nbd-client.c

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/*
 * Open connection for network block device
 *
 * Copyright 1997,1998 Pavel Machek, distribute under GPL
 *  <pavel@atrey.karlin.mff.cuni.cz>
 * Copyright (c) 2002 - 2011 Wouter Verhelst <w@uter.be>
 *
 * Version 1.0 - 64bit issues should be fixed, now
 * Version 1.1 - added bs (blocksize) option (Alexey Guzeev, aga@permonline.ru)
 * Version 1.2 - I added new option '-d' to send the disconnect request
 * Version 2.0 - Version synchronised with server
 * Version 2.1 - Check for disconnection before INIT_PASSWD is received
 *      to make errormsg a bit more helpful in case the server can't
 *      open the exported file.
 * 16/03/2010 - Add IPv6 support.
 *      Kitt Tientanopajai <kitt@kitty.in.th>
 *      Neutron Soutmun <neo.neutron@gmail.com>
 *      Suriya Soutmun <darksolar@gmail.com>
 */

#include "config.h"
#include "lfs.h"

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h>
#include <unistd.h>
#include <netinet/tcp.h>
#include <netinet/in.h>
#include <netdb.h>
#include "netdb-compat.h"
#include <stdio.h>
#include <fcntl.h>
#include <syslog.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/mman.h>
#include <signal.h>
#include <errno.h>
#include <getopt.h>
#include <stdarg.h>
#include <stdbool.h>
#include <time.h>

#include <linux/ioctl.h>
#define MY_NAME "nbd_client"
#include "cliserv.h"

#ifdef WITH_SDP
#include <sdp_inet.h>
#endif

#define NBDC_DO_LIST 1

int check_conn(char* devname, int do_print) {
        char buf[256];
        char* p;
        int fd;
        int len;

        if( (p=strrchr(devname, '/')) ) {
                devname=p+1;
        }
        if((p=strchr(devname, 'p'))) {
                /* We can't do checks on partitions. */
                *p='\0';
        }
        snprintf(buf, 256, "/sys/block/%s/pid", devname);
        if((fd=open(buf, O_RDONLY))<0) {
                if(errno==ENOENT) {
                        return 1;
                } else {
                        return 2;
                }
        }
        len=read(fd, buf, 256);
        if(len < 0) {
                perror("could not read from server");
                return 2;
        }
        buf[(len < 256) ? len : 255]='\0';
        if(do_print) printf("%s\n", buf);
        close(fd);
        return 0;
}

int opennet(char *name, char* portstr, int sdp) {
        int sock;
        struct addrinfo hints;
        struct addrinfo *ai = NULL;
        struct addrinfo *rp = NULL;
        int e;

        memset(&hints,'\0',sizeof(hints));
        hints.ai_family = AF_UNSPEC;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;
        hints.ai_protocol = IPPROTO_TCP;

        e = getaddrinfo(name, portstr, &hints, &ai);

        if(e != 0) {
                fprintf(stderr, "getaddrinfo failed: %s\n", gai_strerror(e));
                freeaddrinfo(ai);
                return -1;
        }

        if(sdp) {
#ifdef WITH_SDP
                if (ai->ai_family == AF_INET)
                        ai->ai_family = AF_INET_SDP;
                else (ai->ai_family == AF_INET6)
                        ai->ai_family = AF_INET6_SDP;
#else
                err("Can't do SDP: I was not compiled with SDP support!");
#endif
        }

        for(rp = ai; rp != NULL; rp = rp->ai_next) {
                sock = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);

                if(sock == -1)
                        continue;       /* error */

                if(connect(sock, rp->ai_addr, rp->ai_addrlen) != -1)
                        break;          /* success */
                        
                close(sock);
        }

        if (rp == NULL) {
                err_nonfatal("Socket failed: %m");
                sock = -1;
                goto err;
        }

        setmysockopt(sock);
err:
        freeaddrinfo(ai);
        return sock;
}

int openunix(const char *path) {
        int sock;
        struct sockaddr_un un_addr;
        memset(&un_addr, 0, sizeof(un_addr));

