Major revision of the ipfw manpage, trying to make it up-to-date

with ipfw2 extensions and give examples of use of the new features.

This is just a preliminary commit, where i simply added the basic
syntax for the extensions, and clean up the page (e.g. by listing
things in alphabetical rather than random order).
I would appreciate feedback and possible corrections/extensions
by interested parties.

Still missing are a more detailed description of stateful rules
(with keepalives), interaction with of stateful rules and natd (don't do
that!), examples of use with the recently introduced rule sets.

There is an issue related to the MFC: RELENG_4 still has ipfw as a
default, and ipfw2 is optional. We have two options here: MFC this
page as ipfw(8) adding a large number of "SORRY NOT IN IPFW" notes,
or create a new ipfw2(8) manpage just for -stable users.  I am all
for the first approach, but of course am listening to your comments.

1 files changed, 682 insertions, 518 deletions

diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index 5b419ee..1b3832b 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -10,75 +10,97 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl q
-.Oo
-.Fl p Ar preproc
-.Oo Fl D
-.Ar macro Ns Op = Ns Ar value
-.Oc
-.Op Fl U Ar macro
-.Oc
-.Ar pathname
-.Nm
-.Op Fl f | q
-.Cm flush
+.Cm add
+.Ar rule
 .Nm
 .Op Fl q
-.Brq Cm zero | resetlog | delete
+.Cm delete
+.Op Cm set
 .Op Ar number ...
 .Nm
-.Op Fl s Op Ar field
-.Op Fl adeftN
+.Op Fl adeftNS
 .Brq Cm list | show
 .Op Ar number ...
 .Nm
-.Op Fl q
-.Cm add
-.Op Ar number
-.Ar rule-body
+.Op Fl f | q
+.Cm flush
 .Nm
-.Cm pipe
-.Ar number
-.Cm config
-.Ar pipe-config-options
+.Op Fl q
+.Brq Cm zero | resetlog
+.Op Cm set
+.Op Ar number ...
 .Nm
-.Cm pipe
-.Brq Cm delete | list | show
+.Op Fl q
+.Brq Cm disable | enable
+.Cm set
 .Op Ar number ...
 .Nm
-.Cm queue
+.Cm show sets
+.Pp
+.Nm
+.Brq Cm pipe | queue
 .Ar number
 .Cm config
-.Ar queue-config-options
+.Ar config-options
 .Nm
-.Cm queue
+.Op Fl s Op Ar field
+.Brq Cm pipe | queue
 .Brq Cm delete | list | show
 .Op Ar number ...
+.Pp
+.Nm
+.Op Fl q
+.Oo
+.Fl p Ar preproc
+.Oo Fl D
+.Ar macro Ns Op = Ns Ar value
+.Oc
+.Op Fl U Ar macro
+.Oc
+.Ar pathname
 .Sh DESCRIPTION
 The
 .Nm
 utility is the user interface for controlling the
-.Xr ipfirewall 4
-and the
+.Xr ipfw 4
+firewall and the
 .Xr dummynet 4
 traffic shaper in
 .Fx .
 .Pp
-A firewall configuration is made of a list of numbered rules,
-which is scanned for each incoming or outgoing IP packet
-until a match is found and
-the relevant action is performed.
+An
+.Nm
+configuration, or
+.Em ruleset ,
+is made of a list of
+.Em rules
+numbered from 1 to 65535.
+Packets are passed to
+.Nm
+in a number of different places in the protocol stack
+(depending on the source and destination of the packet,
+it is possible that
+.Nm
+is invoked multiple times on the same packet).
+The packet passed to the firewall is compared
+against each of the rules in the firewall
+.Em ruleset .
+When a match is found, the action corresponding to the
+matching rule is performed.
+.Pp
 Depending on the action and certain system settings, packets
-can be reinjected into the firewall at the rule after the
+can be reinjected into the firewall at some rule after the
 matching one for further processing.
-All rules apply to all interfaces, so it is responsibility
-of the system administrator to write the ruleset in such a
-way as to minimize the number of checks.
 .Pp
-A configuration always includes a
-.Em DEFAULT
+An
+.Nm
+ruleset always includes a
+.Em default
 rule (numbered 65535) which cannot be modified,
 and matches all packets.
-The action associated with the default rule can be either
+The action associated with the
+.Em default
+rule can be either
 .Cm deny
 or
 .Cm allow
@@ -97,9 +119,10 @@ the exact parameters (addresses and ports) of the matching packet.
 .Pp
 These dynamic rules, which have a limited lifetime, are checked
 at the first occurrence of a
-.Cm check-state
-or
+.Cm check-state ,
 .Cm keep-state
+or
+.Cm limit
 rule, and are typically used to open the firewall on-demand to
 legitimate traffic only.
 See the
@@ -118,7 +141,7 @@ commands.
 .Pp
 Rules can be added with the
 .Cm add
-command; deleted individually with the
+command; deleted individually or in groups with the
 .Cm delete
 command, and globally with the
 .Cm flush
@@ -153,6 +176,8 @@ if misused,
 .No i.e. Cm flush .
 .Em Note ,
 if there is no tty associated with the process, this is implied.
+.It Fl N
+Try to resolve addresses and service names in output.
 .It Fl q
 While
 .Cm add Ns ing ,
@@ -176,18 +201,19 @@ If a
 .Cm flush
 is performed in normal (verbose) mode (with the default kernel
 configuration), it prints a message.
-Because all rules are flushed, the message cannot be delivered
-to the login session.
-This causes the remote login session to be closed and the
-remainder of the ruleset is not processed.
-Access to the console is required to recover.
-.It Fl t
-While listing, show last match timestamp.
-.It Fl N
-Try to resolve addresses and service names in output.
+Because all rules are flushed, the message might not be delivered
+to the login session, causing the remote login session to be closed
+and the remainder of the ruleset is not processed.
