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This series implements two new per-cgroup hooks: getsockopt and
setsockopt along with a new sockopt program type. The idea is pretty
similar to recently introduced cgroup sysctl hooks, but
implementation is simpler (no need to convert to/from strings).
What this can be applied to:
* move business logic of what tos/priority/etc can be set by
containers (either pass or reject)
* handle existing options (or introduce new ones) differently by
propagating some information in cgroup/socket local storage
Compared to a simple syscall/{g,s}etsockopt tracepoint, those
hooks are context aware. Meaning, they can access underlying socket
and use cgroup and socket local storage.
v9:
* allow overwriting setsocktop arguments (Alexei Starovoitov)
(see individual changes for more changelog details)
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