cleanup: fix unused variable + unnecessary mut warnings (7 total)

- router/mod.rs: 4x |mut b| → |b| (&mut [u8] is already mutable)
- scheme/icmp.rs: handle_recvmsg stub params → _file, _how, _flags
- scheme/ip.rs: handle_recvmsg stub params → _file, _how, _flags
- scheme/socket.rs: get_sock_opt default + msg_send ctx → _ prefixed
- scheme/tun.rs: loop name → _name

netstack/src/router/mod.rs

@@ -138,14 +138,14 @@ impl Router {
                 RouteType::Unreachable => {
                     if let Some(error_pkt) = icmp_error::build_icmpv4_port_unreachable(packet) {
                         let _ = self.rx_buffer.enqueue(error_pkt.len(), ())
-                            .map(|mut b| b.copy_from_slice(&error_pkt));
+                            .map(|b| b.copy_from_slice(&error_pkt));
                     }
                     continue;
                 }
                 RouteType::Prohibit => {
                     if let Some(error_pkt) = icmp_error::build_icmpv4_port_unreachable(packet) {
                         let _ = self.rx_buffer.enqueue(error_pkt.len(), ())
-                            .map(|mut b| b.copy_from_slice(&error_pkt));
+                            .map(|b| b.copy_from_slice(&error_pkt));
                     }
                     continue;
                 }
@@ -312,14 +312,14 @@ impl Router {
                         RouteType::Unreachable => {
                             if let Some(error_pkt) = icmp_error::build_icmpv4_port_unreachable(&packet_buf) {
                                 let _ = self.tx_buffer.enqueue(error_pkt.len(), ())
-                                    .map(|mut b| b.copy_from_slice(&error_pkt));
+                                    .map(|b| b.copy_from_slice(&error_pkt));
                             }
                             continue;
                         }
                         RouteType::Prohibit => {
                             if let Some(error_pkt) = icmp_error::build_icmpv4_port_unreachable(&packet_buf) {
                                 let _ = self.tx_buffer.enqueue(error_pkt.len(), ())
-                                    .map(|mut b| b.copy_from_slice(&error_pkt));
+                                    .map(|b| b.copy_from_slice(&error_pkt));
                             }
                             continue;
                         }

netstack/src/scheme/icmp.rs

@@ -269,9 +269,9 @@ impl<'a> SchemeSocket for IcmpSocket<'a> {
 
     fn handle_recvmsg(
         &mut self,
-        file: &mut SchemeFile<Self>,
-        how: &mut [u8],
-        flags: usize,
+        _file: &mut SchemeFile<Self>,
+        _how: &mut [u8],
+        _flags: usize,
     ) -> SyscallResult<usize> {
         return Err(SyscallError::new(syscall::EOPNOTSUPP));
     }

netstack/src/scheme/ip.rs

@@ -146,9 +146,9 @@ impl<'a> SchemeSocket for RawSocket<'a> {
 
     fn handle_recvmsg(
         &mut self,
-        file: &mut SchemeFile<Self>,
-        how: &mut [u8],
-        flags: usize,
+        _file: &mut SchemeFile<Self>,
+        _how: &mut [u8],
+        _flags: usize,
     ) -> SyscallResult<usize> {
         return Err(SyscallError::new(syscall::EOPNOTSUPP));
     }

netstack/src/scheme/socket.rs

@@ -253,9 +253,9 @@ where
 
 fn get_sock_opt(
         &self,
-        file: &SchemeFile<Self>,
-        name: usize,
-        buf: &mut [u8],
+        _file: &SchemeFile<Self>,
+        _name: usize,
+        _buf: &mut [u8],
     ) -> SyscallResult<usize> {
         Err(SyscallError::new(syscall::ENOPROTOOPT))
     }
@@ -448,7 +448,7 @@ where
         fd: usize,
         payload: &mut [u8],
         metadata: &[u64],
-        ctx: &CallerCtx,
+        _ctx: &CallerCtx,
     ) -> SyscallResult<usize> {
         // metadata to Vec<u8>
         let Some(verb) = SocketCall::try_from_raw(metadata[0] as usize) else {

netstack/src/scheme/tun.rs

@@ -116,7 +116,7 @@ impl TunScheme {
                 _ => {}
             }
         }
-        for (name, dev) in &self.inner.devices {
+        for (_name, dev) in &self.inner.devices {
             let mut written = Vec::new();
             {
                 let mut rx = dev.tx.borrow_mut();