2 * net/tipc/msg.h: Include file for TIPC message header routines
4 * Copyright (c) 2000-2007, Ericsson AB
5 * Copyright (c) 2005-2007, Wind River Systems
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the names of the copyright holders nor the names of its
17 * contributors may be used to endorse or promote products derived from
18 * this software without specific prior written permission.
20 * Alternatively, this software may be distributed under the terms of the
21 * GNU General Public License ("GPL") version 2 as published by the Free
22 * Software Foundation.
24 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
25 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
28 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
29 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
30 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34 * POSSIBILITY OF SUCH DAMAGE.
42 #define TIPC_VERSION 2
43 #define DATA_LOW TIPC_LOW_IMPORTANCE
44 #define DATA_MEDIUM TIPC_MEDIUM_IMPORTANCE
45 #define DATA_HIGH TIPC_HIGH_IMPORTANCE
46 #define DATA_CRITICAL TIPC_CRITICAL_IMPORTANCE
47 #define SHORT_H_SIZE 24 /* Connected,in cluster */
48 #define DIR_MSG_H_SIZE 32 /* Directly addressed messages */
49 #define CONN_MSG_H_SIZE 36 /* Routed connected msgs*/
50 #define LONG_H_SIZE 40 /* Named Messages */
51 #define MCAST_H_SIZE 44 /* Multicast messages */
52 #define MAX_H_SIZE 60 /* Inclusive full options */
53 #define MAX_MSG_SIZE (MAX_H_SIZE + TIPC_MAX_USER_MSG_SIZE)
54 #define LINK_CONFIG 13
58 TIPC user data message header format, version 2
60 - Fundamental definitions available to privileged TIPC users
61 are located in tipc_msg.h.
62 - Remaining definitions available to TIPC internal users appear below.
66 static inline void msg_set_word(struct tipc_msg
*m
, u32 w
, u32 val
)
68 m
->hdr
[w
] = htonl(val
);
71 static inline void msg_set_bits(struct tipc_msg
*m
, u32 w
,
72 u32 pos
, u32 mask
, u32 val
)
74 val
= (val
& mask
) << pos
;
75 m
->hdr
[w
] &= ~htonl(mask
<< pos
);
76 m
->hdr
[w
] |= htonl(val
);
83 static inline u32
msg_version(struct tipc_msg
*m
)
85 return msg_bits(m
, 0, 29, 7);
88 static inline void msg_set_version(struct tipc_msg
*m
)
90 msg_set_bits(m
, 0, 29, 0xf, TIPC_VERSION
);
93 static inline u32
msg_user(struct tipc_msg
*m
)
95 return msg_bits(m
, 0, 25, 0xf);
98 static inline u32
msg_isdata(struct tipc_msg
*m
)
100 return (msg_user(m
) <= DATA_CRITICAL
);
103 static inline void msg_set_user(struct tipc_msg
*m
, u32 n
)
105 msg_set_bits(m
, 0, 25, 0xf, n
);
108 static inline void msg_set_importance(struct tipc_msg
*m
, u32 i
)
113 static inline void msg_set_hdr_sz(struct tipc_msg
*m
,u32 n
)
115 msg_set_bits(m
, 0, 21, 0xf, n
>>2);
118 static inline int msg_non_seq(struct tipc_msg
*m
)
120 return msg_bits(m
, 0, 20, 1);
123 static inline void msg_set_non_seq(struct tipc_msg
*m
)
125 msg_set_bits(m
, 0, 20, 1, 1);
128 static inline int msg_dest_droppable(struct tipc_msg
*m
)
130 return msg_bits(m
, 0, 19, 1);
133 static inline void msg_set_dest_droppable(struct tipc_msg
*m
, u32 d
)
135 msg_set_bits(m
, 0, 19, 1, d
);
138 static inline int msg_src_droppable(struct tipc_msg
*m
)
140 return msg_bits(m
, 0, 18, 1);
143 static inline void msg_set_src_droppable(struct tipc_msg
*m
, u32 d
)
145 msg_set_bits(m
