1.\" 2.\" This file and its contents are supplied under the terms of the 3.\" Common Development and Distribution License ("CDDL"), version 1.0. 4.\" You may only use this file in accordance with the terms of version 5.\" 1.0 of the CDDL. 6.\" 7.\" A full copy of the text of the CDDL should have accompanied this 8.\" source. A copy of the CDDL is also available via the Internet at 9.\" http://www.illumos.org/license/CDDL. 10.\" 11.\" 12.\" Copyright 2016 Joyent, Inc. 13.\" 14.Dd June 02, 2016 15.Dt MAC_LSO_GET 9F 16.Os 17.Sh NAME 18.Nm mac_lso_get 19.Nd get LSO information on message blocks 20.Sh SYNOPSIS 21.In sys/mac_provider.h 22.Ft void 23.Fo mac_lso_get 24.Fa "mblk_t *mp" 25.Fa "uint32_t *mss" 26.Fa "uint32_t *flags" 27.Fc 28.Sh INTERFACE LEVEL 29illumos DDI specific 30.Sh PARAMETERS 31.Bl -tag -width Fa 32.It Fa mp 33A pointer to a 34.Xr mblk 9S 35structure that contains an outgoing frame. 36.It Fa mss 37A pointer to a value that will be filled in with the maximum segment 38size (MSS). 39.It Fa flags 40A pointer to a value that will be filled in with various flags that 41indicate the behavior to perform. 42.El 43.Sh DESCRIPTION 44The 45.Fn mac_lso_get 46function is used by device drivers that have indicated that they support 47the 48.Sy MAC_CAPAB_LSO 49capability to determine whether large send offload (also known as large 50segmentation offload or LSO) is required for this frame or not. If so, 51the driver should take the appropriate actions to program the hardware 52to perform LSO. 53.Pp 54The 55.Fn mac_lso_get 56function should only be called on the first 57.Sy mblk_t 58that begins a given individual frame in a chain. In other words, it only 59works on entries where it is the first of many possible entries linked 60together by the 61.Sy b_cont 62member. The first 63.Sy mblk_t 64received from any 65.Xr mac 9E 66API or pointed to by a 67.Sy b_next 68pointer should be used. 69.Pp 70A device driver should first look at the 71.Fa flags 72argument to determine what to do. 73.Fa flags 74may be a bitwise inclusive OR of the following: 75.Bl -tag -width Sy 76.It Sy HW_LSO 77This flag indicates that hardware needs to perform segmentation 78offload. The maximum segment size that the driver should use is 79available through the 80.Fa mss 81argument. 82.El 83.Sh CONTEXT 84The 85.Fn mac_lso_get 86function may be called from 87.Sy user , 88.Sy kernel , 89or 90.Sy interrupt 91context. 92.Sh SEE ALSO 93.Xr mac 9E , 94.Xr mblk 9S 95