server/ResolverController.cpp

/*
 * Copyright (C) 2011 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
 *
 *      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.
 */

#define LOG_TAG "ResolverController"
#define DBG 0

#include <algorithm>
#include <cstdlib>
#include <string>
#include <vector>
#include <cutils/log.h>
#include <net/if.h>
#include <sys/socket.h>
#include <netdb.h>

// NOTE: <resolv_netid.h> is a private C library header that provides
//       declarations for _resolv_set_nameservers_for_net and
//       _resolv_flush_cache_for_net
#include <resolv_netid.h>
#include <resolv_params.h>
#include <resolv_stats.h>

#include <android/net/INetd.h>

#include "ResolverController.h"
#include "ResolverStats.h"

int ResolverController::setDnsServers(unsigned netId, const char* searchDomains,
        const char** servers, int numservers, const __res_params* params) {
    if (DBG) {
        ALOGD("setDnsServers netId = %u\n", netId);
    }
    return -_resolv_set_nameservers_for_net(netId, servers, numservers, searchDomains, params);
}

int ResolverController::clearDnsServers(unsigned netId) {
    _resolv_set_nameservers_for_net(netId, NULL, 0, "", NULL);
    if (DBG) {
        ALOGD("clearDnsServers netId = %u\n", netId);
    }
    return 0;
}

int ResolverController::flushDnsCache(unsigned netId) {
    if (DBG) {
        ALOGD("flushDnsCache netId = %u\n", netId);
    }

    _resolv_flush_cache_for_net(netId);

    return 0;
}

int ResolverController::getDnsInfo(unsigned netId, std::vector<std::string>* servers,
        std::vector<std::string>* domains, __res_params* params,
        std::vector<android::net::ResolverStats>* stats) {
    using android::net::ResolverStats;
    using android::net::INetd;
    static_assert(ResolverStats::STATS_SUCCESSES == INetd::RESOLVER_STATS_SUCCESSES &&
            ResolverStats::STATS_ERRORS == INetd::RESOLVER_STATS_ERRORS &&
            ResolverStats::STATS_TIMEOUTS == INetd::RESOLVER_STATS_TIMEOUTS &&
            ResolverStats::STATS_INTERNAL_ERRORS == INetd::RESOLVER_STATS_INTERNAL_ERRORS &&
            ResolverStats::STATS_RTT_AVG == INetd::RESOLVER_STATS_RTT_AVG &&
            ResolverStats::STATS_LAST_SAMPLE_TIME == INetd::RESOLVER_STATS_LAST_SAMPLE_TIME &&
            ResolverStats::STATS_USABLE == INetd::RESOLVER_STATS_USABLE &&
            ResolverStats::STATS_COUNT == INetd::RESOLVER_STATS_COUNT,
            "AIDL and ResolverStats.h out of sync");
    int nscount = -1;
    sockaddr_storage res_servers[MAXNS];
    int dcount = -1;
    char res_domains[MAXDNSRCH][MAXDNSRCHPATH];
    __res_stats res_stats[MAXNS];
    servers->clear();
    domains->clear();
    *params = __res_params{};
    stats->clear();
    int revision_id = android_net_res_stats_get_info_for_net(netId, &nscount, res_servers, &dcount,
            res_domains, params, res_stats);

    // If the netId is unknown (which can happen for valid net IDs for which no DNS servers have
    // yet been configured), there is no revision ID. In this case there is no data to return.
    if (revision_id < 0) {
        return 0;
    }

    // Verify that the returned data is sane.
    if (nscount < 0 || nscount > MAXNS || dcount < 0 || dcount > MAXDNSRCH) {
        ALOGE("%s: nscount=%d, dcount=%d", __FUNCTION__, nscount, dcount);
        return -ENOTRECOVERABLE;
    }

