Committer: Michael Beasley <mike@snafu.setup>
[mikesnafu-overlay.git] / net / tipc / msg.h
blobe9ef6df26562c224256006f4a71733347ca354f7
1 /*
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
6 * All rights reserved.
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.
37 #ifndef _TIPC_MSG_H
38 #define _TIPC_MSG_H
40 #include "core.h"
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);
80 * Word 0
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)
110 msg_set_user(m, 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);
155 * Word 1
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))
199 return;
200 msg_set_bits(m, 1, 16, 0x7, (hsz - 28)/4);
201 msg_set_hdr_sz(m, hsz + sz);
202 memcpy(to, opt, 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);
217 * Word 2
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);
242 * Words 3-10
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)))
284 return 0;
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)
335 if (!msg_short(m))
336 return;
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
356 w3:| previous node |
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.
379 * Internal users
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
398 #define CONN_PROBE 0
399 #define CONN_PROBE_REPLY 1
400 #define CONN_ACK 2
403 * Name distributor messages
406 #define PUBLICATION 0
407 #define WITHDRAWAL 1
411 * Word 1
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);
436 * Word 2
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);
471 * Word 4
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));
538 * Word 5
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);
608 * Word 9
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 void msg_set_dataoctet(struct tipc_msg *m, u32 pos)
668 msg_data(m)[pos + 4] = 1;
672 * Segmentation message types
675 #define FIRST_FRAGMENT 0
676 #define FRAGMENT 1
677 #define LAST_FRAGMENT 2
680 * Link management protocol message types
683 #define STATE_MSG 0
684 #define RESET_MSG 1
685 #define ACTIVATE_MSG 2
688 * Changeover tunnel message types
690 #define DUPLICATE_MSG 0
691 #define ORIGINAL_MSG 1
694 * Routing table message types
696 #define EXT_ROUTING_TABLE 0
697 #define LOCAL_ROUTING_TABLE 1
698 #define SLAVE_ROUTING_TABLE 2
699 #define ROUTE_ADDITION 3
700 #define ROUTE_REMOVAL 4
703 * Config protocol message types
706 #define DSC_REQ_MSG 0
707 #define DSC_RESP_MSG 1
709 static inline u32 msg_tot_importance(struct tipc_msg *m)
711 if (likely(msg_isdata(m))) {
712 if (likely(msg_orignode(m) == tipc_own_addr))
713 return msg_importance(m);
714 return msg_importance(m) + 4;
716 if ((msg_user(m) == MSG_FRAGMENTER) &&
717 (msg_type(m) == FIRST_FRAGMENT))
718 return msg_importance(msg_get_wrapped(m));
719 return msg_importance(m);
723 static inline void msg_init(struct tipc_msg *m, u32 user, u32 type,
724 u32 err, u32 hsize, u32 destnode)
726 memset(m, 0, hsize);
727 msg_set_version(m);
728 msg_set_user(m, user);
729 msg_set_hdr_sz(m, hsize);
730 msg_set_size(m, hsize);
731 msg_set_prevnode(m, tipc_own_addr);
732 msg_set_type(m, type);
733 msg_set_errcode(m, err);
734 if (!msg_short(m)) {
735 msg_set_orignode(m, tipc_own_addr);
736 msg_set_destnode(m, destnode);
741 * msg_calc_data_size - determine total data size for message
744 static inline int msg_calc_data_size(struct iovec const *msg_sect, u32 num_sect)
746 int dsz = 0;
747 int i;
749 for (i = 0; i < num_sect; i++)
750 dsz += msg_sect[i].iov_len;
751 return dsz;
755 * msg_build - create message using specified header and data
757 * Note: Caller must not hold any locks in case copy_from_user() is interrupted!
759 * Returns message data size or errno
762 static inline int msg_build(struct tipc_msg *hdr,
763 struct iovec const *msg_sect, u32 num_sect,
764 int max_size, int usrmem, struct sk_buff** buf)
766 int dsz, sz, hsz, pos, res, cnt;
768 dsz = msg_calc_data_size(msg_sect, num_sect);
769 if (unlikely(dsz > TIPC_MAX_USER_MSG_SIZE)) {
770 *buf = NULL;
771 return -EINVAL;
774 pos = hsz = msg_hdr_sz(hdr);
775 sz = hsz + dsz;
776 msg_set_size(hdr, sz);
777 if (unlikely(sz > max_size)) {
778 *buf = NULL;
779 return dsz;
782 *buf = buf_acquire(sz);
783 if (!(*buf))
784 return -ENOMEM;
785 skb_copy_to_linear_data(*buf, hdr, hsz);
786 for (res = 1, cnt = 0; res && (cnt < num_sect); cnt++) {
787 if (likely(usrmem))
788 res = !copy_from_user((*buf)->data + pos,
789 msg_sect[cnt].iov_base,
790 msg_sect[cnt].iov_len);
791 else
792 skb_copy_to_linear_data_offset(*buf, pos,
793 msg_sect[cnt].iov_base,
794 msg_sect[cnt].iov_len);
795 pos += msg_sect[cnt].iov_len;
797 if (likely(res))
798 return dsz;
800 buf_discard(*buf);
801 *buf = NULL;
802 return -EFAULT;
805 static inline void msg_set_media_addr(struct tipc_msg *m, struct tipc_media_addr *a)
807 memcpy(&((int *)m)[5], a, sizeof(*a));
810 static inline void msg_get_media_addr(struct tipc_msg *m, struct tipc_media_addr *a)
812 memcpy(a, &((int*)m)[5], sizeof(*a));
815 #endif