feat: support non-standard ssh clients and passthrough options

src/cli/args.rs

@@ -41,7 +41,7 @@ pub(crate) struct CliArgs {
     /// intended for interactive use.
     #[arg(
         long, help_heading("Modes"), hide = true,
-        conflicts_with_all(["help_buffers", "quiet", "statistics", "timeout", "ipv4", "ipv6", "remote_debug", "profile"])
+        conflicts_with_all(["help_buffers", "quiet", "statistics", "timeout", "ipv4", "ipv6", "remote_debug", "profile", "source", "destination", "ssh", "ssh_opt"])
     )]
     pub server: bool,
 
@@ -71,6 +71,21 @@ pub(crate) struct CliArgs {
     #[arg(short = '6', long, action, conflicts_with("ipv4"))]
     pub ipv6: bool,
 
+    /// Specifies the ssh client program to use
+    #[arg(long, default_value("ssh"))]
+    pub ssh: String,
+
+    /// Specifies an additional option or argument to pass to the ssh client.
+    /// Note: you must repeat `-S` for each.
+    /// For example, to pass `-i /dev/null` to ssh, specify `-S -i -S /dev/null`
+    #[arg(
+        short = 'S',
+        action,
+        value_name("ssh-option"),
+        allow_hyphen_values(true)
+    )]
+    pub ssh_opt: Vec<String>,
+
     // CLIENT DEBUG ----------------------------
     /// Enable detailed debug output
     #[arg(short, long, action, help_heading("Debug options"), display_order(100))]

src/client/control.rs

@@ -26,6 +26,8 @@ pub struct Parameters {
     bbr: bool,
     iwind: Option<u64>,
     family: AddressFamily,
+    ssh_client: String,
+    ssh_opts: Vec<String>,
 }
 
 impl TryFrom<&CliArgs> for Parameters {
@@ -43,6 +45,8 @@ impl TryFrom<&CliArgs> for Parameters {
             bbr: args.bbr,
             iwind: args.initial_congestion_window,
             family: args.address_family(),
+            ssh_client: args.ssh.clone(),
+            ssh_opts: args.ssh_opt.clone(),
         })
     }
 }
@@ -93,13 +97,14 @@ impl ControlChannel {
 
     /// This is effectively a constructor. At present, it launches a subprocess.
     fn launch(args: &Parameters) -> Result<Self> {
-        let mut server = tokio::process::Command::new("ssh");
+        let mut server = tokio::process::Command::new(&args.ssh_client);
         let _ = server.kill_on_drop(true);
         let _ = match args.family {
             AddressFamily::Any => &mut server,
             AddressFamily::IPv4 => server.arg("-4"),
             AddressFamily::IPv6 => server.arg("-6"),
         };
+        let _ = server.args(&args.ssh_opts);
         let _ = server.args([
             &args.remote_user_host,
             "qcp",