docs: guides reflect verified NAT/redirect/divert/pflog and the fixed state listing; CHANGELOG for v0.4.0

CHANGELOG.md

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+# Changelog
+
+## v0.4.0 — 2026-11-11
+
+Lab-verified milestone release.  The full gate suite (9 gates) runs against
+Alpine VMs under libvirt on the kernel built from source.
+
+### Verified in the lab (each has a gate in `tests/vm/`)
+
+| Capability | Gate | What it proves |
+|---|---|---|
+| Engine loads, `/dev/pf`, real OpenBSD `pfctl` over the ioctl ABI | `01` | `insmod` + `pfctl -s info` + transit ping + state created |
+| `block` / `return` / `return-rst` | `02` | ICMP dropped, TCP refused |
+| `pfr` tables (inline `{ }`, `-T add/del/show`, `-T` block) | `03` | table load, block by table, delete, unblock |
+| Anchors and evaluation order | `04` | anchor child passes the request before the parent `block`, state created by the anchor rule, request dropped after the anchor is flushed |
+| `nat-to` (source NAT) | `05` | tcpdump proof of the rewritten source, reply de-NATed, state shows both tuples |
+| `rdr-to` (port redirect) | `06` | client talks to the firewall, server answers, **2 MB pulled through the redirect byte-identical**, firewall still responsive afterwards |
+| `divert-to` + `AF_DIVERT` + `pdivert` | `11` | drop with no listener (BSD `divs_noport` parity), packet delivered to userspace, rewritten and reinjected |
+| `pflog` + `pflogd` | `12` | logged packets read from `/dev/pflog` and written as a `DLT_PFLOG` pcap containing the real bytes |
+| Soak / unload discipline | `14` | traffic + states with no kernel warnings, clean `rmmod`, reload, no slab growth |
+
+### Added
+
+- `module/pfsrc/pfk_pflog.c` — `/dev/pflog` chardev backend (OpenBSD
+  `pflog_hdr` layout, 64-byte records, bounded queue, `poll`, stats ioctl).
+- `tools/pflogd` — reads `/dev/pflog`, writes `DLT_PFLOG` pcap (or a readable
+  one-line-per-record summary).
+- `tools/pdivert` — divert(4) relay with payload mutation + ICMP checksum fix.
+- `module/pfsrc/divert_sock.c` — `AF_DIVERT` socket family registered at
+  runtime (`PF_DIVERT = 32`, `IPPROTO_DIVERT = 254`), blocking `recvmsg`,
+  `poll`, BSD-compatible reinjection.
+- `scripts/demo-session.sh` + `scripts/demo-record.py` + `make demo` —
+  asciinema recording of the live lab (`out/demo-pf-linux.cast`).
+- `docs/{en,pt-BR}/`: README, install, build, guide, vm-lab, feature-matrix,
+  patches, caveats, demo.  `docs/porting-notes.md` records every deviation.
+- `patches/kernel/` + `scripts/apply-patches.sh` / `scripts/unpatch.sh` —
+  kernel-core patch mechanism, empty series by design (verified: the module
+  needs no core patch).
+
+### Fixed (all found by the VM gates, root causes documented)
+
+- `skb->mark` bookkeeping used multi-bit values, so the "in pass done" mark
+  also satisfied the "out pass done" test: transit traffic never reached the
+  **out** ruleset (NAT and egress rules silently ignored).
+- The out ruleset was never evaluated for forwarded packets: added the
+  `NF_INET_FORWARD` hook (OpenBSD evaluates it in `ip_forward()`).
+- `refcnt_rele()` had inverted polarity → live state keys freed → `Oops` in
+  the state RBT and `pfctl -s states` hangs.
+- `radix` `SALEN()` read the `sa_family` byte as a length (Linux sockaddrs
+  have no `sa_len`) → table entries dropped as duplicates.
+- BSD/Linux `LIST_HEAD` macro arity clash in `compat/sys/queue.h`.
+- Reverse NAT: a packet whose destination pf rewrote was delivered to the
+  firewall's own stack instead of being re-routed.
+- Checksums across translation: IP header checksum recomputed (OpenBSD's
+  `ip_output` does this, Linux does not); transport checksum recomputed in
+  software for plain skbs and handed back to the NIC (`CHECKSUM_PARTIAL`) for
+  GSO/TSO — the earlier software-only fix corrupted every segment after the
+  first and stalled bulk transfers.
+- `divert`: NULL dereference on an empty listener list (wedged the VM),
+  port byte order mismatch between `bind` and the queue, L3-only skbs injected
+  into an Ethernet device RX path, re-divert loop (solved with a skip mark).
+- `IOC_SIZEBITS` = 14 truncated the rule ioctl struct → `EINVAL` on load.
+- State iteration started at id 1 (kifs never attached), `stoeplitz_init()`
+  never called, purge timer re-arming itself at `rmmod`, `rtnl`×`NET` lock
+  order inversion in the interface notifier.
+
+### Known gaps
+
+`binat-to`, `route-to`/`dup-to`/`fail-to`, `af-to`, scrub end-to-end
+(normalization code is ported and compiles; the lab gate is not written),
+queues/ALTQ (`hfsc.c`/`fq_codel.c` staged, `pfq` qdisc not implemented),
+`pfsync`/CARP (out of scope).  See `docs/en/feature-matrix.md`.
+
+## v0.3.0 — 2026-11-11
+
+M2 data path: netisr-style workqueue, per-direction marks, state/table/anchor
+gates passing; divert design settled (in-module socket family, no core patch).
+
+## v0.2.0 — 2026-11-11
+
+M1: engine compiles into `pf.ko` (pf.c, pf_ioctl.c with the full ioctl ABI,
+pf_norm, pf_if, pf_lb, pf_table, pf_ruleset, pf_osfp, pf_syncookies, radix,
+md5/sha, ifq), `/dev/pf`, Linux-built OpenBSD `pfctl` talking to it.
+
+## v0.1.0 — 2026-11-11
+
+M0: repo, bilingual scaffold, kernel 7.3.4 build, libvirt Alpine lab with
+custom-kernel VMs (pf0/cli/srv/gw2), build/deploy/test scripts.