nbd/client: prepare nbd_receive_reply for structured reply

In following patch nbd_receive_reply will be used both for simple
and structured reply header receiving.
NBDReply is altered into union of simple reply header and structured
reply chunk header, simple error translation moved to block/nbd-client
to be consistent with further structured reply error translation.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171027104037.8319-11-eblake@redhat.com>

2 files changed, 84 insertions, 23 deletions

diff --git a/nbd/client.c b/nbd/client.c
index 9acf745b79..4f0745f601 100644
--- a/nbd/client.c
+++ b/nbd/client.c
@@ -908,6 +908,57 @@ int nbd_send_request(QIOChannel *ioc, NBDRequest *request)
     return nbd_write(ioc, buf, sizeof(buf), NULL);
 }
 
+/* nbd_receive_simple_reply
+ * Read simple reply except magic field (which should be already read).
+ * Payload is not read (payload is possible for CMD_READ, but here we even
+ * don't know whether it take place or not).
+ */
+static int nbd_receive_simple_reply(QIOChannel *ioc, NBDSimpleReply *reply,
+                                    Error **errp)
+{
+    int ret;
+
+    assert(reply->magic == NBD_SIMPLE_REPLY_MAGIC);
+
+    ret = nbd_read(ioc, (uint8_t *)reply + sizeof(reply->magic),
+                   sizeof(*reply) - sizeof(reply->magic), errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    be32_to_cpus(&reply->error);
+    be64_to_cpus(&reply->handle);
+
+    return 0;
+}
+
+/* nbd_receive_structured_reply_chunk
+ * Read structured reply chunk except magic field (which should be already
+ * read).
+ * Payload is not read.
+ */
+static int nbd_receive_structured_reply_chunk(QIOChannel *ioc,
+                                              NBDStructuredReplyChunk *chunk,
+                                              Error **errp)
+{
+    int ret;
+
+    assert(chunk->magic == NBD_STRUCTURED_REPLY_MAGIC);
+
+    ret = nbd_read(ioc, (uint8_t *)chunk + sizeof(chunk->magic),
+                   sizeof(*chunk) - sizeof(chunk->magic), errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    be16_to_cpus(&chunk->flags);
+    be16_to_cpus(&chunk->type);
+    be64_to_cpus(&chunk->handle);
+    be32_to_cpus(&chunk->length);
+
+    return 0;
+}
+
 /* nbd_receive_reply
  * Returns 1 on success
  *         0 on eof, when no data was read (errp is not set)
@@ -915,38 +966,47 @@ int nbd_send_request(QIOChannel *ioc, NBDRequest *request)
  */
 int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp)
 {
-    uint8_t buf[NBD_REPLY_SIZE];
-    uint32_t magic;
     int ret;
 
-    ret = nbd_read_eof(ioc, buf, sizeof(buf), errp);
+    ret = nbd_read_eof(ioc, &reply->magic, sizeof(reply->magic), errp);
     if (ret <= 0) {
         return ret;
     }
 
-    /* Reply
-       [ 0 ..  3]    magic   (NBD_SIMPLE_REPLY_MAGIC)
-       [ 4 ..  7]    error   (0 == no error)
-       [ 7 .. 15]    handle
-     */
+    be32_to_cpus(&reply->magic);
 
-    magic = ldl_be_p(buf);
-    reply->error  = ldl_be_p(buf + 4);
-    reply->handle = ldq_be_p(buf + 8);
-
-    trace_nbd_receive_reply(magic, reply->error, nbd_err_lookup(reply->error),
-                            reply->handle);
-    reply->error = nbd_errno_to_system_errno(reply->error);
+    switch (reply->magic) {
+    case NBD_SIMPLE_REPLY_MAGIC:
+        ret = nbd_receive_simple_reply(ioc, &reply->simple, errp);
+        if (ret < 0) {
+            break;
+        }
 
-    if (reply->error == ESHUTDOWN) {
-        /* This works even on mingw which lacks a native ESHUTDOWN */
-        error_setg(errp, "server shutting down");
+        trace_nbd_receive_simple_reply(reply->simple.error,
+                                       nbd_err_lookup(reply->simple.error),
+                                       reply->handle);
+        if (reply->simple.error == NBD_ESHUTDOWN) {
+            /* This works even on mingw which lacks a native ESHUTDOWN */
+            error_setg(errp, "server shutting down");
+            return -EINVAL;
+        }
+        break;
+    case NBD_STRUCTURED_REPLY_MAGIC:
+        ret = nbd_receive_structured_reply_chunk(ioc, &reply->structured, errp);
+        if (ret < 0) {
+            break;
+        }
+        trace_nbd_receive_structured_reply_chunk(reply->structured.flags,
+                                                 reply->structured.type,
+                                                 reply->structured.handle,
+                                                 reply->structured.length);
+        break;
+    default:
+        error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", reply->magic);
         return -EINVAL;
     }
-
-    if (magic != NBD_SIMPLE_REPLY_MAGIC) {
-        error_setg(errp, "invalid magic (got 0x%" PRIx32 ")", magic);
-        return -EINVAL;
+    if (ret < 0) {
+        return ret;
     }
 
     return 1;
diff --git a/nbd/trace-events b/nbd/trace-events
index 596df96575..4a13757524 100644
--- a/nbd/trace-events
+++ b/nbd/trace-events
@@ -26,7 +26,8 @@ nbd_client_loop_ret(int ret, const char *error) "NBD loop returned %d: %s"
 nbd_client_clear_queue(void) "Clearing NBD queue"
 nbd_client_clear_socket(void) "Clearing NBD socket"
 nbd_send_request(uint64_t from, uint32_t len, uint64_t handle, uint16_t flags, uint16_t type, const char *name) "Sending request to server: { .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64 ", .flags = 0x%" PRIx16 ", .type = %" PRIu16 " (%s) }"
-nbd_receive_reply(uint32_t magic, int32_t error, const char *errname, uint64_t handle) "Got reply: { magic = 0x%" PRIx32 ", .error = %" PRId32 " (%s), handle = %" PRIu64" }"
+nbd_receive_simple_reply(int32_t error, const char *errname, uint64_t handle) "Got simple reply: { .error = %" PRId32 " (%s), handle = %" PRIu64" }"
+nbd_receive_structured_reply_chunk(uint16_t flags, uint16_t type, uint64_t handle, uint32_t length) "Got structured reply chunk: { flags = 0x%" PRIx16 ", type = %d, handle = %" PRIu64 ", length = %" PRIu32 " }"
 
 # nbd/common.c
 nbd_unknown_error(int err) "Squashing unexpected error %d to EINVAL"