why struct net_device has a field uc_promisc? How this field is used?
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why struct net_device has a field uc_promisc ? How this field is used? Thank
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why struct net_device has a field uc_promisc? How this field is used?
Thank you all!
When a device that doesn’t support unicast filtering has to listen to several unicast addresses, it is put on promiscous mode, according to
dev->uc_countanddev->uc_promisc. Check the__dev_set_rx_mode()function.Many devices implement
ndo_set_rx_mode(), and set their unicast (and multicast) filters viando_set_rx_mode(). For devices that don’t implement that, Linux sets the device to promiscuous mode, and keeps track of that fact withdev->uc_promisc.So there are several flags for promiscuous mode:
dev->flags & IFF_PROMISCmeans the device is in promiscuous mode.dev->gflags & IFF_PROMISCmeans the user has requested promiscuous mode.dev->uc_promiscmeans promiscuous mode has been enabled (actually, its reference count has been incremented) due to the need to listen to additional unicast address in a device that doesn’t implementndo_set_rx_mode().