Describe what each input flag does and who uses it. Cc: Willem de Bruijn <willemb@xxxxxxxxxx> Cc: Petar Penkov <ppenkov@xxxxxxxxxx> Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx> --- Documentation/bpf/prog_flow_dissector.rst | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/Documentation/bpf/prog_flow_dissector.rst b/Documentation/bpf/prog_flow_dissector.rst index ed343abe541e..0f3f380b2ce4 100644 --- a/Documentation/bpf/prog_flow_dissector.rst +++ b/Documentation/bpf/prog_flow_dissector.rst @@ -26,6 +26,7 @@ and output arguments. * ``nhoff`` - initial offset of the networking header * ``thoff`` - initial offset of the transport header, initialized to nhoff * ``n_proto`` - L3 protocol type, parsed out of L2 header + * ``flags`` - optional flags Flow dissector BPF program should fill out the rest of the ``struct bpf_flow_keys`` fields. Input arguments ``nhoff/thoff/n_proto`` should be @@ -101,6 +102,23 @@ can be called for both cases and would have to be written carefully to handle both cases. +Flags +===== + +``flow_keys->flags`` might contain optional input flags that work as follows: + +* ``FLOW_DISSECTOR_F_PARSE_1ST_FRAG`` - tells BPF flow dissector to continue + parsing first fragment; the default expected behavior is that flow dissector + returns as soon as it finds out that the packet is fragmented; + used by ``eth_get_headlen`` to estimate length of all headers for GRO. +* ``FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL`` - tells BPF flow dissector to stop + parsing as soon as it reaches IPv6 flow label; used by ``___skb_get_hash`` + and ``__skb_get_hash_symmetric`` to get flow hash. +* ``FLOW_DISSECTOR_F_STOP_AT_ENCAP`` - tells BPF flow dissector to stop + parsing as soon as it reaches encapsulated headers; used by routing + infrastructure. + + Reference Implementation ======================== -- 2.22.0.657.g960e92d24f-goog
