On 10/12/17 18:25, Willem de Bruijn wrote:
On Thu, Oct 12, 2017 at 12:30 PM, Willem de Bruijn
<willemdebruijn.ker...@gmail.com> wrote:
On Thu, Oct 12, 2017 at 11:44 AM, Anton Ivanov
<anton.iva...@cambridgegreys.com> wrote:
Found it.
Two bugs canceling each other.
The bind sequence in: psock_txring_vnet.c is wrong.
It does the following addr.sll_protocol = htons(ETH_P_IP);
before calling bind.
If you set addr.sll_protocol to ETH_P_ALL where it should have been in the
first place the test program blows up with -ENOBUFS
There is no such requirement that the socket should bind to ETH_P_ALL.
There is no requirement to bind to ETH_P_IP either and most code
examples going back more than 10 years to the days of TCP Illustrated
use ALL.
I just did the v6 test - if you bind with ETH_P_IP GSO on TCPv6 is
broken and returns NOBUF and vice versa.
I think what is happening is that this value is taken into account when
looking at "what should I use to segment it with" in skb_mac_gso_segment
which is invoked at the end of the verification chain which starts in
packet_direct_xmit in af_packet.c
packet_snd sets skb->protocol based on the protocol that the packet
socket is bound to. Binding to ETH_P_IP is the right choice here.
To avoid having to open multiple sockets for different protocols,
sockaddr_ll can also be passed in the msg_name argument on
each call.
Does not work for vnet headers - it honors what you bound with. I tried
to bind with ETH_ALL and pass ETH_P_IP as an arg and it ENOBUF-ed
--
Anton R. Ivanov
Cambridge Greys Limited, England and Wales company No 10273661
http://www.cambridgegreys.com/
