From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo =?utf-8?b?VHViw61v?= <rtpardavila@gmail.com>
Subject: Re: Single socket with =?utf-8?b?VFhfUklORw==?= and =?utf-8?b?UlhfUklORw==?=
Date: Wed, 15 May 2013 13:32:41 +0000 (UTC)
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References: <loom.20130515T144941-798@post.gmane.org> <51938BAD.5050502@redhat.com>
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Daniel Borkmann <dborkman <at> redhat.com> writes:

>=20
> On 05/15/2013 02:53 PM, Ricardo Tub=C3=ADo wrote:
> > Once I tell kernel to export the TX_RING through setsockopt() (see =
code
> > below) I always get an error (EBUSY) if i try to tell kernel to exp=
ort the
> > RX_RING with the same socket descriptor. Therefore, I have to open =
an
> > additional socket for the RX_RING and I require of two sockets when=
 I though
> > that I would only require of one socket for both TX and RX using mm=
ap()ed
> > memory.
> >
> > Do I need both sockets or am I doing something wrong?
>=20
> The second time you call init_ring() in your code e.g. with TX_RING, =
where
> you have previously set it up for the RX_RING. The kernel will give y=
ou
> -EBUSY because the packet socket is already mmap(2)'ed.
>=20

Ok, so if I make the following system calls:

void *ring=3DNULL;
setsockopt(socket_fd, SOL_PACKET, PACKET_RX_RING, p, LEN__TPACKET_REQ);
ring =3D mmap(NULL, ring_len, ring_access_flags, MAP_SHARED, socket_fd,=
 0);

Would I be permitted to use the ring map obtained both for RX and for T=
X? If
so, for me it is confusing to use PACKET_RX_RING if I can also TX data
through that ring...