Merge branch 'tc-qevent-block' into next

Merge branch 'tc-qevent-block' into next

Petr Machata  says:

====================

When a list of filters at a given block is requested, tc first validates
that the block exists before doing the filter query. Currently the
validation routine checks ingress and egress blocks. But now that blocks
can be bound to qevents as well, qevent blocks should be looked for as
well:

    # ip link add up type dummy
    # tc qdisc add dev dummy1 root handle 1: \
         red min 30000 max 60000 avpkt 1000 qevent early_drop block 100
    # tc filter add block 100 pref 1234 handle 102 matchall action drop
    # tc filter show block 100
    Cannot find block "100"

This patchset fixes this issue:

    # tc filter show block 100
    filter protocol all pref 1234 matchall chain 0
    filter protocol all pref 1234 matchall chain 0 handle 0x66
      not_in_hw
            action order 1: gact action drop
             random type none pass val 0
             index 2 ref 1 bind 1

In patch #1, the helpers and necessary infrastructure is introduced,
including a new qdisc_util callback that implements sniffing out bound
blocks in a given qdisc.

In patch #2, RED implements the new callback.

v3:
- Patch #1:
    - Do not pass &ctx->found directly to has_block. Do it through a
      helper variable, so that the callee does not overwrite the result
      already stored in ctx->found.

v2:
- Patch #1:
    - In tc_qdisc_block_exists_cb(), do not initialize 'q'.
    - Propagate upwards errors from q->has_block.

====================

Signed-off-by: David Ahern <dsahern@kernel.org>