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Implement ifnet cloning for tun(4)/tap(4).

Browse source 
Make devfs cloning a sysctl/tunable which defaults to on.

If devfs cloning is enabled, only the super-user may create
tun(4)/tap(4)/vmnet(4) instances. Devfs cloning is still enabled by
default; it may be disabled from the loader or via sysctl with
"net.link.tap.devfs_cloning" and "net.link.tun.devfs_cloning".

Disabling its use affects potentially all tun(4)/tap(4) consumers
including OpenSSH, OpenVPN and VMware.

PR:		105228 (potentially also 90413, 105570)
Submitted by:	Landon Fuller
Tested by:	Andrej Tobola
Approved by:	core (rwatson)
MFC after:	4 weeks
This commit is contained in:
Bruce M Simpson 2007-02-04 16:32:46 +00:00
parent aecf742ea2
commit cd83bbd2aa
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=166497
4 changed files with 270 additions and 50 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
share/man/man4/tap.4
View file

@ -1,7 +1,7 @@
.\" $FreeBSD$
.\" Based on PR#2411
.\"
.Dd July 9, 2000
.Dd February 4, 2007
.Os
.Dt TAP 4
.Sh NAME
@ -41,11 +41,26 @@ The network interfaces are named
etc., one for each control device that has been opened.
These Ethernet network interfaces persist until
.Pa if_tap.ko
module is unloaded (if
.Nm
is built into your kernel, the network interfaces cannot be removed).
module is unloaded, or until removed with "ifconfig destroy" (see below).
.Pp
The
.Nm
devices are created using interface cloning.
This is done using the
.Dq ifconfig tap Ns Sy N No create
command.
This is the preferred method of creating
.Nm
devices.
The same method allows removal of interfaces.
For this, use the
.Dq ifconfig tap Ns Sy N No destroy
command.
.Pp
If the
.Xr sysctl 8
variable
.Va net.link.tap.devfs_cloning
is non-zero, the
.Nm
interface
permits opens on the special control device
@ -57,9 +72,21 @@ will return a handle for the lowest unused
device (use
.Xr devname 3
to determine which).
.Pp
.Bf Em
Disabling the legacy devfs cloning functionality may break existing
applications which use
.Nm ,
such as
.Tn VMware
and
.Xr ssh 1 .
It therefore defaults to being enabled until further notice.
.Ef
.Pp
Control devices (once successfully opened) persist until
.Pa if_tap.ko
is unloaded in the same way that network interfaces persist (see above).
is unloaded or the interface is destroyed.
.Pp
Each interface supports the usual Ethernet network interface
.Xr ioctl 2 Ns s ,

39
share/man/man4/tun.4
View file

@ -2,7 +2,7 @@
.\" $FreeBSD$
.\" Based on PR#2411
.\"
.Dd October 9, 2006
.Dd February 4, 2007
.Dt TUN 4
.Os
.Sh NAME
@ -42,11 +42,28 @@ The network interfaces are named
etc., one for each control device that has been opened.
These network interfaces persist until the
.Pa if_tun.ko
module is unloaded (if
.Nm
is built into your kernel, the network interfaces cannot be removed).
module is unloaded, or until removed with the
.Xr ifconfig 8
command.
.Pp
The
.Nm
devices are created using interface cloning.
This is done using the
.Dq ifconfig tap Ns Sy N No create
command.
This is the preferred method of creating
.Nm
devices.
The same method allows removal of interfaces.
For this, use the
.Dq ifconfig tap Ns Sy N No destroy
command.
.Pp
If the
.Xr sysctl 8
variable
.Va net.link.tun.devfs_cloning
is non-zero, the
.Nm
interface
permits opens on the special control device
@ -58,6 +75,18 @@ will return a handle for the lowest unused
device (use
.Xr devname 3
to determine which).
.Pp
.Bf Em
Disabling the legacy devfs cloning functionality may break existing
applications which use
.Nm ,
such as
.Xr ppp 8
and
.Xr ssh 1 .
It therefore defaults to being enabled until further notice.
.Ef
.Pp
Control devices (once successfully opened) persist until
.Pa if_tun.ko
is unloaded in the same way that network interfaces persist (see above).

