More readme info

README.md

@@ -3,9 +3,17 @@
 [![Docs.rs](https://docs.rs/protomask/badge.svg)](https://docs.rs/protomask) 
 [![Build](https://github.com/Ewpratten/protomask/actions/workflows/build.yml/badge.svg)](https://github.com/Ewpratten/protomask/actions/workflows/build.yml)
 
-**A user space NAT64 implementation.**
+**A user space [NAT64](https://en.wikipedia.org/wiki/NAT64) implementation.**
 
-*Protomask* started as a challenge to create a NAT64 implementation in a weekend. The goal of this implementation is to *keep things simple*. There aren't many knobs to tweak, so if you want to do stateful NAT or source address filtering, put something like `iptables` in front of it.
+Protomask started as a challenge to create a NAT64 implementation in a weekend. The goal of this implementation is to *keep things simple*. There aren't many knobs to tweak, so if you want to do stateful NAT or source address filtering, put something like `iptables` in front of it.
+
+## How it works
+
+Protomask listens on an IPv6 `/96` prefix for incoming traffic.
+
+When traffic destined for an [embedded IPv4 address](https://datatracker.ietf.org/doc/html/rfc6052) is received, the source IPv6 address is assigned a real IPv4 address from a pool of addresses on a first-come-first-serve basis.
+
+All further packet from that source IPv6 address will be NAT-ed through its assigned IPv4 address until the reservation expires. The reverse process happens for return traffic too.
 
 ## Configuration
 
@@ -13,14 +21,15 @@ Protomask uses a [TOML](https://toml.io) configuration file. Here is a functiona
 
 ```toml
 [Interface]
-# A list of IPv4 prefixes to map traffic to
-Pool = ["44.31.119.0/24"]
-# The IPv6 prefix to listen for traffic on (should generally be the well-known 64:ff9b::/96 prefix)
+# The IPv6 prefix to listen for V6 traffic on
 Prefix = "64:ff9b::/96"
+# A list of IPv4 prefixes to map V6 traffic to
+Pool = ["192.0.2.0/24"]
 
 [Rules]
 # A static mapping of IPv4 and IPv6 addresses
-# These addresses will be exclusively reserved, and not used in the general pool
+# These addresses will not used in the dynamic pool
 MapStatic = [{ v4 = "192.0.2.2", v6 = "2001:db8:1::2" }]
+# How many seconds to keep a dynamic mapping alive for
+ReservationDuration = 7200 # Optional
 ```
-

src/config.rs

@@ -10,12 +10,6 @@ use ipnet::{Ipv4Net, Ipv6Net};
 /// Interface config
 #[derive(Debug, serde::Deserialize)]
 pub struct InterfaceConfig {
-    /// IPv4 router address
-    // #[serde(rename = "Address4")]
-    // pub address_v4: Ipv4Addr,
-    // /// IPv6 router address
-    // #[serde(rename = "Address6")]
-    // pub address_v6: Ipv6Addr,
     /// Ipv4 pool
     #[serde(rename = "Pool")]
     pub pool: Vec<Ipv4Net>,
@@ -34,8 +28,8 @@ pub struct AddressMappingRule {
 }
 
 /// Used to generate the default reservation duration
-fn default_reservation_duration() -> Duration {
-    Duration::from_secs(7200)
+fn default_reservation_duration() -> u64 {
+    7200
 }
 
 /// Rules config
@@ -46,7 +40,14 @@ pub struct RulesConfig {
     pub static_map: Vec<AddressMappingRule>,
     /// How long to hold a dynamic mapping for
     #[serde(rename = "ReservationDuration", default="default_reservation_duration")]
-    pub reservation_duration: Duration,
+    reservation_duration: u64,
+}
+
+impl RulesConfig {
+    /// Get the reservation duration
+    pub fn reservation_duration(&self) -> Duration {
+        Duration::from_secs(self.reservation_duration)
+    }
 }
 
 /// Representation of the `protomask.toml` config file

src/main.rs

@@ -60,7 +60,7 @@ pub async fn main() {
             .iter()
             .map(|rule| (rule.v6, rule.v4))
             .collect(),
-        config.rules.reservation_duration,
+        config.rules.reservation_duration(),
     )
     .await
     .unwrap();