On 11/2/2012 4:01 PM, Ben Hutchings wrote:

On Fri, 2012-11-02 at 15:48 -0700, John Fastabend wrote:

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On 11/2/2012 3:38 PM, Ben Hutchings wrote:

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On Wed, 2012-10-24 at 11:13 -0700, John Fastabend wrote:

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Hardware switches may support enabling and disabling the
loopback switch which puts the device in a VEPA mode defined
in the IEEE 802.1Qbg specification. In this mode frames are
not switched in the hardware but sent directly to the switch.
SR-IOV capable NICs will likely support this mode I am
aware of at least two such devices. Also I am told (but don't
have any of this hardware available) that there are devices
that only support VEPA modes. In these cases it is important
at a minimum to be able to query these attributes.

This patch adds an additional IFLA_BRIDGE_MODE attribute that can be
set and dumped via the PF_BRIDGE:{SET|GET}LINK operations. Also
anticipating bridge attributes that may be common for both embedded
bridges and software bridges this adds a flags attribute
IFLA_BRIDGE_FLAGS currently used to determine if the command or event
is being generated to/from an embedded bridge or software bridge.
Finally, the event generation is pulled out of the bridge module and
into rtnetlink proper.

[...]

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+	if (attr && nla_type(attr) == IFLA_BRIDGE_FLAGS)

This condition is wrong; attr will *not* be NULL if the
nla_for_each_nested() loop terminates without finding an
IFLA_BRIDGE_FLAGS attribute.

It might be NULL if the nlmsg has no IFLA_AF_SPEC attr. In this case
we still need to send the PROTINFO attribute to the master which
could be the linux bridge.

[...]

I think nla_for_each_nested() can leave attr non-null but also not valid
for use with nla_type().  And that's a problem.  I think it would be
better to use an explicit flag for whether we found that attribute,
rather than trying to re-test here.

Ben.

OK. I'll add an explicit flag for this. Thanks.