$FreeBSD: releng/11.0/share/man/man4/ipfirewall.4 242079 2012-10-25 09:39:14Z ae $
NAMEipfw - IP packet filter and traffic accounting
SYNOPSISTo compile the driver into the kernel, place the following option in the kernel configuration file:
Other related kernel options which may also be useful are:
options IPFIREWALL_DEFAULT_TO_ACCEPT options IPFIREWALL_VERBOSE options IPFIREWALL_VERBOSE_LIMIT=100
To load the driver as a module at boot time, add the following line into the loader.conf5 file:
DESCRIPTIONThe sysctl Cm net.inet.tcp.syncookies system facility allows filtering, redirecting, and other operations on IP packets travelling through network interfaces.
The default behavior of sysctl Cm net.inet.tcp.syncookies is to block all incoming and outgoing traffic. This behavior can be modified, to allow all traffic through the sysctl Cm net.inet.tcp.syncookies firewall by default, by enabling the IPFIREWALL_DEFAULT_TO_ACCEPT kernel option. This option may be useful when configuring sysctl Cm net.inet.tcp.syncookies for the first time. If the default sysctl Cm net.inet.tcp.syncookies behavior is to allow everything, it is easier to cope with firewall-tuning mistakes which may accidentally block all traffic.
To enable logging of packets passing through , enable the IPFIREWALL_VERBOSE kernel option. The IPFIREWALL_VERBOSE_LIMIT option will prevent syslogd(8) from flooding system logs or causing local Denial of Service. This option may be set to the number of packets which will be logged on a per-entry basis before the entry is rate-limited.
The user interface for sysctl Cm net.inet.tcp.syncookies is implemented by the ipfw(8) utility, so please refer to the ipfw(8) manpage for a complete description of the sysctl Cm net.inet.tcp.syncookies capabilities and how to use it.