fix: Only free up sending a call me maybe when the best addr was invalidated

Author: matheus23

iroh/src/magicsock/node_map/node_state.rs

@@ -1037,10 +1037,12 @@ impl NodeState {
                 }
             }
         }
-        // Clear trust on our best_addr if it is not included in the updated set.  Also
-        // clear the last call-me-maybe send time so we will send one again.
-        self.udp_paths.update_to_best_addr(now);
-        self.last_call_me_maybe = None;
+        // Clear trust on our best_addr if it is not included in the updated set.
+        let changed = self.udp_paths.update_to_best_addr(now);
+        if changed {
+            // Clear the last call-me-maybe send time so we will send one again.
+            self.last_call_me_maybe = None;
+        }
         debug!(
             paths = %summarize_node_paths(&self.udp_paths.paths),
             "updated endpoint paths from call-me-maybe",

iroh/src/magicsock/node_map/udp_paths.rs

@@ -8,6 +8,7 @@
 use std::{collections::BTreeMap, net::SocketAddr};
 
 use n0_future::time::Instant;
+use tracing::{event, Level};
 
 use super::{path_state::PathState, IpPort};
 
@@ -113,9 +114,34 @@ impl NodeUdpPaths {
         &self.best
     }
 
-    pub(super) fn update_to_best_addr(&mut self, now: Instant) {
-        self.best_ipv4 = self.best_addr(false, now);
-        self.best = self.best_addr(true, now);
+    /// Changes the current best address(es) to ones chosen as described in [`Self::best_addr`] docs.
+    ///
+    /// Returns whether one of the best addresses had to change.
+    ///
+    /// This should be called any time that `paths` is modified.
+    pub(super) fn update_to_best_addr(&mut self, now: Instant) -> bool {
+        let best_ipv4 = self.best_addr(false, now);
+        let best = self.best_addr(true, now);
+        let mut changed = false;
+        if best_ipv4 != self.best_ipv4 {
+            event!(
+                target: "iroh::_events::udp::best_ipv4",
+                Level::DEBUG,
+                ?best_ipv4,
+            );
+            changed = true;
+        }
+        if best != self.best {
+            event!(
+                target: "iroh::_events::udp::best",
+                Level::DEBUG,
+                ?best,
+            );
+            changed = true;
+        }
+        self.best_ipv4 = best_ipv4;
+        self.best = best;
+        changed
     }
 
     pub(super) fn best_addr(&self, have_ipv6: bool, now: Instant) -> UdpSendAddr {