Send the last error to the NBD client

resolves: RHEL-50666

0001-server-crypto.c-Fix-fallback-functions-used-when-gnu.patch

@@ -0,0 +1,51 @@
+From 7563596fdb7587dfb8708b5eeeb4b97d738ba79d Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Wed, 24 Jul 2024 11:22:28 +0100
+Subject: [PATCH] server/crypto.c: Fix fallback functions used when gnutls is
+ unavailable
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+The return value was wrong resulting in these errors:
+
+crypto.c: In function ‘nbdkit_peer_tls_dn’:
+crypto.c:945:3: error: return makes pointer from integer without a cast [-Werror]
+   return -1;
+   ^
+crypto.c: In function ‘nbdkit_peer_tls_issuer_dn’:
+crypto.c:953:3: error: return makes pointer from integer without a cast [-Werror]
+   return -1;
+   ^
+
+Fixes: commit a3759199c93300cf9de24a129c4141609dacb047
+Fixes: commit bf77f76112e3ffbc9149a54fbeb0a505310f28a2
+---
+ server/crypto.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/server/crypto.c b/server/crypto.c
+index abdc4801..fa408c75 100644
+--- a/server/crypto.c
++++ b/server/crypto.c
+@@ -942,7 +942,7 @@ nbdkit_peer_tls_dn (void)
+ {
+   nbdkit_error ("%s is not supported on this platform",
+                 "nbdkit_peer_tls_dn");
+-  return -1;
++  return NULL;
+ }
+ 
+ NBDKIT_DLL_PUBLIC char *
+@@ -950,7 +950,7 @@ nbdkit_peer_tls_issuer_dn (void)
+ {
+   nbdkit_error ("%s is not supported on this platform",
+                 "nbdkit_peer_tls_issuer_dn");
+-  return -1;
++  return NULL;
+ }
+ 
+ #endif /* !HAVE_GNUTLS */
+-- 
+2.43.0
+

