feat(sftp): add SFTPv3 protocol support (#2875)

Co-authored-by: houseme <housemecn@gmail.com>

crates/config/src/constants/protocols.rs

@@ -57,3 +57,106 @@ pub const ENV_WEBDAV_CERTS_DIR: &str = "RUSTFS_WEBDAV_CERTS_DIR";
 pub const ENV_WEBDAV_CA_FILE: &str = "RUSTFS_WEBDAV_CA_FILE";
 pub const ENV_WEBDAV_MAX_BODY_SIZE: &str = "RUSTFS_WEBDAV_MAX_BODY_SIZE";
 pub const ENV_WEBDAV_REQUEST_TIMEOUT: &str = "RUSTFS_WEBDAV_REQUEST_TIMEOUT";
+
+/// Default SFTP server bind address.
+pub const DEFAULT_SFTP_ADDRESS: &str = "0.0.0.0:2222";
+
+/// Default for SFTP host-key directory. None means no default. Operators
+/// must set RUSTFS_SFTP_HOST_KEY_DIR explicitly when SFTP is enabled.
+pub const DEFAULT_SFTP_HOST_KEY_DIR: Option<&str> = None;
+
+/// SFTP environment variable names.
+pub const ENV_SFTP_ENABLE: &str = "RUSTFS_SFTP_ENABLE";
+pub const ENV_SFTP_ADDRESS: &str = "RUSTFS_SFTP_ADDRESS";
+pub const ENV_SFTP_HOST_KEY_DIR: &str = "RUSTFS_SFTP_HOST_KEY_DIR";
+pub const ENV_SFTP_IDLE_TIMEOUT: &str = "RUSTFS_SFTP_IDLE_TIMEOUT";
+/// S3 multipart part size in bytes. Default DEFAULT_SFTP_PART_SIZE (16 MiB).
+/// Valid range 5 MiB to 5 GiB (S3 protocol bounds), enforced at startup.
+///
+/// The per-upload size ceiling is part_size * 10_000 (the S3 parts cap),
+/// so the default caps single uploads at 160 GiB. Deployments expecting
+/// larger single files must raise this: 64 MiB -> 640 GiB, 128 MiB ->
+/// 1.25 TiB, 512 MiB -> 5 TiB (S3 object max). Rename is not affected;
+/// multipart_copy scales the per-part size dynamically and handles up
+/// to the 5 TiB S3 object limit regardless of this setting.
+pub const ENV_SFTP_PART_SIZE: &str = "RUSTFS_SFTP_PART_SIZE";
+pub const ENV_SFTP_READ_ONLY: &str = "RUSTFS_SFTP_READ_ONLY";
+pub const ENV_SFTP_BANNER: &str = "RUSTFS_SFTP_BANNER";
+/// Optional environment variable. If RUSTFS_SFTP_HANDLES_PER_SESSION
+/// is not set in the process environment, the server uses the default
+/// of 64 handles per session and emits no warning. If set, the value
+/// must be in the inclusive range 8 to 1024. Out-of-range values fall
+/// back to the default of 64 with a warn-level log naming the
+/// requested value and the bounds.
+///
+/// Caps the maximum number of simultaneously-open SFTP handles per
+/// session. A handle is the server-side identifier returned by
+/// SSH_FXP_OPEN and SSH_FXP_OPENDIR. One client typically uses one
+/// handle per file in flight plus one per directory listing.
+/// Operators running clients with deep pipelining may raise this.
+pub const ENV_SFTP_HANDLES_PER_SESSION: &str = "RUSTFS_SFTP_HANDLES_PER_SESSION";
+
+/// Optional environment variable. If RUSTFS_SFTP_BACKEND_OP_TIMEOUT_SECS
+/// is not set in the process environment, the server uses the default
+/// of 60 seconds and emits no warning. If set, the value must be in
+/// the inclusive range 5 to 600 seconds. Out-of-range values fall
+/// back to the default with a warn-level log naming the requested
+/// value and the bounds.
+///
+/// Bounds every storage backend call issued by the SFTP driver. A
+/// backend that does not respond within this many seconds returns
+/// Failure to the client and emits a warn log naming the backend
+/// method. This catches a backend that accepted the request and never
+/// returned a body, which the SSH keepalive cannot detect because the
+/// transport itself remains live.
+pub const ENV_SFTP_BACKEND_OP_TIMEOUT_SECS: &str = "RUSTFS_SFTP_BACKEND_OP_TIMEOUT_SECS";
+
+/// Optional environment variable. If RUSTFS_SFTP_READ_CACHE_WINDOW_BYTES
+/// is not set in the process environment, the server uses a 4 MiB
+/// default and emits no warning. If set, the value must be in the
+/// inclusive range MAX_READ_LEN (256 KiB) to 64 MiB. Out-of-range
+/// values fall back to the default with a warn-level log naming the
+/// requested value and the bounds.
+///
+/// Per-handle byte window the SFTP read path fetches in one backend
+/// call on a cache miss. Subsequent FXP_READs within that window are
+/// served from the buffer without a backend round trip. For
+/// sequential downloads the backend round-trip count drops by
+/// window_bytes / MAX_READ_LEN. Random-access workloads should set
+/// the window equal to MAX_READ_LEN to opt out of read-ahead.
+pub const ENV_SFTP_READ_CACHE_WINDOW_BYTES: &str = "RUSTFS_SFTP_READ_CACHE_WINDOW_BYTES";
+
+/// Optional environment variable. If
+/// RUSTFS_SFTP_READ_CACHE_TOTAL_MEM_BYTES is not set in the process
+/// environment, the server uses a 256 MiB default and emits no
+/// warning. If set, the value must be at least 16 MiB. Below-min
+/// values fall back to the default with a warn-level log naming the
+/// requested value and the bound.
+///
+/// Process-wide ceiling on cumulative read cache memory across every
+/// live SFTP handle. Once the accumulator plus a new window would
+/// exceed this value, the populate call on the per-handle cache is
+/// skipped. The read still completes from the freshly-fetched bytes
+/// without storing them in the cache, at the cost of one backend
+/// call per FXP_READ. High-concurrency deployments expecting many
+/// parallel downloads should raise this in step with the per-session
+/// handle cap.
+pub const ENV_SFTP_READ_CACHE_TOTAL_MEM_BYTES: &str = "RUSTFS_SFTP_READ_CACHE_TOTAL_MEM_BYTES";
+
+/// Default idle session timeout in seconds.
+pub const DEFAULT_SFTP_IDLE_TIMEOUT: u64 = 600;
+
+/// Default S3 multipart upload part size in bytes (16 MiB).
+///
+/// The per-upload size ceiling is part_size * 10_000 (the S3 parts cap),
+/// so the default gives a 160 GiB single-upload limit. Deployments that
+/// expect single files larger than this must raise part_size:
+/// 64 MiB -> 640 GiB, 128 MiB -> 1.25 TiB, 512 MiB -> 5 TiB (S3 max).
+/// The minimum is 5 MiB and the maximum is 5 GiB (S3 protocol bounds).
+pub const DEFAULT_SFTP_PART_SIZE: u64 = 16_777_216;
+
+/// Default read-only mode (disabled).
+pub const DEFAULT_SFTP_READ_ONLY: bool = false;
+
+/// Default SSH identification string (no version disclosure).
+pub const DEFAULT_SFTP_BANNER: &str = "SSH-2.0-RustFS";