refactor: simplify control flow and error handling in metrics and netlink

src/metrics.rs

@@ -78,8 +78,10 @@ impl Transport {
 
                 let full_data = format!("{}\n", data);
                 // take the stream out, write, put it back or set None on failure
-                if let Some(s) = stream {
+                let write_error = stream
-                    if let Err(e) = std::io::Write::write_all(s, full_data.as_bytes()) {
+                    .as_mut()
+                    .and_then(|s| std::io::Write::write_all(s, full_data.as_bytes()).err());
+                if let Some(e) = write_error {
                     warn!("TCP send failed: {}", e);
                     *stream = None;
                     *reconnect_backoff = (*reconnect_backoff * 2).min(MAX_RECONNECT_BACKOFF);
@@ -88,7 +90,6 @@ impl Transport {
         }
     }
 }
-}
 
 pub enum Metric {
     Ping {
@@ -209,11 +210,8 @@ impl Metrics {
             }
 
             // greedily drain without blocking
-            loop {
+            while let Ok(metric) = self.metrics_rx.try_recv() {
-                match self.metrics_rx.try_recv() {
+                batch.push(metric);
-                    Ok(metric) => batch.push(metric),
-                    Err(_) => break,
-                }
                 if batch.len() >= batch_size {
                     break;
                 }

src/netlink.rs

@@ -85,9 +85,9 @@ impl Netlink {
         while let Some(reply) = iter.recv() {
             let (header, attrs) = reply?;
 
-            if header.ifindex == ifindex {
+            if header.ifindex == ifindex
-                if let Ok(kind) = attrs.get_kind() {
+                && let Ok(kind) = attrs.get_kind()
-                    if kind
+                && kind
                     .to_str()
                     .map_err(|_| NetlinkError::NlQdiscError("Invalid UTF-8".to_string()))?
                     == "cake"
@@ -98,8 +98,6 @@ impl Netlink {
                 });
             }
         }
-            }
-        }
 
         Err(NetlinkError::NoQdiscFound(ifname.to_string()))
     }

src/ratecontroller.rs

@@ -446,8 +446,8 @@ impl Ratecontroller {
                     delta_delay_up: self.state_ul.delta_stat,
                 });
 
-                if let Some(ref mut fd) = stats_fd {
+                let stats_write_error = stats_fd.as_mut().and_then(|fd| {
-                    if let Err(e) = fd.write_all(
+                    fd.write_all(
                         format!(
                             "{},{},{},{},{},{},{},{}\n",
                             stats_time.secs(),
@@ -460,16 +460,19 @@ impl Ratecontroller {
                             self.state_ul.current_rate as u64
                         )
                         .as_bytes(),
-                    ) {
+                    )
+                    .err()
+                });
+                if let Some(e) = stats_write_error {
                     warn!("Failed to write statistics: {}", e);
                 }
-                }
 
                 lastchg_t = now_t;
             }
 
-            if let Some(ref mut fd) = speed_hist_fd {
+            if let Some(ref mut fd) = speed_hist_fd
-                if now_t.duration_since(lastdump_t).as_secs_f64() > 300.0 {
+                && now_t.duration_since(lastdump_t).as_secs_f64() > 300.0
+            {
                 for i in 0..self.config.speed_hist_size as usize {
                     let hist_time = Time::new(ClockId::Realtime);
                     if let Err(e) = fd.write_all(
@@ -491,4 +494,3 @@ impl Ratecontroller {
         }
     }
 }
-}