, 0, 18, 1, d
);
148 static inline void msg_set_size(struct tipc_msg
*m
, u32 sz
)
150 m
->hdr
[0] = htonl((msg_word(m
, 0) & ~0x1ffff) | sz
);
158 static inline void msg_set_type(struct tipc_msg
*m
, u32 n
)
160 msg_set_bits(m
, 1, 29, 0x7, n
);
163 static inline void msg_set_errcode(struct tipc_msg
*m
, u32 err
)
165 msg_set_bits(m
, 1, 25, 0xf, err
);
168 static inline u32
msg_reroute_cnt(struct tipc_msg
*m
)
170 return msg_bits(m
, 1, 21, 0xf);
173 static inline void msg_incr_reroute_cnt(struct tipc_msg
*m
)
175 msg_set_bits(m
, 1, 21, 0xf, msg_reroute_cnt(m
) + 1);
178 static inline void msg_reset_reroute_cnt(struct tipc_msg
*m
)
180 msg_set_bits(m
, 1, 21, 0xf, 0);
183 static inline u32
msg_lookup_scope(struct tipc_msg
*m
)
185 return msg_bits(m
, 1, 19, 0x3);
188 static inline void msg_set_lookup_scope(struct tipc_msg
*m
, u32 n
)
190 msg_set_bits(m
, 1, 19, 0x3, n
);
193 static inline void msg_set_options(struct tipc_msg
*m
, const char *opt
, u32 sz
)
195 u32 hsz
= msg_hdr_sz(m
);
196 char *to
= (char *)&m
->hdr
[hsz
/4];
198 if ((hsz
< DIR_MSG_H_SIZE
) || ((hsz
+ sz
) > MAX_H_SIZE
))
200 msg_set_bits(m
, 1, 16, 0x7, (hsz
- 28)/4);
201 msg_set_hdr_sz(m
, hsz
+ sz
);
205 static inline u32
msg_bcast_ack(struct tipc_msg
*m
)
207 return msg_bits(m
, 1, 0, 0xffff);
210 static inline void msg_set_bcast_ack(struct tipc_msg
*m
, u32 n
)
212 msg_set_bits(m
, 1, 0, 0xffff, n
);
220 static inline u32
msg_ack(struct tipc_msg
*m
)
222 return msg_bits(m
, 2, 16, 0xffff);
225 static inline void msg_set_ack(struct tipc_msg
*m
, u32 n
)
227 msg_set_bits(m
, 2, 16, 0xffff, n
);
230 static inline u32
msg_seqno(struct tipc_msg
*m
)
232 return msg_bits(m
, 2, 0, 0xffff);
235 static inline void msg_set_seqno(struct tipc_msg
*m
, u32 n
)
237 msg_set_bits(m
, 2, 0, 0xffff, n
);
246 static inline void msg_set_prevnode(struct tipc_msg
*m
, u32 a
)
248 msg_set_word(m
, 3, a
);
251 static inline void msg_set_origport(struct tipc_msg
*m
, u32 p
)
253 msg_set_word(m
, 4, p
);
256 static inline void msg_set_destport(struct tipc_msg
*m
, u32 p
)
258 msg_set_word(m
, 5, p
);
261 static inline void msg_set_mc_netid(struct tipc_msg
*m
, u32 p
)
263 msg_set_word(m
, 5, p
);
266 static inline void msg_set_orignode(struct tipc_msg
*m
, u32 a
)
268 msg_set_word(m
, 6, a
);
271 static inline void msg_set_destnode(struct tipc_msg
*m
, u32 a
)
273 msg_set_word(m
, 7, a
);
276 static inline int msg_is_dest(struct tipc_msg
*m
, u32 d
)
278 return(msg_short(m
) || (msg_destnode(m
) == d
));
281 static inline u32
msg_routed(struct tipc_msg
*m
)
283 if (likely(msg_short(m
)))
285 return(msg_destnode(m
) ^ msg_orignode(m
)) >> 11;
288 static inline void msg_set_nametype(struct tipc_msg
*m
, u32 n
)
290 msg_set_word(m
, 8, n
);
293 static inline u32
msg_transp_seqno(struct tipc_msg
*m
)
295 return msg_word(m
, 8);
298 static inline void msg_set_timestamp(struct tipc_msg
*m
, u32 n
)
300 msg_set_word(m
, 8, n
);
303 static inline u32
msg_timestamp(struct tipc_msg
*m
)
305 return msg_word(m
, 8);
308 static inline void msg_set_transp_seqno(struct tipc_msg
*m
, u32 n
)
310 msg_set_word(m
, 8, n
);
313 static inline void msg_set_namelower(struct tipc_msg
*m
, u32 n
)
315 msg_set_word(m
, 9, n
);
318 static inline void msg_set_nameinst(struct tipc_msg
*m
, u32 n
)
