[lldp-devel] Question on is_valid_lldp_device function

Paddu Krishnan (padkrish) padkrish at cisco.com
Mon Nov 18 04:44:56 UTC 2013

Thanks John. What you said makes sense. Let me think some more on this.


On 11/13/13 1:39 PM, "John Fastabend" <john.fastabend at gmail.com> wrote:

>On 11/10/2013 10:52 PM, Paddu Krishnan (padkrish) wrote:
>> Hello,
>> I see that this function seems to return false for regular Linux bridges
>> as well as OVS bridges created using 1.4 version.
>> I see that the called function 'is_bridge' checks for the presence
>> of /sys/class/net/%s/bridge directory.
>> I am trying to understand the reason behind this.
>> I understand from our discussion earlier that there are interop issues
>> in LLDP with virtual switches like OVS. But, if one is able to get
>> around this in OVS, LLDPAD still may not receive the frames because of
>> the above check due to which the interface may not get added (function
>> 'add_port') does not get called.
>> Can someone please help me understand this behavior?
>lldpad uses the ports attached to the bridge and has no code to support
>running on the bridge interfaces.
>For example if eth0, eth1 are slaves of the bridge interface br0 lldpad
>will manage eth0 and eth1 sending/receiving lldpdu's over those
>interfaces. The standard linux bridge ./net/bridge supports this.
>If we ran lldpad over the br0 interface there would need to be code to
>learn which interface the lldpdu was received on and which interface to
>send a lldpdu out. It was easier to run over the non-bridge interfaces
>and let the bridge devices pass mac addresses that are reserved by
>"IEEE 802.1D Table 7-10 Reserved addresses" up the stack. The kernel
>function is_link_local_ether_addr() is used to do this check in the
>bridge module.
>> Thanks,
>> Paddu
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>John Fastabend         Intel Corporation

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