1 /* 2 * Berkeley Packet Filter based traffic classifier 3 * 4 * Might be used to classify traffic through flexible, user-defined and 5 * possibly JIT-ed BPF filters for traffic control as an alternative to 6 * ematches. 7 * 8 * (C) 2013 Daniel Borkmann <dborkman@redhat.com> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License version 2 as 12 * published by the Free Software Foundation. 13 */ 14 15 #include <linux/module.h> 16 #include <linux/types.h> 17 #include <linux/skbuff.h> 18 #include <linux/filter.h> 19 #include <linux/bpf.h> 20 #include <linux/idr.h> 21 22 #include <net/rtnetlink.h> 23 #include <net/pkt_cls.h> 24 #include <net/sock.h> 25 26 MODULE_LICENSE("GPL"); 27 MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>"); 28 MODULE_DESCRIPTION("TC BPF based classifier"); 29 30 #define CLS_BPF_NAME_LEN 256 31 #define CLS_BPF_SUPPORTED_GEN_FLAGS \ 32 (TCA_CLS_FLAGS_SKIP_HW | TCA_CLS_FLAGS_SKIP_SW) 33 34 struct cls_bpf_head { 35 struct list_head plist; 36 struct idr handle_idr; 37 struct rcu_head rcu; 38 }; 39 40 struct cls_bpf_prog { 41 struct bpf_prog *filter; 42 struct list_head link; 43 struct tcf_result res; 44 bool exts_integrated; 45 bool offloaded; 46 u32 gen_flags; 47 struct tcf_exts exts; 48 u32 handle; 49 u16 bpf_num_ops; 50 struct sock_filter *bpf_ops; 51 const char *bpf_name; 52 struct tcf_proto *tp; 53 union { 54 struct work_struct work; 55 struct rcu_head rcu; 56 }; 57 }; 58 59 static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = { 60 [TCA_BPF_CLASSID] = { .type = NLA_U32 }, 61 [TCA_BPF_FLAGS] = { .type = NLA_U32 }, 62 [TCA_BPF_FLAGS_GEN] = { .type = NLA_U32 }, 63 [TCA_BPF_FD] = { .type = NLA_U32 }, 64 [TCA_BPF_NAME] = { .type = NLA_NUL_STRING, 65 .len = CLS_BPF_NAME_LEN }, 66 [TCA_BPF_OPS_LEN] = { .type = NLA_U16 }, 67 [TCA_BPF_OPS] = { .type = NLA_BINARY, 68 .len = sizeof(struct sock_filter) * BPF_MAXINSNS }, 69 }; 70 71 static int cls_bpf_exec_opcode(int code) 72 { 73 switch (code) { 74 case TC_ACT_OK: 75 case TC_ACT_SHOT: 76 case TC_ACT_STOLEN: 77 case TC_ACT_TRAP: 78 case TC_ACT_REDIRECT: 79 case TC_ACT_UNSPEC: 80 return code; 81 default: 82 return TC_ACT_UNSPEC; 83 } 84 } 85 86 static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp, 87 struct tcf_result *res) 88 { 89 struct cls_bpf_head *head = rcu_dereference_bh(tp->root); 90 bool at_ingress = skb_at_tc_ingress(skb); 91 struct cls_bpf_prog *prog; 92 int ret = -1; 93 94 /* Needed here for accessing maps. */ 95 rcu_read_lock(); 96 list_for_each_entry_rcu(prog, &head->plist, link) { 97 int filter_res; 98 99 qdisc_skb_cb(skb)->tc_classid = prog->res.classid; 100 101 if (tc_skip_sw(prog->gen_flags)) { 102 filter_res = prog->exts_integrated ? TC_ACT_UNSPEC : 0; 103 } else if (at_ingress) { 104 /* It is safe to push/pull even if skb_shared() */ 105 __skb_push(skb, skb->mac_len); 106 bpf_compute_data_pointers(skb); 107 filter_res = BPF_PROG_RUN(prog->filter, skb); 108 __skb_pull(skb, skb->mac_len); 109 } else { 110 bpf_compute_data_pointers(skb); 111 filter_res = BPF_PROG_RUN(prog->filter, skb); 112 } 113 114 if (prog->exts_integrated) { 115 res->class = 0; 116 res->classid = TC_H_MAJ(prog->res.classid) | 117 qdisc_skb_cb(skb)->tc_classid; 118 119 ret = cls_bpf_exec_opcode(filter_res); 120 if (ret == TC_ACT_UNSPEC) 121 continue; 122 break; 123 } 124 125 if (filter_res == 0) 126 continue; 127 if (filter_res != -1) { 128 res->class = 0; 129 res->classid = filter_res; 130 } else { 131 *res = prog->res; 132 } 133 134 ret = tcf_exts_exec(skb, &prog->exts, res); 135 if (ret < 0) 136 continue; 137 138 break; 139 } 140 rcu_read_unlock(); 141 142 return ret; 143 } 144 145 static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog) 146 { 147 return !prog->bpf_ops; 148 } 149 150 static int cls_bpf_offload_cmd(struct tcf_proto *tp, struct cls_bpf_prog *prog, 151 enum tc_clsbpf_command cmd) 152 { 153 bool addorrep = cmd == TC_CLSBPF_ADD || cmd == TC_CLSBPF_REPLACE; 154 struct tcf_block *block = tp->chain->block; 155 bool skip_sw = tc_skip_sw(prog->gen_flags); 156 struct tc_cls_bpf_offload cls_bpf = {}; 157 int err; 158 159 tc_cls_common_offload_init(&cls_bpf.common, tp); 160 cls_bpf.command = cmd; 161 cls_bpf.exts = &prog->exts; 162 cls_bpf.prog = prog->filter; 163 cls_bpf.name = prog->bpf_name; 164 cls_bpf.exts_integrated = prog->exts_integrated; 165 cls_bpf.gen_flags = prog->gen_flags; 166 167 err = tc_setup_cb_call(block, NULL, TC_SETUP_CLSBPF, &cls_bpf, skip_sw); 168 if (addorrep) { 169 if (err < 0) { 170 cls_bpf_offload_cmd(tp, prog, TC_CLSBPF_DESTROY); 171 return err; 172 } else if (err > 0) { 173 prog->gen_flags |= TCA_CLS_FLAGS_IN_HW; 174 } 175 } 176 177 if (addorrep && skip_sw && !(prog->gen_flags & TCA_CLS_FLAGS_IN_HW)) 178 return -EINVAL; 179 180 return 0; 181 } 182 183 static int cls_bpf_offload(struct tcf_proto *tp, struct cls_bpf_prog *prog, 184 struct cls_bpf_prog *oldprog) 185 { 186 struct cls_bpf_prog *obj = prog; 187 enum tc_clsbpf_command cmd; 188 bool skip_sw; 189 int ret; 190 191 skip_sw = tc_skip_sw(prog->gen_flags) || 192 (oldprog && tc_skip_sw(oldprog->gen_flags)); 193 194 if (oldprog && oldprog->offloaded) { 195 if (!tc_skip_hw(prog->gen_flags)) { 196 cmd = TC_CLSBPF_REPLACE; 197 } else if (!tc_skip_sw(prog->gen_flags)) { 198 obj = oldprog; 199 cmd = TC_CLSBPF_DESTROY; 200 } else { 201 return -EINVAL; 202 } 203 } else { 204 if (tc_skip_hw(prog->gen_flags)) 205 return skip_sw ? -EINVAL : 0; 206 cmd = TC_CLSBPF_ADD; 207 } 208 209 ret = cls_bpf_offload_cmd(tp, obj, cmd); 210 if (ret) 211 return ret; 212 213 obj->offloaded = true; 214 if (oldprog) 215 oldprog->offloaded = false; 216 217 return 0; 218 } 219 220 static void cls_bpf_stop_offload(struct tcf_proto *tp, 221 struct cls_bpf_prog *prog) 222 { 223 int err; 224 225 if (!prog->offloaded) 226 return; 227 228 err = cls_bpf_offload_cmd(tp, prog, TC_CLSBPF_DESTROY); 229 if (err) { 230 