samples/bpf: Use consistent include paths for libbpf

Fix all files in samples/bpf to include libbpf header files with the bpf/
prefix, to be consistent with external users of the library. Also ensure
that all includes of exported libbpf header files (those that are exported
on 'make install' of the library) use bracketed includes instead of quoted.

To make sure no new files are introduced that doesn't include the bpf/
prefix in its include, remove tools/lib/bpf from the include path entirely,
and use tools/lib instead.

Fixes: 6910d7d3867a ("selftests/bpf: Ensure bpf_helper_defs.h are taken from selftests dir")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/157952560911.1683545.8795966751309534150.stgit@toke.dk

bpf: fix samples xdp_tx_iptunnel and tc_l2_redirect with fake KBUILD_MODNAME

Fix build errors for samples/bpf xdp_tx_iptunnel and tc_l2_redirect,
when dynamic debugging is enabled (CONFIG_DYNAMIC_DEBUG) by defining a
fake KBUILD_MODNAME.

Just like Daniel Borkmann fixed other samples/bpf in commit
96a8eb1eeed2 ("bpf: fix samples to add fake KBUILD_MODNAME").

Fixes: 12d8bb64e3f6 ("bpf: xdp: Add XDP example for head adjustment")
Fixes: 90e02896f1a4 ("bpf: Add test for bpf_redirect to ipip/ip6tnl")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

bpf: Add test for bpf_redirect to ipip/ip6tnl

The test creates two netns, ns1 and ns2. The host (the default netns)
has an ipip or ip6tnl dev configured for tunneling traffic to the ns2.

ping VIPS from ns1 <----> host <--tunnel--> ns2 (VIPs at loopback)

The test is to have ns1 pinging VIPs configured at the loopback
interface in ns2.

The VIPs are 10.10.1.102 and 2401:face::66 (which are configured
at lo@ns2). [Note: 0x66 => 102].

At ns1, the VIPs are routed _via_ the host.

At the host, bpf programs are installed at the veth to redirect packets
from a veth to the ipip/ip6tnl. The test is configured in a way so
that both ingress and egress can be tested.

At ns2, the ipip/ip6tnl dev is configured with the local and remote address
specified. The return path is routed to the dev ipip/ip6tnl.

During egress test, the host also locally tests pinging the VIPs to ensure
that bpf_redirect at egress also works for the direct egress (i.e. not
forwarding from dev ve1 to ve2).

Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>