Add new NetIf variant to NatResolver for IP resolution via network interface (#10922)

Co-authored-by: garwah <garwah@garwah>
Co-authored-by: Emilia Hane <emiliaha95@gmail.com>
Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

Cargo.lock

@@ -7547,6 +7547,7 @@ dependencies = [
  "serde_with",
  "thiserror",
  "tokio",
+ "tracing",
 ]
 
 [[package]]

crates/net/nat/Cargo.toml

@@ -18,6 +18,7 @@ serde_with = { workspace = true, optional = true }
 thiserror.workspace = true
 tokio = { workspace = true, features = ["time"] }
 if-addrs.workspace = true
+tracing.workspace = true
 
 [dev-dependencies]
 reth-tracing.workspace = true

crates/net/nat/src/lib.rs

@@ -25,7 +25,9 @@ use std::{
     task::{Context, Poll},
     time::Duration,
 };
+use tracing::error;
 
+use crate::net_if::resolve_net_if_ip;
 #[cfg(feature = "serde")]
 use serde_with::{DeserializeFromStr, SerializeDisplay};
 
@@ -48,6 +50,8 @@ pub enum NatResolver {
     PublicIp,
     /// Use the given [`IpAddr`]
     ExternalIp(IpAddr),
+    /// Resolve external IP via the network interface.
+    NetIf,
     /// Resolve nothing
     None,
 }
@@ -66,6 +70,7 @@ impl fmt::Display for NatResolver {
             Self::Upnp => f.write_str("upnp"),
             Self::PublicIp => f.write_str("publicip"),
             Self::ExternalIp(ip) => write!(f, "extip:{ip}"),
+            Self::NetIf => f.write_str("netif"),
             Self::None => f.write_str("none"),
         }
     }
@@ -91,6 +96,7 @@ impl FromStr for NatResolver {
             "upnp" => Self::Upnp,
             "none" => Self::None,
             "publicip" | "public-ip" => Self::PublicIp,
+            "netif" => Self::NetIf,
             s => {
                 let Some(ip) = s.strip_prefix("extip:") else {
                     return Err(ParseNatResolverError::UnknownVariant(format!(
@@ -185,6 +191,13 @@ pub async fn external_addr_with(resolver: NatResolver) -> Option<IpAddr> {
     match resolver {
         NatResolver::Any | NatResolver::Upnp | NatResolver::PublicIp => resolve_external_ip().await,
         NatResolver::ExternalIp(ip) => Some(ip),
+        NatResolver::NetIf => match resolve_net_if_ip(DEFAULT_NET_IF_NAME) {
+            Ok(ip) => Some(ip),
+            Err(err) => {
+                error!("Failed to resolve network interface IP: {}", err);
+                None
+            }
+        },
         NatResolver::None => None,
     }
 }