        un_addr.sun_family = AF_UNIX;
        if (strnlen(path, sizeof(un_addr.sun_path)) == sizeof(un_addr.sun_path)) {
                err_nonfatal("UNIX socket path too long");
                return -1;
        }

        strncpy(un_addr.sun_path, path, sizeof(un_addr.sun_path) - 1);

        if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
                err_nonfatal("SOCKET failed");
                return -1;
        };

        if (connect(sock, &un_addr, sizeof(un_addr)) == -1) {
                err_nonfatal("CONNECT failed");
                close(sock);
                return -1;
        }
        return sock;
}

void ask_list(int sock) {
        uint32_t opt;
        uint32_t opt_server;
        uint32_t len;
        uint32_t reptype;
        uint64_t magic;
        int rlen;
        const int BUF_SIZE = 1024;
        char buf[BUF_SIZE];

        magic = ntohll(opts_magic);
        if (write(sock, &magic, sizeof(magic)) < 0)
                err("Failed/2.2: %m");

        /* Ask for the list */
        opt = htonl(NBD_OPT_LIST);
        if(write(sock, &opt, sizeof(opt)) < 0) {
                err("writing list option failed: %m");
        }
        /* Send the length (zero) */
        len = htonl(0);
        if(write(sock, &len, sizeof(len)) < 0) {
                err("writing length failed: %m");
        }
        /* newline, move away from the "Negotiation:" line */
        printf("\n");
        do {
                memset(buf, 0, 1024);
                if(read(sock, &magic, sizeof(magic)) < 0) {
                        err("Reading magic from server: %m");
                }
                if(read(sock, &opt_server, sizeof(opt_server)) < 0) {
                        err("Reading option: %m");
                }
                if(read(sock, &reptype, sizeof(reptype)) <0) {
                        err("Reading reply from server: %m");
                }
                if(read(sock, &len, sizeof(len)) < 0) {
                        err("Reading length from server: %m");
                }
                magic=ntohll(magic);
                len=ntohl(len);
                reptype=ntohl(reptype);
                if(magic != rep_magic) {
                        err("Not enough magic from server");
                }
                if(reptype & NBD_REP_FLAG_ERROR) {
                        switch(reptype) {
                                case NBD_REP_ERR_POLICY:
                                        fprintf(stderr, "\nE: listing not allowed by server.\n");
                                        break;
                                default:
                                        fprintf(stderr, "\nE: unexpected error from server.\n");
                                        break;
                        }
                        if(len > 0 && len < BUF_SIZE) {
                                if((rlen=read(sock, buf, len)) < 0) {
                                        fprintf(stderr, "\nE: could not read error message from server\n");
                                } else {
                                        buf[rlen] = '\0';
                                        fprintf(stderr, "Server said: %s\n", buf);
                                }
                        }
                        exit(EXIT_FAILURE);
                } else {
                        if(len) {
                                if(reptype != NBD_REP_SERVER) {
                                        err("Server sent us a reply we don't understand!");
                                }
                                if(read(sock, &len, sizeof(len)) < 0) {
                                        fprintf(stderr, "\nE: could not read export name length from server\n");
                                        exit(EXIT_FAILURE);
                                }
                                len=ntohl(len);
                                if (len >= BUF_SIZE) {
                                        fprintf(stderr, "\nE: export name on server too long\n");
                                        exit(EXIT_FAILURE);
                                }
                                if(read(sock, buf, len) < 0) {
                                        fprintf(stderr, "\nE: could not read export name from server\n");
                                        exit(EXIT_FAILURE);
                                }
                                buf[len] = 0;
                                printf("%s\n", buf);
                        }
                }
        } while(reptype != NBD_REP_ACK);
        opt=htonl(NBD_OPT_ABORT);
        len=htonl(0);
        magic=htonll(opts_magic);
        if (write(sock, &magic, sizeof(magic)) < 0)
                err("Failed/2.2: %m");
        if (write(sock, &opt, sizeof(opt)) < 0)
                err("Failed writing abort");
        if (write(sock, &len, sizeof(len)) < 0)
                err("Failed writing length");
}

