include/uapi/linux/pkt_cls.h

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 #ifndef __LINUX_PKT_CLS_H
   3 #define __LINUX_PKT_CLS_H
   4
   5 #include <linux/types.h>
   6 #include <linux/pkt_sched.h>
   7
   8 #define TC_COOKIE_MAX_SIZE 16
   9
  10 /* Action attributes */
  11 enum {
  12         TCA_ACT_UNSPEC,
  13         TCA_ACT_KIND,
  14         TCA_ACT_OPTIONS,
  15         TCA_ACT_INDEX,
  16         TCA_ACT_STATS,
  17         TCA_ACT_PAD,
  18         TCA_ACT_COOKIE,
  19         __TCA_ACT_MAX
  20 };
  21
  22 #define TCA_ACT_MAX __TCA_ACT_MAX
  23 #define TCA_OLD_COMPAT (TCA_ACT_MAX+1)
  24 #define TCA_ACT_MAX_PRIO 32
  25 #define TCA_ACT_BIND    1
  26 #define TCA_ACT_NOBIND  0
  27 #define TCA_ACT_UNBIND  1
  28 #define TCA_ACT_NOUNBIND        0
  29 #define TCA_ACT_REPLACE         1
  30 #define TCA_ACT_NOREPLACE       0
  31
  32 #define TC_ACT_UNSPEC   (-1)
  33 #define TC_ACT_OK               0
  34 #define TC_ACT_RECLASSIFY       1
  35 #define TC_ACT_SHOT             2
  36 #define TC_ACT_PIPE             3
  37 #define TC_ACT_STOLEN           4
  38 #define TC_ACT_QUEUED           5
  39 #define TC_ACT_REPEAT           6
  40 #define TC_ACT_REDIRECT         7
  41 #define TC_ACT_TRAP             8 /* For hw path, this means "trap to cpu"
  42                                    * and don't further process the frame
  43                                    * in hardware. For sw path, this is
  44                                    * equivalent of TC_ACT_STOLEN - drop
  45                                    * the skb and act like everything
  46                                    * is alright.
  47                                    */
  48
  49 /* There is a special kind of actions called "extended actions",
  50  * which need a value parameter. These have a local opcode located in
  51  * the highest nibble, starting from 1. The rest of the bits
  52  * are used to carry the value. These two parts together make
  53  * a combined opcode.
  54  */
  55 #define __TC_ACT_EXT_SHIFT 28
  56 #define __TC_ACT_EXT(local) ((local) << __TC_ACT_EXT_SHIFT)
  57 #define TC_ACT_EXT_VAL_MASK ((1 << __TC_ACT_EXT_SHIFT) - 1)
  58 #define TC_ACT_EXT_CMP(combined, opcode) \
  59         (((combined) & (~TC_ACT_EXT_VAL_MASK)) == opcode)
  60
  61 #define TC_ACT_JUMP __TC_ACT_EXT(1)
  62 #define TC_ACT_GOTO_CHAIN __TC_ACT_EXT(2)
  63
  64 /* Action type identifiers*/
  65 enum {
  66         TCA_ID_UNSPEC=0,
  67         TCA_ID_POLICE=1,
  68         /* other actions go here */
  69         __TCA_ID_MAX=255
  70 };
  71
  72 #define TCA_ID_MAX __TCA_ID_MAX
  73
  74 struct tc_police {
  75         __u32                   index;
  76         int                     action;
  77 #define TC_POLICE_UNSPEC        TC_ACT_UNSPEC
  78 #define TC_POLICE_OK            TC_ACT_OK
  79 #define TC_POLICE_RECLASSIFY    TC_ACT_RECLASSIFY
  80 #define TC_POLICE_SHOT          TC_ACT_SHOT
  81 #define TC_POLICE_PIPE          TC_ACT_PIPE
  82