0002-server-log-Move-preserve-errno-to-log_verror-functio.patch

@@ -0,0 +1,149 @@
+From f2c644d4495d5e75883ff729936102c90489e8d8 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Tue, 23 Jul 2024 14:46:41 +0100
+Subject: [PATCH] server: log: Move preserve errno to log_verror function
+
+This neutral code refactoring just moves the place where we preserve
+errno out one layer, but should have no other effect.
+---
+ server/internal.h   |  8 ++++----
+ server/log-stderr.c |  9 ++-------
+ server/log-syslog.c | 13 ++++---------
+ server/log.c        | 12 ++++++++----
+ 4 files changed, 18 insertions(+), 24 deletions(-)
+
+diff --git a/server/internal.h b/server/internal.h
+index 0b0507e4..1a783e3f 100644
+--- a/server/internal.h
++++ b/server/internal.h
+@@ -340,10 +340,10 @@ extern void free_debug_flags (void);
+ extern void log_verror (const char *fs, va_list args);
+ 
+ /* log-*.c */
+-extern void log_stderr_verror (const char *fs, va_list args)
+-  ATTRIBUTE_FORMAT_PRINTF (1, 0);
+-extern void log_syslog_verror (const char *fs, va_list args)
+-  ATTRIBUTE_FORMAT_PRINTF (1, 0);
++extern void log_stderr_verror (int orig_errno, const char *fs, va_list args)
++  ATTRIBUTE_FORMAT_PRINTF (2, 0);
++extern void log_syslog_verror (int orig_errno, const char *fs, va_list args)
++  ATTRIBUTE_FORMAT_PRINTF (2, 0);
+ 
+ /* vfprintf.c */
+ #if !HAVE_VFPRINTF_PERCENT_M
+diff --git a/server/log-stderr.c b/server/log-stderr.c
+index 8a55f5df..4d8b09da 100644
+--- a/server/log-stderr.c
++++ b/server/log-stderr.c
+@@ -43,12 +43,9 @@
+ 
+ #include "internal.h"
+ 
+-/* Note: preserves the previous value of errno. */
+ void
+-log_stderr_verror (const char *fs, va_list args)
++log_stderr_verror (int orig_errno, const char *fs, va_list args)
+ {
+-  int err = errno;              /* must be first line of function */
+-
+   const char *name = threadlocal_get_name ();
+   size_t instance_num = threadlocal_get_instance_num ();
+   int tty;
+@@ -69,7 +66,7 @@ log_stderr_verror (const char *fs, va_list args)
+   }
+ 
+   fprintf (stderr, "error: ");
+-  errno = err;                  /* must restore in case fs contains %m */
++  errno = orig_errno;        /* must restore in case fs contains %m */
+   vfprintf (stderr, fs, args);
+   fprintf (stderr, "\n");
+ 
+@@ -78,6 +75,4 @@ log_stderr_verror (const char *fs, va_list args)
+ #ifdef HAVE_FUNLOCKFILE
+   funlockfile (stderr);
+ #endif
+-
+-  errno = err;                  /* must be last line of function */
+ }
+diff --git a/server/log-syslog.c b/server/log-syslog.c
+index 76c5035b..29a7a825 100644
+--- a/server/log-syslog.c
++++ b/server/log-syslog.c
+@@ -45,11 +45,9 @@
+ /* Tempted to use LOG_FTP instead of LOG_DAEMON! */
+ static const int PRIORITY = LOG_DAEMON|LOG_ERR;
+ 
+-/* Note: preserves the previous value of errno. */
+ void
+-log_syslog_verror (const char *fs, va_list args)
++log_syslog_verror (int orig_errno, const char *fs, va_list args)
+ {
+-  int err = errno;
+   const char *name = threadlocal_get_name ();
+   size_t instance_num = threadlocal_get_instance_num ();
+   CLEANUP_FREE char *msg = NULL;
+@@ -59,9 +57,9 @@ log_syslog_verror (const char *fs, va_list args)
+   fp = open_memstream (&msg, &len);
+   if (fp == NULL) {
+     /* Fallback to logging using fs, args directly. */
+-    errno = err; /* Must restore in case fs contains %m */
++    errno = orig_errno;      /* must restore in case fs contains %m */
+     vsyslog (PRIORITY, fs, args);
+-    goto out;
++    return;
+   }
+ 
+   if (name) {
+@@ -71,12 +69,9 @@ log_syslog_verror (const char *fs, va_list args)
+     fprintf (fp, ": ");
+   }
+ 
+-  errno = err; /* Must restore in case fs contains %m */
++  errno = orig_errno;        /* must restore in case fs contains %m */
+   vfprintf (fp, fs, args);
+   close_memstream (fp);
+ 
+   syslog (PRIORITY, "%s", msg);
+-
+- out:
+-  errno = err;
+ }
+diff --git a/server/log.c b/server/log.c
+index 464e4f9a..9c1f667a 100644
+--- a/server/log.c
++++ b/server/log.c
+@@ -46,23 +46,27 @@
+ void
+ log_verror (const char *fs, va_list args)
+ {
++  int orig_errno = errno;
++
+   switch (log_to) {
+   case LOG_TO_DEFAULT:
+     if (forked_into_background)
+-      log_syslog_verror (fs, args);
++      log_syslog_verror (orig_errno, fs, args);
+     else
+-      log_stderr_verror (fs, args);
++      log_stderr_verror (orig_errno, fs, args);
+     break;
+   case LOG_TO_SYSLOG:
+-    log_syslog_verror (fs, args);
++    log_syslog_verror (orig_errno, fs, args);
+     break;
+   case LOG_TO_STDERR:
+-    log_stderr_verror (fs, args);
++    log_stderr_verror (orig_errno, fs, args);
+     break;
+   case LOG_TO_NULL:
+     /* nothing */
+     break;
+   }
++
++  errno = orig_errno; /* Restore errno before leaving the function. */
+ }
+ 
+ /* Note: preserves the previous value of errno. */
+-- 
+2.43.0
+

