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67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
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/*
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* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/**
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* @file
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*
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* Packet buffer padding
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*
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*/
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#include <string.h>
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#include <gpxe/pkbuff.h>
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/**
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* Pad packet buffer
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*
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* @v pkb Packet buffer
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* @v min_len Minimum length
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*
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* This function pads and aligns packet buffers, for devices that
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* aren't capable of padding in hardware, or that require specific
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* alignment in TX buffers. The packet data will end up aligned to a
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* multiple of @c PKB_ALIGN.
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*
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* @c min_len must not exceed @v PKB_ZLEN.
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*/
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void pkb_pad ( struct pk_buff *pkb, size_t min_len ) {
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void *data;
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size_t len;
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size_t headroom;
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signed int pad_len;
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assert ( min_len <= PKB_ZLEN );
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/* Move packet data to start of packet buffer. This will both
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* align the data (since packet buffers are aligned to
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* PKB_ALIGN) and give us sufficient space for the
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* zero-padding
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*/
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data = pkb->data;
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len = pkb_len ( pkb );
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headroom = pkb_headroom ( pkb );
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pkb_push ( pkb, headroom );
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memmove ( pkb->data, data, len );
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pkb_unput ( pkb, headroom );
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/* Pad to minimum packet length */
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pad_len = ( min_len - pkb_len ( pkb ) );
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if ( pad_len > 0 )
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memset ( pkb_put ( pkb, pad_len ), 0, pad_len );
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}
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