+Access to the console would then be required to recover.
+.It Fl S
+While listing rules, show the set each rule belongs to.
+If this flag is not specified, disabled rules will not be
+listed.
 .It Fl s Op Ar field
 While listing pipes, sort according to one of the four
 counters (total and current packets or bytes).
+.It Fl t
+While listing, show last match timestamp.
 .El
 .Pp
 To ease configuration, rules can be put into a file which is
@@ -197,8 +223,7 @@ as shown in the first synopsis line.
 An absolute
 .Ar pathname
 must be used.
-The file
-will be read line by line and applied as arguments to the
+The file will be read line by line and applied as arguments to the
 .Nm
 utility.
 .Pp
@@ -236,61 +261,160 @@ frequently required arguments like IP addresses.
 The
 .Nm
 .Cm pipe
+and
+.Cm queue
 commands are used to configure the traffic shaper, as shown in the
 .Sx TRAFFIC SHAPER CONFIGURATION
 section below.
+.Sh PACKET FLOW
+.Nm
+can be invoked from multiple places in the protocol stack,
+under control of several system parameters,
+and it is important to understand when this occurs in order to
+design a proper ruleset. The places where
+.Nm
+is invoked are listed below, together with the sysctl variables
+which control its invocation.
+.Bd -literal -offset indent
+      ^	    to upper layers   V
+      |                       |
+      +----------->-----------+
+      ^                       V
+ [ip_input]              [ip_output]   net.inet.ip.fw.enable=1
+      |                       |
+      ^                       V
+[ether_demux]    [ether_output_frame]  net.link.ether.ipfw=1
+      |                       |
+      +-->--[bdg_forward]-->--+        net.link.ether.bridge_ipfw=1
+      ^                       V
+      |      to devices       |
+.Ed
+.Pp
+As can be noted from the above picture, the number of
+times the same packet goes through the firewall can
+vary between 0 and 4 depending o packet source and
+destination, and system configuration.
+In each of these places, the packet is passed to
+.Nm
+with all (and only) the fields that belong to that level.
+That is, incoming packets will include the MAC header when
+.Nm
+is invoked from
+.Cm ether_demux() ,
+but the same packets will have the MAC header stripped off when
+.Nm
+is invoked from
+.Cm ip_input() .
+.br
+The complete ruleset is always used,
+irrespective of the place where
+.Nm
+is invoked, or the source of the packet.
+If a rule contains some match patterns or actions which are not valid
+for the place of invokation (e.g. trying
+to match a MAC header when
+.Nm
+is called from
+.Cm ip_input()
+) the rule will simply not match. It is thus responsibility of
+the programmer, if necessary, to write a suitable ruleset to
+differentiate among the possible places.
+.Cm skipto
+rules can be useful here, as an example:
+.Bd -literal -offset indent
+# packets from ether_demux or bdg_forward
+ipfw add 10 skipto 1000 all from any to any layer2 in
+# packets from ip_input
+ipfw add 10 skipto 2000 all from any to any not layer2 in
+# packets from ip_output
+ipfw add 10 skipto 3000 all from any to any not layer2 out
+# packets from ether_output_frame
+ipfw add 10 skipto 4000 all from any to any layer2 out
+.Ed
+.Pp
+(yes, at the moment there is no way to differentiate between
+ether_demux and bdg_forward).
 .Sh RULE FORMAT
-The
+The format of
 .Nm
-rule format is the following:
-.Bd -ragged
+rules is the following:
+.Bd -ragged -offset indent
+.Op Ar rule_number
+.Op Cm set Ar set_number
 .Op Cm prob Ar match_probability
-.Ar action
+.br
+.Ar "   " action
 .Op Cm log Op Cm logamount Ar number
-.Ar proto
-.Cm from Ar src
-.Cm to Ar dst
-.Op Ar interface-spec
-.Op Ar options
+.Ar body
 .Ed
 .Pp
-Each packet can be filtered based on the following information that is
-associated with it:
+where the body of the rule specifies which information is used
+for filtering packets, among the following:
 .Pp
-.Bl -tag -width "Source and destination IP address" -offset indent -compact
-.It Protocol
-(TCP, UDP, ICMP, etc.)
-.It Source and destination IP address
-(possibly masked)
-.It Source and destination port
-(lists, ranges or masks)
+.Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
+.It Layer-2 header fields
+When available
+.It IPv4 Protocol
+TCP, UDP, ICMP, etc.
+.It Source and dest. addresses and ports
 .It Direction
-(incoming or outgoing)
+See Section
+.Sx PACKET FLOW
 .It Transmit and receive interface
-(by name or address)
-.It IP version
-.It IP type of service
-.It IP datagram length
-.It IP identification
-.It IP fragment flag
-(non-zero IP offset)
-.It IP time to live
+By name or address
+.It Misc. IP header fields
+Version, type of service, datagram length, identification,
+fragment flag (non-zero IP offset),
+Time To Live
 .It IP options
-.It TCP sequence number
-.It TCP acknowledgment number
-.It TCP flags
-(SYN, FIN, ACK, RST, etc.)
-.It TCP window
+.It Misc. TCP header fields
+TCP flags (SYN, FIN, ACK, RST, etc.),
+sequence number, acknowledgment number,
+window
 .It TCP options
 .It ICMP types
-(for ICMP packets)
-.It User/group ID of the socket associated with the packet
+for ICMP packets
+.It User/group ID
+When the packet can be associate to a local socket.
 .El
 .Pp
-Note that it may be dangerous to filter on the source IP
-address or source TCP/UDP port because either or both could
-easily be spoofed.
+Note that some of the above information, e.g. source MAC or IP addresses and
+TCP/UDP ports, could easily be spoofed, so filtering on those fields
+alone might not guarantee the desired results.
 .Bl -tag -width indent
+.It Ar rule_number
+Each rule is associated with a
+.Ar rule_number
+in the range 1..65535, with the latter reserved for the
+.Em default
+rule.
