qemu-nbd: introduce nbd_do_receive_request

Group the receiving of a response and the associated data into a new function.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

nbd.c

@@ -611,6 +611,47 @@ static int nbd_do_send_reply(int csock, struct nbd_reply *reply,
     return rc;
 }
 
+static int nbd_do_receive_request(int csock, struct nbd_request *request,
+                                  uint8_t *data)
+{
+    int rc;
+
+    if (nbd_receive_request(csock, request) == -1) {
+        rc = -EIO;
+        goto out;
+    }
+
+    if (request->len > NBD_BUFFER_SIZE) {
+        LOG("len (%u) is larger than max len (%u)",
+            request->len, NBD_BUFFER_SIZE);
+        rc = -EINVAL;
+        goto out;
+    }
+
+    if ((request->from + request->len) < request->from) {
+        LOG("integer overflow detected! "
+            "you're probably being attacked");
+        rc = -EINVAL;
+        goto out;
+    }
+
+    TRACE("Decoding type");
+
+    if ((request->type & NBD_CMD_MASK_COMMAND) == NBD_CMD_WRITE) {
+        TRACE("Reading %u byte(s)", request->len);
+
+        if (read_sync(csock, data, request->len) != request->len) {
+            LOG("reading from socket failed");
+            rc = -EIO;
+            goto out;
+        }
+    }
+    rc = 0;
+
+out:
+    return rc;
+}
+
 int nbd_trip(BlockDriverState *bs, int csock, off_t size,
              uint64_t dev_offset, uint32_t nbdflags,
              uint8_t *data)
@@ -621,22 +662,17 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size,
 
     TRACE("Reading request.");
 
-    if (nbd_receive_request(csock, &request) == -1)
+    ret = nbd_do_receive_request(csock, &request, data);
+    if (ret == -EIO) {
         return -1;
+    }
 
     reply.handle = request.handle;
     reply.error = 0;
 
-    if (request.len > NBD_BUFFER_SIZE) {
-        LOG("len (%u) is larger than max len (%u)",
-            request.len, NBD_BUFFER_SIZE);
-        goto invalid_request;
-    }
-
-    if ((request.from + request.len) < request.from) {
-        LOG("integer overflow detected! "
-            "you're probably being attacked");
-        goto invalid_request;
+    if (ret < 0) {
+        reply.error = -ret;
+        goto error_reply;
     }
 
     if ((request.from + request.len) > size) {
@@ -647,8 +683,6 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size,
         goto invalid_request;
     }
 
-    TRACE("Decoding type");
-
     switch (request.type & NBD_CMD_MASK_COMMAND) {
     case NBD_CMD_READ:
         TRACE("Request type is READ");
@@ -668,14 +702,6 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size,
     case NBD_CMD_WRITE:
         TRACE("Request type is WRITE");
 
-        TRACE("Reading %u byte(s)", request.len);
-
-        if (read_sync(csock, data, request.len) != request.len) {
-            LOG("reading from socket failed");
-            errno = EINVAL;
-            return -1;
-        }
-
         if (nbdflags & NBD_FLAG_READ_ONLY) {
             TRACE("Server is read-only, return error");
             reply.error = EROFS;