01.12.2018 1:03, Eric Blake wrote:
> We want to be able to detect whether a given qemu NBD server is
> exposing the right export(s) and dirty bitmaps, at least for
> regression testing. We could use 'nbd-client -l' from the upstream
> NBD project to list exports, but it's annoying to rely on
> out-of-tree binaries; furthermore, nbd-client doesn't necessarily
> know about all of the qemu NBD extensions. Thus, we plan on adding
> a new mode to qemu-nbd that merely sniffs all possible information
> from the server during handshake phase, then disconnects and dumps
> the information.
>
> This patch adds the low-level client code for grabbing the list
> of exports. It benefits from the recent refactoring patches, as
> well as a minor tweak of changing nbd_opt_go() to nbd_opt_info_go(),
> in order to share as much code as possible when it comes to doing
> validation of server replies. The resulting information is stored
> in an array of NBDExportInfo which has been expanded to hold more
> members, along with a convenience function for freeing the list.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
> ---
> include/block/nbd.h | 15 +++-
> nbd/client.c | 166 ++++++++++++++++++++++++++++++++++++++++++--
> nbd/trace-events | 2 +-
> 3 files changed, 174 insertions(+), 9 deletions(-)
>
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 65feff8ba96..74d006b8d62 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -262,6 +262,9 @@ struct NBDExportInfo {
> /* Set by client before nbd_receive_negotiate() */
> bool request_sizes;
> char *x_dirty_bitmap;
> +
> + /* Set by client before nbd_receive_negotiate(), or by server results
> + * during nbd_receive_export_list() */
> char *name; /* must be non-NULL */
>
> /* In-out fields, set by client before nbd_receive_negotiate() and
> @@ -269,7 +272,8 @@ struct NBDExportInfo {
> bool structured_reply;
> bool base_allocation; /* base:allocation context for
> NBD_CMD_BLOCK_STATUS */
>
> - /* Set by server results during nbd_receive_negotiate() */
> + /* Set by server results during nbd_receive_negotiate() and
> + * nbd_receive_export_list() */
> uint64_t size;
> uint16_t flags;
> uint32_t min_block;
> @@ -277,12 +281,21 @@ struct NBDExportInfo {
> uint32_t max_block;
>
> uint32_t meta_base_allocation_id;
> +
> + /* Set by server results during nbd_receive_export_list() */
> + char *description;
> + int n_contexts;
> + char **contexts;
> };
> typedef struct NBDExportInfo NBDExportInfo;
>
> int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
> const char *hostname, QIOChannel **outioc,
> NBDExportInfo *info, Error **errp);
> +void nbd_free_export_list(NBDExportInfo *info, int count);
> +int nbd_receive_export_list(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
> + const char *hostname, NBDExportInfo **info,
> + Error **errp);
> int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
> Error **errp);
> int nbd_send_request(QIOChannel *ioc, NBDRequest *request);
> diff --git a/nbd/client.c b/nbd/client.c
> index a282712724d..6292de560ee 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -351,7 +351,8 @@ static int nbd_receive_list(QIOChannel *ioc, const char
> *want, bool *match,
> * used, 0 if NBD_OPT_GO is unsupported (fall back to NBD_OPT_LIST and
> * NBD_OPT_EXPORT_NAME in that case), and > 0 if the export is good to
> * go (with the rest of @info populated). */
> -static int nbd_opt_go(QIOChannel *ioc, NBDExportInfo *info, Error **errp)
> +static int nbd_opt_info_go(QIOChannel *ioc, uint32_t opt,