+Rules are checked sequentially by rule number.
+Multiple rules can have the same number, in which case they are
+checked (and listed) according to the order in which they have
+been added.
+If a rule is entered without specifying a number, the kernel will
+assign one in such a way that the rule becomes the last one
+before the
+.Em default
+rule.
+Automatic rule numbers are assigned by incrementing the last
+non-default rule number by the value of the sysctl variable
+.Ar net.inet.ip.fw.autoinc_step
+which defaults to 100.
+If this is not possible (e.g. because we would go beyond the
+maximum allowed rule number), the same number of the last
+non-default value is used instead.
+.It Ar set_number
+Each rule is associated to a
+.Ar set_number
+in the range 0..31, with the latter reserved for the
+.Em default
+rule.
+Sets can be individually disabled and enabled, so this parameter
+is of fundamental importance for atomic ruleset manipulation.
+It can be also used to simplify deletion of groups of rules.
+If a rule is entered without specifying a set number,
+set 0 will be used.
 .It Cm prob Ar match_probability
 A match is only declared with the specified probability
 (floating point number between 0 and 1).
@@ -300,116 +424,110 @@ random packet drop or
 .Xr dummynet 4 )
 to simulate the effect of multiple paths leading to out-of-order
 packet delivery.
-.It Ar action :
+.It Cm log Op Cm logamount Ar number
+When a packet matches a rule with the
+.Cm log
+keyword, a message will be
+logged to
+.Xr syslogd 8
+with a
+.Dv LOG_SECURITY
+facility.
+The logging only occurs if the sysctl variable
+.Em net.inet.ip.fw.verbose
+is set to 1
+(which is the default when the kernel is compiled with
+.Dv IPFIREWALL_VERBOSE
+) and the number of packets logged so far for that
+particular rule does not exceed ther
+.Cm logamount
+parameter.
+If no
+.Cm logamount
+is specified, the limit is taken from the sysctl variable
+.Em net.inet.ip.fw.verbose_limit .
+In both cases, a value of 0
+removes the logging limit.
+.Pp
+Once the limit is reached, logging can be re-enabled by
+clearing the logging counter
+or the packet counter for that entry, see the
+.Cm resetlog
+command.
+.Pp
+.El
+.Ss RULE ACTIONS
+A rule can be associated with one of the following actions, which
+will be executed when the packet matches the body of the rule.
 .Bl -tag -width indent
-.It Cm allow
+.It Cm allow | accept | pass | permit
 Allow packets that match rule.
 The search terminates.
-Aliases are
-.Cm pass ,
-.Cm permit
-and
-.Cm accept .
-.It Cm deny
-Discard packets that match this rule.
-The search terminates.
-.Cm drop
-is an alias for
-.Cm deny .
-.It Cm reject
-(Deprecated).
-Discard packets that match this rule, and try to send an ICMP
-host unreachable notice.
-The search terminates.
-.It Cm unreach Ar code
-Discard packets that match this rule, and try to send an ICMP
-unreachable notice with code
-.Ar code ,
-where
-.Ar code
-is a number from 0 to 255, or one of these aliases:
-.Cm net , host , protocol , port ,
-.Cm needfrag , srcfail , net-unknown , host-unknown ,
-.Cm isolated , net-prohib , host-prohib , tosnet ,
-.Cm toshost , filter-prohib , host-precedence
-or
-.Cm precedence-cutoff .
-The search terminates.
-.It Cm reset
-TCP packets only.
-Discard packets that match this rule, and try to send a TCP
-reset (RST) notice.
-The search terminates.
-.It Cm count
-Update counters for all packets that match rule.
-The search continues with the next rule.
 .It Cm check-state
 Checks the packet against the dynamic ruleset.
-If a match is found then the search terminates, otherwise
-we move to the next rule.
+If a match is found, execute the action associated with
+the rule which generated this dynamic rule, otherwise
+move to the next rule.
+.br
+.Cm Check-state
+rules do not have a body.
 If no
 .Cm check-state
 rule is found, the dynamic ruleset is checked at the first
 .Cm keep-state
+or
+.Cm limit
 rule.
+.It Cm count
+Update counters for all packets that match rule.
+The search continues with the next rule.
+.It Cm deny | drop
+Discard packets that match this rule.
+The search terminates.
 .It Cm divert Ar port
 Divert packets that match this rule to the
 .Xr divert 4
 socket bound to port
 .Ar port .
 The search terminates.
-.It Cm tee Ar port
-Send a copy of packets matching this rule to the
-.Xr divert 4
-socket bound to port
-.Ar port .
-The search terminates and the original packet is accepted
-(but see section
-.Sx BUGS
-below).
-.It Cm fwd Ar ipaddr Ns Op , Ns Ar port
+.It Cm fwd | forward Ar ipaddr Ns Op , Ns Ar port
 Change the next-hop on matching packets to
 .Ar ipaddr ,
 which can be an IP address in dotted quad or a host name.
+The search terminates if this rule matches.
+.Pp
 If
 .Ar ipaddr
-is not a directly-reachable address, the route as found in
-the local routing table for that IP is used instead.
+is a local address, then matching packets will be forwarded to
+.Ar port
+(or the port number in the packet if one is not specified in the rule)
+on the local machine.
+.br
 If
 .Ar ipaddr
-is a local address, then on a packet matching a
+is not a local address, then the port number
+(if specified) is ignored, and the packet will be
+forwarded to the remote address, using the route as found in
+the local routing table for that IP.
+.br
+A
+.Ar fwd
+rule will not match layer-2 packets (those received
+on ether_input, ether_output, or bridged).
+.br
+The
 .Cm fwd
-rule,
-it will be diverted to
-.Ar port
-on the local machine, keeping the local address of the socket
-set to the original IP address the packet was destined for.
+action does not change the contents of the packet at all.
