qemu

server.c (87575B)

---

 /*
  *  Copyright (C) 2016-2022 Red Hat, Inc.
  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
  *
  *  Network Block Device Server Side
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; under version 2 of the License.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "qemu/osdep.h"
 
 #include "block/export.h"
 #include "qapi/error.h"
 #include "qemu/queue.h"
 #include "trace.h"
 #include "nbd-internal.h"
 #include "qemu/units.h"
 #include "qemu/memalign.h"
 
 #define NBD_META_ID_BASE_ALLOCATION 0
 #define NBD_META_ID_ALLOCATION_DEPTH 1
 /* Dirty bitmaps use 'NBD_META_ID_DIRTY_BITMAP + i', so keep this id last. */
 #define NBD_META_ID_DIRTY_BITMAP 2
 
 /*
  * NBD_MAX_BLOCK_STATUS_EXTENTS: 1 MiB of extents data. An empirical
  * constant. If an increase is needed, note that the NBD protocol
  * recommends no larger than 32 mb, so that the client won't consider
  * the reply as a denial of service attack.
  */
 #define NBD_MAX_BLOCK_STATUS_EXTENTS (1 * MiB / 8)
 
 static int system_errno_to_nbd_errno(int err)
 {
     switch (err) {
     case 0:
         return NBD_SUCCESS;
     case EPERM:
     case EROFS:
         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 EOVERFLOW:
         return NBD_EOVERFLOW;
     case ENOTSUP:
 #if ENOTSUP != EOPNOTSUPP
     case EOPNOTSUPP:
 #endif
         return NBD_ENOTSUP;
     case ESHUTDOWN:
         return NBD_ESHUTDOWN;
     case EINVAL:
     default:
         return NBD_EINVAL;
     }
 }
 
 /* Definitions for opaque data types */
 
 typedef struct NBDRequestData NBDRequestData;
 
 struct NBDRequestData {
     NBDClient *client;
     uint8_t *data;
     bool complete;
 };
 
 struct NBDExport {
     BlockExport common;
 
     char *name;
     char *description;
     uint64_t size;
     uint16_t nbdflags;
     QTAILQ_HEAD(, NBDClient) clients;
     QTAILQ_ENTRY(NBDExport) next;
 
     BlockBackend *eject_notifier_blk;
     Notifier eject_notifier;
 
     bool allocation_depth;
     BdrvDirtyBitmap **export_bitmaps;
     size_t nr_export_bitmaps;
 };
 
 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
 
 /* NBDExportMetaContexts represents a list of contexts to be exported,
  * as selected by NBD_OPT_SET_META_CONTEXT. Also used for
  * NBD_OPT_LIST_META_CONTEXT. */
 typedef struct NBDExportMetaContexts {
     NBDExport *exp;
     size_t count; /* number of negotiated contexts */
     bool base_allocation; /* export base:allocation context (block status) */
     bool allocation_depth; /* export qemu:allocation-depth */
     bool *bitmaps; /*
                     * export qemu:dirty-bitmap:<export bitmap name>,
                     * sized by exp->nr_export_bitmaps
                     */
 } NBDExportMetaContexts;
 
 struct NBDClient {
     int refcount;
     void (*close_fn)(NBDClient *client, bool negotiated);
 
     NBDExport *exp;
     QCryptoTLSCreds *tlscreds;
     char *tlsauthz;
     QIOChannelSocket *sioc; /* The underlying data channel */
     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
 
     Coroutine *recv_coroutine;
 
     CoMutex send_lock;
     Coroutine *send_coroutine;
 
     bool read_yielding;
     bool quiescing;
 
     QTAILQ_ENTRY(NBDClient) next;
     int nb_requests;
     bool closing;
 
     uint32_t check_align; /* If non-zero, check for aligned client requests */
 
     bool structured_reply;
     NBDExportMetaContexts export_meta;
 
     uint32_t opt; /* Current option being negotiated */
     uint32_t optlen; /* remaining length of data in ioc for the option being
                         negotiated now */
 };
 
 static void nbd_client_receive_next_request(NBDClient *client);
 
 /* Basic flow for negotiation
 
    Server         Client
    Negotiate
 
    or
 
    Server         Client
    Negotiate #1
                   Option
    Negotiate #2
 
    ----
 
    followed by
 
    Server         Client
                   Request
    Response
                   Request
    Response
                   ...
    ...
                   Request (type == 2)
 
 */
 
 static inline void set_be_option_rep(NBDOptionReply *rep, uint32_t option,
                                      uint32_t type, uint32_t length)
 {
     stq_be_p(&rep->magic, NBD_REP_MAGIC);
     stl_be_p(&rep->option, option);
     stl_be_p(&rep->type, type);
     stl_be_p(&rep->length, length);
 }
 
 /* Send a reply header, including length, but no payload.
  * Return -errno on error, 0 on success. */
 static int nbd_negotiate_send_rep_len(NBDClient *client, uint32_t type,
                                       uint32_t len, Error **errp)
 {
     NBDOptionReply rep;
 
     trace_nbd_negotiate_send_rep_len(client->opt, nbd_opt_lookup(client->opt),
                                      type, nbd_rep_lookup(type), len);
 
     assert(len < NBD_MAX_BUFFER_SIZE);
 
     set_be_option_rep(&rep, client->opt, type, len);
     return nbd_write(client->ioc, &rep, sizeof(rep), errp);
 }
 
 /* Send a reply header with default 0 length.
  * Return -errno on error, 0 on success. */
 static int nbd_negotiate_send_rep(NBDClient *client, uint32_t type,
                                   Error **errp)
 {
     return nbd_negotiate_send_rep_len(client, type, 0, errp);
 }
 
 /* Send an error reply.
  * Return -errno on error, 0 on success. */
 static int G_GNUC_PRINTF(4, 0)
 nbd_negotiate_send_rep_verr(NBDClient *client, uint32_t type,
                             Error **errp, const char *fmt, va_list va)
 {
     ERRP_GUARD();
     g_autofree char *msg = NULL;
     int ret;
     size_t len;
 
     msg = g_strdup_vprintf(fmt, va);
     len = strlen(msg);
     assert(len < NBD_MAX_STRING_SIZE);
     trace_nbd_negotiate_send_rep_err(msg);
     ret = nbd_negotiate_send_rep_len(client, type, len, errp);
     if (ret < 0) {
         return ret;
     }
     if (nbd_write(client->ioc, msg, len, errp) < 0) {
         error_prepend(errp, "write failed (error message): ");
         return -EIO;
     }
 
     return 0;
 }
 
 /*
  * Return a malloc'd copy of @name suitable for use in an error reply.
  */
 static char *
 nbd_sanitize_name(const char *name)
 {
     if (strnlen(name, 80) < 80) {
         return g_strdup(name);
     }
     /* XXX Should we also try to sanitize any control characters? */
     return g_strdup_printf("%.80s...", name);
 }
 
 /* Send an error reply.
  * Return -errno on error, 0 on success. */
 static int G_GNUC_PRINTF(4, 5)
 nbd_negotiate_send_rep_err(NBDClient *client, uint32_t type,
                            Error **errp, const char *fmt, ...)
 {
     va_list va;
     int ret;
 
     va_start(va, fmt);
     ret = nbd_negotiate_send_rep_verr(client, type, errp, fmt, va);
     va_end(va);
     return ret;
 }
 
 /* Drop remainder of the current option, and send a reply with the
  * given error type and message. Return -errno on read or write
  * failure; or 0 if connection is still live. */
 static int G_GNUC_PRINTF(4, 0)
 nbd_opt_vdrop(NBDClient *client, uint32_t type, Error **errp,
               const char *fmt, va_list va)
 {
     int ret = nbd_drop(client->ioc, client->optlen, errp);
 
     client->optlen = 0;
     if (!ret) {
         ret = nbd_negotiate_send_rep_verr(client, type, errp, fmt, va);
     }
     return ret;
 }
 
 static int G_GNUC_PRINTF(4, 5)
 nbd_opt_drop(NBDClient *client, uint32_t type, Error **errp,
              const char *fmt, ...)
 {
     int ret;
     va_list va;
 
     va_start(va, fmt);
     ret = nbd_opt_vdrop(client, type, errp, fmt, va);
     va_end(va);
 
     return ret;
 }
 
 static int G_GNUC_PRINTF(3, 4)
 nbd_opt_invalid(NBDClient *client, Error **errp, const char *fmt, ...)
 {
     int ret;
     va_list va;
 
     va_start(va, fmt);
     ret = nbd_opt_vdrop(client, NBD_REP_ERR_INVALID, errp, fmt, va);
     va_end(va);
 
     return ret;
 }
 
 /* Read size bytes from the unparsed payload of the current option.
  * If @check_nul, require that no NUL bytes appear in buffer.
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
 static int nbd_opt_read(NBDClient *client, void *buffer, size_t size,
                         bool check_nul, Error **errp)
 {
     if (size > client->optlen) {
         return nbd_opt_invalid(client, errp,
                                "Inconsistent lengths in option %s",
                                nbd_opt_lookup(client->opt));
     }
     client->optlen -= size;
     if (qio_channel_read_all(client->ioc, buffer, size, errp) < 0) {
         return -EIO;
     }
 
     if (check_nul && strnlen(buffer, size) != size) {
         return nbd_opt_invalid(client, errp,
                                "Unexpected embedded NUL in option %s",
                                nbd_opt_lookup(client->opt));
     }
     return 1;
 }
 
 /* Drop size bytes from the unparsed payload of the current option.
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
 static int nbd_opt_skip(NBDClient *client, size_t size, Error **errp)
 {
     if (size > client->optlen) {
         return nbd_opt_invalid(client, errp,
                                "Inconsistent lengths in option %s",
                                nbd_opt_lookup(client->opt));
     }
     client->optlen -= size;
     return nbd_drop(client->ioc, size, errp) < 0 ? -EIO : 1;
 }
 
 /* nbd_opt_read_name
  *
  * Read a string with the format:
  *   uint32_t len     (<= NBD_MAX_STRING_SIZE)
  *   len bytes string (not 0-terminated)
  *
  * On success, @name will be allocated.
  * If @length is non-null, it will be set to the actual string length.
  *
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success.
  */
 static int nbd_opt_read_name(NBDClient *client, char **name, uint32_t *length,
                              Error **errp)
 {
     int ret;
     uint32_t len;
     g_autofree char *local_name = NULL;
 
