filter: choose the filtering method via configuration file

This patch changes the current behaviour of the filtering selection.
Up to now, conntrackd has used the kernel version to select the
filtering method based on the following logic: If kernel is >= 2.6.26
we use BSF-based filtering from kernel-space, otherwise, default to
userspace.

However, this filtering method still lacks of IPv6 support and
it requires a patch that got into 2.6.29 to filter IPv6 addresses
from kernel-space. To fix this issue, we default to user-space
filtering and let the user choose the method via the configuration
file.

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

3 files changed, 30 insertions, 6 deletions

diff --git a/doc/sync/alarm/conntrackd.conf b/doc/sync/alarm/conntrackd.conf
index 8d34697..6995d6c 100644
--- a/doc/sync/alarm/conntrackd.conf
+++ b/doc/sync/alarm/conntrackd.conf
@@ -159,8 +159,16 @@ General {
 	# State. The filter is attached to an action that can be: Accept or
 	# Ignore. Thus, you can define the event filtering policy of the
 	# filter-sets in positive or negative logic depending on your needs.
-	#
-	Filter {
+	# You can select if conntrackd filters the event messages from 
+	# user-space or kernel-space. The kernel-space event filtering
+	# saves some CPU cycles by avoiding the copy of the event message
+	# from kernel-space to user-space. The kernel-space event filtering
+	# is prefered, however, you require a Linux kernel >= 2.6.29 to
+	# filter from kernel-space. If you want to select kernel-space 
+	# event filtering, use the keyword 'Kernelspace' instead of 
+	# 'Userspace'.
+	#
+	Filter from Userspace {
 		#
 		# Accept only certain protocols: You may want to replicate
 		# the state of flows depending on their layer 4 protocol.
diff --git a/doc/sync/ftfw/conntrackd.conf b/doc/sync/ftfw/conntrackd.conf
index 06c3d15..3a2ed0e 100644
--- a/doc/sync/ftfw/conntrackd.conf
+++ b/doc/sync/ftfw/conntrackd.conf
@@ -163,8 +163,16 @@ General {
 	# State. The filter is attached to an action that can be: Accept or
 	# Ignore. Thus, you can define the event filtering policy of the
 	# filter-sets in positive or negative logic depending on your needs.
-	#
-	Filter {
+	# You can select if conntrackd filters the event messages from 
+	# user-space or kernel-space. The kernel-space event filtering
+	# saves some CPU cycles by avoiding the copy of the event message
+	# from kernel-space to user-space. The kernel-space event filtering
+	# is prefered, however, you require a Linux kernel >= 2.6.29 to
+	# filter from kernel-space. If you want to select kernel-space 
+	# event filtering, use the keyword 'Kernelspace' instead of 
+	# 'Userspace'.
+	#
+	Filter from Userspace {
 		#
 		# Accept only certain protocols: You may want to replicate
 		# the state of flows depending on their layer 4 protocol.
diff --git a/doc/sync/notrack/conntrackd.conf b/doc/sync/notrack/conntrackd.conf
index 446e981..e9835e8 100644
--- a/doc/sync/notrack/conntrackd.conf
+++ b/doc/sync/notrack/conntrackd.conf
@@ -147,8 +147,16 @@ General {
 	# State. The filter is attached to an action that can be: Accept or
 	# Ignore. Thus, you can define the event filtering policy of the
 	# filter-sets in positive or negative logic depending on your needs.
-	#
-	Filter {
+	# You can select if conntrackd filters the event messages from 
+	# user-space or kernel-space. The kernel-space event filtering
+	# saves some CPU cycles by avoiding the copy of the event message
+	# from kernel-space to user-space. The kernel-space event filtering
+	# is prefered, however, you require a Linux kernel >= 2.6.29 to
+	# filter from kernel-space. If you want to select kernel-space 
+	# event filtering, use the keyword 'Kernelspace' instead of 
+	# 'Userspace'.
+	#
+	Filter from Userspace {
 		#
 		# Accept only certain protocols: You may want to replicate
 		# the state of flows depending on their layer 4 protocol.