Check before redefining TCP_ZEROCOPY_RECEIVE
Check before redefining TCP_ZEROCOPY_RECEIVE

Summary: Check before redefining TCP_ZEROCOPY_RECEIVE

Reviewed By: henrywang8atfbdotcom, kevin-vigor

Differential Revision: D33982730

fbshipit-source-id: 1f6a6d95e247e0fe824d853c4504ef0bd17e76bf

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly