Create systemd socket activation.

In future the socket activation IMHO should be standard way of starting
cjdns. Thanks to that configurators don't have to know anything about
cjdroute placement to start cjdns.

contrib/bash/cjdns-trap.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+PIPE_NAME="client-core-$(tr -cd 'a-f0-9' < /dev/urandom | head -c 8)"
+(sleep 1 && /usr/bin/env cjdroute core "$PIPE_NAME" > /dev/null) &
+nc -lU "/tmp/cjdns_pipe_$PIPE_NAME"

contrib/systemd/README.md

@@ -0,0 +1,6 @@
+## How to install
+
+```bash
+mv contrib/systemd/cjdns* /usr/lib/systemd/systemd/
+mv conrtib/bash/cjdns-trap.sh /usr/lib/systemd/scripts/
+```

contrib/systemd/cjdns.socket

@@ -0,0 +1,11 @@
+[Unit]
+Description=Cjdns activation socket.
+
+[Socket]
+ListenStream=/run/cjdns/cjdns.socket
+Accept=true
+SocketMode=0600
+
+[Install]
+WantedBy=sockets.target
+

contrib/systemd/cjdns@.service

@@ -0,0 +1,16 @@
+[Unit]
+Description=cjdns-multinstant: routing engine designed for security, scalability, speed and ease of use
+Wants=network.target
+After=network.target
+Requires=cjdns.socket
+
+[Service]
+ProtectHome=true
+ProtectSystem=true
+SyslogIdentifier=cjdroute
+
+Type=forking
+ExecStart=/usr/lib/systemd/scripts/cjdns-trap.sh
+StandardInput=socket
+StandardOutput=socket
+StandardError=journal