Re: SOCK_RAW does not receive broadcast (with VLAN unless PROMISC)

[David Miller]

From: Gil Beniamini <gil.beniamini@xxxxxxxxx>
Date: Mon, 8 Jun 2009 21:05:25 +0300

> 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).

Please post networking questions and reports to netdev@xxxxxxxxxxxxxxx
which is where the networking experts are subscribed.

I am also fully aware of your problem as Linus Torvalds forwarded
your report to me last week, you just need to be patient as I simply
haven't had a chance to look into it yet.

> 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 âreceivedâ 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@xxxxxxxxx
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