nbd: Introduce NBD named exports.

This patch allows to connect Qemu using NBD protocol to an nbd-server
using named exports.

For instance, if on the host "isoserver", in /etc/nbd-server/config, you have:

[generic]
[debian-500-ppc-netinst]
        exportname = /ISO/debian-500-powerpc-netinst.iso
[Fedora-10-ppc-netinst]
        exportname = /ISO/Fedora-10-ppc-netinst.iso

You can connect to it, using:

    qemu -cdrom nbd:isoserver:exportname=debian-500-ppc-netinst
    qemu -cdrom nbd:isoserver:exportname=Fedora-10-ppc-netinst

NOTE: you need at least nbd-server 2.9.18

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/nbd.c

@@ -33,6 +33,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#define EN_OPTSTR ":exportname="
+
 typedef struct BDRVNBDState {
     int sock;
     off_t size;
@@ -42,55 +44,83 @@ typedef struct BDRVNBDState {
 static int nbd_open(BlockDriverState *bs, const char* filename, int flags)
 {
     BDRVNBDState *s = bs->opaque;
+    uint32_t nbdflags;
+
+    char *file;
+    char *name;
     const char *host;
     const char *unixpath;
     int sock;
     off_t size;
     size_t blocksize;
     int ret;
+    int err = -EINVAL;
 
-    if (!strstart(filename, "nbd:", &host))
+    file = qemu_strdup(filename);
-        return -EINVAL;
+
+    name = strstr(file, EN_OPTSTR);
+    if (name) {
+        if (name[strlen(EN_OPTSTR)] == 0) {
+            goto out;
+        }
+        name[0] = 0;
+        name += strlen(EN_OPTSTR);
+    }
+
+    if (!strstart(file, "nbd:", &host)) {
+        goto out;
+    }
 
     if (strstart(host, "unix:", &unixpath)) {
 
-        if (unixpath[0] != '/')
+        if (unixpath[0] != '/') {
-            return -EINVAL;
+            goto out;
+        }
 
         sock = unix_socket_outgoing(unixpath);
 
     } else {
-        uint16_t port;
+        uint16_t port = NBD_DEFAULT_PORT;
         char *p, *r;
         char hostname[128];
 
         pstrcpy(hostname, 128, host);
 
         p = strchr(hostname, ':');
-        if (p == NULL)
+        if (p != NULL) {
-            return -EINVAL;
+            *p = '\0';
+            p++;
 
-        *p = '\0';
+            port = strtol(p, &r, 0);
-        p++;
+            if (r == p) {
+                goto out;
+            }
+        } else if (name == NULL) {
+            goto out;
+        }
 
-        port = strtol(p, &r, 0);
-        if (r == p)
-            return -EINVAL;
         sock = tcp_socket_outgoing(hostname, port);
     }
 
-    if (sock == -1)
+    if (sock == -1) {
-        return -errno;
+        err = -errno;
+        goto out;
+    }
 
-    ret = nbd_receive_negotiate(sock, &size, &blocksize);
+    ret = nbd_receive_negotiate(sock, name, &nbdflags, &size, &blocksize);
-    if (ret == -1)
+    if (ret == -1) {
-        return -errno;
+        err = -errno;
+        goto out;
+    }
 
     s->sock = sock;
     s->size = size;
     s->blocksize = blocksize;
+    err = 0;
 
-    return 0;
+out:
+    qemu_free(file);
+    return err;
 }
 
 static int nbd_read(BlockDriverState *bs, int64_t sector_num,

nbd.c

@@ -62,6 +62,8 @@
 #define NBD_SET_SIZE_BLOCKS	_IO(0xab, 7)
 #define NBD_DISCONNECT          _IO(0xab, 8)
 
+#define NBD_OPT_EXPORT_NAME	(1 << 0)
+
 /* That's all folks */
 
 #define read_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, true)
@@ -296,22 +298,27 @@ int nbd_negotiate(int csock, off_t size)
 	return 0;
 }
 
-int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize)
+int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
+                          off_t *size, size_t *blocksize)
 {
-	char buf[8 + 8 + 8 + 128];
+	char buf[256];
-	uint64_t magic;
+	uint64_t magic, s;
+	uint16_t tmp;
 
 	TRACE("Receiving negotation.");
 
-	if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
+	if (read_sync(csock, buf, 8) != 8) {
 		LOG("read failed");
 		errno = EINVAL;
 		return -1;
 	}
 
-	magic = be64_to_cpup((uint64_t*)(buf + 8));
+	buf[8] = '\0';
-	*size = be64_to_cpup((uint64_t*)(buf + 16));
+	if (strlen(buf) == 0) {
-	*blocksize = 1024;
+		LOG("server connection closed");
+		errno = EINVAL;
+		return -1;
+	}
 
 	TRACE("Magic is %c%c%c%c%c%c%c%c",
 	      qemu_isprint(buf[0]) ? buf[0] : '.',
@@ -322,8 +329,6 @@ int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize)
 	      qemu_isprint(buf[5]) ? buf[5] : '.',
 	      qemu_isprint(buf[6]) ? buf[6] : '.',
 	      qemu_isprint(buf[7]) ? buf[7] : '.');
-	TRACE("Magic is 0x%" PRIx64, magic);
-	TRACE("Size is %" PRIu64, *size);
 
 	if (memcmp(buf, "NBDMAGIC", 8) != 0) {
 		LOG("Invalid magic received");
@@ -331,10 +336,99 @@ int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize)
 		return -1;
 	}
 