  83         __u32                   limit;
  84         __u32                   burst;
  85         __u32                   mtu;
  86         struct tc_ratespec      rate;
  87         struct tc_ratespec      peakrate;
  88         int                     refcnt;
  89         int                     bindcnt;
  90         __u32                   capab;
  91 };
  92
  93 struct tcf_t {
  94         __u64   install;
  95         __u64   lastuse;
  96         __u64   expires;
  97         __u64   firstuse;
  98 };
  99
 100 struct tc_cnt {
 101         int                   refcnt;
 102         int                   bindcnt;
 103 };
 104
 105 #define tc_gen \
 106         __u32                 index; \
 107         __u32                 capab; \
 108         int                   action; \
 109         int                   refcnt; \
 110         int                   bindcnt
 111
 112 enum {
 113         TCA_POLICE_UNSPEC,
 114         TCA_POLICE_TBF,
 115         TCA_POLICE_RATE,
 116         TCA_POLICE_PEAKRATE,
 117         TCA_POLICE_AVRATE,
 118         TCA_POLICE_RESULT,
 119         TCA_POLICE_TM,
 120         TCA_POLICE_PAD,
 121         __TCA_POLICE_MAX
 122 #define TCA_POLICE_RESULT TCA_POLICE_RESULT
 123 };
 124
 125 #define TCA_POLICE_MAX (__TCA_POLICE_MAX - 1)
 126
 127 /* tca flags definitions */
 128 #define TCA_CLS_FLAGS_SKIP_HW   (1 << 0) /* don't offload filter to HW */
 129 #define TCA_CLS_FLAGS_SKIP_SW   (1 << 1) /* don't use filter in SW */
 130 #define TCA_CLS_FLAGS_IN_HW     (1 << 2) /* filter is offloaded to HW */
 131 #define TCA_CLS_FLAGS_NOT_IN_HW (1 << 3) /* filter isn't offloaded to HW */
 132
 133 /* U32 filters */
 134
 135 #define TC_U32_HTID(h) ((h)&0xFFF00000)
 136 #define TC_U32_USERHTID(h) (TC_U32_HTID(h)>>20)
 137 #define TC_U32_HASH(h) (((h)>>12)&0xFF)
 138 #define TC_U32_NODE(h) ((h)&0xFFF)
 139 #define TC_U32_KEY(h) ((h)&0xFFFFF)
 140 #define TC_U32_UNSPEC   0
 141 #define TC_U32_ROOT     (0xFFF00000)
 142
 143 enum {
 144         TCA_U32_UNSPEC,
 145         TCA_U32_CLASSID,
 146         TCA_U32_HASH,
 147         TCA_U32_LINK,
 148         TCA_U32_DIVISOR,
 149         TCA_U32_SEL,
 150         TCA_U32_POLICE,
 151         TCA_U32_ACT,
 152         TCA_U32_INDEV,
 153         TCA_U32_PCNT,
 154         TCA_U32_MARK,
 155         TCA_U32_FLAGS,
 156         TCA_U32_PAD,
 157         __TCA_U32_MAX
 158 };
 159
 160 #define TCA_U32_MAX (__TCA_U32_MAX - 1)
 161
 162 struct tc_u32_key {
 163         __be32          mask;
 164         __be32          val;
 165         int             off;
 166         int             offmask;
 167 };
 168
 169 struct tc_u32_sel {
 170         unsigned char           flags;
 171         unsigned char           offshift;
 172         unsigned char           nkeys;
 173
 174         __be16                  offmask;
 175         __u16                   off;
 176         short                   offoff;
 177
 178         short                   hoff;
 179         __be32                  hmask;
