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announce server hostname in MANIFEST, display in client

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Server reads its hostname via gethostname(2) and includes it as a
length-prefixed UTF-8 string at the start of the MANIFEST payload.

Client displays 'Server: <hostname> — <MAC>' in a label above the
upstream list. Both sides updated for the new MANIFEST format:
  [hostname_len:1][hostname:N][entries...]

Protocol version unchanged (still 1); MANIFEST payload layout change
is backward-incompatible but both sides ship together.
This commit is contained in:
Mute
2026-08-13 08:08:05 +00:00
parent 27e15452ee
commit 3336a08543
7 changed files with 110 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
PROTOCOL.md
+13 -3
View File
@@ -59,18 +59,27 @@ Reserved (unimplemented in v1; parse returns Err, encode unimplemented):
### MANIFEST payload
Variable-length entries, parsed sequentially until the payload is consumed.
A hostname prefix followed by variable-length entries, parsed sequentially
until the payload is consumed.
```
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+-------------------------------+
+---------------+-----------------------------------------------+
| hostname_len | hostname (UTF-8, hostname_len bytes) ... |
+---------------+-----------------------------------------------+
| id | proto | port (big-endian) |
+---------------+---------------+-------------------------------+
| label_len | label (UTF-8, label_len bytes) ... |
+---------------+-----------------------------------------------+
| ... repeated ... |
+---------------------------------------------------------------+
```
- **hostname_len** (u8): length in bytes of the server's hostname. `0` is valid
(unknown hostname).
- **hostname** (`hostname_len` bytes, UTF-8): the server's hostname, read via
`gethostname(2)` at startup. Maximum 255 bytes.
- **id** (u8): upstream identifier (1-based positional index from `gatunad`
cmdline).
- **proto** (u8): `1 = TCP`, `2 = UDP` (reserved; not emitted in v1).
@@ -80,7 +89,8 @@ Variable-length entries, parsed sequentially until the payload is consumed.
- **label** (`label_len` bytes, UTF-8): human-readable name for the upstream,
taken from the `PORT[:label]` cmdline argument. Maximum 255 bytes.
To parse: read the 5-byte fixed prefix, then `label_len` bytes, and repeat until
To parse: read `hostname_len`, then `hostname_len` bytes of hostname, then read
5-byte fixed entry prefixes + `label_len` bytes of label each, repeating until
the payload is exhausted. The number of entries is not carried explicitly.
### OPEN payload
gatunad/src/frame.rs
+24 -11
View File
@@ -39,7 +39,7 @@ pub struct UpstreamEntry {
#[derive(Clone, Debug)]
pub enum Frame {
Discover,
Manifest(Vec<UpstreamEntry>),
Manifest { hostname: String, entries: Vec<UpstreamEntry> },
Open { upstream_id: u8 },
OpenAck { session_id: u32, upstream_id: u8 },
OpenNak { upstream_id: u8, reason: u8 },
@@ -94,8 +94,12 @@ impl Frame {
pub fn encode(&self) -> Vec<u8> {
match self {
Frame::Discover => build(TYPE_DISCOVER, 0, Vec::new()),
Frame::Manifest(entries) => {
Frame::Manifest { hostname, entries } => {
let mut payload = Vec::new();
let hn_bytes = hostname.as_bytes();
let hn_len = hn_bytes.len().min(255) as u8;
payload.push(hn_len);
payload.extend_from_slice(&hn_bytes[..hn_len as usize]);
for e in entries {
encode_entry(&mut payload, e);
}
@@ -143,29 +147,38 @@ impl Frame {
Ok(Frame::Discover)
}
TYPE_MANIFEST => {
if payload.is_empty() {
return Err(DecodeError::BadPayload("MANIFEST missing hostname prefix"));
}
let hn_len = payload[0] as usize;
if 1 + hn_len > payload.len() {
return Err(DecodeError::BadPayload("MANIFEST hostname truncated"));
}
let hostname = String::from_utf8_lossy(&payload[1..1 + hn_len]).into_owned();
let rest = &payload[1 + hn_len..];
let mut entries = Vec::new();
let mut i = 0;
while i < payload.len() {
if i + 5 > payload.len() {
while i < rest.len() {
if i + 5 > rest.len() {
return Err(DecodeError::BadPayload("MANIFEST entry truncated"));
}
let id = payload[i];
let proto = payload[i + 1];
let port = u16::from_be_bytes([payload[i + 2], payload[i + 3]]);
