[PATCH proxmox-ebpf v5 0/5] add proxmox-ebpf library

[Hannes Laimer <h.laimer@proxmox.com>]

proxmox-ebpf holds the eBPF programs and the code that loads, attaches
and updates them, grouped into subsystems. It is a library only, whoever
needs a subsystem pulls in just that one through a cargo feature and
calls it from their side. This series is the shared part, the actual
subsystems come as their own series on top.

The core is the shared subsystem code. It takes care of everything from
loading and attaching per interface to pinning in bpffs and tearing down
again. So nothing has to keep running, and each call picks up where the
last one left off. The build records a hash of the compiled object and a
schema version per subsystem, so a call can tell what changed. A changed
program or map schema is swapped onto the existing links without
interrupting traffic. The new maps are filled before the links move onto
them. The BPF C code is also built natively against a small shim, so the
parsing and packet building logic can be tested without a kernel.
Packaging is debcargo like the other Rust crates.

Every change runs under a lock per subsystem, a full apply takes it
exclusively and a single-interface step shared, like the pmxcfs domain
locks. The holder reads the input of its change under the lock and
writes before it lets go. So a change and a full apply reach the kernel
in the order they read their input, and nothing has to order them after
the fact. A holder that never returns makes the waiters time out instead
of hanging them. A subsystem can also hand over the whole content of its
maps. The programs then move onto the new content one link at a time and
never read a mix of old and new entries, and a write the kernel refuses
leaves the old content in place. The programs of different subsystems on
one interface run in a fixed order. An attach places its link relative
to the links the other subsystems already hold there, so the order holds
however the attaches are timed, and an update keeps every link in its
place.

The series applies on top of the scaffolding commit of the repo, which
is not on the list since it carries the vendored vmlinux.h at ~167k
lines. It is on my staff repo along with these five commits.

v5:
 * add a call that replaces the maps as a whole, it uses more space and
   writes everything instead of only what changed, but leaves the old
   content in place instead of a mix, in cases where the write fails
   with ENOMEM. Subsystems choose which they need
 * install/upgrade now also use this newly added replace path, this
   simplifies the process and also closes a hole where attached programs
   would read empty maps, shortly before they were filled after a schema
   version bump
 * the run order of the subsystems is written to
   `/run/proxmox-ebpf/order` by a full apply and every attach places by
   it, so a stale process running an older version attaches correctly
   against subsystems added by a process running a newer version
 * set correct permissions on `/run/..`
 * a build whose schema is older than the pinned one no longer counts
   its state as current, so its single steps back off as well
 * add `interrupted()` on the lock guard, true when a replacement left
   its staged set or an old schema directory behind, a full pass
   replaces then
 * an attach checks after attaching that the interface still has the
   index of its pin, one recreated under the same name in between is
   reported as gone
 * a map missing from a pinned set is reported by name

v4, thanks @Stefan!:
 * drop the generation counter, a change takes the apply lock before it
   reads its input instead, so the lock order is the input order
 * new, the links of different subsystems on an interface are now
   ordered
 * the tc link plumbing is its own commit ahead of the subsystem code
 * subsystem programs are now a list of direction and name pairs
 * add short note for why not proxmox-sys's locking
 * improve tc error handling
 * fix smaller spacing and code stuff


proxmox-ebpf:

Hannes Laimer (5):
  tc: add the link plumbing
  subsystem: add the shared tc program handling
  subsystem: place the links of different subsystems in a fixed order
  tests: add a native harness for the BPF C programs
  debian: package the crate as a Rust library

 .gitignore                     |    1 +
 Cargo.toml                     |    7 +
 Makefile                       |   54 ++
 build.rs                       |   68 ++
 debian/changelog               |    5 +
 debian/control                 |   50 ++
 debian/copyright               |   26 +
 debian/debcargo.toml           |   13 +
 debian/source/format           |    1 +
 src/bpf-shim/bpf/bpf_endian.h  |   12 +
 src/bpf-shim/bpf/bpf_helpers.h |   34 +
 src/bpf-shim/bpf_debug.h       |   10 +
 src/bpf-shim/vmlinux.h         |   70 ++
 src/lib.rs                     |    3 +
 src/subsystem.rs               | 1146 ++++++++++++++++++++++++++++++++
 src/tc.rs                      |  323 +++++++++
 tests/common/mod.rs            |  207 ++++++
 tests/harness.rs               |   64 ++
 18 files changed, 2094 insertions(+)
 create mode 100644 Makefile
 create mode 100644 debian/changelog
 create mode 100644 debian/control
 create mode 100644 debian/copyright
 create mode 100644 debian/debcargo.toml
 create mode 100644 debian/source/format
 create mode 100644 src/bpf-shim/bpf/bpf_endian.h
 create mode 100644 src/bpf-shim/bpf/bpf_helpers.h
 create mode 100644 src/bpf-shim/bpf_debug.h
 create mode 100644 src/bpf-shim/vmlinux.h
 create mode 100644 src/subsystem.rs
 create mode 100644 src/tc.rs
 create mode 100644 tests/common/mod.rs
 create mode 100644 tests/harness.rs


Summary over all repositories:
  18 files changed, 2094 insertions(+), 0 deletions(-)

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