Settings > Sources: turn syslog reception on/off, choose UDP/TCP

- SyslogServer opens and closes the UDP/TCP listeners at runtime from the
  configuration saved in /data/syslog.json; a busy port no longer stops
  Logstream, the error is shown in Settings instead.
- Sources tab: syslog section with an on/off switch, UDP and TCP labels,
  the live listening state and the published port (SYSLOG_PORT, passed as
  SYSLOG_PUBLIC_PORT for display; the mapping stays in docker-compose).

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

README.md

@@ -28,6 +28,11 @@ Then open <http://localhost:8080>.
 - **Manual test**: `logger -n 127.0.0.1 -P 514 -d "hello error"` (util-linux) or
   `echo "<14>test ok" | nc -u -w1 127.0.0.1 514`.
 
+**Settings > Sources > Syslog** turns syslog reception on or off and chooses the protocols
+(UDP, TCP) without restarting; the choice is saved in `/data/syslog.json`. It also shows the
+listening state (and the error if the port is already in use). The port itself is published
+by docker-compose: change `SYSLOG_PORT` in `.env`, then run `docker compose up -d`.
+
 Supported formats: RFC 3164 (BSD) and RFC 5424. Over TCP, both "one message per line"
 and "octet counting" (RFC 6587) framing are accepted.
 
@@ -222,6 +227,7 @@ To update one of them:
 | `rdns.go` | cached reverse DNS lookups |
 | `export.go` | streamed CSV export |
 | `docker.go` | Docker container logs (API, followers, positions, level detection) |
+| `syslogserver.go` | syslog listeners opened and closed from Settings > Sources |
 | `tags.go` | color tag storage |
 | `api.go` | `/api/*` HTTP routes |
 | `web/` | UI (HTML, CSS, plain JavaScript, no build step), embedded in the binary; translations live in `web/app.js` (`I18N`) |

api.go

@@ -20,6 +20,7 @@ type API struct {
 	allowPurge bool
 	exportMax  int
 	docker     *DockerManager // nil when DOCKER_LOGS is off
+	syslog     *SyslogServer
 }
 
 func (a *API) Routes(mux *http.ServeMux) {
@@ -37,10 +38,32 @@ func (a *API) Routes(mux *http.ServeMux) {
 	mux.HandleFunc("GET /api/purge", a.purgeStatus)
 	mux.HandleFunc("POST /api/purge", a.purge)
 	mux.HandleFunc("GET /api/export.csv", a.exportCSV)
+	mux.HandleFunc("GET /api/syslog", a.syslogStatus)
+	mux.HandleFunc("PUT /api/syslog", a.syslogConfigure)
 	mux.HandleFunc("GET /api/docker", a.dockerStatus)
 	mux.HandleFunc("PUT /api/docker", a.dockerConfigure)
 }
 
+// GET /api/syslog: syslog reception state (Settings > Sources).
+func (a *API) syslogStatus(w http.ResponseWriter, r *http.Request) {
+	writeJSON(w, http.StatusOK, a.syslog.Status())
+}
+
+// PUT /api/syslog {"enabled": bool, "udp": bool, "tcp": bool}
+func (a *API) syslogConfigure(w http.ResponseWriter, r *http.Request) {
+	var cfg syslogConfig
+	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 4096)).Decode(&cfg); err != nil {
+		writeErr(w, http.StatusBadRequest, err)
+		return
+	}
+	if err := a.syslog.Configure(cfg); err != nil {
+		writeErr(w, http.StatusInternalServerError, err)
+		return
+	}
+	log.Printf("syslog reception changed from %s: %+v", r.RemoteAddr, cfg)
+	writeJSON(w, http.StatusOK, a.syslog.Status())
+}
+
 // GET /api/docker: Docker source state and containers (Settings > Sources).
 func (a *API) dockerStatus(w http.ResponseWriter, r *http.Request) {
 	if a.docker == nil {

