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proto/rwhod: improve de/serialization and datatypes

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This commit is contained in:
Oystein Kristoffer Tveit
2026-01-04 20:16:59 +09:00
parent b12752bd17
commit dabc54a943
9 changed files with 319 additions and 92 deletions
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1
src/proto/finger_protocol.rs
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1
src/proto/rusers_protocol.rs
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318
src/proto/rwhod_protocol.rs
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@@ -1,5 +1,11 @@
use std::array;
use bytes::{Buf, BufMut, BytesMut};
use chrono::Duration;
/// Classic C struct for utmp data for a single user session.
///
/// This struct is used in the rwhod protocol by being interpreted as raw bytes to be sent over UDP.
#[derive(Debug, Clone)]
#[repr(C)]
pub struct Outmp {
@@ -16,6 +22,9 @@ impl Outmp {
pub const MAX_USER_ID_LEN: usize = 8;
}
/// Classic C struct for a single user session.
///
/// This struct is used in the rwhod protocol by being interpreted as raw bytes to be sent over UDP.
#[derive(Debug, Clone)]
#[repr(C)]
pub struct Whoent {
@@ -25,6 +34,31 @@ pub struct Whoent {
pub we_idle: i32,
}
impl Whoent {
pub const SIZE: usize = std::mem::size_of::<Self>();
fn zeroed() -> Self {
Self {
we_utmp: Outmp {
out_line: [0u8; Outmp::MAX_TTY_NAME_LEN],
out_name: [0u8; Outmp::MAX_USER_ID_LEN],
out_time: 0,
},
we_idle: 0,
}
}
fn is_zeroed(&self) -> bool {
self.we_utmp.out_line.iter().all(|&b| b == 0)
&& self.we_utmp.out_name.iter().all(|&b| b == 0)
&& self.we_utmp.out_time == 0
&& self.we_idle == 0
}
}
/// Classic C struct for a rwhod status update.
///
/// This struct is used in the rwhod protocol by being interpreted as raw bytes to be sent over UDP.
#[derive(Debug, Clone)]
#[repr(C)]
pub struct Whod {
@@ -47,7 +81,9 @@ pub struct Whod {
}
impl Whod {
pub const SIZE: usize = std::mem::size_of::<Whod>();
pub const HEADER_SIZE: usize = 1 + 1 + 2 + 4 + 4 + Self::MAX_HOSTNAME_LEN + 4 * 3 + 4;
pub const MAX_SIZE: usize = std::mem::size_of::<Self>();
pub const MAX_HOSTNAME_LEN: usize = 32;
pub const MAX_WHOENTRIES: usize = 1024 / std::mem::size_of::<Whoent>();
@@ -56,42 +92,170 @@ impl Whod {
// NOTE: there was probably meant to be more packet types, but only status is defined.
pub const WHODTYPE_STATUS: u8 = 1;
pub fn to_bytes(&self) -> [u8; std::mem::size_of::<Whod>()] {
unsafe { std::mem::transmute_copy(self) }
pub fn new(
sendtime: i32,
recvtime: i32,
hostname: [u8; Self::MAX_HOSTNAME_LEN],
loadav: [i32; 3],
boottime: i32,
whoentries: [Whoent; Self::MAX_WHOENTRIES],
) -> Self {
debug_assert!(
whoentries
.iter()
.skip_while(|entry| !entry.is_zeroed())
.all(|entry| entry.is_zeroed())
);
Self {
wd_vers: Self::WHODVERSION,
wd_type: Self::WHODTYPE_STATUS,
wd_pad: [0u8; 2],
wd_sendtime: sendtime,
wd_recvtime: recvtime,
wd_hostname: hostname,
wd_loadav: loadav,
wd_boottime: boottime,
wd_we: whoentries,
}
}
// TODO: we should probably make a safer parser.
