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Commit fd837fa0 authored by chenbruce's avatar chenbruce
Browse files

Customized hostname/address table for DNS query 

- Some Android OEMs would like to create their own customized table
  (hostname/address mapping lists) that the resolver looks up before
  querying dns servers and gets the result directly.
- About DNS query, resolver checks system/etc/hosts first. If no data is
  found, resolver will query dns from the server. We add a new parameter to
  ResolverParamsParcel for OEMs to customize the table and OEMs can use
  setDnsConfigurationForNetwork to create the hostname/address lists. After
  OEMs create their own lists,the dns query will be following sequence.
  system/ect/hosts -> customized table -> dns server
- Add test cases: GetAddrInfoFromCustTable,
                  GetAddrInfoFromCustTable_InvalidInput,
                  GetAddrInfoFromCustTable_Modify

Bug: 122998288
Test: cd packages/modules/DnsResolver && atest
Change-Id: I7a2d689de74f0076f0115e0cb20fdc028903ae86
parent c727677f

Android.bp

+2 −2
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ aidl_interface { 
    local_include_dir: "binder",

    srcs: [

        "binder/android/net/IDnsResolver.aidl",

        "binder/android/net/ResolverHostsParcel.aidl",

        "binder/android/net/ResolverParamsParcel.aidl",

    ],

    imports: [
@@ -185,8 +186,7 @@ cc_test { 
        "libbinder_ndk",

    ],

    static_libs: [

        "dnsresolver_aidl_interface-cpp",

        "dnsresolver_aidl_interface-ndk_platform",

        "dnsresolver_aidl_interface-unstable-ndk_platform",

        "netd_event_listener_interface-ndk_platform",

        "libgmock",

        "liblog",

ResolverController.cpp

+1 −1
Original line number Diff line number Diff line
@@ -232,7 +232,7 @@ int ResolverController::setResolverConfiguration(const ResolverParamsParcel& res 
    res_params.retry_count = resolverParams.retryCount;



    return resolv_set_nameservers(resolverParams.netId, resolverParams.servers,

                                  resolverParams.domains, res_params);

                                  resolverParams.domains, res_params, resolverParams.hosts);

}



int ResolverController::getResolverInfo(int32_t netId, std::vector<std::string>* servers,

binder/android/net/ResolverHostsParcel.aidl

0 → 100644
+36 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2019 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.

 */



package android.net;



/**

 * A mapping list which translates hostnames or domain names to IP addresses

 * locally. Mapping multiple addresses to one hostname is supported.

 * It's similar to /etc/hosts file.

 *

 * {@hide}

 */

parcelable ResolverHostsParcel {

    /**

     * The IPv4 or IPv6 address corresponding to |hostName| field.

     */

    @utf8InCpp String ipAddr;



    /**

     * The hostname is a FQDN.

     */

    @utf8InCpp String hostName = "";

}

binder/android/net/ResolverParamsParcel.aidl

+13 −0
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ 


package android.net;



import android.net.ResolverHostsParcel;



/**

 * Configuration for a resolver parameters.

 *
@@ -97,4 +99,15 @@ parcelable ResolverParamsParcel { 
     * by the experiement flag.

     */

    int tlsConnectTimeoutMs = 0;



    /**

     * An IP/hostname mapping table for DNS local lookup customization.

     * WARNING: this is intended for local testing and other special situations.

     * Future versions of the DnsResolver module may break your assumptions.

     * Injecting static mappings for public hostnames is generally A VERY BAD IDEA,

     * since it makes it impossible for the domain owners to migrate the domain.

     * It is also not an effective domain blocking mechanism, because apps can

     * easily hardcode IPs or bypass the system DNS resolver.

     */

    ResolverHostsParcel[] hosts = {};

}

getaddrinfo.cpp

+30 −7
Original line number Diff line number Diff line
@@ -140,7 +140,9 @@ static int dns_getaddrinfo(const char* name, const addrinfo* pai, 
static void _sethtent(FILE**);

static void _endhtent(FILE**);

static struct addrinfo* _gethtent(FILE**, const char*, const struct addrinfo*);

static bool files_getaddrinfo(const char* name, const addrinfo* pai, addrinfo** res);

static struct addrinfo* getCustomHosts(const size_t netid, const char*, const struct addrinfo*);

static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,

                              addrinfo** res);

static int _find_src_addr(const struct sockaddr*, struct sockaddr*, unsigned, uid_t);



static int res_queryN(const char* name, res_target* target, res_state res, int* herrno);
@@ -464,7 +466,7 @@ static int explore_fqdn(const addrinfo* pai, const char* hostname, const char* s 
    // If the servname does not match socktype/protocol, return error code.

    if ((error = get_portmatch(pai, servname))) return error;



    if (!files_getaddrinfo(hostname, pai, &result)) {

    if (!files_getaddrinfo(netcontext->dns_netid, hostname, pai, &result)) {

        error = dns_getaddrinfo(hostname, pai, netcontext, &result, event);

    }

    if (error) {
@@ -1527,22 +1529,43 @@ found: 
    return res0;

}



static bool files_getaddrinfo(const char* name, const addrinfo* pai, addrinfo** res) {

static struct addrinfo* getCustomHosts(const size_t netid, const char* _Nonnull name,

                                       const struct addrinfo* _Nonnull pai) {

    struct addrinfo sentinel = {};

    struct addrinfo *res0, *res;

    res = &sentinel;

    std::vector<std::string> hosts = getCustomizedTableByName(netid, name);

    for (const std::string& host : hosts) {

        int error = getaddrinfo_numeric(host.c_str(), nullptr, *pai, &res0);

        if (!error && res0 != nullptr) {

            res->ai_next = res0;

            res = res0;

            res0 = nullptr;

        }

    }

    return sentinel.ai_next;

}



static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,

                              addrinfo** res) {

    struct addrinfo sentinel = {};

    struct addrinfo *p, *cur;

    FILE* hostf = NULL;

    FILE* hostf = nullptr;



    cur = &sentinel;



    _sethtent(&hostf);

    while ((p = _gethtent(&hostf, name, pai)) != NULL) {

    while ((p = _gethtent(&hostf, name, pai)) != nullptr) {

        cur->ai_next = p;

        while (cur && cur->ai_next) cur = cur->ai_next;

    }

    _endhtent(&hostf);



    if ((p = getCustomHosts(netid, name, pai)) != nullptr) {

        cur->ai_next = p;

    }



    *res = sentinel.ai_next;

    return sentinel.ai_next != NULL;

    return sentinel.ai_next != nullptr;

}



/* resolver logic */