#!/usr/bin/env python3 """ NBD server — raw RAID0 striping from physical disks, bypassing mdadm. Opens /dev/sda, /dev/sde, /dev/sdd, /dev/sdc in read-only mode and implements RAID0 striping directly, then applies the ext4 chunk translation formula on top. This allows inspection of raw physical data without any mdadm layer. Disk order (RAID0): sda=0 sde=1 sdd=2 sdc=3 DISK_DATA_START: byte offset on each raw disk where the md0 data begins. Typically 0 for mdadm v0.90/v1.0, or 1048576 (2048 sectors) for v1.1/v1.2. Run: mdadm --examine /dev/sda | grep 'Data Offset' to determine the correct value before starting this server. Formula modes (--formula): v9 : 4-chunk groups, chunk_idx==4 skipped (original working formula) v10 : 5-chunk groups, all chunks readable (session-2 claim, unverified) raw : no ext4 translation — raw md0 byte space exposed directly (useful for hex inspection without any interpretation layer) Usage: # Determine disk data offset first: mdadm --examine /dev/sda | grep 'Data Offset' # Build merged GDT (uses md0 — run before switching): python3 build_merged_v2.py # Start raw server: python3 nbd_server_raw.py --formula v9 --disk-offset 1048576 nbd-client 127.0.0.1 10810 /dev/nbd1 -N "" mount -o ro /dev/nbd1 /mnt/raw """ import socket, struct, threading, sys, os, argparse # --- Disk layout ----------------------------------------------------------- DISKS = ['/dev/sda', '/dev/sde', '/dev/sdd', '/dev/sdc'] # disk index 0-3 NUM_DISKS = 4 CHUNK_BYTES = 128 * 512 # 64 KB # Where md0 byte 0 lives on each raw disk. # Default: 0 (mdadm v0.90/v1.0 with superblock at end). # For v1.1/v1.2 this is usually 1048576 (2048 sectors from disk start). # Override with --disk-offset on the command line. DEFAULT_DISK_DATA_START = 0 # --- Filesystem / LV layout ------------------------------------------------ LV_PHYS_START = 5120000 * 512 # byte offset of LV within md0 virtual space BSIZE = 4096 BPG = 32768 GDT_ENTRY_SZ = 64 NUM_GROUPS = 35728 GDT_VIRT_START = BSIZE GDT_VIRT_END = BSIZE + NUM_GROUPS * GDT_ENTRY_SZ MERGED_GDT_PATH = '/tmp/merged_gdt.bin' # Virtual size exposed over NBD (9365766144 * 512 bytes) VIRT_SIZE = 9365766144 * 512 # --- NBD protocol constants ------------------------------------------------ NBDMAGIC = 0x4e42444d41474943 IHAVEOPT = 0x49484156454F5054 REPLYMAGIC = 0x3e889045565a9 NBD_OPT_EXPORT_NAME = 1 NBD_OPT_ABORT = 2 NBD_OPT_LIST = 3 NBD_OPT_GO = 7 NBD_REP_ACK = 1 NBD_REP_SERVER = 2 NBD_REP_INFO = 3 NBD_REP_ERR_UNSUP = (1 << 31) | 1 NBD_INFO_EXPORT = 0 NBD_FLAG_HAS_FLAGS = 1 << 0 NBD_FLAG_READ_ONLY = 1 << 1 NBD_FLAG_SEND_FLUSH = 1 << 2 NBD_REQUEST_MAGIC = 0x25609513 NBD_REPLY_MAGIC = 0x67446698 NBD_CMD_READ = 0 NBD_CMD_DISC = 2 NBD_CMD_FLUSH = 3 TX_FLAGS = NBD_FLAG_HAS_FLAGS | NBD_FLAG_READ_ONLY | NBD_FLAG_SEND_FLUSH # Set by main() after arg parsing DISK_DATA_START = DEFAULT_DISK_DATA_START FORMULA = 'v9' DISK_FDS = [] # list of open file objects, index == disk index MERGED_GDT_DATA = b'' # --------------------------------------------------------------------------- # Raw RAID0 layer # --------------------------------------------------------------------------- def md0_read(md0_offset: int, length: int) -> bytearray: """Read `length` bytes starting at `md0_offset` in