stream: Add basic stream service for systemd sockets

This allows systemd socket activation by passing URIs such as systemd://foo
to plugins such as VICI.

For example setting charon.plugins.vici.socket = systemd://vici, a
systemd socket file descriptor with the name "vici" will be picked up.

So these would be the corresponding unit options:

  [Socket]
  FileDescriptorName=vici
  Service=strongswan.service

  ListenStream=/run/charon.vici

The implementation currently is very basic and right now only the first
file descriptor for a particular identifier is picked up if there are
multiple socket units with the same FileDescriptorName.

Signed-off-by: aszlig <[email protected]>

Closes strongswan/strongswan#79.

src/libstrongswan/Makefile.am

@@ -96,6 +96,7 @@ fetcher/fetcher_manager.h eap/eap.h pen/pen.h ipsec/ipsec_types.h \
 networking/host.h networking/host_resolver.h networking/packet.h \
 networking/tun_device.h networking/streams/stream.h \
 networking/streams/stream_unix.h networking/streams/stream_service_unix.h \
+networking/streams/stream_service_systemd.h \
 networking/streams/stream_tcp.h networking/streams/stream_service_tcp.h \
 networking/streams/stream_service.h networking/streams/stream_manager.h \
 resolver/resolver.h resolver/resolver_response.h resolver/rr_set.h \
@@ -192,6 +193,12 @@ if USE_LIBCAP
   libstrongswan_la_LIBADD += -lcap
 endif
 
+if USE_SYSTEMD
+  AM_CPPFLAGS += $(systemd_CFLAGS) -DUSE_SYSTEMD
+  libstrongswan_la_SOURCES += networking/streams/stream_service_systemd.c
+  libstrongswan_la_LIBADD += $(systemd_LIBS)
+endif
+
 EXTRA_DIST = \
 asn1/oid.txt asn1/oid.pl \
 crypto/proposal/proposal_keywords_static.txt \