[Qemu-devel] [PATCH][v2] Merge NBD client/server int qemu-nbd

[Laurent Vivier <Laurent.Vivier@bull.net>]

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Hi,

this patch allows to connect directly a disk image file to an NBD
device. It introduces the use of a unix socket (instead of inet).

- To connect a file to a device:

# qemu-nbd --connect=/dev/nbd0 my_disk.qcow2

Then you can see directly your disk (no need of nbd-client):

# fdisk -l /dev/nbd0

Disk /dev/nbd0: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

     Device Boot      Start         End      Blocks   Id  System
/dev/nbd0p1   *           1         492     3951958+  83  Linux
/dev/nbd0p2             493         522      240975    5  Extended
/dev/nbd0p5             493         522      240943+  82  Linux swap /
Solaris

- To disconnect the file from the device:

# qemu-nbd --disconnect /dev/nbd0

Changelog:
- v2: call show_parts() from client and avoid the sleep(1). Thank you to
Avi and Anthony. Include my cleanup patch and comments from Carlo
Marcelo Arenas Belon.

Regards,
Laurent
-- 
------------- Laurent.Vivier@bull.net ---------------
"The best way to predict the future is to invent it."
- Alan Kay

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Index: qemu/nbd.c
===================================================================
--- qemu.orig/nbd.c	2008-06-18 17:05:46.000000000 +0200
+++ qemu/nbd.c	2008-06-19 10:47:46.000000000 +0200
@@ -25,6 +25,7 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <sys/socket.h>
+#include <sys/un.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
 #include <arpa/inet.h>
@@ -183,6 +184,65 @@ error:
     return -1;
 }
 
+int unix_socket_incoming(const char *path)
+{
+    int s;
+    struct sockaddr_un addr;
+    int serrno;
+
+    s = socket(PF_UNIX, SOCK_STREAM, 0);
+    if (s == -1) {
+        return -1;
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sun_family = AF_UNIX;
+    pstrcpy(addr.sun_path, sizeof(addr.sun_path), path);
+
+    if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+        goto error;
+    }
+
+    if (listen(s, 128) == -1) {
+        goto error;
+    }
+
+    return s;
+error:
+    serrno = errno;
+    close(s);
+    errno = serrno;
+    return -1;
+}
+
+int unix_socket_outgoing(const char *path)
+{
+    int s;
+    struct sockaddr_un addr;
+    int serrno;
+
+    s = socket(PF_UNIX, SOCK_STREAM, 0);
+    if (s == -1) {
+        return -1;
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sun_family = AF_UNIX;
+    pstrcpy(addr.sun_path, sizeof(addr.sun_path), path);
+
+    if (connect(s, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+        goto error;
+    }
+
+    return s;
+error:
+    serrno = errno;
+    close(s);
+    errno = serrno;
+    return -1;
+}
+
+
 /* Basic flow
 
    Server         Client
@@ -388,8 +448,8 @@ int nbd_trip(BlockDriverState *bs, int c
 	}
 
 	if (len > sizeof(data)) {
-		LOG("len (%u) is larger than max len (%u)",
-		    len, sizeof(data));
+		LOG("len (%u) is larger than max len (%lu)",
+		    len, (unsigned long)sizeof(data));
 		errno = EINVAL;
 		return -1;
 	}
Index: qemu/nbd.h
===================================================================
--- qemu.orig/nbd.h	2008-06-18 17:05:46.000000000 +0200
+++ qemu/nbd.h	2008-06-19 10:47:46.000000000 +0200
@@ -27,6 +27,8 @@
 #include "block_int.h"
 
 int tcp_socket_incoming(const char *address, uint16_t port);
+int unix_socket_outgoing(const char *path);
+int unix_socket_incoming(const char *path);
 
 int nbd_negotiate(BlockDriverState *bs, int csock, off_t size);
 int nbd_receive_negotiate(int fd, int csock);
Index: qemu/qemu-nbd.c
===================================================================
--- qemu.orig/qemu-nbd.c	2008-06-18 17:05:46.000000000 +0200
+++ qemu/qemu-nbd.c	2008-06-19 10:48:49.000000000 +0200
@@ -21,15 +21,18 @@
 #include "block_int.h"
 #include "nbd.h"
 
-#include <malloc.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <getopt.h>
 #include <err.h>
+#include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
 #include <arpa/inet.h>
+#include <signal.h>
+
+//#define DEBUG
 
 int verbose;
 