0003-server-Rename-threadlocal_-set-get-_error-to-._errno.patch

@@ -0,0 +1,175 @@
+From 1d7f655726ad3483d0e8086741182aada7ae8595 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Wed, 24 Jul 2024 10:29:13 +0100
+Subject: [PATCH] server: Rename threadlocal_{set,get}_error to .._errno
+
+A simple mechanical change, to avoid confusion with
+threadlocal_{set,get}_last_error introduced in the following commit.
+---
+ server/internal.h    |  4 ++--
+ server/plugins.c     | 27 +++++++++++++--------------
+ server/protocol.c    |  5 +++--
+ server/threadlocal.c |  4 ++--
+ 4 files changed, 20 insertions(+), 20 deletions(-)
+
+diff --git a/server/internal.h b/server/internal.h
+index 1a783e3f..8102ccde 100644
+--- a/server/internal.h
++++ b/server/internal.h
+@@ -569,8 +569,8 @@ extern void threadlocal_set_name (const char *name)
+ extern const char *threadlocal_get_name (void);
+ extern void threadlocal_set_instance_num (size_t instance_num);
+ extern size_t threadlocal_get_instance_num (void);
+-extern void threadlocal_set_error (int err);
+-extern int threadlocal_get_error (void);
++extern void threadlocal_set_errno (int err);
++extern int threadlocal_get_errno (void);
+ extern void *threadlocal_buffer (size_t size);
+ extern void threadlocal_set_conn (struct connection *conn);
+ extern struct connection *threadlocal_get_conn (void);
+diff --git a/server/plugins.c b/server/plugins.c
+index ca89ac7a..3c7df0d2 100644
+--- a/server/plugins.c
++++ b/server/plugins.c
+@@ -633,15 +633,14 @@ plugin_can_cache (struct context *c)
+ NBDKIT_DLL_PUBLIC void
+ nbdkit_set_error (int err)
+ {
+-  threadlocal_set_error (err);
++  threadlocal_set_errno (err);
+ }
+ 
+-/* Grab the appropriate error value.
+- */
++/* Grab the appropriate error value. */
+ static int
+-get_error (struct backend_plugin *p)
++get_errno (struct backend_plugin *p)
+ {
+-  int ret = threadlocal_get_error ();
++  int ret = threadlocal_get_errno ();
+ 
+   if (!ret && p->plugin.errno_is_preserved != 0)
+     ret = errno;
+@@ -664,7 +663,7 @@ plugin_pread (struct context *c,
+   else
+     r = p->plugin._pread_v1 (c->handle, buf, count, offset);
+   if (r == -1)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -685,7 +684,7 @@ plugin_flush (struct context *c,
+     return -1;
+   }
+   if (r == -1)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -715,7 +714,7 @@ plugin_pwrite (struct context *c,
+   if (r != -1 && need_flush)
+     r = plugin_flush (c, 0, err);
+   if (r == -1 && !*err)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -744,7 +743,7 @@ plugin_trim (struct context *c,
+   if (r != -1 && need_flush)
+     r = plugin_flush (c, 0, err);
+   if (r == -1 && !*err)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -782,7 +781,7 @@ plugin_zero (struct context *c,
+     else
+       emulate = true;
+     if (r == -1)
+-      *err = emulate ? EOPNOTSUPP : get_error (p);
++      *err = emulate ? EOPNOTSUPP : get_errno (p);
+     if (r == 0 || (*err != EOPNOTSUPP && *err != ENOTSUP))
+       goto done;
+   }
+@@ -794,7 +793,7 @@ plugin_zero (struct context *c,
+   }
+ 
+   flags &= ~NBDKIT_FLAG_MAY_TRIM;
+-  threadlocal_set_error (0);
++  threadlocal_set_errno (0);
+   *err = 0;
+ 
+   while (count) {
+@@ -814,7 +813,7 @@ plugin_zero (struct context *c,
+   if (r != -1 && need_flush)
+     r = plugin_flush (c, 0, err);
+   if (r == -1 && !*err)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -839,7 +838,7 @@ plugin_extents (struct context *c,
+     r = -1;
+   }
+   if (r == -1)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+@@ -859,7 +858,7 @@ plugin_cache (struct context *c,
+ 
+   r = p->plugin.cache (c->handle, count, offset, flags);
+   if (r == -1)
+-    *err = get_error (p);
++    *err = get_errno (p);
+   return r;
+ }
+ 
+diff --git a/server/protocol.c b/server/protocol.c
+index 9b63f789..677da05c 100644
+--- a/server/protocol.c
++++ b/server/protocol.c
+@@ -235,8 +235,9 @@ handle_request (uint16_t cmd, uint16_t flags, uint64_t offset, uint32_t count,
+   int err = 0;
+ 
+   /* Clear the error, so that we know if the plugin calls
+-   * nbdkit_set_error() or relied on errno.  */
+-  threadlocal_set_error (0);
++   * nbdkit_set_error() or relied on errno.
++   */
++  threadlocal_set_errno (0);
+ 
+   switch (cmd) {
+   case NBD_CMD_READ:
+diff --git a/server/threadlocal.c b/server/threadlocal.c
+index 088fe55a..9bb656bc 100644
+--- a/server/threadlocal.c
++++ b/server/threadlocal.c
+@@ -154,7 +154,7 @@ threadlocal_get_instance_num (void)
+ }
+ 
+ void
+-threadlocal_set_error (int err)
++threadlocal_set_errno (int err)
+ {
+   struct threadlocal *threadlocal = pthread_getspecific (threadlocal_key);
+ 
+@@ -167,7 +167,7 @@ threadlocal_set_error (int err)
+ /* This preserves errno, for convenience.
+  */
+ int
+-threadlocal_get_error (void)
++threadlocal_get_errno (void)
+ {
+   int err = errno;
+   struct threadlocal *threadlocal = pthread_getspecific (threadlocal_key);
+-- 
+2.43.0
+

