#!/usr/bin/env python3 """ NBD server v8 - PERC H710 chunk translation + on-the-fly patches: 1. Superblock: clear metadata_csum, gdt_csum, has_journal feature bits 2. GDT: zero all checksum fields in every group descriptor Nothing is written to disk. All patches applied in memory on reads. """ import socket, struct, threading DEV = '/dev/md0' CHUNK_BYTES = 128 * 512 LV_PHYS_START = 5120000 * 512 VIRT_SIZE = 9365766144 * 512 # Superblock location and fields SB_OFFSET = 1024 SB_SIZE = 1024 SB_COMPAT = 92 SB_INCOMPAT = 96 SB_RO_COMPAT = 100 SB_JNLINUM = 180 SB_CHECKSUM = 1020 INCOMPAT_HAS_JOURNAL = 0x004 COMPAT_HAS_JOURNAL = 0x004 RO_COMPAT_GDT_CSUM = 0x010 RO_COMPAT_METADATA_CSUM = 0x400 # GDT location and fields GDT_OFFSET = 4096 # block 1 GDT_ENTRY_SZ = 64 NUM_GROUPS = 35728 GDT_SIZE = NUM_GROUPS * GDT_ENTRY_SZ GDT_END = GDT_OFFSET + GDT_SIZE GDT_CSUM_OFF = 30 # checksum offset within each entry # NBD protocol 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 raw_read(virt_offset, length): """Pure chunk translation, no patching.""" 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) data = f.read(seg_len) result[dst_off:dst_off + len(data)] = data pos += seg_len remaining -= seg_len return result def patch_superblock(data, req_start): """ Patch superblock feature bits in a data buffer. req_start: virtual offset of data[0]. """ sb_start = SB_OFFSET sb_end = SB_OFFSET + SB_SIZE req_end = req_start + len(data) if req_start >= sb_end or req_end <= sb_start: return # no overlap # Offsets into data buffer def patch_u32(sb_field_off, mask_clear): buf_off = sb_start + sb_field_off - req_start if 0 <= buf_off <= len(data) - 4: val = struct.unpack_from('= GDT_END or req_end <= GDT_OFFSET: return # no overlap # First and last GDT entry indices that could overlap first_entry = max(0, (req_start - GDT_OFFSET) // GDT_ENTRY_SZ) last_entry = min(NUM_GROUPS - 1, (req_end - GDT_OFFSET - 1) // GDT_ENTRY_SZ) for g in range(first_entry, last_entry + 1): # Virtual offset of checksum field for group g csum_virt = GDT_OFFSET + g * GDT_ENTRY_SZ + GDT_CSUM_OFF buf_off = csum_virt - req_start if 0 <= buf_off <= len(data) - 2: struct.pack_into('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} in 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 v8') print(f' device : {DEV}') print(f' lv_start : byte {LV_PHYS_START}') print(f' virt_size : {VIRT_SIZE // 1024**3} GB') print(f' patches : superblock features + GDT checksums (on-the-fly)') 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(' fls /dev/nbd0 1585918') 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()