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
not 0 - enabled (default)
If this option is enabled, the connection tracking code will provide userspace with connection tracking events via ctnetlink.
- 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_helper - BOOLEAN
0 - disabled (default)
not 0 - enabled
Enable automatic conntrack helper assignment. If disabled it is required to set up iptables rules to assign helpers to connections. See the CT target description in the iptables-extensions(8) man page for further information.
- 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_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 with tcp pickup timeout.
- 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 with udp pickup timeout.