netfilter: nf_conntrack_tstamp: add flow-based timestamp extension

This patch adds flow-based timestamping for conntracks. This
conntrack extension is disabled by default. Basically, we use
two 64-bits variables to store the creation timestamp once the
conntrack has been confirmed and the other to store the deletion
time. This extension is disabled by default, to enable it, you
have to:

echo 1 > /proc/sys/net/netfilter/nf_conntrack_timestamp

This patch allows to save memory for user-space flow-based
loogers such as ulogd2. In short, ulogd2 does not need to
keep a hashtable with the conntrack in user-space to know
when they were created and destroyed, instead we use the
kernel timestamp. If we want to have a sane IPFIX implementation
in user-space, this nanosecs resolution timestamps are also
useful. Other custom user-space applications can benefit from
this via libnetfilter_conntrack.

This patch modifies the /proc output to display the delta time
in seconds since the flow start. You can also obtain the
flow-start date by means of the conntrack-tools.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index 5cf8a8c141aa..341eb089349e 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -21,11 +21,13 @@ struct netns_ct {
         int                     sysctl_events;
         unsigned int            sysctl_events_retry_timeout;
         int                     sysctl_acct;
+        int                     sysctl_tstamp;
         int                     sysctl_checksum;
         unsigned int            sysctl_log_invalid; /* Log invalid packets */
 #ifdef CONFIG_SYSCTL
         struct ctl_table_header *sysctl_header;
         struct ctl_table_header *acct_sysctl_header;
+        struct ctl_table_header *tstamp_sysctl_header;
         struct ctl_table_header *event_sysctl_header;
 #endif
         char                    *slabname;