+In particular, the destination address remains unmodified, so
+packets forwarded to another system will usually be rejected by that system
+unless there is a matching rule on that system to capture them.
+For packets forwarded locally,
+the local address of the socket will be
+set to the original destination address of the packet.
 This makes the 
 .Xr netstat 1
 entry look rather weird but is intended for
 use with transparent proxy servers.
-If the IP is not a local address then the port number
-(if specified) is ignored.
-This will also map addresses when packets are
-generated locally.
-The search terminates if this rule matches.
-If the port number is not given then the port number in the
-packet is used, so that a packet for an external machine port
-Y would be forwarded to local port Y.
-The kernel must have been compiled with the
-.Dv IPFIREWALL_FORWARD
-option.
-Bridging interferes with forwarding of packets not destined
-to the local system as they bypass
-.Fn ip_input
-and
-.Fn ip_output
-where forwarding is implemented.
-The
-.Cm fwd
-action does not change the contents of the packet at all so
-packets forwarded to another system will usually be rejected by that system
-unless there is a matching rule on that system to capture them.
 .It Cm pipe Ar pipe_nr
 Pass packet to a
 .Xr dummynet 4
@@ -430,53 +548,93 @@ Pass packet to a
 .Xr dummynet 4
 .Dq queue
 (for bandwidth limitation using WF2Q).
+.It Cm reject
+(Deprecated).
+Synonym for
+.Cm unreach host .
+.It Cm reset
+Discard packets that match this rule, and if the
+packet is a TCP packet, try to send a TCP reset (RST) notice.
+The search terminates.
 .It Cm skipto Ar number
 Skip all subsequent rules numbered less than
 .Ar number .
 The search continues with the first rule numbered
 .Ar number
 or higher.
+.It Cm tee Ar port
+Send a copy of packets matching this rule to the
+.Xr divert 4
+socket bound to port
+.Ar port .
+The search terminates and the original packet is accepted
+(but see section
+.Sx BUGS
+below).
+.It Cm unreach Ar code
+Discard packets that match this rule, and try to send an ICMP
+unreachable notice with code
+.Ar code ,
+where
+.Ar code
+is a number from 0 to 255, or one of these aliases:
+.Cm net , host , protocol , port ,
+.Cm needfrag , srcfail , net-unknown , host-unknown ,
+.Cm isolated , net-prohib , host-prohib , tosnet ,
+.Cm toshost , filter-prohib , host-precedence
+or
+.Cm precedence-cutoff .
+The search terminates.
 .El
-.It Cm log Op Cm logamount Ar number
-If the kernel was compiled with
-.Dv IPFIREWALL_VERBOSE ,
-then when a packet matches a rule with the
-.Cm log
-keyword a message will be
-logged to
-.Xr syslogd 8
-with a
-.Dv LOG_SECURITY
-facility.
-.Em Note :
-by default, they are appended to the
-.Pa /var/log/security
-file (see
-.Xr syslog.conf 5 ) .
-If the kernel was compiled with the
-.Dv IPFIREWALL_VERBOSE_LIMIT
-option, then by default logging will cease after the number
-of packets specified by the option are received for that
-particular chain entry, and
-.Em net.inet.ip.fw.verbose_limit
-will be set to that number.
-However, if
-.Cm logamount Ar number
-is used, that
-.Ar number
-will be the logging limit rather than
-.Em net.inet.ip.fw.verbose_limit ,
-where the value
-.Dq 0
-removes the logging limit.
-Logging may then be re-enabled by clearing the logging counter
-or the packet counter for that entry.
+.Ss RULE BODY
+The body of a rule contains zero or more patterns (such as
+specific source and destination addresses or ports,
+protocol options, incoming or outgoing interfaces, etc.)
+that the packet must match in order to be recognised.
+In general, the patterns are connected by (implicit)
+.Em and
+connectives -- i.e. all must match in order for the
+rule to match.
+Individual patterns can be prefixed by the
+.Em not
+keyword to reverse the result of the match, as in
+.Pp
+.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
+.Pp
+Additionally, sets of alternative match patterns (
+.Em or-blocks
+) can be constructed by putting the patterns in
+lists enclosed between parentheses ( ) or braces { }, and
+using
+.Cm or
+connectives as follows:
+.Pp
+.Dl "ipfw add 100 allow ip from { x or not y or z } to any"
+.Pp
+Only one level of parentheses is allowed.
+Beware that most shells have special meanings for parentheses
+or braces, so it is advisable to put a \\ in front of them.
+.Pp
+The body of a rule must in general comprise a source and destination
+addres specifier.
+The keyword
+.Ar any
+can be used in various places to specify that the content of
+a required field is irrelevant.
+.Pp
+The general rule body format is one of the following:
+.Bd -ragged -offset indent
+.Ar proto
+.Cm from Ar src
+.Cm to Ar dst
+.Op Ar options
+.br
+.Cm MAC Ar dst-mac src-mac mac-type
+.Op Ar options
+.Ed
 .Pp
-Console logging and the log limit are adjustable dynamically
-through the
-.Xr sysctl 8
-interface in the MIB base of
-.Em net.inet.ip.fw .
+where fields have the following meaning:
+.Bl -tag -width indent
 .It Ar proto
 An IP protocol specified by number or name (for a complete
 list see
@@ -487,66 +645,88 @@ or
 .Cm all
 keywords mean any protocol will match.
 .It Ar src No and Ar dst :
-.Cm any | me | Op Cm not
-.Aq Ar address Ns / Ns Ar mask
-.Op Ar ports
-.Pp
-Specifying
-.Cm any
-makes the rule match any IP address.
-.Pp
-Specifying
-.Cm me
-makes the rule match any IP address configured on an interface in the system.
-.Pp
+A single
+.Ar ip address
+, or an
+.Em or-block
+containing one or more of them,
+optionally followed by
+.Em port numbers.
+followed by a set of port numbers.
