client/FwmarkClient.cpp

/*
 * Copyright (C) 2014 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 "FwmarkClient.h"

#include "FwmarkCommand.h"

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))

namespace {

const sockaddr_un FWMARK_SERVER_PATH = {AF_UNIX, "/dev/socket/fwmarkd"};

}  // namespace

bool FwmarkClient::shouldSetFwmark(int family) {
    return (family == AF_INET || family == AF_INET6) && !getenv(ANDROID_NO_USE_FWMARK_CLIENT);
}

bool FwmarkClient::shouldReportConnectComplete(int family) {
    // TODO: put getenv(ANDROID_FWMARK_METRICS_ONLY) behind the ro.debuggable system property
    // or else an app can evade connect logging just by setting the env variable
    return shouldSetFwmark(family) && !getenv(ANDROID_FWMARK_METRICS_ONLY);
}

FwmarkClient::FwmarkClient() : mChannel(-1) {
}

FwmarkClient::~FwmarkClient() {
    if (mChannel >= 0) {
        close(mChannel);
    }
}

int FwmarkClient::send(FwmarkCommand* data, int fd, FwmarkConnectInfo* connectInfo) {
    mChannel = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
    if (mChannel == -1) {
        return -errno;
    }

    if (TEMP_FAILURE_RETRY(connect(mChannel, reinterpret_cast<const sockaddr*>(&FWMARK_SERVER_PATH),
                                   sizeof(FWMARK_SERVER_PATH))) == -1) {
        // If we are unable to connect to the fwmark server, assume there's no error. This protects
        // against future changes if the fwmark server goes away.
        return 0;
    }

    iovec iov[2] = {
        { data, sizeof(*data) },
        { connectInfo, (connectInfo ? sizeof(*connectInfo) : 0) },
    };
    msghdr message;
    memset(&message, 0, sizeof(message));
    message.msg_iov = iov;
    message.msg_iovlen = ARRAY_SIZE(iov);

    union {
        cmsghdr cmh;
        char cmsg[CMSG_SPACE(sizeof(fd))];
    } cmsgu;

    if (data->cmdId != FwmarkCommand::QUERY_USER_ACCESS) {
        memset(cmsgu.cmsg, 0, sizeof(cmsgu.cmsg));
        message.msg_control = cmsgu.cmsg;
        message.msg_controllen = sizeof(cmsgu.cmsg);

        cmsghdr* const cmsgh = CMSG_FIRSTHDR(&message);
        cmsgh->cmsg_len = CMSG_LEN(sizeof(fd));
        cmsgh->cmsg_level = SOL_SOCKET;
        cmsgh->cmsg_type = SCM_RIGHTS;
        memcpy(CMSG_DATA(cmsgh), &fd, sizeof(fd));
    }

    if (TEMP_FAILURE_RETRY(sendmsg(mChannel, &message, 0)) == -1) {
        return -errno;
    }

    int error = 0;

    if (TEMP_FAILURE_RETRY(recv(mChannel, &error, sizeof(error), 0)) == -1) {
        return -errno;
    }

    return error;
}