HostAP processing of Ethernet FCS when in bridge mode

Lewis Adam-CAL022 Adam.Lewis at motorola.com
Thu Jan 22 11:01:28 EST 2004


Hi all,
 
I'm trying to verify an assumption I have on what the wireless driver should
do with the FCS of an Ethernet frame when it receives it from eth0 when eth0
and wlan0 are bridged together.  From looking at the prism2_tx() function,
it is clear that the SRC and DST fields from the Ethernet header are copied
to the txdesc.  After that, the skb->data is copied to the BAP (minus the
first 14 bytes/Ethernet header).  My question then is this - it does not
appear as though the code makes any effort to detect the presence of a
trailing FCS and the end of skb->data, as it would exist in the case where
eth0 and wlan0 are tied together via a bridge (br0).  It was my
understanding (or maybe assumption is a better word) that the data sent over
the wireless link should not have the Ethernet FCS encapsulated within the
802.11 payload.  Is this correct, or am I misunderstanding?
 
Thanks for the clarification!
Adam
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