Reject Docker host match on conflicting physical identity (#1366)

Back-port v5 fix 333e66a8e to v6, adapted to v6's DockerHostView accessors.
findMatchingDockerHost now skips an agentID/token match when
dockerHostIdentityConflicts detects a different MachineID, Swarm NodeID, or
(absent stronger IDs) hostname, so two physically different Docker nodes
that share a token+agentID are not collapsed into one host record. Adds a
regression test.

internal/monitoring/docker_host_identity.go

@@ -87,6 +87,9 @@ func findMatchingDockerHost(hosts []*unifiedresources.DockerHostView, report age
 
 			existingToken := strings.TrimSpace(host.TokenID())
 			if tokenID == "" || existingToken == tokenID {
+				if dockerHostIdentityConflicts(host, report) {
+					continue
+				}
 				return host, true
 			}
 		}
@@ -147,6 +150,46 @@ func findMatchingDockerHost(hosts []*unifiedresources.DockerHostView, report age
 	return nil, false
 }
 
+// dockerHostIdentityConflicts reports whether an incoming report is clearly from
+// a different physical/swarm node than the existing Docker host record, so a
+// shared token+agentID reused from another node is not collapsed into one host.
+func dockerHostIdentityConflicts(existing *unifiedresources.DockerHostView, report agentsdocker.Report) bool {
+	if existing == nil {
+		return false
+	}
+
+	existingMachineID := strings.TrimSpace(existing.MachineID())
+	reportMachineID := strings.TrimSpace(report.Host.MachineID)
+	if existingMachineID != "" && reportMachineID != "" && existingMachineID != reportMachineID {
+		return true
+	}
+
+	existingSwarmNodeID := ""
+	if sw := existing.Swarm(); sw != nil {
+		existingSwarmNodeID = strings.TrimSpace(sw.NodeID)
+	}
+	reportSwarmNodeID := ""
+	if report.Host.Swarm != nil {
+		reportSwarmNodeID = strings.TrimSpace(report.Host.Swarm.NodeID)
+	}
+	if existingSwarmNodeID != "" && reportSwarmNodeID != "" && existingSwarmNodeID != reportSwarmNodeID {
+		return true
+	}
+
+	// Without stronger stable IDs, a hostname change is ambiguous and should not
+	// be treated as the same reporting host automatically.
+	existingHostname := strings.TrimSpace(existing.Hostname())
+	reportHostname := strings.TrimSpace(report.Host.Hostname)
+	if existingMachineID == "" && reportMachineID == "" &&
+		existingSwarmNodeID == "" && reportSwarmNodeID == "" &&
+		existingHostname != "" && reportHostname != "" &&
+		!unifiedresources.HostnamesEquivalent(existingHostname, reportHostname) {
+		return true
+	}
+
+	return false
+}
+
 func dockerHostStableID(host *unifiedresources.DockerHostView) string {
 	if host == nil {
 		return ""

internal/monitoring/docker_host_identity_test.go

@@ -952,3 +952,28 @@ func TestSanitizeDockerHostSuffix_UnicodeRunes(t *testing.T) {
 		t.Errorf("got %q, want %q", result, expected)
 	}
 }
+
+func TestFindMatchingDockerHost_RejectsConflictingPhysicalIdentity(t *testing.T) {
+	t.Parallel()
+
+	hosts := []models.DockerHost{
+		{
+			ID:        "host1",
+			AgentID:   "agent-1",
+			TokenID:   "token-1",
+			MachineID: "machine-1",
+			Hostname:  "hostname-1",
+		},
+	}
+
+	// Same agentID + token, but the report comes from a physically different
+	// machine — it must NOT be collapsed into the existing host (#1366).
+	report := agentsdocker.Report{
+		Agent: agentsdocker.AgentInfo{ID: "agent-1"},
+		Host:  agentsdocker.HostInfo{MachineID: "machine-2", Hostname: "hostname-2"},
+	}
+
+	if _, ok := findMatchingDockerHost(dockerHostViewsForTest(hosts), report, &config.APITokenRecord{ID: "token-1"}); ok {
+		t.Fatal("expected no match when the report's physical identity conflicts with the existing host")
+	}
+}