0004-server-Introduce-threadlocal_-set-get-_last_error.patch

@@ -0,0 +1,93 @@
+From fa5055ae2b9f96af941d697de39198c96ee2580a Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Wed, 24 Jul 2024 10:37:58 +0100
+Subject: [PATCH] server: Introduce threadlocal_{set,get}_last_error
+
+Plus a function to clear the last_error field.
+---
+ server/internal.h    |  3 +++
+ server/threadlocal.c | 40 ++++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 43 insertions(+)
+
+diff --git a/server/internal.h b/server/internal.h
+index 8102ccde..c45384a6 100644
+--- a/server/internal.h
++++ b/server/internal.h
+@@ -571,6 +571,9 @@ extern void threadlocal_set_instance_num (size_t instance_num);
+ extern size_t threadlocal_get_instance_num (void);
+ extern void threadlocal_set_errno (int err);
+ extern int threadlocal_get_errno (void);
++extern void threadlocal_set_last_error (char *msg);
++extern void threadlocal_clear_last_error (void);
++extern const char *threadlocal_get_last_error (void);
+ extern void *threadlocal_buffer (size_t size);
+ extern void threadlocal_set_conn (struct connection *conn);
+ extern struct connection *threadlocal_get_conn (void);
+diff --git a/server/threadlocal.c b/server/threadlocal.c
+index 9bb656bc..74a3c4e5 100644
+--- a/server/threadlocal.c
++++ b/server/threadlocal.c
+@@ -56,6 +56,7 @@ struct threadlocal {
+   char *name;                   /* Can be NULL. */
+   size_t instance_num;          /* Can be 0. */
+   int err;
++  char *last_error;             /* Can be NULL. */
+   void *buffer;                 /* Can be NULL. */
+   size_t buffer_size;
+   struct connection *conn;      /* Can be NULL. */
+@@ -70,6 +71,7 @@ free_threadlocal (void *threadlocalv)
+   struct threadlocal *threadlocal = threadlocalv;
+ 
+   free (threadlocal->name);
++  free (threadlocal->last_error);
+   free (threadlocal->buffer);
+   free (threadlocal);
+ }
+@@ -176,6 +178,44 @@ threadlocal_get_errno (void)
+   return threadlocal ? threadlocal->err : 0;
+ }
+ 
++/* Set the last_error field.  The ownership of the 'msg' string is
++ * passed to the threadlocal and will be freed here.
++ */
++void
++threadlocal_set_last_error (char *msg)
++{
++  struct threadlocal *threadlocal = pthread_getspecific (threadlocal_key);
++
++  if (threadlocal) {
++    free (threadlocal->last_error);
++    threadlocal->last_error = msg;
++  }
++  else {
++    /* ... otherwise throw it away, it's informational. */
++    free (msg);
++  }
++}
++
++void
++threadlocal_clear_last_error (void)
++{
++  threadlocal_set_last_error (NULL);
++}
++
++/* Get the last_error field.  If successful, this returns a non-NULL
++ * string.  This is valid until something calls nbdkit_error() in the
++ * same thread, so it should be used quickly.  Returning NULL is not
++ * necessarily an error.  The last_error is informational and may not
++ * be available.
++ */
++const char *
++threadlocal_get_last_error (void)
++{
++  struct threadlocal *threadlocal = pthread_getspecific (threadlocal_key);
++
++  return threadlocal ? threadlocal->last_error : NULL;
++}
++
+ /* Return the single pread/pwrite buffer for this thread.  The buffer
+  * size is increased to ‘size’ bytes if required.
+  *
+-- 
+2.43.0
+

