From 79c609e4f1019399c3158f3562e02caa68c89f6d Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 8 Aug 2022 09:23:55 -0400
Subject: [PATCH] arti: Add a feature flag for dns-proxy.

It remains on-by-default, so users shouldn't notice a difference,
but it may help when we want to save a few bytes of binary size.

Closes #532
---
 crates/arti/Cargo.toml |  7 ++++---
 crates/arti/src/lib.rs | 10 ++++++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/crates/arti/Cargo.toml b/crates/arti/Cargo.toml
index 8b309c3a2..a71309a7f 100644
--- a/crates/arti/Cargo.toml
+++ b/crates/arti/Cargo.toml
@@ -12,11 +12,12 @@ categories = ["command-line-utilities", "cryptography"]
 repository = "https://gitlab.torproject.org/tpo/core/arti.git/"
 
 [features]
-default = ["tokio", "native-tls"]
+default = ["tokio", "native-tls", "dns-proxy"]
 
-full = ["async-std", "tokio", "native-tls", "journald", "arti-client/full"]
+full = ["async-std", "tokio", "native-tls", "journald", "arti-client/full", "dns-proxy"]
 
 async-std = ["arti-client/async-std", "tor-rtcompat/async-std", "async-ctrlc", "once_cell"]
+dns-proxy = ["trust-dns-proto"]
 tokio = ["tokio-crate", "arti-client/tokio", "tor-rtcompat/tokio"]
 native-tls = ["arti-client/native-tls", "tor-rtcompat/native-tls"]
 rustls = ["arti-client/rustls", "tor-rtcompat/rustls"]
@@ -57,7 +58,7 @@ tracing = "0.1.18"
 tracing-appender = "0.2.0"
 tracing-journald = { version = "0.3.0", optional = true }
 tracing-subscriber = { version = "0.3.0", features = ["env-filter"] }
-trust-dns-proto = "0.21.1"
+trust-dns-proto = { version = "0.21.1", optional = true }
 
 [dev-dependencies]
 itertools = "0.10.1"
diff --git a/crates/arti/src/lib.rs b/crates/arti/src/lib.rs
index d5269f292..68925c0ae 100644
--- a/crates/arti/src/lib.rs
+++ b/crates/arti/src/lib.rs
@@ -52,6 +52,8 @@
 //!   (default)
 //! * `journald` -- Build with support for logging to the `journald` logging
 //!   backend (available as part of systemd.)
+//! * `dns-proxy` (default) -- Build with support for proxying certain simple
+//!   DNS queries over the Tor network.  
 //!
 //! * `full` -- Build with all features above, along with all stable additive
 //!   features from other arti crates.  (This does not include experimental
@@ -150,6 +152,7 @@
 #![allow(clippy::print_stdout)]
 
 pub mod cfg;
+#[cfg(feature = "dns-proxy")]
 pub mod dns;
 pub mod exit;
 pub mod logging;
@@ -246,6 +249,7 @@ pub async fn run<R: Runtime>(
         }));
     }
 
+    #[cfg(feature = "dns-proxy")]
     if dns_port != 0 {
         let runtime = runtime.clone();
         let client = client.isolated_client();
@@ -255,6 +259,12 @@ pub async fn run<R: Runtime>(
         }));
     }
 
+    #[cfg(not(feature = "dns-proxy"))]
+    if dns_port != 0 {
+        warn!("Tried to specify a DNS proxy port, but Arti was built without dns-proxy support.");
+        return Ok(());
+    }
+
     if proxy.is_empty() {
         warn!("No proxy port set; specify -p PORT (for `socks_port`) or -d PORT (for `dns_port`). Alternatively, use the `socks_port` or `dns_port` configuration option.");
         return Ok(());