1.. SPDX-License-Identifier: GPL-2.0
2
3===================================
4Netfilter Conntrack Sysfs variables
5===================================
6
7/proc/sys/net/netfilter/nf_conntrack_* Variables:
8=================================================
9
10nf_conntrack_acct - BOOLEAN
11	- 0 - disabled (default)
12	- not 0 - enabled
13
14	Enable connection tracking flow accounting. 64-bit byte and packet
15	counters per flow are added.
16
17nf_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. The hash table will
21	never have fewer than 1024 and never more than 262144 buckets.
22	This sysctl is only writeable in the initial net namespace.
23
24nf_conntrack_checksum - BOOLEAN
25	- 0 - disabled
26	- not 0 - enabled (default)
27
28	Verify checksum of incoming packets. Packets with bad checksums are
29	in INVALID state. If this is enabled, such packets will not be
30	considered for connection tracking.
31
32nf_conntrack_count - INTEGER (read-only)
33	Number of currently allocated flow entries.
34
35nf_conntrack_events - BOOLEAN
36	- 0 - disabled
37	- 1 - enabled
38	- 2 - auto (default)
39
40	If this option is enabled, the connection tracking code will
41	provide userspace with connection tracking events via ctnetlink.
42	The default allocates the extension if a userspace program is
43	listening to ctnetlink events.
44
45nf_conntrack_expect_max - INTEGER
46	Maximum size of expectation table.  Default value is
47	nf_conntrack_buckets / 256. Minimum is 1.
48
49nf_conntrack_frag6_high_thresh - INTEGER
50	default 262144
51
52	Maximum memory used to reassemble IPv6 fragments.  When
53	nf_conntrack_frag6_high_thresh bytes of memory is allocated for this
54	purpose, the fragment handler will toss packets until
55	nf_conntrack_frag6_low_thresh is reached.
56
57nf_conntrack_frag6_low_thresh - INTEGER
58	default 196608
59
60	See nf_conntrack_frag6_low_thresh
61
62nf_conntrack_frag6_timeout - INTEGER (seconds)
63	default 60
64
65	Time to keep an IPv6 fragment in memory.
66
67nf_conntrack_generic_timeout - INTEGER (seconds)
68	default 600
69
70	Default for generic timeout.  This refers to layer 4 unknown/unsupported
71	protocols.
72
73nf_conntrack_helper - BOOLEAN
74	- 0 - disabled (default)
75	- not 0 - enabled
76
77	Enable automatic conntrack helper assignment.
78	If disabled it is required to set up iptables rules to assign
79	helpers to connections.  See the CT target description in the
80	iptables-extensions(8) man page for further information.
81
82nf_conntrack_icmp_timeout - INTEGER (seconds)
83	default 30
84
85	Default for ICMP timeout.
86
87nf_conntrack_icmpv6_timeout - INTEGER (seconds)
88	default 30
89
90	Default for ICMP6 timeout.
91
92nf_conntrack_log_invalid - INTEGER
93	- 0   - disable (default)
94	- 1   - log ICMP packets
95	- 6   - log TCP packets
96	- 17  - log UDP packets
97	- 33  - log DCCP packets
98	- 41  - log ICMPv6 packets
99	- 136 - log UDPLITE packets
100	- 255 - log packets of any protocol
101
102	Log invalid packets of a type specified by value.
103
104nf_conntrack_max - INTEGER
105        Maximum number of allowed connection tracking entries. This value is set
106        to nf_conntrack_buckets by default.
107        Note that connection tracking entries are added to the table twice -- once
108        for the original direction and once for the reply direction (i.e., with
109        the reversed address). This means that with default settings a maxed-out
110        table will have a average hash chain length of 2, not 1.
111
112nf_conntrack_tcp_be_liberal - BOOLEAN
113	- 0 - disabled (default)
114	- not 0 - enabled
115
116	Be conservative in what you do, be liberal in what you accept from others.
117	If it's non-zero, we mark only out of window RST segments as INVALID.
118
119nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN
120	- 0 - disabled (default)
121	- 1 - enabled
122
123	If it's 1, we don't mark out of window RST segments as INVALID.
124
125nf_conntrack_tcp_loose - BOOLEAN
126	- 0 - disabled
127	- not 0 - enabled (default)
128
129	If it is set to zero, we disable picking up already established
130	connections.
131
132nf_conntrack_tcp_max_retrans - INTEGER
133	default 3
134
135	Maximum number of packets that can be retransmitted without
136	received an (acceptable) ACK from the destination. If this number
137	is reached, a shorter timer will be started.
138
139nf_conntrack_tcp_timeout_close - INTEGER (seconds)
140	default 10
141
142nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
143	default 60
144
145nf_conntrack_tcp_timeout_established - INTEGER (seconds)
146	default 432000 (5 days)
147
148nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
149	default 120
150
151nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
152	default 30
153
154nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
155	default 300
156
157nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
158	default 60
159
160nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
161	default 120
162
163nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
164	default 120
165
166nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
167	default 300
168
169nf_conntrack_timestamp - BOOLEAN
170	- 0 - disabled (default)
171	- not 0 - enabled
172
173	Enable connection tracking flow timestamping.
174
175nf_conntrack_udp_timeout - INTEGER (seconds)
176	default 30
177
178nf_conntrack_udp_timeout_stream - INTEGER (seconds)
179	default 120
180
181	This extended timeout will be used in case there is an UDP stream
182	detected.
183
184nf_conntrack_gre_timeout - INTEGER (seconds)
185	default 30
186
187nf_conntrack_gre_timeout_stream - INTEGER (seconds)
188	default 180
189
190	This extended timeout will be used in case there is an GRE stream
191	detected.
192
193nf_hooks_lwtunnel - BOOLEAN
194	- 0 - disabled (default)
195	- not 0 - enabled
196
197	If this option is enabled, the lightweight tunnel netfilter hooks are
198	enabled. This option cannot be disabled once it is enabled.
199
200nf_flowtable_tcp_timeout - INTEGER (seconds)
201        default 30
202
203        Control offload timeout for tcp connections.
204        TCP connections may be offloaded from nf conntrack to nf flow table.
205        Once aged, the connection is returned to nf conntrack with tcp pickup timeout.
206
207nf_flowtable_udp_timeout - INTEGER (seconds)
208        default 30
209
210        Control offload timeout for udp connections.
211        UDP connections may be offloaded from nf conntrack to nf flow table.
212        Once aged, the connection is returned to nf conntrack with udp pickup timeout.
213