taglinefilesource code
sock_wspace343include/net/sock.hextern unsigned long    sock_wspace(struct sock *sk);
sock_wspace387net/ipv4/packet.csock_wspace,
sock_wspace311net/ipv4/raw.csock_wspace,
sock_wspace5417net/ipv4/tcp.csock_wspace,
sock_wspace741net/ipv4/udp.csock_wspace,