#!/usr/bin/env python3 """ NBD server v5 — minimal PERC H710 chunk translation only. Simply reproduces what the PERC controller presented to the OS: - Skip every 5th 64KB chunk (PERC internal metadata) - Serve the result as a read-only block device No superblock patching. No GDT synthesis. The filesystem was written correctly through the PERC's translation — reading it back the same way should give a valid filesystem. Usage: python3 nbd_server_v5.py & nbd-client 127.0.0.1 10809 /dev/nbd0 -N "" mount -o ro,norecovery -t ext4 /dev/nbd0 /mnt/root """ import socket import struct import threading DEV = '/dev/md0' CHUNK_BYTES = 128 * 512 # 64 KB per chunk LV_PHYS_START = 5120000 * 512 # byte 2,621,440,000 VIRT_SIZE = 9365766144 * 512 # from superblock block count # NBD newstyle 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 def read_virtual(virt_offset, length): """ Read length bytes from the virtual address space. Applies PERC chunk translation: every 5th 64KB chunk is skipped (it contained PERC internal metadata and is not part of user data). Skipped chunks return zeros. """ result = bytearray(length) pos = virt_offset remaining = length with open(DEV, 'rb') as f: 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: phys = (LV_PHYS_START + group * 4 * CHUNK_BYTES + chunk_idx * CHUNK_BYTES + intra) f.seek(phys) chunk = f.read(seg_len) result[dst_off:dst_off + len(chunk)] = chunk # chunk_idx == 4: leave as zeros (PERC metadata, not user data) pos += seg_len remaining -= seg_len return bytes(result) def recv_all(conn, n): buf = b'' while len(buf) < n: data = conn.recv(n - len(buf)) if not data: raise ConnectionError('client disconnected') buf += data 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: # Handshake conn.sendall(struct.pack('>Q', NBDMAGIC)) conn.sendall(struct.pack('>Q', IHAVEOPT)) conn.sendall(struct.pack('>H', 0x0003)) # FIXED_NEWSTYLE | NO_ZEROES recv_all(conn, 4) # client flags # Option haggling 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: name = b'' send_reply(conn, opt, NBD_REP_SERVER, struct.pack('>I', 0) + name) 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 phase ({VIRT_SIZE//1024//1024//1024}GB)') # Transmission while True: hdr = recv_all(conn, 28) magic, flags, cmd, handle, offset, length = \ struct.unpack('>IHHQQI', hdr) if magic != NBD_REQUEST_MAGIC: print(f'[nbd] bad magic 0x{magic:08x}') 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} disconnect') 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() def main(): print(f'PERC H710 recovery NBD server v5 (minimal)') print(f' device : {DEV}') print(f' lv_start : byte {LV_PHYS_START} (sector {LV_PHYS_START//512})') print(f' virt_size : {VIRT_SIZE//1024//1024//1024} GB') print(f' chunk : {CHUNK_BYTES//1024} KB, every 5th skipped') 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', 10809)) srv.listen(5) print('Listening on 127.0.0.1:10809') print(' nbd-client 127.0.0.1 10809 /dev/nbd0 -N ""') print(' mount -o ro,norecovery -t ext4 /dev/nbd0 /mnt/root') print() while True: conn, addr = srv.accept() threading.Thread(target=handle_client, args=(conn, addr), daemon=True).start() if __name__ == '__main__': main()