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 dozen possible error codes and squash everything else to EINVAL. Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- nbd.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/nbd.c b/nbd.c index eea8c51..1ad5b66 100644 --- a/nbd.c +++ b/nbd.c @@ -86,6 +86,37 @@ #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. + */ +static int system_errno_to_nbd_errno(int err) +{ + switch (err) { + case EPERM: + return 1; + case EIO: + return 5; + case ENXIO: + return 6; + case E2BIG: + return 7; + case ENOMEM: + return 12; + case EACCES: + return 13; + case EFBIG: + return 27; + case ENOSPC: + return 28; + case EROFS: + return 30; + case EINVAL: + default: + return 22; + } +} + /* Definitions for opaque data types */ typedef struct NBDRequest NBDRequest; @@ -856,6 +887,20 @@ 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)); + /* NBD errors should be universally equal to the corresponding + * errno values, check it here. + */ + QEMU_BUILD_BUG_ON(EPERM != 1); + QEMU_BUILD_BUG_ON(EIO != 5); + QEMU_BUILD_BUG_ON(ENXIO != 6); + QEMU_BUILD_BUG_ON(E2BIG != 7); + QEMU_BUILD_BUG_ON(ENOMEM != 12); + QEMU_BUILD_BUG_ON(EACCES != 13); + QEMU_BUILD_BUG_ON(EINVAL != 22); + QEMU_BUILD_BUG_ON(EFBIG != 27); + QEMU_BUILD_BUG_ON(ENOSPC != 28); + QEMU_BUILD_BUG_ON(EROFS != 30); + TRACE("Got reply: " "{ magic = 0x%x, .error = %d, handle = %" PRIu64" }", magic, reply->error, reply->handle); @@ -872,6 +917,8 @@ 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) -- 2.3.5