More documentation!

Signed-off-by: Levente Kurusa <lkurusa@acm.org>

src/net_cls.rs

@@ -1,17 +1,24 @@
-/* Network classifier controller */
+//! This module contains the implementation of the `net_cls` cgroup subsystem.
+//! 
+//! See the Kernel's documentation for more information about this subsystem, found at:
+//!  [Documentation/cgroup-v1/net_cls.txt](https://www.kernel.org/doc/Documentation/cgroup-v1/net_cls.txt)
 use std::path::PathBuf;
 use std::io::{Read, Write};
 use std::fs::File;
 
 use {NetworkResources, Controllers, Controller, Resources, ControllIdentifier, Subsystem};
 
+/// A controller that allows controlling the `net_cls` subsystem of a Cgroup.
+///
+/// In esssence, using the `net_cls` controller, one can attach a custom class to the network
+/// packets emitted by the control group's tasks. This can then later be used in iptables to have
+/// custom firewall rules, QoS, etc.
 #[derive(Debug, Clone)]
 pub struct NetClsController {
     base: PathBuf,
     path: PathBuf,
 }
 
-
 impl Controller for NetClsController {
     fn control_type(self: &Self) -> Controllers { Controllers::NetCls }
     fn get_path<'a>(self: &'a Self) -> &'a PathBuf { &self.path }
@@ -55,6 +62,7 @@ fn read_u64_from(mut file: File) -> Option<u64> {
 }
 
 impl NetClsController {
+    /// Constructs a new `NetClsController` with `oroot` serving as the root of the control group.
     pub fn new(oroot: PathBuf) -> Self {
         let mut root = oroot;
         root.push(Self::controller_type().to_string());
@@ -63,6 +71,8 @@ impl NetClsController {
             path: root,
         }
     }
+    
+    /// Set the network class id of the outgoing packets of the control group's tasks.
     pub fn set_class(self: &Self, class: u64) {
         self.open_path("net_cls.classid", true).and_then(|mut file| {
             let s = format!("{:#08X}", class);
@@ -70,6 +80,7 @@ impl NetClsController {
         });
     }
 
+    /// Get the network class id of the outgoing packets of the control group's tasks.
     pub fn get_class(self: &Self) -> u64 {
         self.open_path("net_cls.classid", false).and_then(|file| {
             read_u64_from(file)