void negotiate(int sock, u64 *rsize64, uint16_t *flags, char* name, uint32_t needed_flags, uint32_t client_flags, uint32_t do_opts) {
        u64 magic, size64;
        uint16_t tmp;
        uint16_t global_flags;
        char buf[256] = "\0\0\0\0\0\0\0\0\0";
        uint32_t opt;
        uint32_t namesize;

        printf("Negotiation: ");
        readit(sock, buf, 8);
        if (strcmp(buf, INIT_PASSWD))
                err("INIT_PASSWD bad");
        printf(".");
        readit(sock, &magic, sizeof(magic));
        magic = ntohll(magic);
        if (magic != opts_magic) {
                if(magic == cliserv_magic) {
                        err("It looks like you're trying to connect to an oldstyle server. This is no longer supported since nbd 3.10.");
                }
        }
        printf(".");
        readit(sock, &tmp, sizeof(uint16_t));
        global_flags = ntohs(tmp);
        if((needed_flags & global_flags) != needed_flags) {
                /* There's currently really only one reason why this
                 * check could possibly fail, but we may need to change
                 * this error message in the future... */
                fprintf(stderr, "\nE: Server does not support listing exports\n");
                exit(EXIT_FAILURE);
        }

        if (global_flags & NBD_FLAG_NO_ZEROES) {
                client_flags |= NBD_FLAG_C_NO_ZEROES;
        }
        client_flags = htonl(client_flags);
        if (write(sock, &client_flags, sizeof(client_flags)) < 0)
                err("Failed/2.1: %m");

        if(do_opts & NBDC_DO_LIST) {
                ask_list(sock);
                exit(EXIT_SUCCESS);
        }

        /* Write the export name that we're after */
        magic = htonll(opts_magic);
        if (write(sock, &magic, sizeof(magic)) < 0)
                err("Failed/2.2: %m");

        opt = ntohl(NBD_OPT_EXPORT_NAME);
        if (write(sock, &opt, sizeof(opt)) < 0)
                err("Failed/2.3: %m");
        namesize = (u32)strlen(name);
        namesize = ntohl(namesize);
        if (write(sock, &namesize, sizeof(namesize)) < 0)
                err("Failed/2.4: %m");
        if (write(sock, name, strlen(name)) < 0)
                err("Failed/2.4: %m");

        readit(sock, &size64, sizeof(size64));
        size64 = ntohll(size64);

        if ((size64>>12) > (uint64_t)~0UL) {
                printf("size = %luMB", (unsigned long)(size64>>20));
                err("Exported device is too big for me. Get 64-bit machine :-(\n");
        } else
                printf("size = %luMB", (unsigned long)(size64>>20));

        readit(sock, &tmp, sizeof(tmp));
        *flags = (uint32_t)ntohs(tmp);

        if (!(global_flags & NBD_FLAG_NO_ZEROES)) {
                readit(sock, &buf, 124);
        }
        printf("\n");

        *rsize64 = size64;
}

bool get_from_config(char* cfgname, char** name_ptr, char** dev_ptr, char** hostn_ptr, int* bs, int* timeout, int* persist, int* swap, int* sdp, int* b_unix, char**port) {
        int fd = open(SYSCONFDIR "/nbdtab", O_RDONLY);
        bool retval = false;
        if(fd < 0) {
                fprintf(stderr, "while opening %s: ", SYSCONFDIR "/nbdtab");
                perror("could not open config file");
                goto out;
        }
        off_t size = lseek(fd, 0, SEEK_END);
        lseek(fd, 0, SEEK_SET);
        void *data = NULL;
        char *fsep = "\n\t# ";
        char *lsep = "\n#";

        if(size < 0) {
                perror("E: mmap'ing nbdtab");
                exit(EXIT_FAILURE);
        }

        data = mmap(NULL, (size_t)size, PROT_READ, MAP_SHARED, fd, 0);
        char *loc = strstr((const char*)data, cfgname);
        if(!loc) {
                goto out;
        }
        size_t l = strlen(cfgname) + 6;
        *dev_ptr = malloc(l);
        snprintf(*dev_ptr, l, "/dev/%s", cfgname);

