A website on every address steps aside for websites that name an address on the same port

The wildcard then listens on the machine's other addresses only, in the built-in proxy and in Traefik,
and follows the machine when it gains or loses an address.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

traefik.go

@@ -49,7 +49,8 @@ type traefikMgr struct {
 	stop      context.CancelFunc // stops the current traefik process
 	lastErr   string
 	maps      map[string]*mapState
-	ports     map[string]int // mapping ID -> relay port, kept stable across edits so Traefik's backend URL never changes
+	binds     map[string][]string // mapping ID -> the addresses it listens on (a wildcard steps aside for named ones)
+	ports     map[string]int      // mapping ID -> relay port, kept stable across edits so Traefik's backend URL never changes
 	dynBytes  []byte
 }
 
@@ -217,20 +218,23 @@ func hostRule(host string) (string, bool) {
 
 // sync rewrites Traefik's configuration for the given web mappings and
 // (re)starts the process if its static part changed. Called with b.mu held.
-func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, acmeEmail string, staging bool) {
+func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, binds map[string][]string, acmeEmail string, staging bool) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
+	t.binds = binds
 	t.maps = map[string]*mapState{}
 	eps := map[string]string{} // name -> address
 	needACME := false
 	for _, ms := range maps {
 		t.maps[ms.m.ID] = ms
-		eps[epName(ms.m.BindIP, ms.m.Port)] = net.JoinHostPort(ms.m.BindIP, strconv.Itoa(ms.m.Port))
+		for _, ip := range t.bindsOf(ms.m) {
+			eps[epName(ip, ms.m.Port)] = net.JoinHostPort(ip, strconv.Itoa(ms.m.Port))
+			if ms.m.Proto == model.ProtoHTTPS && ms.m.RedirectHTTP {
+				eps[epName(ip, 80)] = net.JoinHostPort(ip, "80")
+			}
+		}
 		if ms.m.Proto == model.ProtoHTTPS {
 			needACME = true
-			if ms.m.RedirectHTTP {
-				eps[epName(ms.m.BindIP, 80)] = net.JoinHostPort(ms.m.BindIP, "80")
-			}
 		}
 	}
 	routers := map[string]any{}
@@ -244,7 +248,11 @@ func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, acmeEmail strin
 			continue
 		}
 		rule, wildcard := hostRule(m.Hostname)
-		ep := epName(m.BindIP, m.Port)
+		var mainEPs, redirEPs []string
+		for _, ip := range t.bindsOf(m) {
+			mainEPs = append(mainEPs, epName(ip, m.Port))
+			redirEPs = append(redirEPs, epName(ip, 80))
+		}
 		prio := 5000
 		if wildcard {
 			prio = 2000
@@ -274,7 +282,7 @@ func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, acmeEmail strin
 			mws["host-"+m.ID] = map[string]any{"headers": map[string]any{"customRequestHeaders": map[string]string{"Host": m.RewriteHost}}}
 			chain = append(chain, "host-"+m.ID)
 		}
-		router := map[string]any{"rule": rule, "entryPoints": []string{ep}, "service": "s-" + m.ID, "middlewares": chain, "priority": prio}
+		router := map[string]any{"rule": rule, "entryPoints": mainEPs, "service": "s-" + m.ID, "middlewares": chain, "priority": prio}
 		var tlsCfg map[string]any
 		if m.Proto == model.ProtoHTTPS {
 			tlsCfg = map[string]any{}
@@ -292,7 +300,7 @@ func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, acmeEmail strin
 			services["g-"+m.ID] = map[string]any{"loadBalancer": map[string]any{
 				"servers": []map[string]string{{"url": fmt.Sprintf("http://127.0.0.1:%d", t.gatePort)}}, "passHostHeader": true}}
 			mws["gate-"+m.ID] = map[string]any{"headers": map[string]any{"customRequestHeaders": map[string]string{"X-Hammerhead-Mapping": m.ID}}}
-			g := map[string]any{"rule": rule + " && PathPrefix(`/.hammerhead/`)", "entryPoints": []string{ep}, "service": "g-" + m.ID,
+			g := map[string]any{"rule": rule + " && PathPrefix(`/.hammerhead/`)", "entryPoints": mainEPs, "service": "g-" + m.ID,
 				"middlewares": []string{"gate-" + m.ID}, "priority": prio + 1000}
 			if tlsCfg != nil {
 				g["tls"] = tlsCfg
@@ -305,7 +313,7 @@ func (t *traefikMgr) sync(ctx context.Context, maps []*mapState, acmeEmail strin
 				redirPort = strconv.Itoa(m.Port)
 			}
 			mws["redir-"+m.ID] = map[string]any{"redirectScheme": map[string]any{"scheme": "https", "port": redirPort, "permanent": true}}
-			routers["r-"+m.ID] = map[string]any{"rule": rule, "entryPoints": []string{epName(m.BindIP, 80)}, "service": "noop@internal",
+			routers["r-"+m.ID] = map[string]any{"rule": rule, "entryPoints": redirEPs, "service": "noop@internal",
 				"middlewares": []string{"redir-" + m.ID}, "priority": prio}
 		}
 	}
@@ -545,10 +553,7 @@ func (t *traefikMgr) probeCerts(ctx context.Context) {
 		t.mu.Unlock()
 		changed := false
 		for _, ms := range targets {
-			ip := ms.m.BindIP
-			if pip := net.ParseIP(ip); pip != nil && pip.IsUnspecified() {
-				ip = "127.0.0.1"
-			}
+			ip := t.probeAddr(ms.m)
 			status := t.probeOne(net.JoinHostPort(ip, strconv.Itoa(ms.m.Port)), ms.m.Hostname)
 			t.b.mu.Lock()
 			if t.b.acme.certs == nil {
@@ -598,3 +603,27 @@ func containsStr(list []string, s string) bool {
 	}
 	return false
 }
+
+// bindsOf is the addresses a web mapping listens on; t.mu is held, or the caller does not race sync.
+func (t *traefikMgr) bindsOf(m model.Mapping) []string {
+	if ips := t.binds[m.ID]; len(ips) > 0 {
+		return ips
+	}
+	return []string{m.BindIP}
+}
+
+// probeAddr picks an address on this machine to test a mapping's certificate through.
+func (t *traefikMgr) probeAddr(m model.Mapping) string {
+	t.mu.Lock()
+	ips := t.bindsOf(m)
+	t.mu.Unlock()
+	for _, ip := range ips {
+		if ip == "127.0.0.1" {
+			return ip
+		}
+	}
+	if p := net.ParseIP(ips[0]); p != nil && p.IsUnspecified() {
+		return "127.0.0.1"
+	}
+	return ips[0]
+}