[Qemu-devel] [PATCH v3 10/19] nbd/client: Split out nbd_send_one_meta_context()

[Eric Blake <eblake@redhat.com>]

Refactor nbd_negotiate_simple_meta_context() to pull out the
code that can be reused to send a LIST request for 0 or 1 query.
No semantic change.  The old comment about 'sizeof(uint32_t)'
being equivalent to '/* number of queries */' is no longer
needed, now that we are computing 'sizeof(queries)' instead.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181215135324.152629-14-eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

---
v3: Improve commit message [Rich], formatting tweak [checkpatch],
rebase to dropped patch
---
 nbd/client.c     | 67 +++++++++++++++++++++++++++++++++---------------
 nbd/trace-events |  2 +-
 2 files changed, 48 insertions(+), 21 deletions(-)

diff --git a/nbd/client.c b/nbd/client.c
index 77993890f04..3c716be2719 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -629,6 +629,49 @@ static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
     return QIO_CHANNEL(tioc);
 }

+/*
+ * nbd_send_one_meta_context:
+ * Send 0 or 1 set/list meta context queries.
+ * Return 0 on success, -1 with errp set for any error
+ */
+static int nbd_send_one_meta_context(QIOChannel *ioc,
+                                     uint32_t opt,
+                                     const char *export,
+                                     const char *query,
+                                     Error **errp)
+{
+    int ret;
+    uint32_t export_len = strlen(export);
+    uint32_t queries = !!query;
+    uint32_t context_len = 0;
+    uint32_t data_len;
+    char *data;
+    char *p;
+
+    data_len = sizeof(export_len) + export_len + sizeof(queries);
+    if (query) {
+        context_len = strlen(query);
+        data_len += sizeof(context_len) + context_len;
+    } else {
+        assert(opt == NBD_OPT_LIST_META_CONTEXT);
+    }
+    data = g_malloc(data_len);
+    p = data;
+
+    trace_nbd_opt_meta_request(nbd_opt_lookup(opt), query ?: "(all)", export);
+    stl_be_p(p, export_len);
+    memcpy(p += sizeof(export_len), export, export_len);
+    stl_be_p(p += export_len, queries);
+    if (query) {
+        stl_be_p(p += sizeof(uint32_t), context_len);
+        memcpy(p += sizeof(context_len), query, context_len);
+    }
+
+    ret = nbd_send_option_request(ioc, opt, data_len, data, errp);
+    g_free(data);
+    return ret;
+}
+
 /* nbd_negotiate_simple_meta_context:
  * Request the server to set the meta context for export @info->name
  * using @info->x_dirty_bitmap with a fallback to "base:allocation",
@@ -653,26 +696,10 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
     NBDOptionReply reply;
     const char *context = info->x_dirty_bitmap ?: "base:allocation";
     bool received = false;
-    uint32_t export_len = strlen(info->name);
-    uint32_t context_len = strlen(context);
-    uint32_t data_len = sizeof(export_len) + export_len +
-                        sizeof(uint32_t) + /* number of queries */
-                        sizeof(context_len) + context_len;
-    char *data = g_malloc(data_len);
-    char *p = data;

-    trace_nbd_opt_meta_request(context, info->name);
-    stl_be_p(p, export_len);
-    memcpy(p += sizeof(export_len), info->name, export_len);
-    stl_be_p(p += export_len, 1);
-    stl_be_p(p += sizeof(uint32_t), context_len);
-    memcpy(p += sizeof(context_len), context, context_len);
-
-    ret = nbd_send_option_request(ioc, NBD_OPT_SET_META_CONTEXT, data_len, data,
-                                  errp);
-    g_free(data);
-    if (ret < 0) {
-        return ret;
+    if (nbd_send_one_meta_context(ioc, NBD_OPT_SET_META_CONTEXT,
+                                  info->name, context, errp) < 0) {
+        return -1;
     }

     if (nbd_receive_option_reply(ioc, NBD_OPT_SET_META_CONTEXT, &reply,
@@ -689,7 +716,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
     if (reply.type == NBD_REP_META_CONTEXT) {
         char *name;

-        if (reply.length != sizeof(info->context_id) + context_len) {
+        if (reply.length != sizeof(info->context_id) + strlen(context)) {
             error_setg(errp, "Failed to negotiate meta context '%s', server "
                        "answered with unexpected length %" PRIu32, context,
                        reply.length);
diff --git a/nbd/trace-events b/nbd/trace-events
index c3966d2b653..59521e47a3d 100644
--- a/nbd/trace-events
+++ b/nbd/trace-events
@@ -12,7 +12,7 @@ nbd_receive_query_exports_start(const char *wantname) "Querying export list for
 nbd_receive_query_exports_success(const char *wantname) "Found desired export name '%s'"
 nbd_receive_starttls_new_client(void) "Setting up TLS"
 nbd_receive_starttls_tls_handshake(void) "Starting TLS handshake"
-nbd_opt_meta_request(const char *context, const char *export) "Requesting to set meta context %s for export %s"
+nbd_opt_meta_request(const char *optname, const char *context, const char *export) "Requesting %s %s for export %s"
 nbd_opt_meta_reply(const char *context, uint32_t id) "Received mapping of context %s to id %" PRIu32
 nbd_receive_negotiate(void *tlscreds, const char *hostname) "Receiving negotiation tlscreds=%p hostname=%s"
 nbd_receive_negotiate_magic(uint64_t magic) "Magic is 0x%" PRIx64
-- 
2.20.1