@@ -44,6 +47,8 @@ static void usage(const char *name)
 "  -b, --bind=IFACE     interface to bind to (default `0.0.0.0')\n"
 "  -r, --read-only      export read-only\n"
 "  -P, --partition=NUM  only expose partition NUM\n"
+"  -c, --connect=DEV    connect FILE to the local NBD device DEV\n"
+"  -d, --disconnect     disconnect the specified device\n"
 "  -v, --verbose        display extra debugging information\n"
 "  -h, --help           display this help and exit\n"
 "  -V, --version        output version information and exit\n"
@@ -145,19 +150,39 @@ static int find_partition(BlockDriverSta
     return -1;
 }
 
+static void show_parts(const char *device)
+{
+    if (fork() == 0) {
+        int nbd;
+
+        /* linux just needs an open() to trigger
+         * the partition table update
+         * but remember to load the module with max_part != 0 :
+         *     modprobe nbd max_part=63
+         */
+        nbd = open(device, O_RDWR);
+        if (nbd != -1)
+        	close(nbd);
+        exit(0);
+    }
+}
+
 int main(int argc, char **argv)
 {
     BlockDriverState *bs;
     off_t dev_offset = 0;
     off_t offset = 0;
     bool readonly = false;
+    bool disconnect = false;
     const char *bindto = "0.0.0.0";
     int port = 1024;
     int sock, csock;
     struct sockaddr_in addr;
     socklen_t addr_len = sizeof(addr);
     off_t fd_size;
-    const char *sopt = "hVbo:p:rsP:v";
+    char *device;
+    char sockpath[128];
+    const char *sopt = "hVbo:p:rsP:c:dv?";
     struct option lopt[] = {
         { "help", 0, 0, 'h' },
         { "version", 0, 0, 'V' },
@@ -166,8 +191,11 @@ int main(int argc, char **argv)
         { "offset", 1, 0, 'o' },
         { "read-only", 0, 0, 'r' },
         { "partition", 1, 0, 'P' },
+        { "connect", 1, 0, 'c' },
+        { "disconnect", 0, 0, 'd' },
         { "snapshot", 0, 0, 's' },
         { "verbose", 0, 0, 'v' },
+	{ 0, 0, 0, 0 }
     };
     int ch;
     int opt_ind = 0;
@@ -175,6 +203,8 @@ int main(int argc, char **argv)
     char *end;
     bool snapshot = false;
     int partition = -1;
+    int fd;
+    int ret;
 
     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
         switch (ch) {
@@ -213,6 +243,12 @@ int main(int argc, char **argv)
             if (partition < 1 || partition > 8)
                 errx(EINVAL, "Invalid partition %d", partition);
             break;
+        case 'd':
+            disconnect = true;
+            break;
+        case 'c':
+            device = optarg;
+            break;
         case 'v':
             verbose = 1;
             break;
@@ -236,6 +272,20 @@ int main(int argc, char **argv)
              argv[0]);
     }
 
+    if (disconnect) {
+        fd = open(argv[optind], O_RDWR);
+        if (fd == -1)
+            errx(errno, "Cannot open %s", argv[optind]);
+
+        nbd_disconnect(fd);
+
+        close(fd);
+
+        printf("%s disconnected\n", argv[optind]);
+
+	return 0;
+    }
+
     bdrv_init();
 
     bs = bdrv_new("hda");
@@ -251,7 +301,60 @@ int main(int argc, char **argv)
         find_partition(bs, partition, &dev_offset, &fd_size))
         errx(errno, "Could not find partition %d", partition);
 
-    sock = tcp_socket_incoming(bindto, port);
+    if (device) {
+	pid_t pid;
+	if (!verbose)
+            daemon(0, 0);	/* detach client and server */
+
+        sprintf(sockpath, "/var/lock/qemu-img-%s", basename(device));
+
+        pid = fork();
+        if (pid < 0)
+            return 1;
+	if (pid != 0) {
+            ret = 0;
+            bdrv_close(bs);
+
+            do {
+                sock = unix_socket_outgoing(sockpath);
+                if (sock == -1) {
+                    if (errno != ENOENT && errno != ECONNREFUSED)
+                        goto exit;
+                    sleep(1);	/* wait children */
+                }
+            } while (sock == -1);
+
+            fd = open(device, O_RDWR);
+            if (fd == -1) {
+                ret = -1;
+                goto exit;
+            }
+
+            ret = nbd_receive_negotiate(fd, sock);
+            if (ret == -1)
+                goto exit;
+
+            printf("NBD device %s is now connected to file %s\n",
+                    device, argv[optind]);
+
+	    /* if supported, update partition table */
+
+            show_parts(device);
+
+            nbd_client(fd, sock);
+            close(fd);
+exit:
+            kill(pid, SIGTERM);
+            unlink(sockpath);
+
+            return ret;
+        }
+        /* children */
+        sock = unix_socket_incoming(sockpath);
+    } else {
+        sock = tcp_socket_incoming(bindto, port);
+    }
+
     if (sock == -1)
         return 1;