.. SPDX-License-Identifier: GPL-2.0
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Netfilter Conntrack Sysfs variables
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/proc/sys/net/netfilter/nf_conntrack_* Variables:
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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. The hash table will
never have fewer than 1024 and never more than 262144 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
- 1 - enabled
- 2 - auto (default)
If this option is enabled, the connection tracking code will
provide userspace with connection tracking events via ctnetlink.
The default allocates the extension if a userspace program is
listening to ctnetlink events.
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_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
Maximum number of allowed connection tracking entries. This value is set
to nf_conntrack_buckets by default.
Note that connection tracking entries are added to the table twice -- once
for the original direction and once for the reply direction (i.e., with
the reversed address). This means that with default settings a maxed-out
table will have a average hash chain length of 2, not 1.
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_ignore_invalid_rst - BOOLEAN
- 0 - disabled (default)
- 1 - enabled
If it's 1, we don't mark 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_sctp_timeout_closed - INTEGER (seconds)
default 10
nf_conntrack_sctp_timeout_cookie_wait - INTEGER (seconds)
default 3
nf_conntrack_sctp_timeout_cookie_echoed - INTEGER (seconds)
default 3
nf_conntrack_sctp_timeout_established - INTEGER (seconds)
default 210
Default is set to (hb_interval * path_max_retrans + rto_max)
nf_conntrack_sctp_timeout_shutdown_sent - INTEGER (seconds)
default 3
nf_conntrack_sctp_timeout_shutdown_recd - INTEGER (seconds)
default 3
nf_conntrack_sctp_timeout_shutdown_ack_sent - INTEGER (seconds)
default 3
nf_conntrack_sctp_timeout_heartbeat_sent - INTEGER (seconds)
default 30
This timeout is used to setup conntrack entry on secondary paths.
Default is set to hb_interval.
nf_conntrack_udp_timeout - INTEGER (seconds)
default 30
nf_conntrack_udp_timeout_stream - INTEGER (seconds)
default 120
This extended timeout will be used in case there is an UDP stream
detected.
nf_conntrack_gre_timeout - INTEGER (seconds)
default 30
nf_conntrack_gre_timeout_stream - INTEGER (seconds)
default 180
This extended timeout will be used in case there is an GRE stream
detected.
nf_hooks_lwtunnel - BOOLEAN
- 0 - disabled (default)
- not 0 - enabled
If this option is enabled, the lightweight tunnel netfilter hooks are
enabled. This option cannot be disabled once it is enabled.
nf_flowtable_tcp_timeout - INTEGER (seconds)
default 30
Control offload timeout for tcp connections.
TCP connections may be offloaded from nf conntrack to nf flow table.
Once aged, the connection is returned to nf conntrack.
nf_flowtable_udp_timeout - INTEGER (seconds)
default 30
Control offload timeout for udp connections.
UDP connections may be offloaded from nf conntrack to nf flow table.
Once aged, the connection is returned to nf conntrack.
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