+.It Ar ip address :
+An address (or set of addresses) specified in one of the following
+ways, optionally preceded by a
+.Cm not
+operator:
+.Bl -tag -width indent
+.It Cm any
+matches any IP address.
+.It Cm me
+matches any IP address configured on an interface in the system.
+The address list is evaluated at the time the packet is
+analysed.
+.It Ar numeric-ip | hostname
+Matches a single IPv4 address, specified as dotted-quad or a hostname.
+Hostnames are resolved at the time the rule is added to the firewall list.
+.It Ar addr Ns / Ns Ar masklen
+Matches all addresses with base
+.Ar addr
+(specified as a dotted quad or a hostname)
+and mask width of
+.Cm masklen
+bits.
+As an example, 1.2.3.4/25 will match
+all IP numbers from 1.2.3.0 to 1.2.3.127 .
+.It Ar addr Ns / Ns Ar masklen Ns Cm { Ns Ar num,num,... Ns Cm }
+Matches all addresses with base address
+.Ar addr
+(specified as a dotted quad or a hostname)
+and whose last byte is in the list between braces { } .
+Note that there must be no spaces between braces, commas and
+numbers.
 The
-.Aq Ar address Ns / Ns Ar mask
-may be specified as:
-.Bl -tag -width "ipno/bits"
-.It Ar ipno
-An IP number of the form 1.2.3.4.
-Only this exact IP number will match the rule.
-.It Ar ipno Ns / Ns Ar bits
-An IP number with a mask width of the form 1.2.3.4/24.
-In this case all IP numbers from 1.2.3.0 to 1.2.3.255 will match.
-.It Ar ipno Ns : Ns Ar mask
-An IP number with a mask of the form 1.2.3.4:255.255.240.0.
-In this case all IP numbers from 1.2.0.0 to 1.2.15.255 will match.
+.Ar masklen
+field is used to limit the size of the set of addresses,
+and can have any value between 24 and 32.
+.br
+As an example, an address specified as 1.2.3.4/24{128,35,55,89}
+will match the following IP addresses:
+.br
+1.2.3.128 1.2.3.35 1.2.3.55 1.2.3.89 .
+.br
+This format is particularly useful to handle sparse address sets
+within a single rule. Because the matching occurs using a
+bitmask, it takes constant time and dramatically reduces
+the complexity of rulesets.
 .El
-.Pp
-The sense of the match can be inverted by preceding an address with the
+.It Cm port numbers
+With protocols which support port numbers (such as TCP and UDP), optional
+.Cm ports
+may be specified as one or more ports or port ranges, separated
+by commas but no spaces, and an optional
 .Cm not
-modifier, causing all other addresses to be matched instead.
-This does not affect the selection of port numbers.
-.Pp
-With the TCP and UDP protocols, optional
-.Em ports
-may be specified as:
+operator:
 .Bd -ragged -offset indent
-.Sm off
-.Brq Ar port | port No \&- Ar port | port : mask
-.Op , Ar port Op , Ar ...
-.Sm on
+.Op Cm not
+.Brq Ar port | port Ns \&- Ns Ar port Ns
+.Op , Ns Ar ...
 .Ed
 .Pp
 The
 .Ql \&-
 notation specifies a range of ports (including boundaries).
 .Pp
-The
-.Ql \&:
-notation specifies a port and a mask, a match is declared if
-the port number in the packet matches the one in the rule,
-limited to the bits which are set in the mask.
-.Pp
 Service names (from
 .Pa /etc/services )
 may be used instead of numeric port values.
-A range may only be specified as the first value, and the
-length of the port list is limited to
-.Dv IP_FW_MAX_PORTS
-ports (as defined in
-.Pa /usr/src/sys/netinet/ip_fw.h ) .
+The length of the port list is limited to 14 ports or ranges,
+though you can also use port ranges within an
+.Em or-block
+to build essentially unlimited lists:
+.Pp
+.Dl "ipfw add allow tcp from any { 1-20,30-50 or 500-600 } to any"
+.Pp
+.Pp
 A backslash
 .Pq Ql \e
 can be used to escape the dash
@@ -561,30 +741,178 @@ specifications.
 See the
 .Cm frag
 option for details on matching fragmented packets.
-.It Ar interface-spec
-Some combinations of the following specifiers are allowed:
-.Bl -tag -width "via ipno"
-.It Cm in
-Only match incoming packets.
-.It Cm out
-Only match outgoing packets.
-.It Cm via Ar ifX
-Packet must be going through interface
-.Ar ifX .
-.It Cm via Ar if Ns Cm *
-Packet must be going through interface
-.Ar ifX ,
-where
-.Ar X
-is any unit number.
-.It Cm via any
-Packet must be going through
-.Em some
-interface.
-.It Cm via Ar ipno
-Packet must be going through the interface having IP address
-.Ar ipno .
 .El
+.Ss RULE OPTIONS
+Additional match patterns can be used within
+rules. Zero or more of these so-called
+.Em options
+can be present in a rule, optionally prefixed by the
+.Cm not
+operand, and possibly grouped into
+.Em or-blocks .
+.Pp
+Note that there is an ambiguity in the syntax: in a rule of
+the form
+.Pp
+.Dl "ipfw add allow ip from any to any { in or layer2 }"
+.Pp
+the or-block could contain either port lists or options.
+To remove the ambiguity, one should specify a destination
+port, which can be done by either using the keyword
+.Cm any
+or an empty or-block
+.Cm { }
+e.g.:
+.Pp
+.Dl "ipfw add allow ip from any to any any { in or layer2 }"
+.Pp
+The following options are available:
+.Bl -tag -width indent
+.It Cm bridged
+Matches only bridged packets.
+.It Cm established
+TCP packets only.
+Match packets that have the RST or ACK bits set.
+.It Cm frag
+Match if the packet is a fragment and this is not the first
+fragment of the datagram.
