systemd support

How does it work? I don't know. Does it work? I don't know.
Would I encourage its use? No.

dnscrypt-proxy/config.go

@@ -136,7 +136,7 @@ func ConfigLoad(proxy *Proxy, svcFlag *string, config_file string) error {
 	proxy.certRefreshDelayAfterFailure = time.Duration(10 * time.Second)
 	proxy.certIgnoreTimestamp = config.CertIgnoreTimestamp
 	if len(config.ListenAddresses) == 0 {
-		return errors.New("No local IP/port configured")
+		dlog.Debugf("No local IP/port configured")
 	}
 	proxy.listenAddresses = config.ListenAddresses
 	proxy.daemonize = config.Daemonize

dnscrypt-proxy/dnscrypt-proxy.toml

@@ -18,7 +18,7 @@
 
 
 ## List of local addresses and ports to listen to. Can be IPv4 and/or IPv6.
-
+## To only use systemd activation sockets, use an empty set: []
 listen_addresses = ['127.0.0.1:53', '[::1]:53']
 
 

dnscrypt-proxy/main.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/coreos/go-systemd/activation"
 	"github.com/coreos/go-systemd/daemon"
 	"github.com/jedisct1/dlog"
 	"github.com/kardianos/service"
@@ -165,6 +166,9 @@ func (proxy *Proxy) StartProxy() {
 			dlog.Fatal(err)
 		}
 	}
+	if err := proxy.systemDListeners(); err != nil {
+		dlog.Fatal(err)
+	}
 	liveServers, err := proxy.serversInfo.refresh(proxy)
 	if liveServers > 0 {
 		dlog.Noticef("dnscrypt-proxy is ready - live servers: %d", liveServers)
@@ -261,6 +265,24 @@ func (proxy *Proxy) tcpListenerFromAddr(listenAddr *net.TCPAddr) error {
 	return nil
 }
 
+func (proxy *Proxy) systemDListeners() error {
+	listeners, err := activation.Listeners(true)
+	if err != nil && len(listeners) > 0 {
+		for i, listener := range listeners {
+			dlog.Noticef("Wiring systemd TCP socket #%d", i)
+			proxy.tcpListener(listener.(*net.TCPListener))
+		}
+	}
+	packetConns, err := activation.PacketConns(true)
+	if err != nil && len(packetConns) > 0 {
+		for i, packetConn := range packetConns {
+			dlog.Noticef("Wiring systemd UDP socket #%d", i)
+			proxy.udpListener(packetConn.(*net.UDPConn))
+		}
+	}
+	return nil
+}
+
 func (proxy *Proxy) exchangeWithUDPServer(serverInfo *ServerInfo, encryptedQuery []byte, clientNonce []byte) ([]byte, error) {
 	pc, err := net.DialUDP("udp", nil, serverInfo.UDPAddr)
 	if err != nil {

systemd/dnscrypt-proxy.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=DNSCrypt client proxy
+Documentation=man:dnscrypt-proxy(8)
+Requires=dnscrypt-proxy.socket
+After=network.target
+Before=nss-lookup.target
+
+[Install]
+Also=dnscrypt-proxy.socket
+WantedBy=multi-user.target
+
+[Service]
+Type=simple
+NonBlocking=true
+
+# Change this
+ExecStart=/opt/dnscrypt-proxy/dnscrypt-proxy

systemd/dnscrypt-proxy.socket

@@ -0,0 +1,11 @@
+[Unit]
+Description=dnscrypt-proxy listening socket
+
+[Socket]
+ListenStream=127.0.0.1:53
+ListenDatagram=127.0.0.1:53
+NoDelay=true
+DeferAcceptSec=1
+
+[Install]
+WantedBy=sockets.target