From bcacfb06385ab4177ffabe4e3aa979d3540b6428 Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Fri, 25 Oct 2019 18:33:23 -0500
Subject: [PATCH 1/2] test adding BindToDevice to linux. if it works then we'll
 want to rethink slightly how we get the tcpContext on every platform, to make
 this compile everywhere and look a little cleaner

---
 src/yggdrasil/tcp.go       |  1 +
 src/yggdrasil/tcp_linux.go | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/src/yggdrasil/tcp.go b/src/yggdrasil/tcp.go
index 7d5b80b2..0733b58a 100644
--- a/src/yggdrasil/tcp.go
+++ b/src/yggdrasil/tcp.go
@@ -299,6 +299,7 @@ func (t *tcp) call(saddr string, options interface{}, sintf string, upgrade *Tcp
 				Timeout: time.Second * 5,
 			}
 			if sintf != "" {
+				dialer.Control = t.getContextWithBindToDevice(sintf)
 				ief, err := net.InterfaceByName(sintf)
 				if err != nil {
 					return
diff --git a/src/yggdrasil/tcp_linux.go b/src/yggdrasil/tcp_linux.go
index 7eda3b5e..8d36f04c 100644
--- a/src/yggdrasil/tcp_linux.go
+++ b/src/yggdrasil/tcp_linux.go
@@ -29,3 +29,17 @@ func (t *tcp) tcpContext(network, address string, c syscall.RawConn) error {
 	// Return nil because errors here are not considered fatal for the connection, it just means congestion control is suboptimal
 	return nil
 }
+
+func (t *tcp) getContextWithBindToDevice(sintf string) func(string, string, syscall.RawConn) error {
+	return func(network, address string, c syscall.RawConn) error {
+		var err error
+		btd := func(fd uintptr) {
+			err = unix.BindToDevice(int(fd), sintf)
+		}
+		c.Control(btd)
+		if err != nil {
+			t.link.core.log.Debugln("Failed to set SO_BINDTODEVICE:", sintf)
+		}
+		return t.tcpContext(network, address, c)
+	}
+}

From 710815fed595af7abeac82ca088577e287d231d4 Mon Sep 17 00:00:00 2001
From: Arceliar <Arceliar@users.noreply.github.com>
Date: Fri, 25 Oct 2019 19:32:53 -0500
Subject: [PATCH 2/2] add dummy functions for other platforms

---
 src/yggdrasil/tcp.go        | 2 +-
 src/yggdrasil/tcp_darwin.go | 4 ++++
 src/yggdrasil/tcp_linux.go  | 2 +-
 src/yggdrasil/tcp_other.go  | 4 ++++
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/yggdrasil/tcp.go b/src/yggdrasil/tcp.go
index 0733b58a..9cca4193 100644
--- a/src/yggdrasil/tcp.go
+++ b/src/yggdrasil/tcp.go
@@ -299,7 +299,7 @@ func (t *tcp) call(saddr string, options interface{}, sintf string, upgrade *Tcp
 				Timeout: time.Second * 5,
 			}
 			if sintf != "" {
-				dialer.Control = t.getContextWithBindToDevice(sintf)
+				dialer.Control = t.getControl(sintf)
 				ief, err := net.InterfaceByName(sintf)
 				if err != nil {
 					return
diff --git a/src/yggdrasil/tcp_darwin.go b/src/yggdrasil/tcp_darwin.go
index 9d55a1db..3d0626c0 100644
--- a/src/yggdrasil/tcp_darwin.go
+++ b/src/yggdrasil/tcp_darwin.go
@@ -26,3 +26,7 @@ func (t *tcp) tcpContext(network, address string, c syscall.RawConn) error {
 		return control
 	}
 }
+
+func (t *tcp) getControl(sintf string) func(string, string, syscall.RawConn) error {
+	return t.tcpContext
+}
diff --git a/src/yggdrasil/tcp_linux.go b/src/yggdrasil/tcp_linux.go
index 8d36f04c..9ec3c10f 100644
--- a/src/yggdrasil/tcp_linux.go
+++ b/src/yggdrasil/tcp_linux.go
@@ -30,7 +30,7 @@ func (t *tcp) tcpContext(network, address string, c syscall.RawConn) error {
 	return nil
 }
 
-func (t *tcp) getContextWithBindToDevice(sintf string) func(string, string, syscall.RawConn) error {
+func (t *tcp) getControl(sintf string) func(string, string, syscall.RawConn) error {
 	return func(network, address string, c syscall.RawConn) error {
 		var err error
 		btd := func(fd uintptr) {
diff --git a/src/yggdrasil/tcp_other.go b/src/yggdrasil/tcp_other.go
index 44c3d76d..7ee41971 100644
--- a/src/yggdrasil/tcp_other.go
+++ b/src/yggdrasil/tcp_other.go
@@ -11,3 +11,7 @@ import (
 func (t *tcp) tcpContext(network, address string, c syscall.RawConn) error {
 	return nil
 }
+
+func (t *tcp) getControl(sintf string) func(string, string, syscall.RawConn) error {
+	return t.tcpContext
+}