+.Cm frag
+may not be used in conjunction with either
+.Cm tcpflags
+or TCP/UDP port specifications.
+.It Cm gid Ar group
+Match all TCP or UDP packets sent by or received for a
+.Ar group .
+A
+.Ar group
+may be matched by name or identification number.
+.It Cm icmptypes Ar types
+ICMP packets only.
+Match if the ICMP type is in the list
+.Ar types .
+The list may be specified as any combination of ranges or
+individual types separated by commas.
+The supported ICMP types are:
+.Pp
+echo reply
+.Pq Cm 0 ,
+destination unreachable
+.Pq Cm 3 ,
+source quench
+.Pq Cm 4 ,
+redirect
+.Pq Cm 5 ,
+echo request
+.Pq Cm 8 ,
+router advertisement
+.Pq Cm 9 ,
+router solicitation
+.Pq Cm 10 ,
+time-to-live exceeded
+.Pq Cm 11 ,
+IP header bad
+.Pq Cm 12 ,
+timestamp request
+.Pq Cm 13 ,
+timestamp reply
+.Pq Cm 14 ,
+information request
+.Pq Cm 15 ,
+information reply
+.Pq Cm 16 ,
+address mask request
+.Pq Cm 17
+and address mask reply
+.Pq Cm 18 .
+.It Cm in | out
+Only match incoming or outgoing packets, respectively.
+.Cm in
+and
+.Cm out
+are mutually exclusive (in fact,
+.Cm out
+is implemented as
+.Cm not in
+).
+.It Cm ipid Ar id
+Match if the identification of IP datagram is
+.Ar id .
+.It Cm iplen Ar len
+Match if the total length of a packet, including header and data, is
+.Ar len
+bytes.
+.It Cm ipoptions Ar spec
+Match if the IP header contains the comma separated list of
+options specified in
+.Ar spec .
+The supported IP options are:
+.Pp
+.Cm ssrr
+(strict source route),
+.Cm lsrr
+(loose source route),
+.Cm rr
+(record packet route) and
+.Cm ts
+(timestamp).
+The absence of a particular option may be denoted
+with a
+.Ql \&! .
+.It Cm ipprecedence Ar precedence
+Match if the numeric value of IP datagram's precedence is equal to
+.Ar precedence .
+.It Cm iptos Ar spec
+Match if the IP header contains the comma separated list of
+service types specified in
+.Ar spec .
+The supported IP types of service are:
+.Pp
+.Cm lowdelay
+.Pq Dv IPTOS_LOWDELAY ,
+.Cm throughput
+.Pq Dv IPTOS_THROUGHPUT ,
+.Cm reliability
+.Pq Dv IPTOS_RELIABILITY ,
+.Cm mincost
+.Pq Dv IPTOS_MINCOST ,
+.Cm congestion
+.Pq Dv IPTOS_CE .
+The absence of a particular type may be denoted
+with a
+.Ql \&! .
+.It Cm ipttl Ar ttl
+Match if the time to live of IP datagram is
+.Ar ttl .
+.It Cm ipversion Ar ver
+Match if the IP header version is
+.Ar ver .
+.It Cm keep-state
+Upon a match, the firewall will create a dynamic rule, whose
+default behaviour is to matching bidirectional traffic between
+source and destination IP/port using the same protocol.
+The rule has a limited lifetime (controlled by a set of
+.Xr sysctl 8
+variables), and the lifetime is refreshed every time a matching
+packet is found.
+.It Cm layer2
+Matches only layer2 packets, i.e. those passed to
+.Nm
+from ether_demux() and ether_output_frame().
+.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
+The firewall will only allow
+.Ar N
+connections with the same
+set of parameters as specified in the rule.
+One or more
+of source and destination addresses and ports can be
+specified.
+.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any
+Packet must be received, transmitted or be going through,
+respectively, the interface specified by exact name (
+.Ar ifX
+), by device name (
+.Ar if Ns Cm *
+), by IP address, or through some interface.
 .Pp
 The
 .Cm via
@@ -600,7 +928,7 @@ is checked.
 By specifying both, it is possible to match packets based on
 both receive and transmit interface, e.g.:
 .Pp
-.Dl "ipfw add 100 deny ip from any to any out recv ed0 xmit ed1"
+.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
 .Pp
 The
 .Cm recv
@@ -615,111 +943,16 @@ is required (and
 is invalid) whenever
 .Cm xmit
 is used.
-Specifying
-.Cm via
-together with
-.Cm xmit
-or
-.Cm recv
-is invalid.
 .Pp
 A packet may not have a receive or transmit interface: packets
 originating from the local host have no receive interface,
 while packets destined for the local host have no transmit
 interface.
-.It Ar options :
-.Bl -tag -width indent
-.It Cm keep-state
-Upon a match, the firewall will create a dynamic rule, whose
-default behaviour is to matching bidirectional traffic between
-source and destination IP/port using the same protocol.
-The rule has a limited lifetime (controlled by a set of
-.Xr sysctl 8
-variables), and the lifetime is refreshed every time a matching
-packet is found.
-.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
-The firewall will only allow
-.Ar N
-connections with the same
-set of parameters as specified in the rule.
-One or more
-of source and destination addresses and ports can be
-specified.
-.It Cm bridged
-Matches only bridged packets.
-This can be useful for multicast or broadcast traffic, which
-would otherwise pass through the firewall twice: once during
-bridging, and a second time when the packet is delivered to
-the local stack.
-.Pp
-Apart from a small performance penalty, this would be a problem
-when using
-.Em pipes
-because the same packet would be accounted for twice in terms
-of bandwidth, queue occupation, and also counters.
-.It Cm ipversion Ar ver
-Match if the IP header version is
-.Ar ver .
-.It Cm ipprecedence Ar precedence
-Match if the numeric value of IP datagram's precedence is equal to
-.Ar precedence .
-.It Cm iptos Ar spec
-Match if the IP header contains the comma separated list of
-service types specified in
-.Ar spec .
