- The values (bitmap) are
- 1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN.
- 2: Enables TCP Fast Open on the server side, i.e., allowing data in
- a SYN packet to be accepted and passed to the application before
- 3-way hand shake finishes.
- 4: Send data in the opening SYN regardless of cookie availability and
- without a cookie option.
- 0x100: Accept SYN data w/o validating the cookie.
- 0x200: Accept data-in-SYN w/o any cookie option present.
- 0x400/0x800: Enable Fast Open on all listeners regardless of the
- TCP_FASTOPEN socket option. The two different flags designate two
- different ways of setting max_qlen without the TCP_FASTOPEN socket
- option.
+ The client support is enabled by flag 0x1 (on by default). The client
+ then must use sendmsg() or sendto() with the MSG_FASTOPEN flag,
+ rather than connect() to send data in SYN.