158
sys/net/if_tap.c
View file

@ -62,6 +62,7 @@
#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_clone.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/if_types.h>
@ -93,6 +94,14 @@ static void tapifstart(struct ifnet *);
static int tapifioctl(struct ifnet *, u_long, caddr_t);
static void tapifinit(void *);
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);
static void vmnet_clone_destroy(struct ifnet *);
IFC_SIMPLE_DECLARE(tap, 0);
IFC_SIMPLE_DECLARE(vmnet, 0);
/* character device */
static d_open_t tapopen;
static d_close_t tapclose;
@ -142,6 +151,7 @@ static struct cdevsw tap_cdevsw = {
static struct mtx tapmtx;
static int tapdebug = 0; /* debug flag */
static int tapuopen = 0; /* allow user open() */
static int tapdclone = 1; /* enable devfs cloning */
static SLIST_HEAD(, tap_softc) taphead; /* first device */
static struct clonedevs *tapclones;
@ -154,10 +164,87 @@ SYSCTL_NODE(_net_link, OID_AUTO, tap, CTLFLAG_RW, 0,
"Ethernet tunnel software network interface");
SYSCTL_INT(_net_link_tap, OID_AUTO, user_open, CTLFLAG_RW, &tapuopen, 0,
"Allow user to open /dev/tap (based on node permissions)");
SYSCTL_INT(_net_link_tap, OID_AUTO, devfs_cloning, CTLFLAG_RW, &tapdclone, 0,
"Enably legacy devfs interface creation");
SYSCTL_INT(_net_link_tap, OID_AUTO, debug, CTLFLAG_RW, &tapdebug, 0, "");
TUNABLE_INT("net.link.tap.devfs_cloning", &tapdclone);
DEV_MODULE(if_tap, tapmodevent, NULL);
static int
tap_clone_create(struct if_clone *ifc, int unit, caddr_t params)
{
struct cdev *dev;
int i;
int extra;
if (strcmp(ifc->ifc_name, VMNET) == 0)
extra = VMNET_DEV_MASK;
else
extra = 0;
/* find any existing device, or allocate new unit number */
i = clone_create(&tapclones, &tap_cdevsw, &unit, &dev, extra);
if (i) {
dev = make_dev(&tap_cdevsw, unit2minor(unit | extra),
UID_ROOT, GID_WHEEL, 0600, "%s%d", ifc->ifc_name, unit);
if (dev != NULL) {
dev_ref(dev);
dev->si_flags |= SI_CHEAPCLONE;
}
}
tapcreate(dev);
return (0);
}
/* vmnet devices are tap devices in disguise */
static int
vmnet_clone_create(struct if_clone *ifc, int unit, caddr_t params)
{
return tap_clone_create(ifc, unit, params);
}
static void
tap_destroy(struct tap_softc *tp)
{
struct ifnet *ifp = tp->tap_ifp;
int s;
/* Unlocked read. */
KASSERT(!(tp->tap_flags & TAP_OPEN),
("%s flags is out of sync", ifp->if_xname));
knlist_destroy(&tp->tap_rsel.si_note);
destroy_dev(tp->tap_dev);
s = splimp();
ether_ifdetach(ifp);
if_free_type(ifp, IFT_ETHER);
splx(s);
mtx_destroy(&tp->tap_mtx);
free(tp, M_TAP);
}
static void
tap_clone_destroy(struct ifnet *ifp)
{
struct tap_softc *tp = ifp->if_softc;
mtx_lock(&tapmtx);
SLIST_REMOVE(&taphead, tp, tap_softc, tap_next);
mtx_unlock(&tapmtx);
tap_destroy(tp);
}
/* vmnet devices are tap devices in disguise */
static void
vmnet_clone_destroy(struct ifnet *ifp)
{
tap_clone_destroy(ifp);
}
/*
* tapmodevent
*
@ -169,7 +256,6 @@ tapmodevent(module_t mod, int type, void *data)
static eventhandler_tag eh_tag = NULL;
struct tap_softc *tp = NULL;
struct ifnet *ifp = NULL;
int s;
switch (type) {
case MOD_LOAD:
@ -186,6 +272,8 @@ tapmodevent(module_t mod, int type, void *data)
mtx_destroy(&tapmtx);
return (ENOMEM);
}
if_clone_attach(&tap_cloner);
if_clone_attach(&vmnet_cloner);
return (0);
case MOD_UNLOAD:
@ -207,6 +295,8 @@ tapmodevent(module_t mod, int type, void *data)
mtx_unlock(&tapmtx);
EVENTHANDLER_DEREGISTER(dev_clone, eh_tag);
if_clone_detach(&tap_cloner);
if_clone_detach(&vmnet_cloner);
mtx_lock(&tapmtx);
while ((tp = SLIST_FIRST(&taphead)) != NULL) {
@ -217,19 +307,7 @@ tapmodevent(module_t mod, int type, void *data)
TAPDEBUG("detaching %s\n", ifp->if_xname);
/* Unlocked read. */
KASSERT(!(tp->tap_flags & TAP_OPEN),
("%s flags is out of sync", ifp->if_xname));
knlist_destroy(&tp->tap_rsel.si_note);
destroy_dev(tp->tap_dev);
s = splimp();
ether_ifdetach(ifp);
if_free_type(ifp, IFT_ETHER);
splx(s);
mtx_destroy(&tp->tap_mtx);
free(tp, M_TAP);
tap_destroy(tp);
mtx_lock(&tapmtx);
}
mtx_unlock(&tapmtx);
@ -255,38 +333,63 @@ tapmodevent(module_t mod, int type, void *data)
static void
tapclone(void *arg, struct ucred *cred, char *name, int namelen, struct cdev **dev)
{
char devname[SPECNAMELEN + 1];
int i, unit, append_unit;
int extra;
int i, unit;
char *device_name = name;
if (*dev != NULL)
return;
device_name = TAP;
/*
* If tap cloning is enabled, only the superuser can create
* an interface.
*/
if (!tapdclone || priv_check_cred(cred, PRIV_NET_IFCREATE, 0) != 0)
return;
unit = 0;
append_unit = 0;
extra = 0;
/* We're interested in only tap/vmnet devices. */
if (strcmp(name, TAP) == 0) {
unit = -1;
} else if (strcmp(name, VMNET) == 0) {
device_name = VMNET;
extra = VMNET_DEV_MASK;
unit = -1;
} else if (dev_stdclone(name, NULL, device_name, &unit) != 1) {
device_name = VMNET;
extra = VMNET_DEV_MASK;
if (dev_stdclone(name, NULL, device_name, &unit) != 1)
} else if (dev_stdclone(name, NULL, TAP, &unit) != 1) {
if (dev_stdclone(name, NULL, VMNET, &unit) != 1) {
return;
} else {
extra = VMNET_DEV_MASK;
}
}
if (unit == -1)
append_unit = 1;
/* find any existing device, or allocate new unit number */
i = clone_create(&tapclones, &tap_cdevsw, &unit, dev, extra);
if (i) {
if (append_unit) {
/*
* We were passed 'tun' or 'tap', with no unit specified
* so we'll need to append it now.
*/
namelen = snprintf(devname, sizeof(devname), "%s%d", name,
unit);
name = devname;
}
*dev = make_dev(&tap_cdevsw, unit2minor(unit | extra),
UID_ROOT, GID_WHEEL, 0600, "%s%d", device_name, unit);
UID_ROOT, GID_WHEEL, 0600, "%s", name);
if (*dev != NULL) {
dev_ref(*dev);
(*dev)->si_flags |= SI_CHEAPCLONE;
}
}
if_clone_create(name, namelen, NULL);
} /* tapclone */
@ -385,16 +488,7 @@ tapopen(struct cdev *dev, int flag, int mode, struct thread *td)
if ((dev2unit(dev) & CLONE_UNITMASK) > TAPMAXUNIT)
return (ENXIO);
/*
* XXXRW: Non-atomic test-and-set of si_drv1. Currently protected
* by Giant, but the race actually exists under memory pressure as
* well even when running with Giant, as malloc() may sleep.
*/
tp = dev->si_drv1;
if (tp == NULL) {
tapcreate(dev);
tp = dev->si_drv1;
}
mtx_lock(&tp->tap_mtx);
if (tp->tap_flags & TAP_OPEN) {