docker-compose.yml

@@ -12,6 +12,7 @@ services:
       - "${HTTP_PORT:-8080}:8080"
     environment:
       VLOGS_URL: http://victorialogs:9428
+      SYSLOG_PUBLIC_PORT: ${SYSLOG_PORT:-514}     # shown in Settings > Sources (the mapping is set above)
       TZ: ${TZ:-Europe/Paris}
       AUTH_USER: ${AUTH_USER:-}   # leave empty to disable authentication
       AUTH_PASS: ${AUTH_PASS:-}

main.go

@@ -120,16 +120,15 @@ func main() {
 		store.Enqueue(e)
 		hub.Publish(e)
 	}
-	if err := StartSyslog(ctx, cfg.syslogAddr, sink); err != nil {
-		log.Fatalf("syslog: %v", err)
-	}
+	// Listening errors (port already used…) are shown in Settings > Sources.
+	syslogSrv := NewSyslogServer(ctx, cfg.syslogAddr, getenv("SYSLOG_PUBLIC_PORT", ""), cfg.dataDir, sink)
 
 	static, err := fs.Sub(webFS, "web")
 	if err != nil {
 		log.Fatal(err)
 	}
 	mux := http.NewServeMux()
-	api := &API{store: store, hub: hub, tags: tags, rdns: rdns, allowPurge: cfg.allowPurge, exportMax: cfg.exportMax}
+	api := &API{store: store, hub: hub, tags: tags, rdns: rdns, allowPurge: cfg.allowPurge, exportMax: cfg.exportMax, syslog: syslogSrv}
 	if cfg.dockerLogs {
 		dm, err := NewDockerManager(cfg.dockerHost, cfg.dataDir, cfg.backfill, sink)
 		if err != nil {

syslog.go

@@ -225,30 +225,6 @@ func parseHostTag(e *Entry, s string, withHost bool) {
 	e.Message = s
 }
 
-// StartSyslog starts the UDP and TCP listeners on the same address.
-func StartSyslog(ctx context.Context, addr string, sink func(*Entry)) error {
-	pc, err := net.ListenPacket("udp", addr)
-	if err != nil {
-		return err
-	}
-	ln, err := net.Listen("tcp", addr)
-	if err != nil {
-		pc.Close()
-		return err
-	}
-	if uc, ok := pc.(*net.UDPConn); ok {
-		_ = uc.SetReadBuffer(8 << 20)
-	}
-	go func() {
-		<-ctx.Done()
-		pc.Close()
-		ln.Close()
-	}()
-	go serveUDP(ctx, pc, sink)
-	go serveTCP(ctx, ln, sink)
-	return nil
-}
-
 func serveUDP(ctx context.Context, pc net.PacketConn, sink func(*Entry)) {
 	buf := make([]byte, 65536)
 	for {