0005-server-Take-a-thread-local-copy-of-the-last-call-to-.patch

@@ -0,0 +1,93 @@
+From bfa6d4064cb74f429149d14ab4025b258fc95ec4 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Tue, 23 Jul 2024 15:28:06 +0100
+Subject: [PATCH] server: Take a thread-local copy of the last call to
+ nbdkit_error
+
+nbdkit_error has traditionally been a "fancy wrapper around fprintf"
+(kind of, don't take that literally).  It is encouraged that plugins
+and filters do something like:
+
+  if (error) {
+    nbdkit_error ("oops, a bad thing happened");
+    return -1;
+  }
+
+but we don't enforce this.  Plugins might call nbdkit_error more than
+once or not at all.
+
+The point where we get to sending an error back over the wire to the
+NBD client is long after the plugin returned above, and after
+nbdkit_error was called.
+
+Therefore in order to send errors back to the NBD client, we must keep
+the last error message around.
+
+This change simply modifies nbdkit_error to make a best-effort attempt
+to save the last error message in thread-local storage.
+
+We also clear the last error when a new request starts, to ensure that
+we don't leak errors across different callbacks or connections.
+---
+ server/log.c      | 21 +++++++++++++++++++++
+ server/protocol.c |  5 +++++
+ 2 files changed, 26 insertions(+)
+
+diff --git a/server/log.c b/server/log.c
+index 9c1f667a..acf14d57 100644
+--- a/server/log.c
++++ b/server/log.c
+@@ -40,6 +40,25 @@
+ 
+ #include "internal.h"
+ 
++/* Copy the error message to threadlocal.  This is sent to callers
++ * which are using structured replies, but is for extra information
++ * only so don't fail if we are unable to copy it.
++ */
++static void
++copy_error_to_threadlocal (int orig_errno, const char *fs, va_list args)
++{
++  va_list args_copy;
++  char *msg;
++  int r;
++
++  va_copy (args_copy, args);
++  errno = orig_errno;        /* must restore in case fs contains %m */
++  r = vasprintf (&msg, fs, args_copy);
++  va_end (args_copy);
++  if (r != -1 && msg)
++    threadlocal_set_last_error (msg); /* ownership passed to threadlocal */
++}
++
+ /* Call the right log_*_verror function depending on log_sink.
+  * Note: preserves the previous value of errno.
+  */
+@@ -48,6 +67,8 @@ log_verror (const char *fs, va_list args)
+ {
+   int orig_errno = errno;
+ 
++  copy_error_to_threadlocal (orig_errno, fs, args);
++
+   switch (log_to) {
+   case LOG_TO_DEFAULT:
+     if (forked_into_background)
+diff --git a/server/protocol.c b/server/protocol.c
+index 677da05c..d428bfc8 100644
+--- a/server/protocol.c
++++ b/server/protocol.c
+@@ -239,6 +239,11 @@ handle_request (uint16_t cmd, uint16_t flags, uint64_t offset, uint32_t count,
+    */
+   threadlocal_set_errno (0);
+ 
++  /* Also clear the last error in this thread so we will only save
++   * nbdkit_error() from this request.
++   */
++  threadlocal_clear_last_error ();
++
+   switch (cmd) {
+   case NBD_CMD_READ:
+     if (backend_pread (c, buf, count, offset, 0, &err) == -1)
+-- 
+2.43.0
+

