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Optimize memory allocation logic when constructing packet buffer #78

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Merged
ssrlive merged 1 commit into from
Nov 17, 2025
Merged

Optimize memory allocation logic when constructing packet buffer #78

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17 changes: 14 additions & 3 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,10 @@ const TUN_PROTO_IP6: [u8; 2] = [0x00, 0x0A];
#[cfg(any(target_os = "macos", target_os = "ios"))]
const TUN_PROTO_IP4: [u8; 2] = [0x00, 0x02];

/// Minimum MTU required for IPv6 (per RFC 8200 §5: MTU ≥ 1280).
/// Also satisfies IPv4 minimum MTU (RFC 791 §3.1: 68 bytes).
const MIN_MTU: u16 = 1280;

/// Configuration for the IP stack.
///
/// This structure holds configuration parameters that control the behavior of the IP stack,
Expand All @@ -61,7 +65,7 @@ const TUN_PROTO_IP4: [u8; 2] = [0x00, 0x02];
#[non_exhaustive]
pub struct IpStackConfig {
/// Maximum Transmission Unit (MTU) size in bytes.
/// Default is `u16::MAX` (65535).
/// Default is `MIN_MTU` (1280).
pub mtu: u16,
/// Whether to include packet information headers (Unix platforms only).
/// Default is `false`.
Expand All @@ -76,7 +80,7 @@ pub struct IpStackConfig {
impl Default for IpStackConfig {
fn default() -> Self {
IpStackConfig {
mtu: u16::MAX,
mtu: MIN_MTU,
packet_information: false,
tcp_config: Arc::new(TcpConfig::default()),
udp_timeout: Duration::from_secs(30),
Expand Down Expand Up @@ -300,9 +304,16 @@ fn run<Device: AsyncRead + AsyncWrite + Unpin + Send + 'static>(
let (session_remove_tx, mut session_remove_rx) = mpsc::unbounded_channel::<NetworkTuple>();
let pi = config.packet_information;
let offset = if pi && cfg!(unix) { 4 } else { 0 };
let mut buffer = vec![0_u8; u16::MAX as usize + offset];
let mut buffer = vec![0_u8; config.mtu as usize + offset];
let (up_pkt_sender, mut up_pkt_receiver) = mpsc::unbounded_channel::<NetworkPacket>();

if config.mtu < MIN_MTU {
log::warn!(
"the MTU in the configuration ({}) below the MIN_MTU (1280) can cause problems.",
config.mtu
);
}

tokio::spawn(async move {
loop {
select! {
Expand Down