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authorPaolo Bonzini <pbonzini@redhat.com>2015-05-07 17:25:10 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-05-08 14:45:11 +0200
commitca4414804114fd0095b317785bc0b51862e62ebb (patch)
tree1d6900bb9761902a6587149180377aa01e9f23a2
parentd24697e1824467f3921c84a94f011f43d6466403 (diff)
qemu-nbd: only send a limited number of errno codes on the wire
Right now, NBD includes potentially platform-specific error values in the wire protocol. Luckily, most common error values are more or less universal: in particular, of all errno values <= 34 (up to ERANGE), they are all the same on supported platforms except for 11 (which is EAGAIN on Windows and Linux, but EDEADLK on Darwin and the *BSDs). So, in order to guarantee some portability, only keep a handful of possible error codes and squash everything else to EINVAL. This patch defines a limited set of errno values that are valid for the NBD protocol, and specifies recommendations for what error to return in specific corner cases. The set of errno values is roughly based on the errors listed in the read(2) and write(2) man pages, with some exceptions: - ENOMEM is added for servers that implement copy-on-write or other formats that require dynamic allocation. - EDQUOT is not part of the universal set of errors; it can be changed to ENOSPC on the wire format. - EFBIG is part of the universal set of errors, but it is also changed to ENOSPC because it is pretty similar to ENOSPC or EDQUOT. Incoming values will in general match system errno values, but not on the Hurd which has different errno values (they have a "subsystem code" equal to 0x10 in bits 24-31). The Hurd is probably not something to which QEMU has been ported, but still do the right thing and reverse-map the NBD errno values to the system errno values. The corresponding patch to the NBD protocol description can be found at http://article.gmane.org/gmane.linux.drivers.nbd.general/3154. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--nbd.c57
1 files changed, 57 insertions, 0 deletions
diff --git a/nbd.c b/nbd.c
index cb1b9bbf7c..06b501ba67 100644
--- a/nbd.c
+++ b/nbd.c
@@ -86,6 +86,59 @@
#define NBD_OPT_ABORT (2)
#define NBD_OPT_LIST (3)
+/* NBD errors are based on errno numbers, so there is a 1:1 mapping,
+ * but only a limited set of errno values is specified in the protocol.
+ * Everything else is squashed to EINVAL.
+ */
+#define NBD_SUCCESS 0
+#define NBD_EPERM 1
+#define NBD_EIO 5
+#define NBD_ENOMEM 12
+#define NBD_EINVAL 22
+#define NBD_ENOSPC 28
+
+static int system_errno_to_nbd_errno(int err)
+{
+ switch (err) {
+ case 0:
+ return NBD_SUCCESS;
+ case EPERM:
+ return NBD_EPERM;
+ case EIO:
+ return NBD_EIO;
+ case ENOMEM:
+ return NBD_ENOMEM;
+#ifdef EDQUOT
+ case EDQUOT:
+#endif
+ case EFBIG:
+ case ENOSPC:
+ return NBD_ENOSPC;
+ case EINVAL:
+ default:
+ return NBD_EINVAL;
+ }
+}
+
+static int nbd_errno_to_system_errno(int err)
+{
+ switch (err) {
+ case NBD_SUCCESS:
+ return 0;
+ case NBD_EPERM:
+ return EPERM;
+ case NBD_EIO:
+ return EIO;
+ case NBD_ENOMEM:
+ return ENOMEM;
+ case NBD_ENOSPC:
+ return ENOSPC;
+ case NBD_EINVAL:
+ default:
+ return EINVAL;
+ }
+}
+
/* Definitions for opaque data types */
typedef struct NBDRequest NBDRequest;
@@ -856,6 +909,8 @@ ssize_t nbd_receive_reply(int csock, struct nbd_reply *reply)
reply->error = be32_to_cpup((uint32_t*)(buf + 4));
reply->handle = be64_to_cpup((uint64_t*)(buf + 8));
+ reply->error = nbd_errno_to_system_errno(reply->error);
+
TRACE("Got reply: "
"{ magic = 0x%x, .error = %d, handle = %" PRIu64" }",
magic, reply->error, reply->handle);
@@ -872,6 +927,8 @@ static ssize_t nbd_send_reply(int csock, struct nbd_reply *reply)
uint8_t buf[NBD_REPLY_SIZE];
ssize_t ret;
+ reply->error = system_errno_to_nbd_errno(reply->error);
+
/* Reply
[ 0 .. 3] magic (NBD_REPLY_MAGIC)
[ 4 .. 7] error (0 == no error)