conntrackd: add cthelper infrastructure (+ example FTP helper)

This patch adds the user-space helper infrastructure. It also
contains the implementation of the FTP helper in user-space.

There's one example file that you can use to configure conntrackd
as user-space connection tracking helper under:

 doc/helper/conntrackd.conf

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/doc/helper/conntrackd.conf b/doc/helper/conntrackd.conf
new file mode 100644
index 0000000..711b309
--- /dev/null
+++ b/doc/helper/conntrackd.conf
@@ -0,0 +1,82 @@
+#
+# Helper settings
+#
+
+Helper {
+	# Before this, you have to make sure you have registered the `ftp'
+	# user-space helper stub via:
+	#
+	# nfct helper add ftp inet tcp
+	#
+	Type ftp inet tcp {
+		#
+		# Set NFQUEUE number you want to use to receive traffic from
+		# the kernel.
+		#
+		QueueNum 0
+		#
+		# Set the Expectation policy for this helper.
+		#
+		Policy ftp {
+			#
+			# Maximum number of simultaneous expectations
+			#
+			ExpectMax 1
+			#
+			# Maximum living time for one expectation (in seconds).
+			#
+			ExpectTimeout 300
+		}
+	}
+}
+
+#
+# General settings
+#
+General {
+	#
+	# Set the nice value of the daemon, this value goes from -20
+	# (most favorable scheduling) to 19 (least favorable). Using a
+	# very low value reduces the chances to lose state-change events.
+	# Default is 0 but this example file sets it to most favourable
+	# scheduling as this is generally a good idea. See man nice(1) for
+	# more information.
+	#
+	Nice -20
+
+	#
+	# Select a different scheduler for the daemon, you can select between
+	# RR and FIFO and the process priority (minimum is 0, maximum is 99).
+	# See man sched_setscheduler(2) for more information. Using a RT
+	# scheduler reduces the chances to overrun the Netlink buffer.
+	#
+	# Scheduler {
+	#	Type FIFO
+	#	Priority 99
+	# }
+
+	#
+	# Logfile: on (/var/log/conntrackd.log), off, or a filename
+	# Default: off
+	#
+	LogFile on
+
+	#
+	# Syslog: on, off or a facility name (daemon (default) or local0..7)
+	# Default: off
+	#
+	#Syslog on
+
+	#
+	# Lockfile
+	#
+	LockFile /var/lock/conntrack.lock
+
+	#
+	# Unix socket configuration
+	#
+	UNIX {
+		Path /var/run/conntrackd.ctl
+		Backlog 20
+	}
+}