1 /* $NetBSD: if_tap.c,v 1.101 2017/10/30 16:01:19 ozaki-r Exp $ */ 2 3 /* 4 * Copyright (c) 2003, 2004, 2008, 2009 The NetBSD Foundation. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* 30 * tap(4) is a virtual Ethernet interface. It appears as a real Ethernet 31 * device to the system, but can also be accessed by userland through a 32 * character device interface, which allows reading and injecting frames. 33 */ 34 35 #include <sys/cdefs.h> 36 __KERNEL_RCSID(0, "$NetBSD: if_tap.c,v 1.101 2017/10/30 16:01:19 ozaki-r Exp $"); 37 38 #if defined(_KERNEL_OPT) 39 40 #include "opt_modular.h" 41 #include "opt_compat_netbsd.h" 42 #endif 43 44 #include <sys/param.h> 45 #include <sys/atomic.h> 46 #include <sys/conf.h> 47 #include <sys/cprng.h> 48 #include <sys/device.h> 49 #include <sys/file.h> 50 #include <sys/filedesc.h> 51 #include <sys/intr.h> 52 #include <sys/kauth.h> 53 #include <sys/kernel.h> 54 #include <sys/kmem.h> 55 #include <sys/module.h> 56 #include <sys/mutex.h> 57 #include <sys/poll.h> 58 #include <sys/proc.h> 59 #include <sys/select.h> 60 #include <sys/sockio.h> 61 #include <sys/stat.h> 62 #include <sys/sysctl.h> 63 #include <sys/systm.h> 64 65 #include <net/if.h> 66 #include <net/if_dl.h> 67 #include <net/if_ether.h> 68 #include <net/if_media.h> 69 #include <net/if_tap.h> 70 #include <net/bpf.h> 71 72 #include <compat/sys/sockio.h> 73 74 #include "ioconf.h" 75 76 /* 77 * sysctl node management 78 * 79 * It's not really possible to use a SYSCTL_SETUP block with 80 * current module implementation, so it is easier to just define 81 * our own function. 82 * 83 * The handler function is a "helper" in Andrew Brown's sysctl 84 * framework terminology. It is used as a gateway for sysctl 85 * requests over the nodes. 86 * 87 * tap_log allows the module to log creations of nodes and 88 * destroy them all at once using sysctl_teardown. 89 */ 90 static int tap_node; 91 static int tap_sysctl_handler(SYSCTLFN_PROTO); 92 static void sysctl_tap_setup(struct sysctllog **); 93 94 /* 95 * Since we're an Ethernet device, we need the 2 following 96 * components: a struct ethercom and a struct ifmedia 97 * since we don't attach a PHY to ourselves. 98 * We could emulate one, but there's no real point. 99 */ 100 101 struct tap_softc { 102 device_t sc_dev; 103 struct ifmedia sc_im; 104 struct ethercom sc_ec; 105 int sc_flags; 106 #define TAP_INUSE 0x00000001 /* tap device can only be opened once */ 107 #define TAP_ASYNCIO 0x00000002 /* user is using async I/O (SIGIO) on the device */ 108 #define TAP_NBIO 0x00000004 /* user wants calls to avoid blocking */ 109 #define TAP_GOING 0x00000008 /* interface is being destroyed */ 110 struct selinfo sc_rsel; 111 pid_t sc_pgid; /* For async. IO */ 112 kmutex_t sc_rdlock; 113 kmutex_t sc_kqlock; 114 void *sc_sih; 115 struct timespec sc_atime; 116 struct timespec sc_mtime; 117 struct timespec sc_btime; 118 }; 119 120 /* autoconf(9) glue */ 121 122 static int tap_match(device_t, cfdata_t, void *); 123 static void tap_attach(device_t, device_t, void *); 124 static int tap_detach(device_t, int); 125 126 CFATTACH_DECL_NEW(tap, sizeof(struct tap_softc), 127 tap_match, tap_attach, tap_detach, NULL); 128 extern struct cfdriver tap_cd; 129 130 /* Real device access routines */ 131 static int tap_dev_close(struct tap_softc *); 132 static int tap_dev_read(int, struct uio *, int); 133 static int tap_dev_write(int, struct uio *, int); 134 static int tap_dev_ioctl(int, u_long, void *, struct lwp *); 135 static int tap_dev_poll(int, int, struct lwp *); 136 static int tap_dev_kqfilter(int, struct knote *); 137 138 /* Fileops access routines */ 139 static int tap_fops_close(file_t *); 140 static int tap_fops_read(file_t *, off_t *, struct uio *, 141 kauth_cred_t, int); 142 static int tap_fops_write(file_t *, off_t *, struct uio *, 143 kauth_cred_t, int); 144 static int tap_fops_ioctl(file_t *, u_long, void *); 145 static int tap_fops_poll(file_t *, int); 146 static int tap_fops_stat(file_t *, struct stat *); 147 static int tap_fops_kqfilter(file_t *, struct knote *); 148 149 static const struct fileops tap_fileops = { 150 .fo_read = tap_fops_read, 151 .fo_write = tap_fops_write, 152 .fo_ioctl = tap_fops_ioctl, 153 .fo_fcntl = fnullop_fcntl, 154 .fo_poll = tap_fops_poll, 155 .fo_stat = tap_fops_stat, 156 .fo_close = tap_fops_close, 157 .fo_kqfilter = tap_fops_kqfilter, 158 .fo_restart = fnullop_restart, 159 }; 160 161 /* Helper for cloning open() */ 162 static int tap_dev_cloner(struct lwp *); 163 164 /* Character device routines */ 165 static int tap_cdev_open(dev_t, int, int, struct lwp *); 166 static int tap_cdev_close(dev_t, int, int, struct lwp *); 167 static int tap_cdev_read(dev_t, struct uio *, int); 168 static int tap_cdev_write(dev_t, struct uio *, int); 169 static int tap_cdev_ioctl(dev_t, u_long, void *, int, struct lwp *); 170 static int tap_cdev_poll(dev_t, int, struct lwp *); 171 static int tap_cdev_kqfilter(dev_t, struct knote *); 172 173 const struct cdevsw tap_cdevsw = { 174 .d_open = tap_cdev_open, 175 .d_close = tap_cdev_close, 176 .d_read = tap_cdev_read, 177 .d_write = tap_cdev_write, 178 .d_ioctl = tap_cdev_ioctl, 179 .d_stop = nostop, 180 .d_tty = notty, 181 .d_poll = tap_cdev_poll, 182 .d_mmap = nommap, 183 .d_kqfilter = tap_cdev_kqfilter, 184 .d_discard = nodiscard, 185 .d_flag = D_OTHER 186 }; 187 188 #define TAP_CLONER 0xfffff /* Maximal minor value */ 189 190 /* kqueue-related routines */ 191 static void tap_kqdetach(struct knote *); 192 static int tap_kqread(struct knote *, long); 193 194 /* 195 * Those are needed by the if_media interface. 