pr_err("Stopping hardware offload failed: %d\n", err); 231 return; 232 } 233 234 prog->offloaded = false; 235 } 236 237 static void cls_bpf_offload_update_stats(struct tcf_proto *tp, 238 struct cls_bpf_prog *prog) 239 { 240 if (!prog->offloaded) 241 return; 242 243 cls_bpf_offload_cmd(tp, prog, TC_CLSBPF_STATS); 244 } 245 246 static int cls_bpf_init(struct tcf_proto *tp) 247 { 248 struct cls_bpf_head *head; 249 250 head = kzalloc(sizeof(*head), GFP_KERNEL); 251 if (head == NULL) 252 return -ENOBUFS; 253 254 INIT_LIST_HEAD_RCU(&head->plist); 255 idr_init(&head->handle_idr); 256 rcu_assign_pointer(tp->root, head); 257 258 return 0; 259 } 260 261 static void cls_bpf_free_parms(struct cls_bpf_prog *prog) 262 { 263 if (cls_bpf_is_ebpf(prog)) 264 bpf_prog_put(prog->filter); 265 else 266 bpf_prog_destroy(prog->filter); 267 268 kfree(prog->bpf_name); 269 kfree(prog->bpf_ops); 270 } 271 272 static void __cls_bpf_delete_prog(struct cls_bpf_prog *prog) 273 { 274 tcf_exts_destroy(&prog->exts); 275 tcf_exts_put_net(&prog->exts); 276 277 cls_bpf_free_parms(prog); 278 kfree(prog); 279 } 280 281 static void cls_bpf_delete_prog_work(struct work_struct *work) 282 { 283 struct cls_bpf_prog *prog = container_of(work, struct cls_bpf_prog, work); 284 285 rtnl_lock(); 286 __cls_bpf_delete_prog(prog); 287 rtnl_unlock(); 288 } 289 290 static void cls_bpf_delete_prog_rcu(struct rcu_head *rcu) 291 { 292 struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu); 293 294 INIT_WORK(&prog->work, cls_bpf_delete_prog_work); 295 tcf_queue_work(&prog->work); 296 } 297 298 static void __cls_bpf_delete(struct tcf_proto *tp, struct cls_bpf_prog *prog) 299 { 300 struct cls_bpf_head *head = rtnl_dereference(tp->root); 301 302 idr_remove_ext(&head->handle_idr, prog->handle); 303 cls_bpf_stop_offload(tp, prog); 304 list_del_rcu(&prog->link); 305 tcf_unbind_filter(tp, &prog->res); 306 if (tcf_exts_get_net(&prog->exts)) 307 call_rcu(&prog->rcu, cls_bpf_delete_prog_rcu); 308 else 309 __cls_bpf_delete_prog(prog); 310 } 311 312 static int cls_bpf_delete(struct tcf_proto *tp, void *arg, bool *last) 313 { 314 struct cls_bpf_head *head = rtnl_dereference(tp->root); 315 316 __cls_bpf_delete(tp, arg); 317 *last = list_empty(&head->plist); 318 return 0; 319 } 320 321 static void cls_bpf_destroy(struct tcf_proto *tp) 322 { 323 struct cls_bpf_head *head = rtnl_dereference(tp->root); 324 struct cls_bpf_prog *prog, *tmp; 325 326 list_for_each_entry_safe(prog, tmp, &head->plist, link) 327 __cls_bpf_delete(tp, prog); 328 329 idr_destroy(&head->handle_idr); 330 kfree_rcu(head, rcu); 331 } 332 333 static void *cls_bpf_get(struct tcf_proto *tp, u32 handle) 334 { 335 struct cls_bpf_head *head = rtnl_dereference(tp->root); 336 struct cls_bpf_prog *prog; 337 338 list_for_each_entry(prog, &head->plist, link) { 339 if (prog->handle == handle) 340 return prog; 341 } 342 343 return NULL; 344 } 345 346 static int cls_bpf_prog_from_ops(struct