syslogserver.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"net"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// syslogConfig is saved in /data/syslog.json and edited in Settings > Sources.
+type syslogConfig struct {
+	Enabled bool `json:"enabled"`
+	UDP     bool `json:"udp"`
+	TCP     bool `json:"tcp"`
+}
+
+// SyslogServer owns the UDP and TCP listeners and opens or closes them when
+// the configuration changes, without restarting Logstream.
+type SyslogServer struct {
+	parent     context.Context
+	addr       string // listening address inside the container, e.g. ":5514"
+	publicPort string // port published on the host by docker-compose (display only)
+	sink       func(*Entry)
+	cfgPath    string
+
+	mu     sync.Mutex
+	cfg    syslogConfig
+	cancel context.CancelFunc
+	pc     net.PacketConn
+	ln     net.Listener
+	errUDP string
+	errTCP string
+}
+
+func NewSyslogServer(ctx context.Context, addr, publicPort, dataDir string, sink func(*Entry)) *SyslogServer {
+	s := &SyslogServer{
+		parent:     ctx,
+		addr:       addr,
+		publicPort: publicPort,
+		sink:       sink,
+		cfgPath:    filepath.Join(dataDir, "syslog.json"),
+		cfg:        syslogConfig{Enabled: true, UDP: true, TCP: true},
+	}
+	if b, err := os.ReadFile(s.cfgPath); err == nil {
+		var cfg syslogConfig
+		if err := json.Unmarshal(b, &cfg); err == nil {
+			s.cfg = cfg
+		}
+	}
+	s.apply()
+	go func() {
+		<-ctx.Done()
+		s.mu.Lock()
+		s.closeLocked()
+		s.mu.Unlock()
+	}()
+	return s
+}
+
+// closeLocked stops the listeners synchronously, so that the port is free
+// before it is opened again; the caller holds the lock.
+func (s *SyslogServer) closeLocked() {
+	if s.cancel != nil {
+		s.cancel() // also closes the open TCP connections
+		s.cancel = nil
+	}
+	if s.pc != nil {
+		s.pc.Close()
+		s.pc = nil
+	}
+	if s.ln != nil {
+		s.ln.Close()
+		s.ln = nil
+	}
+}
+
+// apply opens the listeners required by the configuration.
+func (s *SyslogServer) apply() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.closeLocked()
+	s.errUDP, s.errTCP = "", ""
+	if !s.cfg.Enabled || s.parent.Err() != nil {
+		log.Printf("syslog: reception disabled")
+		return
+	}
+	ctx, cancel := context.WithCancel(s.parent)
+	s.cancel = cancel
+	var open []string
+	if s.cfg.UDP {
+		pc, err := net.ListenPacket("udp", s.addr)
+		if err != nil {
+			s.errUDP = err.Error()
+			log.Printf("syslog udp: %v", err)
+		} else {
+			if uc, ok := pc.(*net.UDPConn); ok {
+				_ = uc.SetReadBuffer(8 << 20)
+			}
+			s.pc = pc
+			go serveUDP(ctx, pc, s.sink)
+			open = append(open, "udp")
+		}
+	}
+	if s.cfg.TCP {
+		ln, err := net.Listen("tcp", s.addr)
+		if err != nil {
+			s.errTCP = err.Error()
+			log.Printf("syslog tcp: %v", err)
+		} else {
+			s.ln = ln
+			go serveTCP(ctx, ln, s.sink)
+			open = append(open, "tcp")
+		}
+	}
+	log.Printf("syslog: listening on %s %v", s.addr, open)
+}
+
+// Configure saves and applies a new configuration.
+func (s *SyslogServer) Configure(cfg syslogConfig) error {
+	s.mu.Lock()
+	s.cfg = cfg
+	s.mu.Unlock()
+	s.apply()
+	return writeJSONFile(s.cfgPath, cfg)
+}
+
+// Status is the state shown in Settings > Sources.
+func (s *SyslogServer) Status() map[string]any {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return map[string]any{
+		"enabled":      s.cfg.Enabled,
+		"udp":          s.cfg.UDP,
+		"tcp":          s.cfg.TCP,
+		"udpListening": s.pc != nil,
+		"tcpListening": s.ln != nil,
+		"udpError":     s.errUDP,
+		"tcpError":     s.errTCP,
+		"port":         s.publicPort,
+		"internalAddr": s.addr,
+	}
+}

