customizes override logic for gossip ContactInfo

If there are two running instances of the same node, we want the one
with more recent start time to be propagated through gossip regardless
of wallclocks.

The commit adds custom override logic for ContactInfo to first compare
by outset timestamp.

gossip/src/contact_info.rs

@@ -14,6 +14,7 @@ use {
     solana_streamer::socket::SocketAddrSpace,
     static_assertions::const_assert_eq,
     std::{
+        cmp::Ordering,
         collections::HashSet,
         net::{IpAddr, Ipv4Addr, SocketAddr},
         time::{SystemTime, UNIX_EPOCH},
@@ -443,6 +444,24 @@ impl ContactInfo {
     pub(crate) fn check_duplicate(&self, other: &ContactInfo) -> bool {
         self.pubkey == other.pubkey && self.outset < other.outset
     }
+
+    // Returns None if the contact-infos have different pubkey.
+    // Otherwise returns true if (self.outset, self.wallclock) tuple is larger
+    // than (other.outset, other.wallclock).
+    // If the tuples are equal it returns None.
+    #[inline]
+    #[must_use]
+    pub(crate) fn overrides(&self, other: &ContactInfo) -> Option<bool> {
+        if self.pubkey != other.pubkey {
+            return None;
+        }
+        let other = (other.outset, other.wallclock);
+        match (self.outset, self.wallclock).cmp(&other) {
+            Ordering::Less => Some(false),
+            Ordering::Greater => Some(true),
+            Ordering::Equal => None,
+        }
+    }
 }
 
 impl Default for ContactInfo {
@@ -1038,6 +1057,8 @@ mod tests {
             let other = node.clone();
             assert!(!node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), None);
+            assert_eq!(other.overrides(&node), None);
         }
         // Updated socket address is not a duplicate instance.
         {
@@ -1046,16 +1067,28 @@ mod tests {
             while other.set_serve_repair(new_rand_socket(&mut rng)).is_err() {}
             assert!(!node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), None);
+            assert_eq!(other.overrides(&node), None);
             other.remove_serve_repair();
             assert!(!node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), None);
+            assert_eq!(other.overrides(&node), None);
         }
         // Updated wallclock is not a duplicate instance.
         {
             let other = node.clone();
             node.set_wallclock(rng.gen());
             assert!(!node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(
+                node.overrides(&other),
+                Some(other.wallclock < node.wallclock)
+            );
+            assert_eq!(
+                other.overrides(&node),
+                Some(node.wallclock < other.wallclock)
+            );
         }
         // Different pubkey is not a duplicate instance.
         {
@@ -1066,6 +1099,8 @@ mod tests {
             );
             assert!(!node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), None);
+            assert_eq!(other.overrides(&node), None);
         }
         // Same pubkey, more recent outset timestamp is a duplicate instance.
         {
@@ -1077,6 +1112,14 @@ mod tests {
             assert!(node.outset < other.outset);
             assert!(node.check_duplicate(&other));
             assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), Some(false));
+            assert_eq!(other.overrides(&node), Some(true));
+            node.set_wallclock(other.wallclock);
+            assert!(node.outset < other.outset);
+            assert!(node.check_duplicate(&other));
+            assert!(!other.check_duplicate(&node));
+            assert_eq!(node.overrides(&other), Some(false));
+            assert_eq!(other.overrides(&node), Some(true));
         }
     }
 }

gossip/src/crds.rs

@@ -196,14 +196,21 @@ impl Default for Crds {
 // Both values should have the same key/label.
 fn overrides(value: &CrdsValue, other: &VersionedCrdsValue) -> bool {
     assert_eq!(value.label(), other.value.label(), "labels mismatch!");
-    // Node instances are special cased so that if there are two running
-    // instances of the same node, the more recent start is propagated through
-    // gossip regardless of wallclocks.
+    // Contact-infos and node instances are special cased so that if there are
+    // two running instances of the same node, the more recent start is
+    // propagated through gossip regardless of wallclocks.
     if let CrdsData::NodeInstance(value) = &value.data {
         if let Some(out) = value.overrides(&other.value) {
             return out;
         }
     }
+    if let CrdsData::ContactInfo(value) = &value.data {
+        if let CrdsData::ContactInfo(other) = &other.value.data {
+            if let Some(out) = value.overrides(other) {
+                return out;
+            }
+        }
+    }
     match value.wallclock().cmp(&other.value.wallclock()) {
         Ordering::Less => false,
         Ordering::Greater => true,