1 files changed, 51 insertions, 0 deletions
diff --git a/src/config/mod.rs b/src/config/mod.rs
index 811ad57..21a8733 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -236,6 +236,13 @@ pub(crate) const OPTIONS: &[OptionSpec] = &[
         "Chunk size when serving large transfers to other nodes (e.g. an epoch's snapshot to a rejoining node), 1KiB to 4MiB.",
     ),
     option(
+        "transports",
+        Kind::List,
+        "NAME,[NAME...]",
+        Some("mycelium"),
+        "The transports this node uses, in order of preference: mycelium, libp2p (in builds with the libp2p feature). A peer is reached on the first one both have; nodes on several carry the traffic between nodes that share none.",
+    ),
+    option(
         "mycelium-rest-url",
         Kind::Text,
         "SCHEME://HOSTNAME:PORT",
@@ -342,6 +349,8 @@ pub(crate) struct Settings {
     /// In bytes.
     #[serde(default = "default_blob_chunk", with = "crate::units::size_option")]
     pub(crate) blob_chunk: u64,
+    #[serde(default = "default_transports")]
+    pub(crate) transports: Vec<String>,
     pub(crate) mycelium_rest_url: Option<String>,
     pub(crate) mycelium_key_file: Option<PathBuf>,
     pub(crate) mycelium_network_key_file: Option<PathBuf>,
@@ -373,6 +382,12 @@ fn default_electorate_window() -> Duration {
 fn default_blob_chunk() -> u64 {
     64 * 1024
 }
+fn default_transports() -> Vec<String> {
+    vec!["mycelium".to_owned()]
+}
+/// The transports `transports` may name, and whether this build has each.
+pub(crate) const TRANSPORTS: &[(&str, bool)] =
+    &[("mycelium", true), ("libp2p", cfg!(feature = "libp2p"))];
 fn default_mycelium_peers() -> Vec<String> {
     vec!["tls://127.0.0.1:9651".to_owned()]
 }
@@ -434,6 +449,28 @@ impl Settings {
         if self.genesis && self.recover_from.is_some() {
             bail!("recover-from starts the swarm from a backup; it can't be combined with genesis");
         }
+        if self.transports.is_empty() {
+            bail!("transports: a node needs at least one");
+        }
+        for (index, name) in self.transports.iter().enumerate() {
+            match TRANSPORTS.iter().find(|(known, _)| known == name) {
+                None => bail!(
+                    "transports: unknown transport {name:?} (known: {})",
+                    TRANSPORTS
+                        .iter()
+                        .map(|(known, _)| *known)
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                ),
+                Some((_, false)) => {
+                    bail!("transports: this build has no {name} (built without the {name} feature)")
+                }
+                Some(_) if self.transports[..index].contains(name) => {
+                    bail!("transports: {name} is named twice")
+                }
+                Some(_) => {}
+            }
+        }
         if self.debug_epoch.is_some() && !self.debug_api {
             bail!("debug-epoch needs debug-api");
         }
@@ -1354,6 +1391,20 @@ mod tests {
             )
             .is_err()
         );
+        let transports = |names: JsonValue| {
+            resolve(
+                layer(json!({ "htpasswd": "u", "node-key-file": "node.key", "transports": names })),
+                Vec::new(),
+            )
+        };
+        assert!(transports(json!([])).is_err());
+        assert!(transports(json!(["pigeon"])).is_err());
+        assert!(transports(json!(["mycelium", "mycelium"])).is_err());
+        assert!(transports(json!(["mycelium"])).is_ok());
+        assert_eq!(
+            transports(json!(["libp2p", "mycelium"])).is_ok(),
+            cfg!(feature = "libp2p")
+        );
     }
 
     #[test]