil {
-		return nil, err
-	}
-
-	sysconn, err := conn.SyscallConn()
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-
-	sysconn.Control(func(fd uintptr) {
-		err = syscall.BindToDevice(int(fd), dev)
-	})
-
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-
-	return conn, nil
+func init() {
+	panic(fmt.Sprintf("%s is not a supported operating system", runtime.GOOS))
+}
+
+func BindInterface(ip net.IP, port int, dev string) (net.PacketConn, error) {
+	return nil, errors.New("server: %s does not support binding to an interface")
 }
diff --git a/server/ifi_linux.go b/server/ifi_linux.go
new file mode 100644
index 0000000..2a45433
--- /dev/null
+++ b/server/ifi_linux.go
@@ -0,0 +1,41 @@
+// +build: linux
+
+package server
+
+import (
+	"net"
+	"syscall"
+)
+
+func BindInterface(ip net.IP, port int, dev string) (net.PacketConn, error) {
+	if port == 0 {
+		port = 67
+	}
+
+	udpAddr := &net.UDPAddr{
+		IP:   ip,
+		Port: port,
+	}
+
+	conn, err := net.ListenUDP("udp4", udpAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	sysconn, err := conn.SyscallConn()
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	sysconn.Control(func(fd uintptr) {
+		err = syscall.BindToDevice(int(fd), dev)
+	})
+
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}