/*
 * Copyright (C) 2010 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.
 */

#include <arpa/inet.h>
#include <dirent.h>
#include <errno.h>
#include <linux/if.h>
#include <math.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
#include <pthread.h>
#include <resolv_netid.h>
#include <net/if.h>

#define LOG_TAG "DnsProxyListener"
#define DBG 0
#define VDBG 0

#include <chrono>

#include <cutils/log.h>
#include <binder/IServiceManager.h>
#include <utils/String16.h>
#include <sysutils/SocketClient.h>

#include "Fwmark.h"
#include "DnsProxyListener.h"
#include "NetdConstants.h"
#include "NetworkController.h"
#include "ResponseCode.h"
#include "android/net/metrics/IDnsEventListener.h"

using android::String16;
using android::interface_cast;
using android::net::metrics::IDnsEventListener;

DnsProxyListener::DnsProxyListener(const NetworkController* netCtrl) :
        FrameworkListener("dnsproxyd"), mNetCtrl(netCtrl) {
    registerCmd(new GetAddrInfoCmd(this));
    registerCmd(new GetHostByAddrCmd(this));
    registerCmd(new GetHostByNameCmd(this));
}

DnsProxyListener::GetAddrInfoHandler::GetAddrInfoHandler(
        SocketClient *c, char* host, char* service, struct addrinfo* hints,
        const struct android_net_context& netcontext,
        const android::sp<android::net::metrics::IDnsEventListener>& dnsEventListener)
        : mClient(c),
          mHost(host),
          mService(service),
          mHints(hints),
          mNetContext(netcontext),
          mDnsEventListener(dnsEventListener) {
}

DnsProxyListener::GetAddrInfoHandler::~GetAddrInfoHandler() {
    free(mHost);
    free(mService);
    free(mHints);
}

void DnsProxyListener::GetAddrInfoHandler::start() {
    pthread_t thread;
    pthread_create(&thread, NULL,
                   DnsProxyListener::GetAddrInfoHandler::threadStart, this);
    pthread_detach(thread);
}

void* DnsProxyListener::GetAddrInfoHandler::threadStart(void* obj) {
    GetAddrInfoHandler* handler = reinterpret_cast<GetAddrInfoHandler*>(obj);
    handler->run();
    delete handler;
    pthread_exit(NULL);
    return NULL;
}

android::sp<IDnsEventListener> DnsProxyListener::getDnsEventListener() {
    if (mDnsEventListener == nullptr) {
        // Use checkService instead of getService because getService waits for 5 seconds for the
        // service to become available. The DNS resolver inside netd is started much earlier in the
        // boot sequence than the framework DNS listener, and we don't want to delay all DNS lookups
        // for 5 seconds until the DNS listener starts up.
        android::sp<android::IBinder> b = android::defaultServiceManager()->checkService(
                android::String16("dns_listener"));
        if (b != nullptr) {
            mDnsEventListener = interface_cast<IDnsEventListener>(b);
        }
    }
    // If the DNS listener service is dead, the binder call will just return an error, which should
    // be fine because the only impact is that we can't log DNS events. In any case, this should
    // only happen if the system server is going down, which means it will shortly be taking us down
    // with it.
    return mDnsEventListener;
}

static bool sendBE32(SocketClient* c, uint32_t data) {
    uint32_t be_data = htonl(data);
    return c->sendData(&be_data, sizeof(be_data)) == 0;
}

// Sends 4 bytes of big-endian length, followed by the data.
// Returns true on success.
static bool sendLenAndData(SocketClient* c, const int len, const void* data) {
    return sendBE32(c, len) && (len == 0 || c->sendData(data, len) == 0);
}

// Returns true on success
static bool sendhostent(SocketClient *c, struct hostent *hp) {
    bool success = true;
    int i;
    if (hp->h_name != NULL) {
        success &= sendLenAndData(c, strlen(hp->h_name)+1, hp->h_name);
    } else {
        success &= sendLenAndData(c, 0, "") == 0;
    }

    for (i=0; hp->h_aliases[i] != NULL; i++) {
        success &= sendLenAndData(c, strlen(hp->h_aliases[i])+1, hp->h_aliases[i]);
    }
    success &= sendLenAndData(c, 0, ""); // null to indicate we're done

    uint32_t buf = htonl(hp->h_addrtype);
    success &= c->sendData(&buf, sizeof(buf)) == 0;

    buf = htonl(hp->h_length);
    success &= c->sendData(&buf, sizeof(buf)) == 0;

    for (i=0; hp->h_addr_list[i] != NULL; i++) {
        success &= sendLenAndData(c, 16, hp->h_addr_list[i]);
    }
    success &= sendLenAndData(c, 0, ""); // null to indicate we're done
    return success;
}

