Pick a free routing table id

1 files changed, 23 insertions, 19 deletions

diff --git a/talpid-core/src/split.rs b/talpid-core/src/split.rs
index d72d41cc8f..090a497c9a 100644
--- a/talpid-core/src/split.rs
+++ b/talpid-core/src/split.rs
@@ -17,7 +17,6 @@ pub const NETCLS_CLASSID: u32 = 0x4d9f41;
 pub const MARK: i32 = 0xf41;
 
 const CGROUP_NAME: &str = "mullvad-exclusions";
-static mut ROUTING_TABLE_ID: i32 = 19;
 const ROUTING_TABLE_NAME: &str = "mullvad_exclusions";
 const RT_TABLES_PATH: &str = "/etc/iproute2/rt_tables";
 
@@ -99,19 +98,20 @@ fn get_default_route() -> Result<DefaultRoute, Error> {
 }
 
 /// Manage routing for split tunneling cgroup.
-pub struct SplitTunnel;
+pub struct SplitTunnel {
+    table_id: i32,
+}
 
 impl SplitTunnel {
     /// Object that allows specified applications to not pass through the tunnel
     pub fn new() -> Result<SplitTunnel, Error> {
-        Self::initialize_routing_table()?;
-        Ok(SplitTunnel {})
+        let mut tunnel = SplitTunnel { table_id: 0 };
+        tunnel.initialize_routing_table()?;
+        Ok(tunnel)
     }
 
     /// Set up policy-based routing for marked packets.
-    fn initialize_routing_table() -> Result<(), Error> {
-        // TODO: ensure the ID does not conflict with that of another table
-
+    fn initialize_routing_table(&mut self) -> Result<(), Error> {
         // Add routing table to /etc/iproute2/rt_tables, if it does not exist
 
         let mut file = fs::OpenOptions::new()
@@ -123,6 +123,8 @@ impl SplitTunnel {
         let buf_reader = BufReader::new(file.try_clone().map_err(Error::RoutingTableSetup)?);
         let expression = Regex::new(r"^\s*(\d+)\s+(\w+)").unwrap();
 
+        let mut used_ids = Vec::<i32>::new();
+
         for line in buf_reader.lines() {
             let line = line.map_err(Error::RoutingTableSetup)?;
             if let Some(captures) = expression.captures(&line) {
@@ -134,24 +136,26 @@ impl SplitTunnel {
                     .expect("Table ID does not fit i32");
                 let table_name = captures.get(2).unwrap().as_str();
 
-                // Already added
                 if table_name == ROUTING_TABLE_NAME {
-                    if table_id != unsafe { ROUTING_TABLE_ID } {
-                        unsafe { ROUTING_TABLE_ID = table_id };
-                    }
-
+                    // The table has already been added
+                    self.table_id = table_id;
                     return Ok(());
                 }
+
+                used_ids.push(table_id);
+            }
+        }
+
+        used_ids.sort_unstable();
+        for id in 1..256 {
+            if used_ids.binary_search(&id).is_err() {
+                // Assign a free id to the table
+                self.table_id = id;
+                break;
             }
         }
 
-        write!(
-            file,
-            "{} {}",
-            unsafe { ROUTING_TABLE_ID },
-            ROUTING_TABLE_NAME
-        )
-        .map_err(Error::RoutingTableSetup)
+        write!(file, "{} {}", self.table_id, ROUTING_TABLE_NAME).map_err(Error::RoutingTableSetup)
     }
 
     /// Reset the split-tunneling routing table to its default state