Structure used for scatter/gather data input when receiving multiple messages or packets in one go. You generally pass in an array of empty #GInputVectors and the operation will use all the buffers as if they were one buffer, and will set @bytes_received to the total number of bytes received across all #GInputVectors.

This structure closely mirrors `struct mmsghdr` and `struct msghdr` from the POSIX sockets API (see `man 2 recvmmsg`).

If @address is non-%NULL then it is set to the source address the message was received from, and the caller must free it afterwards.

If @control_messages is non-%NULL then it is set to an array of control messages received with the message (if any), and the caller must free it afterwards. @num_control_messages is set to the number of elements in this array, which may be zero.

Flags relevant to this message will be returned in @flags. For example, `MSG_EOR` or `MSG_TRUNC`.