net/core/request_sock.c

20  * Maximum number of SYN_RECV sockets in queue per LISTEN socket.
21  * One SYN_RECV socket costs about 80bytes on a 32bit machine.
23  * but then some measure against one socket starving all other sockets
44  * This function is called to set a Fast Open socket's "fastopen_rsk" field
45  * to NULL when a TFO socket no longer needs to access the request_sock.
49  * Before TFO, a child socket is created only after 3WHS is completed,
51  * complex with TFO. A child socket, accepted or not, has to access its
54  * until either the child socket is accepted, or in the rare case when the
57  * In short, a request socket is only freed after BOTH 3WHS has completed
58  * (or aborted) and the child socket has been accepted (or listener closed).
59  * When a child socket is accepted, its corresponding req->sk is set to
61  * will be used by the code below to determine if a child socket has been
65  * Note that fastopen_rsk is only accessed from the child socket's context
66  * with its socket lock held. But a request_sock (req) can be accessed by
67  * both its child socket through fastopen_rsk, and a listener socket through
75  * Note that another solution was to simply use the existing socket lock
76  * from the listener. But first socket lock is difficult to use. It is not
80  * acquire a child's lock while holding listener's socket lock. A corner
100 	if (req->sk)	/* the child socket hasn't been accepted yet */  in reqsk_fastopen_remove()