1 .. SPDX-License-Identifier: GPL-2.0
3 ===================================
4 Netfilter Conntrack Sysfs variables
5 ===================================
7 /proc/sys/net/netfilter/nf_conntrack_* Variables:
8 =================================================
10 nf_conntrack_acct - BOOLEAN
11 - 0 - disabled (default)
14 Enable connection tracking flow accounting. 64-bit byte and packet
15 counters per flow are added.
17 nf_conntrack_buckets - INTEGER
18 Size of hash table. If not specified as parameter during module
19 loading, the default size is calculated by dividing total memory
20 by 16384 to determine the number of buckets but the hash table will
21 never have fewer than 32 and limited to 16384 buckets. For systems
22 with more than 4GB of memory it will be 65536 buckets.
23 This sysctl is only writeable in the initial net namespace.
25 nf_conntrack_checksum - BOOLEAN
27 - not 0 - enabled (default)
29 Verify checksum of incoming packets. Packets with bad checksums are
30 in INVALID state. If this is enabled, such packets will not be
31 considered for connection tracking.
33 nf_conntrack_count - INTEGER (read-only)
34 Number of currently allocated flow entries.
36 nf_conntrack_events - BOOLEAN
38 - not 0 - enabled (default)
40 If this option is enabled, the connection tracking code will
41 provide userspace with connection tracking events via ctnetlink.
43 nf_conntrack_expect_max - INTEGER
44 Maximum size of expectation table. Default value is
45 nf_conntrack_buckets / 256. Minimum is 1.
47 nf_conntrack_frag6_high_thresh - INTEGER
50 Maximum memory used to reassemble IPv6 fragments. When
51 nf_conntrack_frag6_high_thresh bytes of memory is allocated for this
52 purpose, the fragment handler will toss packets until
53 nf_conntrack_frag6_low_thresh is reached.
55 nf_conntrack_frag6_low_thresh - INTEGER
58 See nf_conntrack_frag6_low_thresh
60 nf_conntrack_frag6_timeout - INTEGER (seconds)
63 Time to keep an IPv6 fragment in memory.
65 nf_conntrack_generic_timeout - INTEGER (seconds)
68 Default for generic timeout. This refers to layer 4 unknown/unsupported
71 nf_conntrack_helper - BOOLEAN
72 - 0 - disabled (default)
75 Enable automatic conntrack helper assignment.
76 If disabled it is required to set up iptables rules to assign
77 helpers to connections. See the CT target description in the
78 iptables-extensions(8) man page for further information.
80 nf_conntrack_icmp_timeout - INTEGER (seconds)
83 Default for ICMP timeout.
85 nf_conntrack_icmpv6_timeout - INTEGER (seconds)
88 Default for ICMP6 timeout.
90 nf_conntrack_log_invalid - INTEGER
91 - 0 - disable (default)
92 - 1 - log ICMP packets
94 - 17 - log UDP packets
95 - 33 - log DCCP packets
96 - 41 - log ICMPv6 packets
97 - 136 - log UDPLITE packets
98 - 255 - log packets of any protocol
100 Log invalid packets of a type specified by value.
102 nf_conntrack_max - INTEGER
103 Size of connection tracking table. Default value is
104 nf_conntrack_buckets value * 4.
106 nf_conntrack_tcp_be_liberal - BOOLEAN
107 - 0 - disabled (default)
110 Be conservative in what you do, be liberal in what you accept from others.
111 If it's non-zero, we mark only out of window RST segments as INVALID.
113 nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN
114 - 0 - disabled (default)
117 If it's 1, we don't mark out of window RST segments as INVALID.
119 nf_conntrack_tcp_loose - BOOLEAN
121 - not 0 - enabled (default)
123 If it is set to zero, we disable picking up already established
126 nf_conntrack_tcp_max_retrans - INTEGER
129 Maximum number of packets that can be retransmitted without
130 received an (acceptable) ACK from the destination. If this number
131 is reached, a shorter timer will be started.
133 nf_conntrack_tcp_timeout_close - INTEGER (seconds)
136 nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
139 nf_conntrack_tcp_timeout_established - INTEGER (seconds)
140 default 432000 (5 days)
142 nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
145 nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
148 nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
151 nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
154 nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
157 nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
160 nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
163 nf_conntrack_timestamp - BOOLEAN
164 - 0 - disabled (default)
167 Enable connection tracking flow timestamping.
169 nf_conntrack_udp_timeout - INTEGER (seconds)
172 nf_conntrack_udp_timeout_stream - INTEGER (seconds)
175 This extended timeout will be used in case there is an UDP stream
178 nf_conntrack_gre_timeout - INTEGER (seconds)
181 nf_conntrack_gre_timeout_stream - INTEGER (seconds)
184 This extended timeout will be used in case there is an GRE stream
187 nf_hooks_lwtunnel - BOOLEAN
188 - 0 - disabled (default)
191 If this option is enabled, the lightweight tunnel netfilter hooks are
192 enabled. This option cannot be disabled once it is enabled.
194 nf_flowtable_tcp_timeout - INTEGER (seconds)
197 Control offload timeout for tcp connections.
198 TCP connections may be offloaded from nf conntrack to nf flow table.
199 Once aged, the connection is returned to nf conntrack with tcp pickup timeout.
201 nf_flowtable_udp_timeout - INTEGER (seconds)
204 Control offload timeout for udp connections.
205 UDP connections may be offloaded from nf conntrack to nf flow table.
206 Once aged, the connection is returned to nf conntrack with udp pickup timeout.