web/app.js

@@ -67,6 +67,12 @@ const I18N = {
     fHostName: 'host name (DNS)', fHostIp: 'host IP',
     clickHost: 'Click to filter on this host', clickApp: 'Click to filter on this app',
     sourceAria: 'Source', srcAll: 'All sources', tabSources: 'Sources',
+    syslogEnabled: 'Receive syslog messages', syslogProtocols: 'Protocols', syslogPort: 'Port',
+    syslogListening: ({ port, protos }) => `Listening on port ${port} (${protos}).`,
+    syslogOff: 'Syslog reception is off: syslog messages are ignored (Docker logs are still collected).',
+    syslogNone: 'No protocol selected: syslog messages are ignored.',
+    syslogErr: (p) => `Cannot listen over ${p}: `,
+    syslogPortHelp: (i) => `Published by docker-compose (container port ${i}). To change it, set SYSLOG_PORT in .env, then run docker compose up -d.`,
     dockerTitle: 'Docker containers',
     dockerDefault: 'Follow new containers automatically',
     dockerAll: 'Enable all', dockerNone: 'Disable all',
@@ -171,6 +177,12 @@ const I18N = {
     fHostName: 'nom d\'hôte (DNS)', fHostIp: 'IP de l\'hôte',
     clickHost: 'Cliquer pour filtrer sur cet hôte', clickApp: 'Cliquer pour filtrer sur cette appli',
     sourceAria: 'Source', srcAll: 'Toutes les sources', tabSources: 'Sources',
+    syslogEnabled: 'Recevoir les messages syslog', syslogProtocols: 'Protocoles', syslogPort: 'Port',
+    syslogListening: ({ port, protos }) => `Écoute sur le port ${port} (${protos}).`,
+    syslogOff: 'Réception syslog désactivée : les messages syslog sont ignorés (les logs Docker sont toujours collectés).',
+    syslogNone: 'Aucun protocole sélectionné : les messages syslog sont ignorés.',
+    syslogErr: (p) => `Impossible d'écouter en ${p} : `,
+    syslogPortHelp: (i) => `Publié par docker-compose (port ${i} dans le conteneur). Pour le changer, modifiez SYSLOG_PORT dans .env, puis lancez docker compose up -d.`,
     dockerTitle: 'Conteneurs Docker',
     dockerDefault: 'Suivre automatiquement les nouveaux conteneurs',
     dockerAll: 'Tout activer', dockerNone: 'Tout désactiver',
@@ -395,6 +407,7 @@ function setLang(next) {
   renderTimeSettings();
   renderPurge();
   renderInterface();
+  renderSyslog();
   renderDocker();
 }
 
@@ -1095,6 +1108,66 @@ $('#exportMenu').addEventListener('click', (ev) => {
 document.addEventListener('click', (ev) => { if (!ev.target.closest('.export')) setExportMenu(false); });
 document.addEventListener('keydown', (ev) => { if (ev.key === 'Escape') setExportMenu(false); });
 
+/* ================= Syslog source ================= */
+
+let syslogState = null;
+
+async function loadSyslog() {
+  try { syslogState = await api('/api/syslog'); } catch { syslogState = null; }
+  renderSyslog();
+}
+
+function renderSyslog() {
+  const s = syslogState;
+  const status = $('#syslogStatus');
+  if (!s) { status.textContent = ''; return; }
+  $('#syslogEnabled').checked = s.enabled;
+  for (const b of document.querySelectorAll('#syslogProtos [data-proto]')) {
+    const on = !!s[b.dataset.proto];
+    b.classList.toggle('on', on);
+    b.setAttribute('aria-pressed', String(on));
+    b.disabled = !s.enabled;
+  }
+  $('#syslogProtos').classList.toggle('off', !s.enabled);
+  $('#syslogPortVal').textContent = s.port || s.internalAddr;
+  const internal = String(s.internalAddr || '').replace(/^:/, '');
+  $('#syslogPortHelp').textContent = t('syslogPortHelp', internal);
+
+  const errs = [];
+  if (s.udpError) errs.push(t('syslogErr', 'UDP') + s.udpError);
+  if (s.tcpError) errs.push(t('syslogErr', 'TCP') + s.tcpError);
+  const protos = [s.udpListening && 'UDP', s.tcpListening && 'TCP'].filter(Boolean).join(' + ');
+  if (errs.length) {
+    status.textContent = errs.join(' · ');
+    status.className = 'docker-status bad';
+  } else if (!s.enabled) {
+    status.textContent = t('syslogOff');
+    status.className = 'docker-status muted';
+  } else if (!protos) {
+    status.textContent = t('syslogNone');
+    status.className = 'docker-status muted';
+  } else {
+    status.textContent = t('syslogListening', { port: s.port || internal, protos });
+    status.className = 'docker-status good';
+  }
+}
+
+async function configureSyslog(change) {
+  const s = syslogState || { enabled: true, udp: true, tcp: true };
+  const body = { enabled: s.enabled, udp: s.udp, tcp: s.tcp, ...change };
+  syslogState = { ...s, ...body };
+  renderSyslog();
+  try { syslogState = await api('/api/syslog', { method: 'PUT', body }); } catch (e) { toast(e.message); }
+  renderSyslog();
+}
+
+$('#syslogEnabled').addEventListener('change', (ev) => configureSyslog({ enabled: ev.target.checked }));
+$('#syslogProtos').addEventListener('click', (ev) => {
+  const b = ev.target.closest('[data-proto]');
+  if (!b || b.disabled || !syslogState) return;
+  configureSyslog({ [b.dataset.proto]: !syslogState[b.dataset.proto] });
+});
+
 /* ================= Docker source ================= */
 