pub fn from_bytes(bytes: &[u8; std::mem::size_of::<Whod>()]) -> Self {
unsafe { std::mem::transmute_copy(bytes) }
pub fn to_bytes(&self) -> [u8; Whod::MAX_SIZE] {
let mut buf = BytesMut::with_capacity(Whod::MAX_SIZE);
buf.put_u8(self.wd_vers);
buf.put_u8(self.wd_type);
buf.put_slice(&self.wd_pad);
buf.put_i32(self.wd_sendtime);
buf.put_i32(self.wd_recvtime);
buf.put_slice(&self.wd_hostname);
buf.put_i32(self.wd_loadav[0]);
buf.put_i32(self.wd_loadav[1]);
buf.put_i32(self.wd_loadav[2]);
buf.put_i32(self.wd_boottime);
for whoent in &self.wd_we {
buf.put_slice(&whoent.we_utmp.out_line);
buf.put_slice(&whoent.we_utmp.out_name);
buf.put_i32(whoent.we_utmp.out_time);
buf.put_i32(whoent.we_idle);
}
// SAFETY: this should never happen, Whod::MAX_SIZE is computed from the struct size
buf
.to_vec()
.try_into()
.expect("Buffer length mismatch, this should never happen")
}
pub fn from_bytes(input: &[u8]) -> anyhow::Result<Self> {
if input.len() < Self::HEADER_SIZE {
return Err(anyhow::anyhow!(
"Not enough bytes to parse packet header: {} < {}",
input.len(),
Self::HEADER_SIZE
));
}
if input.len() > Self::MAX_SIZE {
return Err(anyhow::anyhow!(
"Too many bytes to parse packet: {} > {}",
input.len(),
Self::MAX_SIZE
));
}
if !(input.len() - Self::HEADER_SIZE).is_multiple_of(Whoent::SIZE) {
return Err(anyhow::anyhow!(
"Invalid packet length: {} (not aligned with struct sizes, should be {} + N * {})",
input.len(),
Self::HEADER_SIZE,
Whoent::SIZE,
));
}
let mut bytes = bytes::Bytes::copy_from_slice(input);
let wd_vers = bytes.get_u8();
debug_assert!(wd_vers == Self::WHODVERSION);
let wd_type = bytes.get_u8();
debug_assert!(wd_type == Self::WHODTYPE_STATUS);
bytes.advance(2); // skip wd_pad
let wd_sendtime = bytes.get_i32();
let wd_recvtime = bytes.get_i32();
let mut wd_hostname = [0u8; Self::MAX_HOSTNAME_LEN];
bytes.copy_to_slice(&mut wd_hostname);
let wd_loadav = [bytes.get_i32(), bytes.get_i32(), bytes.get_i32()];
let wd_boottime = bytes.get_i32();
debug_assert!(bytes.remaining() + Self::HEADER_SIZE == input.len());
let mut wd_we = array::from_fn(|_| Whoent::zeroed());
for (byte_chunk, whoent) in bytes.chunks_exact(Whoent::SIZE).zip(wd_we.iter_mut()) {
let mut chunk_bytes = bytes::Bytes::copy_from_slice(byte_chunk);
let mut out_line = [0u8; Outmp::MAX_TTY_NAME_LEN];
chunk_bytes.copy_to_slice(&mut out_line);
let mut out_name = [0u8; Outmp::MAX_USER_ID_LEN];
chunk_bytes.copy_to_slice(&mut out_name);
let out_time = chunk_bytes.get_i32();
let we_utmp = Outmp {
out_line,
out_name,
out_time,
};
let we_idle = chunk_bytes.get_i32();
*whoent = Whoent { we_utmp, we_idle };
}
let result = Whod::new(
wd_sendtime,
wd_recvtime,
wd_hostname,
wd_loadav,
wd_boottime,
wd_we,
);
Ok(result)
}
}
// ------------------------------------------------
/// High-level representation of a rwhod status update.
///
/// This struct is intended for easier use in Rust code, with proper types and dynamic arrays.
/// It can be converted to and from the low-level [`Whod`] struct used for network transmission.