196 */ 197 198 static int tap_mediachange(struct ifnet *); 199 static void tap_mediastatus(struct ifnet *, struct ifmediareq *); 200 201 /* 202 * Those are needed by the ifnet interface, and would typically be 203 * there for any network interface driver. 204 * Some other routines are optional: watchdog and drain. 205 */ 206 207 static void tap_start(struct ifnet *); 208 static void tap_stop(struct ifnet *, int); 209 static int tap_init(struct ifnet *); 210 static int tap_ioctl(struct ifnet *, u_long, void *); 211 212 /* Internal functions */ 213 static int tap_lifaddr(struct ifnet *, u_long, struct ifaliasreq *); 214 static void tap_softintr(void *); 215 216 /* 217 * tap is a clonable interface, although it is highly unrealistic for 218 * an Ethernet device. 219 * 220 * Here are the bits needed for a clonable interface. 221 */ 222 static int tap_clone_create(struct if_clone *, int); 223 static int tap_clone_destroy(struct ifnet *); 224 225 struct if_clone tap_cloners = IF_CLONE_INITIALIZER("tap", 226 tap_clone_create, 227 tap_clone_destroy); 228 229 /* Helper functions shared by the two cloning code paths */ 230 static struct tap_softc * tap_clone_creator(int); 231 int tap_clone_destroyer(device_t); 232 233 static struct sysctllog *tap_sysctl_clog; 234 235 #ifdef _MODULE 236 devmajor_t tap_bmajor = -1, tap_cmajor = -1; 237 #endif 238 239 static u_int tap_count; 240 241 void 242 tapattach(int n) 243 { 244 245 /* 246 * Nothing to do here, initialization is handled by the 247 * module initialization code in tapinit() below). 248 */ 249 } 250 251 static void 252 tapinit(void) 253 { 254 int error = config_cfattach_attach(tap_cd.cd_name, &tap_ca); 255 if (error) { 256 aprint_error("%s: unable to register cfattach\n", 257 tap_cd.cd_name); 258 (void)config_cfdriver_detach(&tap_cd); 259 return; 260 } 261 262 if_clone_attach(&tap_cloners); 263 sysctl_tap_setup(&tap_sysctl_clog); 264 #ifdef _MODULE 265 devsw_attach("tap", NULL, &tap_bmajor, &tap_cdevsw, &tap_cmajor); 266 #endif 267 } 268 269 static int 270 tapdetach(void) 271 { 272 int error = 0; 273 274 if (tap_count != 0) 275 return EBUSY; 276 277 #ifdef _MODULE 278 if (error == 0) 279 error = devsw_detach(NULL, &tap_cdevsw); 280 #endif 281 if (error == 0) 282 sysctl_teardown(&tap_sysctl_clog); 283 if (error == 0) 284 if_clone_detach(&tap_cloners); 285 286 if (error == 0) 287 error = config_cfattach_detach(tap_cd.cd_name, &tap_ca); 288 289 return error; 290 } 291 292 /* Pretty much useless for a pseudo-device */ 293 static int 294 tap_match(device_t parent, cfdata_t cfdata, void *arg) 295 { 296 297 return 1; 298 } 299 300 void 301 tap_attach(device_t parent, device_t self, void *aux) 302 { 303 struct tap_softc *sc = device_private(self); 304 struct ifnet *ifp; 305 const struct sysctlnode *node; 306 int error; 307 uint8_t enaddr[ETHER_ADDR_LEN] = 308 { 0xf2, 0x0b, 0xa4, 0xff, 0xff, 0xff }; 309 char enaddrstr[3 * ETHER_ADDR_LEN]; 310 311 sc->sc_dev = self; 312 sc->sc_sih = NULL; 313 getnanotime(&sc->sc_btime); 314 sc->sc_atime = sc->sc_mtime = sc->sc_btime; 315 sc->sc_flags = 0; 316 selinit(&sc->sc_rsel); 317 318 /* 319 * Initialize the two locks for the device. 320 * 321 * We need a lock here because even though the tap device can be 322 * opened only once, the file descriptor might be passed to another 323 * process, say a fork(2)ed child. 324 * 325 * The Giant saves us from most of the hassle, but since the read 326 * operation can sleep, we don't want two processes to wake up at 327 * the same moment and both try and dequeue a single packet. 328 * 329 * The queue for event listeners (used by kqueue(9), see below) has 330 * to be protected too, so use a spin lock. 331 */ 332 mutex_init(&sc->sc_rdlock, MUTEX_DEFAULT, IPL_NONE); 333 mutex_init(&sc->sc_kqlock, MUTEX_DEFAULT, IPL_VM); 334 335 if (!pmf_device_register(self, NULL, NULL)) 336 aprint_error_dev(self, "couldn't establish power handler\n"); 337 338 /* 339 * In order to obtain unique initial Ethernet address on a host, 340 * do some randomisation. It's not meant for anything but avoiding 341 * hard-coding an address. 