Add cache invalidation to the hot cache. Whenever an IP mapping

changes, the cache is invalidated - meaning it will re-cache
the correct values.

src/rust/lqos_sys/src/ip_mapping/mod.rs

@@ -36,6 +36,7 @@ pub fn add_ip_to_tc(
   let mut value =
     IpHashData { cpu: ip_to_add.cpu, tc_handle: ip_to_add.handle() };
   bpf_map.insert_or_update(&mut key, &mut value)?;
+  clear_hot_cache()?;
   Ok(())
 }
 
@@ -56,6 +57,7 @@ pub fn del_ip_from_tc(address: &str, upload: bool) -> Result<()> {
   let ip = XdpIpAddress::from_ip(ip);
   let mut key = IpHashKey { prefixlen: ip_to_add.prefix, address: ip.0 };
   bpf_map.delete(&mut key)?;
+  clear_hot_cache()?;
   Ok(())
 }
 
@@ -71,6 +73,8 @@ pub fn clear_ips_from_tc() -> Result<()> {
   )?;
   bpf_map.clear()?;
 
+  clear_hot_cache()?;
+  
   Ok(())
 }
 
@@ -89,3 +93,12 @@ pub fn list_mapped_ips() -> Result<Vec<(IpHashKey, IpHashData)>> {
 
   Ok(raw)
 }
+
+/// Clears the "hot cache", which should be done whenever you change the IP
+/// mappings - because otherwise cached data will keep going to the previous
+/// destinations.
+fn clear_hot_cache() -> Result<()> {
+  let mut bpf_map = BpfMap::<XdpIpAddress, IpHashData>::from_path("/sys/fs/bpf/ip_to_cpu_and_tc_hotcache")?;
+  bpf_map.clear()?;
+  Ok(())
+}