[lwip-users] Promiscous Mode (Ref: Windows 7 Startup crashes LwIP and Free RTOS)

[Marco Jakobs]

Hi all,

while checking some stuff for my project at work, i discovered this EMAC 
configuration:

    /* Enable the copy of data into the buffers, ignore broadcasts,
       and don't copy FCS. */
    AT91C_BASE_EMAC->EMAC_NCFGR |= ( AT91C_EMAC_CAF | AT91C_EMAC_NBC | 
AT91C_EMAC_DRFCS );

This sets the EMAC into promiscous mode - which means that *all* 
received frames will be copied. Is there any reason for giving LwIP all 
the anycasts, multicasts etc. which are spread by different PCs, 
printers etc...?

This may also affect my issue in the Windows 7 Startup crash thread ... 
i'll try it tonight at home.

My first tests show that it works also in the non-promiscuous mode, with 
which of course the broadcasts have to be enabled (for getting the ARP 
queries). Now i can also connect my device to a hub with a downloading 
PC connected without getting watchdog resets due to never running 
low-priority tasks (in promicuous mode the high priority EMAC task will 
take nearly all CPU power to process the incoming frames).

So, changing the init to

    AT91C_BASE_EMAC->EMAC_NCFGR |= ( AT91C_EMAC_DRFCS );

looks good for me!

Is there any reason for having the promiscuous mode enabled in LwIP?

Thanks,
Marco