WIP

peer/device.go

@@ -53,7 +53,7 @@ func (a *App) devAddDirect(p *Peer, endpoint netip.AddrPort) {
 func (a *App) devSetRelay(p *Peer, endpoint netip.AddrPort) {
 	log.Printf("RELAY: %s - %s @ %s", p.Name, p.VPNIP.String(), endpoint.String())
 	devRetry(p.VPNIP, "SetRelay", func() error { return a.dev.SetRelay(p.PubKey(), endpoint, a.vpnNet) })
-	p.State = StateDirect
+	p.State = StateDirect // Dirrect connection. The app marks peer as relay.
 }
 
 func (a *App) devPromote(p *Peer) {

peer/hosts.go

@@ -14,10 +14,18 @@ import (
 
 const (
 	hostsFile  = "/etc/hosts"
-	hostsBegin = "# BEGIN vppn "
-	hostsEnd   = "# END vppn "
+	hostsBegin = "# BEGIN vppn"
+	hostsEnd   = "# END vppn"
 )
 
+// hostMarkers returns the begin/end marker lines that delimit the managed
+// section for localDomain. The domain is wrapped in parentheses so one domain's
+// marker can never be a prefix of another's (e.g. "net" vs "net2") when
+// multiple vppn instances share /etc/hosts.
+func hostMarkers(localDomain string) (begin, end string) {
+	return hostsBegin + "(" + localDomain + ")", hostsEnd + "(" + localDomain + ")"
+}
+
 // updateHosts rewrites the managed vppn section in /etc/hosts using the
 // current peersByIP map. Peers without a Name are skipped.
 func (a *App) updateHosts() {
@@ -36,8 +44,7 @@ func updateHosts(hostsPath, localDomain string, peers map[netip.Addr]*Peer) erro
 	}
 	defer lockFile.Close()
 
-	begin := hostsBegin + localDomain
-	end := hostsEnd + localDomain
+	begin, end := hostMarkers(localDomain)
 
 	info, err := os.Stat(hostsPath)
 	if err != nil {

peer/hosts_test.go

@@ -28,8 +28,7 @@ func readManagedSection(t *testing.T, path, localDomain string) (inside, outside
 	if err != nil {
 		t.Fatal(err)
 	}
-	begin := hostsBegin + localDomain
-	end := hostsEnd + localDomain
+	begin, end := hostMarkers(localDomain)
 
 	inSection := false
 	for _, line := range strings.Split(string(raw), "\n") {
@@ -157,6 +156,45 @@ func TestUpdateHosts_Idempotent(t *testing.T) {
 	}
 }
 
+// TestUpdateHosts_PrefixDomainsCoexist guards finding 4.4: two domains where
+// one label is a prefix of the other ("net" vs "net2") must each manage their
+// own section without clobbering the other's, even sharing one hosts file.
+func TestUpdateHosts_PrefixDomainsCoexist(t *testing.T) {
+	path := writeTempHosts(t, "127.0.0.1 localhost\n")
+
+	if err := updateHosts(path, "net2.local", map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.0.2.1"): peer("a"),
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := updateHosts(path, "net.local", map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.0.1.1"): peer("b"),
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Both sections coexist after writing the prefix domain.
+	if in, _ := readManagedSection(t, path, "net2.local"); len(in) != 1 || in[0] != "10.0.2.1 a.net2.local" {
+		t.Errorf("net2 section clobbered: %v", in)
+	}
+	if in, _ := readManagedSection(t, path, "net.local"); len(in) != 1 || in[0] != "10.0.1.1 b.net.local" {
+		t.Errorf("net section wrong: %v", in)
+	}
+
+	// Re-updating net2 must not disturb the net section.
+	if err := updateHosts(path, "net2.local", map[netip.Addr]*Peer{
+		netip.MustParseAddr("10.0.2.2"): peer("c"),
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if in, _ := readManagedSection(t, path, "net.local"); len(in) != 1 || in[0] != "10.0.1.1 b.net.local" {
+		t.Errorf("net section disturbed by net2 update: %v", in)
+	}
+	if in, _ := readManagedSection(t, path, "net2.local"); len(in) != 1 || in[0] != "10.0.2.2 c.net2.local" {
+		t.Errorf("net2 section not updated: %v", in)
+	}
+}
+
 func contains(ss []string, s string) bool {
 	for _, x := range ss {
 		if x == s {