#[derive(Debug, Clone)]
pub struct WhodStatusUpdate {
// NOTE: there is only one defined packet type, so we just omit it here
/// Timestamp by sender
sendtime: chrono::DateTime<chrono::Utc>,
pub sendtime: chrono::DateTime<chrono::Utc>,
/// Timestamp applied by receiver
recvtime: Option<chrono::DateTime<chrono::Utc>>,
pub recvtime: Option<chrono::DateTime<chrono::Utc>>,
/// Name of the host sending the status update (max 32 characters)
hostname: String,
pub hostname: String,
/// load average over 5 minutes multiplied by 100
load_average_5_min: i32,
pub load_average_5_min: i32,
/// load average over 10 minutes multiplied by 100
load_average_10_min: i32,
pub load_average_10_min: i32,
/// load average over 15 minutes multiplied by 100
load_average_15_min: i32,
pub load_average_15_min: i32,
/// Which time the system was booted
boot_time: chrono::DateTime<chrono::Utc>,
pub boot_time: chrono::DateTime<chrono::Utc>,
/// List of users currently logged in to the host (max 42 entries)
users: Vec<WhodUserEntry>,
pub users: Vec<WhodUserEntry>,
}
impl WhodStatusUpdate {
@@ -118,19 +282,23 @@ impl WhodStatusUpdate {
}
}
/// High-level representation of a single user session in a rwhod status update.
///
/// This struct is intended for easier use in Rust code, with proper types.
/// It can be converted to and from the low-level [`Whoent`] struct used for network transmission.
#[derive(Debug, Clone)]
pub struct WhodUserEntry {
/// TTY name (max 8 characters)
tty: String,
pub tty: String,
/// User ID (max 8 characters)
user_id: String,
pub user_id: String,
/// Time when the user logged in
login_time: chrono::DateTime<chrono::Utc>,
pub login_time: chrono::DateTime<chrono::Utc>,
/// Idle time in seconds
idle_time_seconds: i32,
/// How long since the user last typed on the TTY
pub idle_time: Duration,
}
impl WhodUserEntry {
@@ -138,13 +306,13 @@ impl WhodUserEntry {
tty: String,
user_id: String,
login_time: chrono::DateTime<chrono::Utc>,
idle_time_seconds: i32,
idle_time: Duration,
) -> Self {
Self {
tty,
user_id,
login_time,
idle_time_seconds,
idle_time,
}
}
}
@@ -181,7 +349,7 @@ impl TryFrom<Whoent> for WhodUserEntry {
tty,
user_id,
login_time,
idle_time_seconds: value.we_idle,
idle_time: Duration::seconds(value.we_idle as i64),
})
}
}
@@ -224,11 +392,13 @@ impl TryFrom<Whod> for WhodStatusUpdate {
format!("Invalid boot time timestamp: {}", value.wd_boottime),
)?;
let mut users = Vec::new();
for whoent in &value.wd_we {
let user_entry = WhodUserEntry::try_from(whoent.clone())?;
users.push(user_entry);
}
let users = value
.wd_we
.iter()
.take_while(|whoent| !whoent.is_zeroed())
.cloned()
.map(WhodUserEntry::try_from)
.collect::<Result<Vec<WhodUserEntry>, String>>()?;
Ok(WhodStatusUpdate {
sendtime,
@@ -243,91 +413,89 @@ impl TryFrom<Whod> for WhodStatusUpdate {
}
}
// TODO: support less strict conversions with truncation
impl TryFrom<WhodUserEntry> for Whoent {
type Error = String;
fn try_from(value: WhodUserEntry) -> Result<Self, Self::Error> {
let mut out_line = [0u8; 8];
let mut out_line = [0u8; Outmp::MAX_TTY_NAME_LEN];