nlattr **tb, struct cls_bpf_prog *prog) 347 { 348 struct sock_filter *bpf_ops; 349 struct sock_fprog_kern fprog_tmp; 350 struct bpf_prog *fp; 351 u16 bpf_size, bpf_num_ops; 352 int ret; 353 354 bpf_num_ops = nla_get_u16(tb[TCA_BPF_OPS_LEN]); 355 if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0) 356 return -EINVAL; 357 358 bpf_size = bpf_num_ops * sizeof(*bpf_ops); 359 if (bpf_size != nla_len(tb[TCA_BPF_OPS])) 360 return -EINVAL; 361 362 bpf_ops = kzalloc(bpf_size, GFP_KERNEL); 363 if (bpf_ops == NULL) 364 return -ENOMEM; 365 366 memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size); 367 368 fprog_tmp.len = bpf_num_ops; 369 fprog_tmp.filter = bpf_ops; 370 371 ret = bpf_prog_create(&fp, &fprog_tmp); 372 if (ret < 0) { 373 kfree(bpf_ops); 374 return ret; 375 } 376 377 prog->bpf_ops = bpf_ops; 378 prog->bpf_num_ops = bpf_num_ops; 379 prog->bpf_name = NULL; 380 prog->filter = fp; 381 382 return 0; 383 } 384 385 static int cls_bpf_prog_from_efd(struct nlattr **tb, struct cls_bpf_prog *prog, 386 u32 gen_flags, const struct tcf_proto *tp) 387 { 388 struct bpf_prog *fp; 389 char *name = NULL; 390 bool skip_sw; 391 u32 bpf_fd; 392 393 bpf_fd = nla_get_u32(tb[TCA_BPF_FD]); 394 skip_sw = gen_flags & TCA_CLS_FLAGS_SKIP_SW; 395 396 fp = bpf_prog_get_type_dev(bpf_fd, BPF_PROG_TYPE_SCHED_CLS, skip_sw); 397 if (IS_ERR(fp)) 398 return PTR_ERR(fp); 399 400 if (tb[TCA_BPF_NAME]) { 401 name = nla_memdup(tb[TCA_BPF_NAME], GFP_KERNEL); 402 if (!name) { 403 bpf_prog_put(fp); 404 return -ENOMEM; 405 } 406 } 407 408 prog->bpf_ops = NULL; 409 prog->bpf_name = name; 410 prog->filter = fp; 411 412 if (fp->dst_needed && !(tp->q->flags & TCQ_F_INGRESS)) 413 netif_keep_dst(qdisc_dev(tp->q)); 414 415 return 0; 416 } 417 418 static int cls_bpf_set_parms(struct net *net, struct tcf_proto *tp, 419 struct cls_bpf_prog *prog, unsigned long base, 420 struct nlattr **tb, struct nlattr *est, bool ovr) 421 { 422 bool is_bpf, is_ebpf, have_exts = false; 423 u32 gen_flags = 0; 424 int ret; 425 426 is_bpf = tb[TCA_BPF_OPS_LEN] && tb[TCA_BPF_OPS]; 427 is_ebpf = tb[TCA_BPF_FD]; 428 if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) 429 return -EINVAL; 430 431 ret = tcf_exts_validate(net, tp, tb, est, &prog->exts, ovr); 432 if (ret < 0) 433 return ret; 434 435 if (tb[TCA_BPF_FLAGS]) { 436 u32 bpf_flags = nla_get_u32(tb[TCA_BPF_FLAGS]); 437 438 if (bpf_flags & ~TCA_BPF_FLAG_ACT_DIRECT) 439 return -EINVAL; 440 441 have_exts = bpf_flags & TCA_BPF_FLAG_ACT_DIRECT; 442 } 443 if (tb[TCA_BPF_FLAGS_GEN]) { 444 gen_flags = nla_get_u32(tb[TCA_BPF_FLAGS_GEN]); 445 if (gen_flags & ~CLS_BPF_SUPPORTED_GEN_FLAGS || 446 !tc_flags_valid(gen_flags)) 447 return -EINVAL; 448 } 449 450 prog->exts_integrated = have_exts; 451 prog->gen_flags = gen_flags; 452 453 ret = is_bpf ? cls_bpf_prog_from_ops(tb, prog) : 454 cls_bpf_prog_from_efd(tb, prog, gen_flags, tp); 455 if (ret < 0) 456 return ret; 457 458 if (tb[TCA_BPF_CLASSID]) { 