> + NBDExportInfo *info, Error **errp)
> {
> NBDOptionReply reply;
> uint32_t len = strlen(info->name);
> @@ -364,7 +365,8 @@ static int nbd_opt_go(QIOChannel *ioc, NBDExportInfo
> *info, Error **errp)
> * flags still 0 is a witness of a broken server. */
> info->flags = 0;
>
> - trace_nbd_opt_go_start(info->name);
> + assert(opt == NBD_OPT_GO || opt == NBD_OPT_INFO);
> + trace_nbd_opt_go_start(nbd_opt_lookup(opt), info->name);
> buf = g_malloc(4 + len + 2 + 2 * info->request_sizes + 1);
> stl_be_p(buf, len);
> memcpy(buf + 4, info->name, len);
> @@ -373,7 +375,7 @@ static int nbd_opt_go(QIOChannel *ioc, NBDExportInfo
> *info, Error **errp)
> if (info->request_sizes) {
> stw_be_p(buf + 4 + len + 2, NBD_INFO_BLOCK_SIZE);
> }
> - error = nbd_send_option_request(ioc, NBD_OPT_GO,
> + error = nbd_send_option_request(ioc, opt,
> 4 + len + 2 + 2 * info->request_sizes,
> buf, errp);
> g_free(buf);
> @@ -382,7 +384,7 @@ static int nbd_opt_go(QIOChannel *ioc, NBDExportInfo
> *info, Error **errp)
> }
>
> while (1) {
> - if (nbd_receive_option_reply(ioc, NBD_OPT_GO, &reply, errp) < 0) {
> + if (nbd_receive_option_reply(ioc, opt, &reply, errp) < 0) {
> return -1;
> }
> error = nbd_handle_reply_err(ioc, &reply, errp);
> @@ -733,8 +735,12 @@ static int nbd_negotiate_simple_meta_context(QIOChannel
> *ioc,
> nbd_send_opt_abort(ioc);
> return -1;
> }
> + g_free(name);
> + } else {
> + info->contexts = g_renew(char *, info->contexts,
> + ++info->n_contexts);
> + info->contexts[info->n_contexts - 1] = name;
> }
> - g_free(name);
> received = true;
>
> /* receive NBD_REP_ACK */
> @@ -828,7 +834,9 @@ static int nbd_start_negotiate(QIOChannel *ioc,
> QCryptoTLSCreds *tlscreds,
> clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
> }
> if (globalflags & NBD_FLAG_NO_ZEROES) {
> - *zeroes = false;
> + if (zeroes) {
> + *zeroes = false;
> + }
> clientflags |= NBD_FLAG_C_NO_ZEROES;
> }
> /* client requested flags */
> @@ -921,7 +929,7 @@ int nbd_receive_negotiate(QIOChannel *ioc,
> QCryptoTLSCreds *tlscreds,
> * TLS). If it is not available, fall back to
> * NBD_OPT_LIST for nicer error messages about a missing
> * export, then use NBD_OPT_EXPORT_NAME. */
> - result = nbd_opt_go(ioc, info, errp);
> + result = nbd_opt_info_go(ioc, NBD_OPT_GO, info, errp);
> if (result < 0) {
> return -EINVAL;
> }
> @@ -993,6 +1001,150 @@ int nbd_receive_negotiate(QIOChannel *ioc,
> QCryptoTLSCreds *tlscreds,
> return 0;
> }
>
> +/* Clean up result of nbd_receive_export_list */
> +void nbd_free_export_list(NBDExportInfo *info, int count)
> +{
> + int i, j;
> +
> + for (i = 0; info && i < count; i++) {
> + free(info[i].name);
> + free(info[i].description);
> + for (j = 0; j < info[i].n_contexts; j++) {
> + free(info[i].contexts[j]);
> + }
> + free(info[i].contexts);
> + }
> + free(info);
> +}
g_free
> +
> +/* Query details about a server's exports, then disconnect without
> + * going into transmission phase. Return a count of the exports listed
> + * in @info by the server, or -1 on error. Caller must free @info. */
> +int nbd_receive_export_list(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
> + const char *hostname, NBDExportInfo **info,
> + Error **errp)
> +{
> + int result;
> + int count = 0;
> + int i;
> + int rc;
> + int ret = -1;
> + NBDExportInfo *array = NULL;
> + uint32_t oldflags;
> + QIOChannel *sioc = NULL;
it's a bit confusing that you use sioc name for the second produced ioc, when
in nbd_client_init it's visa-versa.
So, I assume that you mean Secure ioc, when in nbd_client_init it is Socket ioc.