 180         struct tc_u32_key       keys[0];
 181 };
 182
 183 struct tc_u32_mark {
 184         __u32           val;
 185         __u32           mask;
 186         __u32           success;
 187 };
 188
 189 struct tc_u32_pcnt {
 190         __u64 rcnt;
 191         __u64 rhit;
 192         __u64 kcnts[0];
 193 };
 194
 195 /* Flags */
 196
 197 #define TC_U32_TERMINAL         1
 198 #define TC_U32_OFFSET           2
 199 #define TC_U32_VAROFFSET        4
 200 #define TC_U32_EAT              8
 201
 202 #define TC_U32_MAXDEPTH 8
 203
 204
 205 /* RSVP filter */
 206
 207 enum {
 208         TCA_RSVP_UNSPEC,
 209         TCA_RSVP_CLASSID,
 210         TCA_RSVP_DST,
 211         TCA_RSVP_SRC,
 212         TCA_RSVP_PINFO,
 213         TCA_RSVP_POLICE,
 214         TCA_RSVP_ACT,
 215         __TCA_RSVP_MAX
 216 };
 217
 218 #define TCA_RSVP_MAX (__TCA_RSVP_MAX - 1 )
 219
 220 struct tc_rsvp_gpi {
 221         __u32   key;
 222         __u32   mask;
 223         int     offset;
 224 };
 225
 226 struct tc_rsvp_pinfo {
 227         struct tc_rsvp_gpi dpi;
 228         struct tc_rsvp_gpi spi;
 229         __u8    protocol;
 230         __u8    tunnelid;
 231         __u8    tunnelhdr;
 232         __u8    pad;
 233 };
 234
 235 /* ROUTE filter */
 236
 237 enum {
 238         TCA_ROUTE4_UNSPEC,
 239         TCA_ROUTE4_CLASSID,
 240         TCA_ROUTE4_TO,
 241         TCA_ROUTE4_FROM,
 242         TCA_ROUTE4_IIF,
 243         TCA_ROUTE4_POLICE,
 244         TCA_ROUTE4_ACT,
 245         __TCA_ROUTE4_MAX
 246 };
 247
 248 #define TCA_ROUTE4_MAX (__TCA_ROUTE4_MAX - 1)
 249
 250
 251 /* FW filter */
 252
 253 enum {
 254         TCA_FW_UNSPEC,
 255         TCA_FW_CLASSID,
 256         TCA_FW_POLICE,
 257         TCA_FW_INDEV, /*  used by CONFIG_NET_CLS_IND */
 258         TCA_FW_ACT, /* used by CONFIG_NET_CLS_ACT */
 259         TCA_FW_MASK,
 260         __TCA_FW_MAX
 261 };
 262
 263 #define TCA_FW_MAX (__TCA_FW_MAX - 1)
 264
 265 /* TC index filter */
 266
 267 enum {
 268         TCA_TCINDEX_UNSPEC,
 269         TCA_TCINDEX_HASH,
 270         TCA_TCINDEX_MASK,
 271         TCA_TCINDEX_SHIFT,
 272         TCA_TCINDEX_FALL_THROUGH,
 273         TCA_TCINDEX_CLASSID,
 274         TCA_TCINDEX_POLICE,
 275         TCA_TCINDEX_ACT,
 276         __TCA_TCINDEX_MAX
 277 };
 278
 279 #define TCA_TCINDEX_MAX     (__TCA_TCINDEX_MAX - 1)
 280
 281 /* Flow filter */
 282
 283 enum {
 284         FLOW_KEY_SRC,
 285         FLOW_KEY_DST,
 286         FLOW_KEY_PROTO,
 287         FLOW_KEY_PROTO_SRC,
 288         FLOW_KEY_PROTO_DST,
 289         FLOW_KEY_IIF,
 290         FLOW_KEY_PRIORITY,
 291         FLOW_KEY_MARK,
 292         FLOW_KEY_NFCT,
 293         FLOW_KEY_NFCT_SRC,
 294         FLOW_KEY_NFCT_DST,
 295         FLOW_KEY_NFCT_PROTO_SRC,
 296         FLOW_KEY_NFCT_PROTO_DST,
 297         FLOW_KEY_RTCLASSID,
 298         FLOW_KEY_SKUID,
 299         FLOW_KEY_SKGID,
 300         FLOW_KEY_VLAN_TAG,
 301         FLOW_KEY_RXHASH,
 302         __FLOW_KEY_MAX,
 303 };
 304