342 */ 343 cprng_fast(&enaddr[3], 3); 344 345 aprint_verbose_dev(self, "Ethernet address %s\n", 346 ether_snprintf(enaddrstr, sizeof(enaddrstr), enaddr)); 347 348 /* 349 * Why 1000baseT? Why not? You can add more. 350 * 351 * Note that there are 3 steps: init, one or several additions to 352 * list of supported media, and in the end, the selection of one 353 * of them. 354 */ 355 ifmedia_init(&sc->sc_im, 0, tap_mediachange, tap_mediastatus); 356 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_1000_T, 0, NULL); 357 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_1000_T|IFM_FDX, 0, NULL); 358 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_100_TX, 0, NULL); 359 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_100_TX|IFM_FDX, 0, NULL); 360 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_10_T, 0, NULL); 361 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_10_T|IFM_FDX, 0, NULL); 362 ifmedia_add(&sc->sc_im, IFM_ETHER|IFM_AUTO, 0, NULL); 363 ifmedia_set(&sc->sc_im, IFM_ETHER|IFM_AUTO); 364 365 /* 366 * One should note that an interface must do multicast in order 367 * to support IPv6. 368 */ 369 ifp = &sc->sc_ec.ec_if; 370 strcpy(ifp->if_xname, device_xname(self)); 371 ifp->if_softc = sc; 372 ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST; 373 ifp->if_extflags = IFEF_NO_LINK_STATE_CHANGE; 374 ifp->if_ioctl = tap_ioctl; 375 ifp->if_start = tap_start; 376 ifp->if_stop = tap_stop; 377 ifp->if_init = tap_init; 378 IFQ_SET_READY(&ifp->if_snd); 379 380 sc->sc_ec.ec_capabilities = ETHERCAP_VLAN_MTU | ETHERCAP_JUMBO_MTU; 381 382 /* Those steps are mandatory for an Ethernet driver. */ 383 error = if_initialize(ifp); 384 if (error != 0) { 385 aprint_error_dev(self, "if_initialize failed(%d)\n", error); 386 ifmedia_removeall(&sc->sc_im); 387 pmf_device_deregister(self); 388 mutex_destroy(&sc->sc_rdlock); 389 mutex_destroy(&sc->sc_kqlock); 390 seldestroy(&sc->sc_rsel); 391 392 return; /* Error */ 393 } 394 ether_ifattach(ifp, enaddr); 395 if_register(ifp); 396 397 /* 398 * Add a sysctl node for that interface. 399 * 400 * The pointer transmitted is not a string, but instead a pointer to 401 * the softc structure, which we can use to build the string value on 402 * the fly in the helper function of the node. See the comments for 403 * tap_sysctl_handler for details. 404 * 405 * Usually sysctl_createv is called with CTL_CREATE as the before-last 406 * component. However, we can allocate a number ourselves, as we are 407 * the only consumer of the net.link.<iface> node. In this case, the 408 * unit number is conveniently used to number the node. CTL_CREATE 409 * would just work, too. 410 */ 411 if ((error = sysctl_createv(NULL, 0, NULL, 412 &node, CTLFLAG_READWRITE, 413 CTLTYPE_STRING, device_xname(self), NULL, 414 tap_sysctl_handler, 0, (void *)sc, 18, 415 CTL_NET, AF_LINK, tap_node, device_unit(sc->sc_dev), 416 CTL_EOL)) != 0) 417 aprint_error_dev(self, 418 "sysctl_createv returned %d, ignoring\n", error); 419 } 420 421 /* 422 * When detaching, we do the inverse of what is done in the attach 423 * routine, in reversed order. 424 */ 425 static int 426 tap_detach(device_t self, int flags) 427 { 428 struct tap_softc *sc = device_private(self); 429 struct ifnet *ifp = &sc->sc_ec.ec_if; 430 int error; 431 int s; 432 433 sc->sc_flags |= TAP_GOING; 434 s = splnet(); 435 tap_stop(ifp, 1); 436 if_down(ifp); 437 splx(s); 438 439 if (sc->sc_sih != NULL) { 440 softint_disestablish(sc->sc_sih); 441 sc->sc_sih = NULL; 442 } 443 444 /* 445 * Destroying a single leaf is a very straightforward operation using 446 * sysctl_destroyv. One should be sure to always end the path with 447 * CTL_EOL. 448 */ 449 if ((error = sysctl_destroyv(NULL, CTL_NET, AF_LINK, tap_node, 450 device_unit(sc->sc_dev), CTL_EOL)) != 0) 451 aprint_error_dev(self, 452 "sysctl_destroyv returned %d, ignoring\n", error); 453 ether_ifdetach(ifp); 454 if_detach(ifp); 455 ifmedia_removeall(&sc->sc_im); 456 seldestroy(&sc->sc_rsel); 457 mutex_destroy(&sc->sc_rdlock); 458 mutex_destroy(&sc->sc_kqlock); 459 460 pmf_device_deregister(self); 461 462 return 0; 463 } 464 465 /* 466 * This function is called by the ifmedia layer to notify the driver 467 * that the user requested a media change. A real driver would 468 * reconfigure the hardware. 469 */ 470 static int 471 tap_mediachange(struct ifnet *ifp) 472 { 473 return 0; 474 } 475 476 /* 477 * Here the user asks for the currently used media. 478 */ 479 static void 480 tap_mediastatus(struct ifnet *ifp, struct ifmediareq *imr) 481 { 482 struct tap_softc *sc = (struct tap_softc *)ifp->if_softc; 483 imr->ifm_active = sc->sc_im.ifm_cur->ifm_media; 484 } 485 486 /* 487 * This is the function where we SEND packets. 488 * 489 * There is no 'receive' equivalent. A typical driver will get 490 * interrupts from the hardware, and from there will inject new packets 491 * into the network stack. 492 * 493 * Once handled, a packet must be freed. A real driver might not be able 494 * to fit all the pending packets into the hardware, and is allowed to 495 * return before having sent all the packets. It should then use the 496 * if_flags flag IFF_OACTIVE to notify the upper layer. 497 * 498 * There are also other flags one should check, such as IFF_PAUSE. 499 * 500 * It is our duty to make packets available to BPF listeners. 501 * 502 * You should be aware that this function is called by the Ethernet layer 503 * at splnet(). 