ebpf: add helper to retrieve net_cls's classid cookie

It would be very useful to retrieve the net_cls's classid from an eBPF
program to allow for a more fine-grained classification, it could be
directly used or in conjunction with additional policies. I.e. docker,
but also tooling such as cgexec, can easily run applications via net_cls
cgroups:

  cgcreate -g net_cls:/foo
  echo 42 > foo/net_cls.classid
  cgexec -g net_cls:foo <prog>

Thus, their respecitve classid cookie of foo can then be looked up on
the egress path to apply further policies. The helper is desigend such
that a non-zero value returns the cgroup id.

Signed-off-by: Daniel Borkmann <[email protected]>
Cc: Thomas Graf <[email protected]>
Acked-by: Alexei Starovoitov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

0 files changed, 0 insertions, 0 deletions