When doing mbuf queueing, the packet filter hooks in ether_demux(), ip_input(), and ip6_input() are by-passed. This means that the packet filters don't process incoming packets, which might result in connection failures. For example, the TCP sequence number validation, will result in dropping valid packets.
Please note that this patch is only disabling mbuf queueing, not LRO.
Thanks to Herbert J. Skuhra for reporting the issue.