table of contents
|LO(4)||Device Drivers Manual||LO(4)|
lo — software
loopback network interface
loop interface is a software loopback
mechanism which may be used for performance analysis, software testing,
and/or local communication. As with other network interfaces, the loopback
interface must have network addresses assigned for each address family with
which it is to be used. These addresses may be set with the appropriate
ioctl(2) commands for corresponding address families. The
loopback interface should be the last interface configured, as protocols may
use the order of configuration as an indication of priority. The loopback
configured first unless no hardware interfaces exist.
If the transmit checksum offload capability flag is enabled on a loopback interface, checksums will not be generated by IP, UDP, or TCP for packets sent on the interface.
If the receive checksum offload capability flag is enabled on a loopback interface, checksums will not be validated by IP, UDP, or TCP for packets received on the interface.
By default, both receive and transmit checksum flags will be enabled, in order to avoid the overhead of checksumming for local communication where data corruption is unlikely. If transmit checksum generation is disabled, then validation should also be disabled in order to avoid packets being dropped due to invalid checksums.
- lo%d: can't handle af%d.
- The interface was handed a message with addresses formatted in an unsuitable address family; the packet was dropped.
lo device appeared in
4.2BSD. The current checksum generation and
validation avoidance policy appeared in FreeBSD
|January 25, 2012||Debian|