static bool sendaddrinfo(SocketClient* c, struct addrinfo* ai) {
    // struct addrinfo {
    //      int     ai_flags;       /* AI_PASSIVE, AI_CANONNAME, AI_NUMERICHOST */
    //      int     ai_family;      /* PF_xxx */
    //      int     ai_socktype;    /* SOCK_xxx */
    //      int     ai_protocol;    /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
    //      socklen_t ai_addrlen;   /* length of ai_addr */
    //      char    *ai_canonname;  /* canonical name for hostname */
    //      struct  sockaddr *ai_addr;      /* binary address */
    //      struct  addrinfo *ai_next;      /* next structure in linked list */
    // };

    // Write the struct piece by piece because we might be a 64-bit netd
    // talking to a 32-bit process.
    bool success =
            sendBE32(c, ai->ai_flags) &&
            sendBE32(c, ai->ai_family) &&
            sendBE32(c, ai->ai_socktype) &&
            sendBE32(c, ai->ai_protocol);
    if (!success) {
        return false;
    }

    // ai_addrlen and ai_addr.
    if (!sendLenAndData(c, ai->ai_addrlen, ai->ai_addr)) {
        return false;
    }

    // strlen(ai_canonname) and ai_canonname.
    if (!sendLenAndData(c, ai->ai_canonname ? strlen(ai->ai_canonname) + 1 : 0, ai->ai_canonname)) {
        return false;
    }

    return true;
}

void DnsProxyListener::GetAddrInfoHandler::run() {
    if (DBG) {
        ALOGD("GetAddrInfoHandler, now for %s / %s / {%u,%u,%u,%u,%u}", mHost, mService,
                mNetContext.app_netid, mNetContext.app_mark,
                mNetContext.dns_netid, mNetContext.dns_mark,
                mNetContext.uid);
    }

    struct addrinfo* result = NULL;
    Stopwatch s;
    uint32_t rv = android_getaddrinfofornetcontext(mHost, mService, mHints, &mNetContext, &result);
    const int latencyMs = lround(s.timeTaken());

    if (rv) {
        // getaddrinfo failed
        mClient->sendBinaryMsg(ResponseCode::DnsProxyOperationFailed, &rv, sizeof(rv));
    } else {
        bool success = !mClient->sendCode(ResponseCode::DnsProxyQueryResult);
        struct addrinfo* ai = result;
        while (ai && success) {
            success = sendBE32(mClient, 1) && sendaddrinfo(mClient, ai);
            ai = ai->ai_next;
        }
        success = success && sendBE32(mClient, 0);
        if (!success) {
            ALOGW("Error writing DNS result to client");
        }
    }
    if (result) {
        freeaddrinfo(result);
    }
    mClient->decRef();
    if (mDnsEventListener != nullptr) {
        mDnsEventListener->onDnsEvent(mNetContext.dns_netid, IDnsEventListener::EVENT_GETADDRINFO,
                                      (int32_t) rv, latencyMs);
    }
}

DnsProxyListener::GetAddrInfoCmd::GetAddrInfoCmd(DnsProxyListener* dnsProxyListener) :
    NetdCommand("getaddrinfo"),
    mDnsProxyListener(dnsProxyListener) {
}

int DnsProxyListener::GetAddrInfoCmd::runCommand(SocketClient *cli,
                                            int argc, char **argv) {
    if (DBG) {
        for (int i = 0; i < argc; i++) {
            ALOGD("argv[%i]=%s", i, argv[i]);
        }
    }
    if (argc != 8) {
        char* msg = NULL;
        asprintf( &msg, "Invalid number of arguments to getaddrinfo: %i", argc);
        ALOGW("%s", msg);
        cli->sendMsg(ResponseCode::CommandParameterError, msg, false);
        free(msg);
        return -1;
    }

    char* name = argv[1];
    if (strcmp("^", name) == 0) {
        name = NULL;
    } else {
        name = strdup(name);
    }

    char* service = argv[2];
    if (strcmp("^", service) == 0) {
        service = NULL;
    } else {
        service = strdup(service);
    }

    struct addrinfo* hints = NULL;
    int ai_flags = atoi(argv[3]);
    int ai_family = atoi(argv[4]);
    int ai_socktype = atoi(argv[5]);
    int ai_protocol = atoi(argv[6]);
    unsigned netId = strtoul(argv[7], NULL, 10);
    uid_t uid = cli->getUid();

    struct android_net_context netcontext;
    mDnsProxyListener->mNetCtrl->getNetworkContext(netId, uid, &netcontext);