459 prog->res.classid = nla_get_u32(tb[TCA_BPF_CLASSID]); 460 tcf_bind_filter(tp, &prog->res, base); 461 } 462 463 return 0; 464 } 465 466 static int cls_bpf_change(struct net *net, struct sk_buff *in_skb, 467 struct tcf_proto *tp, unsigned long base, 468 u32 handle, struct nlattr **tca, 469 void **arg, bool ovr) 470 { 471 struct cls_bpf_head *head = rtnl_dereference(tp->root); 472 struct cls_bpf_prog *oldprog = *arg; 473 struct nlattr *tb[TCA_BPF_MAX + 1]; 474 struct cls_bpf_prog *prog; 475 unsigned long idr_index; 476 int ret; 477 478 if (tca[TCA_OPTIONS] == NULL) 479 return -EINVAL; 480 481 ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy, 482 NULL); 483 if (ret < 0) 484 return ret; 485 486 prog = kzalloc(sizeof(*prog), GFP_KERNEL); 487 if (!prog) 488 return -ENOBUFS; 489 490 ret = tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE); 491 if (ret < 0) 492 goto errout; 493 494 if (oldprog) { 495 if (handle && oldprog->handle != handle) { 496 ret = -EINVAL; 497 goto errout; 498 } 499 } 500 501 if (handle == 0) { 502 ret = idr_alloc_ext(&head->handle_idr, prog, &idr_index, 503 1, 0x7FFFFFFF, GFP_KERNEL); 504 if (ret) 505 goto errout; 506 prog->handle = idr_index; 507 } else { 508 if (!oldprog) { 509 ret = idr_alloc_ext(&head->handle_idr, prog, &idr_index, 510 handle, handle + 1, GFP_KERNEL); 511 if (ret) 512 goto errout; 513 } 514 prog->handle = handle; 515 } 516 517 ret = cls_bpf_set_parms(net, tp, prog, base, tb, tca[TCA_RATE], ovr); 518 if (ret < 0) 519 goto errout_idr; 520 521 ret = cls_bpf_offload(tp, prog, oldprog); 522 if (ret) 523 goto errout_parms; 524 525 if (!tc_in_hw(prog->gen_flags)) 526 prog->gen_flags |= TCA_CLS_FLAGS_NOT_IN_HW; 527 528 if (oldprog) { 529 idr_replace_ext(&head->handle_idr, prog, handle); 530 list_replace_rcu(&oldprog->link, &prog->link); 531 tcf_unbind_filter(tp, &oldprog->res); 532 tcf_exts_get_net(&oldprog->exts); 533 call_rcu(&oldprog->rcu, cls_bpf_delete_prog_rcu); 534 } else { 535 list_add_rcu(&prog->link, &head->plist); 536 } 537 538 *arg = prog; 539 return 0; 540 541 errout_parms: 542 cls_bpf_free_parms(prog); 543 errout_idr: 544 if (!oldprog) 545 idr_remove_ext(&head->handle_idr, prog->handle); 546 errout: 547 tcf_exts_destroy(&prog->exts); 548 kfree(prog); 549 return ret; 550 } 551 552 static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog *prog, 553 struct sk_buff *skb) 554 { 555 struct nlattr *nla; 556 557 if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_num_ops)) 558 return -EMSGSIZE; 559 560 nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_num_ops * 561 sizeof(struct sock_filter)); 562 if (nla == NULL) 563 return -EMSGSIZE; 564 565 memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla)); 566 567 return 0; 568 } 569 570 static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog, 571 struct sk_buff *skb) 572 { 573 struct nlattr *nla; 574 575 if (prog->bpf_name && 576 