     *name = NULL;
     ret = nbd_opt_read(client, &len, sizeof(len), false, errp);
     if (ret <= 0) {
         return ret;
     }
     len = cpu_to_be32(len);
 
     if (len > NBD_MAX_STRING_SIZE) {
         return nbd_opt_invalid(client, errp,
                                "Invalid name length: %" PRIu32, len);
     }
 
     local_name = g_malloc(len + 1);
     ret = nbd_opt_read(client, local_name, len, true, errp);
     if (ret <= 0) {
         return ret;
     }
     local_name[len] = '\0';
 
     if (length) {
         *length = len;
     }
     *name = g_steal_pointer(&local_name);
 
     return 1;
 }
 
 /* Send a single NBD_REP_SERVER reply to NBD_OPT_LIST, including payload.
  * Return -errno on error, 0 on success. */
 static int nbd_negotiate_send_rep_list(NBDClient *client, NBDExport *exp,
                                        Error **errp)
 {
     ERRP_GUARD();
     size_t name_len, desc_len;
     uint32_t len;
     const char *name = exp->name ? exp->name : "";
     const char *desc = exp->description ? exp->description : "";
     QIOChannel *ioc = client->ioc;
     int ret;
 
     trace_nbd_negotiate_send_rep_list(name, desc);
     name_len = strlen(name);
     desc_len = strlen(desc);
     assert(name_len <= NBD_MAX_STRING_SIZE && desc_len <= NBD_MAX_STRING_SIZE);
     len = name_len + desc_len + sizeof(len);
     ret = nbd_negotiate_send_rep_len(client, NBD_REP_SERVER, len, errp);
     if (ret < 0) {
         return ret;
     }
 
     len = cpu_to_be32(name_len);
     if (nbd_write(ioc, &len, sizeof(len), errp) < 0) {
         error_prepend(errp, "write failed (name length): ");
         return -EINVAL;
     }
 
     if (nbd_write(ioc, name, name_len, errp) < 0) {
         error_prepend(errp, "write failed (name buffer): ");
         return -EINVAL;
     }
 
     if (nbd_write(ioc, desc, desc_len, errp) < 0) {
         error_prepend(errp, "write failed (description buffer): ");
         return -EINVAL;
     }
 
     return 0;
 }
 
 /* Process the NBD_OPT_LIST command, with a potential series of replies.
  * Return -errno on error, 0 on success. */
 static int nbd_negotiate_handle_list(NBDClient *client, Error **errp)
 {
     NBDExport *exp;
     assert(client->opt == NBD_OPT_LIST);
 
     /* For each export, send a NBD_REP_SERVER reply. */
     QTAILQ_FOREACH(exp, &exports, next) {
         if (nbd_negotiate_send_rep_list(client, exp, errp)) {
             return -EINVAL;
         }
     }
     /* Finish with a NBD_REP_ACK. */
     return nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
 }
 
 static void nbd_check_meta_export(NBDClient *client)
 {
     if (client->exp != client->export_meta.exp) {
         client->export_meta.count = 0;
     }
 }
 
 /* Send a reply to NBD_OPT_EXPORT_NAME.
  * Return -errno on error, 0 on success. */
 static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
                                             Error **errp)
 {
     ERRP_GUARD();
     g_autofree char *name = NULL;
     char buf[NBD_REPLY_EXPORT_NAME_SIZE] = "";
     size_t len;
     int ret;
     uint16_t myflags;
 
     /* Client sends:
         [20 ..  xx]   export name (length bytes)
        Server replies:
         [ 0 ..   7]   size
         [ 8 ..   9]   export flags
         [10 .. 133]   reserved     (0) [unless no_zeroes]
      */
     trace_nbd_negotiate_handle_export_name();
     if (client->optlen > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "Bad length received");
         return -EINVAL;
     }
     name = g_malloc(client->optlen + 1);
     if (nbd_read(client->ioc, name, client->optlen, "export name", errp) < 0) {
         return -EIO;
     }
     name[client->optlen] = '\0';
     client->optlen = 0;
 
     trace_nbd_negotiate_handle_export_name_request(name);
 
     client->exp = nbd_export_find(name);
     if (!client->exp) {
         error_setg(errp, "export not found");
         return -EINVAL;
     }
 
     myflags = client->exp->nbdflags;
     if (client->structured_reply) {
         myflags |= NBD_FLAG_SEND_DF;
     }
     trace_nbd_negotiate_new_style_size_flags(client->exp->size, myflags);
     stq_be_p(buf, client->exp->size);
     stw_be_p(buf + 8, myflags);
     len = no_zeroes ? 10 : sizeof(buf);
     ret = nbd_write(client->ioc, buf, len, errp);
     if (ret < 0) {
         error_prepend(errp, "write failed: ");
         return ret;
     }
 
     QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
     blk_exp_ref(&client->exp->common);
     nbd_check_meta_export(client);
 
     return 0;
 }
 
 /* Send a single NBD_REP_INFO, with a buffer @buf of @length bytes.
  * The buffer does NOT include the info type prefix.
  * Return -errno on error, 0 if ready to send more. */
 static int nbd_negotiate_send_info(NBDClient *client,
                                    uint16_t info, uint32_t length, void *buf,
                                    Error **errp)
 {
     int rc;
 
     trace_nbd_negotiate_send_info(info, nbd_info_lookup(info), length);
     rc = nbd_negotiate_send_rep_len(client, NBD_REP_INFO,
                                     sizeof(info) + length, errp);
     if (rc < 0) {
         return rc;
     }
     info = cpu_to_be16(info);
     if (nbd_write(client->ioc, &info, sizeof(info), errp) < 0) {
         return -EIO;
     }
     if (nbd_write(client->ioc, buf, length, errp) < 0) {
         return -EIO;
     }
     return 0;
 }
 
 /* nbd_reject_length: Handle any unexpected payload.
  * @fatal requests that we quit talking to the client, even if we are able
  * to successfully send an error reply.
  * Return:
  * -errno  transmission error occurred or @fatal was requested, errp is set
  * 0       error message successfully sent to client, errp is not set
  */
 static int nbd_reject_length(NBDClient *client, bool fatal, Error **errp)
 {
     int ret;
 
     assert(client->optlen);
     ret = nbd_opt_invalid(client, errp, "option '%s' has unexpected length",
                           nbd_opt_lookup(client->opt));
     if (fatal && !ret) {
         error_setg(errp, "option '%s' has unexpected length",
                    nbd_opt_lookup(client->opt));
         return -EINVAL;
     }
     return ret;
 }
 
 /* Handle NBD_OPT_INFO and NBD_OPT_GO.
  * Return -errno on error, 0 if ready for next option, and 1 to move
  * into transmission phase.  */
 static int nbd_negotiate_handle_info(NBDClient *client, Error **errp)
 {
     int rc;
     g_autofree char *name = NULL;
     NBDExport *exp;
     uint16_t requests;
     uint16_t request;
     uint32_t namelen = 0;
     bool sendname = false;
     bool blocksize = false;
     uint32_t sizes[3];
     char buf[sizeof(uint64_t) + sizeof(uint16_t)];
     uint32_t check_align = 0;
     uint16_t myflags;
 
     /* Client sends:
         4 bytes: L, name length (can be 0)
         L bytes: export name
         2 bytes: N, number of requests (can be 0)
         N * 2 bytes: N requests
     */
     rc = nbd_opt_read_name(client, &name, &namelen, errp);
     if (rc <= 0) {
         return rc;
     }
     trace_nbd_negotiate_handle_export_name_request(name);
 
     rc = nbd_opt_read(client, &requests, sizeof(requests), false, errp);
     if (rc <= 0) {
         return rc;
     }
     requests = be16_to_cpu(requests);
     trace_nbd_negotiate_handle_info_requests(requests);
     while (requests--) {
         rc = nbd_opt_read(client, &request, sizeof(request), false, errp);
         if (rc <= 0) {
             return rc;
         }
         request = be16_to_cpu(request);
         trace_nbd_negotiate_handle_info_request(request,
                                                 nbd_info_lookup(request));
         /* We care about NBD_INFO_NAME and NBD_INFO_BLOCK_SIZE;
          * everything else is either a request we don't know or
          * something we send regardless of request */
         switch (request) {
         case NBD_INFO_NAME:
             sendname = true;
             break;
         case NBD_INFO_BLOCK_SIZE:
             blocksize = true;
             break;
         }
     }
     if (client->optlen) {
         return nbd_reject_length(client, false, errp);
     }
 
     exp = nbd_export_find(name);
     if (!exp) {
         g_autofree char *sane_name = nbd_sanitize_name(name);
 
         return nbd_negotiate_send_rep_err(client, NBD_REP_ERR_UNKNOWN,
                                           errp, "export '%s' not present",
                                           sane_name);
     }
 
     /* Don't bother sending NBD_INFO_NAME unless client requested it */
     if (sendname) {
         rc = nbd_negotiate_send_info(client, NBD_INFO_NAME, namelen, name,
                                      errp);
         if (rc < 0) {
             return rc;
         }
     }
 
     /* Send NBD_INFO_DESCRIPTION only if available, regardless of
      * client request */
     if (exp->description) {
         size_t len = strlen(exp->description);
 
         assert(len <= NBD_MAX_STRING_SIZE);
         rc = nbd_negotiate_send_info(client, NBD_INFO_DESCRIPTION,
                                      len, exp->description, errp);
         if (rc < 0) {
             return rc;
         }
     }
 
     /* Send NBD_INFO_BLOCK_SIZE always, but tweak the minimum size
      * according to whether the client requested it, and according to
      * whether this is OPT_INFO or OPT_GO. */
     /* minimum - 1 for back-compat, or actual if client will obey it. */
     if (client->opt == NBD_OPT_INFO || blocksize) {
         check_align = sizes[0] = blk_get_request_alignment(exp->common.blk);
     } else {
         sizes[0] = 1;
     }
     assert(sizes[0] <= NBD_MAX_BUFFER_SIZE);
     /* preferred - Hard-code to 4096 for now.
      * TODO: is blk_bs(blk)->bl.opt_transfer appropriate? */
     sizes[1] = MAX(4096, sizes[0]);
     /* maximum - At most 32M, but smaller as appropriate. */
     sizes[2] = MIN(blk_get_max_transfer(exp->common.blk), NBD_MAX_BUFFER_SIZE);
     trace_nbd_negotiate_handle_info_block_size(sizes[0], sizes[1], sizes[2]);
     sizes[0] = cpu_to_be32(sizes[0]);
     sizes[1] = cpu_to_be32(sizes[1]);
     sizes[2] = cpu_to_be32(sizes[2]);
     rc = nbd_negotiate_send_info(client, NBD_INFO_BLOCK_SIZE,
                                  sizeof(sizes), sizes, errp);
     if (rc < 0) {
         return rc;
     }
 
     /* Send NBD_INFO_EXPORT always */
     myflags = exp->nbdflags;
     if (client->structured_reply) {
         myflags |= NBD_FLAG_SEND_DF;
     }
     trace_nbd_negotiate_new_style_size_flags(exp->size, myflags);
     stq_be_p(buf, exp->size);
     stw_be_p(buf + 8, myflags);
     rc = nbd_negotiate_send_info(client, NBD_INFO_EXPORT,
                                  sizeof(buf), buf, errp);
     if (rc < 0) {
         return rc;
     }
 
