feat(client): make reconnect exponential backoff configurable

crates/irtt-app/src/cmd/client/args.rs

@@ -72,7 +72,7 @@ pub struct ClientArgs {
     #[arg(
         long,
         conflicts_with = "no_test",
-        long_help = "Retry failed initial opens and closed, failed, or silent sessions independently per target. Requires --continuous or --duration 0. Unsuccessful connections back off from 250ms to 10s. Use --reconnect-timeout to configure silence detection and --no-stats when only measurement events are needed."
+        long_help = "Retry failed initial opens and closed, failed, or silent sessions independently per target. Requires --continuous or --duration 0. Unsuccessful connections use exponential backoff (defaults: 250ms initial, 10s maximum), configurable with --reconnect-initial-delay and --reconnect-max-delay. Use --reconnect-timeout to configure silence detection and --no-stats when only measurement events are needed."
     )]
     pub reconnect: bool,
 
@@ -80,6 +80,14 @@ pub struct ClientArgs {
     #[arg(long, default_value = "10s", value_parser = crate::shared::client::parse_duration, requires = "reconnect")]
     pub reconnect_timeout: Duration,
 
+    /// Initial retry delay, restored after a valid reply.
+    #[arg(long, default_value = "250ms", value_parser = crate::shared::client::parse_duration, requires = "reconnect")]
+    pub reconnect_initial_delay: Duration,
+
+    /// Maximum retry delay (must be at least twice the initial delay).
+    #[arg(long, default_value = "10s", value_parser = crate::shared::client::parse_duration, requires = "reconnect")]
+    pub reconnect_max_delay: Duration,
+
     #[command(flatten)]
     pub common: CommonClientArgs,
 
@@ -132,6 +140,15 @@ impl ClientArgs {
         if self.reconnect && !self.is_continuous() {
             return Err("--reconnect requires --continuous or --duration 0".to_owned());
         }
+        if self
+            .reconnect_initial_delay
+            .checked_mul(2)
+            .is_none_or(|minimum| self.reconnect_max_delay < minimum)
+        {
+            return Err(
+                "--reconnect-max-delay must be at least twice --reconnect-initial-delay".to_owned(),
+            );
+        }
         if self.targets_stdin && !self.is_continuous() {
             return Err("--targets-stdin requires --continuous or --duration 0".to_owned());
         }

crates/irtt-app/src/cmd/client/run.rs

@@ -78,6 +78,8 @@ pub async fn run_stream(
         {
             let mut config = setup.managed_config();
             config.reconnect_timeout = args.reconnect.then_some(args.reconnect_timeout);
+            config.reconnect_initial_delay = args.reconnect_initial_delay;
+            config.reconnect_max_delay = args.reconnect_max_delay;
             config
         },
         setup.managed_targets(),
@@ -482,6 +484,8 @@ async fn run_stdin_stream(
         {
             let mut config = setup.managed_config();
             config.reconnect_timeout = args.reconnect.then_some(args.reconnect_timeout);
+            config.reconnect_initial_delay = args.reconnect_initial_delay;
+            config.reconnect_max_delay = args.reconnect_max_delay;
             config
         },
         setup.managed_targets(),