 305 #define FLOW_KEY_MAX    (__FLOW_KEY_MAX - 1)
 306
 307 enum {
 308         FLOW_MODE_MAP,
 309         FLOW_MODE_HASH,
 310 };
 311
 312 enum {
 313         TCA_FLOW_UNSPEC,
 314         TCA_FLOW_KEYS,
 315         TCA_FLOW_MODE,
 316         TCA_FLOW_BASECLASS,
 317         TCA_FLOW_RSHIFT,
 318         TCA_FLOW_ADDEND,
 319         TCA_FLOW_MASK,
 320         TCA_FLOW_XOR,
 321         TCA_FLOW_DIVISOR,
 322         TCA_FLOW_ACT,
 323         TCA_FLOW_POLICE,
 324         TCA_FLOW_EMATCHES,
 325         TCA_FLOW_PERTURB,
 326         __TCA_FLOW_MAX
 327 };
 328
 329 #define TCA_FLOW_MAX    (__TCA_FLOW_MAX - 1)
 330
 331 /* Basic filter */
 332
 333 enum {
 334         TCA_BASIC_UNSPEC,
 335         TCA_BASIC_CLASSID,
 336         TCA_BASIC_EMATCHES,
 337         TCA_BASIC_ACT,
 338         TCA_BASIC_POLICE,
 339         __TCA_BASIC_MAX
 340 };
 341
 342 #define TCA_BASIC_MAX (__TCA_BASIC_MAX - 1)
 343
 344
 345 /* Cgroup classifier */
 346
 347 enum {
 348         TCA_CGROUP_UNSPEC,
 349         TCA_CGROUP_ACT,
 350         TCA_CGROUP_POLICE,
 351         TCA_CGROUP_EMATCHES,
 352         __TCA_CGROUP_MAX,
 353 };
 354
 355 #define TCA_CGROUP_MAX (__TCA_CGROUP_MAX - 1)
 356
 357 /* BPF classifier */
 358
 359 #define TCA_BPF_FLAG_ACT_DIRECT         (1 << 0)
 360
 361 enum {
 362         TCA_BPF_UNSPEC,
 363         TCA_BPF_ACT,
 364         TCA_BPF_POLICE,
 365         TCA_BPF_CLASSID,
 366         TCA_BPF_OPS_LEN,
 367         TCA_BPF_OPS,
 368         TCA_BPF_FD,
 369         TCA_BPF_NAME,
 370         TCA_BPF_FLAGS,
 371         TCA_BPF_FLAGS_GEN,
 372         TCA_BPF_TAG,
 373         TCA_BPF_ID,
 374         __TCA_BPF_MAX,
 375 };
 376
 377 #define TCA_BPF_MAX (__TCA_BPF_MAX - 1)
 378
 379 /* Flower classifier */
 380
 381 enum {
 382         TCA_FLOWER_UNSPEC,
 383         TCA_FLOWER_CLASSID,
 384         TCA_FLOWER_INDEV,
 385         TCA_FLOWER_ACT,
 386         TCA_FLOWER_KEY_ETH_DST,         /* ETH_ALEN */
 387         TCA_FLOWER_KEY_ETH_DST_MASK,    /* ETH_ALEN */
 388         TCA_FLOWER_KEY_ETH_SRC,         /* ETH_ALEN */
 389         TCA_FLOWER_KEY_ETH_SRC_MASK,    /* ETH_ALEN */
 390         TCA_FLOWER_KEY_ETH_TYPE,        /* be16 */
 391         TCA_FLOWER_KEY_IP_PROTO,        /* u8 */
 392         TCA_FLOWER_KEY_IPV4_SRC,        /* be32 */
 393         TCA_FLOWER_KEY_IPV4_SRC_MASK,   /* be32 */
 394         TCA_FLOWER_KEY_IPV4_DST,        /* be32 */
 395         TCA_FLOWER_KEY_IPV4_DST_MASK,   /* be32 */
 396         TCA_FLOWER_KEY_IPV6_SRC,        /* struct in6_addr */
 397         TCA_FLOWER_KEY_IPV6_SRC_MASK,   /* struct in6_addr */
 398         TCA_FLOWER_KEY_IPV6_DST,        /* struct in6_addr */
 399         TCA_FLOWER_KEY_IPV6_DST_MASK,   /* struct in6_addr */
 400         TCA_FLOWER_KEY_TCP_SRC,         /* be16 */
 401         TCA_FLOWER_KEY_TCP_DST,         /* be16 */
 402         TCA_FLOWER_KEY_UDP_SRC,         /* be16 */
 403         TCA_FLOWER_KEY_UDP_DST,         /* be16 */
 404
 405         TCA_FLOWER_FLAGS,
