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download PDF document: ipfw.4.pdf

IPFW(4) FreeBSD Kernel Interfaces Manual IPFW(4)
NAME ipfw - IP packet filter and traffic accounting
SYNOPSIS To compile the driver into the kernel, place the following option in the kernel configuration file:
options IPFIREWALL
Other related kernel options which may also be useful are:
options IPFIREWALL_DEFAULT_TO_ACCEPT options IPDIVERT options IPFIREWALL_NAT options IPFIREWALL_NAT64 options IPFIREWALL_NPTV6 options IPFIREWALL_PMOD options IPFIREWALL_VERBOSE options IPFIREWALL_VERBOSE_LIMIT=100 options LIBALIAS
To load the driver as a module at boot time, add the following line into the loader.conf(5) file:
ipfw_load="YES"
DESCRIPTION The ipfw system facility allows filtering, redirecting, and other operations on IP packets travelling through network interfaces.
The default behavior of ipfw is to block all incoming and outgoing traffic. This behavior can be modified, to allow all traffic through the ipfw firewall by default, by enabling the IPFIREWALL_DEFAULT_TO_ACCEPT kernel option. This option may be useful when configuring ipfw for the first time. If the default ipfw behavior is to allow everything, it is easier to cope with firewall-tuning mistakes which may accidentally block all traffic.
When using natd(8) in conjunction with ipfw as NAT facility, the kernel option IPDIVERT enables diverting packets to natd(8) for translation.
When using the in-kernel NAT facility of ipfw, the kernel option IPFIREWALL_NAT enables basic libalias(3) functionality in the kernel.
When using any of the IPv4 to IPv6 transition mechanisms in ipfw, the kernel option IPFIREWALL_NAT64 enables all of these NAT64 methods in the kernel.
When using the IPv6 network prefix translation facility of ipfw, the kernel option IPFIREWALL_NPTV6 enables this functionality in the kernel.
When using the packet modification facility of ipfw, the kernel option IPFIREWALL_PMOD enables this functionality in the kernel.
To enable logging of packets passing through ipfw, enable the IPFIREWALL_VERBOSE kernel option. The IPFIREWALL_VERBOSE_LIMIT option will prevent syslogd(8) from flooding system logs or causing local Denial accomplished with the IPFIREWALL_NAT kernel option.
The user interface for ipfw is implemented by the ipfw(8) utility, so please refer to the ipfw(8) man page for a complete description of the ipfw capabilities and how to use it.
SEE ALSO setsockopt(2), divert(4), ip(4), ip6(4), ipfw(8), libalias(3), natd(8), sysctl(8), syslogd(8), pfil(9)
FreeBSD 14.0-RELEASE-p11 August 19, 2020 FreeBSD 14.0-RELEASE-p11