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Add BROKEN_NAT env variable to select Udp sender port workaround #501

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Jun 30, 2018
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Add BROKEN_NAT env variable to select Udp sender port workaround #501

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32 changes: 19 additions & 13 deletions src/nat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ use std::net::{IpAddr, Ipv4Addr, SocketAddr, UdpSocket};

use self::futures::Future;
use self::p2p::UdpSocketExt;
use std::env;

/// A data type representing a public Udp socket
pub struct UdpSocketPair {
Expand Down Expand Up @@ -42,19 +43,24 @@ pub fn udp_public_bind(label: &str) -> UdpSocketPair {
// |public_addr| to the local |receiver| socket...
let receiver = UdpSocket::bind(local_addr).unwrap();

// ... however for outbound packets, the NAT *will not* rewrite the
// source port from |receiver.local_addr().port()| to |public_addr.port()|.
// This is currently a problem when talking with a fullnode as it
// assumes it can send UDP packets back at the source. This hits the
// NAT as a datagram for |receiver.local_addr().port()| on the NAT's public
// IP, which the NAT promptly discards. As a short term hack, create a
// local UDP socket, |sender|, with the same port as |public_addr.port()|.
//
// TODO: Remove the |sender| socket and deal with the downstream changes to
// the UDP signalling
let mut local_addr_sender = local_addr.clone();
local_addr_sender.set_port(public_addr.port());
let sender = UdpSocket::bind(local_addr_sender).unwrap();
// TODO: try to autodetect a broken NAT (issue #496)
let sender = if env::var("BROKEN_NAT").is_err() {
receiver.try_clone().unwrap()
} else {
// ... however for outbound packets, some NATs *will not* rewrite the
// source port from |receiver.local_addr().port()| to |public_addr.port()|.
// This is currently a problem when talking with a fullnode as it
// assumes it can send UDP packets back at the source. This hits the
// NAT as a datagram for |receiver.local_addr().port()| on the NAT's public
// IP, which the NAT promptly discards. As a short term hack, create a
// local UDP socket, |sender|, with the same port as |public_addr.port()|.
//
// TODO: Remove the |sender| socket and deal with the downstream changes to
// the UDP signalling
let mut local_addr_sender = local_addr.clone();
local_addr_sender.set_port(public_addr.port());
UdpSocket::bind(local_addr_sender).unwrap()
};

UdpSocketPair {
addr: public_addr,
Expand Down