IPVS: Handle Scheduling errors.

IPVS: Handle Scheduling errors.

If ip_vs_conn_fill_param_persist return an error to ip_vs_sched_persist,
this error must propagate as ignored=-1 to ip_vs_schedule().
Errors from ip_vs_conn_new() in ip_vs_sched_persist() and ip_vs_schedule()
should also return *ignored=-1;

This patch just relies on the fact that ignored is 1 before calling
ip_vs_sched_persist().

Sent from Julian:
  "The new case when ip_vs_conn_fill_param_persist fails
   should set *ignored = -1, so that we can use NF_DROP,
   see below. *ignored = -1 should be also used for ip_vs_conn_new
   failure in ip_vs_sched_persist() and ip_vs_schedule().
   The new negative value should be handled in tcp,udp,sctp"

"To summarize:

- *ignored = 1:
      protocol tried to schedule (eg. on SYN), found svc but the
      svc/scheduler decides that this packet should be accepted with
      NF_ACCEPT because it must not be scheduled.

- *ignored = 0:
      scheduler can not find destination, so try bypass or
      return ICMP and then NF_DROP (ip_vs_leave).

- *ignored = -1:
      scheduler tried to schedule but fatal error occurred, eg.
      ip_vs_conn_new failure (ENOMEM) or ip_vs_sip_fill_param
      failure such as missing Call-ID, ENOMEM on skb_linearize
      or pe_data. In this case we should return NF_DROP without
      any attempts to send ICMP with ip_vs_leave."

More or less all ideas and input to this patch is work from
Julian Anastasov

Signed-off-by: Hans Schillstrom <hans.schillstrom@ericsson.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>