        size_t line_len, field_len, ws_len;
#define CHECK_LEN field_len = strcspn(loc, fsep); ws_len = strspn(loc+field_len, fsep); if(field_len > line_len || line_len <= 0) { goto out; }
#define MOVE_NEXT line_len -= field_len + ws_len; loc += field_len + ws_len
        // find length of line
        line_len = strcspn(loc, lsep);
        // first field is the device node name, which we already know, so skip it
        CHECK_LEN;
        MOVE_NEXT;
        // next field is the hostname
        CHECK_LEN;
        *hostn_ptr = strndup(loc, field_len);
        MOVE_NEXT;
        // third field is the export name
        CHECK_LEN;
        *name_ptr = strndup(loc, field_len);
        if(ws_len + field_len > line_len) {
                // optional last field is not there, so return success
                retval = true;
                goto out;
        }
        MOVE_NEXT;
        CHECK_LEN;
#undef CHECK_LEN
#undef MOVE_NEXT
        // fourth field is the options field, a comma-separated field of options
        do {
                if(!strncmp(loc, "bs=", 3)) {
                        *bs = (int)strtol(loc+3, &loc, 0);
                        goto next;
                }
                if(!strncmp(loc, "timeout=", 8)) {
                        *timeout = (int)strtol(loc+8, &loc, 0);
                        goto next;
                }
                if(!strncmp(loc, "port=", 5)) {
                        *port = strndup(loc+5, strcspn(loc+5, ","));
                        goto next;
                }
                if(!strncmp(loc, "persist", 7)) {
                        loc += 7;
                        *persist = 1;
                        goto next;
                }
                if(!strncmp(loc, "swap", 4)) {
                        *swap = 1;
                        loc += 4;
                        goto next;
                }
                if(!strncmp(loc, "sdp", 3)) {
                        *sdp = 1;
                        loc += 3;
                        goto next;
                }
                if(!strncmp(loc, "unix", 4)) {
                        *b_unix = 1;
                        loc += 4;
                        goto next;
                }
                // skip unknown options, with a warning unless they start with a '_'
                l = strcspn(loc, ",");
                if(*loc != '_') {
                        char* s = strndup(loc, l);
                        fprintf(stderr, "Warning: unknown option '%s' found in nbdtab file", s);
                        free(s);
                }
                loc += l;
next:
                if(*loc == ',') {
                        loc++;
                }
        } while(strcspn(loc, lsep) > 0);
        retval = true;
out:
        if(data != NULL) {
                munmap(data, size);
        }
        if(fd >= 0) {
                close(fd);
        }
        return retval;
}

void setsizes(int nbd, u64 size64, int blocksize, u32 flags) {
        unsigned long size;
        int read_only = (flags & NBD_FLAG_READ_ONLY) ? 1 : 0;

        if (size64>>12 > (uint64_t)~0UL)
                err("Device too large.\n");
        else {
                if (ioctl(nbd, NBD_SET_BLKSIZE, 4096UL) < 0)
                        err("Ioctl/1.1a failed: %m\n");
                size = (unsigned long)(size64>>12);
                if (ioctl(nbd, NBD_SET_SIZE_BLOCKS, size) < 0)
                        err("Ioctl/1.1b failed: %m\n");
                if (ioctl(nbd, NBD_SET_BLKSIZE, (unsigned long)blocksize) < 0)
                        err("Ioctl/1.1c failed: %m\n");
                fprintf(stderr, "bs=%d, sz=%llu bytes\n", blocksize, 4096ULL*size);
        }

        ioctl(nbd, NBD_CLEAR_SOCK);

