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/*
* Copyright (c) 2017-2019 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <hicn/hicn-light/config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <hicn/core/strategy.h>
#include <hicn/core/strategy_vft.h>
#include <hicn/core/nexthops.h>
#include <hicn/core/fib_entry.h>
#include "load_balancer.h"
#define AVG_PI_THRESHOLD 1e-3
#define AVG_PI_MIN 0.1
#define ALPHA 0.9
#define NEXTHOP_STATE_INIT { \
.pi = 0, \
.avg_pi = 0.0, \
.weight = 1, \
}
/* Shorthand */
#define nexthop_state_t strategy_load_balancer_nexthop_state_t
#define update_state(state) \
do { \
state->avg_pi = (state->avg_pi * ALPHA) + \
(state->pi * 1 - ALPHA); \
if (state->avg_pi < AVG_PI_THRESHOLD) \
state->avg_pi = AVG_PI_MIN; \
state->weight = 1 / state->avg_pi; \
} while(0)
#define update_state_inc(state) \
do { \
state->pi++; \
update_state(state); \
} while(0)
#define update_state_dec(state) \
do { \
if (state->pi > 0) \
state->pi--; \
update_state(state); \
} while(0)
#if 0
#define reset_all(nexthops, nexthops_state) \
do { \
unsigned _lb_var(nexthop); \
nexthops_foreach((state), _lb_var(nexthop), { \
(nexthop) = NEXTHOP_STATE_INIT; \
}); \
} while(0)
#else
#define reset_all(state)
#endif
static
void
strategy_load_balancer_initialize(strategy_entry_t * entry)
{
// XXXreset_all(entry->state);
// XXX TODO initialize nexthops
// XXX maybe merge with nexthop data structure
}
static
void
strategy_load_balancer_finalize(strategy_entry_t * entry)
{
/* Nothing to do */
}
static
void
strategy_load_balancer_add_nexthop(strategy_entry_t * entry, unsigned nexthop,
strategy_nexthop_state_t * state)
{
// Create and reset associated state
// if this is really a new nexthop
// XXX assume nexthop is inserted before
reset_all(state);
}
static
void
strategy_load_balancer_remove_nexthop(strategy_entry_t * entry, unsigned
nexthop, strategy_nexthop_state_t * state)
{
reset_all(state);
}
static
nexthops_t *
strategy_load_balancer_lookup_nexthops(strategy_entry_t * entry,
nexthops_t * nexthops, const msgbuf_t * msgbuf)
{
// TEMP
nexthop_state_t * state = NULL;
/* Compute the sum of weights of potential next hops */
double sum = 0;
unsigned i, nexthop;
nexthops_enumerate(nexthops, i, nexthop, {
(void)nexthop;
sum += nexthops_state(nexthops, i).load_balancer.weight;
});
/* Perform weighted random selection */
double distance = (double)rand() * sum / ((double)RAND_MAX + 1);
nexthops_enumerate(nexthops, i, nexthop, {
// XXX distance -= nexthop_state(nexthops, i).weight;
if (distance < 0) {
nexthops_select(nexthops, i);
update_state_inc(state); // XXX
break;
}
});
return nexthops;
}
static
void
strategy_load_balancer_on_timeout(strategy_entry_t * entry,
const nexthops_t * nexthops)
{
/*
* As we have few nexthops in FIB entry, and even fewer selected ones in
* nexthops, we can allow for linear search that will be very efficient
* CPU-wise.
*/
// XXX TODO
#if 0
unsigned nexthop;
nexthops_foreach(nexthops, nexthop, {
// XXX TODO leverage coexistence between nexthop and state
if (correct_nexthop_id(nexthop))
update_state_dec(&entry.state.nexthop_state);
});
#endif
}
static
void
strategy_load_balancer_on_data(strategy_entry_t * entry,
const nexthops_t * nexthops, const msgbuf_t * msgbuf,
Ticks pitEntryCreation, Ticks objReception)
{
strategy_load_balancer_on_timeout(entry, nexthops);
}
DECLARE_STRATEGY(load_balancer);
#undef nexthop_state_t
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