diff --git a/crates/shadowsocks-service/src/local/socks/client/socks5/udp_client.rs b/crates/shadowsocks-service/src/local/socks/client/socks5/udp_client.rs
index 48047075..4eed1b18 100644
--- a/crates/shadowsocks-service/src/local/socks/client/socks5/udp_client.rs
+++ b/crates/shadowsocks-service/src/local/socks/client/socks5/udp_client.rs
@@ -70,7 +70,7 @@ impl Socks5UdpClient {
         send_buf.put_slice(buf);
 
         let n = self.socket.send(&send_buf).await?;
-        Ok(if n <= header_len { 0 } else { n - header_len })
+        Ok(n.saturating_sub(header_len))
     }
 
     /// Returns a future that receives a single datagram on the socket. On success, the future resolves to the number of bytes read and the origin.
diff --git a/crates/shadowsocks/src/config.rs b/crates/shadowsocks/src/config.rs
index 852ffc7a..c3f4597c 100644
--- a/crates/shadowsocks/src/config.rs
+++ b/crates/shadowsocks/src/config.rs
@@ -129,7 +129,7 @@ impl FromStr for Mode {
 
 struct ModeVisitor;
 
-impl<'de> serde::de::Visitor<'de> for ModeVisitor {
+impl serde::de::Visitor<'_> for ModeVisitor {
     type Value = Mode;
 
     fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
@@ -1078,7 +1078,7 @@ impl Display for ServerAddr {
 
 struct ServerAddrVisitor;
 
-impl<'de> serde::de::Visitor<'de> for ServerAddrVisitor {
+impl serde::de::Visitor<'_> for ServerAddrVisitor {
     type Value = ServerAddr;
 
     fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
@@ -1259,7 +1259,7 @@ impl Display for ManagerAddr {
 
 struct ManagerAddrVisitor;
 
-impl<'de> serde::de::Visitor<'de> for ManagerAddrVisitor {
+impl serde::de::Visitor<'_> for ManagerAddrVisitor {
     type Value = ManagerAddr;
 
     fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
diff --git a/crates/shadowsocks/src/dns_resolver/resolver.rs b/crates/shadowsocks/src/dns_resolver/resolver.rs
index dfd78b45..e42e79c3 100644
--- a/crates/shadowsocks/src/dns_resolver/resolver.rs
+++ b/crates/shadowsocks/src/dns_resolver/resolver.rs
@@ -315,7 +315,7 @@ impl DnsResolver {
             }
         }
 
-        impl<'x, 'y> Drop for ResolverLogger<'x, 'y> {
+        impl Drop for ResolverLogger<'_, '_> {
             fn drop(&mut self) {
                 match self.start_time {
                     Some(start_time) => {
diff --git a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/mod.rs b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/mod.rs
index 56ae3a01..883986ae 100644
--- a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/mod.rs
+++ b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/mod.rs
@@ -86,7 +86,7 @@ pub enum TcpRequestHeaderRef<'a> {
     Aead2022(Aead2022TcpRequestHeaderRef<'a>),
 }
 
-impl<'a> TcpRequestHeaderRef<'a> {
+impl TcpRequestHeaderRef<'_> {
     pub fn write_to_buf<B: BufMut>(&self, buf: &mut B) {
         match *self {
             TcpRequestHeaderRef::Stream(ref h) => h.write_to_buf(buf),
diff --git a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v1.rs b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v1.rs
index 7c002923..2eaa81d3 100644
--- a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v1.rs
+++ b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v1.rs
@@ -33,7 +33,7 @@ pub struct StreamTcpRequestHeaderRef<'a> {
     pub addr: &'a Address,
 }
 
-impl<'a> StreamTcpRequestHeaderRef<'a> {
+impl StreamTcpRequestHeaderRef<'_> {
     pub fn write_to_buf<B: BufMut>(&self, buf: &mut B) {
         self.addr.write_to_buf(buf);
     }
diff --git a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v2.rs b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v2.rs
index 469488d5..656306d5 100644
--- a/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v2.rs
+++ b/crates/shadowsocks/src/relay/tcprelay/proxy_stream/protocol/v2.rs
@@ -72,7 +72,7 @@ pub struct Aead2022TcpRequestHeaderRef<'a> {
     pub padding_size: u16,
 }
 
