Extend bpf_skb_adjust_room growth to mark inner MAC header so that L2 encapsulation can be used for tc tunnels.
Patch #1 extends the existing test_tc_tunnel to support UDP encapsulation; later we want to be able to test MPLS over UDP and MPLS over GRE encapsulation.
Patch #2 adds the BPF_F_ADJ_ROOM_ENCAP_L2(len) macro, which allows specification of inner mac length. Other approaches were explored prior to taking this approach. Specifically, I tried automatically computing the inner mac length on the basis of the specified flags (so inner maclen for GRE/IPv4 encap is the len_diff specified to bpf_skb_adjust_room minus GRE + IPv4 header length for example). Problem with this is that we don't know for sure what form of GRE/UDP header we have; is it a full GRE header, or is it a FOU UDP header or generic UDP encap header? My fear here was we'd end up with an explosion of flags. The other approach tried was to support inner L2 header marking as a separate room adjustment, i.e. adjust for L3/L4 encap, then call bpf_skb_adjust_room for L2 encap. This can be made to work but because it imposed an order on operations, felt a bit clunky.
Patch #3 syncs tools/ bpf.h.
Patch #4 extends the tests again to support MPLSoverGRE and MPLSoverUDP encap, along with existing test coverage.
Alan Maguire (4): selftests_bpf: extend test_tc_tunnel for UDP encap bpf: add layer 2 encap support to bpf_skb_adjust_room bpf: sync bpf.h to tools/ for BPF_F_ADJ_ROOM_ENCAP_L2 selftests_bpf: extend test_tc_tunnel.sh test for L2 encap
include/uapi/linux/bpf.h | 5 + net/core/filter.c | 19 +- tools/include/uapi/linux/bpf.h | 5 + tools/testing/selftests/bpf/progs/test_tc_tunnel.c | 281 ++++++++++++++++----- tools/testing/selftests/bpf/test_tc_tunnel.sh | 105 +++++--- 5 files changed, 318 insertions(+), 97 deletions(-)