320 msg_set_namelower(m
, n
);
323 static inline void msg_set_nameupper(struct tipc_msg
*m
, u32 n
)
325 msg_set_word(m
, 10, n
);
328 static inline struct tipc_msg
*msg_get_wrapped(struct tipc_msg
*m
)
330 return (struct tipc_msg
*)msg_data(m
);
333 static inline void msg_expand(struct tipc_msg
*m
, u32 destnode
)
337 msg_set_hdr_sz(m
, LONG_H_SIZE
);
338 msg_set_orignode(m
, msg_prevnode(m
));
339 msg_set_destnode(m
, destnode
);
340 memset(&m
->hdr
[8], 0, 12);
346 TIPC internal message header format, version 2
348 1 0 9 8 7 6 5 4|3 2 1 0 9 8 7 6|5 4 3 2 1 0 9 8|7 6 5 4 3 2 1 0
349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
350 w0:|vers |msg usr|hdr sz |n|resrv| packet size |
351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
352 w1:|m typ|rsv=0| sequence gap | broadcast ack no |
353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
354 w2:| link level ack no/bc_gap_from | seq no / bcast_gap_to |
355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
358 w4:| next sent broadcast/fragm no | next sent pkt/ fragm msg no |
359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
360 w5:| session no |rsv=0|r|berid|link prio|netpl|p|
361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
362 w6:| originating node |
363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
364 w7:| destination node |
365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
366 w8:| transport sequence number |
367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
368 w9:| msg count / bcast tag | link tolerance |
369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
371 / User Specific Data /
373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
375 NB: CONN_MANAGER use data message format. LINK_CONFIG has own format.
382 #define BCAST_PROTOCOL 5
383 #define MSG_BUNDLER 6
384 #define LINK_PROTOCOL 7
385 #define CONN_MANAGER 8
386 #define ROUTE_DISTRIBUTOR 9
387 #define CHANGEOVER_PROTOCOL 10
388 #define NAME_DISTRIBUTOR 11
389 #define MSG_FRAGMENTER 12
390 #define LINK_CONFIG 13
391 #define INT_H_SIZE 40
392 #define DSC_H_SIZE 40
395 * Connection management protocol messages
399 #define CONN_PROBE_REPLY 1
403 * Name distributor messages
406 #define PUBLICATION 0
414 static inline u32
msg_seq_gap(struct tipc_msg
*m
)
416 return msg_bits(m
, 1, 16, 0xff);
419 static inline void msg_set_seq_gap(struct tipc_msg
*m
, u32 n
)
421 msg_set_bits(m
, 1, 16, 0xff, n
);
424 static inline u32
msg_req_links(struct tipc_msg
*m
)
426 return msg_bits(m
, 1, 16, 0xfff);
429 static inline void msg_set_req_links(struct tipc_msg
*m
, u32 n
)
431 msg_set_bits(m
, 1, 16, 0xfff, n
);
439 static inline u32
msg_dest_domain(struct tipc_msg
*m
)
441 return msg_word(m
, 2);
444 static inline void msg_set_dest_domain(struct tipc_msg
*m
, u32 n
)
446 msg_set_word(m
, 2, n
);
449 static inline u32
msg_bcgap_after(struct tipc_msg
*m
)
451 return msg_bits(m
, 2, 16, 0xffff);
454 static inline void msg_set_bcgap_after(struct tipc_msg
*m
, u32 n
)
456 msg_set_bits(m
, 2, 16, 0xffff, n
);
459 static inline u32
msg_bcgap_to(struct tipc_msg
*m
)
461 return msg_bits(m
, 2, 0, 0xffff);
464 static inline void msg_set_bcgap_to(struct tipc_msg
*m
, u32 n
)
466 msg_set_bits(m
, 2, 0, 0xffff, n
);
474 static inline u32
msg_last_bcast(struct tipc_msg
*m
)
