feat(p2p): adds tor.forward_address setting (#4070)

Description
---
Adds `tor.forward_address` to instruct tor to forward traffic to a custom address 

Motivation and Context
---
This setting is useful for docker setups where tor and the base node listener are accessible through DNS addresses.

How Has This Been Tested?
---
Manually: setting `tor.forward_address` and checking that traffic is forwarded through that port.

base_layer/p2p/src/initialization.rs

@@ -94,6 +94,8 @@ pub enum CommsInitializationError {
     FailedToAddSeedPeer(#[from] PeerManagerError),
     #[error("Cannot acquire exclusive file lock, another instance of the application is already running")]
     CannotAcquireFileLock,
+    #[error("Invalid tor forward address: `{0}`")]
+    InvalidTorForwardAddress(std::io::Error),
     #[error("IO Error: `{0}`")]
     IoError(#[from] std::io::Error),
 }
@@ -249,10 +251,10 @@ pub async fn spawn_comms_using_transport(
 
 async fn initialize_hidden_service(
     mut config: TorTransportConfig,
-) -> Result<tor::HiddenServiceController, tor::HiddenServiceBuilderError> {
+) -> Result<tor::HiddenServiceController, CommsInitializationError> {
     let mut builder = tor::HiddenServiceBuilder::new()
         .with_hs_flags(tor::HsFlags::DETACH)
-        .with_port_mapping(config.to_port_mapping())
+        .with_port_mapping(config.to_port_mapping()?)
         .with_socks_authentication(config.to_socks_auth())
         .with_control_server_auth(config.to_control_auth())
         .with_socks_address_override(config.socks_address_override)
@@ -267,7 +269,8 @@ async fn initialize_hidden_service(
         builder = builder.with_tor_identity(identity);
     }
 
-    builder.build().await
+    let hidden_svc_ctl = builder.build().await?;
+    Ok(hidden_svc_ctl)
 }
 
 async fn configure_comms_and_dht(

base_layer/p2p/src/transport.rs

@@ -28,9 +28,10 @@ use tari_comms::{
     tor,
     tor::TorIdentity,
     transports::{predicate::FalsePredicate, SocksConfig},
+    utils::multiaddr::multiaddr_to_socketaddr,
 };
 
-use crate::{SocksAuthentication, TorControlAuthentication};
+use crate::{initialization::CommsInitializationError, SocksAuthentication, TorControlAuthentication};
 
 #[derive(Debug, Clone, Serialize, Deserialize, Default)]
 #[serde(deny_unknown_fields)]
@@ -146,14 +147,29 @@ pub struct TorTransportConfig {
     /// When set to true, outbound TCP connections bypass the tor proxy. Defaults to false for better privacy, setting
     /// to true may improve network performance for TCP nodes.
     pub proxy_bypass_for_outbound_tcp: bool,
+    /// If set, instructs tor to forward traffic the the provided address.
+    pub forward_address: Option<Multiaddr>,
     /// The tor identity to use to create the hidden service. If None, a new one will be generated.
     #[serde(skip)]
     pub identity: Option<TorIdentity>,
 }
 
 impl TorTransportConfig {
-    pub fn to_port_mapping(&self) -> tor::PortMapping {
-        tor::PortMapping::new(self.onion_port.get(), ([127, 0, 0, 1], 0).into())
+    /// Returns a [self::tor::PortMapping] struct that maps the [onion_port] to an address that is listening for
+    /// traffic. If [forward_address] is set, that address is used, otherwise 127.0.0.1:[onion_port] is used.
+    ///
+    /// [onion_port]: TorTransportConfig::onion_port
+    /// [forward_address]: TorTransportConfig::forward_address
+    pub fn to_port_mapping(&self) -> Result<tor::PortMapping, CommsInitializationError> {
+        let forward_addr = self
+            .forward_address
+            .as_ref()
+            .map(|addr| multiaddr_to_socketaddr(addr))
+            .transpose()
+            .map_err(CommsInitializationError::InvalidTorForwardAddress)?
+            .unwrap_or_else(|| ([127, 0, 0, 1], 0).into());
+
+        Ok(tor::PortMapping::new(self.onion_port.get(), forward_addr))
     }
 
     pub fn to_control_auth(&self) -> tor::Authentication {
@@ -175,6 +191,7 @@ impl Default for TorTransportConfig {
             onion_port: NonZeroU16::new(18141).unwrap(),
             proxy_bypass_addresses: vec![],
             proxy_bypass_for_outbound_tcp: false,
+            forward_address: None,
             identity: None,
         }
     }

common/config/presets/base_node.toml

@@ -64,6 +64,8 @@ tor.proxy_bypass_addresses = []
 #tor.proxy_bypass_addresses = ["/dns4/my-foo-base-node/tcp/9998"]
 # When using the tor transport and set to true, outbound TCP connections bypass the tor proxy. Defaults to false for better privacy
 tor.proxy_bypass_for_outbound_tcp = false
+# Custom address to forward tor traffic.
+#tor.forward_address = "/ip4/127.0.0.1/tcp/0"
 
 # Use a SOCKS5 proxy transport. This transport recognises any addresses supported by the proxy.
 #type = "socks5"