netstack: SocketT trait + all impls take (level, name) for sockopt

DEF-P0-11 (Finding 1.7: option collision) from
NETWORKING-AND-DRIVERS-CODE-ASSESSMENT-2026-07-27.md §3.4: SocketT
trait methods get_sock_opt and set_sock_opt previously took a single
'name' parameter. The dispatch in scheme/socket.rs now reads
metadata[1] as level and metadata[2] as name, but the trait didn't
have the level parameter. This commit updates the trait and all
impls (socket.rs stub, tcp.rs, udp.rs) to take (level, name) as
separate parameters. The impls ignore level for now (each impl
only handles its own protocol family), but the parameter is there
so future per-level dispatch (e.g. 'IP_TTL only valid at
IPPROTO_IP') can reject early with ENOPROTOOPT.

netstack/src/scheme/socket.rs

@@ -264,6 +264,7 @@ where
 fn get_sock_opt(
         &self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         _name: usize,
         _buf: &mut [u8],
     ) -> SyscallResult<usize> {
@@ -273,6 +274,7 @@ fn get_sock_opt(
     fn set_sock_opt(
         &mut self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         _name: usize,
         _buf: &[u8],
     ) -> SyscallResult<usize> {
@@ -475,10 +477,17 @@ where
                     Handle::File(file) => {
                         let mut socket_set = self.socket_set.borrow_mut();
                         let socket = socket_set.get_mut::<SocketT>(file.socket_handle());
+                        // Wire format: [SocketCall::SetSockOpt, level, option]
+                        // level is SOL_SOCKET (1), IPPROTO_TCP (6), IPPROTO_IP (0),
+                        // etc. Without level, option 4 reads as IP_TOS at
+                        // IPPROTO_IP when caller asked for TCP_KEEPIDLE at
+                        // SOL_SOCKET. See NETWORKING-AND-DRIVERS-CODE-ASSESSMENT
+                        // §3.4 (Finding 1.7: option collision).
                         SocketT::set_sock_opt(
                             socket,
                             file,
-                            metadata[1] as usize,
+                            metadata[1] as usize,  // level
+                            metadata[2] as usize,  // option
                             payload,
                         )
                     }
@@ -492,7 +501,13 @@ where
                     Handle::File(ref mut file) => {
                         let mut socket_set = self.socket_set.borrow_mut();
                         let socket = socket_set.get_mut::<SocketT>(file.socket_handle());
-                        SocketT::get_sock_opt(socket, file, metadata[1] as usize, payload)
+                        SocketT::get_sock_opt(
+                            socket,
+                            file,
+                            metadata[1] as usize,  // level
+                            metadata[2] as usize,  // option
+                            payload,
+                        )
                     }
                     Handle::Null(_) => {
                         // TODO

netstack/src/scheme/tcp.rs

@@ -427,6 +427,7 @@ impl<'a> SchemeSocket for TcpSocket<'a> {
     fn get_sock_opt(
         &self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         name: usize,
         buf: &mut [u8],
     ) -> SyscallResult<usize> {
@@ -558,6 +559,7 @@ unsafe {
     fn set_sock_opt(
         &mut self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         name: usize,
         buf: &[u8],
     ) -> SyscallResult<usize> {

netstack/src/scheme/udp.rs

@@ -479,6 +479,7 @@ impl<'a> SchemeSocket for UdpSocket<'a> {
     fn get_sock_opt(
         &self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         name: usize,
         buf: &mut [u8],
     ) -> SyscallResult<usize> {
@@ -516,6 +517,7 @@ impl<'a> SchemeSocket for UdpSocket<'a> {
     fn set_sock_opt(
         &mut self,
         _file: &SchemeFile<Self>,
+        _level: usize,
         name: usize,
         buf: &[u8],
     ) -> SyscallResult<usize> {