    if (ai_flags != -1 || ai_family != -1 ||
        ai_socktype != -1 || ai_protocol != -1) {
        hints = (struct addrinfo*) calloc(1, sizeof(struct addrinfo));
        hints->ai_flags = ai_flags;
        hints->ai_family = ai_family;
        hints->ai_socktype = ai_socktype;
        hints->ai_protocol = ai_protocol;
    }

    if (DBG) {
        ALOGD("GetAddrInfoHandler for %s / %s / {%u,%u,%u,%u,%u}",
             name ? name : "[nullhost]",
             service ? service : "[nullservice]",
             netcontext.app_netid, netcontext.app_mark,
             netcontext.dns_netid, netcontext.dns_mark,
             netcontext.uid);
    }

    cli->incRef();
    DnsProxyListener::GetAddrInfoHandler* handler =
            new DnsProxyListener::GetAddrInfoHandler(cli, name, service, hints, netcontext,
                                                     mDnsProxyListener->getDnsEventListener());
    handler->start();

    return 0;
}

/*******************************************************
 *                  GetHostByName                      *
 *******************************************************/
DnsProxyListener::GetHostByNameCmd::GetHostByNameCmd(DnsProxyListener* dnsProxyListener) :
      NetdCommand("gethostbyname"),
      mDnsProxyListener(dnsProxyListener) {
}

int DnsProxyListener::GetHostByNameCmd::runCommand(SocketClient *cli,
                                            int argc, char **argv) {
    if (DBG) {
        for (int i = 0; i < argc; i++) {
            ALOGD("argv[%i]=%s", i, argv[i]);
        }
    }
    if (argc != 4) {
        char* msg = NULL;
        asprintf(&msg, "Invalid number of arguments to gethostbyname: %i", argc);
        ALOGW("%s", msg);
        cli->sendMsg(ResponseCode::CommandParameterError, msg, false);
        free(msg);
        return -1;
    }

    uid_t uid = cli->getUid();
    unsigned netId = strtoul(argv[1], NULL, 10);
    char* name = argv[2];
    int af = atoi(argv[3]);

    if (strcmp(name, "^") == 0) {
        name = NULL;
    } else {
        name = strdup(name);
    }

    uint32_t mark = mDnsProxyListener->mNetCtrl->getNetworkForDns(&netId, uid);

    cli->incRef();
    DnsProxyListener::GetHostByNameHandler* handler =
            new DnsProxyListener::GetHostByNameHandler(cli, name, af, netId, mark,
                                                       mDnsProxyListener->getDnsEventListener());
    handler->start();

    return 0;
}

DnsProxyListener::GetHostByNameHandler::GetHostByNameHandler(
        SocketClient* c, char* name, int af, unsigned netId, uint32_t mark,
        const android::sp<android::net::metrics::IDnsEventListener>& dnsEventListener)
        : mClient(c),
          mName(name),
          mAf(af),
          mNetId(netId),
          mMark(mark),
          mDnsEventListener(dnsEventListener) {
}

DnsProxyListener::GetHostByNameHandler::~GetHostByNameHandler() {
    free(mName);
}

void DnsProxyListener::GetHostByNameHandler::start() {
    pthread_t thread;
    pthread_create(&thread, NULL,
            DnsProxyListener::GetHostByNameHandler::threadStart, this);
    pthread_detach(thread);
}

void* DnsProxyListener::GetHostByNameHandler::threadStart(void* obj) {
    GetHostByNameHandler* handler = reinterpret_cast<GetHostByNameHandler*>(obj);
    handler->run();
    delete handler;
    pthread_exit(NULL);
    return NULL;
}

void DnsProxyListener::GetHostByNameHandler::run() {
    if (DBG) {
        ALOGD("DnsProxyListener::GetHostByNameHandler::run\n");
    }

    Stopwatch s;
    struct hostent* hp = android_gethostbynamefornet(mName, mAf, mNetId, mMark);
    const int latencyMs = lround(s.timeTaken());

    if (DBG) {
        ALOGD("GetHostByNameHandler::run gethostbyname errno: %s hp->h_name = %s, name_len = %zu\n",
                hp ? "success" : strerror(errno),
                (hp && hp->h_name) ? hp->h_name : "null",
                (hp && hp->h_name) ? strlen(hp->h_name) + 1 : 0);
    }

    bool success = true;
    if (hp) {
        success = mClient->sendCode(ResponseCode::DnsProxyQueryResult) == 0;
        success &= sendhostent(mClient, hp);
    } else {
        success = mClient->sendBinaryMsg(ResponseCode::DnsProxyOperationFailed, NULL, 0) == 0;
    }

    if (!success) {
        ALOGW("GetHostByNameHandler: Error writing DNS result to client\n");
    }
    mClient->decRef();

    if (mDnsEventListener != nullptr) {
        mDnsEventListener->onDnsEvent(mNetId, IDnsEventListener::EVENT_GETHOSTBYNAME,
                                      h_errno, latencyMs);
    }
}


