Increase subnet range for IPPR (#4487)

* Increase subnet range for IPPR

* Fix for IPv6

* Fix range

* Add unit test

* Bump version

common/ip-packet-requests/src/lib.rs

@@ -9,7 +9,8 @@ pub mod response;
 // version 3: initial version
 // version 4: IPv6 support
 // version 5: Add severity level to info response
-pub const CURRENT_VERSION: u8 = 5;
+// version 6: Increase the available IPs
+pub const CURRENT_VERSION: u8 = 6;
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub struct IpPair {

service-providers/ip-packet-router/src/constants.rs

@@ -4,10 +4,10 @@ use std::time::Duration;
 // The interface used to route traffic
 pub const TUN_BASE_NAME: &str = "nymtun";
 pub const TUN_DEVICE_ADDRESS_V4: Ipv4Addr = Ipv4Addr::new(10, 0, 0, 1);
-pub const TUN_DEVICE_NETMASK_V4: Ipv4Addr = Ipv4Addr::new(255, 255, 255, 0);
+pub const TUN_DEVICE_NETMASK_V4: Ipv4Addr = Ipv4Addr::new(255, 255, 0, 0);
 pub const TUN_DEVICE_ADDRESS_V6: Ipv6Addr = Ipv6Addr::new(0x2001, 0xdb8, 0xa160, 0, 0, 0, 0, 0x1); // 2001:db8:a160::1
 
-pub const TUN_DEVICE_NETMASK_V6: &str = "120";
+pub const TUN_DEVICE_NETMASK_V6: &str = "112";
 
 // We routinely check if any clients needs to be disconnected at this interval
 pub(crate) const DISCONNECT_TIMER_INTERVAL: Duration = Duration::from_secs(10);

service-providers/ip-packet-router/src/util/generate_new_ip.rs

@@ -6,12 +6,13 @@ use crate::constants::{TUN_DEVICE_ADDRESS_V4, TUN_DEVICE_ADDRESS_V6};
 
 // Find an available IP address in self.connected_clients
 // TODO: make this nicer
-fn generate_random_ips_within_subnet() -> IpPair {
-    let mut rng = rand::thread_rng();
-    // Generate a random number in the range 1-254
-    let last_octet = rand::Rng::gen_range(&mut rng, 1..=254);
-    let ipv4 = Ipv4Addr::new(10, 0, 0, last_octet);
-    let ipv6 = Ipv6Addr::new(0x2001, 0x0db8, 0xa160, 0, 0, 0, 0, last_octet as u16);
+fn generate_random_ips_within_subnet<R: rand::Rng>(rng: &mut R) -> IpPair {
+    // Generate a random number in the range 2-65535
+    let last_bytes: u16 = rand::Rng::gen_range(rng, 2..=65534);
+    let before_last_byte = (last_bytes >> 8) as u8;
+    let last_byte = (last_bytes & 255) as u8;
+    let ipv4 = Ipv4Addr::new(10, 0, before_last_byte, last_byte);
+    let ipv6 = Ipv6Addr::new(0x2001, 0x0db8, 0xa160, 0, 0, 0, 0, last_bytes);
     IpPair::new(ipv4, ipv6)
 }
 
@@ -32,7 +33,8 @@ pub(crate) fn find_new_ips<T>(
     connected_clients_ipv4: &HashMap<Ipv4Addr, T>,
     connected_clients_ipv6: &HashMap<Ipv6Addr, T>,
 ) -> Option<IpPair> {
-    let mut new_ips = generate_random_ips_within_subnet();
+    let mut rng = rand::thread_rng();
+    let mut new_ips = generate_random_ips_within_subnet(&mut rng);
     let mut tries = 0;
     let tun_ips = IpPair::new(TUN_DEVICE_ADDRESS_V4, TUN_DEVICE_ADDRESS_V6);
 
@@ -42,7 +44,7 @@ pub(crate) fn find_new_ips<T>(
         tun_ips,
         new_ips,
     ) {
-        new_ips = generate_random_ips_within_subnet();
+        new_ips = generate_random_ips_within_subnet(&mut rng);
         tries += 1;
         if tries > 100 {
             return None;
@@ -50,3 +52,23 @@ pub(crate) fn find_new_ips<T>(
     }
     Some(new_ips)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::collections::HashSet;
+
+    #[test]
+    fn verify_ip_generation() {
+        let mut map = HashSet::with_capacity(65533);
+        let mut rng = rand::rngs::mock::StepRng::new(0, 65540);
+        for _ in 2..65535 {
+            let pair = generate_random_ips_within_subnet(&mut rng);
+            println!("{:?}", pair);
+            assert!(!map.contains(&pair));
+            map.insert(pair);
+        }
+        let pair = generate_random_ips_within_subnet(&mut rng);
+        assert!(map.contains(&pair));
+    }
+}