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* Copyright (C) 2016 The Android Open Source Project
* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#ifndef _RES_STATS_H
#define _RES_STATS_H
#include <sys/socket.h>
#include <stdbool.h>
#include <stdint.h>
#include <time.h>
#include "resolv_params.h"
#define RCODE_TIMEOUT 255
* Resolver reachability statistics and run-time parameters.
struct __res_sample {
time_t at; // time in s at which the sample was recorded
uint16_t rtt; // round-trip time in ms
uint8_t rcode; // the DNS rcode or RCODE_XXX defined above
struct __res_stats {
// Stats of the last <sample_count> queries.
struct __res_sample samples[MAXNSSAMPLES];
// The number of samples stored.
uint8_t sample_count;
// The next sample to modify.
uint8_t sample_next;
/* Calculate the round-trip-time from start time t0 and end time t1. */
extern int
_res_stats_calculate_rtt(const struct timespec* t1, const struct timespec* t0);
/* Initialize a sample for calculating server reachability statistics. */
extern void
_res_stats_set_sample(struct __res_sample* sample, time_t now, int rcode, int rtt);
/* Returns true if the server is considered unusable, i.e. if the success rate is not lower than the
* threshold for the stored stored samples. If not enough samples are stored, the server is
* considered usable.
extern bool
_res_stats_usable_server(const struct __res_params* params, struct __res_stats* stats);
/* Aggregates the reachability statistics for the given server based on on the stored samples. */
extern void
android_net_res_stats_aggregate(struct __res_stats* stats, int* successes, int* errors,
int* timeouts, int* internal_errors, int* rtt_avg, time_t* last_sample_time)
__attribute__((visibility ("default")));
extern int
android_net_res_stats_get_info_for_net(unsigned netid, int* nscount,
struct sockaddr_storage servers[MAXNS], int* dcount, char domains[MAXDNSRCH][MAXDNSRCHPATH],
struct __res_params* params, struct __res_stats stats[MAXNS])
__attribute__((visibility ("default")));
/* Returns an array of bools indicating which servers are considered good */
extern void
android_net_res_stats_get_usable_servers(const struct __res_params* params,
struct __res_stats stats[], int nscount, bool valid_servers[])
__attribute__((visibility ("default")));
#endif // _RES_STATS_H