-The supported IP types of service are:
-.Pp
-.Cm lowdelay
-.Pq Dv IPTOS_LOWDELAY ,
-.Cm throughput
-.Pq Dv IPTOS_THROUGHPUT ,
-.Cm reliability
-.Pq Dv IPTOS_RELIABILITY ,
-.Cm mincost
-.Pq Dv IPTOS_MINCOST ,
-.Cm congestion
-.Pq Dv IPTOS_CE .
-The absence of a particular type may be denoted
-with a
-.Ql \&! .
-.It Cm iplen Ar len
-Match if the total length of a packet, including header and data, is
-.Ar len
-bytes.
-.It Cm ipid Ar id
-Match if the identification of IP datagram is
-.Ar id .
-.It Cm frag
-Match if the packet is a fragment and this is not the first
-fragment of the datagram.
-.Cm frag
-may not be used in conjunction with either
-.Cm tcpflags
-or TCP/UDP port specifications.
-.It Cm ipttl Ar ttl
-Match if the time to live of IP datagram is
-.Ar ttl .
-.It Cm ipoptions Ar spec
-Match if the IP header contains the comma separated list of
-options specified in
-.Ar spec .
-The supported IP options are:
-.Pp
-.Cm ssrr
-(strict source route),
-.Cm lsrr
-(loose source route),
-.Cm rr
-(record packet route) and
-.Cm ts
-(timestamp).
-The absence of a particular option may be denoted
-with a
-.Ql \&! .
-.It Cm tcpseq Ar seq
+.It Cm setup
 TCP packets only.
-Match if the TCP header sequence number field is set to
-.Ar seq .
+Match packets that have the SYN bit set but no ACK bit.
+This is the short form of
+.Dq Li tcpflags\ syn,!ack .
 .It Cm tcpack Ar ack
 TCP packets only.
 Match if the TCP header acknowledgment number field is set to
@@ -748,14 +981,10 @@ a non-zero offset.
 See the
 .Cm frag
 option for details on matching fragmented packets.
-.It Cm established
-TCP packets only.
-Match packets that have the RST or ACK bits set.
-.It Cm setup
+.It Cm tcpseq Ar seq
 TCP packets only.
-Match packets that have the SYN bit set but no ACK bit.
-This is the short form of
-.Dq Li tcpflags\ syn,!ack .
+Match if the TCP header sequence number field is set to
+.Ar seq .
 .It Cm tcpwin Ar win
 TCP packets only.
 Match if the TCP header window field is set to
@@ -780,58 +1009,15 @@ The supported TCP options are:
 The absence of a particular option may be denoted
 with a
 .Ql \&! .
-.It Cm icmptypes Ar types
-ICMP packets only.
-Match if the ICMP type is in the list
-.Ar types .
-The list may be specified as any combination of ranges or
-individual types separated by commas.
-The supported ICMP types are:
-.Pp
-echo reply
-.Pq Cm 0 ,
-destination unreachable
-.Pq Cm 3 ,
-source quench
-.Pq Cm 4 ,
-redirect
-.Pq Cm 5 ,
-echo request
-.Pq Cm 8 ,
-router advertisement
-.Pq Cm 9 ,
-router solicitation
-.Pq Cm 10 ,
-time-to-live exceeded
-.Pq Cm 11 ,
-IP header bad
-.Pq Cm 12 ,
-timestamp request
-.Pq Cm 13 ,
-timestamp reply
-.Pq Cm 14 ,
-information request
-.Pq Cm 15 ,
-information reply
-.Pq Cm 16 ,
-address mask request
-.Pq Cm 17
-and address mask reply
-.Pq Cm 18 .
 .It Cm uid Ar user
 Match all TCP or UDP packets sent by or received for a
 .Ar user .
 A
 .Ar user
 may be matched by name or identification number.
-.It Cm gid Ar group
-Match all TCP or UDP packets sent by or received for a
-.Ar group .
-A
-.Ar group
-may be matched by name or identification number.
-.El
 .El
+.Sh STATEFUL FIREWALL
+To be completed.
 .Sh TRAFFIC SHAPER CONFIGURATION
 The
 .Nm
@@ -864,49 +1050,20 @@ rate fixed by the pipe according to the WF2Q+ policy.
 The
 .Nm
 pipe configuration format is the following:
-.Bd -ragged
-.Cm pipe Ar number Cm config
-.Op Cm bw Ar bandwidth | device
-.Op Cm delay Ar ms-delay
-.Oo
-.Cm queue
-.Brq Ar slots | size
-.Oc
-.Op Cm plr Ar loss-probability
-.Op Cm mask Ar mask-specifier
-.Op Cm buckets Ar hash-table-size
-.Oo
-.Cm red | gred
-.Sm off
-.Ar w_q No / Ar min_th No / Ar max_th No / Ar max_p
-.Sm on
-.Oc
+.Bd -ragged -offset indent
+.Cm pipe Ar number Cm config Ar pipe-configuration
 .Ed
 .Pp
 The
 .Nm
 queue configuration format is the following:
-.Bd -ragged
-.Cm queue Ar number Cm config
-.Op Cm pipe Ar pipe_nr
-.Op Cm weight Ar weight
-.Oo
-.Cm queue
-.Brq Ar slots | size
-.Oc
-.Op Cm plr Ar loss-probability
-.Op Cm mask Ar mask-specifier
-.Op Cm buckets Ar hash-table-size
-.Oo
-.Cm red | gred
-.Sm off
-.Ar w_q No / Ar min_th No / Ar max_th No / Ar max_p
-.Sm on
-.Oc
+.Bd -ragged -offset indent
+.Cm queue Ar number Cm config Ar queue-configuration
 .Ed
 .Pp
 The following parameters can be configured for a pipe:
-.Bl -tag -width indent
+.Pp
+.Bl -tag -width indent -compact
 .It Cm bw Ar bandwidth | device
 Bandwidth, measured in
 .Sm off
@@ -917,7 +1074,7 @@ Bandwidth, measured in
 A value of 0 (default) means unlimited bandwidth.
