CDRIVER-756: Properly check for error in mongoc_stream_writev

And add additional checks to verify the full write succeeded, or else
return descriptive error

Author: bjori

src/mongoc/mongoc-cluster.c

@@ -2238,18 +2238,8 @@ mongoc_cluster_sendv_to_server (mongoc_cluster_t              *cluster,
 
    BSON_ASSERT (cluster->iov.len);
 
-   if (!mongoc_stream_writev (stream, iov, iovcnt,
-                              cluster->sockettimeoutms)) {
-      char buf[128];
-      char * errstr;
-      errstr = bson_strerror_r(errno, buf, sizeof buf);
-
-      bson_set_error (error,
-                      MONGOC_ERROR_STREAM,
-                      MONGOC_ERROR_STREAM_SOCKET,
-                      "Failure during socket delivery: %s",
-                      errstr);
-      mongoc_cluster_disconnect_node (cluster, server_id);
+   if (!_mongoc_stream_writev_full (stream, iov, iovcnt,
+                                    cluster->sockettimeoutms, error)) {
       RETURN (false);
    }
 

src/mongoc/mongoc-stream-private.h

@@ -34,6 +34,13 @@ BSON_BEGIN_DECLS
 #define MONGOC_STREAM_GRIDFS   4
 #define MONGOC_STREAM_TLS      5
 
+bool
+_mongoc_stream_writev_full (mongoc_stream_t *stream,
+                            mongoc_iovec_t  *iov,
+                            size_t           iovcnt,
+                            int32_t          timeout_msec,
+                            bson_error_t    *error);
+
 
 BSON_END_DECLS
 

src/mongoc/mongoc-stream.c

@@ -368,3 +368,47 @@ mongoc_stream_check_closed (mongoc_stream_t *stream)
 
    RETURN (ret);
 }
+
+bool
+_mongoc_stream_writev_full (mongoc_stream_t *stream,
+                            mongoc_iovec_t  *iov,
+                            size_t           iovcnt,
+                            int32_t          timeout_msec,
+                            bson_error_t    *error)
+{
+   size_t total_bytes = 0;
+   int i;
+   ssize_t r;
+   ENTRY;
+
+   for (i = 0; i < iovcnt; i++) {
+      total_bytes += iov[i].iov_len;
+   }
+
+   r = mongoc_stream_writev(stream, iov, iovcnt, timeout_msec);
+   TRACE("writev returned: %ld", r);
+
+   if (r < 0) {
+      if (error) {
+         char buf[128];
+         char *errstr;
+
+         errstr = bson_strerror_r(errno, buf, sizeof(buf));
+
+         bson_set_error (error, MONGOC_ERROR_STREAM, MONGOC_ERROR_STREAM_SOCKET,
+                         "Failure during socket delivery: %s (%d)", errstr, errno);
+      }
+
+      RETURN(false);
+   }
+
+   if (r != total_bytes) {
+      bson_set_error (error, MONGOC_ERROR_STREAM, MONGOC_ERROR_STREAM_SOCKET,
+                      "Failure to send all requested bytes (only sent: %lld/%llu in %dms) during socket delivery",
+                      (long long)r, (unsigned long long)total_bytes, timeout_msec);
+
+      RETURN(false);
+   }
+
+   RETURN(true);
+}