        /* ignore error as kernel may not support */
        ioctl(nbd, NBD_SET_FLAGS, (unsigned long) flags);

        if (ioctl(nbd, BLKROSET, (unsigned long) &read_only) < 0)
                err("Unable to set read-only attribute for device");
}

void set_timeout(int nbd, int timeout) {
        if (timeout) {
                if (ioctl(nbd, NBD_SET_TIMEOUT, (unsigned long)timeout) < 0)
                        err("Ioctl NBD_SET_TIMEOUT failed: %m\n");
                fprintf(stderr, "timeout=%d\n", timeout);
        }
}

void finish_sock(int sock, int nbd, int swap) {
        if (ioctl(nbd, NBD_SET_SOCK, sock) < 0)
                err("Ioctl NBD_SET_SOCK failed: %m\n");

#ifndef __ANDROID__
        if (swap)
                mlockall(MCL_CURRENT | MCL_FUTURE);
#endif
}

static int
oom_adjust(const char *file, const char *value)
{
        int fd, rc;
        size_t len;

        fd = open(file, O_WRONLY);
        if (fd < 0)
                return -1;
        len = strlen(value);
        rc = write(fd, value, len) != (ssize_t) len;
        close(fd);
        return rc ? -1 : 0;
}

void usage(char* errmsg, ...) {
        if(errmsg) {
                char tmp[256];
                va_list ap;
                va_start(ap, errmsg);
                snprintf(tmp, 256, "ERROR: %s\n\n", errmsg);
                vfprintf(stderr, tmp, ap);
                va_end(ap);
        } else {
                fprintf(stderr, "nbd-client version %s\n", PACKAGE_VERSION);
        }
        fprintf(stderr, "Usage: nbd-client -name|-N name host [port] nbd_device\n\t[-block-size|-b block size] [-timeout|-t timeout] [-swap|-s] [-sdp|-S]\n\t[-persist|-p] [-nofork|-n] [-systemd-mark|-m]\n");
        fprintf(stderr, "Or   : nbd-client -u (with same arguments as above)\n");
        fprintf(stderr, "Or   : nbd-client nbdX\n");
        fprintf(stderr, "Or   : nbd-client -d nbd_device\n");
        fprintf(stderr, "Or   : nbd-client -c nbd_device\n");
        fprintf(stderr, "Or   : nbd-client -h|--help\n");
        fprintf(stderr, "Or   : nbd-client -l|--list host\n");
        fprintf(stderr, "Default value for blocksize is 1024 (recommended for ethernet)\n");
        fprintf(stderr, "Allowed values for blocksize are 512,1024,2048,4096\n"); /* will be checked in kernel :) */
        fprintf(stderr, "Note, that kernel 2.4.2 and older ones do not work correctly with\n");
        fprintf(stderr, "blocksizes other than 1024 without patches\n");
        fprintf(stderr, "Default value for port is 10809. Note that port must always be numeric\n");
}

void disconnect(char* device) {
        int nbd = open(device, O_RDWR);

        if (nbd < 0)
                err("Cannot open NBD: %m\nPlease ensure the 'nbd' module is loaded.");
        printf("disconnect, ");
        if (ioctl(nbd, NBD_DISCONNECT)<0)
                err("Ioctl failed: %m\n");
        printf("sock, ");
        if (ioctl(nbd, NBD_CLEAR_SOCK)<0)
                err("Ioctl failed: %m\n");
        printf("done\n");
}

int main(int argc, char *argv[]) {
        char* port=NBD_DEFAULT_PORT;
        int sock, nbd;
        int blocksize=1024;
        char *hostname=NULL;
        char *nbddev=NULL;
        int swap=0;
        int cont=0;
        int timeout=0;
        int sdp=0;
        int G_GNUC_UNUSED nofork=0; // if -dNOFORK
        u64 size64;
        uint16_t flags = 0;
        int c;
        int nonspecial=0;
        int b_unix=0;
        char* name="";
        uint16_t needed_flags=0;
        uint32_t cflags=NBD_FLAG_C_FIXED_NEWSTYLE;
        uint32_t opts=0;
        sigset_t block, old;
        struct sigaction sa;
        struct option long_options[] = {
                { "block-size", required_argument, NULL, 'b' },
                { "check", required_argument, NULL, 'c' },
                { "disconnect", required_argument, NULL, 'd' },
                { "help", no_argument, NULL, 'h' },
                { "list", no_argument, NULL, 'l' },
                { "name", required_argument, NULL, 'N' },
                { "nofork", no_argument, NULL, 'n' },
                { "persist", no_argument, NULL, 'p' },
                { "sdp", no_argument, NULL, 'S' },
                { "swap", no_argument, NULL, 's' },
                { "systemd-mark", no_argument, NULL, 'm' },
                { "timeout", required_argument, NULL, 't' },
                { "unix", no_argument, NULL, 'u' },
                { 0, 0, 0, 0 }, 
        };

