improve performance of route generation (#914)

this may fix following problem:

1. cpu 100% when large number of nodes in network.
2. high cpu usage when large number of foreign networks.
3. packet loss when new node enters/exits.
4. old routes not cleand and show as an obloleted entry.

Cargo.toml

@@ -16,5 +16,5 @@ panic = "unwind"
 panic = "abort"
 lto = true
 codegen-units = 1
-opt-level = 'z'
+opt-level = 3
 strip = true