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udp: ConnectionValidator: add documentation

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This commit is contained in:
Joakim Frostegård 2022-04-14 22:08:57 +02:00
parent 10cb0849d6
commit 1e5b98bcf6
1 changed files with 10 additions and 4 deletions
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14
aquatic_udp/src/common.rs
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@ -17,6 +17,13 @@ use crate::config::Config;
pub const MAX_PACKET_SIZE: usize = 8192;
/// HMAC (BLAKE3) based ConnectionID creator and validator
///
/// Structure of created ConnectionID (bytes making up inner i64):
/// - &[0..4]: connection expiration time as number of seconds after
/// ConnectionValidator instance was created, encoded as u32 bytes
/// - &[4..8]: truncated keyed BLAKE3 hash of above 4 bytes and octets of
/// client IP address
#[derive(Clone)]
pub struct ConnectionValidator {
start_time: Instant,
@ -25,6 +32,8 @@ pub struct ConnectionValidator {
}
impl ConnectionValidator {
/// Create new instance. Must be created once and cloned if used in several
/// threads.
pub fn new(config: &Config) -> anyhow::Result<Self> {
let mut key = [0; 32];
@ -54,7 +63,7 @@ impl ConnectionValidator {
) -> bool {
let valid_until = connection_id.0.to_ne_bytes()[..4].try_into().unwrap();
// Check that recreating ConnectionId with same inputs yields identical HMAC.
// Check that recreating ConnectionId with same inputs yields identical hash.
//
// I expect i64 comparison to be be constant-time.
if connection_id != self.create_connection_id_inner(valid_until, source_addr) {
@ -69,9 +78,6 @@ impl ConnectionValidator {
valid_until: [u8; 4],
source_addr: CanonicalSocketAddr,
) -> ConnectionId {
// The first 4 bytes is number of seconds since server start until
// connection is no longer valid. The last 4 is the truncated message
// authentication code.
let mut connection_id_bytes = [0u8; 8];
(&mut connection_id_bytes[..4]).copy_from_slice(&valid_until);