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simplify and unify request parsing

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This commit is contained in:
Adam 2025-08-08 03:02:32 +01:00
parent 636ba8d7f5
commit a16aea2d11
4 changed files with 86 additions and 81 deletions
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8
src/bittorrent/info_hash.rs
View File

@ -8,6 +8,14 @@ pub struct InfoHash {
pub bytes: [u8; INFO_HASH_SIZE],
}
impl InfoHash {
pub fn from_bytes(buf: &[u8]) -> Option<InfoHash> {
Some(InfoHash {
bytes: buf.try_into().ok()?,
})
}
}
impl fmt::Display for InfoHash {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
const INFO_HASH_STR_LEN: usize = INFO_HASH_SIZE * 2;

6
src/bittorrent/peer.rs
View File

@ -8,6 +8,12 @@ pub struct PeerId {
}
impl PeerId {
pub fn from_bytes(buf: &[u8]) -> Option<PeerId> {
Some(PeerId {
bytes: buf.try_into().ok()?,
})
}
pub fn to_string_lossy(&self) -> String {
String::from_utf8_lossy(&self.bytes).into()
}

77
src/bittorrent/udp.rs
View File

@ -1,6 +1,6 @@
use std::{
io::{Cursor, Write},
net::{Ipv4Addr, Ipv6Addr, SocketAddrV4, SocketAddrV6},
net::{Ipv4Addr, SocketAddrV4, SocketAddrV6},
};
use crate::bittorrent::{
@ -9,18 +9,9 @@ use crate::bittorrent::{
protocol::{Action, Event},
};
pub const CONNECT_REQUEST_SIZE: usize = 16;
pub const MIN_ANNOUNCE_REQUEST_SIZE: usize = 98;
pub const MIN_SCRAPE_REQUEST_SIZE: usize = 36;
pub const MIN_CONNECTION_RESPONSE_SIZE: usize = 16;
pub const MIN_ANNOUNCE_RESPONSE_SIZE: usize = 20;
pub const MIN_SCRAPE_RESPONSE_SIZE: usize = 8;
pub const SCRAPE_RESPONSE_ENTRY_SIZE: usize = 12;
pub const IPV4_SIZE: usize = Ipv4Addr::BITS as usize / 8;
pub const IPV6_SIZE: usize = Ipv6Addr::BITS as usize / 8;
pub const PORT_SIZE: usize = size_of::<u16>();
pub const IPV4_ADDR_PAIR_SIZE: usize = IPV4_SIZE + PORT_SIZE;
pub const IPV6_ADDR_PAIR_SIZE: usize = IPV6_SIZE + PORT_SIZE;
#[derive(Debug)]
pub struct ConnectRequest {
@ -28,6 +19,19 @@ pub struct ConnectRequest {
pub transaction_id: i32,
}
impl ConnectRequest {
pub fn from_bytes(buf: &[u8]) -> Option<ConnectRequest> {
if buf.len() != CONNECT_REQUEST_SIZE {
return None;
}
Some(ConnectRequest {
protocol_id: i64::from_be_bytes(buf[0..8].try_into().ok()?),
transaction_id: i32::from_be_bytes(buf[12..16].try_into().ok()?),
})
}
}
#[derive(Debug)]
pub struct ConnectResponse {
pub transaction_id: i32,
@ -75,6 +79,38 @@ pub struct AnnounceRequest {
pub port: u16,
}
impl AnnounceRequest {
pub fn from_bytes(buf: &[u8]) -> Option<AnnounceRequest> {
if buf.len() < MIN_ANNOUNCE_REQUEST_SIZE {
return None;
}
Some(AnnounceRequest {
connection_id: i64::from_be_bytes(buf[0..8].try_into().ok()?),
transaction_id: i32::from_be_bytes(buf[12..16].try_into().ok()?),
info_hash: InfoHash::from_bytes(buf[16..36].try_into().ok()?)?,
peer_id: PeerId::from_bytes(buf[36..56].try_into().ok()?)?,
downloaded: i64::from_be_bytes(buf[56..64].try_into().ok()?),
left: i64::from_be_bytes(buf[64..72].try_into().ok()?),
uploaded: i64::from_be_bytes(buf[72..80].try_into().ok()?),
event: Event::from_i32(i32::from_be_bytes(buf[80..84].try_into().ok()?))?,
ipv4_address: if buf[84..88].iter().all(|b| *b == 0x00) {
None
} else {
Some(Ipv4Addr::from_bits(u32::from_be_bytes(
buf[84..88].try_into().ok()?,
)))
},
key: u32::from_be_bytes(buf[88..92].try_into().ok()?),
num_want: {
let want = i32::from_be_bytes(buf[92..96].try_into().ok()?);
if want < 0 { None } else { Some(want as u32) }
},
port: u16::from_be_bytes(buf[96..98].try_into().ok()?),
})
}
}
#[derive(Debug)]
pub enum AnnounceResponse {
V4(AnnounceResponseV4),
@ -158,6 +194,25 @@ pub struct ScrapeRequest {
pub info_hashes: Vec<InfoHash>,
}
impl ScrapeRequest {
pub fn from_bytes(buf: &[u8]) -> Option<ScrapeRequest> {
if buf.len() < MIN_SCRAPE_REQUEST_SIZE {
return None;
}
Some(ScrapeRequest {
connection_id: i64::from_be_bytes(buf[0..8].try_into().ok()?),
transaction_id: i32::from_be_bytes(buf[12..16].try_into().ok()?),
info_hashes: buf[16..]
.chunks_exact(20)
.map(|b| InfoHash {
bytes: b.try_into().unwrap(), // unwrap: `chunks_exact` guarantees the size
})
.collect(),
})
}
}
#[derive(Debug, Default)]
pub struct ScrapeStats {
/// Number of connected peers who have completed the download and are seeding

