Interface promiscuity obscurity in Linux

From: Ricardo Branco (97-29312at_private)
Date: Wed Jul 24 2002 - 13:20:19 PDT

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    This affects Linux 2.2 and 2.4

Using libpcap to put the interface in promiscuous mode, will cause that
ifconfig(8) doesn't show it!

libpcap uses setsockopt(..., SOL_PACKET, PACKET_ADD_MEMBERSHIP, ...) with
PACKET_MR_PROMISC to set the interface in promiscuous mode.

I notified this to the tcpdump-workers mailing list and the problem is
that the setsockopt() sets the promisc flag in a variable that is not the
same as the one that the SIOCGIFFLAGS ioctl() reads. I don't have the
kernel source right now to make this advisory more precise.

Well, sorry for my not-so-good english
Enjoy

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