nbd: support feature negotiation

nbd supports writing flags in bytes 24...27 of the header,
and uses that for the read-only flag.  Add support for it
in qemu-nbd.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/nbd.h b/nbd.h
index df7b7af7c0..b9c3b391d6 100644
--- a/nbd.h
+++ b/nbd.h
@@ -37,6 +37,9 @@ struct nbd_reply {
     uint64_t handle;
 } QEMU_PACKED;
 
+#define NBD_FLAG_HAS_FLAGS      (1 << 0)        /* Flags are there */
+#define NBD_FLAG_READ_ONLY      (1 << 1)        /* Device is read-only */
+
 enum {
     NBD_CMD_READ = 0,
     NBD_CMD_WRITE = 1,
@@ -53,14 +56,14 @@ int tcp_socket_incoming_spec(const char *address_and_port);
 int unix_socket_outgoing(const char *path);
 int unix_socket_incoming(const char *path);
 
-int nbd_negotiate(int csock, off_t size);
+int nbd_negotiate(int csock, off_t size, uint32_t flags);
 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_init(int fd, int csock, uint32_t flags, 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);
 int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
-             off_t *offset, bool readonly, uint8_t *data, int data_size);
+             off_t *offset, uint32_t nbdflags, uint8_t *data, int data_size);
 int nbd_client(int fd);
 int nbd_disconnect(int fd);