84
sys/net/if_tun.c
View file

@ -45,6 +45,7 @@
#include <sys/random.h>
#include <net/if.h>
#include <net/if_clone.h>
#include <net/if_types.h>
#include <net/netisr.h>
#include <net/route.h>
@ -105,13 +106,22 @@ struct tun_softc {
static struct mtx tunmtx;
static MALLOC_DEFINE(M_TUN, TUNNAME, "Tunnel Interface");
static int tundebug = 0;
static int tundclone = 1;
static struct clonedevs *tunclones;
static TAILQ_HEAD(,tun_softc) tunhead = TAILQ_HEAD_INITIALIZER(tunhead);
SYSCTL_INT(_debug, OID_AUTO, if_tun_debug, CTLFLAG_RW, &tundebug, 0, "");
SYSCTL_DECL(_net_link);
SYSCTL_NODE(_net_link, OID_AUTO, tun, CTLFLAG_RW, 0,
"IP tunnel software network interface.");
SYSCTL_INT(_net_link_tun, OID_AUTO, devfs_cloning, CTLFLAG_RW, &tundclone, 0,
"Enable legacy devfs interface creation.");
TUNABLE_INT("net.link.tun.devfs_cloning", &tundclone);
static void tunclone(void *arg, struct ucred *cred, char *name,
int namelen, struct cdev **dev);
static void tuncreate(struct cdev *dev);
static void tuncreate(const char *name, struct cdev *dev);
static int tunifioctl(struct ifnet *, u_long, caddr_t);
static int tuninit(struct ifnet *);
static int tunmodevent(module_t, int, void *);
@ -119,6 +129,11 @@ static int tunoutput(struct ifnet *, struct mbuf *, struct sockaddr *,
struct rtentry *rt);
static void tunstart(struct ifnet *);
static int tun_clone_create(struct if_clone *, int, caddr_t);
static void tun_clone_destroy(struct ifnet *);
IFC_SIMPLE_DECLARE(tun, 0);
static d_open_t tunopen;
static d_close_t tunclose;
static d_read_t tunread;
@ -158,15 +173,45 @@ static struct cdevsw tun_cdevsw = {
.d_name = TUNNAME,
};
static int
tun_clone_create(struct if_clone *ifc, int unit, caddr_t params)
{
struct cdev *dev;
int i;
/* find any existing device, or allocate new unit number */
i = clone_create(&tunclones, &tun_cdevsw, &unit, &dev, 0);
if (i) {
/* No preexisting struct cdev *, create one */
dev = make_dev(&tun_cdevsw, unit2minor(unit),
UID_UUCP, GID_DIALER, 0600, "%s%d", ifc->ifc_name, unit);
if (dev != NULL) {
dev_ref(dev);
dev->si_flags |= SI_CHEAPCLONE;
}
}
tuncreate(ifc->ifc_name, dev);
return (0);
}
static void
tunclone(void *arg, struct ucred *cred, char *name, int namelen,
struct cdev **dev)
{
int u, i;
char devname[SPECNAMELEN + 1];
int u, i, append_unit;
if (*dev != NULL)
return;
/*
* If tun cloning is enabled, only the superuser can create an
* interface.
*/
if (!tundclone || priv_check_cred(cred, PRIV_NET_IFCREATE, 0) != 0)
return;
if (strcmp(name, TUNNAME) == 0) {
u = -1;
} else if (dev_stdclone(name, NULL, TUNNAME, &u) != 1)
@ -174,17 +219,29 @@ tunclone(void *arg, struct ucred *cred, char *name, int namelen,
if (u != -1 && u > IF_MAXUNIT)
return; /* Unit number too high */
if (u == -1)
append_unit = 1;
else
append_unit = 0;
/* find any existing device, or allocate new unit number */
i = clone_create(&tunclones, &tun_cdevsw, &u, dev, 0);
if (i) {
if (append_unit) {
namelen = snprintf(devname, sizeof(devname), "%s%d", name,
u);
name = devname;
}
/* No preexisting struct cdev *, create one */
*dev = make_dev(&tun_cdevsw, unit2minor(u),
UID_UUCP, GID_DIALER, 0600, "tun%d", u);
UID_UUCP, GID_DIALER, 0600, "%s", name);
if (*dev != NULL) {
dev_ref(*dev);
(*dev)->si_flags |= SI_CHEAPCLONE;
}
}
if_clone_create(name, namelen, NULL);
}
static void
@ -206,6 +263,17 @@ tun_destroy(struct tun_softc *tp)
free(tp, M_TUN);
}
static void
tun_clone_destroy(struct ifnet *ifp)
{
struct tun_softc *tp = ifp->if_softc;
mtx_lock(&tunmtx);
TAILQ_REMOVE(&tunhead, tp, tun_list);
mtx_unlock(&tunmtx);
tun_destroy(tp);
}
static int
tunmodevent(module_t mod, int type, void *data)
{
@ -219,8 +287,10 @@ tunmodevent(module_t mod, int type, void *data)
tag = EVENTHANDLER_REGISTER(dev_clone, tunclone, 0, 1000);
if (tag == NULL)
return (ENOMEM);
if_clone_attach(&tun_cloner);
break;
case MOD_UNLOAD:
if_clone_detach(&tun_cloner);
EVENTHANDLER_DEREGISTER(dev_clone, tag);
mtx_lock(&tunmtx);
@ -281,7 +351,7 @@ tunstart(struct ifnet *ifp)
/* XXX: should return an error code so it can fail. */
static void
tuncreate(struct cdev *dev)
tuncreate(const char *name, struct cdev *dev)
{
struct tun_softc *sc;
struct ifnet *ifp;
@ -299,8 +369,8 @@ tuncreate(struct cdev *dev)
ifp = sc->tun_ifp = if_alloc(IFT_PPP);
if (ifp == NULL)
panic("%s%d: failed to if_alloc() interface.\n",
TUNNAME, dev2unit(dev));
if_initname(ifp, TUNNAME, dev2unit(dev));
name, dev2unit(dev));
if_initname(ifp, name, dev2unit(dev));
ifp->if_mtu = TUNMTU;
ifp->if_ioctl = tunifioctl;
ifp->if_output = tunoutput;
@ -331,7 +401,7 @@ tunopen(struct cdev *dev, int flag, int mode, struct thread *td)
*/
tp = dev->si_drv1;
if (!tp) {
tuncreate(dev);
tuncreate(TUNNAME, dev);
tp = dev->si_drv1;
}