NOTES

/* Do not allow orphaned sockets to eat all our resources.
 * This is direct violation of TCP specs, but it is required
 * to prevent DoS attacks. It is called when a retransmission timeout
 * or zero probe timeout occurs on orphaned socket.
 *
 * Criteria is still not confirmed experimentally and may change.
 * We kill the socket, if:
 * 1. If number of orphaned sockets exceeds an administratively configured
 *    limit.
 * 2. If we have strong memory pressure.
 */

tcp_timer.c line 66


also write timers are around

                retry_until = sysctl_tcp_retries2;
tcp_timer.c line 148


later on

        /* *WARNING* RFC 1122 forbids this
         *
         * It doesn't AFAIK, because we kill the retransmit timer -AK
         *
         * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
         * this behaviour in Solaris down as a bug fix. [AC]
         *
         * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
         * even if they advertise zero window. Hence, connection is killed only
         * if we received no ACKs for normal connection timeout. It is not killed
         * only because window stays zero for some time, window may be zero
         * until armageddon and even later. We are in full accordance
         * with RFCs, only probe timer combines both retransmission timeout
         * and probe timeout in one bottle.                             --ANK
         */