Netfilter Conntrack Sysfs variables¶
/proc/sys/net/netfilter/nf_conntrack_* Variables:¶
- nf_conntrack_acct - BOOLEAN
- 0 - disabled (default) 
- not 0 - enabled 
 - Enable connection tracking flow accounting. 64-bit byte and packet counters per flow are added. 
- nf_conntrack_buckets - INTEGER
- Size of hash table. If not specified as parameter during module loading, the default size is calculated by dividing total memory by 16384 to determine the number of buckets. The hash table will never have fewer than 1024 and never more than 262144 buckets. This sysctl is only writeable in the initial net namespace. 
- nf_conntrack_checksum - BOOLEAN
- 0 - disabled 
- not 0 - enabled (default) 
 - Verify checksum of incoming packets. Packets with bad checksums are in INVALID state. If this is enabled, such packets will not be considered for connection tracking. 
- nf_conntrack_count - INTEGER (read-only)
- Number of currently allocated flow entries. 
- nf_conntrack_events - BOOLEAN
- 0 - disabled 
- 1 - enabled 
- 2 - auto (default) 
 - If this option is enabled, the connection tracking code will provide userspace with connection tracking events via ctnetlink. The default allocates the extension if a userspace program is listening to ctnetlink events. 
- nf_conntrack_expect_max - INTEGER
- Maximum size of expectation table. Default value is nf_conntrack_buckets / 256. Minimum is 1. 
- nf_conntrack_frag6_high_thresh - INTEGER
- default 262144 - Maximum memory used to reassemble IPv6 fragments. When nf_conntrack_frag6_high_thresh bytes of memory is allocated for this purpose, the fragment handler will toss packets until nf_conntrack_frag6_low_thresh is reached. 
- nf_conntrack_frag6_low_thresh - INTEGER
- default 196608 - See nf_conntrack_frag6_low_thresh 
- nf_conntrack_frag6_timeout - INTEGER (seconds)
- default 60 - Time to keep an IPv6 fragment in memory. 
- nf_conntrack_generic_timeout - INTEGER (seconds)
- default 600 - Default for generic timeout. This refers to layer 4 unknown/unsupported protocols. 
- nf_conntrack_icmp_timeout - INTEGER (seconds)
- default 30 - Default for ICMP timeout. 
- nf_conntrack_icmpv6_timeout - INTEGER (seconds)
- default 30 - Default for ICMP6 timeout. 
- nf_conntrack_log_invalid - INTEGER
- 0 - disable (default) 
- 1 - log ICMP packets 
- 6 - log TCP packets 
- 17 - log UDP packets 
- 33 - log DCCP packets 
- 41 - log ICMPv6 packets 
- 136 - log UDPLITE packets 
- 255 - log packets of any protocol 
 - Log invalid packets of a type specified by value. 
- nf_conntrack_max - INTEGER
- Maximum number of allowed connection tracking entries. This value is set to nf_conntrack_buckets by default. Note that connection tracking entries are added to the table twice -- once for the original direction and once for the reply direction (i.e., with the reversed address). This means that with default settings a maxed-out table will have a average hash chain length of 2, not 1. 
- nf_conntrack_tcp_be_liberal - BOOLEAN
- 0 - disabled (default) 
- not 0 - enabled 
 - Be conservative in what you do, be liberal in what you accept from others. If it’s non-zero, we mark only out of window RST segments as INVALID. 
- nf_conntrack_tcp_ignore_invalid_rst - BOOLEAN
- 0 - disabled (default) 
- 1 - enabled 
 - If it’s 1, we don’t mark out of window RST segments as INVALID. 
- nf_conntrack_tcp_loose - BOOLEAN
- 0 - disabled 
- not 0 - enabled (default) 
 - If it is set to zero, we disable picking up already established connections. 
- nf_conntrack_tcp_max_retrans - INTEGER
- default 3 - Maximum number of packets that can be retransmitted without received an (acceptable) ACK from the destination. If this number is reached, a shorter timer will be started. 
- nf_conntrack_tcp_timeout_close - INTEGER (seconds)
- default 10 
- nf_conntrack_tcp_timeout_close_wait - INTEGER (seconds)
- default 60 
- nf_conntrack_tcp_timeout_established - INTEGER (seconds)
- default 432000 (5 days) 
- nf_conntrack_tcp_timeout_fin_wait - INTEGER (seconds)
- default 120 
- nf_conntrack_tcp_timeout_last_ack - INTEGER (seconds)
- default 30 
- nf_conntrack_tcp_timeout_max_retrans - INTEGER (seconds)
- default 300 
- nf_conntrack_tcp_timeout_syn_recv - INTEGER (seconds)
- default 60 
- nf_conntrack_tcp_timeout_syn_sent - INTEGER (seconds)
- default 120 
- nf_conntrack_tcp_timeout_time_wait - INTEGER (seconds)
- default 120 
- nf_conntrack_tcp_timeout_unacknowledged - INTEGER (seconds)
- default 300 
- nf_conntrack_timestamp - BOOLEAN
- 0 - disabled (default) 
- not 0 - enabled 
 - Enable connection tracking flow timestamping. 
- nf_conntrack_sctp_timeout_closed - INTEGER (seconds)
- default 10 
- nf_conntrack_sctp_timeout_cookie_wait - INTEGER (seconds)
- default 3 
- nf_conntrack_sctp_timeout_cookie_echoed - INTEGER (seconds)
- default 3 
- nf_conntrack_sctp_timeout_established - INTEGER (seconds)
- default 210 - Default is set to (hb_interval * path_max_retrans + rto_max) 
- nf_conntrack_sctp_timeout_shutdown_sent - INTEGER (seconds)
- default 3 
- nf_conntrack_sctp_timeout_shutdown_recd - INTEGER (seconds)
- default 3 
- nf_conntrack_sctp_timeout_shutdown_ack_sent - INTEGER (seconds)
- default 3 
- nf_conntrack_sctp_timeout_heartbeat_sent - INTEGER (seconds)
- default 30 - This timeout is used to setup conntrack entry on secondary paths. Default is set to hb_interval. 
- nf_conntrack_udp_timeout - INTEGER (seconds)
- default 30 
- nf_conntrack_udp_timeout_stream - INTEGER (seconds)
- default 120 - This extended timeout will be used in case there is an UDP stream detected. 
- nf_conntrack_gre_timeout - INTEGER (seconds)
- default 30 
- nf_conntrack_gre_timeout_stream - INTEGER (seconds)
- default 180 - This extended timeout will be used in case there is an GRE stream detected. 
- nf_hooks_lwtunnel - BOOLEAN
- 0 - disabled (default) 
- not 0 - enabled 
 - If this option is enabled, the lightweight tunnel netfilter hooks are enabled. This option cannot be disabled once it is enabled. 
- nf_flowtable_tcp_timeout - INTEGER (seconds)
- default 30 - Control offload timeout for tcp connections. TCP connections may be offloaded from nf conntrack to nf flow table. Once aged, the connection is returned to nf conntrack. 
- nf_flowtable_udp_timeout - INTEGER (seconds)
- default 30 - Control offload timeout for udp connections. UDP connections may be offloaded from nf conntrack to nf flow table. Once aged, the connection is returned to nf conntrack.