From 29c8d5636fb7b86e4f9a47a93b2324a53e271a17 Mon Sep 17 00:00:00 2001
From: Jake McGinty <me@jake.su>
Date: Thu, 5 Apr 2018 00:54:12 -0700
Subject: udp: only convert 'mapped', not 'compatible' adddresses, to IPv4
 internally

---
 src/udp/frame.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/udp/frame.rs b/src/udp/frame.rs
index 7f38e57..1f4feaf 100644
--- a/src/udp/frame.rs
+++ b/src/udp/frame.rs
@@ -7,6 +7,7 @@ use futures::{Async, Future, Poll, Stream, Sink, StartSend, AsyncSink, future, s
 use nix::sys::socket::{sockopt, setsockopt};
 use udp::{ConnectedUdpSocket, UdpSocket};
 use tokio_core::reactor::Handle;
+use std::net::Ipv6Addr;
 
 pub enum Socket {
     Unconnected(UdpSocket),
@@ -154,13 +155,23 @@ impl UdpFramed {
     }
 }
 
+fn v6_mapped_to_v4(addr: Ipv6Addr) -> Option<Ipv4Addr> {
+    match addr.segments() {
+        [0, 0, 0, 0, 0, f, g, h] if f == 0xffff => {
+            Some(Ipv4Addr::new((g >> 8) as u8, g as u8,
+                               (h >> 8) as u8, h as u8))
+        },
+        _ => None
+    }
+}
+
 pub type PeerServerMessage = (SocketAddr, Vec<u8>);
 pub struct VecUdpCodec;
 impl VecUdpCodec {
     fn decode(&mut self, src: &SocketAddr, buf: &[u8]) -> io::Result<PeerServerMessage> {
         let unmapped_ip = match src.ip() {
             IpAddr::V6(v6addr) => {
-                if let Some(v4addr) = v6addr.to_ipv4() {
+                if let Some(v4addr) = v6_mapped_to_v4(v6addr) {
                     IpAddr::V4(v4addr)
                 } else {
                     IpAddr::V6(v6addr)
-- 
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