-	TRACE("Checking magic");
+	if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+		LOG("read failed");
+		errno = EINVAL;
+		return -1;
+	}
+	magic = be64_to_cpu(magic);
+	TRACE("Magic is 0x%" PRIx64, magic);
 
-	if (magic != 0x00420281861253LL) {
+	if (name) {
-		LOG("Bad magic received");
+		uint32_t reserved = 0;
+		uint32_t opt;
+		uint32_t namesize;
+
+		TRACE("Checking magic (opts_magic)");
+		if (magic != 0x49484156454F5054LL) {
+			LOG("Bad magic received");
+			errno = EINVAL;
+			return -1;
+		}
+		if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+			LOG("flags read failed");
+			errno = EINVAL;
+			return -1;
+		}
+		*flags = be16_to_cpu(tmp) << 16;
+		/* reserved for future use */
+		if (write_sync(csock, &reserved, sizeof(reserved)) !=
+		    sizeof(reserved)) {
+			LOG("write failed (reserved)");
+			errno = EINVAL;
+			return -1;
+		}
+		/* write the export name */
+		magic = cpu_to_be64(magic);
+		if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
+			LOG("write failed (magic)");
+			errno = EINVAL;
+			return -1;
+		}
+		opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
+		if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
+			LOG("write failed (opt)");
+			errno = EINVAL;
+			return -1;
+		}
+		namesize = cpu_to_be32(strlen(name));
+		if (write_sync(csock, &namesize, sizeof(namesize)) !=
+		    sizeof(namesize)) {
+			LOG("write failed (namesize)");
+			errno = EINVAL;
+			return -1;
+		}
+		if (write_sync(csock, (char*)name, strlen(name)) != strlen(name)) {
+			LOG("write failed (name)");
+			errno = EINVAL;
+			return -1;
+		}
+	} else {
+		TRACE("Checking magic (cli_magic)");
+
+		if (magic != 0x00420281861253LL) {
+			LOG("Bad magic received");
+			errno = EINVAL;
+			return -1;
+		}
+	}
+
+	if (read_sync(csock, &s, sizeof(s)) != sizeof(s)) {
+		LOG("read failed");
+		errno = EINVAL;
+		return -1;
+	}
+	*size = be64_to_cpu(s);
+	*blocksize = 1024;
+	TRACE("Size is %" PRIu64, *size);
+
+	if (!name) {
+		if (read_sync(csock, flags, sizeof(*flags)) != sizeof(*flags)) {
+			LOG("read failed (flags)");
+			errno = EINVAL;
+			return -1;
+		}
+		*flags = be32_to_cpup(flags);
+	} else {
+		if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+			LOG("read failed (tmp)");
+			errno = EINVAL;
+			return -1;
+		}
+		*flags |= be32_to_cpu(tmp);
+	}
+	if (read_sync(csock, &buf, 124) != 124) {
+		LOG("read failed (buf)");
 		errno = EINVAL;
 		return -1;
 	}

nbd.h

@@ -42,6 +42,8 @@ enum {
     NBD_CMD_DISC = 2
 };
 
+#define NBD_DEFAULT_PORT	10809
+
 size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read);
 int tcp_socket_outgoing(const char *address, uint16_t port);
 int tcp_socket_incoming(const char *address, uint16_t port);
@@ -49,7 +51,8 @@ int unix_socket_outgoing(const char *path);
 int unix_socket_incoming(const char *path);
 
 int nbd_negotiate(int csock, off_t size);
-int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize);
+int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
+                          off_t *size, size_t *blocksize);
 int nbd_init(int fd, int csock, off_t size, size_t blocksize);
 int nbd_send_request(int csock, struct nbd_request *request);
 int nbd_receive_reply(int csock, struct nbd_reply *reply);

qemu-doc.texi

@@ -620,6 +620,13 @@ qemu linux1.img -hdb nbd:unix:/tmp/my_socket
 qemu linux2.img -hdb nbd:unix:/tmp/my_socket
 @end example
 
+If the nbd-server uses named exports (since NBD 2.9.18), you must use the
+"exportname" option:
+@example
+qemu -cdrom nbd:localhost:exportname=debian-500-ppc-netinst
+qemu -cdrom nbd:localhost:exportname=openSUSE-11.1-ppc-netinst
+@end example
+
 @node pcsys_network
 @section Network emulation
 

qemu-nbd.c

@@ -230,6 +230,7 @@ int main(int argc, char **argv)
     int nb_fds = 0;
     int max_fd;
     int persistent = 0;
+    uint32_t nbdflags;
 
     while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
         switch (ch) {
@@ -398,7 +399,8 @@ int main(int argc, char **argv)
                 goto out;
             }
 
-            ret = nbd_receive_negotiate(sock, &size, &blocksize);
+            ret = nbd_receive_negotiate(sock, NULL, &nbdflags,
+					&size, &blocksize);
             if (ret == -1) {
                 ret = 1;
                 goto out;