476 return msg_bits(m
, 4, 16, 0xffff);
479 static inline void msg_set_last_bcast(struct tipc_msg
*m
, u32 n
)
481 msg_set_bits(m
, 4, 16, 0xffff, n
);
485 static inline u32
msg_fragm_no(struct tipc_msg
*m
)
487 return msg_bits(m
, 4, 16, 0xffff);
490 static inline void msg_set_fragm_no(struct tipc_msg
*m
, u32 n
)
492 msg_set_bits(m
, 4, 16, 0xffff, n
);
496 static inline u32
msg_next_sent(struct tipc_msg
*m
)
498 return msg_bits(m
, 4, 0, 0xffff);
501 static inline void msg_set_next_sent(struct tipc_msg
*m
, u32 n
)
503 msg_set_bits(m
, 4, 0, 0xffff, n
);
507 static inline u32
msg_long_msgno(struct tipc_msg
*m
)
509 return msg_bits(m
, 4, 0, 0xffff);
512 static inline void msg_set_long_msgno(struct tipc_msg
*m
, u32 n
)
514 msg_set_bits(m
, 4, 0, 0xffff, n
);
517 static inline u32
msg_bc_netid(struct tipc_msg
*m
)
519 return msg_word(m
, 4);
522 static inline void msg_set_bc_netid(struct tipc_msg
*m
, u32 id
)
524 msg_set_word(m
, 4, id
);
527 static inline u32
msg_link_selector(struct tipc_msg
*m
)
529 return msg_bits(m
, 4, 0, 1);
532 static inline void msg_set_link_selector(struct tipc_msg
*m
, u32 n
)
534 msg_set_bits(m
, 4, 0, 1, (n
& 1));
541 static inline u32
msg_session(struct tipc_msg
*m
)
543 return msg_bits(m
, 5, 16, 0xffff);
546 static inline void msg_set_session(struct tipc_msg
*m
, u32 n
)
548 msg_set_bits(m
, 5, 16, 0xffff, n
);
551 static inline u32
msg_probe(struct tipc_msg
*m
)
553 return msg_bits(m
, 5, 0, 1);
556 static inline void msg_set_probe(struct tipc_msg
*m
, u32 val
)
558 msg_set_bits(m
, 5, 0, 1, (val
& 1));
561 static inline char msg_net_plane(struct tipc_msg
*m
)
563 return msg_bits(m
, 5, 1, 7) + 'A';
566 static inline void msg_set_net_plane(struct tipc_msg
*m
, char n
)
568 msg_set_bits(m
, 5, 1, 7, (n
- 'A'));
571 static inline u32
msg_linkprio(struct tipc_msg
*m
)
573 return msg_bits(m
, 5, 4, 0x1f);
576 static inline void msg_set_linkprio(struct tipc_msg
*m
, u32 n
)
578 msg_set_bits(m
, 5, 4, 0x1f, n
);
581 static inline u32
msg_bearer_id(struct tipc_msg
*m
)
583 return msg_bits(m
, 5, 9, 0x7);
586 static inline void msg_set_bearer_id(struct tipc_msg
*m
, u32 n
)
588 msg_set_bits(m
, 5, 9, 0x7, n
);
591 static inline u32
msg_redundant_link(struct tipc_msg
*m
)
593 return msg_bits(m
, 5, 12, 0x1);
596 static inline void msg_set_redundant_link(struct tipc_msg
*m
)
598 msg_set_bits(m
, 5, 12, 0x1, 1);
601 static inline void msg_clear_redundant_link(struct tipc_msg
*m
)
603 msg_set_bits(m
, 5, 12, 0x1, 0);
611 static inline u32
msg_msgcnt(struct tipc_msg
*m
)
613 return msg_bits(m
, 9, 16, 0xffff);
616 static inline void msg_set_msgcnt(struct tipc_msg
*m
, u32 n
)
618 msg_set_bits(m
, 9, 16, 0xffff, n
);
621 static inline u32
msg_bcast_tag(struct tipc_msg
*m
)
623 return msg_bits(m
, 9, 16, 0xffff);
626 static inline void msg_set_bcast_tag(struct tipc_msg
*m
, u32 n
)
628 msg_set_bits(m
, 9, 16, 0xffff, n
);
631 static inline u32
msg_max_pkt(struct tipc_msg
*m
)
633 return (msg_bits(m
, 9, 16, 0xffff) * 4);
636 static inline void msg_set_max_pkt(struct tipc_msg
*m
, u32 n
)
638 msg_set_bits(m
, 9, 16, 0xffff, (n
/ 4));
641 static inline u32
msg_link_tolerance(struct tipc_msg
*m
)
643 return msg_bits(m
, 9, 0, 0xffff);
646 static inline void msg_set_link_tolerance(struct tipc_msg
*m
, u32 n
)
