taglinefilesource code
ssthresh143include/net/sock.hvolatile unsigned short  ssthresh;
ssthresh659net/ipv4/af_inet.csk->ssthresh = 0;
ssthresh655net/ipv4/tcp.csk->ssthresh = sk->cong_window >> 1; /* remember window where we lost */
ssthresh2754net/ipv4/tcp.cnewsk->ssthresh = 0;
ssthresh3297net/ipv4/tcp.cif (sk->cong_window < sk->ssthresh)