-impl<'a> Aead2022TcpRequestHeaderRef<'a> {
+impl Aead2022TcpRequestHeaderRef<'_> {
     pub fn write_to_buf<B: BufMut>(&self, buf: &mut B) {
         assert!(
             self.padding_size as usize <= MAX_PADDING_SIZE,
diff --git a/crates/shadowsocks/src/relay/tcprelay/utils.rs b/crates/shadowsocks/src/relay/tcprelay/utils.rs
index 0b267ce1..e37d8c66 100644
--- a/crates/shadowsocks/src/relay/tcprelay/utils.rs
+++ b/crates/shadowsocks/src/relay/tcprelay/utils.rs
@@ -240,7 +240,7 @@ where
     }
 }
 
-impl<'a, A, B> Future for CopyBidirectional<'a, A, B>
+impl<A, B> Future for CopyBidirectional<'_, A, B>
 where
     A: AsyncRead + AsyncWrite + Unpin + ?Sized,
     B: AsyncRead + AsyncWrite + Unpin + ?Sized,
diff --git a/crates/shadowsocks/src/relay/udprelay/compat.rs b/crates/shadowsocks/src/relay/udprelay/compat.rs
index fd17f28f..8dec3e29 100644
--- a/crates/shadowsocks/src/relay/udprelay/compat.rs
+++ b/crates/shadowsocks/src/relay/udprelay/compat.rs
@@ -81,7 +81,7 @@ pub struct RecvFut<'a, S: DatagramReceive + ?Sized> {
     buf: &'a mut [u8],
 }
 
-impl<'a, S: DatagramReceive + ?Sized> Future for RecvFut<'a, S> {
+impl<S: DatagramReceive + ?Sized> Future for RecvFut<'_, S> {
     type Output = io::Result<usize>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
@@ -101,7 +101,7 @@ pub struct RecvFromFut<'a, S: DatagramReceive + ?Sized> {
     buf: &'a mut [u8],
 }
 
-impl<'a, S: DatagramReceive + ?Sized> Future for RecvFromFut<'a, S> {
+impl<S: DatagramReceive + ?Sized> Future for RecvFromFut<'_, S> {
     type Output = io::Result<(usize, SocketAddr)>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
@@ -118,7 +118,7 @@ pub struct RecvReadyFut<'a, S: DatagramReceive + ?Sized> {
     io: &'a S,
 }
 
-impl<'a, S: DatagramReceive + ?Sized> Future for RecvReadyFut<'a, S> {
+impl<S: DatagramReceive + ?Sized> Future for RecvReadyFut<'_, S> {
     type Output = io::Result<()>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
@@ -132,7 +132,7 @@ pub struct SendFut<'a, S: DatagramSend + ?Sized> {
     buf: &'a [u8],
 }
 
-impl<'a, S: DatagramSend + ?Sized> Future for SendFut<'a, S> {
+impl<S: DatagramSend + ?Sized> Future for SendFut<'_, S> {
     type Output = io::Result<usize>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
@@ -147,7 +147,7 @@ pub struct SendToFut<'a, S: DatagramSend + ?Sized> {
     buf: &'a [u8],
 }
 
-impl<'a, S: DatagramSend + ?Sized> Future for SendToFut<'a, S> {
+impl<S: DatagramSend + ?Sized> Future for SendToFut<'_, S> {
     type Output = io::Result<usize>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
@@ -160,7 +160,7 @@ pub struct SendReadyFut<'a, S: DatagramSend + ?Sized> {
     io: &'a S,
 }
 
-impl<'a, S: DatagramSend + ?Sized> Future for SendReadyFut<'a, S> {
+impl<S: DatagramSend + ?Sized> Future for SendReadyFut<'_, S> {
     type Output = io::Result<()>;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {