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List:       busybox
Subject:    Not actually a network block device client yet.
From:       Rob Landley <rob () landley ! net>
Date:       2010-08-31 5:54:39
Message-ID: 201008310054.40297.rob () landley ! net
[Download RAW message or body]

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.c" (text/x-csrc)]

/* nbd-client

   Copyright 2010 Rob Landley <rob@landley.net> 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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