        logging(MY_NAME);

        while((c=getopt_long_only(argc, argv, "-b:c:d:hlnN:pSst:u", long_options, NULL))>=0) {
                switch(c) {
                case 1:
                        // non-option argument
                        if(strchr(optarg, '=')) {
                                // old-style 'bs=' or 'timeout='
                                // argument
                                fprintf(stderr, "WARNING: old-style command-line argument encountered. This is deprecated.\n");
                                if(!strncmp(optarg, "bs=", 3)) {
                                        optarg+=3;
                                        goto blocksize;
                                }
                                if(!strncmp(optarg, "timeout=", 8)) {
                                        optarg+=8;
                                        goto timeout;
                                }
                                usage("unknown option %s encountered", optarg);
                                exit(EXIT_FAILURE);
                        }
                        switch(nonspecial++) {
                                case 0:
                                        // host
                                        hostname=optarg;
                                        break;
                                case 1:
                                        // port
                                        if(!strtol(optarg, NULL, 0)) {
                                                // not parseable as a number, assume it's the device
                                                nbddev = optarg;
                                                nonspecial++;
                                        } else {
                                                port = optarg;
                                        }
                                        break;
                                case 2:
                                        // device
                                        nbddev = optarg;
                                        break;
                                default:
                                        usage("too many non-option arguments specified");
                                        exit(EXIT_FAILURE);
                        }
                        break;
                case 'b':
                      blocksize:
                        blocksize=(int)strtol(optarg, NULL, 0);
                        break;
                case 'c':
                        return check_conn(optarg, 1);
                case 'd':
                        disconnect(optarg);
                        exit(EXIT_SUCCESS);
                case 'h':
                        usage(NULL);
                        exit(EXIT_SUCCESS);
                case 'l':
                        needed_flags |= NBD_FLAG_FIXED_NEWSTYLE;
                        opts |= NBDC_DO_LIST;
                        nbddev="";
                        break;
                case 'm':
                        argv[0][0] = '@';
                        break;
                case 'n':
                        nofork=1;
                        break;
                case 'N':
                        name=optarg;
                        break;
                case 'p':
                        cont=1;
                        break;
                case 's':
                        swap=1;
                        break;
                case 'S':
                        sdp=1;
                        break;
                case 't':
                      timeout:
                        timeout=strtol(optarg, NULL, 0);
                        break;
                case 'u':
                        b_unix = 1;
                        break;
                default:
                        fprintf(stderr, "E: option eaten by 42 mice\n");
                        exit(EXIT_FAILURE);
                }
        }

#ifdef __ANDROID__
  if (swap)
    err("swap option unsupported on Android because mlockall is unsupported.");
#endif
        if(hostname) {
                if((!name || !nbddev) && !(opts & NBDC_DO_LIST)) {
                        if(!strncmp(hostname, "nbd", 3) || !strncmp(hostname, "/dev/nbd", 8)) {
                                if(!get_from_config(hostname, &name, &nbddev, &hostname, &blocksize, &timeout, &cont, &swap, &sdp, &b_unix, &port)) {
                                        usage("no valid configuration for specified device found", hostname);
                                        exit(EXIT_FAILURE);
                                }
                        } else {
                                usage("not enough information specified, and argument didn't look like an nbd device");
                                exit(EXIT_FAILURE);
                        }
                }
        } else {
                usage("no information specified");
                exit(EXIT_FAILURE);
        }

