5:45 a.m.
This sends the last error saved in the connection handle back to the
NBD client. This is informational and best effort.
qemu reports the error already, for example:
$ nbdkit --log=null \
eval open=' echo EPERM Go Away >&2; exit 1 ' get_size=' echo
100 ' \
--run 'qemu-img info "$uri"'
qemu-img: Could not open 'nbd+unix://?socket=/tmp/nbdkitIDl6iy/socket':
Requested export not available
server reported: /tmp/nbdkitRDAfXH/open: Go Away
This goes back to at least qemu 2.12.0 (RHEL 7) and possibly earlier,
so we can just assume that qemu does this for the test.
libnbd requires a patch to display this information.
---
tests/Makefile.am | 2 +
server/protocol-handshake-newstyle.c | 22 ++++++++++-
tests/test-last-error.sh | 55 ++++++++++++++++++++++++++++
3 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 8c7d6b8c96..89c5fa9d0f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -292,6 +292,7 @@ TESTS += \
test-read-password-interactive.sh \
test-nbd-client.sh \
test-nbd-client-tls.sh \
+ test-last-error.sh \
$(NULL)
if !IS_WINDOWS
TESTS += \
@@ -324,6 +325,7 @@ EXTRA_DIST += \
test-help-plugin.sh \
test-ipv4-lo.sh \
test-ipv6-lo.sh \
+ test-last-error.sh \
test-long-name.sh \
test-nbd-client-tls.sh \
test-nbd-client.sh \
diff --git a/server/protocol-handshake-newstyle.c b/server/protocol-handshake-newstyle.c
index 6b3bc76f0f..46cd0328b1 100644
--- a/server/protocol-handshake-newstyle.c
+++ b/server/protocol-handshake-newstyle.c
@@ -57,16 +57,32 @@ send_newstyle_option_reply (uint32_t option, uint32_t reply)
{
GET_CONN;
struct nbd_fixed_new_option_reply fixed_new_option_reply;
+ const char *last_error = NULL;
+ uint32_t replylen = 0;
+
+ if (NBD_REP_IS_ERR (reply)) {
+ last_error = threadlocal_get_last_error ();
+ /* Note that calling nbdkit_error will invalidate last_error, so
+ * be careful below.
+ */
+ if (last_error) {
+ size_t len = strlen (last_error);
+ if (len <= NBD_MAX_STRING)
+ replylen = len;
+ }
+ }
fixed_new_option_reply.magic = htobe64 (NBD_REP_MAGIC);
fixed_new_option_reply.option = htobe32 (option);
fixed_new_option_reply.reply = htobe32 (reply);
- fixed_new_option_reply.replylen = htobe32 (0);
+ fixed_new_option_reply.replylen = htobe32 (replylen);
debug ("replying to %s with %s", name_of_nbd_opt (option),
name_of_nbd_rep (reply));
if (conn->send (&fixed_new_option_reply,
- sizeof fixed_new_option_reply, 0) == -1) {
+ sizeof fixed_new_option_reply,
+ replylen > 0 ? SEND_MORE : 0) == -1) {
+ err:
/* The protocol document says that the client is allowed to simply
* drop the connection after sending NBD_OPT_ABORT, or may read
* the reply.
@@ -77,6 +93,8 @@ send_newstyle_option_reply (uint32_t option, uint32_t reply)
nbdkit_error ("write: %s: %m", name_of_nbd_opt (option));
return -1;
}
+ if (replylen > 0 && conn->send (last_error, replylen, 0) == -1)
+ goto err;
return 0;
}
diff --git a/tests/test-last-error.sh b/tests/test-last-error.sh
new file mode 100755
index 0000000000..fc720606d9
--- /dev/null
+++ b/tests/test-last-error.sh
@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+# nbdkit
+# Copyright Red Hat
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+source ./functions.sh
+set -e
+set -x
+
+# Test informational error messages sent to the NBD client.
+# qemu-img supports this since at least 2.12.0.
+
+requires_run
+requires_plugin eval
+requires qemu-img --version
+
+out=last-error.out
+rm -f $out
+cleanup_fn rm -f $out
+
+export out
+
+nbdkit eval \
+ open=' echo EPERM Go Away >&2; exit 1 ' get_size=' echo 0 '
\
+ --run ' qemu-img info "$uri" > $out 2>&1 ||: '
+cat $out
+
+grep "Go Away" $out
--
2.44.0