From c66430c67049ad46ba66d5412051327f760d1350 Mon Sep 17 00:00:00 2001
From: Kristoffer Dalby <kristoffer@tailscale.com>
Date: Sat, 1 Nov 2025 22:43:43 +0100
Subject: [PATCH] types: add order-independent endpoint comparison

Add EndpointsChanged function that compares endpoint slices
without regard to ordering. Uses netip.AddrPort.Compare with
slices.SortFunc to enable accurate change detection.

Update PeerChangeFromMapRequest to only include endpoints in
PeerChange when they actually changed, avoiding unnecessary
updates to peers.
---
 hscontrol/types/node.go | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/hscontrol/types/node.go b/hscontrol/types/node.go
index 8cf40ced..0481f621 100644
--- a/hscontrol/types/node.go
+++ b/hscontrol/types/node.go
@@ -509,8 +509,10 @@ func (node *Node) PeerChangeFromMapRequest(req tailcfg.MapRequest) tailcfg.PeerC
 		}
 	}
 
-	// TODO(kradalby): Find a good way to compare updates
-	ret.Endpoints = req.Endpoints
+	// Compare endpoints using order-independent comparison
+	if EndpointsChanged(node.Endpoints, req.Endpoints) {
+		ret.Endpoints = req.Endpoints
+	}
 
 	now := time.Now()
 	ret.LastSeen = &now
@@ -518,6 +520,32 @@ func (node *Node) PeerChangeFromMapRequest(req tailcfg.MapRequest) tailcfg.PeerC
 	return ret
 }
 
+// EndpointsChanged compares two endpoint slices and returns true if they differ.
+// The comparison is order-independent - endpoints are sorted before comparison.
+func EndpointsChanged(oldEndpoints, newEndpoints []netip.AddrPort) bool {
+	if len(oldEndpoints) != len(newEndpoints) {
+		return true
+	}
+
+	if len(oldEndpoints) == 0 {
+		return false
+	}
+
+	// Make copies to avoid modifying the original slices
+	oldCopy := slices.Clone(oldEndpoints)
+	newCopy := slices.Clone(newEndpoints)
+
+	// Sort both slices to enable order-independent comparison
+	slices.SortFunc(oldCopy, func(a, b netip.AddrPort) int {
+		return a.Compare(b)
+	})
+	slices.SortFunc(newCopy, func(a, b netip.AddrPort) int {
+		return a.Compare(b)
+	})
+
+	return !slices.Equal(oldCopy, newCopy)
+}
+
 func (node *Node) RegisterMethodToV1Enum() v1.RegisterMethod {
 	switch node.RegisterMethod {
 	case "authkey":