let label_len = payload[i + 4] as usize;
let id = rest[i];
let proto = rest[i + 1];
let port = u16::from_be_bytes([rest[i + 2], rest[i + 3]]);
let label_len = rest[i + 4] as usize;
i += 5;
if i + label_len > payload.len() {
if i + label_len > rest.len() {
return Err(DecodeError::BadPayload("MANIFEST label truncated"));
}
let label = if label_len == 0 {
None
} else {
Some(String::from_utf8_lossy(&payload[i..i + label_len]).into_owned())
Some(String::from_utf8_lossy(&rest[i..i + label_len]).into_owned())
};
i += label_len;
entries.push(UpstreamEntry { id, proto, port, label });
}
Ok(Frame::Manifest(entries))
Ok(Frame::Manifest { hostname, entries })
}
TYPE_OPEN => {
if payload.len() != 1 {
gatunad/src/main.rs
+9 -3
View File
@@ -52,6 +52,8 @@ async fn main() -> ExitCode {
}
};
let hostname = Arc::new(upstream::get_hostname());
let link = match Link::open(&args.iface) {
Ok(l) => Arc::new(l),
Err(e) => {
@@ -112,7 +114,7 @@ async fn main() -> ExitCode {
continue;
}
};
handle_frame(frame, src, &tx, &store, &next_id, &table).await;
handle_frame(frame, src, &tx, &store, &next_id, &table, &hostname).await;
}
Ok(None) => {
// Ignorable frame (outgoing/short/mismatch) or transient; do not
@@ -135,10 +137,14 @@ async fn handle_frame(
store: &SessionStore,
next_id: &Arc<AtomicU32>,
table: &Arc<crate::upstream::UpstreamTable>,
hostname: &Arc<String>,
) {
match frame {
Frame::Discover => {
let manifest = Frame::Manifest(table.entries());
let manifest = Frame::Manifest {
hostname: (**hostname).clone(),
entries: table.entries(),
};
let _ = tx.send((src, manifest.encode())).await;
}
Frame::Open { upstream_id } => {
@@ -202,6 +208,6 @@ async fn handle_frame(
store.lock().expect("store poisoned").remove(&session_id);
}
// Not expected from a client; ignore.
Frame::Manifest(_) | Frame::OpenAck { .. } | Frame::OpenNak { .. } => {}
Frame::Manifest { .. } | Frame::OpenAck { .. } | Frame::OpenNak { .. } => {}
}
}
gatunad/src/upstream.rs
+15 -1
View File
@@ -1,6 +1,20 @@
//! Upstream table: cmdline parsing and MANIFEST entry construction.
use crate::frame::{UpstreamEntry, PROTO_TCP, PROTO_UDP};
use crate::frame::{Frame, UpstreamEntry, PROTO_TCP, PROTO_UDP};
/// Read the system hostname via `gethostname(2)`.
pub fn get_hostname() -> String {
let mut buf = [0u8; 256];
let ret = unsafe {
libc::gethostname(buf.as_mut_ptr() as *mut libc::c_char, buf.len())
};
if ret == 0 {
let len = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());
String::from_utf8_lossy(&buf[..len]).into_owned()
} else {
String::new()
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
#[allow(dead_code)]
win/gatuna-client/Frame.cs
+27 -12
View File
@@ -40,7 +40,7 @@ readonly record struct UpstreamEntry(
abstract record Frame
{
internal record Discover : Frame;
internal record Manifest(UpstreamEntry[] Entries) : Frame;
internal record Manifest(string Hostname, UpstreamEntry[] Entries) : Frame;
internal record Open(byte UpstreamId) : Frame;
internal record OpenAck(uint SessionId, byte UpstreamId) : Frame;
internal record OpenNak(byte UpstreamId, byte Reason) : Frame;
@@ -74,7 +74,7 @@ static class FrameCodec
Frame.Discover =>
Build(Proto.TypeDiscover, 0, []),
Frame.Manifest manifest =>
Build(Proto.TypeManifest, 0, BuildManifestPayload(manifest.Entries)),
Build(Proto.TypeManifest, 0, BuildManifestPayload(manifest.Hostname, manifest.Entries)),
Frame.Open open =>
Build(Proto.TypeOpen, 0, [open.UpstreamId]),
Frame.OpenAck ack =>
@@ -90,9 +90,14 @@ static class FrameCodec
};
}
static byte[] BuildManifestPayload(UpstreamEntry[] entries)
static byte[] BuildManifestPayload(string hostname, UpstreamEntry[] entries)
{
using var ms = new MemoryStream();
var hnBytes = Encoding.UTF8.GetBytes(hostname);
var hnLen = (byte)Math.Min(hnBytes.Length, 255);
ms.WriteByte(hnLen);
if (hnLen > 0)
ms.Write(hnBytes, 0, hnLen);
foreach (var e in entries)
{
var labelBytes = Encoding.UTF8.GetBytes(e.Label ?? "");
@@ -141,25 +146,35 @@ static class FrameCodec
static Frame.Manifest? ParseManifest(ReadOnlySpan<byte> payload)
{
if (payload.Length < 1)
return null;
var hnLen = payload[0];
if (1 + hnLen > payload.Length)
return null;
var hostname = hnLen == 0
? ""
