servertest: compare user profiles in via captures

Self and peer profiles, by login and display name. A tagged self gets
its own profile in SaaS; listed as a skip entry until headscale matches.

hscontrol/servertest/via_compat_test.go

@@ -67,6 +67,13 @@ var viaCompatTests = []struct {
 	{"via-grant-v62", "via exit steering plus a member rule to autogroup:internet on one port"},
 }
 
+// viaCompatSkipReasons lists checks where headscale differs from SaaS,
+// keyed by check alone where every capture differs the same way. A listed
+// check that matches fails, so a fix must delete its entry.
+var viaCompatSkipReasons = map[string]string{
+	"tagged-self": "TAGGED_SELF_PROFILE: SaaS gives a tagged node a profile of its own, headscale the shared tagged-devices one",
+}
+
 // TestViaGrantMapCompat loads golden captures from Tailscale SaaS and
 // compares headscale's [tailcfg.MapResponse] structure against the captured [netmap.NetworkMap].
 //
@@ -479,6 +486,75 @@ func compareNetmap(
 	}
 
 	comparePacketFilter(t, got, want, clients, saasAddrs)
+	compareUserProfiles(t, got, want.Netmap, clients)
+}
+
+// compareUserProfiles compares the profile the viewer holds for itself and
+// for each peer in clients. Profile IDs differ between SaaS and headscale, so
+// a profile is its login, with SaaS emails mapped to user names, and its
+// display name.
+func compareUserProfiles(
+	t require.TestingT,
+	got, want *netmap.NetworkMap,
+	clients map[string]*servertest.TestClient,
+) {
+	if h, ok := t.(interface{ Helper() }); ok {
+		h.Helper()
+	}
+
+	gotProfiles := nodeProfiles(got, clients)
+
+	for name, wantProfile := range nodeProfiles(want, clients) {
+		check := "peer"
+		if name == "" {
+			check = "self"
+			if want.SelfNode.Tags().Len() > 0 {
+				check = "tagged-self"
+			}
+		}
+
+		if reason, listed := viaCompatSkipReasons[check]; listed {
+			if gotProfiles[name] == wantProfile {
+				t.Errorf("node %q: %s profile matches SaaS; delete viaCompatSkipReasons[%q] (%s)",
+					name, check, check, reason)
+			}
+
+			continue
+		}
+
+		assert.Equalf(t, wantProfile, gotProfiles[name], "node %q: %s profile mismatch", name, check)
+	}
+}
+
+// nodeProfiles maps "" (self) and each peer in clients to its user profile.
+func nodeProfiles(
+	nm *netmap.NetworkMap,
+	clients map[string]*servertest.TestClient,
+) map[string]string {
+	profile := func(id tailcfg.UserID) string {
+		p, ok := nm.UserProfiles[id]
+		if !ok {
+			return "no profile"
+		}
+
+		login := p.LoginName()
+		if name, ok := captureUserNames[login]; ok {
+			login = name
+		}
+
+		return login + " / " + p.DisplayName()
+	}
+
+	out := map[string]string{"": profile(nm.SelfNode.User())}
+
+	for _, peer := range nm.Peers {
+		name := extractHostname(peer.Name())
+		if _, isOurs := clients[name]; isOurs {
+			out[name] = profile(peer.User())
+		}
+	}
+
+	return out
 }
 
 // comparePacketFilter compares PacketFilter rules as a set of (source,

hscontrol/servertest/via_ha_compat_test.go

@@ -337,6 +337,8 @@ func compareCaptureNetmap(
 			len(want.PacketFilterRules), gotLen,
 		)
 	}
+
+	compareUserProfiles(t, nm, want.Netmap, clients)
 }
 
 type capturePeerSummary struct {