 406         TCA_FLOWER_KEY_VLAN_ID,         /* be16 */
 407         TCA_FLOWER_KEY_VLAN_PRIO,       /* u8   */
 408         TCA_FLOWER_KEY_VLAN_ETH_TYPE,   /* be16 */
 409
 410         TCA_FLOWER_KEY_ENC_KEY_ID,      /* be32 */
 411         TCA_FLOWER_KEY_ENC_IPV4_SRC,    /* be32 */
 412         TCA_FLOWER_KEY_ENC_IPV4_SRC_MASK,/* be32 */
 413         TCA_FLOWER_KEY_ENC_IPV4_DST,    /* be32 */
 414         TCA_FLOWER_KEY_ENC_IPV4_DST_MASK,/* be32 */
 415         TCA_FLOWER_KEY_ENC_IPV6_SRC,    /* struct in6_addr */
 416         TCA_FLOWER_KEY_ENC_IPV6_SRC_MASK,/* struct in6_addr */
 417         TCA_FLOWER_KEY_ENC_IPV6_DST,    /* struct in6_addr */
 418         TCA_FLOWER_KEY_ENC_IPV6_DST_MASK,/* struct in6_addr */
 419
 420         TCA_FLOWER_KEY_TCP_SRC_MASK,    /* be16 */
 421         TCA_FLOWER_KEY_TCP_DST_MASK,    /* be16 */
 422         TCA_FLOWER_KEY_UDP_SRC_MASK,    /* be16 */
 423         TCA_FLOWER_KEY_UDP_DST_MASK,    /* be16 */
 424         TCA_FLOWER_KEY_SCTP_SRC_MASK,   /* be16 */
 425         TCA_FLOWER_KEY_SCTP_DST_MASK,   /* be16 */
 426
 427         TCA_FLOWER_KEY_SCTP_SRC,        /* be16 */
 428         TCA_FLOWER_KEY_SCTP_DST,        /* be16 */
 429
 430         TCA_FLOWER_KEY_ENC_UDP_SRC_PORT,        /* be16 */
 431         TCA_FLOWER_KEY_ENC_UDP_SRC_PORT_MASK,   /* be16 */
 432         TCA_FLOWER_KEY_ENC_UDP_DST_PORT,        /* be16 */
 433         TCA_FLOWER_KEY_ENC_UDP_DST_PORT_MASK,   /* be16 */
 434
 435         TCA_FLOWER_KEY_FLAGS,           /* be32 */
 436         TCA_FLOWER_KEY_FLAGS_MASK,      /* be32 */
 437
 438         TCA_FLOWER_KEY_ICMPV4_CODE,     /* u8 */
 439         TCA_FLOWER_KEY_ICMPV4_CODE_MASK,/* u8 */
 440         TCA_FLOWER_KEY_ICMPV4_TYPE,     /* u8 */
 441         TCA_FLOWER_KEY_ICMPV4_TYPE_MASK,/* u8 */
 442         TCA_FLOWER_KEY_ICMPV6_CODE,     /* u8 */
 443         TCA_FLOWER_KEY_ICMPV6_CODE_MASK,/* u8 */
 444         TCA_FLOWER_KEY_ICMPV6_TYPE,     /* u8 */
 445         TCA_FLOWER_KEY_ICMPV6_TYPE_MASK,/* u8 */
 446
 447         TCA_FLOWER_KEY_ARP_SIP,         /* be32 */
 448         TCA_FLOWER_KEY_ARP_SIP_MASK,    /* be32 */
 449         TCA_FLOWER_KEY_ARP_TIP,         /* be32 */
 450         TCA_FLOWER_KEY_ARP_TIP_MASK,    /* be32 */
 451         TCA_FLOWER_KEY_ARP_OP,          /* u8 */
 452         TCA_FLOWER_KEY_ARP_OP_MASK,     /* u8 */
 453         TCA_FLOWER_KEY_ARP_SHA,         /* ETH_ALEN */
 454         TCA_FLOWER_KEY_ARP_SHA_MASK,    /* ETH_ALEN */
 455         TCA_FLOWER_KEY_ARP_THA,         /* ETH_ALEN */
 456         TCA_FLOWER_KEY_ARP_THA_MASK,    /* ETH_ALEN */
 457
 458         TCA_FLOWER_KEY_MPLS_TTL,        /* u8 - 8 bits */
 459         TCA_FLOWER_KEY_MPLS_BOS,        /* u8 - 1 bit */
 460         TCA_FLOWER_KEY_MPLS_TC,         /* u8 - 3 bits */
 461         TCA_FLOWER_KEY_MPLS_LABEL,      /* be32 - 20 bits */
 462
 463         TCA_FLOWER_KEY_TCP_FLAGS,       /* be16 */
 464         TCA_FLOWER_KEY_TCP_FLAGS_MASK,  /* be16 */
 465
 466         TCA_FLOWER_KEY_IP_TOS,          /* u8 */