76
src/udp_server.rs
View File

@ -131,84 +131,20 @@ fn try_parse_packet(buf: &[u8]) -> Option<UdpRequest> {
}
fn try_parse_connect(buf: &[u8]) -> Option<ConnectRequest> {
// Buffer length is checked to be at least 16 in `try_parse_packet`
let conn = ConnectRequest::from_bytes(buf)?;
let protocol_id: i64 = i64::from_be_bytes(buf[0..8].try_into().ok()?);
if protocol_id != UDP_MAGIC {
// Disregard the request immediately if `protocol_id` is not the valid magic number
if conn.protocol_id != UDP_MAGIC {
return None;
}
Some(ConnectRequest {
protocol_id: protocol_id,
transaction_id: i32::from_be_bytes(buf[12..16].try_into().ok()?),
})
Some(conn)
}
fn try_parse_announce(buf: &[u8]) -> Option<AnnounceRequest> {
if buf.len() < MIN_ANNOUNCE_REQUEST_SIZE {
return None;
}
let connection_id: i64 = i64::from_be_bytes(buf[0..8].try_into().ok()?);
let transaction_id: i32 = i32::from_be_bytes(buf[12..16].try_into().ok()?);
let info_hash: InfoHash = InfoHash {
bytes: buf[16..36].try_into().ok()?,
};
let peer_id: PeerId = PeerId {
bytes: buf[36..56].try_into().unwrap_or_default(),
};
let downloaded: i64 = i64::from_be_bytes(buf[56..64].try_into().ok()?);
let left: i64 = i64::from_be_bytes(buf[64..72].try_into().ok()?);
let uploaded: i64 = i64::from_be_bytes(buf[72..80].try_into().ok()?);
let event: Event = Event::from_i32(i32::from_be_bytes(buf[80..84].try_into().ok()?))?;
let ip_addr: Option<Ipv4Addr> = if buf[84..88].iter().all(|b| *b == 0x00) {
None
} else {
Some(Ipv4Addr::from_bits(u32::from_be_bytes(
buf[84..88].try_into().ok()?,
)))
};
let key: u32 = u32::from_be_bytes(buf[88..92].try_into().ok()?);
let num_want: Option<u32> = {
let want = i32::from_be_bytes(buf[92..96].try_into().ok()?);
if want < 0 { None } else { Some(want as u32) }
};
let port: u16 = u16::from_be_bytes(buf[96..98].try_into().ok()?);
Some(AnnounceRequest {
connection_id: connection_id,
transaction_id: transaction_id,
info_hash: info_hash,
peer_id: peer_id,
downloaded: downloaded,
left: left,
uploaded: uploaded,
event: event,
ipv4_address: ip_addr,
key: key,
num_want: num_want,
port: port,
})
AnnounceRequest::from_bytes(buf)
}
fn try_parse_scrape(buf: &[u8]) -> Option<ScrapeRequest> {
if buf.len() < MIN_SCRAPE_REQUEST_SIZE {
return None;
}
let connection_id: i64 = i64::from_be_bytes(buf[0..8].try_into().ok()?);
let transaction_id: i32 = i32::from_be_bytes(buf[12..16].try_into().ok()?);
let info_hashes: Vec<InfoHash> = buf[16..]
.chunks_exact(20)
.map(|b| InfoHash {
bytes: b.try_into().unwrap(), // unwrap: `chunks_exact` guarantees the size
})
.collect();
Some(ScrapeRequest {
connection_id: connection_id,
transaction_id: transaction_id,
info_hashes: info_hashes,
})
ScrapeRequest::from_bytes(buf)
}