fix subnet proxy deadloop (#1492)

* use LPM to determine subnet proxy dst.
* never allow subnet proxy traffic sending to self.

Cargo.lock

@@ -1273,9 +1273,9 @@ dependencies = [
 
 [[package]]
 name = "cidr"
-version = "0.2.3"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6bdf600c45bd958cf2945c445264471cca8b6c8e67bc87b71affd6d7e5682621"
+checksum = "bd1b64030216239a2e7c364b13cd96a2097ebf0dfe5025f2dedee14a23f2ab60"
 dependencies = [
  "serde",
 ]
@@ -2176,6 +2176,7 @@ dependencies = [
  "petgraph 0.8.1",
  "pin-project-lite",
  "pnet",
+ "prefix-trie",
  "prost",
  "prost-build",
  "prost-reflect",
@@ -6182,6 +6183,7 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "85cf4c7c25f1dd66c76b451e9041a8cfce26e4ca754934fa7aed8d5a59a01d20"
 dependencies = [
+ "cidr",
  "ipnet",
  "num-traits",
 ]
@@ -7507,10 +7509,11 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.207"
+version = "1.0.228"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5665e14a49a4ea1b91029ba7d3bca9f299e1f7cfa194388ccc20f14743e784f2"
+checksum = "9a8e94ea7f378bd32cbbd37198a4a91436180c5bb472411e48b5ec2e2124ae9e"
 dependencies = [
+ "serde_core",
  "serde_derive",
 ]
 
@@ -7526,10 +7529,19 @@ dependencies = [
 ]
 
 [[package]]
-name = "serde_derive"
-version = "1.0.207"
+name = "serde_core"
+version = "1.0.228"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6aea2634c86b0e8ef2cfdc0c340baede54ec27b1e46febd7f80dffb2aa44a00e"
+checksum = "41d385c7d4ca58e59fc732af25c3983b67ac852c1a25000afe1175de458b67ad"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.228"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
 dependencies = [
  "proc-macro2",
  "quote",