: Encoding.UTF8.GetString(payload[1..(1 + hnLen)]);
var rest = payload[(1 + hnLen)..];
var entries = new List<UpstreamEntry>();
int i = 0;
while (i < payload.Length)
while (i < rest.Length)
{
if (i + 5 > payload.Length)
if (i + 5 > rest.Length)
return null;
var id = payload[i];
var proto = payload[i + 1];
var port = (ushort)(payload[i + 2] << 8 | payload[i + 3]);
var labelLen = payload[i + 4];
var id = rest[i];
var proto = rest[i + 1];
var port = (ushort)(rest[i + 2] << 8 | rest[i + 3]);
var labelLen = rest[i + 4];
i += 5;
if (i + labelLen > payload.Length)
if (i + labelLen > rest.Length)
return null;
string? label = labelLen == 0
? null
: Encoding.UTF8.GetString(payload[i..(i + labelLen)]);
: Encoding.UTF8.GetString(rest[i..(i + labelLen)]);
i += labelLen;
entries.Add(new UpstreamEntry(id, proto, port, label));
}
return new Frame.Manifest(entries.ToArray());
return new Frame.Manifest(hostname, entries.ToArray());
}
}
win/gatuna-client/MainForm.cs
+16 -4
View File
@@ -7,6 +7,7 @@ public partial class MainForm : Form
readonly SessionManager _sessions = new();
readonly ComboBox _deviceBox = new();
readonly Button _discoverBtn = new();
readonly Label _serverLabel = new();
readonly ListView _listView = new();
readonly Label _statusLabel = new();
TunnelLink? _link;
@@ -23,7 +24,8 @@ public partial class MainForm : Form
InitializeComponents();
_sessions.Log += msg => this.Invoke(() => _statusLabel.Text = msg);
_sessions.ManifestReceived += entries => this.Invoke(() => PopulateList(entries));
_sessions.ManifestReceived += (hostname, mac, entries) =>
this.Invoke(() => PopulateList(hostname, mac, entries));
foreach (var d in TunnelLink.ListDevices())
{
@@ -54,9 +56,15 @@ public partial class MainForm : Form
_discoverBtn.Click += OnDiscover;
Controls.Add(_discoverBtn);
_listView.Left = pad; _listView.Top = _discoverBtn.Bottom + 8;
_serverLabel.Left = pad; _serverLabel.Top = _discoverBtn.Bottom + 8;
_serverLabel.Width = ClientSize.Width - pad * 2;
_serverLabel.AutoEllipsis = true;
_serverLabel.Text = "Server: not connected";
Controls.Add(_serverLabel);
_listView.Left = pad; _listView.Top = _serverLabel.Bottom + 8;
_listView.Width = ClientSize.Width - pad * 2;
_listView.Height = 220;
_listView.Height = 200;
_listView.View = View.Details;
_listView.FullRowSelect = true;
_listView.CheckBoxes = true;
@@ -96,11 +104,15 @@ public partial class MainForm : Form
_sessions.AttachLink(_link);
_link.Open();
_sessions.Discover();
_serverLabel.Text = "Server: discovering...";
_statusLabel.Text = "discovering...";
}
void PopulateList(UpstreamEntry[] entries)
void PopulateList(string hostname, byte[] mac, UpstreamEntry[] entries)
{
var macStr = string.Join(":", mac.Select(b => b.ToString("X2")));
_serverLabel.Text = $"Server: {hostname} — {macStr}";
_listView.BeginUpdate();
_listView.Items.Clear();
foreach (var up in entries)
win/gatuna-client/SessionManager.cs
+6 -3
View File
@@ -12,6 +12,7 @@ sealed class SessionManager : IDisposable
readonly ConcurrentDictionary<int, ListenerState> _listeners = new();
byte[]? _serverMac;
string _serverHostname = "";
UpstreamEntry[] _upstreams = [];
// Serialized OPEN: only one outstanding at a time.
@@ -20,10 +21,11 @@ sealed class SessionManager : IDisposable
readonly Queue<PendingOpen> _openQueue = new();
public event Action<string>? Log;
public event Action<UpstreamEntry[]>? ManifestReceived;
public event Action<string, byte[], UpstreamEntry[]>? ManifestReceived;
public UpstreamEntry[] Upstreams => _upstreams;
public byte[]? ServerMac => _serverMac;
public string ServerHostname => _serverHostname;
public TunnelLink? Link => _link;
public void AttachLink(TunnelLink link)
@@ -51,9 +53,10 @@ sealed class SessionManager : IDisposable
{
case Frame.Manifest manifest:
_serverMac = srcMac;
_serverHostname = manifest.Hostname;
_upstreams = manifest.Entries;
Log?.Invoke($"manifest: {manifest.Entries.Length} upstreams from {BitConverter.ToString(srcMac)}");
ManifestReceived?.Invoke(manifest.Entries);
Log?.Invoke($"manifest: {manifest.Entries.Length} upstreams from {manifest.Hostname} ({BitConverter.ToString(srcMac)})");
ManifestReceived?.Invoke(manifest.Hostname, srcMac, manifest.Entries);
break;
case Frame.OpenAck ack: