| Message ID | 1427666762-23683-1-git-send-email-bernhard.thaler@wvnet.at |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Bernhard Thaler <bernhard.thaler@wvnet.at> Date: Mon, 30 Mar 2015 00:06:02 +0200 > BR_GROUPFWD_RESTRICTED bitmask restricts users from setting values to > /sys/class/net/brX/bridge/group_fwd_mask that allow forwarding of > some IEEE 802.1D Table 7-10 Reserved addresses: > > (MAC Control) 802.3 01-80-C2-00-00-01 > (Link Aggregation) 802.3 01-80-C2-00-00-02 > 802.1AB LLDP 01-80-C2-00-00-0E > > Relax BR_GROUPFWD_RESTRICTED to at least forward LLDP frames and document > group_fwd_mask. > > e.g. > echo 16384 > /sys/class/net/brX/bridge/group_fwd_mask > allows to forward LLDP frames. > > Tested on a simple bridge setup with two interfaces. Setting group_fwd_mask > as described above lets crafted LLDP frames traverse bridge. > > Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at> I don't understand why we want to allow forwarding LLDP by default, it specifically is the case that an 802.1D bridge is only compliant if it does not forward LLDP packets. We've blocked forwarding of LLDP by default for such a long time, so I argue against this change from the perspective of users expecting LLDP to be not forwarded by the Linux bridge by default. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 01.04.2015 21:28, David Miller wrote: > From: Bernhard Thaler <bernhard.thaler@wvnet.at> > Date: Mon, 30 Mar 2015 00:06:02 +0200 > >> BR_GROUPFWD_RESTRICTED bitmask restricts users from setting values to >> /sys/class/net/brX/bridge/group_fwd_mask that allow forwarding of >> some IEEE 802.1D Table 7-10 Reserved addresses: >> >> (MAC Control) 802.3 01-80-C2-00-00-01 >> (Link Aggregation) 802.3 01-80-C2-00-00-02 >> 802.1AB LLDP 01-80-C2-00-00-0E >> >> Relax BR_GROUPFWD_RESTRICTED to at least forward LLDP frames and document >> group_fwd_mask. >> >> e.g. >> echo 16384 > /sys/class/net/brX/bridge/group_fwd_mask >> allows to forward LLDP frames. >> >> Tested on a simple bridge setup with two interfaces. Setting group_fwd_mask >> as described above lets crafted LLDP frames traverse bridge. >> >> Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at> > > I don't understand why we want to allow forwarding LLDP by default, it > specifically is the case that an 802.1D bridge is only compliant if it > does not forward LLDP packets. > > We've blocked forwarding of LLDP by default for such a long time, so I > argue against this change from the perspective of users expecting LLDP > to be not forwarded by the Linux bridge by default. > BR_GROUPFWD_DEFAULT is unchanged. By default none of the IEEE 802.1D Table 7-10 Reserved addresses are forwarded by the bridge (except for STP BPDUs if STP is turned off on the bridge device). For users not changing /sys/class/net/brX/bridge/group_fwd_mask there should be no difference to current default bridge behavior. Only if users deliberately set group_fwd_mask to a value such as 16384 the bridge will start to forward LLDP frames. Current BR_GROUPFWD_RESTRICTED value though restricts users from setting such values to group_fwd_mask. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 01 Apr 2015 23:03:02 +0200 Bernhard Thaler <bernhard.thaler@wvnet.at> wrote: > > > On 01.04.2015 21:28, David Miller wrote: > > From: Bernhard Thaler <bernhard.thaler@wvnet.at> > > Date: Mon, 30 Mar 2015 00:06:02 +0200 > > > >> BR_GROUPFWD_RESTRICTED bitmask restricts users from setting values to > >> /sys/class/net/brX/bridge/group_fwd_mask that allow forwarding of > >> some IEEE 802.1D Table 7-10 Reserved addresses: > >> > >> (MAC Control) 802.3 01-80-C2-00-00-01 > >> (Link Aggregation) 802.3 01-80-C2-00-00-02 > >> 802.1AB LLDP 01-80-C2-00-00-0E > >> > >> Relax BR_GROUPFWD_RESTRICTED to at least forward LLDP frames and document > >> group_fwd_mask. > >> > >> e.g. > >> echo 16384 > /sys/class/net/brX/bridge/group_fwd_mask > >> allows to forward LLDP frames. > >> > >> Tested on a simple bridge setup with two interfaces. Setting group_fwd_mask > >> as described above lets crafted LLDP frames