illumos: manual page: mac_maxsdu

MAC_MAXSDU_UPDATE(9F) Kernel Functions for Drivers MAC_MAXSDU_UPDATE(9F)

NAME

mac_maxsdu_update - indicate that a device's maximum data size has changed

SYNOPSIS

#include <sys/mac_provider.h>

int
mac_maxsdu_update(mac_handle_t mh, uint_t sdu);

INTERFACE LEVEL

illumos DDI specific

PARAMETERS

mh The MAC handle obtained from a call to mac_register(9F).

sdu An integer representing the maximum size data payload.

DESCRIPTION

The mac_maxsdu_update() function is used to inform the MAC layer that the
device represented by the handle mh has changed the largest size frame that
it can transmit, also known as its Send Data Unit (SDU). This should be
called when the device's MTU has been requested to be changed when a
driver's mc_setprop(9E) entry point has been called with the property
MAC_PROP_MTU or some other device-related event occurring.

The sdu represents the size of the largest payload ignoring the size of its
own headers or any margin. For example, for an Ethernet-based device, this
size should not include the Ethernet header or any VLAN tags.

Through VNICs and other virtual data links, many different devices may be
using a single physical device and have their own MTUs. The system takes
care of those concerns and will not ask a device driver to update the MTU
without verifying this.

RETURN VALUES

Upon successful completion, the mac_maxsdu_update() function returns 0.
Otherwise, a non-negative error is returned.

EXAMPLES

For an example of how a device driver should use the mac_maxsdu_update()
function, see the EXAMPLES section in mc_setprop(9E).

ERRORS

The max_maxsdu_update() function may fail if:

EINVAL The specified sdu is lower than the minimum SDU of the
device.