504 * 505 * When the device is opened, we have to pass the packet(s) to the 506 * userland. For that we stay in OACTIVE mode while the userland gets 507 * the packets, and we send a signal to the processes waiting to read. 508 * 509 * wakeup(sc) is the counterpart to the tsleep call in 510 * tap_dev_read, while selnotify() is used for kevent(2) and 511 * poll(2) (which includes select(2)) listeners. 512 */ 513 static void 514 tap_start(struct ifnet *ifp) 515 { 516 struct tap_softc *sc = (struct tap_softc *)ifp->if_softc; 517 struct mbuf *m0; 518 519 if ((sc->sc_flags & TAP_INUSE) == 0) { 520 /* Simply drop packets */ 521 for(;;) { 522 IFQ_DEQUEUE(&ifp->if_snd, m0); 523 if (m0 == NULL) 524 return; 525 526 ifp->if_opackets++; 527 bpf_mtap(ifp, m0); 528 529 m_freem(m0); 530 } 531 } else if (!IFQ_IS_EMPTY(&ifp->if_snd)) { 532 ifp->if_flags |= IFF_OACTIVE; 533 wakeup(sc); 534 selnotify(&sc->sc_rsel, 0, 1); 535 if (sc->sc_flags & TAP_ASYNCIO) 536 softint_schedule(sc->sc_sih); 537 } 538 } 539 540 static void 541 tap_softintr(void *cookie) 542 { 543 struct tap_softc *sc; 544 struct ifnet *ifp; 545 int a, b; 546 547 sc = cookie; 548 549 if (sc->sc_flags & TAP_ASYNCIO) { 550 ifp = &sc->sc_ec.ec_if; 551 if (ifp->if_flags & IFF_RUNNING) { 552 a = POLL_IN; 553 b = POLLIN|POLLRDNORM; 554 } else { 555 a = POLL_HUP; 556 b = 0; 557 } 558 fownsignal(sc->sc_pgid, SIGIO, a, b, NULL); 559 } 560 } 561 562 /* 563 * A typical driver will only contain the following handlers for 564 * ioctl calls, except SIOCSIFPHYADDR. 565 * The latter is a hack I used to set the Ethernet address of the 566 * faked device. 567 * 568 * Note that both ifmedia_ioctl() and ether_ioctl() have to be 569 * called under splnet(). 570 */ 571 static int 572 tap_ioctl(struct ifnet *ifp, u_long cmd, void *data) 573 { 574 struct tap_softc *sc = (struct tap_softc *)ifp->if_softc; 575 struct ifreq *ifr = (struct ifreq *)data; 576 int s, error; 577 578 s = splnet(); 579 580 switch (cmd) { 581 #ifdef OSIOCSIFMEDIA 582 case OSIOCSIFMEDIA: 583 #endif 584 case SIOCSIFMEDIA: 585 case SIOCGIFMEDIA: 586 error = ifmedia_ioctl(ifp, ifr, &sc->sc_im, cmd); 587 break; 588 case SIOCSIFPHYADDR: 589 error = tap_lifaddr(ifp, cmd, (struct ifaliasreq *)data); 590 break; 591 default: 592 error = ether_ioctl(ifp, cmd, data); 593 if (error == ENETRESET) 594 error = 0; 595 break; 596 } 597 598 splx(s); 599 600 return error; 601 } 602 603 /* 604 * Helper function to set Ethernet address. This has been replaced by 605 * the generic SIOCALIFADDR ioctl on a PF_LINK socket. 606 */ 607 static int 608 tap_lifaddr(struct ifnet *ifp, u_long cmd, struct ifaliasreq *ifra) 609 { 610 const struct sockaddr *sa = &ifra->ifra_addr; 611 612 if (sa->sa_family != AF_LINK) 613 return EINVAL; 614 615 if_set_sadl(ifp, sa->sa_data, ETHER_ADDR_LEN, false); 616 617 return 0; 618 } 619 620 /* 621 * _init() would typically be called when an interface goes up, 622 * meaning it should configure itself into the state in which it 623 * can send packets. 624 */ 625 static int 626 tap_init(struct ifnet *ifp) 627 { 628 ifp->if_flags |= IFF_RUNNING; 629 630 tap_start(ifp); 631 632 return 0; 633 } 634 635 /* 636 * _stop() is called when an interface goes down. It is our 637 * responsability to validate that state by clearing the 638 * IFF_RUNNING flag. 639 * 640 * We have to wake up all the sleeping processes to have the pending 641 * read requests cancelled. 642 */ 643 static void 644 tap_stop(struct ifnet *ifp, int disable) 645 { 646 struct tap_softc *sc = (struct tap_softc *)ifp->if_softc; 647 648 ifp->if_flags &= ~IFF_RUNNING; 649 wakeup(sc); 650 selnotify(&sc->sc_rsel, 0, 1); 651 if (sc->sc_flags & TAP_ASYNCIO) 652 softint_schedule(sc->sc_sih); 653 } 654 655 /* 656 * The 'create' command of ifconfig can be used to create 657 * any numbered instance of a given device. Thus we have to 658 * make sure we have enough room in cd_devs to create the 659 * user-specified instance. config_attach_pseudo will do this 660 * for us. 661 */ 662 static int 663 tap_clone_create(struct if_clone *ifc, int unit) 664 { 665 if (tap_clone_creator(unit) == NULL) { 666 aprint_error("%s%d: unable to attach an instance\n", 667 tap_cd.cd_name, unit); 668 return ENXIO; 669 } 670 atomic_inc_uint(&tap_count); 671 return 0; 672 } 673 674 /* 675 * tap(4) can be cloned by two ways: 676 * using 'ifconfig tap0 create', which will use the network 677 * interface cloning API, and call tap_clone_create above. 678 * opening the cloning device node, whose minor number is TAP_CLONER. 679 * See below for an explanation on how this part work. 680 */ 681 static struct tap_softc * 682 tap_clone_creator(int unit) 683 { 684 cfdata_t cf; 685 686 cf = kmem_alloc(sizeof(*cf), KM_SLEEP); 687 cf->cf_name = tap_cd.cd_name; 688 cf->cf_atname = tap_ca.ca_name; 689 if (unit == -1) { 690 /* let autoconf find the first free one */ 691 cf->cf_unit = 0; 692 cf->cf_fstate = FSTATE_STAR; 693 } else { 694 cf->cf_unit = unit; 695 cf->cf_fstate = FSTATE_NOTFOUND; 696 } 697 698 return device_private(config_attach_pseudo(cf)); 699 } 700 701 /* 702 * The clean design of if_clone and autoconf(9) makes that part 703 * really straightforward. The second argument of config_detach 704 * means neither QUIET nor FORCED. 