    // Determine which servers are considered usable by the resolver.
    bool valid_servers[MAXNS];
    std::fill_n(valid_servers, MAXNS, false);
    android_net_res_stats_get_usable_servers(params, res_stats, nscount, valid_servers);

    // Convert the server sockaddr structures to std::string.
    stats->resize(nscount);
    for (int i = 0 ; i < nscount ; ++i) {
        char hbuf[NI_MAXHOST];
        int rv = getnameinfo(reinterpret_cast<const sockaddr*>(&res_servers[i]),
                sizeof(res_servers[i]), hbuf, sizeof(hbuf), nullptr, 0, NI_NUMERICHOST);
        std::string server_str;
        if (rv == 0) {
            server_str.assign(hbuf);
        } else {
            ALOGE("getnameinfo() failed for server #%d: %s", i, gai_strerror(rv));
            server_str.assign("<invalid>");
        }
        servers->push_back(std::move(server_str));
        android::net::ResolverStats& cur_stats = (*stats)[i];
        android_net_res_stats_aggregate(&res_stats[i], &cur_stats.successes, &cur_stats.errors,
                &cur_stats.timeouts, &cur_stats.internal_errors, &cur_stats.rtt_avg,
                &cur_stats.last_sample_time);
        cur_stats.usable = valid_servers[i];
    }

    // Convert the stack-allocated search domain strings to std::string.
    for (int i = 0 ; i < dcount ; ++i) {
        domains->push_back(res_domains[i]);
    }
    return 0;
}

int ResolverController::setResolverConfiguration(int32_t netId,
        const std::vector<std::string>& servers, const std::vector<std::string>& domains,
        const std::vector<int32_t>& params) {
    using android::net::INetd;
    if (params.size() != INetd::RESOLVER_PARAMS_COUNT) {
        ALOGE("%s: params.size()=%zu", __FUNCTION__, params.size());
        return -EINVAL;
    }

    std::vector<const char*> server_ptrs;
    for (const std::string& str : servers) {
        server_ptrs.push_back(str.c_str());
    }

    std::string domains_str;
    if (!domains.empty()) {
        domains_str = domains[0];
        for (size_t i = 1 ; i < domains.size() ; ++i) {
            domains_str += " " + domains[i];
        }
    }

    __res_params res_params;
    res_params.sample_validity = params[INetd::RESOLVER_PARAMS_SAMPLE_VALIDITY];
    res_params.success_threshold = params[INetd::RESOLVER_PARAMS_SUCCESS_THRESHOLD];
    res_params.min_samples = params[INetd::RESOLVER_PARAMS_MIN_SAMPLES];
    res_params.max_samples = params[INetd::RESOLVER_PARAMS_MAX_SAMPLES];

    return setDnsServers(netId, domains_str.c_str(), server_ptrs.data(), server_ptrs.size(),
            &res_params);
}

int ResolverController::getResolverInfo(int32_t netId, std::vector<std::string>* servers,
        std::vector<std::string>* domains, std::vector<int32_t>* params,
        std::vector<int32_t>* stats) {
    using android::net::ResolverStats;
    using android::net::INetd;
    __res_params res_params;
    std::vector<ResolverStats> res_stats;
    int ret = getDnsInfo(netId, servers, domains, &res_params, &res_stats);
    if (ret != 0) {
        return ret;
    }

    // Serialize the information for binder.
    ResolverStats::encodeAll(res_stats, stats);

    params->resize(INetd::RESOLVER_PARAMS_COUNT);
    (*params)[INetd::RESOLVER_PARAMS_SAMPLE_VALIDITY] = res_params.sample_validity;
    (*params)[INetd::RESOLVER_PARAMS_SUCCESS_THRESHOLD] = res_params.success_threshold;
    (*params)[INetd::RESOLVER_PARAMS_MIN_SAMPLES] = res_params.min_samples;
    (*params)[INetd::RESOLVER_PARAMS_MAX_SAMPLES] = res_params.max_samples;
    return 0;
}