     /*
      * If the client is just asking for NBD_OPT_INFO, but forgot to
      * request block sizes in a situation that would impact
      * performance, then return an error. But for NBD_OPT_GO, we
      * tolerate all clients, regardless of alignments.
      */
     if (client->opt == NBD_OPT_INFO && !blocksize &&
         blk_get_request_alignment(exp->common.blk) > 1) {
         return nbd_negotiate_send_rep_err(client,
                                           NBD_REP_ERR_BLOCK_SIZE_REQD,
                                           errp,
                                           "request NBD_INFO_BLOCK_SIZE to "
                                           "use this export");
     }
 
     /* Final reply */
     rc = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
     if (rc < 0) {
         return rc;
     }
 
     if (client->opt == NBD_OPT_GO) {
         client->exp = exp;
         client->check_align = check_align;
         QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
         blk_exp_ref(&client->exp->common);
         nbd_check_meta_export(client);
         rc = 1;
     }
     return rc;
 }
 
 
 /* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the
  * new channel for all further (now-encrypted) communication. */
 static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
                                                  Error **errp)
 {
     QIOChannel *ioc;
     QIOChannelTLS *tioc;
     struct NBDTLSHandshakeData data = { 0 };
 
     assert(client->opt == NBD_OPT_STARTTLS);
 
     trace_nbd_negotiate_handle_starttls();
     ioc = client->ioc;
 
     if (nbd_negotiate_send_rep(client, NBD_REP_ACK, errp) < 0) {
         return NULL;
     }
 
     tioc = qio_channel_tls_new_server(ioc,
                                       client->tlscreds,
                                       client->tlsauthz,
                                       errp);
     if (!tioc) {
         return NULL;
     }
 
     qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-server-tls");
     trace_nbd_negotiate_handle_starttls_handshake();
     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
     qio_channel_tls_handshake(tioc,
                               nbd_tls_handshake,
                               &data,
                               NULL,
                               NULL);
 
     if (!data.complete) {
         g_main_loop_run(data.loop);
     }
     g_main_loop_unref(data.loop);
     if (data.error) {
         object_unref(OBJECT(tioc));
         error_propagate(errp, data.error);
         return NULL;
     }
 
     return QIO_CHANNEL(tioc);
 }
 
 /* nbd_negotiate_send_meta_context
  *
  * Send one chunk of reply to NBD_OPT_{LIST,SET}_META_CONTEXT
  *
  * For NBD_OPT_LIST_META_CONTEXT @context_id is ignored, 0 is used instead.
  */
 static int nbd_negotiate_send_meta_context(NBDClient *client,
                                            const char *context,
                                            uint32_t context_id,
                                            Error **errp)
 {
     NBDOptionReplyMetaContext opt;
     struct iovec iov[] = {
         {.iov_base = &opt, .iov_len = sizeof(opt)},
         {.iov_base = (void *)context, .iov_len = strlen(context)}
     };
 
     assert(iov[1].iov_len <= NBD_MAX_STRING_SIZE);
     if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
         context_id = 0;
     }
 
     trace_nbd_negotiate_meta_query_reply(context, context_id);
     set_be_option_rep(&opt.h, client->opt, NBD_REP_META_CONTEXT,
                       sizeof(opt) - sizeof(opt.h) + iov[1].iov_len);
     stl_be_p(&opt.context_id, context_id);
 
     return qio_channel_writev_all(client->ioc, iov, 2, errp) < 0 ? -EIO : 0;
 }
 
 /*
  * Return true if @query matches @pattern, or if @query is empty when
  * the @client is performing _LIST_.
  */
 static bool nbd_meta_empty_or_pattern(NBDClient *client, const char *pattern,
                                       const char *query)
 {
     if (!*query) {
         trace_nbd_negotiate_meta_query_parse("empty");
         return client->opt == NBD_OPT_LIST_META_CONTEXT;
     }
     if (strcmp(query, pattern) == 0) {
         trace_nbd_negotiate_meta_query_parse(pattern);
         return true;
     }
     trace_nbd_negotiate_meta_query_skip("pattern not matched");
     return false;
 }
 
 /*
  * Return true and adjust @str in place if it begins with @prefix.
  */
 static bool nbd_strshift(const char **str, const char *prefix)
 {
     size_t len = strlen(prefix);
 
     if (strncmp(*str, prefix, len) == 0) {
         *str += len;
         return true;
     }
     return false;
 }
 
 /* nbd_meta_base_query
  *
  * Handle queries to 'base' namespace. For now, only the base:allocation
  * context is available.  Return true if @query has been handled.
  */
 static bool nbd_meta_base_query(NBDClient *client, NBDExportMetaContexts *meta,
                                 const char *query)
 {
     if (!nbd_strshift(&query, "base:")) {
         return false;
     }
     trace_nbd_negotiate_meta_query_parse("base:");
 
     if (nbd_meta_empty_or_pattern(client, "allocation", query)) {
         meta->base_allocation = true;
     }
     return true;
 }
 
 /* nbd_meta_qemu_query
  *
  * Handle queries to 'qemu' namespace. For now, only the qemu:dirty-bitmap:
  * and qemu:allocation-depth contexts are available.  Return true if @query
  * has been handled.
  */
 static bool nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta,
                                 const char *query)
 {
     size_t i;
 
     if (!nbd_strshift(&query, "qemu:")) {
         return false;
     }
     trace_nbd_negotiate_meta_query_parse("qemu:");
 
     if (!*query) {
         if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
             meta->allocation_depth = meta->exp->allocation_depth;
             if (meta->exp->nr_export_bitmaps) {
                 memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
             }
         }
         trace_nbd_negotiate_meta_query_parse("empty");
         return true;
     }
 
     if (strcmp(query, "allocation-depth") == 0) {
         trace_nbd_negotiate_meta_query_parse("allocation-depth");
         meta->allocation_depth = meta->exp->allocation_depth;
         return true;
     }
 
     if (nbd_strshift(&query, "dirty-bitmap:")) {
         trace_nbd_negotiate_meta_query_parse("dirty-bitmap:");
         if (!*query) {
             if (client->opt == NBD_OPT_LIST_META_CONTEXT &&
                 meta->exp->nr_export_bitmaps) {
                 memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
             }
             trace_nbd_negotiate_meta_query_parse("empty");
             return true;
         }
 
         for (i = 0; i < meta->exp->nr_export_bitmaps; i++) {
             const char *bm_name;
 
             bm_name = bdrv_dirty_bitmap_name(meta->exp->export_bitmaps[i]);
             if (strcmp(bm_name, query) == 0) {
                 meta->bitmaps[i] = true;
                 trace_nbd_negotiate_meta_query_parse(query);
                 return true;
             }
         }
         trace_nbd_negotiate_meta_query_skip("no dirty-bitmap match");
         return true;
     }
 
     trace_nbd_negotiate_meta_query_skip("unknown qemu context");
     return true;
 }
 
 /* nbd_negotiate_meta_query
  *
  * Parse namespace name and call corresponding function to parse body of the
  * query.
  *
  * The only supported namespaces are 'base' and 'qemu'.
  *
  * Return -errno on I/O error, 0 if option was completely handled by
  * sending a reply about inconsistent lengths, or 1 on success. */
 static int nbd_negotiate_meta_query(NBDClient *client,
                                     NBDExportMetaContexts *meta, Error **errp)
 {
     int ret;
     g_autofree char *query = NULL;
     uint32_t len;
 
     ret = nbd_opt_read(client, &len, sizeof(len), false, errp);
     if (ret <= 0) {
         return ret;
     }
     len = cpu_to_be32(len);
 
     if (len > NBD_MAX_STRING_SIZE) {
         trace_nbd_negotiate_meta_query_skip("length too long");
         return nbd_opt_skip(client, len, errp);
     }
 
     query = g_malloc(len + 1);
     ret = nbd_opt_read(client, query, len, true, errp);
     if (ret <= 0) {
         return ret;
     }
     query[len] = '\0';
 
     if (nbd_meta_base_query(client, meta, query)) {
         return 1;
     }
     if (nbd_meta_qemu_query(client, meta, query)) {
         return 1;
     }
 
     trace_nbd_negotiate_meta_query_skip("unknown namespace");
     return 1;
 }
 
 /* nbd_negotiate_meta_queries
  * Handle NBD_OPT_LIST_META_CONTEXT and NBD_OPT_SET_META_CONTEXT
  *
  * Return -errno on I/O error, or 0 if option was completely handled. */
 static int nbd_negotiate_meta_queries(NBDClient *client,
                                       NBDExportMetaContexts *meta, Error **errp)
 {
     int ret;
     g_autofree char *export_name = NULL;
     /* Mark unused to work around https://bugs.llvm.org/show_bug.cgi?id=3888 */
     g_autofree G_GNUC_UNUSED bool *bitmaps = NULL;
     NBDExportMetaContexts local_meta = {0};
     uint32_t nb_queries;
     size_t i;
     size_t count = 0;
 
     if (client->opt == NBD_OPT_SET_META_CONTEXT && !client->structured_reply) {
         return nbd_opt_invalid(client, errp,
                                "request option '%s' when structured reply "
                                "is not negotiated",
                                nbd_opt_lookup(client->opt));
     }
 
     if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
         /* Only change the caller's meta on SET. */
         meta = &local_meta;
     }
 
     g_free(meta->bitmaps);
     memset(meta, 0, sizeof(*meta));
 
     ret = nbd_opt_read_name(client, &export_name, NULL, errp);
     if (ret <= 0) {
         return ret;
     }
 
     meta->exp = nbd_export_find(export_name);
     if (meta->exp == NULL) {
         g_autofree char *sane_name = nbd_sanitize_name(export_name);
 
         return nbd_opt_drop(client, NBD_REP_ERR_UNKNOWN, errp,
                             "export '%s' not present", sane_name);
     }
     meta->bitmaps = g_new0(bool, meta->exp->nr_export_bitmaps);
     if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
         bitmaps = meta->bitmaps;
     }
 
     ret = nbd_opt_read(client, &nb_queries, sizeof(nb_queries), false, errp);
     if (ret <= 0) {
         return ret;
     }
     nb_queries = cpu_to_be32(nb_queries);
     trace_nbd_negotiate_meta_context(nbd_opt_lookup(client->opt),
                                      export_name, nb_queries);
 
     if (client->opt == NBD_OPT_LIST_META_CONTEXT && !nb_queries) {
         /* enable all known contexts */
         meta->base_allocation = true;
         meta->allocation_depth = meta->exp->allocation_depth;
         if (meta->exp->nr_export_bitmaps) {
             memset(meta->bitmaps, 1, meta->exp->nr_export_bitmaps);
         }
     } else {
         for (i = 0; i < nb_queries; ++i) {
             ret = nbd_negotiate_meta_query(client, meta, errp);
             if (ret <= 0) {
                 return ret;
             }
         }
     }
 
     if (meta->base_allocation) {
         ret = nbd_negotiate_send_meta_context(client, "base:allocation",
                                               NBD_META_ID_BASE_ALLOCATION,
                                               errp);
         if (ret < 0) {
             return ret;
         }
         count++;
     }
 
     if (meta->allocation_depth) {
         ret = nbd_negotiate_send_meta_context(client, "qemu:allocation-depth",
                                               NBD_META_ID_ALLOCATION_DEPTH,
                                               errp);
         if (ret < 0) {
             return ret;
         }
         count++;
     }
 
     for (i = 0; i < meta->exp->nr_export_bitmaps; i++) {
         const char *bm_name;
         g_autofree char *context = NULL;
 
         if (!meta->bitmaps[i]) {
             continue;
         }
 
         bm_name = bdrv_dirty_bitmap_name(meta->exp->export_bitmaps[i]);
         context = g_strdup_printf("qemu:dirty-bitmap:%s", bm_name);
 
         ret = nbd_negotiate_send_meta_context(client, context,
                                               NBD_META_ID_DIRTY_BITMAP + i,
                                               errp);
         if (ret < 0) {
             return ret;
         }
         count++;
     }
 
     ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
     if (ret == 0) {
         meta->count = count;
     }
 
     return ret;
 }
 
 /* nbd_negotiate_options
  * Process all NBD_OPT_* client option commands, during fixed newstyle
  * negotiation.
  * Return:
  * -errno  on error, errp is set
  * 0       on successful negotiation, errp is not set
  * 1       if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
  *         errp is not set
  */
 static int nbd_negotiate_options(NBDClient *client, Error **errp)
 {
     uint32_t flags;
     bool fixedNewstyle = false;
     bool no_zeroes = false;
 
     /* Client sends:
         [ 0 ..   3]   client flags
 
        Then we loop until NBD_OPT_EXPORT_NAME or NBD_OPT_GO:
         [ 0 ..   7]   NBD_OPTS_MAGIC
         [ 8 ..  11]   NBD option
         [12 ..  15]   Data length
         ...           Rest of request
 
         [ 0 ..   7]   NBD_OPTS_MAGIC
         [ 8 ..  11]   Second NBD option
         [12 ..  15]   Data length
         ...           Rest of request
     */
 
     if (nbd_read32(client->ioc, &flags, "flags", errp) < 0) {
         return -EIO;
     }
     trace_nbd_negotiate_options_flags(flags);
     if (flags & NBD_FLAG_C_FIXED_NEWSTYLE) {
         fixedNewstyle = true;
         flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE;
     }
     if (flags & NBD_FLAG_C_NO_ZEROES) {
         no_zeroes = true;
         flags &= ~NBD_FLAG_C_NO_ZEROES;
     }
     if (flags != 0) {
         error_setg(errp, "Unknown client flags 0x%" PRIx32 " received", flags);
         return -EINVAL;
     }
 
     while (1) {
         int ret;
         uint32_t option, length;
         uint64_t magic;
 
         if (nbd_read64(client->ioc, &magic, "opts magic", errp) < 0) {
             return -EINVAL;
         }
         trace_nbd_negotiate_options_check_magic(magic);
         if (magic != NBD_OPTS_MAGIC) {
             error_setg(errp, "Bad magic received");
             return -EINVAL;
         }
 
         if (nbd_read32(client->ioc, &option, "option", errp) < 0) {
             return -EINVAL;
         }
         client->opt = option;
 
         if (nbd_read32(client->ioc, &length, "option length", errp) < 0) {
             return -EINVAL;
         }
         assert(!client->optlen);
         client->optlen = length;
 
         if (length > NBD_MAX_BUFFER_SIZE) {
             error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",
                        length, NBD_MAX_BUFFER_SIZE);
             return -EINVAL;
         }
 
         trace_nbd_negotiate_options_check_option(option,
                                                  nbd_opt_lookup(option));
         if (client->tlscreds &&
             client->ioc == (QIOChannel *)client->sioc) {
             QIOChannel *tioc;
             if (!fixedNewstyle) {
                 error_setg(errp, "Unsupported option 0x%" PRIx32, option);
                 return -EINVAL;
             }
             switch (option) {
             case NBD_OPT_STARTTLS:
                 if (length) {
                     /* Unconditionally drop the connection if the client
                      * can't start a TLS negotiation correctly */
                     return nbd_reject_length(client, true, errp);
                 }
                 tioc = nbd_negotiate_handle_starttls(client, errp);
                 if (!tioc) {
                     return -EIO;
                 }
                 ret = 0;
                 object_unref(OBJECT(client->ioc));
                 client->ioc = QIO_CHANNEL(tioc);
                 break;
 
             case NBD_OPT_EXPORT_NAME:
                 /* No way to return an error to client, so drop connection */
                 error_setg(errp, "Option 0x%x not permitted before TLS",
                            option);
                 return -EINVAL;
 
             default:
                 /* Let the client keep trying, unless they asked to
                  * quit. Always try to give an error back to the
                  * client; but when replying to OPT_ABORT, be aware
                  * that the client may hang up before receiving the
                  * error, in which case we are fine ignoring the
                  * resulting EPIPE. */
                 ret = nbd_opt_drop(client, NBD_REP_ERR_TLS_REQD,
                                    option == NBD_OPT_ABORT ? NULL : errp,
                                    "Option 0x%" PRIx32
                                    " not permitted before TLS", option);
                 if (option == NBD_OPT_ABORT) {
                     return 1;
                 }
                 break;
             }
         } else if (fixedNewstyle) {
             switch (option) {
             case NBD_OPT_LIST:
                 if (length) {
                     ret = nbd_reject_length(client, false, errp);
                 } else {
                     ret = nbd_negotiate_handle_list(client, errp);
                 }
                 break;
 
             case NBD_OPT_ABORT:
                 /* NBD spec says we must try to reply before
                  * disconnecting, but that we must also tolerate
                  * guests that don't wait for our reply. */
                 nbd_negotiate_send_rep(client, NBD_REP_ACK, NULL);
                 return 1;
 
             case NBD_OPT_EXPORT_NAME:
                 return nbd_negotiate_handle_export_name(client, no_zeroes,
                                                         errp);
 
             case NBD_OPT_INFO:
             case NBD_OPT_GO:
                 ret = nbd_negotiate_handle_info(client, errp);
                 if (ret == 1) {
                     assert(option == NBD_OPT_GO);
                     return 0;
                 }
                 break;
 
             case NBD_OPT_STARTTLS:
                 if (length) {
                     ret = nbd_reject_length(client, false, errp);
                 } else if (client->tlscreds) {
                     ret = nbd_negotiate_send_rep_err(client,
                                                      NBD_REP_ERR_INVALID, errp,
                                                      "TLS already enabled");
                 } else {
                     ret = nbd_negotiate_send_rep_err(client,
                                                      NBD_REP_ERR_POLICY, errp,
                                                      "TLS not configured");
                 }
                 break;
 
             case NBD_OPT_STRUCTURED_REPLY:
                 if (length) {
                     ret = nbd_reject_length(client, false, errp);
                 } else if (client->structured_reply) {
                     ret = nbd_negotiate_send_rep_err(
                         client, NBD_REP_ERR_INVALID, errp,
                         "structured reply already negotiated");
                 } else {
                     ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
                     client->structured_reply = true;
                 }
                 break;
 
             case NBD_OPT_LIST_META_CONTEXT:
             case NBD_OPT_SET_META_CONTEXT:
                 ret = nbd_negotiate_meta_queries(client, &client->export_meta,
                                                  errp);
                 break;
 
             default:
                 ret = nbd_opt_drop(client, NBD_REP_ERR_UNSUP, errp,
                                    "Unsupported option %" PRIu32 " (%s)",
                                    option, nbd_opt_lookup(option));
                 break;
             }
         } else {
             /*
              * If broken new-style we should drop the connection
              * for anything except NBD_OPT_EXPORT_NAME
              */
             switch (option) {
             case NBD_OPT_EXPORT_NAME:
                 return nbd_negotiate_handle_export_name(client, no_zeroes,
                                                         errp);
 
             default:
                 error_setg(errp, "Unsupported option %" PRIu32 " (%s)",
                            option, nbd_opt_lookup(option));
                 return -EINVAL;
             }
         }
         if (ret < 0) {
             return ret;
         }
     }
 }
 
 /* nbd_negotiate
  * Return:
  * -errno  on error, errp is set
  * 0       on successful negotiation, errp is not set
  * 1       if client sent NBD_OPT_ABORT, i.e. on valid disconnect,
  *         errp is not set
  */
 static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
 {
     ERRP_GUARD();
     char buf[NBD_OLDSTYLE_NEGOTIATE_SIZE] = "";
     int ret;
 
     /* Old style negotiation header, no room for options
         [ 0 ..   7]   passwd       ("NBDMAGIC")
         [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
         [16 ..  23]   size
         [24 ..  27]   export flags (zero-extended)
         [28 .. 151]   reserved     (0)
 
        New style negotiation header, client can send options
         [ 0 ..   7]   passwd       ("NBDMAGIC")
         [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
         [16 ..  17]   server flags (0)
         ....options sent, ending in NBD_OPT_EXPORT_NAME or NBD_OPT_GO....
      */
 
     qio_channel_set_blocking(client->ioc, false, NULL);
 
     trace_nbd_negotiate_begin();
     memcpy(buf, "NBDMAGIC", 8);
 
     stq_be_p(buf + 8, NBD_OPTS_MAGIC);
     stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES);
 
     if (nbd_write(client->ioc, buf, 18, errp) < 0) {
         error_prepend(errp, "write failed: ");
         return -EINVAL;
     }
     ret = nbd_negotiate_options(client, errp);
     if (ret != 0) {
         if (ret < 0) {
             error_prepend(errp, "option negotiation failed: ");
         }
         return ret;
     }
 