let tty_bytes = value.tty.as_bytes();
if tty_bytes.len() > out_line.len() {
return Err(format!(
"TTY name too long: {} (max {})",
value.tty,
out_line.len()
));
}
out_line[..tty_bytes.len()].copy_from_slice(tty_bytes);
out_line[..tty_bytes.len().min(Outmp::MAX_TTY_NAME_LEN)].copy_from_slice(tty_bytes);
let mut out_name = [0u8; 8];
let mut out_name = [0u8; Outmp::MAX_USER_ID_LEN];
let user_id_bytes = value.user_id.as_bytes();
if user_id_bytes.len() > out_name.len() {
return Err(format!(
"User ID too long: {} (max {})",
value.user_id,
out_name.len()
));
}
out_name[..user_id_bytes.len()].copy_from_slice(user_id_bytes);
out_name[..user_id_bytes.len().min(Outmp::MAX_USER_ID_LEN)].copy_from_slice(user_id_bytes);
let out_time = value
.login_time
.timestamp()
.max(i32::MAX as i64)
.min(i32::MIN as i64) as i32;
let we_idle = value
.idle_time
.num_seconds()
.max(i32::MAX as i64)
.min(i32::MIN as i64) as i32;
Ok(Whoent {
we_utmp: Outmp {
out_line,
out_name,
out_time: value.login_time.timestamp() as i32,
out_time,
},
we_idle: value.idle_time_seconds,
we_idle,
})
}
}
// TODO: support less strict conversions with truncation
impl TryFrom<WhodStatusUpdate> for Whod {
type Error = String;
fn try_from(value: WhodStatusUpdate) -> Result<Self, Self::Error> {
let mut wd_hostname = [0u8; Whod::MAX_HOSTNAME_LEN];
let hostname_bytes = value.hostname.as_bytes();
if hostname_bytes.len() > wd_hostname.len() {
return Err(format!(
"Hostname too long: {} (max {})",
value.hostname,
wd_hostname.len()
));
}
wd_hostname[..hostname_bytes.len()].copy_from_slice(hostname_bytes);
wd_hostname[..hostname_bytes.len().min(Whod::MAX_HOSTNAME_LEN)]
.copy_from_slice(hostname_bytes);
let mut wd_we = array::from_fn(|_| Whoent {
we_utmp: Outmp {
out_line: [0u8; Outmp::MAX_TTY_NAME_LEN],
out_name: [0u8; Outmp::MAX_USER_ID_LEN],
out_time: 0,
},
we_idle: 0,
let wd_sendtime = value
.sendtime
.timestamp()
.max(i32::MAX as i64)
.min(i32::MIN as i64) as i32;
let wd_recvtime = value.recvtime.map_or(0, |dt| {
dt.timestamp().max(i32::MAX as i64).min(i32::MIN as i64) as i32
});
for (i, user_entry) in value.users.into_iter().enumerate() {
if i >= Whod::MAX_WHOENTRIES {
break;
}
wd_we[i] = Whoent::try_from(user_entry)?;
}
let wd_boottime = value
.boot_time
.timestamp()
.max(i32::MAX as i64)
.min(i32::MIN as i64) as i32;
let wd_we = value
.users
.into_iter()
.map(Whoent::try_from)
.chain(std::iter::repeat(Ok(Whoent::zeroed())))
.take(Whod::MAX_WHOENTRIES)
.collect::<Result<Vec<Whoent>, String>>()?
.try_into()
.expect("Length mismatch, this should never happen");
Ok(Whod {
wd_vers: Whod::WHODVERSION,
wd_type: Whod::WHODTYPE_STATUS,
wd_pad: [0u8; 2],
wd_sendtime: value.sendtime.timestamp() as i32,
wd_recvtime: value.recvtime.map_or(0, |dt| dt.timestamp() as i32),
wd_sendtime,
wd_recvtime,
wd_hostname,
wd_loadav: [
value.load_average_5_min,
value.load_average_10_min,
value.load_average_15_min,
],
wd_boottime: value.boot_time.timestamp() as i32,
wd_boottime,
wd_we,
})
}

1
src/proto/write_protocol.rs
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@@ -0,0 +1 @@