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author | Michael Brown | 2013-08-27 17:08:15 +0200 |
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committer | Michael Brown | 2013-08-27 17:39:43 +0200 |
commit | 22a0c4475c91c745f0e5cc1171939359921d09f9 (patch) | |
tree | d5f09c98c2d49a399f504267c18a2dc8dfbb7042 /src/net/fragment.c | |
parent | [linux] Give tap devices a name and bus type (diff) | |
download | ipxe-22a0c4475c91c745f0e5cc1171939359921d09f9.tar.gz ipxe-22a0c4475c91c745f0e5cc1171939359921d09f9.tar.xz ipxe-22a0c4475c91c745f0e5cc1171939359921d09f9.zip |
[ipv4] Generalise fragment reassembly mechanism
Generalise the concept of fragment reassembly to allow for code
sharing between IPv4 and IPv6 protocols.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Diffstat (limited to 'src/net/fragment.c')
-rw-r--r-- | src/net/fragment.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/src/net/fragment.c b/src/net/fragment.c new file mode 100644 index 00000000..3e1dfdf7 --- /dev/null +++ b/src/net/fragment.c @@ -0,0 +1,172 @@ +/* + * 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. + */ + +FILE_LICENCE ( GPL2_OR_LATER ); + +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <ipxe/retry.h> +#include <ipxe/timer.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 ); + 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; + + /* 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 ); + 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 ); + return iobuf; + } + } + + /* (Re)start fragment reassembly timer */ + start_timer_fixed ( &fragment->timer, FRAGMENT_TIMEOUT ); + + return NULL; + + drop: + free_iob ( iobuf ); + return NULL; +} |