feat: full NFSv4.2 server and client in pure Go

Assisted-by: GLM 5.3 Flash

CHANGELOG.md

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+# Changelog
+
+All notable changes to **nfs** are documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and
+this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [development]
+
+### Added
+
+-
+
+## [1.0.0] - 2026-09-21
+
+### Added
+
+The first release of a full NFSv4.2 implementation in pure Go: server and client,
+minor version 2 on the wire only, no portmapper, no mountd, no separate locking
+protocol.
+
+- **Wire foundation**: the XDR codec of RFC 4506, ONC RPC record marking of
+  RFC 5531 with fragment reassembly, the call and reply headers, AUTH_SYS, and
+  the NFSv4.2 operation, error and attribute numbers verified against the
+  standards and the Linux client header.
+- **Stateless operations**: PUTROOTFH, PUTFH, SAVEFH, RESTOREFH, GETFH, LOOKUP,
+  LOOKUPP, PUTPUBFH, GETATTR, ACCESS, READ, READDIR, WRITE, CREATE, REMOVE,
+  RENAME, SETATTR, LINK, READLINK, COMMIT, VERIFY, NVERIFY, SECINFO and
+  SECINFO_NO_NAME, over a virtual filesystem with a local directory backend.
+- **Sessions**: EXCHANGE_ID, CREATE_SESSION, DESTROY_SESSION, BIND_CONN_TO_SESSION
+  and SEQUENCE with a slot table, a reply cache per slot, and client reboot
+  detection that drops the state of the previous life.
+- **Open state**: OPEN and CLOSE with real stateids, share reservations enforced
+  across opens of the same file, OPEN_DOWNGRADE, and regular file creation
+  through the unchecked, guarded and exclusive forms, where an exclusive create
+  replays by its verifier.
+- **Ownership**: every object a client creates carries the identity the client
+  presented, and the server answers the owner and owner group of every object,
+  so ownership reads correctly on any conformant client.
+- **Byte range locking**: LOCK, LOCKT and LOCKU with per owner conflict
+  detection, range splitting on unlock, and RELEASE_LOCKOWNER.
+- **Lease and recovery**: lease renewal on every SEQUENCE, DESTROY_CLIENTID,
+  RECLAIM_COMPLETE inside the grace window, CLAIM_PREVIOUS reclamation, and
+  persistent file handle maps that survive a server restart.
+- **Delegations**: read and write delegations granted on the only open of a
+  file, recalled over the back channel on a conflicting open, returned through
+  DELEGRETURN.
+- **Directory delegations**: GET_DIR_DELEGATION with CB_NOTIFY on create,
+  rename and remove, and CB_NOTIFY_LOCK when a released range frees a denied
+  lock.
+- **Back channel**: CB_COMPOUND over the same TCP connection, CB_SEQUENCE,
+  CB_RECALL, and callback delivery that the client demultiplexes from replies.
+- **Optional operations of RFC 7862**: SEEK, ALLOCATE, DEALLOCATE, IO_ADVISE,
+  READ_PLUS, WRITE_SAME, COPY, CLONE, COPY_NOTIFY, OFFLOAD_CANCEL,
+  OFFLOAD_STATUS, LAYOUTERROR and LAYOUTSTATS.
+- **Extended attributes**: GETXATTR, SETXATTR, LISTXATTR and REMOVEXATTR of
+  RFC 8276 over the user namespace of the local backend.
+- **Named attributes**: OPENATTR with create, lookup, read, write and remove
+  over the synthetic attribute directory of an object.
+- **pNFS**: the metadata server role with LAYOUTGET, LAYOUTCOMMIT,
+  LAYOUTRETURN, GETDEVICEINFO and GETDEVICELIST, and layout bodies for
+  flexfiles (RFC 8435), files, block volumes, objects and SCSI, all over one
+  emulated device that is the metadata server itself. The flexfiles version 2
+  body of draft-haynes-nfsv4-flex-filesv2-00 (layout type 0x6) is served the
+  same way.
+- **Migration and referrals**: the fs_locations and fs_locations_info
+  attributes, referral stubs whose other operations answer NFS4ERR_MOVED.
+- **Kerberos**: RPCSEC_GSS with the krb5, krb5i and krb5p service levels, the
+  AES profiles of RFC 3961 and RFC 3962 and the tokens of RFC 4121 implemented
+  in pure Go, plus the version three credential of RFC 7861 with CREATE, LIST
+  and assertion binding.
+- **RPC-with-TLS**: the AUTH_TLS probe and in place TLS upgrade of RFC 9289.
+- **RPC-over-RDMA framing**: the chunk lists and message assembly of RFC 8166
+  over a stream transport; the verbs transport itself sits outside pure Go.
+- **The nfsd command**: the `-export` directory and the `-addr` listen