     /* Attach the channel to the same AioContext as the export */
     if (client->exp && client->exp->common.ctx) {
         qio_channel_attach_aio_context(client->ioc, client->exp->common.ctx);
     }
 
     assert(!client->optlen);
     trace_nbd_negotiate_success();
 
     return 0;
 }
 
 /* nbd_read_eof
  * Tries to read @size bytes from @ioc. This is a local implementation of
  * qio_channel_readv_all_eof. We have it here because we need it to be
  * interruptible and to know when the coroutine is yielding.
  * Returns 1 on success
  *         0 on eof, when no data was read (errp is not set)
  *         negative errno on failure (errp is set)
  */
 static inline int coroutine_fn
 nbd_read_eof(NBDClient *client, void *buffer, size_t size, Error **errp)
 {
     bool partial = false;
 
     assert(size);
     while (size > 0) {
         struct iovec iov = { .iov_base = buffer, .iov_len = size };
         ssize_t len;
 
         len = qio_channel_readv(client->ioc, &iov, 1, errp);
         if (len == QIO_CHANNEL_ERR_BLOCK) {
             client->read_yielding = true;
             qio_channel_yield(client->ioc, G_IO_IN);
             client->read_yielding = false;
             if (client->quiescing) {
                 return -EAGAIN;
             }
             continue;
         } else if (len < 0) {
             return -EIO;
         } else if (len == 0) {
             if (partial) {
                 error_setg(errp,
                            "Unexpected end-of-file before all bytes were read");
                 return -EIO;
             } else {
                 return 0;
             }
         }
 
         partial = true;
         size -= len;
         buffer = (uint8_t *) buffer + len;
     }
     return 1;
 }
 
 static int nbd_receive_request(NBDClient *client, NBDRequest *request,
                                Error **errp)
 {
     uint8_t buf[NBD_REQUEST_SIZE];
     uint32_t magic;
     int ret;
 
     ret = nbd_read_eof(client, buf, sizeof(buf), errp);
     if (ret < 0) {
         return ret;
     }
     if (ret == 0) {
         return -EIO;
     }
 
     /* Request
        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
        [ 4 ..  5]   flags   (NBD_CMD_FLAG_FUA, ...)
        [ 6 ..  7]   type    (NBD_CMD_READ, ...)
        [ 8 .. 15]   handle
        [16 .. 23]   from
        [24 .. 27]   len
      */
 
     magic = ldl_be_p(buf);
     request->flags  = lduw_be_p(buf + 4);
     request->type   = lduw_be_p(buf + 6);
     request->handle = ldq_be_p(buf + 8);
     request->from   = ldq_be_p(buf + 16);
     request->len    = ldl_be_p(buf + 24);
 
     trace_nbd_receive_request(magic, request->flags, request->type,
                               request->from, request->len);
 
     if (magic != NBD_REQUEST_MAGIC) {
         error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
         return -EINVAL;
     }
     return 0;
 }
 
 #define MAX_NBD_REQUESTS 16
 
 void nbd_client_get(NBDClient *client)
 {
     client->refcount++;
 }
 
 void nbd_client_put(NBDClient *client)
 {
     if (--client->refcount == 0) {
         /* The last reference should be dropped by client->close,
          * which is called by client_close.
          */
         assert(client->closing);
 
         qio_channel_detach_aio_context(client->ioc);
         object_unref(OBJECT(client->sioc));
         object_unref(OBJECT(client->ioc));
         if (client->tlscreds) {
             object_unref(OBJECT(client->tlscreds));
         }
         g_free(client->tlsauthz);
         if (client->exp) {
             QTAILQ_REMOVE(&client->exp->clients, client, next);
             blk_exp_unref(&client->exp->common);
         }
         g_free(client->export_meta.bitmaps);
         g_free(client);
     }
 }
 
 static void client_close(NBDClient *client, bool negotiated)
 {
     if (client->closing) {
         return;
     }
 
     client->closing = true;
 
     /* Force requests to finish.  They will drop their own references,
      * then we'll close the socket and free the NBDClient.
      */
     qio_channel_shutdown(client->ioc, QIO_CHANNEL_SHUTDOWN_BOTH,
                          NULL);
 
     /* Also tell the client, so that they release their reference.  */
     if (client->close_fn) {
         client->close_fn(client, negotiated);
     }
 }
 
 static NBDRequestData *nbd_request_get(NBDClient *client)
 {
     NBDRequestData *req;
 
     assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
     client->nb_requests++;
 
     req = g_new0(NBDRequestData, 1);
     nbd_client_get(client);
     req->client = client;
     return req;
 }
 
 static void nbd_request_put(NBDRequestData *req)
 {
     NBDClient *client = req->client;
 
     if (req->data) {
         qemu_vfree(req->data);
     }
     g_free(req);
 
     client->nb_requests--;
 
     if (client->quiescing && client->nb_requests == 0) {
         aio_wait_kick();
     }
 
     nbd_client_receive_next_request(client);
 
     nbd_client_put(client);
 }
 
 static void blk_aio_attached(AioContext *ctx, void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
 
     trace_nbd_blk_aio_attached(exp->name, ctx);
 
     exp->common.ctx = ctx;
 
     QTAILQ_FOREACH(client, &exp->clients, next) {
         qio_channel_attach_aio_context(client->ioc, ctx);
 
         assert(client->nb_requests == 0);
         assert(client->recv_coroutine == NULL);
         assert(client->send_coroutine == NULL);
     }
 }
 
 static void blk_aio_detach(void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
 
     trace_nbd_blk_aio_detach(exp->name, exp->common.ctx);
 
     QTAILQ_FOREACH(client, &exp->clients, next) {
         qio_channel_detach_aio_context(client->ioc);
     }
 
     exp->common.ctx = NULL;
 }
 
 static void nbd_drained_begin(void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
 
     QTAILQ_FOREACH(client, &exp->clients, next) {
         client->quiescing = true;
     }
 }
 
 static void nbd_drained_end(void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
 
     QTAILQ_FOREACH(client, &exp->clients, next) {
         client->quiescing = false;
         nbd_client_receive_next_request(client);
     }
 }
 
 static bool nbd_drained_poll(void *opaque)
 {
     NBDExport *exp = opaque;
     NBDClient *client;
 
     QTAILQ_FOREACH(client, &exp->clients, next) {
         if (client->nb_requests != 0) {
             /*
              * If there's a coroutine waiting for a request on nbd_read_eof()
              * enter it here so we don't depend on the client to wake it up.
              */
             if (client->recv_coroutine != NULL && client->read_yielding) {
                 qemu_aio_coroutine_enter(exp->common.ctx,
                                          client->recv_coroutine);
             }
 
             return true;
         }
     }
 
     return false;
 }
 
 static void nbd_eject_notifier(Notifier *n, void *data)
 {
     NBDExport *exp = container_of(n, NBDExport, eject_notifier);
 
     blk_exp_request_shutdown(&exp->common);
 }
 
 void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk)
 {
     NBDExport *nbd_exp = container_of(exp, NBDExport, common);
     assert(exp->drv == &blk_exp_nbd);
     assert(nbd_exp->eject_notifier_blk == NULL);
 
     blk_ref(blk);
     nbd_exp->eject_notifier_blk = blk;
     nbd_exp->eject_notifier.notify = nbd_eject_notifier;
     blk_add_remove_bs_notifier(blk, &nbd_exp->eject_notifier);
 }
 
 static const BlockDevOps nbd_block_ops = {
     .drained_begin = nbd_drained_begin,
     .drained_end = nbd_drained_end,
     .drained_poll = nbd_drained_poll,
 };
 
 static int nbd_export_create(BlockExport *blk_exp, BlockExportOptions *exp_args,
                              Error **errp)
 {
     NBDExport *exp = container_of(blk_exp, NBDExport, common);
     BlockExportOptionsNbd *arg = &exp_args->u.nbd;
     BlockBackend *blk = blk_exp->blk;
     int64_t size;
     uint64_t perm, shared_perm;
     bool readonly = !exp_args->writable;
     BlockDirtyBitmapOrStrList *bitmaps;
     size_t i;
     int ret;
 
     assert(exp_args->type == BLOCK_EXPORT_TYPE_NBD);
 
     if (!nbd_server_is_running()) {
         error_setg(errp, "NBD server not running");
         return -EINVAL;
     }
 
     if (!arg->has_name) {
         arg->name = exp_args->node_name;
     }
 
     if (strlen(arg->name) > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "export name '%s' too long", arg->name);
         return -EINVAL;
     }
 
     if (arg->description && strlen(arg->description) > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "description '%s' too long", arg->description);
         return -EINVAL;
     }
 
     if (nbd_export_find(arg->name)) {
         error_setg(errp, "NBD server already has export named '%s'", arg->name);
         return -EEXIST;
     }
 
     size = blk_getlength(blk);
     if (size < 0) {
         error_setg_errno(errp, -size,
                          "Failed to determine the NBD export's length");
         return size;
     }
 
     /* Don't allow resize while the NBD server is running, otherwise we don't
      * care what happens with the node. */
     blk_get_perm(blk, &perm, &shared_perm);
     ret = blk_set_perm(blk, perm, shared_perm & ~BLK_PERM_RESIZE, errp);
     if (ret < 0) {
         return ret;
     }
 
     QTAILQ_INIT(&exp->clients);
     exp->name = g_strdup(arg->name);
     exp->description = g_strdup(arg->description);
     exp->nbdflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH |
                      NBD_FLAG_SEND_FUA | NBD_FLAG_SEND_CACHE);
 
     if (nbd_server_max_connections() != 1) {
         exp->nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
     }
     if (readonly) {
         exp->nbdflags |= NBD_FLAG_READ_ONLY;
     } else {
         exp->nbdflags |= (NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_WRITE_ZEROES |
                           NBD_FLAG_SEND_FAST_ZERO);
     }
     exp->size = QEMU_ALIGN_DOWN(size, BDRV_SECTOR_SIZE);
 
     for (bitmaps = arg->bitmaps; bitmaps; bitmaps = bitmaps->next) {
         exp->nr_export_bitmaps++;
     }
     exp->export_bitmaps = g_new0(BdrvDirtyBitmap *, exp->nr_export_bitmaps);
     for (i = 0, bitmaps = arg->bitmaps; bitmaps;
          i++, bitmaps = bitmaps->next)
     {
         const char *bitmap;
         BlockDriverState *bs = blk_bs(blk);
         BdrvDirtyBitmap *bm = NULL;
 
         switch (bitmaps->value->type) {
         case QTYPE_QSTRING:
             bitmap = bitmaps->value->u.local;
             while (bs) {
                 bm = bdrv_find_dirty_bitmap(bs, bitmap);
                 if (bm != NULL) {
                     break;
                 }
 
                 bs = bdrv_filter_or_cow_bs(bs);
             }
 
             if (bm == NULL) {
                 ret = -ENOENT;
                 error_setg(errp, "Bitmap '%s' is not found",
                            bitmaps->value->u.local);
                 goto fail;
             }
 
             if (readonly && bdrv_is_writable(bs) &&
                 bdrv_dirty_bitmap_enabled(bm)) {
                 ret = -EINVAL;
                 error_setg(errp, "Enabled bitmap '%s' incompatible with "
                            "readonly export", bitmap);
                 goto fail;
             }
             break;
         case QTYPE_QDICT:
             bitmap = bitmaps->value->u.external.name;
             bm = block_dirty_bitmap_lookup(bitmaps->value->u.external.node,
                                            bitmap, NULL, errp);
             if (!bm) {
                 ret = -ENOENT;
                 goto fail;
             }
             break;
         default:
             abort();
         }
 
         assert(bm);
 
         if (bdrv_dirty_bitmap_check(bm, BDRV_BITMAP_ALLOW_RO, errp)) {
             ret = -EINVAL;
             goto fail;
         }
 
         exp->export_bitmaps[i] = bm;
         assert(strlen(bitmap) <= BDRV_BITMAP_MAX_NAME_SIZE);
     }
 
