#!/usr/bin/env python3 """ NBD server v10 - PERC H710 corrected chunk translation + merged GDT overlay. Key fix over v9: all 5 chunks per stripe group contain filesystem data. The old formula used a 4-chunk stride between groups, making ~20% of blocks unreadable and shifting every address past group 0 by an accumulating error. Correct formula: phys = LV_START + group*5*CHUNK + chunk_idx*CHUNK + intra for ALL chunk_idx values 0-4. Usage: python3 build_merged_v2.py # rebuild /tmp/merged_gdt.bin python3 nbd_server_v10.py & nbd-client 127.0.0.1 10809 /dev/nbd0 -N "" mount -o ro /dev/nbd0 /mnt/fs """ import socket, struct, threading, sys, os DEV = '/dev/md0' MERGED_GDT = '/tmp/merged_gdt.bin' CHUNK_BYTES = 128 * 512 # 64 KB LV_PHYS_START = 5120000 * 512 VIRT_SIZE = 9365766144 * 512 BSIZE = 4096 GDT_ENTRY_SZ = 64 NUM_GROUPS = 35728 GDT_VIRT_START = BSIZE GDT_VIRT_END = BSIZE + NUM_GROUPS * GDT_ENTRY_SZ # 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 # Load merged GDT at startup print(f'Loading merged GDT from {MERGED_GDT}...') if not os.path.exists(MERGED_GDT): print(f'ERROR: {MERGED_GDT} not found. Run build_merged_v2.py first.') sys.exit(1) with open(MERGED_GDT, 'rb') as f: MERGED_GDT_DATA = f.read() expected = NUM_GROUPS * GDT_ENTRY_SZ if len(MERGED_GDT_DATA) != expected: print(f'ERROR: merged GDT is {len(MERGED_GDT_DATA)} bytes, expected {expected}') sys.exit(1) print(f'Merged GDT loaded: {len(MERGED_GDT_DATA)//1024}KB ({NUM_GROUPS} groups)') def raw_read(virt_offset, length): """PERC H710 chunk translation — all 5 chunks per group are filesystem data.""" 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 phys = (LV_PHYS_START + group * 5 * CHUNK_BYTES + chunk_idx * CHUNK_BYTES + intra) f.seek(phys) data = f.read(seg_len) result[dst_off:dst_off + len(data)] = data pos += seg_len remaining -= seg_len return result def read_virtual(virt_offset, length): """Read with merged GDT overlay over the primary GDT region only.""" data = raw_read(virt_offset, length) req_end = virt_offset + length if 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) 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() def main(): print('PERC H710 recovery NBD server v10') print(f' device : {DEV}') print(f' lv_start : byte {LV_PHYS_START}') print(f' virt_size : {VIRT_SIZE // 1024**3} GB') print(f' GDT region : bytes {GDT_VIRT_START}-{GDT_VIRT_END}') print(f' translation: group*5*CHUNK (all 5 chunks are filesystem data)') 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() while True: conn, addr = srv.accept() threading.Thread(target=handle_client, args=(conn, addr), daemon=True).start() if __name__ == '__main__': main()