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 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. 24 25nf_conntrack_checksum - BOOLEAN 26 - 0 - disabled 27 - not 0 - enabled (default) 28 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. 32 33nf_conntrack_count - INTEGER (read-only) 34 Number of currently allocated flow entries. 35 36nf_conntrack_events - BOOLEAN 37 - 0 - disabled 38 - not 0 - enabled (default) 39 40 If this option is enabled, the connection tracking code will 41 provide userspace with connection tracking events via ctnetlink. 42 43nf_conntrack_expect_max - INTEGER 44 Maximum size of expectation table. Default value is 45 nf_conntrack_buckets / 256. Minimum is 1. 46 47nf_conntrack_frag6_high_thresh - INTEGER 48 default 262144 49 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. 54 55nf_conntrack_frag6_low_thresh - INTEGER 56 default 196608 57 58 See nf_conntrack_frag6_low_thresh 59 60nf_conntrack_frag6_timeout - INTEGER (seconds) 61 default 60 62 63 Time to keep an IPv6 fragment in memory. 64 65nf_conntrack_generic_timeout - INTEGER (seconds) 66 default 600 67 68 Default for generic timeout. This refers to layer 4 unknown/unsupported 69 protocols. 70 71nf_conntrack_helper - BOOLEAN 72 - 0 - disabled (default) 73 - not 0 - enabled 74 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. 79 80nf_conntrack_icmp_timeout - INTEGER (seconds) 81 default 30 82 83 Default for ICMP timeout. 84 85nf_conntrack_icmpv6_timeout - INTEGER (seconds) 86 default 30 87 88 Default for ICMP6 timeout. 89 90nf_conntrack_log_invalid - INTEGER 91 - 0 - disable (default) 92 - 1 - log ICMP packets 93 - 6 - log TCP 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 99 100 Log invalid packets of a type specified by value. 101 102nf_conntrack_max - INTEGER 103 Size of connection tracking table. Default value is 104 nf_conntrack_buckets value * 4. 105 106nf_conntrack_tcp_be_liberal - BOOLEAN 107 - 0 - disabled (default) 108 - not 0 - enabled 109 110 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. 112 113nf_conntrack_tcp_loose - BOOLEAN 114 - 0 - disabled 115 - not 0 - enabled (default) 116 117 If it is set to zero, we disable picking up already established 118 connections. 119 120nf_conntrack_tcp_max_retrans - INTEGER 121 default 3 122 123 Maximum number of packets that can be retransmitted without 124 received an (acceptable) ACK from the destination. If this number 125 is reached, a shorter timer will be started. 126 127nf_conntrack_tcp_timeout_close - INTEGER (seconds) 128 default 10 129 130nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds) 131 default 60 132 133nf_conntrack_tcp_timeout_established - INTEGER (seconds) 134 default 432000 (5 days) 135 136nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds) 137 default 120 138 139nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds) 140 default 30 141 142nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds) 143 default 300 144 145nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds) 146 default 60 147 148nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds) 149 default 120 150 151nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds) 152 default 120 153 154nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds) 155 default 300 156 157nf_conntrack_timestamp - BOOLEAN 158 - 0 - disabled (default) 159 - not 0 - enabled 160 161 Enable connection tracking flow timestamping. 162 163nf_conntrack_udp_timeout - INTEGER (seconds) 164 default 30 165 166nf_conntrack_udp_timeout_stream - INTEGER (seconds) 167 default 120 168 169 This extended timeout will be used in case there is an UDP stream 170 detected. 171 172nf_conntrack_gre_timeout - INTEGER (seconds) 173 default 30 174 175nf_conntrack_gre_timeout_stream - INTEGER (seconds) 176 default 180 177 178 This extended timeout will be used in case there is an GRE stream 179 detected. 180