     /* Mark bitmaps busy in a separate loop, to simplify roll-back concerns. */
     for (i = 0; i < exp->nr_export_bitmaps; i++) {
         bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], true);
     }
 
     exp->allocation_depth = arg->allocation_depth;
 
     /*
      * We need to inhibit request queuing in the block layer to ensure we can
      * be properly quiesced when entering a drained section, as our coroutines
      * servicing pending requests might enter blk_pread().
      */
     blk_set_disable_request_queuing(blk, true);
 
     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 
     blk_set_dev_ops(blk, &nbd_block_ops, exp);
 
     QTAILQ_INSERT_TAIL(&exports, exp, next);
 
     return 0;
 
 fail:
     g_free(exp->export_bitmaps);
     g_free(exp->name);
     g_free(exp->description);
     return ret;
 }
 
 NBDExport *nbd_export_find(const char *name)
 {
     NBDExport *exp;
     QTAILQ_FOREACH(exp, &exports, next) {
         if (strcmp(name, exp->name) == 0) {
             return exp;
         }
     }
 
     return NULL;
 }
 
 AioContext *
 nbd_export_aio_context(NBDExport *exp)
 {
     return exp->common.ctx;
 }
 
 static void nbd_export_request_shutdown(BlockExport *blk_exp)
 {
     NBDExport *exp = container_of(blk_exp, NBDExport, common);
     NBDClient *client, *next;
 
     blk_exp_ref(&exp->common);
     /*
      * TODO: Should we expand QMP NbdServerRemoveNode enum to allow a
      * close mode that stops advertising the export to new clients but
      * still permits existing clients to run to completion? Because of
      * that possibility, nbd_export_close() can be called more than
      * once on an export.
      */
     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
         client_close(client, true);
     }
     if (exp->name) {
         g_free(exp->name);
         exp->name = NULL;
         QTAILQ_REMOVE(&exports, exp, next);
     }
     blk_exp_unref(&exp->common);
 }
 
 static void nbd_export_delete(BlockExport *blk_exp)
 {
     size_t i;
     NBDExport *exp = container_of(blk_exp, NBDExport, common);
 
     assert(exp->name == NULL);
     assert(QTAILQ_EMPTY(&exp->clients));
 
     g_free(exp->description);
     exp->description = NULL;
 
     if (exp->common.blk) {
         if (exp->eject_notifier_blk) {
             notifier_remove(&exp->eject_notifier);
             blk_unref(exp->eject_notifier_blk);
         }
         blk_remove_aio_context_notifier(exp->common.blk, blk_aio_attached,
                                         blk_aio_detach, exp);
         blk_set_disable_request_queuing(exp->common.blk, false);
     }
 
     for (i = 0; i < exp->nr_export_bitmaps; i++) {
         bdrv_dirty_bitmap_set_busy(exp->export_bitmaps[i], false);
     }
 }
 
 const BlockExportDriver blk_exp_nbd = {
     .type               = BLOCK_EXPORT_TYPE_NBD,
     .instance_size      = sizeof(NBDExport),
     .create             = nbd_export_create,
     .delete             = nbd_export_delete,
     .request_shutdown   = nbd_export_request_shutdown,
 };
 
 static int coroutine_fn nbd_co_send_iov(NBDClient *client, struct iovec *iov,
                                         unsigned niov, Error **errp)
 {
     int ret;
 
     g_assert(qemu_in_coroutine());
     qemu_co_mutex_lock(&client->send_lock);
     client->send_coroutine = qemu_coroutine_self();
 
     ret = qio_channel_writev_all(client->ioc, iov, niov, errp) < 0 ? -EIO : 0;
 
     client->send_coroutine = NULL;
     qemu_co_mutex_unlock(&client->send_lock);
 
     return ret;
 }
 
 static inline void set_be_simple_reply(NBDSimpleReply *reply, uint64_t error,
                                        uint64_t handle)
 {
     stl_be_p(&reply->magic, NBD_SIMPLE_REPLY_MAGIC);
     stl_be_p(&reply->error, error);
     stq_be_p(&reply->handle, handle);
 }
 
 static int nbd_co_send_simple_reply(NBDClient *client,
                                     uint64_t handle,
                                     uint32_t error,
                                     void *data,
                                     size_t len,
                                     Error **errp)
 {
     NBDSimpleReply reply;
     int nbd_err = system_errno_to_nbd_errno(error);
     struct iovec iov[] = {
         {.iov_base = &reply, .iov_len = sizeof(reply)},
         {.iov_base = data, .iov_len = len}
     };
 
     trace_nbd_co_send_simple_reply(handle, nbd_err, nbd_err_lookup(nbd_err),
                                    len);
     set_be_simple_reply(&reply, nbd_err, handle);
 
     return nbd_co_send_iov(client, iov, len ? 2 : 1, errp);
 }
 
 static inline void set_be_chunk(NBDStructuredReplyChunk *chunk, uint16_t flags,
                                 uint16_t type, uint64_t handle, uint32_t length)
 {
     stl_be_p(&chunk->magic, NBD_STRUCTURED_REPLY_MAGIC);
     stw_be_p(&chunk->flags, flags);
     stw_be_p(&chunk->type, type);
     stq_be_p(&chunk->handle, handle);
     stl_be_p(&chunk->length, length);
 }
 
 static int coroutine_fn nbd_co_send_structured_done(NBDClient *client,
                                                     uint64_t handle,
                                                     Error **errp)
 {
     NBDStructuredReplyChunk chunk;
     struct iovec iov[] = {
         {.iov_base = &chunk, .iov_len = sizeof(chunk)},
     };
 
     trace_nbd_co_send_structured_done(handle);
     set_be_chunk(&chunk, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_NONE, handle, 0);
 
     return nbd_co_send_iov(client, iov, 1, errp);
 }
 
 static int coroutine_fn nbd_co_send_structured_read(NBDClient *client,
                                                     uint64_t handle,
                                                     uint64_t offset,
                                                     void *data,
                                                     size_t size,
                                                     bool final,
                                                     Error **errp)
 {
     NBDStructuredReadData chunk;
     struct iovec iov[] = {
         {.iov_base = &chunk, .iov_len = sizeof(chunk)},
         {.iov_base = data, .iov_len = size}
     };
 
     assert(size);
     trace_nbd_co_send_structured_read(handle, offset, data, size);
     set_be_chunk(&chunk.h, final ? NBD_REPLY_FLAG_DONE : 0,
                  NBD_REPLY_TYPE_OFFSET_DATA, handle,
                  sizeof(chunk) - sizeof(chunk.h) + size);
     stq_be_p(&chunk.offset, offset);
 
     return nbd_co_send_iov(client, iov, 2, errp);
 }
 
 static int coroutine_fn nbd_co_send_structured_error(NBDClient *client,
                                                      uint64_t handle,
                                                      uint32_t error,
                                                      const char *msg,
                                                      Error **errp)
 {
     NBDStructuredError chunk;
     int nbd_err = system_errno_to_nbd_errno(error);
     struct iovec iov[] = {
         {.iov_base = &chunk, .iov_len = sizeof(chunk)},
         {.iov_base = (char *)msg, .iov_len = msg ? strlen(msg) : 0},
     };
 
     assert(nbd_err);
     trace_nbd_co_send_structured_error(handle, nbd_err,
                                        nbd_err_lookup(nbd_err), msg ? msg : "");
     set_be_chunk(&chunk.h, NBD_REPLY_FLAG_DONE, NBD_REPLY_TYPE_ERROR, handle,
                  sizeof(chunk) - sizeof(chunk.h) + iov[1].iov_len);
     stl_be_p(&chunk.error, nbd_err);
     stw_be_p(&chunk.message_length, iov[1].iov_len);
 
     return nbd_co_send_iov(client, iov, 1 + !!iov[1].iov_len, errp);
 }
 
 /* Do a sparse read and send the structured reply to the client.
  * Returns -errno if sending fails. bdrv_block_status_above() failure is
  * reported to the client, at which point this function succeeds.
  */
 static int coroutine_fn nbd_co_send_sparse_read(NBDClient *client,
                                                 uint64_t handle,
                                                 uint64_t offset,
                                                 uint8_t *data,
                                                 size_t size,
                                                 Error **errp)
 {
     int ret = 0;
     NBDExport *exp = client->exp;
     size_t progress = 0;
 
     while (progress < size) {
         int64_t pnum;
         int status = bdrv_block_status_above(blk_bs(exp->common.blk), NULL,
                                              offset + progress,
                                              size - progress, &pnum, NULL,
                                              NULL);
         bool final;
 
         if (status < 0) {
             char *msg = g_strdup_printf("unable to check for holes: %s",
                                         strerror(-status));
 
             ret = nbd_co_send_structured_error(client, handle, -status, msg,
                                                errp);
             g_free(msg);
             return ret;
         }
         assert(pnum && pnum <= size - progress);
         final = progress + pnum == size;
         if (status & BDRV_BLOCK_ZERO) {
             NBDStructuredReadHole chunk;
             struct iovec iov[] = {
                 {.iov_base = &chunk, .iov_len = sizeof(chunk)},
             };
 
             trace_nbd_co_send_structured_read_hole(handle, offset + progress,
                                                    pnum);
             set_be_chunk(&chunk.h, final ? NBD_REPLY_FLAG_DONE : 0,
                          NBD_REPLY_TYPE_OFFSET_HOLE,
                          handle, sizeof(chunk) - sizeof(chunk.h));
             stq_be_p(&chunk.offset, offset + progress);
             stl_be_p(&chunk.length, pnum);
             ret = nbd_co_send_iov(client, iov, 1, errp);
         } else {
             ret = blk_pread(exp->common.blk, offset + progress, pnum,
                             data + progress, 0);
             if (ret < 0) {
                 error_setg_errno(errp, -ret, "reading from file failed");
                 break;
             }
             ret = nbd_co_send_structured_read(client, handle, offset + progress,
                                               data + progress, pnum, final,
                                               errp);
         }
 
         if (ret < 0) {
             break;
         }
         progress += pnum;
     }
     return ret;
 }
 
 typedef struct NBDExtentArray {
     NBDExtent *extents;
     unsigned int nb_alloc;
     unsigned int count;
     uint64_t total_length;
     bool can_add;
     bool converted_to_be;
 } NBDExtentArray;
 
 static NBDExtentArray *nbd_extent_array_new(unsigned int nb_alloc)
 {
     NBDExtentArray *ea = g_new0(NBDExtentArray, 1);
 
     ea->nb_alloc = nb_alloc;
     ea->extents = g_new(NBDExtent, nb_alloc);
     ea->can_add = true;
 
     return ea;
 }
 
 static void nbd_extent_array_free(NBDExtentArray *ea)
 {
     g_free(ea->extents);
     g_free(ea);
 }
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(NBDExtentArray, nbd_extent_array_free)
 