705 */ 706 static int 707 tap_clone_destroy(struct ifnet *ifp) 708 { 709 struct tap_softc *sc = ifp->if_softc; 710 int error = tap_clone_destroyer(sc->sc_dev); 711 712 if (error == 0) 713 atomic_dec_uint(&tap_count); 714 return error; 715 } 716 717 int 718 tap_clone_destroyer(device_t dev) 719 { 720 cfdata_t cf = device_cfdata(dev); 721 int error; 722 723 if ((error = config_detach(dev, 0)) != 0) 724 aprint_error_dev(dev, "unable to detach instance\n"); 725 kmem_free(cf, sizeof(*cf)); 726 727 return error; 728 } 729 730 /* 731 * tap(4) is a bit of an hybrid device. It can be used in two different 732 * ways: 733 * 1. ifconfig tapN create, then use /dev/tapN to read/write off it. 734 * 2. open /dev/tap, get a new interface created and read/write off it. 735 * That interface is destroyed when the process that had it created exits. 736 * 737 * The first way is managed by the cdevsw structure, and you access interfaces 738 * through a (major, minor) mapping: tap4 is obtained by the minor number 739 * 4. The entry points for the cdevsw interface are prefixed by tap_cdev_. 740 * 741 * The second way is the so-called "cloning" device. It's a special minor 742 * number (chosen as the maximal number, to allow as much tap devices as 743 * possible). The user first opens the cloner (e.g., /dev/tap), and that 744 * call ends in tap_cdev_open. The actual place where it is handled is 745 * tap_dev_cloner. 746 * 747 * An tap device cannot be opened more than once at a time, so the cdevsw 748 * part of open() does nothing but noting that the interface is being used and 749 * hence ready to actually handle packets. 750 */ 751 752 static int 753 tap_cdev_open(dev_t dev, int flags, int fmt, struct lwp *l) 754 { 755 struct tap_softc *sc; 756 757 if (minor(dev) == TAP_CLONER) 758 return tap_dev_cloner(l); 759 760 sc = device_lookup_private(&tap_cd, minor(dev)); 761 if (sc == NULL) 762 return ENXIO; 763 764 /* The device can only be opened once */ 765 if (sc->sc_flags & TAP_INUSE) 766 return EBUSY; 767 sc->sc_flags |= TAP_INUSE; 768 return 0; 769 } 770 771 /* 772 * There are several kinds of cloning devices, and the most simple is the one 773 * tap(4) uses. What it does is change the file descriptor with a new one, 774 * with its own fileops structure (which maps to the various read, write, 775 * ioctl functions). It starts allocating a new file descriptor with falloc, 776 * then actually creates the new tap devices. 777 * 778 * Once those two steps are successful, we can re-wire the existing file 779 * descriptor to its new self. This is done with fdclone(): it fills the fp 780 * structure as needed (notably f_devunit gets filled with the fifth parameter 781 * passed, the unit of the tap device which will allows us identifying the 782 * device later), and returns EMOVEFD. 783 * 784 * That magic value is interpreted by sys_open() which then replaces the 785 * current file descriptor by the new one (through a magic member of struct 786 * lwp, l_dupfd). 787 * 788 * The tap device is flagged as being busy since it otherwise could be 789 * externally accessed through the corresponding device node with the cdevsw 790 * interface. 791 */ 792 793 static int 794 tap_dev_cloner(struct lwp *l) 795 { 796 struct tap_softc *sc; 797 file_t *fp; 798 int error, fd; 799 800 if ((error = fd_allocfile(&fp, &fd)) != 0) 801 return error; 802 803 if ((sc = tap_clone_creator(-1)) == NULL) { 804 fd_abort(curproc, fp, fd); 805 return ENXIO; 806 } 807 808 sc->sc_flags |= TAP_INUSE; 809 810 return fd_clone(fp, fd, FREAD|FWRITE, &tap_fileops, 811 (void *)(intptr_t)device_unit(sc->sc_dev)); 812 } 813 814 /* 815 * While all other operations (read, write, ioctl, poll and kqfilter) are 816 * really the same whether we are in cdevsw or fileops mode, the close() 817 * function is slightly different in the two cases. 818 * 819 * As for the other, the core of it is shared in tap_dev_close. What 820 * it does is sufficient for the cdevsw interface, but the cloning interface 821 * needs another thing: the interface is destroyed when the processes that 822 * created it closes it. 823 */ 824 static int 825 tap_cdev_close(dev_t dev, int flags, int fmt, 826 struct lwp *l) 827 { 828 struct tap_softc *sc = 829 device_lookup_private(&tap_cd, minor(dev)); 830 831 if (sc == NULL) 832 return ENXIO; 833 834 return tap_dev_close(sc); 835 } 836 837 /* 838 * It might happen that the administrator used ifconfig to externally destroy 839 * the interface. In that case, tap_fops_close will be called while 840 * tap_detach is already happening. If we called it again from here, we 841 * would dead lock. TAP_GOING ensures that this situation doesn't happen. 