/*******************************************************
 *                  GetHostByAddr                      *
 *******************************************************/
DnsProxyListener::GetHostByAddrCmd::GetHostByAddrCmd(const DnsProxyListener* dnsProxyListener) :
        NetdCommand("gethostbyaddr"),
        mDnsProxyListener(dnsProxyListener) {
}

int DnsProxyListener::GetHostByAddrCmd::runCommand(SocketClient *cli,
                                            int argc, char **argv) {
    if (DBG) {
        for (int i = 0; i < argc; i++) {
            ALOGD("argv[%i]=%s", i, argv[i]);
        }
    }
    if (argc != 5) {
        char* msg = NULL;
        asprintf(&msg, "Invalid number of arguments to gethostbyaddr: %i", argc);
        ALOGW("%s", msg);
        cli->sendMsg(ResponseCode::CommandParameterError, msg, false);
        free(msg);
        return -1;
    }

    char* addrStr = argv[1];
    int addrLen = atoi(argv[2]);
    int addrFamily = atoi(argv[3]);
    uid_t uid = cli->getUid();
    unsigned netId = strtoul(argv[4], NULL, 10);

    void* addr = malloc(sizeof(struct in6_addr));
    errno = 0;
    int result = inet_pton(addrFamily, addrStr, addr);
    if (result <= 0) {
        char* msg = NULL;
        asprintf(&msg, "inet_pton(\"%s\") failed %s", addrStr, strerror(errno));
        ALOGW("%s", msg);
        cli->sendMsg(ResponseCode::OperationFailed, msg, false);
        free(addr);
        free(msg);
        return -1;
    }

    uint32_t mark = mDnsProxyListener->mNetCtrl->getNetworkForDns(&netId, uid);

    cli->incRef();
    DnsProxyListener::GetHostByAddrHandler* handler =
            new DnsProxyListener::GetHostByAddrHandler(cli, addr, addrLen, addrFamily, netId, mark);
    handler->start();

    return 0;
}

DnsProxyListener::GetHostByAddrHandler::GetHostByAddrHandler(SocketClient* c,
                                                             void* address,
                                                             int   addressLen,
                                                             int   addressFamily,
                                                             unsigned netId,
                                                             uint32_t mark)
        : mClient(c),
          mAddress(address),
          mAddressLen(addressLen),
          mAddressFamily(addressFamily),
          mNetId(netId),
          mMark(mark) {
}

DnsProxyListener::GetHostByAddrHandler::~GetHostByAddrHandler() {
    free(mAddress);
}

void DnsProxyListener::GetHostByAddrHandler::start() {
    pthread_t thread;
    pthread_create(&thread, NULL,
                   DnsProxyListener::GetHostByAddrHandler::threadStart, this);
    pthread_detach(thread);
}

void* DnsProxyListener::GetHostByAddrHandler::threadStart(void* obj) {
    GetHostByAddrHandler* handler = reinterpret_cast<GetHostByAddrHandler*>(obj);
    handler->run();
    delete handler;
    pthread_exit(NULL);
    return NULL;
}

void DnsProxyListener::GetHostByAddrHandler::run() {
    if (DBG) {
        ALOGD("DnsProxyListener::GetHostByAddrHandler::run\n");
    }
    struct hostent* hp;

    // NOTE gethostbyaddr should take a void* but bionic thinks it should be char*
    hp = android_gethostbyaddrfornet((char*)mAddress, mAddressLen, mAddressFamily, mNetId, mMark);

    if (DBG) {
        ALOGD("GetHostByAddrHandler::run gethostbyaddr errno: %s hp->h_name = %s, name_len = %zu\n",
                hp ? "success" : strerror(errno),
                (hp && hp->h_name) ? hp->h_name : "null",
                (hp && hp->h_name) ? strlen(hp->h_name) + 1 : 0);
    }

    bool success = true;
    if (hp) {
        success = mClient->sendCode(ResponseCode::DnsProxyQueryResult) == 0;
        success &= sendhostent(mClient, hp);
    } else {
        success = mClient->sendBinaryMsg(ResponseCode::DnsProxyOperationFailed, NULL, 0) == 0;
    }

    if (!success) {
        ALOGW("GetHostByAddrHandler: Error writing DNS result to client\n");
    }
    mClient->decRef();
}