From 66ef395afc2363e45e987b805cacad28bfab82e3 Mon Sep 17 00:00:00 2001
From: Joshua Goins <josh@redstrate.com>
Date: Sat, 8 Mar 2025 14:09:57 -0500
Subject: [PATCH] Begin parsing the packet header

---
 Cargo.lock    | 68 ++++++++++++++++++++++++++++++++++++++++++++++++---
 Cargo.toml    |  1 +
 src/packet.rs | 53 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 115 insertions(+), 7 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index eb5dc0b..ac014dc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -17,6 +17,12 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "array-init"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d62b7694a562cdf5a74227903507c56ab2cc8bdd1f781ed5cb4cf9c9f810bfc"
+
 [[package]]
 name = "async-trait"
 version = "0.1.80"
@@ -25,7 +31,7 @@ checksum = "c6fa2087f2753a7da8cc1c0dbfcf89579dd57458e36769de5ac750b4671737ca"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.62",
 ]
 
 [[package]]
@@ -99,6 +105,30 @@ version = "0.21.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
 
+[[package]]
+name = "binrw"
+version = "0.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d4bca59c20d6f40c2cc0802afbe1e788b89096f61bdf7aeea6bf00f10c2909b"
+dependencies = [
+ "array-init",
+ "binrw_derive",
+ "bytemuck",
+]
+
+[[package]]
+name = "binrw_derive"
+version = "0.14.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8ba42866ce5bced2645bfa15e97eef2c62d2bdb530510538de8dd3d04efff3c"
+dependencies = [
+ "either",
+ "owo-colors",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+]
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -114,6 +144,12 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "bytemuck"
+version = "1.22.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6b1fc10dbac614ebc03540c9dbd60e83887fda27794998c6528f1782047d540"
+
 [[package]]
 name = "bytes"
 version = "1.6.0"
@@ -161,6 +197,12 @@ dependencies = [
  "crypto-common",
 ]
 
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -334,6 +376,7 @@ name = "kawari"
 version = "0.1.0"
 dependencies = [
  "axum",
+ "binrw",
  "minijinja",
  "rand",
  "serde",
@@ -427,6 +470,12 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
+[[package]]
+name = "owo-colors"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1b04fb49957986fdce4d6ee7a65027d55d4b6d2265e5848bbb507b58ccfdb6f"
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.1"
@@ -450,7 +499,7 @@ checksum = "2f38a4412a78282e09a2cf38d195ea5420d15ba0602cb375210efbc877243965"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.62",
 ]
 
 [[package]]
@@ -554,7 +603,7 @@ checksum = "c5e405930b9796f1c00bee880d03fc7e0bb4b9a11afc776885ffe84320da2865"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.62",
 ]
 
 [[package]]
@@ -620,6 +669,17 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.62"
@@ -672,7 +732,7 @@ checksum = "5b8a1e28f2deaa14e508979454cb3a223b10b938b45af148bc0986de36f1923b"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.62",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index fb6c7a3..aeeb333 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,3 +34,4 @@ serde = { version = "1.0", features = ["derive"], default-features = false }
 tracing-subscriber = { version = "0.3", features = ["fmt"], default-features = false }
 rand = "0.8"
 minijinja = "2.0"
+binrw = { version = "0.14" }
diff --git a/src/packet.rs b/src/packet.rs
index e66202b..362f517 100644
--- a/src/packet.rs
+++ b/src/packet.rs
@@ -1,6 +1,53 @@
-use std::fs::write;
+use std::{fs::write, io::Cursor};
+
+use binrw::{binrw, BinRead};
+
+pub(crate) fn read_bool_from<T: std::convert::From<u8> + std::cmp::PartialEq>(x: T) -> bool {
+    x == T::from(1u8)
+}
+
+pub(crate) fn write_bool_as<T: std::convert::From<u8>>(x: &bool) -> T {
+    if *x { T::from(1u8) } else { T::from(0u8) }
+}
+
+#[binrw]
+#[brw(repr = u16)]
+#[derive(Debug)]
+enum ConnectionType {
+    Lobby = 0x3,
+}
+
+#[binrw]
+#[derive(Debug)]
+struct PacketHeader {
+    unk1: u64,
+    unk2: u64,
+    timestamp: u64,
+    size: u32,
+    connection_type: ConnectionType,
+    count: u16,
+    unk3: u8,
+    #[br(map = read_bool_from::<u8>)]
+    #[bw(map = write_bool_as::<u8>)]
+    compressed: bool,
+    unk4: u32,
+}
+
+fn dump(msg: &str, data: &[u8]) {
+    write("packet.bin", data);
+    panic!("{msg} Dumped to packet.bin.");
+}
 
 pub fn parse_packet(data: &[u8]) {
-    write("packet.bin", data);
-    panic!("Unknown packet! Dumping to packet.bin.");
+    let mut cursor = Cursor::new(data);
+
+    if let Ok(packet) = PacketHeader::read_le(&mut cursor) {
+        println!("{:#?}", packet);
+
+        if packet.size as usize != data.len() {
+            dump("Packet size mismatch between what we're given and the header!", data);
+        }
+    } else {
+        dump("Failed to parse packet!", data);
+    }
 }