 467         TCA_FLOWER_KEY_IP_TOS_MASK,     /* u8 */
 468         TCA_FLOWER_KEY_IP_TTL,          /* u8 */
 469         TCA_FLOWER_KEY_IP_TTL_MASK,     /* u8 */
 470
 471         __TCA_FLOWER_MAX,
 472 };
 473
 474 #define TCA_FLOWER_MAX (__TCA_FLOWER_MAX - 1)
 475
 476 enum {
 477         TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT = (1 << 0),
 478 };
 479
 480 /* Match-all classifier */
 481
 482 enum {
 483         TCA_MATCHALL_UNSPEC,
 484         TCA_MATCHALL_CLASSID,
 485         TCA_MATCHALL_ACT,
 486         TCA_MATCHALL_FLAGS,
 487         __TCA_MATCHALL_MAX,
 488 };
 489
 490 #define TCA_MATCHALL_MAX (__TCA_MATCHALL_MAX - 1)
 491
 492 /* Extended Matches */
 493
 494 struct tcf_ematch_tree_hdr {
 495         __u16           nmatches;
 496         __u16           progid;
 497 };
 498
 499 enum {
 500         TCA_EMATCH_TREE_UNSPEC,
 501         TCA_EMATCH_TREE_HDR,
 502         TCA_EMATCH_TREE_LIST,
 503         __TCA_EMATCH_TREE_MAX
 504 };
 505 #define TCA_EMATCH_TREE_MAX (__TCA_EMATCH_TREE_MAX - 1)
 506
 507 struct tcf_ematch_hdr {
 508         __u16           matchid;
 509         __u16           kind;
 510         __u16           flags;
 511         __u16           pad; /* currently unused */
 512 };
 513
 514 /*  0                   1
 515  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 516  * +-----------------------+-+-+---+
 517  * |         Unused        |S|I| R |
 518  * +-----------------------+-+-+---+
 519  *
 520  * R(2) ::= relation to next ematch
 521  *          where: 0 0 END (last ematch)
 522  *                 0 1 AND
 523  *                 1 0 OR
 524  *                 1 1 Unused (invalid)
 525  * I(1) ::= invert result
 526  * S(1) ::= simple payload
 527  */
 528 #define TCF_EM_REL_END  0
 529 #define TCF_EM_REL_AND  (1<<0)
 530 #define TCF_EM_REL_OR   (1<<1)
 531 #define TCF_EM_INVERT   (1<<2)
 532 #define TCF_EM_SIMPLE   (1<<3)
 533
 534 #define TCF_EM_REL_MASK 3
 535 #define TCF_EM_REL_VALID(v) (((v) & TCF_EM_REL_MASK) != TCF_EM_REL_MASK)
 536
 537 enum {
 538         TCF_LAYER_LINK,
 539         TCF_LAYER_NETWORK,
 540         TCF_LAYER_TRANSPORT,
 541         __TCF_LAYER_MAX
 542 };
 543 #define TCF_LAYER_MAX (__TCF_LAYER_MAX - 1)
 544
 545 /* Ematch type assignments
 546  *   1..32767           Reserved for ematches inside kernel tree
 547  *   32768..65535       Free to use, not reliable
 548  */
 549 #define TCF_EM_CONTAINER        0
 550 #define TCF_EM_CMP              1
 551 #define TCF_EM_NBYTE            2
 552 #define TCF_EM_U32              3
 553 #define TCF_EM_META             4
 554 #define TCF_EM_TEXT             5
 555 #define TCF_EM_VLAN             6
 556 #define TCF_EM_CANID            7
 557 #define TCF_EM_IPSET            8
 558 #define TCF_EM_IPT              9
 559 #define TCF_EM_MAX              9
 560
 561 enum {
 562         TCF_EM_PROG_TC
 563 };
 564
 565 enum {
 566         TCF_EM_OPND_EQ,
 567         TCF_EM_OPND_GT,
 568         TCF_EM_OPND_LT
 569 };
 570
 571 #endif