linux/Documentation/networking/nf_conntrack-sysctl.txt
Florian Westphal 481fa37347 netfilter: conntrack: add nf_conntrack_default_on sysctl
This switch (default on) can be used to disable automatic registration
of connection tracking functionality in newly created network
namespaces.

This means that when net namespace goes down (or the tracker protocol
module is unloaded) we *might* have to unregister the hooks.

We can either add another per-netns variable that tells if
the hooks got registered by default, or, alternatively, just call
the protocol _put() function and have the callee deal with a possible
'extra' put() operation that doesn't pair with a get() one.

This uses the latter approach, i.e. a put() without a get has no effect.

Conntrack is still enabled automatically regardless of the new sysctl
setting if the new net namespace requires connection tracking, e.g. when
NAT rules are created.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2016-12-04 21:17:25 +01:00

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/proc/sys/net/netfilter/nf_conntrack_* Variables:
nf_conntrack_acct - BOOLEAN
0 - disabled (default)
not 0 - enabled
Enable connection tracking flow accounting. 64-bit byte and packet
counters per flow are added.
nf_conntrack_buckets - INTEGER
Size of hash table. If not specified as parameter during module
loading, the default size is calculated by dividing total memory
by 16384 to determine the number of buckets but the hash table will
never have fewer than 32 and limited to 16384 buckets. For systems
with more than 4GB of memory it will be 65536 buckets.
This sysctl is only writeable in the initial net namespace.
nf_conntrack_checksum - BOOLEAN
0 - disabled
not 0 - enabled (default)
Verify checksum of incoming packets. Packets with bad checksums are
in INVALID state. If this is enabled, such packets will not be
considered for connection tracking.
nf_conntrack_count - INTEGER (read-only)
Number of currently allocated flow entries.
nf_conntrack_events - BOOLEAN
0 - disabled
not 0 - enabled (default)
If this option is enabled, the connection tracking code will
provide userspace with connection tracking events via ctnetlink.
nf_conntrack_expect_max - INTEGER
Maximum size of expectation table. Default value is
nf_conntrack_buckets / 256. Minimum is 1.
nf_conntrack_frag6_high_thresh - INTEGER
default 262144
Maximum memory used to reassemble IPv6 fragments. When
nf_conntrack_frag6_high_thresh bytes of memory is allocated for this
purpose, the fragment handler will toss packets until
nf_conntrack_frag6_low_thresh is reached.
nf_conntrack_frag6_low_thresh - INTEGER
default 196608
See nf_conntrack_frag6_low_thresh
nf_conntrack_frag6_timeout - INTEGER (seconds)
default 60
Time to keep an IPv6 fragment in memory.
nf_conntrack_generic_timeout - INTEGER (seconds)
default 600
Default for generic timeout. This refers to layer 4 unknown/unsupported
protocols.
nf_conntrack_helper - BOOLEAN
0 - disabled (default)
not 0 - enabled
Enable automatic conntrack helper assignment.
If disabled it is required to set up iptables rules to assign
helpers to connections. See the CT target description in the
iptables-extensions(8) man page for further information.
nf_conntrack_icmp_timeout - INTEGER (seconds)
default 30
Default for ICMP timeout.
nf_conntrack_icmpv6_timeout - INTEGER (seconds)
default 30
Default for ICMP6 timeout.
nf_conntrack_log_invalid - INTEGER
0 - disable (default)
1 - log ICMP packets
6 - log TCP packets
17 - log UDP packets
33 - log DCCP packets
41 - log ICMPv6 packets
136 - log UDPLITE packets
255 - log packets of any protocol
Log invalid packets of a type specified by value.
nf_conntrack_max - INTEGER
Size of connection tracking table. Default value is
nf_conntrack_buckets value * 4.
nf_conntrack_default_on - BOOLEAN
0 - don't register conntrack in new net namespaces
1 - register conntrack in new net namespaces (default)
This controls wheter newly created network namespaces have connection
tracking enabled by default. It will be enabled automatically
regardless of this setting if the new net namespace requires
connection tracking, e.g. when NAT rules are created.
This setting is only visible in initial user namespace, it has no
effect on existing namespaces.
nf_conntrack_tcp_be_liberal - BOOLEAN
0 - disabled (default)
not 0 - enabled
Be conservative in what you do, be liberal in what you accept from others.
If it's non-zero, we mark only out of window RST segments as INVALID.
nf_conntrack_tcp_loose - BOOLEAN
0 - disabled
not 0 - enabled (default)
If it is set to zero, we disable picking up already established
connections.
nf_conntrack_tcp_max_retrans - INTEGER
default 3
Maximum number of packets that can be retransmitted without
received an (acceptable) ACK from the destination. If this number
is reached, a shorter timer will be started.
nf_conntrack_tcp_timeout_close - INTEGER (seconds)
default 10
nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
default 60
nf_conntrack_tcp_timeout_established - INTEGER (seconds)
default 432000 (5 days)
nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
default 120
nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
default 30
nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
default 300
nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
default 60
nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
default 120
nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
default 120
nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
default 300
nf_conntrack_timestamp - BOOLEAN
0 - disabled (default)
not 0 - enabled
Enable connection tracking flow timestamping.
nf_conntrack_udp_timeout - INTEGER (seconds)
default 30
nf_conntrack_udp_timeout_stream2 - INTEGER (seconds)
default 180
This extended timeout will be used in case there is an UDP stream
detected.