842 */ 843 static int 844 tap_fops_close(file_t *fp) 845 { 846 int unit = fp->f_devunit; 847 struct tap_softc *sc; 848 int error; 849 850 sc = device_lookup_private(&tap_cd, unit); 851 if (sc == NULL) 852 return ENXIO; 853 854 /* tap_dev_close currently always succeeds, but it might not 855 * always be the case. */ 856 KERNEL_LOCK(1, NULL); 857 if ((error = tap_dev_close(sc)) != 0) { 858 KERNEL_UNLOCK_ONE(NULL); 859 return error; 860 } 861 862 /* Destroy the device now that it is no longer useful, 863 * unless it's already being destroyed. */ 864 if ((sc->sc_flags & TAP_GOING) != 0) { 865 KERNEL_UNLOCK_ONE(NULL); 866 return 0; 867 } 868 869 error = tap_clone_destroyer(sc->sc_dev); 870 KERNEL_UNLOCK_ONE(NULL); 871 return error; 872 } 873 874 static int 875 tap_dev_close(struct tap_softc *sc) 876 { 877 struct ifnet *ifp; 878 int s; 879 880 s = splnet(); 881 /* Let tap_start handle packets again */ 882 ifp = &sc->sc_ec.ec_if; 883 ifp->if_flags &= ~IFF_OACTIVE; 884 885 /* Purge output queue */ 886 if (!(IFQ_IS_EMPTY(&ifp->if_snd))) { 887 struct mbuf *m; 888 889 for (;;) { 890 IFQ_DEQUEUE(&ifp->if_snd, m); 891 if (m == NULL) 892 break; 893 894 ifp->if_opackets++; 895 bpf_mtap(ifp, m); 896 m_freem(m); 897 } 898 } 899 splx(s); 900 901 if (sc->sc_sih != NULL) { 902 softint_disestablish(sc->sc_sih); 903 sc->sc_sih = NULL; 904 } 905 sc->sc_flags &= ~(TAP_INUSE | TAP_ASYNCIO); 906 907 return 0; 908 } 909 910 static int 911 tap_cdev_read(dev_t dev, struct uio *uio, int flags) 912 { 913 return tap_dev_read(minor(dev), uio, flags); 914 } 915 916 static int 917 tap_fops_read(file_t *fp, off_t *offp, struct uio *uio, 918 kauth_cred_t cred, int flags) 919 { 920 int error; 921 922 KERNEL_LOCK(1, NULL); 923 error = tap_dev_read(fp->f_devunit, uio, flags); 924 KERNEL_UNLOCK_ONE(NULL); 925 return error; 926 } 927 928 static int 929 tap_dev_read(int unit, struct uio *uio, int flags) 930 { 931 struct tap_softc *sc = device_lookup_private(&tap_cd, unit); 932 struct ifnet *ifp; 933 struct mbuf *m, *n; 934 int error = 0, s; 935 936 if (sc == NULL) 937 return ENXIO; 938 939 getnanotime(&sc->sc_atime); 940 941 ifp = &sc->sc_ec.ec_if; 942 if ((ifp->if_flags & IFF_UP) == 0) 943 return EHOSTDOWN; 944 945 /* 946 * In the TAP_NBIO case, we have to make sure we won't be sleeping 947 */ 948 if ((sc->sc_flags & TAP_NBIO) != 0) { 949 if (!mutex_tryenter(&sc->sc_rdlock)) 950 return EWOULDBLOCK; 951 } else { 952 mutex_enter(&sc->sc_rdlock); 953 } 954 955 s = splnet(); 956 if (IFQ_IS_EMPTY(&ifp->if_snd)) { 957 ifp->if_flags &= ~IFF_OACTIVE; 958 /* 959 * We must release the lock before sleeping, and re-acquire it 960 * after. 961 */ 962 mutex_exit(&sc->sc_rdlock); 963 if (sc->sc_flags & TAP_NBIO) 964 error = EWOULDBLOCK; 965 else 966 error = tsleep(sc, PSOCK|PCATCH, "tap", 0); 967 splx(s); 968 969 if (error != 0) 970 return error; 971 /* The device might have been downed */ 972 if ((ifp->if_flags & IFF_UP) == 0) 973 return EHOSTDOWN; 974 if ((sc->sc_flags & TAP_NBIO)) { 975 if (!mutex_tryenter(&sc->sc_rdlock)) 976 return EWOULDBLOCK; 977 } else { 978 mutex_enter(&sc->sc_rdlock); 979 } 980 s = splnet(); 981 } 982 983 IFQ_DEQUEUE(&ifp->if_snd, m); 984 ifp->if_flags &= ~IFF_OACTIVE; 985 splx(s); 986 if (m == NULL) { 987 error = 0; 988 goto out; 989 } 990 991 ifp->if_opackets++; 992 bpf_mtap(ifp, m); 993 994 /* 995 * One read is one packet. 996 */ 997 do { 998 error = uiomove(mtod(m, void *), 999 min(m->m_len, uio->uio_resid), uio); 1000 m = n = m_free(m); 1001 } while (m != NULL && uio->uio_resid > 0 && error == 0); 1002 1003 if (m != NULL) 1004 m_freem(m); 1005 1006 out: 1007 mutex_exit(&sc->sc_rdlock); 1008 return error; 1009 } 1010 1011 static int 1012 tap_fops_stat(file_t *fp, struct stat *st) 1013 { 1014 int error = 0; 1015 struct tap_softc *sc; 1016 int unit = fp->f_devunit; 1017 1018 (void)memset(st, 0, sizeof(*st)); 1019 1020 KERNEL_LOCK(1, NULL); 1021 sc = device_lookup_private(&tap_cd, unit); 1022 if (sc == NULL) { 1023 error = ENXIO; 1024 goto out; 1025 } 1026 1027 st->st_dev = makedev(cdevsw_lookup_major(&tap_cdevsw), unit); 1028 st->st_atimespec = sc->sc_atime; 1029 st->st_mtimespec = sc->sc_mtime; 1030 st->st_ctimespec = st->st_birthtimespec = sc->sc_btime; 1031 st->st_uid = kauth_cred_geteuid(fp->f_cred); 1032 st->st_gid = kauth_cred_getegid(fp->f_cred); 1033 out: 1034 KERNEL_UNLOCK_ONE(NULL); 1035 return error; 1036 } 1037 1038 static int 1039 tap_cdev_write(dev_t dev, struct uio *uio, int flags) 1040 { 1041 return tap_dev_write(minor(dev), uio, flags); 1042 } 1043 1044 static int 1045 tap_fops_write(file_t *fp, off_t *offp, struct uio *uio, 1046 kauth_cred_t cred, int flags) 1047 { 1048 int error; 1049 1050 KERNEL_LOCK(1, NULL); 1051 error = tap_dev_write(fp->f_devunit, uio, flags); 1052 KERNEL_UNLOCK_ONE(NULL); 1053 return error; 1054 } 1055 1056 static int 1057 tap_dev_write(int unit, struct uio *uio, int flags) 1058 { 1059 struct tap_softc *sc = 1060 device_lookup_private(&tap_cd, unit); 1061 struct ifnet *ifp; 1062 struct mbuf *m, **mp; 1063 int error = 0; 1064 int s; 1065 1066 if (sc == NULL) 1067 return ENXIO; 1068 1069 getnanotime(&sc->sc_mtime); 1070 ifp = &sc->sc_ec.ec_if; 1071 1072 /* One write, one packet, that's the rule */ 1073 MGETHDR(m, M_DONTWAIT, MT_DATA); 1074 if (m == NULL) { 1075 ifp->if_ierrors++; 1076 return ENOBUFS; 1077 } 1078 m->m_pkthdr.len = uio->uio_resid; 1079 1080 mp = &m; 1081 while (error == 0 && uio->uio_resid > 0) { 1082 if (*mp != m) { 1083 MGET(*mp, M_DONTWAIT, MT_DATA); 1084 if (*mp == NULL) { 1085 error = ENOBUFS; 1086 break; 1087 } 1088 } 1089 (*mp)->m_len = min(MHLEN, uio->uio_resid); 1090 error = uiomove(mtod(*mp, void *), (*mp)->m_len, uio); 1091 mp = &(*mp)->m_next; 1092 } 1093 if (error) { 1094 ifp->if_ierrors++; 1095 m_freem(m); 1096 return error; 1097 } 1098 1099 m_set_rcvif(m, ifp); 1100 1101 s = splnet(); 1102 if_input(ifp, m); 1103 splx(s); 1104 1105 return 0; 1106 } 1107 1108 static int 1109 tap_cdev_ioctl(dev_t dev, u_long cmd, void *data, int flags, 1110 struct lwp *l) 1111 { 1112 return tap_dev_ioctl(minor(dev), cmd, data, l); 1113 } 1114 1115 static int 1116 tap_fops_ioctl(file_t *fp, u_long cmd, void *data) 1117 { 1118 return tap_dev_ioctl(fp->f_devunit, cmd, data, curlwp); 1119 } 1120 1121 static int 1122 tap_dev_ioctl(int unit, u_long cmd, void *data, struct lwp *l) 1123 { 1124 struct tap_softc *sc = device_lookup_private(&tap_cd, unit); 1125 1126 if (sc == NULL) 1127 return ENXIO; 1128 1129 switch (cmd) { 1130 case FIONREAD: 1131 { 1132 struct ifnet *ifp = &sc->sc_ec.ec_if; 1133 struct mbuf *m; 1134 int s; 1135 1136 s = splnet(); 1137 IFQ_POLL(&ifp->if_snd, m); 1138 1139 if (m == NULL) 1140 *(int *)data = 0; 1141 else 1142 *(int *)data = m->m_pkthdr.len; 1143 splx(s); 1144 return 0; 1145 } 1146 case TIOCSPGRP: 1147 case FIOSETOWN: 1148 return fsetown(&sc->sc_pgid, cmd, data); 1149 case TIOCGPGRP: 1150 case FIOGETOWN: 1151 return fgetown(sc->sc_pgid, cmd, data); 1152 case FIOASYNC: 1153 if (*(int *)data) { 1154 if (sc->sc_sih == NULL) { 1155 sc->sc_sih = softint_establish(SOFTINT_CLOCK, 1156 tap_softintr, sc); 1157 if (sc->sc_sih == NULL) 1158 return EBUSY; /* XXX */ 1159 } 1160 sc->sc_flags |= TAP_ASYNCIO; 1161 } else { 1162 sc->sc_flags &= ~TAP_ASYNCIO; 1163 if (sc->sc_sih != NULL) { 1164 softint_disestablish(sc->sc_sih); 1165 sc->sc_sih = NULL; 1166 } 1167 } 1168 return 0; 1169 case FIONBIO: 1170 if (*(int *)data) 1171 sc->sc_flags |= TAP_NBIO; 1172 else 1173 sc->sc_flags &= ~TAP_NBIO; 1174 return 0; 1175 #ifdef OTAPGIFNAME 1176 case OTAPGIFNAME: 1177 #endif 1178 case TAPGIFNAME: 1179 { 1180 struct ifreq *ifr = (struct ifreq *)data; 1181 struct ifnet *ifp = &sc->sc_ec.ec_if; 1182 1183 strlcpy(ifr->ifr_name, ifp->if_xname, IFNAMSIZ); 1184 return 0; 1185 } 1186 default: 1187 return ENOTTY; 1188 } 1189 } 1190 1191 static int 1192 tap_cdev_poll(dev_t dev, int events, struct lwp *l) 1193 { 1194 return tap_dev_poll(minor(dev), events, l); 1195 } 1196 1197 static int 1198 tap_fops_poll(file_t *fp, int events) 1199 { 1200 return tap_dev_poll(fp->f_devunit, events, curlwp); 1201 } 1202 1203 static int 1204 tap_dev_poll(int unit, int events, struct lwp *l) 1205 { 1206 struct tap_softc *sc = 1207 device_lookup_private(&tap_cd, unit); 1208 int revents = 0; 1209 1210 if (sc == NULL) 1211 return POLLERR; 1212 1213 if (events & (POLLIN|POLLRDNORM)) { 1214 struct ifnet *ifp = &sc->sc_ec.ec_if; 1215 struct mbuf *m; 1216 int s; 1217 1218 s = splnet(); 1219 IFQ_POLL(&ifp->if_snd, m); 1220 1221 if (m != NULL) 1222 revents |= events & (POLLIN|POLLRDNORM); 1223 else { 1224 mutex_spin_enter(&sc->sc_kqlock); 1225 selrecord(l, &sc->sc_rsel); 1226 mutex_spin_exit(&sc->sc_kqlock); 1227 } 1228 splx(s); 1229 } 1230 revents |= events & (POLLOUT|POLLWRNORM); 1231 1232 return revents; 1233 } 1234 1235 static struct filterops tap_read_filterops = { 1, NULL, tap_kqdetach, 1236 tap_kqread }; 1237 static struct filterops tap_seltrue_filterops = { 1, NULL, tap_kqdetach, 1238 filt_seltrue }; 1239 1240 static int 1241 tap_cdev_kqfilter(dev_t dev, struct knote *kn) 1242 { 1243 return tap_dev_kqfilter(minor(dev), kn); 1244 } 1245 1246 static int 1247 tap_fops_kqfilter(file_t *fp, struct knote *kn) 1248 { 1249 return tap_dev_kqfilter(fp->f_devunit, kn); 1250 } 1251 1252 static int 1253 tap_dev_kqfilter(int unit, struct knote *kn) 1254 { 1255 struct tap_softc *sc = 1256 device_lookup_private(&tap_cd, unit); 1257 1258 if (sc == NULL) 1259 return ENXIO; 1260 1261 KERNEL_LOCK(1, NULL); 1262 switch(kn->kn_filter) { 1263 case EVFILT_READ: 1264 kn->kn_fop = &tap_read_filterops; 1265 break; 1266 case EVFILT_WRITE: 1267 kn->kn_fop = &tap_seltrue_filterops; 1268 break; 1269 default: 1270 KERNEL_UNLOCK_ONE(NULL); 1271 return EINVAL; 1272 } 1273 1274 kn->kn_hook = sc; 1275 mutex_spin_enter(&sc->sc_kqlock); 1276 SLIST_INSERT_HEAD(&sc->sc_rsel.sel_klist, kn, kn_selnext); 1277 mutex_spin_exit(&sc->sc_kqlock); 1278 KERNEL_UNLOCK_ONE(NULL); 1279 return 0; 1280 } 1281 1282 static void 1283 tap_kqdetach(struct knote *kn) 1284 { 1285 struct tap_softc *sc = (struct tap_softc *)kn->kn_hook; 1286 1287 KERNEL_LOCK(1, NULL); 1288 mutex_spin_enter(&sc->sc_kqlock); 1289 SLIST_REMOVE(&sc->sc_rsel.sel_klist, kn, knote, kn_selnext); 1290 mutex_spin_exit(&sc->sc_kqlock); 1291 KERNEL_UNLOCK_ONE(NULL); 1292 } 1293 1294 static int 1295 tap_kqread(struct knote *kn, long hint) 1296 { 1297 struct tap_softc *sc = (struct tap_softc *)kn->kn_hook; 1298 struct ifnet *ifp = &sc->sc_ec.ec_if; 1299 struct mbuf *m; 1300 int s, rv; 1301 1302 KERNEL_LOCK(1, NULL); 1303 s = splnet(); 1304 IFQ_POLL(&ifp->if_snd, m); 1305 1306 if (m == NULL) 1307 kn->kn_data = 0; 1308 else 1309 kn->kn_data = m->m_pkthdr.len; 1310 splx(s); 1311 rv = (kn->kn_data != 0 ? 