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>

1 files changed, 106 insertions, 12 deletions

diff --git a/nbd.c b/nbd.c
index a9f295f2bb..30dec8d2c5 100644
--- a/nbd.c
+++ b/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];
-	uint64_t magic;
+	char buf[256];
+	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));
-	*size = be64_to_cpup((uint64_t*)(buf + 16));
-	*blocksize = 1024;
+	buf[8] = '\0';
+	if (strlen(buf) == 0) {
+		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 (name) {
+		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 (magic != 0x00420281861253LL) {
-		LOG("Bad magic received");
+	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;
 	}