At the "It compiled, I wonder if it runs?" stage. Haven't got an NBD server lying around to plug it into, but I thought I'd post it before going to bed. (Not yet busyboxified, just sort of standalone. And still kind of ugly.)
FYI, Rob -- GPLv3: as worthy a successor as The Phantom Menace, as timely as Duke Nukem Forever, and as welcome as New Coke.
/* nbd-client Copyright 2010 Rob Landley <[email protected]> Licensed under GPLv2 Usage: nbd-client HOST PORT DEVICE [-sSpn] [-b BLOCK_SIZE] [-t TIMEOUT] [-N name] -s swap -S sdp -p persist -n nofork -d DEVICE -c DEVICE */ #include <errno.h> #include <fcntl.h> #include <limits.h> #include <netdb.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <netinet/tcp.h> #include <sys/ioctl.h> #include <sys/mount.h> #include <sys/types.h> #include <sys/socket.h> #include <sys/stat.h> #define NBD_SET_SOCK _IO(0xab, 0) #define NBD_SET_BLKSIZE _IO(0xab, 1) #define NBD_SET_SIZE _IO(0xab, 2) #define NBD_DO_IT _IO(0xab, 3) #define NBD_CLEAR_SOCK _IO(0xab, 4) #define NBD_CLEAR_QUEUE _IO(0xab, 5) #define NBD_PRINT_DEBUG _IO(0xab, 6) #define NBD_SET_SIZE_BLOCKS _IO(0xab, 7) #define NBD_DISCONNECT _IO(0xab, 8) #define NBD_SET_TIMEOUT _IO(0xab, 9) #if __BYTE_ORDER == __LITTLE_ENDIAN #include <byteswap.h> #define SWAP_BE32(x) __bswap_32(x) #define SWAP_BE64(x) __bswap_64(x) #else #define SWAP_BE32(x) (x) #define SWAP_BE64(x) (x) #endif int main(int argc, char *argv[]) { int sock, nbd, flags; unsigned long timeout = 0; struct addrinfo *addr, *p; char *host=argv[1], *port=argv[2], *device=argv[3]; uint64_t devsize; char data[124]; // Parse command line stuff (just a stub now) if (argc != 4) { fprintf(stderr, "Usage: nbd-client HOST PORT DEVICE\n"); exit(1); } // Make sure the /dev/nbd exists. if (0>(nbd = open(device, O_RDWR))) { fprintf(stderr, "Can't open '%s'\n", device); exit(1); } // Repeat until spanked for (;;) { int temp; // Find and connect to server if (getaddrinfo(host, port, NULL, &addr)) addr = 0; for (p = addr; p; p = p->ai_next) { sock = socket(p->ai_family, p->ai_socktype, p->ai_protocol); if (-1 != connect(sock, p->ai_addr, p->ai_addrlen)) break; } freeaddrinfo(addr); if (!p) { fprintf(stderr, "Can't connect '%s' port '%s'\n", host, port); exit(1); } temp = 1; setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &temp, sizeof(int)); // Log on to the server. (Todo: one big 8+8+8+4+124=152 read) if (read(sock, data, 8) != 8 || memcmp(data, "NBDMAGIC", 8) || read(sock, &devsize, 8) != 8 || SWAP_BE64(devsize) != 0x420281861253LL || read(sock, &devsize, 8) != 8 || read(sock, &flags, 4) != 4 || read(sock, data, 124) != 124) { fprintf(stderr, "Login fail\n"); exit(1); } devsize = SWAP_BE64(devsize); flags = SWAP_BE32(flags); // Set 4k block size. Everything uses that these days. ioctl(nbd, NBD_SET_BLKSIZE, 4096); ioctl(nbd, NBD_SET_SIZE_BLOCKS, devsize/4096); ioctl(nbd, NBD_CLEAR_SOCK); // If the sucker was exported read only, respect that locally. temp = (flags & 2) ? 1 : 0; if (ioctl(nbd, BLKROSET, &temp)<1) { fprintf(stderr, "Login fail\n"); exit(1); } if (timeout && ioctl(nbd, NBD_SET_TIMEOUT, timeout)<0) break; if (ioctl(nbd, NBD_SET_SOCK, sock) < 0) break; // if (swap) mlockall(MCL_CURRENT|MCL_FUTURE); // Open the device to force reread of the partition table. if (!fork()) { char *s = strrchr(device, '/'); sprintf(data, "/sys/block/%.32s/pid", s ? s+1 : device); // Is it up yet? for (;;) { temp = open(data, O_RDONLY); if (temp == -1) sleep(1); else { close(temp); break; } } close(open(device, O_RDONLY)); exit(0); } // Daemonize here. // Process NBD requests until further notice. if (ioctl(nbd, NBD_DO_IT)>=0 || errno==EBADR) break; close(sock); close(nbd); } // Flush queue and exit. ioctl(nbd, NBD_CLEAR_QUEUE); ioctl(nbd, NBD_CLEAR_SOCK); exit(0); }
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