From 02e2644d519ef674a79b38c6ffb97dafe1f9a85a Mon Sep 17 00:00:00 2001
From: Evan Pratten <ewpratten@gmail.com>
Date: Sun, 16 Jul 2023 21:29:45 -0400
Subject: [PATCH] functional TCP

---
 src/nat/xlat/tcp.rs | 55 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/src/nat/xlat/tcp.rs b/src/nat/xlat/tcp.rs
index af723ef..f3d39cb 100644
--- a/src/nat/xlat/tcp.rs
+++ b/src/nat/xlat/tcp.rs
@@ -4,7 +4,8 @@ use pnet_packet::{
     ip::IpNextHeaderProtocols,
     ipv4::{self, Ipv4Packet, MutableIpv4Packet},
     ipv6::{Ipv6Packet, MutableIpv6Packet},
-    Packet, tcp::TcpPacket,
+    tcp::{self, MutableTcpPacket, TcpPacket},
+    Packet,
 };
 
 use crate::nat::packet::IpPacket;
@@ -24,20 +25,43 @@ pub async fn proxy_tcp_packet<'a>(
     // Parse the original packet's payload to extract UDP data
     let tcp_packet = TcpPacket::new(original_packet.get_payload())
         .ok_or_else(|| TcpProxyError::PacketTooShort(original_packet.get_payload().len()))?;
+    log::debug!(
+        "Incoming TCP packet ports: {} -> {}",
+        tcp_packet.get_source(),
+        tcp_packet.get_destination()
+    );
+    log::debug!(
+        "Incoming TCP packet payload len: {}",
+        tcp_packet.payload().len()
+    );
 
     // Construct a new output packet
     match (&original_packet, new_source, new_destination) {
         // Translate IPv4(UDP) to IPv6(UDP)
         (IpPacket::V4(_), IpAddr::V6(new_source), IpAddr::V6(new_destination)) => {
+            // Construct translated TCP packet
+            let mut translated_tcp_packet =
+                MutableTcpPacket::owned(tcp_packet.packet().to_vec()).unwrap();
+
+            // Rewrite the checksum
+            translated_tcp_packet.set_checksum(0);
+            translated_tcp_packet.set_checksum(tcp::ipv6_checksum(
+                &translated_tcp_packet.to_immutable(),
+                &new_source,
+                &new_destination,
+            ));
+
+            // Construct translated IP packet to wrap TCP packet
             let mut output =
-                MutableIpv6Packet::owned(vec![0u8; 40 + tcp_packet.packet().len()]).unwrap();
+                MutableIpv6Packet::owned(vec![0u8; 40 + translated_tcp_packet.packet().len()])
+                    .unwrap();
             output.set_version(6);
             output.set_source(new_source);
             output.set_destination(new_destination);
             output.set_hop_limit(original_packet.get_ttl());
-            output.set_next_header(IpNextHeaderProtocols::Udp);
-            output.set_payload_length(tcp_packet.packet().len() as u16);
-            output.set_payload(tcp_packet.packet());
+            output.set_next_header(IpNextHeaderProtocols::Tcp);
+            output.set_payload_length(translated_tcp_packet.packet().len() as u16);
+            output.set_payload(translated_tcp_packet.packet());
             Ok(IpPacket::V6(
                 Ipv6Packet::owned(output.to_immutable().packet().to_vec()).unwrap(),
             ))
@@ -45,16 +69,29 @@ pub async fn proxy_tcp_packet<'a>(
 
         // Translate IPv6(UDP) to IPv4(UDP)
         (IpPacket::V6(_), IpAddr::V4(new_source), IpAddr::V4(new_destination)) => {
+            // Construct translated TCP packet
+            let mut translated_tcp_packet =
+                MutableTcpPacket::owned(tcp_packet.packet().to_vec()).unwrap();
+
+            // Rewrite the checksum
+            translated_tcp_packet.set_checksum(0);
+            translated_tcp_packet.set_checksum(tcp::ipv4_checksum(
+                &translated_tcp_packet.to_immutable(),
+                &new_source,
+                &new_destination,
+            ));
+
+            // Construct translated IP packet to wrap TCP packet
             let mut output =
-                MutableIpv4Packet::owned(vec![0u8; 20 + tcp_packet.packet().len()]).unwrap();
+                MutableIpv4Packet::owned(vec![0u8; 20 + translated_tcp_packet.packet().len()]).unwrap();
             output.set_version(4);
             output.set_source(new_source);
             output.set_destination(new_destination);
             output.set_ttl(original_packet.get_ttl());
-            output.set_next_level_protocol(IpNextHeaderProtocols::Udp);
+            output.set_next_level_protocol(IpNextHeaderProtocols::Tcp);
             output.set_header_length(5);
-            output.set_total_length(20 + tcp_packet.packet().len() as u16);
-            output.set_payload(tcp_packet.packet());
+            output.set_total_length(20 + translated_tcp_packet.packet().len() as u16);
+            output.set_payload(translated_tcp_packet.packet());
             output.set_checksum(0);
             output.set_checksum(ipv4::checksum(&output.to_immutable()));
             Ok(IpPacket::V4(