0006-server-Send-the-last-error-to-the-NBD-client.patch

@@ -0,0 +1,175 @@
+From 46484ca8e6a35c45fe96b6c972ceba8984d401e8 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Tue, 23 Jul 2024 15:45:04 +0100
+Subject: [PATCH] server: Send the last error to the NBD client
+
+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.
+---
+ server/protocol-handshake-newstyle.c | 43 ++++++++++++++++------
+ tests/Makefile.am                    |  2 +
+ tests/test-last-error.sh             | 55 ++++++++++++++++++++++++++++
+ 3 files changed, 88 insertions(+), 12 deletions(-)
+ create mode 100755 tests/test-last-error.sh
+
+diff --git a/server/protocol-handshake-newstyle.c b/server/protocol-handshake-newstyle.c
+index 6b3bc76f..c18d32e5 100644
+--- a/server/protocol-handshake-newstyle.c
++++ b/server/protocol-handshake-newstyle.c
+@@ -57,28 +57,47 @@ 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) {
+-    /* The protocol document says that the client is allowed to simply
+-     * drop the connection after sending NBD_OPT_ABORT, or may read
+-     * the reply.
+-     */
+-    if (option == NBD_OPT_ABORT)
+-      debug ("write: %s: %m", name_of_nbd_opt (option));
+-    else
+-      nbdkit_error ("write: %s: %m", name_of_nbd_opt (option));
+-    return -1;
+-  }
++                  sizeof fixed_new_option_reply,
++                  replylen > 0 ? SEND_MORE : 0) == -1)
++    goto err;
++  if (replylen > 0 && conn->send (last_error, replylen, 0) == -1)
++    goto err;
+ 
+   return 0;
++
++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.
++   */
++  if (option == NBD_OPT_ABORT)
++    debug ("write: %s: %m", name_of_nbd_opt (option));
++  else
++    nbdkit_error ("write: %s: %m", name_of_nbd_opt (option));
++  return -1;
+ }
+ 
+ /* Reply to NBD_OPT_LIST with the plugin's list of export names.
+diff --git a/tests/Makefile.am b/tests/Makefile.am
+index 8c7d6b8c..89c5fa9d 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/tests/test-last-error.sh b/tests/test-last-error.sh
+new file mode 100755
+index 00000000..fc720606
+--- /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
+-- 
+2.43.0
+

copy-patches.sh

@@ -6,7 +6,7 @@ set -e
 # directory.  Use it like this:
 #   ./copy-patches.sh
 
-rhel_version=8.3
+rhel_version=10.0
 
 # Check we're in the right directory.
 if [ ! -f nbdkit.spec ]; then

nbdkit.spec

@@ -55,7 +55,7 @@
 
 Name:           nbdkit
 Version:        1.40.0
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        NBD server
 
 License:        BSD-3-Clause
@@ -76,6 +76,17 @@ Source2:        libguestfs.keyring
 # Maintainer script which helps with handling patches.
 Source3:        copy-patches.sh
 
+# Patches come from the upstream repository:
+# https://gitlab.com/nbdkit/nbdkit/-/commits/rhel-10.0/
+
+# Patches.
+Patch0001:     0001-server-crypto.c-Fix-fallback-functions-used-when-gnu.patch
+Patch0002:     0002-server-log-Move-preserve-errno-to-log_verror-functio.patch
+Patch0003:     0003-server-Rename-threadlocal_-set-get-_error-to-._errno.patch
+Patch0004:     0004-server-Introduce-threadlocal_-set-get-_last_error.patch
+Patch0005:     0005-server-Take-a-thread-local-copy-of-the-last-call-to-.patch
+Patch0006:     0006-server-Send-the-last-error-to-the-NBD-client.patch
+
 # For automatic RPM Provides generation.
 # See: https://rpm-software-management.github.io/rpm/manual/dependency_generators.html
 Source4:        nbdkit.attr
@@ -1492,9 +1503,11 @@ fi
 
 
 %changelog
-* Mon Jul 22 2024 Richard W.M. Jones <rjones@redhat.com> - 1.40.0-1
+* Fri Jul 26 2024 Richard W.M. Jones <rjones@redhat.com> - 1.40.0-2
 - Rebase to nbdkit 1.40.0
   related: RHEL-49594
+- Send the last error to the NBD client
+  resolves: RHEL-50666
 
 * Fri Jul 12 2024 Richard W.M. Jones <rjones@redhat.com> - 1.38.0-6
 - Re-add libxcrypt dependency