traverse bridge. > >> > >> Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at> > > > > I don't understand why we want to allow forwarding LLDP by default, it > > specifically is the case that an 802.1D bridge is only compliant if it > > does not forward LLDP packets. > > > > We've blocked forwarding of LLDP by default for such a long time, so I > > argue against this change from the perspective of users expecting LLDP > > to be not forwarded by the Linux bridge by default. > > > BR_GROUPFWD_DEFAULT is unchanged. By default none of the IEEE 802.1D > Table 7-10 Reserved addresses are forwarded by the bridge (except for > STP BPDUs if STP is turned off on the bridge device). > For users not changing /sys/class/net/brX/bridge/group_fwd_mask there > should be no difference to current default bridge behavior. > > Only if users deliberately set group_fwd_mask to a value such as 16384 > the bridge will start to forward LLDP frames. Current > BR_GROUPFWD_RESTRICTED value though restricts users from setting such > values to group_fwd_mask. If user wants to violate standards, it is probably best to let them. Unfortunately, there is no way to put a nastygram message up in response. There is no network version of TAINT on the kernel. I have heard that there are people that do weird things with bridges and Openstack that want this. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net index 5ecfd72..668604f 100644 --- a/Documentation/ABI/testing/sysfs-class-net +++ b/Documentation/ABI/testing/sysfs-class-net @@ -39,6 +39,25 @@ Description: Format is a string, e.g: 00:11:22:33:44:55 for an Ethernet MAC address. +What: /sys/class/net/<bridge iface>/bridge/group_fwd_mask +Date: January 2012 +KernelVersion: 3.2 +Contact: netdev@vger.kernel.org +Description: + Bitmask to allow forwarding of link local frames with address + 01-80-C2-00-00-0X on a bridge device. Only values that set bits + not matching BR_GROUPFWD_RESTRICTED in net/bridge/br_private.h + allowed. + Default value 0 does not forward any link local frames. + + Restricted bits: + 0: 01-80-C2-00-00-00 Bridge Group Address used for STP + 1: 01-80-C2-00-00-01 (MAC Control) 802.3 used for MAC PAUSE + 2: 01-80-C2-00-00-02 (Link Aggregation) 802.3ad + + Any values not setting these bits can be used. Take special + care when forwarding control frames e.g. 802.1X-PAE or LLDP. + What: /sys/class/net/<iface>/broadcast Date: April 2005 KernelVersion: 2.6.12 diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index b46fa0c..ef8ef3f 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -33,8 +33,8 @@ /* Control of forwarding link local multicast */ #define BR_GROUPFWD_DEFAULT 0 -/* Don't allow forwarding control protocols like STP and LLDP */ -#define BR_GROUPFWD_RESTRICTED 0x4007u +/* Don't allow forwarding of control protocols like STP, MAC PAUSE and LACP */ +#define BR_GROUPFWD_RESTRICTED 0x0007u /* The Nearest Customer Bridge Group Address, 01-80-C2-00-00-[00,0B,0C,0D,0F] */ #define BR_GROUPFWD_8021AD 0xB801u
BR_GROUPFWD_RESTRICTED bitmask restricts users from setting values to /sys/class/net/brX/bridge/group_fwd_mask that allow forwarding of some IEEE 802.1D Table 7-10 Reserved addresses: (MAC Control) 802.3 01-80-C2-00-00-01 (Link Aggregation) 802.3 01-80-C2-00-00-02 802.1AB LLDP 01-80-C2-00-00-0E Relax BR_GROUPFWD_RESTRICTED to at least forward LLDP frames and document group_fwd_mask. e.g. echo 16384 > /sys/class/net/brX/bridge/group_fwd_mask allows to forward LLDP frames. Tested on a simple bridge setup with two interfaces. Setting group_fwd_mask as described above lets crafted LLDP frames traverse bridge. Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at> --- v1 * this version only removes LLDP restriction from BR_GROUPFWD_RESTRICTED * adds documentation of /sys/class/net/brX/bridge/group_fwd_mask (v0) * initial version "bridge: remove BR_GROUPFWD_RESTRICTED for arbitrary forwarding of reserved addresses" Documentation/ABI/testing/sysfs-class-net | 19 +++++++++++++++++++ net/bridge/br_private.h | 4 ++-- 2 files changed, 21 insertions(+), 2 deletions(-)