the virtual md0 space. Implements RAID0 striping: for each 64KB chunk, determine which physical disk it lives on and read from that disk at the appropriate offset. """ result = bytearray(length) pos = md0_offset remaining = length while remaining > 0: chunk_num = pos // CHUNK_BYTES intra = pos % CHUNK_BYTES disk_idx = chunk_num % NUM_DISKS chunk_on_disk = chunk_num // NUM_DISKS seg_len = min(CHUNK_BYTES - intra, remaining) dst_off = pos - md0_offset disk_byte = DISK_DATA_START + chunk_on_disk * CHUNK_BYTES + intra fd = DISK_FDS[disk_idx] fd.seek(disk_byte) data = fd.read(seg_len) result[dst_off:dst_off + len(data)] = data pos += seg_len remaining -= seg_len return result # --------------------------------------------------------------------------- # ext4 chunk translation layer (converts ext4 virt → md0 offset) # --------------------------------------------------------------------------- def ext4_to_md0_v9(virt_offset: int, length: int) -> bytearray: """v9 formula: 4-data-chunk groups; chunk_idx==4 reads as zeros.""" result = bytearray(length) pos = virt_offset remaining = length while remaining > 0: group = pos // (5 * CHUNK_BYTES) in_group = pos % (5 * CHUNK_BYTES) chunk_idx = in_group // CHUNK_BYTES intra = in_group % CHUNK_BYTES seg_len = min(CHUNK_BYTES - intra, remaining) dst_off = pos - virt_offset if chunk_idx != 4: md0_off = (LV_PHYS_START + group * 4 * CHUNK_BYTES + chunk_idx * CHUNK_BYTES + intra) chunk_data = md0_read(md0_off, seg_len) result[dst_off:dst_off + len(chunk_data)] = chunk_data # chunk_idx==4 → leave as zeros in result pos += seg_len remaining -= seg_len return result def ext4_to_md0_v10(virt_offset: int, length: int) -> bytearray: """v10 formula: all 5 chunks per group are data (no skip).""" result = bytearray(length) pos = virt_offset remaining = length while remaining > 0: group = pos // (5 * CHUNK_BYTES) in_group = pos % (5 * CHUNK_BYTES) chunk_idx = in_group // CHUNK_BYTES intra = in_group % CHUNK_BYTES seg_len = min(CHUNK_BYTES - intra, remaining) dst_off = pos - virt_offset md0_off = (LV_PHYS_START + group * 5 * CHUNK_BYTES + chunk_idx * CHUNK_BYTES + intra) chunk_data = md0_read(md0_off, seg_len) result[dst_off:dst_off + len(chunk_data)] = chunk_data pos += seg_len remaining -= seg_len return result def ext4_to_md0_raw(virt_offset: int, length: int) -> bytearray: """Raw mode: expose md0 directly, no ext4 chunk translation. virt_offset is treated as a byte offset within md0 (starting from 0, not from LV_START). Useful for raw hex inspection of md0 byte space. """ return md0_read(virt_offset, length) def raw_read(virt_offset: int, length: int) -> bytearray: if FORMULA == 'v9': return ext4_to_md0_v9(virt_offset, length) elif FORMULA == 'v10': return ext4_to_md0_v10(virt_offset, length) else: # raw return ext4_to_md0_raw(virt_offset, length) # --------------------------------------------------------------------------- # GDT overlay # --------------------------------------------------------------------------- def read_virtual(virt_offset: int, length: int) -> bytes: """Read with merged GDT overlay applied over the primary GDT region.""" data = raw_read(virt_offset, length) req_end = virt_offset + length if (FORMULA != 'raw' and MERGED_GDT_DATA and