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FAITH(4) | Device Drivers Manual | FAITH(4) |
NAME¶
faith
—
IPv6-to-IPv4 TCP relay capturing interface
SYNOPSIS¶
device faith
DESCRIPTION¶
Thefaith
interface captures IPv6 TCP
traffic, for implementing userland IPv6-to-IPv4 TCP relay like
faithd(8).
Each faith
interface is created at runtime
using interface cloning. This is most easily done with the
ifconfig(8)
create
command or using the
cloned_interfaces variable in
rc.conf(5).
Special action will be taken when IPv6 TCP traffic is seen on a router, and the
default routing table suggests to route it to the
faith
interface. In this case, the packet
will be accepted by the router, regardless of the list of IPv6 interface
addresses assigned to the router. The packet will be captured by an IPv6 TCP
socket, if it has the IN6P_FAITH
flag
turned on and matching address/port pairs. As a result,
faith
will let you capture IPv6 TCP traffic
to some specific destination addresses. Userland programs, such as
faithd(8) can use this behavior to relay IPv6 TCP
traffic to IPv4 TCP traffic. The program can accept some specific IPv6 TCP
traffic, perform getsockname(2) to get the IPv6
destination address specified by the client, and perform application-specific
address mapping to relay IPv6 TCP to IPv4 TCP.
The IN6P_FAITH
flag on a IPv6 TCP socket can
be set by using setsockopt(2), with level
IPPROTO_IPV6
and optname
IPv6_FAITH
.
To handle error reports by ICMPv6, some ICMPv6 packets routed to an
faith
interface will be delivered to IPv6
TCP, as well.
To understand how faith
can be used, take a
look at the source code of faithd(8).
As the faith
interface implements potentially
dangerous operations, great care must be taken when configuring it. To avoid
possible misuse, the sysctl(8) variable
net.inet6.ip6.keepfaith
must be set to
1
prior to using the interface. When
net.inet6.ip6.keepfaith
is 0
,
no packets will be captured by the faith
interface.
The faith
interface is intended to be used on
routers, not on hosts.
SEE ALSO¶
inet(4), inet6(4), faithd(8) Jun-ichiro itojun Hagino and Kazu Yamamoto, An IPv6-to-IPv4 transport relay translator, RFC3142.HISTORY¶
The FAITH IPv6-to-IPv4 TCP relay translator first appeared in the WIDE hydrangea IPv6 stack.January 23, 2012 | Debian |