1 : 0); 1312 KERNEL_UNLOCK_ONE(NULL); 1313 return rv; 1314 } 1315 1316 /* 1317 * sysctl management routines 1318 * You can set the address of an interface through: 1319 * net.link.tap.tap<number> 1320 * 1321 * Note the consistent use of tap_log in order to use 1322 * sysctl_teardown at unload time. 1323 * 1324 * In the kernel you will find a lot of SYSCTL_SETUP blocks. Those 1325 * blocks register a function in a special section of the kernel 1326 * (called a link set) which is used at init_sysctl() time to cycle 1327 * through all those functions to create the kernel's sysctl tree. 1328 * 1329 * It is not possible to use link sets in a module, so the 1330 * easiest is to simply call our own setup routine at load time. 1331 * 1332 * In the SYSCTL_SETUP blocks you find in the kernel, nodes have the 1333 * CTLFLAG_PERMANENT flag, meaning they cannot be removed. Once the 1334 * whole kernel sysctl tree is built, it is not possible to add any 1335 * permanent node. 1336 * 1337 * It should be noted that we're not saving the sysctlnode pointer 1338 * we are returned when creating the "tap" node. That structure 1339 * cannot be trusted once out of the calling function, as it might 1340 * get reused. So we just save the MIB number, and always give the 1341 * full path starting from the root for later calls to sysctl_createv 1342 * and sysctl_destroyv. 1343 */ 1344 static void 1345 sysctl_tap_setup(struct sysctllog **clog) 1346 { 1347 const struct sysctlnode *node; 1348 int error = 0; 1349 1350 if ((error = sysctl_createv(clog, 0, NULL, NULL, 1351 CTLFLAG_PERMANENT, 1352 CTLTYPE_NODE, "link", NULL, 1353 NULL, 0, NULL, 0, 1354 CTL_NET, AF_LINK, CTL_EOL)) != 0) 1355 return; 1356 1357 /* 1358 * The first four parameters of sysctl_createv are for management. 1359 * 1360 * The four that follows, here starting with a '0' for the flags, 1361 * describe the node. 1362 * 1363 * The next series of four set its value, through various possible 1364 * means. 1365 * 1366 * Last but not least, the path to the node is described. That path 1367 * is relative to the given root (third argument). Here we're 1368 * starting from the root. 1369 */ 1370 if ((error = sysctl_createv(clog, 0, NULL, &node, 1371 CTLFLAG_PERMANENT, 1372 CTLTYPE_NODE, "tap", NULL, 1373 NULL, 0, NULL, 0, 1374 CTL_NET, AF_LINK, CTL_CREATE, CTL_EOL)) != 0) 1375 return; 1376 tap_node = node->sysctl_num; 1377 } 1378 1379 /* 1380 * The helper functions make Andrew Brown's interface really 1381 * shine. It makes possible to create value on the fly whether 1382 * the sysctl value is read or written. 1383 * 1384 * As shown as an example in the man page, the first step is to 1385 * create a copy of the node to have sysctl_lookup work on it. 1386 * 1387 * Here, we have more work to do than just a copy, since we have 1388 * to create the string. The first step is to collect the actual 1389 * value of the node, which is a convenient pointer to the softc 1390 * of the interface. From there we create the string and use it 1391 * as the value, but only for the *copy* of the node. 1392 * 1393 * Then we let sysctl_lookup do the magic, which consists in 1394 * setting oldp and newp as required by the operation. When the 1395 * value is read, that means that the string will be copied to 1396 * the user, and when it is written, the new value will be copied 1397 * over in the addr array. 1398 * 1399 * If newp is NULL, the user was reading the value, so we don't 1400 * have anything else to do. If a new value was written, we 1401 * have to check it. 1402 * 1403 * If it is incorrect, we can return an error and leave 'node' as 1404 * it is: since it is a copy of the actual node, the change will 1405 * be forgotten. 1406 * 1407 * Upon a correct input, we commit the change to the ifnet 1408 * structure of our interface. 1409 */ 1410 static int 1411 tap_sysctl_handler(SYSCTLFN_ARGS) 1412 { 1413 struct sysctlnode node; 1414 struct tap_softc *sc; 1415 struct ifnet *ifp; 1416 int error; 1417 size_t len; 1418 char addr[3 * ETHER_ADDR_LEN]; 1419 uint8_t enaddr[ETHER_ADDR_LEN]; 1420 1421 node = *rnode; 1422 sc = node.sysctl_data; 1423 ifp = &sc->sc_ec.ec_if; 1424 (void)ether_snprintf(addr, sizeof(addr), CLLADDR(ifp->if_sadl)); 1425 node.sysctl_data = addr; 1426 error = sysctl_lookup(SYSCTLFN_CALL(&node)); 1427 if (error || newp == NULL) 1428 return error; 1429 1430 len = strlen(addr); 1431 if (len < 11 || len > 17) 1432 return EINVAL; 1433 1434 /* Commit change */ 1435 if (ether_aton_r(enaddr, sizeof(enaddr), addr) != 0) 1436 return EINVAL; 1437 if_set_sadl(ifp, enaddr, ETHER_ADDR_LEN, false); 1438 return error; 1439 } 1440 1441 /* 1442 * Module infrastructure 1443 */ 1444 #include "if_module.h" 1445 1446 IF_MODULE(MODULE_CLASS_DRIVER, tap, "") 1447