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. 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.
24 nf_conntrack_checksum - BOOLEAN
26 - not 0 - enabled (default)
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.
32 nf_conntrack_count - INTEGER (read-only)
33 Number of currently allocated flow entries.
35 nf_conntrack_events - BOOLEAN
37 - not 0 - enabled (default)
39 If this option is enabled, the connection tracking code will
40 provide userspace with connection tracking events via ctnetlink.
42 nf_conntrack_expect_max - INTEGER
43 Maximum size of expectation table. Default value is
44 nf_conntrack_buckets / 256. Minimum is 1.
46 nf_conntrack_frag6_high_thresh - INTEGER
49 Maximum memory used to reassemble IPv6 fragments. When
50 nf_conntrack_frag6_high_thresh bytes of memory is allocated for this
51 purpose, the fragment handler will toss packets until
52 nf_conntrack_frag6_low_thresh is reached.
54 nf_conntrack_frag6_low_thresh - INTEGER
57 See nf_conntrack_frag6_low_thresh
59 nf_conntrack_frag6_timeout - INTEGER (seconds)
62 Time to keep an IPv6 fragment in memory.
64 nf_conntrack_generic_timeout - INTEGER (seconds)
67 Default for generic timeout. This refers to layer 4 unknown/unsupported
70 nf_conntrack_helper - BOOLEAN
71 - 0 - disabled (default)
74 Enable automatic conntrack helper assignment.
75 If disabled it is required to set up iptables rules to assign
76 helpers to connections. See the CT target description in the
77 iptables-extensions(8) man page for further information.
79 nf_conntrack_icmp_timeout - INTEGER (seconds)
82 Default for ICMP timeout.
84 nf_conntrack_icmpv6_timeout - INTEGER (seconds)
87 Default for ICMP6 timeout.
89 nf_conntrack_log_invalid - INTEGER
90 - 0 - disable (default)
91 - 1 - log ICMP packets
93 - 17 - log UDP packets
94 - 33 - log DCCP packets
95 - 41 - log ICMPv6 packets
96 - 136 - log UDPLITE packets
97 - 255 - log packets of any protocol
99 Log invalid packets of a type specified by value.
101 nf_conntrack_max - INTEGER
102 Maximum number of allowed connection tracking entries. This value is set
103 to nf_conntrack_buckets by default.
104 Note that connection tracking entries are added to the table twice -- once
105 for the original direction and once for the reply direction (i.e., with
106 the reversed address). This means that with default settings a maxed-out
107 table will have a average hash chain length of 2, not 1.
109 nf_conntrack_tcp_be_liberal - BOOLEAN
110 - 0 - disabled (default)
113 Be conservative in what you do, be liberal in what you accept from others.
114 If it's non-zero, we mark only out of window RST segments as INVALID.
116 nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN
117 - 0 - disabled (default)
120 If it's 1, we don't mark out of window RST segments as INVALID.
122 nf_conntrack_tcp_loose - BOOLEAN
124 - not 0 - enabled (default)
126 If it is set to zero, we disable picking up already established
129 nf_conntrack_tcp_max_retrans - INTEGER
132 Maximum number of packets that can be retransmitted without
133 received an (acceptable) ACK from the destination. If this number
134 is reached, a shorter timer will be started.
136 nf_conntrack_tcp_timeout_close - INTEGER (seconds)
139 nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
142 nf_conntrack_tcp_timeout_established - INTEGER (seconds)
143 default 432000 (5 days)
145 nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
148 nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
151 nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
154 nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
157 nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
160 nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
163 nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
166 nf_conntrack_timestamp - BOOLEAN
167 - 0 - disabled (default)
170 Enable connection tracking flow timestamping.
172 nf_conntrack_udp_timeout - INTEGER (seconds)
175 nf_conntrack_udp_timeout_stream - INTEGER (seconds)
178 This extended timeout will be used in case there is an UDP stream
181 nf_conntrack_gre_timeout - INTEGER (seconds)
184 nf_conntrack_gre_timeout_stream - INTEGER (seconds)
187 This extended timeout will be used in case there is an GRE stream
190 nf_hooks_lwtunnel - BOOLEAN
191 - 0 - disabled (default)
194 If this option is enabled, the lightweight tunnel netfilter hooks are
195 enabled. This option cannot be disabled once it is enabled.
197 nf_flowtable_tcp_timeout - INTEGER (seconds)
200 Control offload timeout for tcp connections.
201 TCP connections may be offloaded from nf conntrack to nf flow table.
202 Once aged, the connection is returned to nf conntrack with tcp pickup timeout.
204 nf_flowtable_udp_timeout - INTEGER (seconds)
207 Control offload timeout for udp connections.
208 UDP connections may be offloaded from nf conntrack to nf flow table.
209 Once aged, the connection is returned to nf conntrack with udp pickup timeout.