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 - not 0 - enabled (default) 38 39 If this option is enabled, the connection tracking code will 40 provide userspace with connection tracking events via ctnetlink. 41 42nf_conntrack_expect_max - INTEGER 43 Maximum size of expectation table. Default value is 44 nf_conntrack_buckets / 256. Minimum is 1. 45 46nf_conntrack_frag6_high_thresh - INTEGER 47 default 262144 48 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. 53 54nf_conntrack_frag6_low_thresh - INTEGER 55 default 196608 56 57 See nf_conntrack_frag6_low_thresh 58 59nf_conntrack_frag6_timeout - INTEGER (seconds) 60 default 60 61 62 Time to keep an IPv6 fragment in memory. 63 64nf_conntrack_generic_timeout - INTEGER (seconds) 65 default 600 66 67 Default for generic timeout. This refers to layer 4 unknown/unsupported 68 protocols. 69 70nf_conntrack_helper - BOOLEAN 71 - 0 - disabled (default) 72 - not 0 - enabled 73 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. 78 79nf_conntrack_icmp_timeout - INTEGER (seconds) 80 default 30 81 82 Default for ICMP timeout. 83 84nf_conntrack_icmpv6_timeout - INTEGER (seconds) 85 default 30 86 87 Default for ICMP6 timeout. 88 89nf_conntrack_log_invalid - INTEGER 90 - 0 - disable (default) 91 - 1 - log ICMP packets 92 - 6 - log TCP 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 98 99 Log invalid packets of a type specified by value. 100 101nf_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. 108 109nf_conntrack_tcp_be_liberal - BOOLEAN 110 - 0 - disabled (default) 111 - not 0 - enabled 112 113 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. 115 116nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN 117 - 0 - disabled (default) 118 - 1 - enabled 119 120 If it's 1, we don't mark out of window RST segments as INVALID. 121 122nf_conntrack_tcp_loose - BOOLEAN 123 - 0 - disabled 124 - not 0 - enabled (default) 125 126 If it is set to zero, we disable picking up already established 127 connections. 128 129nf_conntrack_tcp_max_retrans - INTEGER 130 default 3 131 132 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. 135 136nf_conntrack_tcp_timeout_close - INTEGER (seconds) 137 default 10 138 139nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds) 140 default 60 141 142nf_conntrack_tcp_timeout_established - INTEGER (seconds) 143 default 432000 (5 days) 144 145nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds) 146 default 120 147 148nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds) 149 default 30 150 151nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds) 152 default 300 153 154nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds) 155 default 60 156 157nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds) 158 default 120 159 160nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds) 161 default 120 162 163nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds) 164 default 300 165 166nf_conntrack_timestamp - BOOLEAN 167 - 0 - disabled (default) 168 - not 0 - enabled 169 170 Enable connection tracking flow timestamping. 171 172nf_conntrack_udp_timeout - INTEGER (seconds) 173 default 30 174 175nf_conntrack_udp_timeout_stream - INTEGER (seconds) 176 default 120 177 178 This extended timeout will be used in case there is an UDP stream 179 detected. 180 181nf_conntrack_gre_timeout - INTEGER (seconds) 182 default 30 183 184nf_conntrack_gre_timeout_stream - INTEGER (seconds) 185 default 180 186 187 This extended timeout will be used in case there is an GRE stream 188 detected. 189 190nf_hooks_lwtunnel - BOOLEAN 191 - 0 - disabled (default) 192 - not 0 - enabled 193 194 If this option is enabled, the lightweight tunnel netfilter hooks are 195 enabled. This option cannot be disabled once it is enabled. 196 197nf_flowtable_tcp_timeout - INTEGER (seconds) 198 default 30 199 200 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. 203 204nf_flowtable_udp_timeout - INTEGER (seconds) 205 default 30 206 207 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. 210