On Mon, Sep 22, 2008 at 06:49:14PM -0700, Maksim Yevmenkin wrote: > [...] > > >>> ok, how about attached patch. i put it together *very* quickly and > >>> only gave it a light testing. its for tap(4), because i could compile > >>> it as a module and tun(4) is compiled into kernel by default, but the > >>> idea should identical for tun(4). should be even simpler for tun(4) > >>> because it does not have to deal with 2 kind of devices (i.e. tap and > >>> vmnet). give it a try, and see if it works. please try both cloning > >>> paths, i.e. > >>> > >>> 1) cat /dev/tap (/dev/vmnet) with and/or without unit number > >>> > >>> and > >>> > >>> 2) ifconfig tapX (vmnetX) create/destroy > >>> > >>> in the mean time i will prepare something similar for tun(4). > >> > >> attached is similar patch for tun(4). i only made sure it compiles :) > >> rebuilding kernel now... > > attached is a slightly better patch for tap(4). the idea is to use > extra ALLOCATED flag that prevents the race Kostik pointed out. could > you please give it a try? any review comments are greatly appreciated. > if this is acceptable, i will prepare something similar for tun(4) The tap should use make_dev_credf(MAKEDEV_REF) instead of make_dev/dev_ref sequence in the clone handler. For similar reasons, I think it is slightly better to do a dev_ref() immediately after setting the TAP_ALLOCATED flag without dropping tapmtx. I cannot figure out how tap_clone_create/tap_clone_destroy are being called. Can it be garbage-collected ? The whole module unload sequence looks unsafe. > > thanks, > max > --- if_tap.c.orig 2008-09-08 17:20:57.000000000 -0700 > +++ if_tap.c 2008-09-22 18:36:16.000000000 -0700 > _at__at_ -94,6 +94,7 _at__at_ > static int tapifioctl(struct ifnet *, u_long, caddr_t); > static void tapifinit(void *); > > +static int tap_clone_lookup(struct cdev **, u_short); > static int tap_clone_create(struct if_clone *, int, caddr_t); > static void tap_clone_destroy(struct ifnet *); > static int vmnet_clone_create(struct if_clone *, int, caddr_t); > _at__at_ -176,6 +177,30 _at__at_ > DEV_MODULE(if_tap, tapmodevent, NULL); > > static int > +tap_clone_lookup(struct cdev **dev, u_short extra) > +{ > + struct tap_softc *tp; > + > + mtx_lock(&tapmtx); > + SLIST_FOREACH(tp, &taphead, tap_next) { > + mtx_lock(&tp->tap_mtx); > + > + if ((tp->tap_flags & (TAP_OPEN|TAP_ALLOCATED|extra)) == extra) { > + tp->tap_flags |= TAP_ALLOCATED; > + *dev = tp->tap_dev; > + mtx_unlock(&tp->tap_mtx); > + mtx_unlock(&tapmtx); > + > + return (1); > + } > + mtx_unlock(&tp->tap_mtx); > + } > + mtx_unlock(&tapmtx); > + > + return (0); > +} > + > +static int > tap_clone_create(struct if_clone *ifc, int unit, caddr_t params) > { > struct cdev *dev; > _at__at_ -288,7 +313,7 _at__at_ > mtx_lock(&tapmtx); > SLIST_FOREACH(tp, &taphead, tap_next) { > mtx_lock(&tp->tap_mtx); > - if (tp->tap_flags & TAP_OPEN) { > + if (tp->tap_flags & (TAP_OPEN|TAP_ALLOCATED)) { > mtx_unlock(&tp->tap_mtx); > mtx_unlock(&tapmtx); > return (EBUSY); > _at__at_ -353,8 +378,18 _at__at_ > > /* We're interested in only tap/vmnet devices. */ > if (strcmp(name, TAP) == 0) { > + if (tap_clone_lookup(dev, 0)) { > + dev_ref(*dev); > + return; > + } > + > unit = -1; > } else if (strcmp(name, VMNET) == 0) { > + if (tap_clone_lookup(dev, TAP_VMNET)) { > + dev_ref(*dev); > + return; > + } > + > unit = -1; > extra = VMNET_DEV_MASK; > } else if (dev_stdclone(name, NULL, TAP, &unit) != 1) { > _at__at_ -559,12 +594,11 _at__at_ > KNOTE_UNLOCKED(&tp->tap_rsel.si_note, 0); > > mtx_lock(&tp->tap_mtx); > - tp->tap_flags &= ~TAP_OPEN; > + tp->tap_flags &= ~(TAP_OPEN|TAP_ALLOCATED); > tp->tap_pid = 0; > mtx_unlock(&tp->tap_mtx); > > - TAPDEBUG("%s is closed. minor = %#x\n", > - ifp->if_xname, minor(dev)); > + TAPDEBUG("%s is closed. minor = %#x\n", ifp->if_xname, minor(dev)); > > return (0); > } /* tapclose */ > --- if_tapvar.h.orig 2005-06-10 12:04:52.000000000 -0700 > +++ if_tapvar.h 2008-09-22 17:34:00.000000000 -0700 > _at__at_ -54,6 +54,7 _at__at_ > #define TAP_ASYNC (1 << 3) > #define TAP_READY (TAP_OPEN|TAP_INITED) > #define TAP_VMNET (1 << 4) > +#define TAP_ALLOCATED (1 << 5) > > u_int8_t ether_addr[ETHER_ADDR_LEN]; /* ether addr of the remote side */ >
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