sk_stream_write_space
void sk_stream_write_space(struct sock *sk);
sk->sk_write_space = sk_stream_write_space;
sk_stream_write_space,
sk->sk_write_space = sk_stream_write_space;
INDIRECT_CALL_1(sk->sk_write_space, sk_stream_write_space, sk);
sk->sk_write_space = sk_stream_write_space;
WARN_ON_ONCE(sk->sk_write_space != sk_stream_write_space);