 /* Further modifications of the array after conversion are abandoned */
 static void nbd_extent_array_convert_to_be(NBDExtentArray *ea)
 {
     int i;
 
     assert(!ea->converted_to_be);
     ea->can_add = false;
     ea->converted_to_be = true;
 
     for (i = 0; i < ea->count; i++) {
         ea->extents[i].flags = cpu_to_be32(ea->extents[i].flags);
         ea->extents[i].length = cpu_to_be32(ea->extents[i].length);
     }
 }
 
 /*
  * Add extent to NBDExtentArray. If extent can't be added (no available space),
  * return -1.
  * For safety, when returning -1 for the first time, .can_add is set to false,
  * and further calls to nbd_extent_array_add() will crash.
  * (this avoids the situation where a caller ignores failure to add one extent,
  * where adding another extent that would squash into the last array entry
  * would result in an incorrect range reported to the client)
  */
 static int nbd_extent_array_add(NBDExtentArray *ea,
                                 uint32_t length, uint32_t flags)
 {
     assert(ea->can_add);
 
     if (!length) {
         return 0;
     }
 
     /* Extend previous extent if flags are the same */
     if (ea->count > 0 && flags == ea->extents[ea->count - 1].flags) {
         uint64_t sum = (uint64_t)length + ea->extents[ea->count - 1].length;
 
         if (sum <= UINT32_MAX) {
             ea->extents[ea->count - 1].length = sum;
             ea->total_length += length;
             return 0;
         }
     }
 
     if (ea->count >= ea->nb_alloc) {
         ea->can_add = false;
         return -1;
     }
 
     ea->total_length += length;
     ea->extents[ea->count] = (NBDExtent) {.length = length, .flags = flags};
     ea->count++;
 
     return 0;
 }
 
 static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
                                   uint64_t bytes, NBDExtentArray *ea)
 {
     while (bytes) {
         uint32_t flags;
         int64_t num;
         int ret = bdrv_block_status_above(bs, NULL, offset, bytes, &num,
                                           NULL, NULL);
 
         if (ret < 0) {
             return ret;
         }
 
         flags = (ret & BDRV_BLOCK_DATA ? 0 : NBD_STATE_HOLE) |
                 (ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0);
 
         if (nbd_extent_array_add(ea, num, flags) < 0) {
             return 0;
         }
 
         offset += num;
         bytes -= num;
     }
 
     return 0;
 }
 
 static int blockalloc_to_extents(BlockDriverState *bs, uint64_t offset,
                                  uint64_t bytes, NBDExtentArray *ea)
 {
     while (bytes) {
         int64_t num;
         int ret = bdrv_is_allocated_above(bs, NULL, false, offset, bytes,
                                           &num);
 
         if (ret < 0) {
             return ret;
         }
 
         if (nbd_extent_array_add(ea, num, ret) < 0) {
             return 0;
         }
 
         offset += num;
         bytes -= num;
     }
 
     return 0;
 }
 
 /*
  * nbd_co_send_extents
  *
  * @ea is converted to BE by the function
  * @last controls whether NBD_REPLY_FLAG_DONE is sent.
  */
 static int nbd_co_send_extents(NBDClient *client, uint64_t handle,
                                NBDExtentArray *ea,
                                bool last, uint32_t context_id, Error **errp)
 {
     NBDStructuredMeta chunk;
     struct iovec iov[] = {
         {.iov_base = &chunk, .iov_len = sizeof(chunk)},
         {.iov_base = ea->extents, .iov_len = ea->count * sizeof(ea->extents[0])}
     };
 
     nbd_extent_array_convert_to_be(ea);
 
     trace_nbd_co_send_extents(handle, ea->count, context_id, ea->total_length,
                               last);
     set_be_chunk(&chunk.h, last ? NBD_REPLY_FLAG_DONE : 0,
                  NBD_REPLY_TYPE_BLOCK_STATUS,
                  handle, sizeof(chunk) - sizeof(chunk.h) + iov[1].iov_len);
     stl_be_p(&chunk.context_id, context_id);
 
     return nbd_co_send_iov(client, iov, 2, errp);
 }
 
 /* Get block status from the exported device and send it to the client */
 static int nbd_co_send_block_status(NBDClient *client, uint64_t handle,
                                     BlockDriverState *bs, uint64_t offset,
                                     uint32_t length, bool dont_fragment,
                                     bool last, uint32_t context_id,
                                     Error **errp)
 {
     int ret;
     unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
     g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
 
     if (context_id == NBD_META_ID_BASE_ALLOCATION) {
         ret = blockstatus_to_extents(bs, offset, length, ea);
     } else {
         ret = blockalloc_to_extents(bs, offset, length, ea);
     }
     if (ret < 0) {
         return nbd_co_send_structured_error(
                 client, handle, -ret, "can't get block status", errp);
     }
 
     return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
 }
 
 /* Populate @ea from a dirty bitmap. */
 static void bitmap_to_extents(BdrvDirtyBitmap *bitmap,
                               uint64_t offset, uint64_t length,
                               NBDExtentArray *es)
 {
     int64_t start, dirty_start, dirty_count;
     int64_t end = offset + length;
     bool full = false;
 
     bdrv_dirty_bitmap_lock(bitmap);
 
     for (start = offset;
          bdrv_dirty_bitmap_next_dirty_area(bitmap, start, end, INT32_MAX,
                                            &dirty_start, &dirty_count);
          start = dirty_start + dirty_count)
     {
         if ((nbd_extent_array_add(es, dirty_start - start, 0) < 0) ||
             (nbd_extent_array_add(es, dirty_count, NBD_STATE_DIRTY) < 0))
         {
             full = true;
             break;
         }
     }
 
     if (!full) {
         /* last non dirty extent, nothing to do if array is now full */
         (void) nbd_extent_array_add(es, end - start, 0);
     }
 
     bdrv_dirty_bitmap_unlock(bitmap);
 }
 
 static int nbd_co_send_bitmap(NBDClient *client, uint64_t handle,
                               BdrvDirtyBitmap *bitmap, uint64_t offset,
                               uint32_t length, bool dont_fragment, bool last,
                               uint32_t context_id, Error **errp)
 {
     unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
     g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
 
     bitmap_to_extents(bitmap, offset, length, ea);
 
     return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
 }
 
 /* nbd_co_receive_request
  * Collect a client request. Return 0 if request looks valid, -EIO to drop
  * connection right away, -EAGAIN to indicate we were interrupted and the
  * channel should be quiesced, and any other negative value to report an error
  * to the client (although the caller may still need to disconnect after
  * reporting the error).
  */
 static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,
                                   Error **errp)
 {
     NBDClient *client = req->client;
     int valid_flags;
     int ret;
 
     g_assert(qemu_in_coroutine());
     assert(client->recv_coroutine == qemu_coroutine_self());
     ret = nbd_receive_request(client, request, errp);
     if (ret < 0) {
         return ret;
     }
 
     trace_nbd_co_receive_request_decode_type(request->handle, request->type,
                                              nbd_cmd_lookup(request->type));
 
     if (request->type != NBD_CMD_WRITE) {
         /* No payload, we are ready to read the next request.  */
         req->complete = true;
     }
 
     if (request->type == NBD_CMD_DISC) {
         /* Special case: we're going to disconnect without a reply,
          * whether or not flags, from, or len are bogus */
         return -EIO;
     }
 
     if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE ||
         request->type == NBD_CMD_CACHE)
     {
         if (request->len > NBD_MAX_BUFFER_SIZE) {
             error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",
                        request->len, NBD_MAX_BUFFER_SIZE);
             return -EINVAL;
         }
 
         if (request->type != NBD_CMD_CACHE) {
             req->data = blk_try_blockalign(client->exp->common.blk,
                                            request->len);
             if (req->data == NULL) {
                 error_setg(errp, "No memory");
                 return -ENOMEM;
             }
         }
     }
 
     if (request->type == NBD_CMD_WRITE) {
         if (nbd_read(client->ioc, req->data, request->len, "CMD_WRITE data",
                      errp) < 0)
         {
             return -EIO;
         }
         req->complete = true;
 
         trace_nbd_co_receive_request_payload_received(request->handle,
                                                       request->len);
     }
 
     /* Sanity checks. */
     if (client->exp->nbdflags & NBD_FLAG_READ_ONLY &&
         (request->type == NBD_CMD_WRITE ||
          request->type == NBD_CMD_WRITE_ZEROES ||
          request->type == NBD_CMD_TRIM)) {
         error_setg(errp, "Export is read-only");
         return -EROFS;
     }
     if (request->from > client->exp->size ||
         request->len > client->exp->size - request->from) {
         error_setg(errp, "operation past EOF; From: %" PRIu64 ", Len: %" PRIu32
                    ", Size: %" PRIu64, request->from, request->len,
                    client->exp->size);
         return (request->type == NBD_CMD_WRITE ||
                 request->type == NBD_CMD_WRITE_ZEROES) ? -ENOSPC : -EINVAL;
     }
     if (client->check_align && !QEMU_IS_ALIGNED(request->from | request->len,
                                                 client->check_align)) {
         /*
          * The block layer gracefully handles unaligned requests, but
          * it's still worth tracing client non-compliance
          */
         trace_nbd_co_receive_align_compliance(nbd_cmd_lookup(request->type),
                                               request->from,
                                               request->len,
                                               client->check_align);
     }
     valid_flags = NBD_CMD_FLAG_FUA;
     if (request->type == NBD_CMD_READ && client->structured_reply) {
         valid_flags |= NBD_CMD_FLAG_DF;
     } else if (request->type == NBD_CMD_WRITE_ZEROES) {
         valid_flags |= NBD_CMD_FLAG_NO_HOLE | NBD_CMD_FLAG_FAST_ZERO;
     } else if (request->type == NBD_CMD_BLOCK_STATUS) {
         valid_flags |= NBD_CMD_FLAG_REQ_ONE;
     }
     if (request->flags & ~valid_flags) {
         error_setg(errp, "unsupported flags for command %s (got 0x%x)",
                    nbd_cmd_lookup(request->type), request->flags);
         return -EINVAL;
     }
 
     return 0;
 }
 
 /* Send simple reply without a payload, or a structured error
  * @error_msg is ignored if @ret >= 0
  * Returns 0 if connection is still live, -errno on failure to talk to client
  */
 static coroutine_fn int nbd_send_generic_reply(NBDClient *client,
                                                uint64_t handle,
                                                int ret,
                                                const char *error_msg,
                                                Error **errp)
 {
     if (client->structured_reply && ret < 0) {
         return nbd_co_send_structured_error(client, handle, -ret, error_msg,
                                             errp);
     } else {
         return nbd_co_send_simple_reply(client, handle, ret < 0 ? -ret : 0,
                                         NULL, 0, errp);
     }
 }
 