648 msg_set_bits(m
, 9, 0, 0xffff, n
);
652 * Routing table message data
656 static inline u32
msg_remote_node(struct tipc_msg
*m
)
658 return msg_word(m
, msg_hdr_sz(m
)/4);
661 static inline void msg_set_remote_node(struct tipc_msg
*m
, u32 a
)
663 msg_set_word(m
, msg_hdr_sz(m
)/4, a
);
666 static inline int msg_dataoctet(struct tipc_msg
*m
, u32 pos
)
668 return(msg_data(m
)[pos
+ 4] != 0);
671 static inline void msg_set_dataoctet(struct tipc_msg
*m
, u32 pos
)
673 msg_data(m
)[pos
+ 4] = 1;
677 * Segmentation message types
680 #define FIRST_FRAGMENT 0
682 #define LAST_FRAGMENT 2
685 * Link management protocol message types
690 #define ACTIVATE_MSG 2
693 * Changeover tunnel message types
695 #define DUPLICATE_MSG 0
696 #define ORIGINAL_MSG 1
699 * Routing table message types
701 #define EXT_ROUTING_TABLE 0
702 #define LOCAL_ROUTING_TABLE 1
703 #define SLAVE_ROUTING_TABLE 2
704 #define ROUTE_ADDITION 3
705 #define ROUTE_REMOVAL 4
708 * Config protocol message types
711 #define DSC_REQ_MSG 0
712 #define DSC_RESP_MSG 1
714 static inline u32
msg_tot_importance(struct tipc_msg
*m
)
716 if (likely(msg_isdata(m
))) {
717 if (likely(msg_orignode(m
) == tipc_own_addr
))
718 return msg_importance(m
);
719 return msg_importance(m
) + 4;
721 if ((msg_user(m
) == MSG_FRAGMENTER
) &&
722 (msg_type(m
) == FIRST_FRAGMENT
))
723 return msg_importance(msg_get_wrapped(m
));
724 return msg_importance(m
);
728 static inline void msg_init(struct tipc_msg
*m
, u32 user
, u32 type
,
729 u32 err
, u32 hsize
, u32 destnode
)
733 msg_set_user(m
, user
);
734 msg_set_hdr_sz(m
, hsize
);
735 msg_set_size(m
, hsize
);
736 msg_set_prevnode(m
, tipc_own_addr
);
737 msg_set_type(m
, type
);
738 msg_set_errcode(m
, err
);
740 msg_set_orignode(m
, tipc_own_addr
);
741 msg_set_destnode(m
, destnode
);
746 * msg_calc_data_size - determine total data size for message
749 static inline int msg_calc_data_size(struct iovec
const *msg_sect
, u32 num_sect
)
754 for (i
= 0; i
< num_sect
; i
++)
755 dsz
+= msg_sect
[i
].iov_len
;
760 * msg_build - create message using specified header and data
762 * Note: Caller must not hold any locks in case copy_from_user() is interrupted!
764 * Returns message data size or errno
767 static inline int msg_build(struct tipc_msg
*hdr
,
768 struct iovec
const *msg_sect
, u32 num_sect
,
769 int max_size
, int usrmem
, struct sk_buff
** buf
)
771 int dsz
, sz
, hsz
, pos
, res
, cnt
;
773 dsz
= msg_calc_data_size(msg_sect
, num_sect
);
774 if (unlikely(dsz
> TIPC_MAX_USER_MSG_SIZE
)) {
779 pos
= hsz
= msg_hdr_sz(hdr
);
781 msg_set_size(hdr
, sz
);
782 if (unlikely(sz
> max_size
)) {
787 *buf
= buf_acquire(sz
);
790 skb_copy_to_linear_data(*buf
, hdr
, hsz
);
791 for (res
= 1, cnt
= 0; res
&& (cnt
< num_sect
); cnt
++) {
793 res
= !copy_from_user((*buf
)->data
+ pos
,
794 msg_sect
[cnt
].iov_base
,
795 msg_sect
[cnt
].iov_len
);
797 skb_copy_to_linear_data_offset(*buf
, pos
,
798 msg_sect
[cnt
].iov_base
,
799 msg_sect
[cnt
].iov_len
);
800 pos
+= msg_sect
[cnt
].iov_len
;
810 static inline void msg_set_media_addr(struct tipc_msg
*m
, struct tipc_media_addr
*a
)
812 memcpy(&((int *)m
)[5], a
, sizeof(*a
));
815 static inline void msg_get_media_addr(struct tipc_msg
*m
, struct tipc_media_addr
*a
)
817 memcpy(a
, &((int*)m
)[5], sizeof(*a
));