virt_offset < GDT_VIRT_END and req_end > GDT_VIRT_START): ol_start = max(virt_offset, GDT_VIRT_START) ol_end = min(req_end, GDT_VIRT_END) src_off = ol_start - GDT_VIRT_START dst_off = ol_start - virt_offset n = ol_end - ol_start data[dst_off:dst_off + n] = MERGED_GDT_DATA[src_off:src_off + n] return bytes(data) # --------------------------------------------------------------------------- # NBD protocol # --------------------------------------------------------------------------- def recv_all(conn, n): buf = b'' while len(buf) < n: d = conn.recv(n - len(buf)) if not d: raise ConnectionError('disconnected') buf += d return buf def send_reply(conn, opt, rtype, data=b''): conn.sendall(struct.pack('>Q', REPLYMAGIC)) conn.sendall(struct.pack('>I', opt)) conn.sendall(struct.pack('>I', rtype)) conn.sendall(struct.pack('>I', len(data))) if data: conn.sendall(data) def handle_client(conn, addr): print(f'[nbd] {addr} connected') try: conn.sendall(struct.pack('>Q', NBDMAGIC)) conn.sendall(struct.pack('>Q', IHAVEOPT)) conn.sendall(struct.pack('>H', 0x0003)) recv_all(conn, 4) while True: hdr = recv_all(conn, 16) _, opt, opt_len = struct.unpack('>QII', hdr) opt_data = recv_all(conn, opt_len) if opt_len else b'' if opt == NBD_OPT_EXPORT_NAME: conn.sendall(struct.pack('>Q', VIRT_SIZE)) conn.sendall(struct.pack('>H', TX_FLAGS)) break elif opt == NBD_OPT_GO: info = struct.pack('>HQH', NBD_INFO_EXPORT, VIRT_SIZE, TX_FLAGS) send_reply(conn, opt, NBD_REP_INFO, info) send_reply(conn, opt, NBD_REP_ACK) break elif opt == NBD_OPT_LIST: send_reply(conn, opt, NBD_REP_SERVER, struct.pack('>I', 0)) send_reply(conn, opt, NBD_REP_ACK) elif opt == NBD_OPT_ABORT: send_reply(conn, opt, NBD_REP_ACK) return else: send_reply(conn, opt, NBD_REP_ERR_UNSUP) print(f'[nbd] {addr} transmission') while True: hdr = recv_all(conn, 28) magic, flags, cmd, handle, offset, length = \ struct.unpack('>IHHQQI', hdr) if magic != NBD_REQUEST_MAGIC: return if cmd == NBD_CMD_READ: try: payload = read_virtual(offset, length) except Exception as e: print(f'[nbd] read error {offset}+{length}: {e}') payload = b'\x00' * length conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 0, handle)) conn.sendall(payload) elif cmd == NBD_CMD_FLUSH: conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 0, handle)) elif cmd == NBD_CMD_DISC: print(f'[nbd] {addr} disconnected') return else: conn.sendall(struct.pack('>IIQ', NBD_REPLY_MAGIC, 1, handle)) except (ConnectionError, BrokenPipeError, ConnectionResetError): print(f'[nbd] {addr} dropped') except Exception as e: print(f'[nbd] {addr} error: {e}') import traceback; traceback.print_exc() finally: conn.close() # --------------------------------------------------------------------------- # Startup / probe helpers # --------------------------------------------------------------------------- def probe_disk_offset(disk_data_start: int): """Sanity-check by reading what should be the FAT32 VBR. FAT32 VBR is at md0 sector 1664 (byte 851968). With RAID0: chunk_num=13, disk_idx=1 (sde), chunk_on_disk=3. Physical byte on sde = disk_data_start + 3*65536 + 0 = disk_data_start + 196608 """ # md0 byte 851968 is FAT32 VBR fat_md0 = 851968 chunk_num = fat_md0 // CHUNK_BYTES intra = fat_md0 % CHUNK_BYTES disk_idx = chunk_num % NUM_DISKS chunk_on_disk = chunk_num // NUM_DISKS disk_byte = disk_data_start + chunk_on_disk * CHUNK_BYTES + intra fd = DISK_FDS[disk_idx] fd.seek(disk_byte) sig = fd.read(3) disk_name = DISKS[disk_idx] if len(sig) >= 2 and sig[0] in (0xEB, 0xFA, 0xE9): print(f' [probe] FAT32/boot-sector signature found at {disk_name}:' f'{disk_byte} — disk-offset looks correct') return True else: print(f' [probe] FAT32 signature NOT found at {disk_name}:{disk_byte}' f' (got {sig.hex()}) — disk-offset may be wrong') return False def main(): global DISK_DATA_START, FORMULA, DISK_FDS, MERGED_GDT_DATA parser = argparse.ArgumentParser(description='Raw-disk RAID0 NBD server') parser.add_argument('--formula', choices=['v9', 'v10', 'raw'], default='v9', help='ext4 chunk translation: v9 (4-chunk skip), ' 'v10 (5-chunk all), raw (no translation, expose md0)') parser.add_argument('--disk-offset', type=int, default=DEFAULT_DISK_DATA_START, metavar='BYTES', help='byte offset on each raw disk where md0 data begins ' '(run: mdadm --examine /dev/sda | grep "Data Offset")') parser.add_argument('--port', type=int, default=10810, help='TCP port to listen on (default 10810)') parser.add_argument('--no-gdt-overlay', action='store_true', help='disable merged GDT overlay') parser.add_argument('--probe', action='store_true', help='probe disk-offset via FAT32 VBR signature and exit') args = parser.parse_args() DISK_DATA_START = args.disk_offset FORMULA = args.formula # Open all disks read-only print('Opening raw disks (read-only)...') for path in DISKS: try: fd = open(path, 'rb') DISK_FDS.append(fd) print(f' {path} : OK') except PermissionError: print(f' {path} : PERMISSION DENIED — run as root') sys.exit(1) except FileNotFoundError: print(f' {path} : NOT FOUND') sys.exit(1) if args.probe: probe_disk_offset(DISK_DATA_START) for fd in DISK_FDS: fd.close() sys.exit(0) # Load merged GDT (optional) if not args.no_gdt_overlay: if os.path.exists(MERGED_GDT_PATH): with open(MERGED_GDT_PATH, 'rb') as f: MERGED_GDT_DATA = f.read() expected = NUM_GROUPS * GDT_ENTRY_SZ if len(MERGED_GDT_DATA) == expected: print(f'Merged GDT loaded: {len(MERGED_GDT_DATA)//1024}KB') else: print(f'WARNING: merged GDT size mismatch ' f'({len(MERGED_GDT_DATA)} vs {expected}), skipping overlay') MERGED_GDT_DATA = b'' else: print(f'NOTE: {MERGED_GDT_PATH} not found, GDT overlay disabled') # Probe sanity check (non-fatal) print('Probing disk-offset sanity...') probe_disk_offset(DISK_DATA_START) print() print('PERC H710 recovery NBD server — raw disk mode') print(f' disks : {" ".join(DISKS)}') print(f' disk-offset : {DISK_DATA_START} bytes ({DISK_DATA_START//512} sectors)') print(f' formula : {FORMULA}') print(f' virt_size : {VIRT_SIZE // 1024**3} GB') print(f' GDT overlay : {"yes" if MERGED_GDT_DATA else "no"}') print() srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM) srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) srv.bind(('127.0.0.1', args.port)) srv.listen(5) print(f'Listening on 127.0.0.1:{args.port}') print(f' nbd-client 127.0.0.1 {args.port} /dev/nbd1 -N ""') print() while True: conn, addr = srv.accept() threading.Thread(target=handle_client, args=(conn, addr), daemon=True).start() if __name__ == '__main__': main()