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_icmp_timeout - INTEGER (seconds)
74	default 30
75
76	Default for ICMP timeout.
77
78nf_conntrack_icmpv6_timeout - INTEGER (seconds)
79	default 30
80
81	Default for ICMP6 timeout.
82
83nf_conntrack_log_invalid - INTEGER
84	- 0   - disable (default)
85	- 1   - log ICMP packets
86	- 6   - log TCP packets
87	- 17  - log UDP packets
88	- 33  - log DCCP packets
89	- 41  - log ICMPv6 packets
90	- 136 - log UDPLITE packets
91	- 255 - log packets of any protocol
92
93	Log invalid packets of a type specified by value.
94
95nf_conntrack_max - INTEGER
96        Maximum number of allowed connection tracking entries. This value is set
97        to nf_conntrack_buckets by default.
98        Note that connection tracking entries are added to the table twice -- once
99        for the original direction and once for the reply direction (i.e., with
100        the reversed address). This means that with default settings a maxed-out
101        table will have a average hash chain length of 2, not 1.
102
103nf_conntrack_tcp_be_liberal - BOOLEAN
104	- 0 - disabled (default)
105	- not 0 - enabled
106
107	Be conservative in what you do, be liberal in what you accept from others.
108	If it's non-zero, we mark only out of window RST segments as INVALID.
109
110nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN
111	- 0 - disabled (default)
112	- 1 - enabled
113
114	If it's 1, we don't mark out of window RST segments as INVALID.
115
116nf_conntrack_tcp_loose - BOOLEAN
117	- 0 - disabled
118	- not 0 - enabled (default)
119
120	If it is set to zero, we disable picking up already established
121	connections.
122
123nf_conntrack_tcp_max_retrans - INTEGER
124	default 3
125
126	Maximum number of packets that can be retransmitted without
127	received an (acceptable) ACK from the destination. If this number
128	is reached, a shorter timer will be started.
129
130nf_conntrack_tcp_timeout_close - INTEGER (seconds)
131	default 10
132
133nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
134	default 60
135
136nf_conntrack_tcp_timeout_established - INTEGER (seconds)
137	default 432000 (5 days)
138
139nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
140	default 120
141
142nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
143	default 30
144
145nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
146	default 300
147
148nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
149	default 60
150
151nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
152	default 120
153
154nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
155	default 120
156
157nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
158	default 300
159
160nf_conntrack_timestamp - BOOLEAN
161	- 0 - disabled (default)
162	- not 0 - enabled
163
164	Enable connection tracking flow timestamping.
165
166nf_conntrack_udp_timeout - INTEGER (seconds)
167	default 30
168
169nf_conntrack_udp_timeout_stream - INTEGER (seconds)
170	default 120
171
172	This extended timeout will be used in case there is an UDP stream
173	detected.
174
175nf_conntrack_gre_timeout - INTEGER (seconds)
176	default 30
177
178nf_conntrack_gre_timeout_stream - INTEGER (seconds)
179	default 180
180
181	This extended timeout will be used in case there is an GRE stream
182	detected.
183
184nf_hooks_lwtunnel - BOOLEAN
185	- 0 - disabled (default)
186	- not 0 - enabled
187
188	If this option is enabled, the lightweight tunnel netfilter hooks are
189	enabled. This option cannot be disabled once it is enabled.
190
191nf_flowtable_tcp_timeout - INTEGER (seconds)
192        default 30
193
194        Control offload timeout for tcp connections.
195        TCP connections may be offloaded from nf conntrack to nf flow table.
196        Once aged, the connection is returned to nf conntrack with tcp pickup timeout.
197
198nf_flowtable_udp_timeout - INTEGER (seconds)
199        default 30
200
201        Control offload timeout for udp connections.
202        UDP connections may be offloaded from nf conntrack to nf flow table.
203        Once aged, the connection is returned to nf conntrack with udp pickup timeout.
204