 let dockerState = null;
@@ -1370,6 +1443,7 @@ $('#settingsBtn').addEventListener('click', () => {
   renderTagList();
   renderInterface();
   loadPurgeStatus();
+  loadSyslog();
   loadDocker();
   showSettingsTab(store.get('settingsTab', 'locale'));
   $('#settingsDlg').showModal();

web/index.html

@@ -178,6 +178,24 @@
 
           <!-- Sources -->
           <div class="set-panel" role="tabpanel" data-panel="sources" hidden>
+            <section class="set-section">
+              <h3>Syslog</h3>
+              <p id="syslogStatus" class="docker-status"></p>
+              <label class="switch-row">
+                <input id="syslogEnabled" type="checkbox" class="switch">
+                <span data-i18n="syslogEnabled">Receive syslog messages</span>
+              </label>
+              <div class="sl-grid">
+                <span class="lbl" data-i18n="syslogProtocols">Protocols</span>
+                <div id="syslogProtos" class="chip-field sl-protos">
+                  <button type="button" class="chip" data-proto="udp" style="--h:205">UDP</button>
+                  <button type="button" class="chip" data-proto="tcp" style="--h:265">TCP</button>
+                </div>
+                <span class="lbl" data-i18n="syslogPort">Port</span>
+                <div class="sl-port"><code id="syslogPortVal">514</code><span id="syslogPortHelp" class="muted small"></span></div>
+              </div>
+            </section>
+
             <section class="set-section">
               <h3 data-i18n="dockerTitle">Docker containers</h3>
               <p id="dockerStatus" class="docker-status"></p>

web/style.css

@@ -426,6 +426,14 @@ select.field:focus { outline: 0; border-color: var(--accent); box-shadow: 0 0 0
 .docker-status.bad { color: var(--sev-err); }
 .switch-row { display: flex; align-items: center; gap: 10px; font-size: 13px; font-weight: 550; cursor: pointer; }
 .dk-opts { display: flex; flex-direction: column; gap: 8px; }
+.sl-grid { display: grid; grid-template-columns: max-content minmax(0, 1fr); gap: 12px 14px; align-items: baseline; margin-top: 14px; }
+.sl-protos { display: inline-flex; min-height: 0; padding: 5px; justify-self: start; }
+.sl-protos.off { opacity: .5; }
+.sl-port { display: flex; flex-direction: column; align-items: flex-start; gap: 5px; }
+.sl-port code {
+  font: 12px var(--mono); padding: 2px 8px; border-radius: 5px;
+  background: var(--panel-2); border: 1px solid var(--border);
+}
 .dk-toolbar { display: flex; align-items: center; gap: 12px; margin: 14px 0 6px; }
 .dk-filter {
   flex: 1; min-width: 0; height: 28px; padding: 0 10px;