feat(monitoring): add dry-run mode to simulate qdisc rate changes

Enable a monitoring-only mode that logs intended bandwidth adjustments without applying them to the system via netlink.

src/config.rs

@@ -84,6 +84,9 @@ pub struct Config {
     pub speed_hist_size: u32,
     pub tick_interval: f64,
     pub upload_delay_ms: f64,
+
+    // Monitoring / dry-run
+    pub dry_run: bool,
 }
 
 impl Config {
@@ -186,6 +189,11 @@ impl Config {
                 "sqm-autorate.@advanced_settings[0].upload_delay_ms",
                 Some(15.0),
             )?,
+            dry_run: Self::get::<bool>(
+                "SQMA_DRY_RUN",
+                "sqm-autorate.@advanced_settings[0].dry_run",
+                Some(false),
+            )?,
         };
 
         let mut config = config;

src/main.rs

@@ -39,6 +39,9 @@ fn main() -> anyhow::Result<()> {
 
     let config = Config::new()?;
     log::init(config.log_level)?;
+    if config.dry_run {
+        info!("*** MONITORING MODE ACTIVE — qdisc rates will NOT be changed ***");
+    }
     let mut reflectors = config.load_reflectors()?;
     let start_t = Instant::now();
 
@@ -111,8 +114,8 @@ fn main() -> anyhow::Result<()> {
         "Setting shaper rates to minimum (D/L): {} / {}",
         config.download_min_kbits, config.upload_min_kbits
     );
-    Netlink::set_qdisc_rate(down_qdisc, config.download_min_kbits as u64)?;
+    Netlink::set_qdisc_rate(down_qdisc, config.download_min_kbits as u64, config.dry_run)?;
-    Netlink::set_qdisc_rate(up_qdisc, config.upload_min_kbits as u64)?;
+    Netlink::set_qdisc_rate(up_qdisc, config.upload_min_kbits as u64, config.dry_run)?;
 
     // Sleep for a few seconds to give the shaper a chance
     // to control the queue if load is heavy

src/netlink.rs

@@ -1,6 +1,7 @@
 use std::io;
 use std::str::Utf8Error;
 
+use log::info;
 use netlink_bindings::{rt_link, tc};
 use netlink_socket2::NetlinkSocket;
 use thiserror::Error;
@@ -111,7 +112,15 @@ impl Netlink {
         Netlink::qdisc_from_ifindex(ifindex, ifname)
     }
 
-    pub fn set_qdisc_rate(qdisc: Qdisc, bandwidth_kbit: u64) -> Result<(), NetlinkError> {
+    pub fn set_qdisc_rate(qdisc: Qdisc, bandwidth_kbit: u64, dry_run: bool) -> Result<(), NetlinkError> {
+        if dry_run {
+            info!(
+                "dry-run: would set qdisc ifindex={} to {} kbit/s",
+                qdisc.ifindex, bandwidth_kbit
+            );
+            return Ok(());
+        }
+
         let mut socket = NetlinkSocket::new();
         let bandwidth = bandwidth_kbit * 1000 / 8;
 

src/ratecontroller.rs

@@ -282,10 +282,12 @@ impl Ratecontroller {
         Netlink::set_qdisc_rate(
             self.state_dl.qdisc,
             self.state_dl.current_rate.round() as u64,
+            self.config.dry_run,
         )?;
         Netlink::set_qdisc_rate(
             self.state_ul.qdisc,
             self.state_ul.current_rate.round() as u64,
+            self.config.dry_run,
         )?;
 
         let mut speed_hist_fd: Option<File> = None;
@@ -346,10 +348,12 @@ impl Ratecontroller {
                     Netlink::set_qdisc_rate(
                         self.state_dl.qdisc,
                         self.state_dl.next_rate as u64,
+                        self.config.dry_run,
                     )?;
                     Netlink::set_qdisc_rate(
                         self.state_ul.qdisc,
                         self.state_ul.next_rate as u64,
+                        self.config.dry_run,
                     )?;
 
                     self.state_dl.current_rate = self.state_dl.next_rate;
@@ -370,11 +374,11 @@ impl Ratecontroller {
                 }
 
                 if self.state_dl.next_rate != self.state_dl.current_rate {
-                    Netlink::set_qdisc_rate(self.state_dl.qdisc, self.state_dl.next_rate as u64)?;
+                    Netlink::set_qdisc_rate(self.state_dl.qdisc, self.state_dl.next_rate as u64, self.config.dry_run)?;
                 }
 
                 if self.state_ul.next_rate != self.state_ul.current_rate {
-                    Netlink::set_qdisc_rate(self.state_ul.qdisc, self.state_ul.next_rate as u64)?;
+                    Netlink::set_qdisc_rate(self.state_ul.qdisc, self.state_ul.next_rate as u64, self.config.dry_run)?;
                 }
 
                 self.state_dl.current_rate = self.state_dl.next_rate;