From 496ca31b8035e68c6e95fd1aadb8c08d81adc472 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Em=C4=ABls=20Pi=C5=86=C4=B7is?= <emils@mullvad.net>
Date: Mon, 26 Apr 2021 16:07:56 +0100
Subject: [PATCH] Pass whole buffer and offset to tunnel writer

---
 src/platform/linux/tun.rs       | 5 +++--
 src/platform/tun.rs             | 2 +-
 src/wireguard/router/receive.rs | 2 +-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/platform/linux/tun.rs b/src/platform/linux/tun.rs
index 82fada1..304966d 100644
--- a/src/platform/linux/tun.rs
+++ b/src/platform/linux/tun.rs
@@ -106,8 +106,9 @@ impl Reader for LinuxTunReader {
 impl Writer for LinuxTunWriter {
     type Error = LinuxTunError;
 
-    fn write(&self, src: &[u8]) -> Result<(), Self::Error> {
-        match unsafe { libc::write(self.fd, src.as_ptr() as _, src.len() as _) } {
+    fn write(&self, src: &[u8], offset: usize) -> Result<(), Self::Error> {
+        let data = &src[offset..];
+        match unsafe { libc::write(self.fd, data.as_ptr() as _, data.len() as _) } {
             -1 => Err(LinuxTunError::Closed),
             _ => Ok(()),
         }
diff --git a/src/platform/tun.rs b/src/platform/tun.rs
index 38c95bf..b54179c 100644
--- a/src/platform/tun.rs
+++ b/src/platform/tun.rs
@@ -25,7 +25,7 @@ pub trait Writer: Send + Sync + 'static {
     /// # Returns
     ///
     /// Unit type or an error
-    fn write(&self, src: &[u8]) -> Result<(), Self::Error>;
+    fn write(&self, src: &mut [u8], offset: usize) -> Result<(), Self::Error>;
 }
 
 pub trait Reader: Send + 'static {
diff --git a/src/wireguard/router/receive.rs b/src/wireguard/router/receive.rs
index 15eb8fb..034216a 100644
--- a/src/wireguard/router/receive.rs
+++ b/src/wireguard/router/receive.rs
@@ -173,7 +173,7 @@ impl<E: Endpoint, C: Callbacks, T: tun::Writer, B: udp::Writer<E>> SequentialJob
         // (keep-alive and malformed packets will have no inner length)
         if let Some(inner) = inner_length(packet) {
             if inner + SIZE_TAG <= packet.len() {
-                let _ = peer.device.inbound.write(&packet[..inner]).map_err(|e| {
+                let _ = peer.device.inbound.write(&packet, inner).map_err(|e| {
                     log::debug!("failed to write inbound packet to TUN: {:?}", e);
                 });
             }