src/net/fragment.c

   1 /*
   2  * Copyright (C) 2013 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  *
  19  * You can also choose to distribute this program under the terms of
  20  * the Unmodified Binary Distribution Licence (as given in the file
  21  * COPYING.UBDL), provided that you have satisfied its requirements.
  22  */
  23
  24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  25
  26 #include <stdint.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <ipxe/retry.h>
  30 #include <ipxe/timer.h>
  31 #include <ipxe/ipstat.h>
  32 #include <ipxe/fragment.h>
  33
  34 /** @file
  35  *
  36  * Fragment reassembly
  37  *
  38  */
  39
  40 /**
  41  * Expire fragment reassembly buffer
  42  *
  43  * @v timer             Retry timer
  44  * @v fail              Failure indicator
  45  */
  46 static void fragment_expired ( struct retry_timer *timer, int fail __unused ) {
  47         struct fragment *fragment =
  48                 container_of ( timer, struct fragment, timer );
  49
  50         DBGC ( fragment, "FRAG %p expired\n", fragment );
  51         free_iob ( fragment->iobuf );
  52         list_del ( &fragment->list );
  53         fragment->fragments->stats->reasm_fails++;
  54         free ( fragment );
  55 }
  56
  57 /**
  58  * Find fragment reassembly buffer
  59  *
  60  * @v fragments         Fragment reassembler
  61  * @v iobuf             I/O buffer
  62  * @v hdrlen            Length of non-fragmentable potion of I/O buffer
  63  * @ret fragment        Fragment reassembly buffer, or NULL if not found
  64  */
  65 static struct fragment * fragment_find ( struct fragment_reassembler *fragments,
  66                                          struct io_buffer *iobuf,
  67                                          size_t hdrlen ) {
  68         struct fragment *fragment;
  69
  70         list_for_each_entry ( fragment, &fragments->list, list ) {
  71                 if ( fragments->is_fragment ( fragment, iobuf, hdrlen ) )
  72                         return fragment;
  73         }
  74         return NULL;
  75 }
  76
  77 /**
  78  * Reassemble packet
  79  *
  80  * @v fragments         Fragment reassembler
  81  * @v iobuf             I/O buffer
  82  * @v hdrlen            Length of non-fragmentable potion of I/O buffer
  83  * @ret iobuf           Reassembled packet, or NULL
  84  *
  85  * This function takes ownership of the I/O buffer.  Note that the
  86  * length of the non-fragmentable portion may be modified.
  87  */
  88 struct io_buffer * fragment_reassemble ( struct fragment_reassembler *fragments,
  89                                          struct io_buffer *iobuf,
  90                                          size_t *hdrlen ) {
  91         struct fragment *fragment;
  92         struct io_buffer *new_iobuf;
  93         size_t new_len;
  94         size_t offset;
  95         size_t expected_offset;
  96         int more_frags;
  97
  98         /* Update statistics */
  99         fragments->stats->reasm_reqds++;
 100
 101         /* Find matching fragment reassembly buffer, if any */
 102         fragment = fragment_find ( fragments, iobuf, *hdrlen );
 103
 104         /* Drop out-of-order fragments */
 105         offset = fragments->fragment_offset ( iobuf, *hdrlen );
 106         expected_offset = ( fragment ? ( iob_len ( fragment->iobuf ) -
 107                                          fragment->hdrlen ) : 0 );
 108         if ( offset != expected_offset ) {
 109                 DBGC ( fragment, "FRAG %p dropping out-of-sequence fragment "
 110                        "[%zd,%zd), expected [%zd,...)\n", fragment, offset,
 111                        ( offset + iob_len ( iobuf ) - *hdrlen ),
 112                        expected_offset );
 113                 goto drop;
 114         }
 115
 116         /* Create or extend fragment reassembly buffer as applicable */
 117         if ( ! fragment ) {
 118
 119                 /* Create new fragment reassembly buffer */
 120                 fragment = zalloc ( sizeof ( *fragment ) );
 121                 if ( ! fragment )
 122                         goto drop;
 123                 list_add ( &fragment->list, &fragments->list );
 124                 fragment->iobuf = iobuf;
 125                 fragment->hdrlen = *hdrlen;
 126                 timer_init ( &fragment->timer, fragment_expired, NULL );
 127                 fragment->fragments = fragments;
 128                 DBGC ( fragment, "FRAG %p [0,%zd)\n", fragment,
 129                        ( iob_len ( iobuf ) - *hdrlen ) );
 130
 131         } else {
 132
 133                 /* Check if this is the final fragment */
 134                 more_frags = fragments->more_fragments ( iobuf, *hdrlen );
 135                 DBGC ( fragment, "FRAG %p [%zd,%zd)%s\n", fragment,
 136                        offset, ( offset + iob_len ( iobuf ) - *hdrlen ),
 137                        ( more_frags ? "" : " complete" ) );
 138
 139                 /* Extend fragment reassembly buffer.  Preserve I/O
 140                  * buffer headroom to allow for code which modifies
 141                  * and resends the buffer (e.g. ICMP echo responses).
 142                  */
 143                 iob_pull ( iobuf, *hdrlen );
 144                 new_len = ( iob_headroom ( fragment->iobuf ) +
 145                             iob_len ( fragment->iobuf ) + iob_len ( iobuf ) );
 146                 new_iobuf = alloc_iob ( new_len );
 147                 if ( ! new_iobuf ) {
 148                         DBGC ( fragment, "FRAG %p could not extend reassembly "
 149                                "buffer to %zd bytes\n", fragment, new_len );
 150                         goto drop;
 151                 }
 152                 iob_reserve ( new_iobuf, iob_headroom ( fragment->iobuf ) );
 153                 memcpy ( iob_put ( new_iobuf, iob_len ( fragment->iobuf ) ),
 154                          fragment->iobuf->data, iob_len ( fragment->iobuf ) );
 155                 memcpy ( iob_put ( new_iobuf, iob_len ( iobuf ) ),
 156                          iobuf->data, iob_len ( iobuf ) );
 157                 free_iob ( fragment->iobuf );
 158                 fragment->iobuf = new_iobuf;
 159                 free_iob ( iobuf );
 160
 161                 /* Stop fragment reassembly timer */
 162                 stop_timer ( &fragment->timer );
 163
 164                 /* If this is the final fragment, return it */
 165                 if ( ! more_frags ) {
 166                         iobuf = fragment->iobuf;
 167                         *hdrlen = fragment->hdrlen;
 168                         list_del ( &fragment->list );
 169                         free ( fragment );
 170                         fragments->stats->reasm_oks++;
 171                         return iobuf;
 172                 }
 173         }
 174
 175         /* (Re)start fragment reassembly timer */
 176         start_timer_fixed ( &fragment->timer, FRAGMENT_TIMEOUT );
 177
 178         return NULL;
 179
 180  drop:
 181         fragments->stats->reasm_fails++;
 182         free_iob ( iobuf );
 183         return NULL;
 184 }