linux-kernel - SOCK_RAW does not receive broadcast (with VLAN unless PROMISC)

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Date:	Mon, 8 Jun 2009 21:05:25 +0300
From:	Gil Beniamini <gil.beniamini@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: SOCK_RAW does not receive broadcast (with VLAN unless PROMISC)

Dear Linux Experts,

My application is using PF_PACKET and SOCK_RAW in order to receive all
Ethernet packets for the machine-unicast MAC plus all broadcast
packets (like ARP broadcast).

That worked OK with kernel 2.6.20 (Ubuntu 7.04 with or without VLAN).

Now with kernel 2.6.28 (Ubuntu 9.04) it works OK only without-VLAN,
but with VLAN the application receive only packets for the
machine-unicast MAC, but no broadcast (like ARP broadcast) packets,
only if I set the socket to PROMISC mode, I start receive also
broadcast packets.

To me it seems a bug, as SOCK_RAW should pass all ‘received’ packet
(including broadcast) to the application, without the need for PROMISC
(which cause my machine to receive other machine unicast  packets, and
filter those by software)!

The original application:

sock=socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
memset((char *) &sockad, 0, sizeof(sockad));
sockad.sll_family = PF_PACKET;
sockad.sll_protocol = htons(ETH_P_ALL);
sockad.sll_ifindex = ethreq.ifr_ifindex;//the relevant unit number

Now the workaround is to set (unwanted) PROMISC mode:

ioctl(sock,SIOCGIFFLAGS,&ethreq);
ethreq.ifr_flags|=IFF_PROMISC; // why does 9.04 need this (+0x100) at
least once?!
ioctl(sock,SIOCSIFFLAGS,&ethreq);

Many thanks in advance,
Gil Beniamini
gil.beniamini@...il.com
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