1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef _RES_STATS_H
18#define _RES_STATS_H
19
20#include <sys/socket.h>
21#include <stdbool.h>
22#include <stdint.h>
23#include <time.h>
24
25#include "resolv_params.h"
26
27#define RCODE_INTERNAL_ERROR    254
28#define RCODE_TIMEOUT           255
29
30/*
31 * Resolver reachability statistics and run-time parameters.
32 */
33
34struct __res_sample {
35    time_t			at;    // time in s at which the sample was recorded
36    uint16_t			rtt;   // round-trip time in ms
37    uint8_t			rcode; // the DNS rcode or RCODE_XXX defined above
38};
39
40struct __res_stats {
41    // Stats of the last <sample_count> queries.
42    struct __res_sample		samples[MAXNSSAMPLES];
43    // The number of samples stored.
44    uint8_t			sample_count;
45    // The next sample to modify.
46    uint8_t			sample_next;
47};
48
49/* Calculate the round-trip-time from start time t0 and end time t1. */
50extern int
51_res_stats_calculate_rtt(const struct timespec* t1, const struct timespec* t0);
52
53/* Initialize a sample for calculating server reachability statistics. */
54extern void
55_res_stats_set_sample(struct __res_sample* sample, time_t now, int rcode, int rtt);
56
57/* Returns true if the server is considered unusable, i.e. if the success rate is not lower than the
58 * threshold for the stored stored samples. If not enough samples are stored, the server is
59 * considered usable.
60 */
61extern bool
62_res_stats_usable_server(const struct __res_params* params, struct __res_stats* stats);
63
64__BEGIN_DECLS
65/* Aggregates the reachability statistics for the given server based on on the stored samples. */
66extern void
67android_net_res_stats_aggregate(struct __res_stats* stats, int* successes, int* errors,
68        int* timeouts, int* internal_errors, int* rtt_avg, time_t* last_sample_time)
69    __attribute__((visibility ("default")));
70
71extern int
72android_net_res_stats_get_info_for_net(unsigned netid, int* nscount,
73        struct sockaddr_storage servers[MAXNS], int* dcount, char domains[MAXDNSRCH][MAXDNSRCHPATH],
74        struct __res_params* params, struct __res_stats stats[MAXNS])
75    __attribute__((visibility ("default")));
76
77/* Returns an array of bools indicating which servers are considered good */
78extern void
79android_net_res_stats_get_usable_servers(const struct __res_params* params,
80        struct __res_stats stats[], int nscount, bool valid_servers[])
81    __attribute__((visibility ("default")));
82__END_DECLS
83
84#endif  // _RES_STATS_H
85