nla_put_string(skb, TCA_BPF_NAME, prog->bpf_name)) 577 return -EMSGSIZE; 578 579 if (nla_put_u32(skb, TCA_BPF_ID, prog->filter->aux->id)) 580 return -EMSGSIZE; 581 582 nla = nla_reserve(skb, TCA_BPF_TAG, sizeof(prog->filter->tag)); 583 if (nla == NULL) 584 return -EMSGSIZE; 585 586 memcpy(nla_data(nla), prog->filter->tag, nla_len(nla)); 587 588 return 0; 589 } 590 591 static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, void *fh, 592 struct sk_buff *skb, struct tcmsg *tm) 593 { 594 struct cls_bpf_prog *prog = fh; 595 struct nlattr *nest; 596 u32 bpf_flags = 0; 597 int ret; 598 599 if (prog == NULL) 600 return skb->len; 601 602 tm->tcm_handle = prog->handle; 603 604 cls_bpf_offload_update_stats(tp, prog); 605 606 nest = nla_nest_start(skb, TCA_OPTIONS); 607 if (nest == NULL) 608 goto nla_put_failure; 609 610 if (prog->res.classid && 611 nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid)) 612 goto nla_put_failure; 613 614 if (cls_bpf_is_ebpf(prog)) 615 ret = cls_bpf_dump_ebpf_info(prog, skb); 616 else 617 ret = cls_bpf_dump_bpf_info(prog, skb); 618 if (ret) 619 goto nla_put_failure; 620 621 if (tcf_exts_dump(skb, &prog->exts) < 0) 622 goto nla_put_failure; 623 624 if (prog->exts_integrated) 625 bpf_flags |= TCA_BPF_FLAG_ACT_DIRECT; 626 if (bpf_flags && nla_put_u32(skb, TCA_BPF_FLAGS, bpf_flags)) 627 goto nla_put_failure; 628 if (prog->gen_flags && 629 nla_put_u32(skb, TCA_BPF_FLAGS_GEN, prog->gen_flags)) 630 goto nla_put_failure; 631 632 nla_nest_end(skb, nest); 633 634 if (tcf_exts_dump_stats(skb, &prog->exts) < 0) 635 goto nla_put_failure; 636 637 return skb->len; 638 639 nla_put_failure: 640 nla_nest_cancel(skb, nest); 641 return -1; 642 } 643 644 static void cls_bpf_bind_class(void *fh, u32 classid, unsigned long cl) 645 { 646 struct cls_bpf_prog *prog = fh; 647 648 if (prog && prog->res.classid == classid) 649 prog->res.class = cl; 650 } 651 652 static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg) 653 { 654 struct cls_bpf_head *head = rtnl_dereference(tp->root); 655 struct cls_bpf_prog *prog; 656 657 list_for_each_entry(prog, &head->plist, link) { 658 if (arg->count < arg->skip) 659 goto skip; 660 if (arg->fn(tp, prog, arg) < 0) { 661 arg->stop = 1; 662 break; 663 } 664 skip: 665 arg->count++; 666 } 667 } 668 669 static struct tcf_proto_ops cls_bpf_ops __read_mostly = { 670 .kind = "bpf", 671 .owner = THIS_MODULE, 672 .classify = cls_bpf_classify, 673 .init = cls_bpf_init, 674 .destroy = cls_bpf_destroy, 675 .get = cls_bpf_get, 676 .change = cls_bpf_change, 677 .delete = cls_bpf_delete, 678 .walk = cls_bpf_walk, 679 .dump = cls_bpf_dump, 680 .bind_class = cls_bpf_bind_class, 681 }; 682 683 static int __init cls_bpf_init_mod(void) 684 { 685 return register_tcf_proto_ops(&cls_bpf_ops); 686 } 687 688 static void __exit cls_bpf_exit_mod(void) 689 { 690 unregister_tcf_proto_ops(&cls_bpf_ops); 691 } 692 693 module_init(cls_bpf_init_mod); 694 module_exit(cls_bpf_exit_mod); 695