        if(strlen(name)==0 && !(opts & NBDC_DO_LIST)) {
                printf("Warning: the oldstyle protocol is no longer supported.\nThis method now uses the newstyle protocol with a default export\n");
        }

        if (b_unix)
                sock = openunix(hostname);
        else
                sock = opennet(hostname, port, sdp);
        if (sock < 0)
                exit(EXIT_FAILURE);

        negotiate(sock, &size64, &flags, name, needed_flags, cflags, opts);

        nbd = open(nbddev, O_RDWR);
        if (nbd < 0)
          err("Cannot open NBD: %m\nPlease ensure the 'nbd' module is loaded.");

        setsizes(nbd, size64, blocksize, flags);
        set_timeout(nbd, timeout);
        finish_sock(sock, nbd, swap);
        if (swap) {
                /* try linux >= 2.6.36 interface first */
                if (oom_adjust("/proc/self/oom_score_adj", "-1000")) {
                        /* fall back to linux <= 2.6.35 interface */
                        oom_adjust("/proc/self/oom_adj", "-17");
                }
        }

        /* Go daemon */
        
#ifndef NOFORK
        if(!nofork) {
                if (daemon(0,0) < 0)
                        err("Cannot detach from terminal");
        }

        memset(&sa, 0, sizeof(sa));
        sa.sa_handler = SIG_IGN;
        sigaction(SIGCHLD, &sa, NULL);
#endif
        do {
#ifndef NOFORK

                sigfillset(&block);
                sigdelset(&block, SIGKILL);
                sigdelset(&block, SIGTERM);
                sigdelset(&block, SIGPIPE);
                sigprocmask(SIG_SETMASK, &block, &old);

                if (!fork()) {
                        /* Due to a race, the kernel NBD driver cannot
                         * call for a reread of the partition table
                         * in the handling of the NBD_DO_IT ioctl().
                         * Therefore, this is done in the first open()
                         * of the device. We therefore make sure that
                         * the device is opened at least once after the
                         * connection was made. This has to be done in a
                         * separate process, since the NBD_DO_IT ioctl()
                         * does not return until the NBD device has
                         * disconnected.
                         */
                        struct timespec req = {
                                .tv_sec = 0,
                                .tv_nsec = 100000000,
                        };
                        while(check_conn(nbddev, 0)) {
                                nanosleep(&req, NULL);
                        }
                        open(nbddev, O_RDONLY);
                        exit(0);
                }
#endif

                if (ioctl(nbd, NBD_DO_IT) < 0) {
                        int error = errno;
                        fprintf(stderr, "nbd,%d: Kernel call returned: %d", getpid(), error);
                        if(error==EBADR) {
                                /* The user probably did 'nbd-client -d' on us.
                                 * quit */
                                cont=0;
                        } else {
                                if(cont) {
                                        u64 new_size;
                                        uint16_t new_flags;

                                        close(sock); close(nbd);
                                        for (;;) {
                                                fprintf(stderr, " Reconnecting\n");
                                                if (b_unix)
                                                        sock = openunix(hostname);
                                                else
                                                        sock = opennet(hostname, port, sdp);
                                                if (sock >= 0)
                                                        break;
                                                sleep (1);
                                        }
                                        nbd = open(nbddev, O_RDWR);
                                        if (nbd < 0)
                                                err("Cannot open NBD: %m");
                                        negotiate(sock, &new_size, &new_flags, name, needed_flags, cflags, opts);
                                        if (size64 != new_size) {
                                                err("Size of the device changed. Bye");
                                        }
                                        setsizes(nbd, size64, blocksize,
                                                                new_flags);

                                        set_timeout(nbd, timeout);
                                        finish_sock(sock,nbd,swap);
                                }
                        }
                } else {
                        /* We're on 2.4. It's not clearly defined what exactly
                         * happened at this point. Probably best to quit, now
                         */
                        fprintf(stderr, "Kernel call returned.");
                        cont=0;
                }
        } while(cont);
        printf("sock, ");
        ioctl(nbd, NBD_CLEAR_SOCK);
        printf("done\n");
        return 0;
}