text: /*
   * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation; either version 2 of the
   * License, or any later version.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   * 02110-1301, USA.
   *
   * You can also choose to distribute this program under the terms of
   * the Unmodified Binary Distribution Licence (as given in the file
   * COPYING.UBDL), provided that you have satisfied its requirements.
   */
  
  FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  
  #include <stdint.h>
  #include <stdlib.h>
  #include <string.h>
  #include <ipxe/retry.h>
  #include <ipxe/timer.h>
  #include <ipxe/ipstat.h>
  #include <ipxe/fragment.h>
  
  /** @file
   *
   * Fragment reassembly
   *
   */
  
  /**
   * Expire fragment reassembly buffer
   *
   * @v timer		Retry timer
   * @v fail		Failure indicator
   */
  static void fragment_expired ( struct retry_timer *timer, int fail __unused ) {
  	struct fragment *fragment =
  		container_of ( timer, struct fragment, timer );
  
  	DBGC ( fragment, "FRAG %p expired\n", fragment );
  	free_iob ( fragment->iobuf );
  	list_del ( &fragment->list );
  	fragment->fragments->stats->reasm_fails++;
  	free ( fragment );
  }
  
  /**
   * Find fragment reassembly buffer
   *
   * @v fragments		Fragment reassembler
   * @v iobuf		I/O buffer
   * @v hdrlen		Length of non-fragmentable potion of I/O buffer
   * @ret fragment	Fragment reassembly buffer, or NULL if not found
   */
  static struct fragment * fragment_find ( struct fragment_reassembler *fragments,
  					 struct io_buffer *iobuf,
  					 size_t hdrlen ) {
  	struct fragment *fragment;
  
  	list_for_each_entry ( fragment, &fragments->list, list ) {
  		if ( fragments->is_fragment ( fragment, iobuf, hdrlen ) )
  			return fragment;
  	}
  	return NULL;
  }
  
  /**
   * Reassemble packet
   *
   * @v fragments		Fragment reassembler
   * @v iobuf		I/O buffer
   * @v hdrlen		Length of non-fragmentable potion of I/O buffer
   * @ret iobuf		Reassembled packet, or NULL
   *
   * This function takes ownership of the I/O buffer.  Note that the
   * length of the non-fragmentable portion may be modified.
   */
  struct io_buffer * fragment_reassemble ( struct fragment_reassembler *fragments,
  					 struct io_buffer *iobuf,
  					 size_t *hdrlen ) {
  	struct fragment *fragment;
  	struct io_buffer *new_iobuf;
  	size_t new_len;
  	size_t offset;
  	size_t expected_offset;
  	int more_frags;
  
  	/* Update statistics */
  	fragments->stats->reasm_reqds++;
  
  	/* Find matching fragment reassembly buffer, if any */
  	fragment = fragment_find ( fragments, iobuf, *hdrlen );
  
  	/* Drop out-of-order fragments */
  	offset = fragments->fragment_offset ( iobuf, *hdrlen );
  	expected_offset = ( fragment ? ( iob_len ( fragment->iobuf ) -
  					 fragment->hdrlen ) : 0 );
  	if ( offset != expected_offset ) {
  		DBGC ( fragment, "FRAG %p dropping out-of-sequence fragment "
  		       "[%zd,%zd), expected [%zd,...)\n", fragment, offset,
  		       ( offset + iob_len ( iobuf ) - *hdrlen ),
  		       expected_offset );
  		goto drop;
  	}
  
  	/* Create or extend fragment reassembly buffer as applicable */
  	if ( ! fragment ) {
  
  		/* Create new fragment reassembly buffer */
  		fragment = zalloc ( sizeof ( *fragment ) );
  		if ( ! fragment )
  			goto drop;
  		list_add ( &fragment->list, &fragments->list );
  		fragment->iobuf = iobuf;
  		fragment->hdrlen = *hdrlen;
  		timer_init ( &fragment->timer, fragment_expired, NULL );
  		fragment->fragments = fragments;
  		DBGC ( fragment, "FRAG %p [0,%zd)\n", fragment,
  		       ( iob_len ( iobuf ) - *hdrlen ) );
  
  	} else {
  
  		/* Check if this is the final fragment */
  		more_frags = fragments->more_fragments ( iobuf, *hdrlen );
  		DBGC ( fragment, "FRAG %p [%zd,%zd)%s\n", fragment,
  		       offset, ( offset + iob_len ( iobuf ) - *hdrlen ),
  		       ( more_frags ? "" : " complete" ) );
  
  		/* Extend fragment reassembly buffer.  Preserve I/O
  		 * buffer headroom to allow for code which modifies
  		 * and resends the buffer (e.g. ICMP echo responses).
  		 */
  		iob_pull ( iobuf, *hdrlen );
  		new_len = ( iob_headroom ( fragment->iobuf ) +
  			    iob_len ( fragment->iobuf ) + iob_len ( iobuf ) );
  		new_iobuf = alloc_iob ( new_len );
  		if ( ! new_iobuf ) {
  			DBGC ( fragment, "FRAG %p could not extend reassembly "
  			       "buffer to %zd bytes\n", fragment, new_len );
  			goto drop;
  		}
  		iob_reserve ( new_iobuf, iob_headroom ( fragment->iobuf ) );
  		memcpy ( iob_put ( new_iobuf, iob_len ( fragment->iobuf ) ),
  			 fragment->iobuf->data, iob_len ( fragment->iobuf ) );
  		memcpy ( iob_put ( new_iobuf, iob_len ( iobuf ) ),
  			 iobuf->data, iob_len ( iobuf ) );
  		free_iob ( fragment->iobuf );
  		fragment->iobuf = new_iobuf;
  		free_iob ( iobuf );
  
  		/* Stop fragment reassembly timer */
  		stop_timer ( &fragment->timer );
  
  		/* If this is the final fragment, return it */
  		if ( ! more_frags ) {
  			iobuf = fragment->iobuf;
  			*hdrlen = fragment->hdrlen;
  			list_del ( &fragment->list );
  			free ( fragment );
  			fragments->stats->reasm_oks++;
  			return iobuf;
  		}
  	}
  
  	/* (Re)start fragment reassembly timer */
  	start_timer_fixed ( &fragment->timer, FRAGMENT_TIMEOUT );
  
  	return NULL;
  
   drop:
  	fragments->stats->reasm_fails++;
  	free_iob ( iobuf );
  	return NULL;
  }
  