 The unit must follow immediately the number, as in
 .Pp
-.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
+.Dl "ipfw pipe 1 config bw 300Kbit/s"
 .Pp
 If a device name is specified instead of a numeric
 value, then the transmit clock is supplied by the specified
@@ -927,6 +1084,7 @@ At the moment only the
 device supports this
 functionality, for use in conjunction with
 .Xr ppp 8 .
+.Pp
 .It Cm delay Ar ms-delay
 Propagation delay, measured in milliseconds.
 The value is rounded to the next multiple of the clock tick
@@ -936,6 +1094,36 @@ with
 to reduce
 the granularity to 1ms or less).
 Default value is 0, meaning no delay.
+.El
+.Pp
+The following parameters can be configured for a queue:
+.Pp
+.Bl -tag -width indent -compact
+.It Cm pipe Ar pipe_nr
+Connects a queue to the specified pipe.
+Multiple queues (usually
+with different weights) can be connected to the same pipe, which
+specifies the aggregate rate for the set of queues.
+.Pp
+.It Cm weight Ar weight
+Specifies the weight to be used for flows matching this queue.
+The weight must be in the range 1..100, and defaults to 1.
+.El
+.Pp
+Finally, the following parameters can be configured for both
+pipes and queues:
+.Pp
+.Bl -tag -width indent -compact
+.Pp
+.It Cm buckets Ar hash-table-size
+Specifies the size of the hash table used for storing the
+various queues.
+Default value is 64 controlled by the
+.Xr sysctl 8
+variable
+.Em net.inet.ip.dummynet.hash_size ,
+allowed range is 16 to 1024.
+.Pp
 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
 Queue size, in
 .Ar slots
@@ -951,13 +1139,7 @@ or 20s of queue on a 30Kbit/s pipe.
 Even worse effect can result if you get packets from an
 interface with a much larger MTU, e.g. the loopback interface
 with its 16KB packets.
-.It Cm plr Ar packet-loss-rate
-Packet loss rate.
-Argument
-.Ar packet-loss-rate
-is a floating-point number between 0 and 1, with 0 meaning no
-loss, 1 meaning 100% loss.
-The loss rate is internally represented on 31 bits.
+.Pp
 .It Cm mask Ar mask-specifier
 The
 .Xr dummynet 4
@@ -984,22 +1166,15 @@ When used within a
 configuration, each flow is assigned a weight equal to the
 weight of the queue, and all flows insisting on the same pipe
 share bandwidth proportionally to their weight.
-.It Cm buckets Ar hash-table-size
-Specifies the size of the hash table used for storing the
-various queues.
-Default value is 64 controlled by the
-.Xr sysctl 8
-variable
-.Em net.inet.ip.dummynet.hash_size ,
-allowed range is 16 to 1024.
-.It Cm pipe Ar pipe_nr
-Connects a queue to the specified pipe.
-Multiple queues (usually
-with different weights) can be connected to the same pipe, which
-specifies the aggregate rate for the set of queues.
-.It Cm weight Ar weight
-Specifies the weight to be used for flows matching this queue.
-The weight must be in the range 1..100, and defaults to 1.
+.Pp
+.It Cm plr Ar packet-loss-rate
+Packet loss rate.
+Argument
+.Ar packet-loss-rate
+is a floating-point number between 0 and 1, with 0 meaning no
+loss, 1 meaning 100% loss.
+The loss rate is internally represented on 31 bits.
+.Pp
 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
 Make use of the RED (Random Early Detection) queue management algorithm.
 .Ar w_q
@@ -1159,6 +1334,14 @@ rules.
 Upon the initial SYN exchange the lifetime is kept short,
 then increased after both SYN have been seen, then decreased
 again during the final FIN exchange or when a RST
+.It Em net.link.ether.ipfw : No 0
+Controls whether layer-2 packets are passed to
+.Nm .
+Default is no.
+.It Em net.link.ether.bridge_ipfw : No 0
+Controls whether bridged packets are passed to
+.Nm .
+Default is no.
 .El
 .Sh EXAMPLES
 This command adds an entry which denies all tcp packets from
@@ -1342,22 +1525,6 @@ on a net with per-host limits, rather than per-network limits:
 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
-.Sh IMPLEMENTATION NOTES
-The number of times a packet is processed by
-.Nm
-varies \(em basically,
-.Nm
-is invoked every time the kernel functions
-.Fn ip_input ,
-.Fn ip_output
-and
-.Fn bdg_forward
-are invoked.
-This means that packets are processed once for connections having
-only one endpoint on the local host, twice for connections with
-both endpoints on the local host, or for packet routed by the host
-(acting as a gateway), and once for packets bridged by the host
-(acting as a bridge).
 .Sh SEE ALSO
 .Xr cpp 1 ,
 .Xr m4 1 ,
@@ -1402,22 +1569,19 @@ both endpoints on the local host, or for packet routed by the host
 .Sh BUGS
 The syntax has grown over the years and it is not very clean.
 .Pp
-.Em WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!
-.Pp
-This program can put your computer in rather unusable state.
-When using it for the first time, work on the console of the
-computer, and do
-.Em NOT
-do anything you don't understand.
+.Em WARNING
 .Pp
-When manipulating/adding chain entries, service and protocol names
-are not accepted.
+Misconfiguring the firewall can put your computer in an unusable state,
+possibly shutting down network services and requiring console access to
+regain control to it.
 .Pp
 Incoming packet fragments diverted by
 .Cm divert
 or
 .Cm tee
 are reassembled before delivery to the socket.
+The action used on those packet is the one from the
+rule which matches the first fragment of the packet.
 .Pp
 Packets that match a
 .Cm tee