 /* Handle NBD_CMD_READ request.
  * Return -errno if sending fails. Other errors are reported directly to the
  * client as an error reply. */
 static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,
                                         uint8_t *data, Error **errp)
 {
     int ret;
     NBDExport *exp = client->exp;
 
     assert(request->type == NBD_CMD_READ);
 
     /* XXX: NBD Protocol only documents use of FUA with WRITE */
     if (request->flags & NBD_CMD_FLAG_FUA) {
         ret = blk_co_flush(exp->common.blk);
         if (ret < 0) {
             return nbd_send_generic_reply(client, request->handle, ret,
                                           "flush failed", errp);
         }
     }
 
     if (client->structured_reply && !(request->flags & NBD_CMD_FLAG_DF) &&
         request->len)
     {
         return nbd_co_send_sparse_read(client, request->handle, request->from,
                                        data, request->len, errp);
     }
 
     ret = blk_pread(exp->common.blk, request->from, request->len, data, 0);
     if (ret < 0) {
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "reading from file failed", errp);
     }
 
     if (client->structured_reply) {
         if (request->len) {
             return nbd_co_send_structured_read(client, request->handle,
                                                request->from, data,
                                                request->len, true, errp);
         } else {
             return nbd_co_send_structured_done(client, request->handle, errp);
         }
     } else {
         return nbd_co_send_simple_reply(client, request->handle, 0,
                                         data, request->len, errp);
     }
 }
 
 /*
  * nbd_do_cmd_cache
  *
  * Handle NBD_CMD_CACHE request.
  * Return -errno if sending fails. Other errors are reported directly to the
  * client as an error reply.
  */
 static coroutine_fn int nbd_do_cmd_cache(NBDClient *client, NBDRequest *request,
                                          Error **errp)
 {
     int ret;
     NBDExport *exp = client->exp;
 
     assert(request->type == NBD_CMD_CACHE);
 
     ret = blk_co_preadv(exp->common.blk, request->from, request->len,
                         NULL, BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
 
     return nbd_send_generic_reply(client, request->handle, ret,
                                   "caching data failed", errp);
 }
 
 /* Handle NBD request.
  * Return -errno if sending fails. Other errors are reported directly to the
  * client as an error reply. */
 static coroutine_fn int nbd_handle_request(NBDClient *client,
                                            NBDRequest *request,
                                            uint8_t *data, Error **errp)
 {
     int ret;
     int flags;
     NBDExport *exp = client->exp;
     char *msg;
     size_t i;
 
     switch (request->type) {
     case NBD_CMD_CACHE:
         return nbd_do_cmd_cache(client, request, errp);
 
     case NBD_CMD_READ:
         return nbd_do_cmd_read(client, request, data, errp);
 
     case NBD_CMD_WRITE:
         flags = 0;
         if (request->flags & NBD_CMD_FLAG_FUA) {
             flags |= BDRV_REQ_FUA;
         }
         ret = blk_pwrite(exp->common.blk, request->from, request->len, data,
                          flags);
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "writing to file failed", errp);
 
     case NBD_CMD_WRITE_ZEROES:
         flags = 0;
         if (request->flags & NBD_CMD_FLAG_FUA) {
             flags |= BDRV_REQ_FUA;
         }
         if (!(request->flags & NBD_CMD_FLAG_NO_HOLE)) {
             flags |= BDRV_REQ_MAY_UNMAP;
         }
         if (request->flags & NBD_CMD_FLAG_FAST_ZERO) {
             flags |= BDRV_REQ_NO_FALLBACK;
         }
         ret = blk_pwrite_zeroes(exp->common.blk, request->from, request->len,
                                 flags);
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "writing to file failed", errp);
 
     case NBD_CMD_DISC:
         /* unreachable, thanks to special case in nbd_co_receive_request() */
         abort();
 
     case NBD_CMD_FLUSH:
         ret = blk_co_flush(exp->common.blk);
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "flush failed", errp);
 
     case NBD_CMD_TRIM:
         ret = blk_co_pdiscard(exp->common.blk, request->from, request->len);
         if (ret >= 0 && request->flags & NBD_CMD_FLAG_FUA) {
             ret = blk_co_flush(exp->common.blk);
         }
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "discard failed", errp);
 
     case NBD_CMD_BLOCK_STATUS:
         if (!request->len) {
             return nbd_send_generic_reply(client, request->handle, -EINVAL,
                                           "need non-zero length", errp);
         }
         if (client->export_meta.count) {
             bool dont_fragment = request->flags & NBD_CMD_FLAG_REQ_ONE;
             int contexts_remaining = client->export_meta.count;
 
             if (client->export_meta.base_allocation) {
                 ret = nbd_co_send_block_status(client, request->handle,
                                                blk_bs(exp->common.blk),
                                                request->from,
                                                request->len, dont_fragment,
                                                !--contexts_remaining,
                                                NBD_META_ID_BASE_ALLOCATION,
                                                errp);
                 if (ret < 0) {
                     return ret;
                 }
             }
 
             if (client->export_meta.allocation_depth) {
                 ret = nbd_co_send_block_status(client, request->handle,
                                                blk_bs(exp->common.blk),
                                                request->from, request->len,
                                                dont_fragment,
                                                !--contexts_remaining,
                                                NBD_META_ID_ALLOCATION_DEPTH,
                                                errp);
                 if (ret < 0) {
                     return ret;
                 }
             }
 
             for (i = 0; i < client->exp->nr_export_bitmaps; i++) {
                 if (!client->export_meta.bitmaps[i]) {
                     continue;
                 }
                 ret = nbd_co_send_bitmap(client, request->handle,
                                          client->exp->export_bitmaps[i],
                                          request->from, request->len,
                                          dont_fragment, !--contexts_remaining,
                                          NBD_META_ID_DIRTY_BITMAP + i, errp);
                 if (ret < 0) {
                     return ret;
                 }
             }
 
             assert(!contexts_remaining);
 
             return 0;
         } else {
             return nbd_send_generic_reply(client, request->handle, -EINVAL,
                                           "CMD_BLOCK_STATUS not negotiated",
                                           errp);
         }
 
     default:
         msg = g_strdup_printf("invalid request type (%" PRIu32 ") received",
                               request->type);
         ret = nbd_send_generic_reply(client, request->handle, -EINVAL, msg,
                                      errp);
         g_free(msg);
         return ret;
     }
 }
 
 /* Owns a reference to the NBDClient passed as opaque.  */
 static coroutine_fn void nbd_trip(void *opaque)
 {
     NBDClient *client = opaque;
     NBDRequestData *req;
     NBDRequest request = { 0 };    /* GCC thinks it can be used uninitialized */
     int ret;
     Error *local_err = NULL;
 
     trace_nbd_trip();
     if (client->closing) {
         nbd_client_put(client);
         return;
     }
 
     if (client->quiescing) {
         /*
          * We're switching between AIO contexts. Don't attempt to receive a new
          * request and kick the main context which may be waiting for us.
          */
         nbd_client_put(client);
         client->recv_coroutine = NULL;
         aio_wait_kick();
         return;
     }
 
     req = nbd_request_get(client);
     ret = nbd_co_receive_request(req, &request, &local_err);
     client->recv_coroutine = NULL;
 
     if (client->closing) {
         /*
          * The client may be closed when we are blocked in
          * nbd_co_receive_request()
          */
         goto done;
     }
 
     if (ret == -EAGAIN) {
         assert(client->quiescing);
         goto done;
     }
 
     nbd_client_receive_next_request(client);
     if (ret == -EIO) {
         goto disconnect;
     }
 
     if (ret < 0) {
         /* It wasn't -EIO, so, according to nbd_co_receive_request()
          * semantics, we should return the error to the client. */
         Error *export_err = local_err;
 
         local_err = NULL;
         ret = nbd_send_generic_reply(client, request.handle, -EINVAL,
                                      error_get_pretty(export_err), &local_err);
         error_free(export_err);
     } else {
         ret = nbd_handle_request(client, &request, req->data, &local_err);
     }
     if (ret < 0) {
         error_prepend(&local_err, "Failed to send reply: ");
         goto disconnect;
     }
 
     /* We must disconnect after NBD_CMD_WRITE if we did not
      * read the payload.
      */
     if (!req->complete) {
         error_setg(&local_err, "Request handling failed in intermediate state");
         goto disconnect;
     }
 
 done:
     nbd_request_put(req);
     nbd_client_put(client);
     return;
 
 disconnect:
     if (local_err) {
         error_reportf_err(local_err, "Disconnect client, due to: ");
     }
     nbd_request_put(req);
     client_close(client, true);
     nbd_client_put(client);
 }
 
 static void nbd_client_receive_next_request(NBDClient *client)
 {
     if (!client->recv_coroutine && client->nb_requests < MAX_NBD_REQUESTS &&
         !client->quiescing) {
         nbd_client_get(client);
         client->recv_coroutine = qemu_coroutine_create(nbd_trip, client);
         aio_co_schedule(client->exp->common.ctx, client->recv_coroutine);
     }
 }
 
 static coroutine_fn void nbd_co_client_start(void *opaque)
 {
     NBDClient *client = opaque;
     Error *local_err = NULL;
 
     qemu_co_mutex_init(&client->send_lock);
 
     if (nbd_negotiate(client, &local_err)) {
         if (local_err) {
             error_report_err(local_err);
         }
         client_close(client, false);
         return;
     }
 
     nbd_client_receive_next_request(client);
 }
 
 /*
  * Create a new client listener using the given channel @sioc.
  * Begin servicing it in a coroutine.  When the connection closes, call
  * @close_fn with an indication of whether the client completed negotiation.
  */
 void nbd_client_new(QIOChannelSocket *sioc,
                     QCryptoTLSCreds *tlscreds,
                     const char *tlsauthz,
                     void (*close_fn)(NBDClient *, bool))
 {
     NBDClient *client;
     Coroutine *co;
 
     client = g_new0(NBDClient, 1);
     client->refcount = 1;
     client->tlscreds = tlscreds;
     if (tlscreds) {
         object_ref(OBJECT(client->tlscreds));
     }
     client->tlsauthz = g_strdup(tlsauthz);
     client->sioc = sioc;
     object_ref(OBJECT(client->sioc));
     client->ioc = QIO_CHANNEL(sioc);
     object_ref(OBJECT(client->ioc));
     client->close_fn = close_fn;
 
     co = qemu_coroutine_create(nbd_co_client_start, client);
     qemu_coroutine_enter(co);
 }