+  address, a TOML configuration file through `-config` carrying the listen
+  address, the operation log, the state directory, the connection cap, the
+  TLS key pair and one `[[export]]`, with the flags overriding the file and a
+  broken file ending the start up with the file and the line named; a read
+  only export with `-ro`; RPC-with-TLS through `-tls-cert` and `-tls-key`,
+  where a client that skips STARTTLS is refused with auth too weak for every
+  procedure but the NULL of the probe; the operation log of `-log-ops`; the
+  connection cap of `-max-connections`; persistent recovery state through
+  `-state-dir`, where file handles and opens are written as they change, a
+  restart loads them back and the grace window lets clients reclaim their
+  opens with CLAIM_PREVIOUS; root squash with `-root-squash` or `root-squash`
+  in the export, mapping a client claiming uid 0 onto nobody (65534);
+  `READY=1` on $NOTIFY_SOCKET once the listener is up, so a `Type=notify`
+  unit starts on real readiness; version reporting; and a clean shutdown on
+  SIGINT and SIGTERM.
+- **The nfs command**: ls, cat, put, get, rm, mkdir and stat against a running
+  server; the whole operation matrix as `nfs selftest`, one line per check
+  plus a summary and a nonzero exit when a check fails; transfers spread over
+  several session slots with `-concurrency`, measured on loopback at a 64 MiB
+  put dropping from 77 ms sequential to 32 ms at four; a session owner id
+  unique to the process, so two clients of the command beside each other are
+  two clients, not one rebooting; and the version report.
+- **Kernel interop**: the server is verified end to end against the Linux
+  kernel NFSv4.2 client, which mounts the tree over `mount -t nfs4` and reads,
+  writes, creates and removes through it, with correct ownership, as root and
+  non root callers alike.
+- **Interoperability stance**: strict conformance as the rule, a documented
+  tolerance layer confined to the deviations of real clients, and the server
+  and client pair as the strict reference of the stack.
+- **Performance**: the server answers a COMPOUND from one buffer instead of
+  copying every operation result twice, READ fills the reply in place, WRITE
+  hands the request's own bytes to the storage and the wire buffers recycle;
+  the local backend keeps open descriptors of regular files in a bounded
+  cache and revalidates the file identity on every use; READDIR pages cost
+  the page against a cached sorted order of the directory; COPY and CLONE run
+  through copy_file_range and the reflink of the filesystem with a fallback
+  to the userspace copy; the session store locks per session instead of one
+  server wide mutex and the lease check runs lock free against an atomic
+  renewal stamp, six clients beside each other measured at 4.8 times the
+  sequential throughput. Measured numbers: 11 percent faster reads, 19
+  percent fewer allocations per COMPOUND, 27 percent fewer bytes per read,
+  16.9 percent faster reads and 11.0 percent faster writes of 64 KiB chunks,
+  and a READDIR page of 64 entries in a 10 000 entry directory measured 30
+  times faster; the reports live in docs/_results/.
+- **Operations**: docs/DEPLOYMENT.md carries the production picture, the
+  hardened systemd unit with Type=notify and the two capability model, the
+  firewall note and the upgrade and monitoring story; docs/CONFIGURATION.md
+  lists every configuration key; docs/BENCHMARKING.md states the measurement
+  method.
+- **Platforms**: Linux on amd64, arm64, loong64 and riscv64; FreeBSD, OpenBSD
+  and NetBSD on amd64 and arm64, all three verified live on amd64, OpenBSD
+  and NetBSD with both ends of the project running inside the system and
+  across to the Linux server because their kernel clients speak only NFSv3;
+  darwin on arm64 as a cross compiled build without runtime testing. Extended
+  attributes and the sparse operations answer not supported on OpenBSD,
+  NetBSD and darwin, whose local backends have no system interface an
+  arbitrary attribute name could use. The stack is pure Go end to end, and
+  the module ships the two commands only: there is no importable package and
+  no library surface.