> + bool try_context = true;
> +
> + *info = NULL;
> + result = nbd_start_negotiate(ioc, tlscreds, hostname, &sioc, true, NULL,
> + errp);
> + if (tlscreds && sioc) {
> + ioc = sioc;
> + }
> +
> + switch (result) {
> + case 2:
> + /* meta contexts are only useful with structured reply */
> + try_context = false;
> + /* fall through */
> + case 3:
> + /* newstyle - use NBD_OPT_LIST to populate array, then try
> + * NBD_OPT_INFO on each array member. If structured replies
> + * are enabled, also try NBD_OPT_LIST_META_CONTEXT. */
> + if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
> + goto out;
> + }
> + while (1) {
> + char *name;
> + char *desc;
> +
> + rc = nbd_receive_list(ioc, NULL, NULL, &name, &desc, errp);
> + if (rc < 0) {
> + goto out;
> + } else if (rc == 0) {
> + break;
> + }
> + array = g_renew(NBDExportInfo, array, ++count);
> + memset(&array[count - 1], 0, sizeof(*array));
> + array[count - 1].name = name;
> + array[count - 1].description = desc;
> + array[count - 1].structured_reply = result == 3;
> + }
> +
> + for (i = 0; i < count; i++) {
> + array[i].request_sizes = true;
> + rc = nbd_opt_info_go(ioc, NBD_OPT_INFO, &array[i], errp);
> + if (rc < 0) {
> + goto out;
> + } else if (rc == 0) {
> + /* Pointless to try rest of loop. If OPT_INFO doesn't work,
> + * it's unlikely that meta contexts work either */
> + break;
> + }
> +
> + if (try_context) {
> + rc = nbd_negotiate_simple_meta_context(
> + ioc, NBD_OPT_LIST_META_CONTEXT, NULL, &array[i], errp);
> + if (rc < 0) {
> + goto out;
> + } else if (rc == 0) {
> + try_context = false;
> + }
> + }
> + }
> +
> + /* Send NBD_OPT_ABORT as a courtesy before hanging up */
> + nbd_send_opt_abort(ioc);
> + break;
> + case 1: /* newstyle, but limited to EXPORT_NAME */
> + error_setg(errp, "Server does not support export lists");
> + /* We can't even send NBD_OPT_ABORT, so merely hang up */
> + goto out;
> + case 0: /* oldstyle, parse length and flags */
> + array = g_new0(NBDExportInfo, 1);
> + array->name = g_strdup("");
> + count = 1;
> +
> + if (nbd_read(ioc, &array->size, sizeof(array->size), errp) < 0) {
> + error_prepend(errp, "Failed to read export length: ");
> + goto out;
> + }
> + array->size = be64_to_cpu(array->size);
> +
> + if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
> + error_prepend(errp, "Failed to read export flags: ");
> + goto out;
> + }
> + oldflags = be32_to_cpu(oldflags);
> + if (oldflags & ~0xffff) {
> + error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
> + goto out;
> + }
> + array->flags = oldflags;
^^^
this is a common part of nbd_receive_export_list and nbd_receive_negotiate,
can we move it to nbd_start_negotiate?
> +
> + /* Send NBD_CMD_DISC as a courtesy to the server, but ignore all
> + * errors now that we have the information we wanted. */
> + if (nbd_drop(ioc, 124, NULL) == 0) {
> + NBDRequest request = { .type = NBD_CMD_DISC };
> +
> + nbd_send_request(ioc, &request);
> + }
> + break;
> + default:
> + goto out;
> + }
> +
> + *info = array;
> + array = NULL;
> + ret = count;
tricky thing. shouldn't we set count to 0 too after it?
aha, no, go to nbd_free_export_list and see
info && i < count
so, it checks.
> +
> + out:
> + qio_channel_shutdown(ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
> + qio_channel_close(ioc, NULL);
interesting, why we don't close it (only shutdown) in other nbd code..
> + object_unref(OBJECT(sioc));
> + nbd_free_export_list(array, count); > + return ret;
> +}
> +
> #ifdef __linux__
> int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
> Error **errp)
> diff --git a/nbd/trace-events b/nbd/trace-events
> index 570b04997ff..2cf83ebed15 100644
> --- a/nbd/trace-events
> +++ b/nbd/trace-events
> @@ -2,7 +2,7 @@
> nbd_send_option_request(uint32_t opt, const char *name, uint32_t len)
> "Sending option request %" PRIu32" (%s), len %" PRIu32
> nbd_receive_option_reply(uint32_t option, const char *optname, uint32_t
> type, const char *typename, uint32_t length) "Received option reply %"
> PRIu32" (%s), type %" PRIu32" (%s), len %" PRIu32
> nbd_reply_err_unsup(uint32_t option, const char *name) "server doesn't
> understand request %" PRIu32 " (%s), attempting fallback"
> -nbd_opt_go_start(const char *name) "Attempting NBD_OPT_GO for export '%s'"
> +nbd_opt_go_start(const char *opt, const char *name) "Attempting %s for
> export '%s'"
> nbd_opt_go_success(void) "Export is good to go"
> nbd_opt_go_info_unknown(int info, const char *name) "Ignoring unknown info
> %d (%s)"
> nbd_opt_go_info_block_size(uint32_t minimum, uint32_t preferred, uint32_t
> maximum) "Block sizes are 0x%" PRIx32 ", 0x%" PRIx32 ", 0x%" PRIx32
>
--
Best regards,
Vladimir
