When listing a table (see the

When listing a table (see the

.Sx LOOKUP TABLES

.Sx LOOKUP TABLES

section below for more information on lookup tables), format values

section below for more information on lookup tables), format values

.It Fl n

.It Fl n

Only check syntax of the command strings, without actually passing

Only check syntax of the command strings, without actually passing

them to the kernel.

them to the kernel.

.Xr bpf 4

.Xr bpf 4

attached to the

attached to the

.Li ipfw0

.Li ipfw0

.Xr bpf 4

.Xr bpf 4

is attached to the pseudo interface.

is attached to the pseudo interface.

.Pp

.Pp

Processing continues at the next rule.

Processing continues at the next rule.

It is possible to use the 

It is possible to use the 

.Cm tablearg

.Cm tablearg

.It Cm reass

.It Cm reass

Queue and reassemble ip fragments.

Queue and reassemble ip fragments.

If the packet is the last logical fragment, the packet is reassembled and, if

If the packet is the last logical fragment, the packet is reassembled and, if

.Va net.inet.ip.fw.one_pass

.Va net.inet.ip.fw.one_pass

.Pp

.Pp

Fragments handling can be tuned via

Fragments handling can be tuned via

.Va net.inet.ip.maxfragpackets

.Va net.inet.ip.maxfragpackets

and

and

.Va net.inet.ip.maxfragsperpacket

.Va net.inet.ip.maxfragsperpacket

the maximum number of fragments per packet (default: 16).

the maximum number of fragments per packet (default: 16).

.Pp

.Pp

.Nm reass

.Nm reass

rule.

rule.

Alternatively, direction-based (like 

Alternatively, direction-based (like 

.It Cm sockarg

.It Cm sockarg

Matches packets that are associated to a local socket and

Matches packets that are associated to a local socket and

for which the SO_USER_COOKIE socket option has been set

for which the SO_USER_COOKIE socket option has been set

option is made available as

option is made available as

.Cm tablearg

.Cm tablearg

value, which in turn can be used as

value, which in turn can be used as

When used with the

When used with the

.Cm skipto

.Cm skipto

action, the user should be aware that the code will walk the ruleset

action, the user should be aware that the code will walk the ruleset

ruleset compact between the skipto and the target rules. 

ruleset compact between the skipto and the target rules. 

.Sh SETS OF RULES

.Sh SETS OF RULES

Each rule belongs to one of 32 different

Each rule belongs to one of 32 different

for each /24 destination subnet.

for each /24 destination subnet.

.Pp

.Pp

The FLOW_MASK, together with the SCHED_MASK, is used to split

The FLOW_MASK, together with the SCHED_MASK, is used to split

``src-ip 0x000000ff''

``src-ip 0x000000ff''

together with the previous SCHED_MASK makes a flow for

together with the previous SCHED_MASK makes a flow for

subnet will be sent to the same scheduler instance.

subnet will be sent to the same scheduler instance.

.Pp

.Pp

The above diagram holds even for the

The above diagram holds even for the

the use of the channel, MAC level retransmissions and so on.

the use of the channel, MAC level retransmissions and so on.

From our point of view, the channel is effectively unavailable

From our point of view, the channel is effectively unavailable

for this extra time, which is constant or variable depending

for this extra time, which is constant or variable depending

time (e.g. on a wireless link after too many retransmissions).

time (e.g. on a wireless link after too many retransmissions).

We can model the additional delay with an empirical curve

We can model the additional delay with an empirical curve

that represents its distribution.

that represents its distribution.

.It Cm wf2qp

.It Cm wf2qp

implements the WF2Q+ algorithm, which is a Weighted Fair Queueing

implements the WF2Q+ algorithm, which is a Weighted Fair Queueing

algorithm which permits flows to share bandwidth according to

algorithm which permits flows to share bandwidth according to

with a minuscule weight will never starve.

with a minuscule weight will never starve.

WF2Q+ has O(log N) per-packet processing cost, where N is the number

WF2Q+ has O(log N) per-packet processing cost, where N is the number

of flows, and is the default algorithm used by previous versions

of flows, and is the default algorithm used by previous versions

Defines the maximum number of chunks in an SCTP packet that will be parsed for a

Defines the maximum number of chunks in an SCTP packet that will be parsed for a

packet that matches an existing association.

packet that matches an existing association.

This value is enforced to be greater or equal than 

This value is enforced to be greater or equal than 

A high value is

A high value is

a DoS risk yet setting too low a value may result in important control chunks in

a DoS risk yet setting too low a value may result in important control chunks in

the packet not being located and parsed.

the packet not being located and parsed.

As for other similar sysctl variables, larger values pose a DoS risk.

As for other similar sysctl variables, larger values pose a DoS risk.

.It Va net.inet.ip.alias.sctp.log_level: No 0 

.It Va net.inet.ip.alias.sctp.log_level: No 0 

Level of detail in the system log messages (0 \- minimal, 1 \- event,

Level of detail in the system log messages (0 \- minimal, 1 \- event,

option in high loss environments.

option in high loss environments.

.It Va net.inet.ip.alias.sctp.shutdown_time: No 15

.It Va net.inet.ip.alias.sctp.shutdown_time: No 15

Timeout value while waiting for SHUTDOWN-COMPLETE.

Timeout value while waiting for SHUTDOWN-COMPLETE.

.El

.El

.Pp

.Pp

This variable is fully dynamic, the new value will be adopted for all newly

This variable is fully dynamic, the new value will be adopted for all newly

Global tracking will decrease the number of collisions within the 

Global tracking will decrease the number of collisions within the 

.Nm nat 

.Nm nat 

at a cost

at a cost

.Nm nat 

.Nm nat 

state

state

problems in complex networks with multiple 

problems in complex networks with multiple 

We recommend not tracking

We recommend not tracking

global IP addresses, this will still result in a fully functional 

global IP addresses, this will still result in a fully functional 

.Nm nat .

.Nm nat .

traffic shaper supported by Akamba Corp.

traffic shaper supported by Akamba Corp.

.Pp

.Pp

The ipfw core (ipfw2) has been completely redesigned and

The ipfw core (ipfw2) has been completely redesigned and

options have been added by various developer over the years.

options have been added by various developer over the years.

.Pp

.Pp

.An -nosplit

.An -nosplit