selftests/net: remove min gso test in packet_snd

This patch removed the 'raw gso min size - 1' test which
always fails now:
./in_netns.sh ./psock_snd -v -c -g -l "${mss}"
raw gso min size - 1 (expected to fail)
tx: 1524
rx: 1472
OK

After commit 7c6d2ecbda83 ("net: be more gentle about silly
gso requests coming from user"), we relaxed the min gso_size
check in virtio_net_hdr_to_skb().
So when a packet which is smaller then the gso_size,
GSO for this packet will not be set, the packet will be
send/recv successfully.

Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests/net: improve descriptions for XFAIL cases in psock_snd.sh

Before changing this it's a bit confusing to read test output:
raw csum_off with bad offset (fails)
./psock_snd: write: Invalid argument

Change "fails" in the test case description to "expected to fail", so
that the test output can be more understandable.

Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests/net: add packet socket packet_snd test

Add regression tests for PF_PACKET transmission using packet_snd.

The TPACKET ring interface has tests for transmission and reception.
This is an initial stab at the same for the send call based interface.

Packets are sent over loopback, then read twice. The entire packet is
read from another packet socket and compared. The packet is also
verified to arrive at a UDP socket for protocol conformance.

The test sends a packet over loopback, testing the following options
(not the full cross-product):

- SOCK_DGRAM
- SOCK_RAW
- vlan tag
- qdisc bypass
- bind() and sendto()
- virtio_net_hdr
- csum offload (NOT actual csum feature, ignored on loopback)
- gso

Besides these basic functionality tests, the test runs from a set
of bounds checks, positive and negative. Running over loopback, which
has dev->min_header_len, it cannot generate variable length hhlen.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>