cmds/statsd/src/socket/StatsSocketListener.cpp

/*
 * Copyright (C) 2018 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 DEBUG false  // STOPSHIP if true
#include "Log.h"

#include <ctype.h>
#include <limits.h>
#include <stdio.h>
#include <sys/cdefs.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>

#include <cutils/sockets.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
#include <unordered_map>

#include "StatsSocketListener.h"
#include "guardrail/StatsdStats.h"
#include "stats_log_util.h"

namespace android {
namespace os {
namespace statsd {

StatsSocketListener::StatsSocketListener(std::shared_ptr<LogEventQueue> queue)
    : SocketListener(getLogSocket(), false /*start listen*/), mQueue(queue) {
}

StatsSocketListener::~StatsSocketListener() {
}

bool StatsSocketListener::onDataAvailable(SocketClient* cli) {
    static bool name_set;
    if (!name_set) {
        prctl(PR_SET_NAME, "statsd.writer");
        name_set = true;
    }

    // + 1 to ensure null terminator if MAX_PAYLOAD buffer is received
    char buffer[sizeof(android_log_header_t) + LOGGER_ENTRY_MAX_PAYLOAD + 1];
    struct iovec iov = {buffer, sizeof(buffer) - 1};

    alignas(4) char control[CMSG_SPACE(sizeof(struct ucred))];
    struct msghdr hdr = {
            NULL, 0, &iov, 1, control, sizeof(control), 0,
    };

    int socket = cli->getSocket();

    // To clear the entire buffer is secure/safe, but this contributes to 1.68%
    // overhead under logging load. We are safe because we check counts, but
    // still need to clear null terminator
    // memset(buffer, 0, sizeof(buffer));
    ssize_t n = recvmsg(socket, &hdr, 0);
    if (n <= (ssize_t)(sizeof(android_log_header_t))) {
        return false;
    }

    buffer[n] = 0;

    struct ucred* cred = NULL;

    struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
    while (cmsg != NULL) {
        if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_CREDENTIALS) {
            cred = (struct ucred*)CMSG_DATA(cmsg);
            break;
        }
        cmsg = CMSG_NXTHDR(&hdr, cmsg);
    }

    struct ucred fake_cred;
    if (cred == NULL) {
        cred = &fake_cred;
        cred->pid = 0;
        cred->uid = DEFAULT_OVERFLOWUID;
    }

    uint8_t* ptr = ((uint8_t*)buffer) + sizeof(android_log_header_t);
    n -= sizeof(android_log_header_t);

    // When a log failed to write to statsd socket (e.g., due ot EBUSY), a special message would
    // be sent to statsd when the socket communication becomes available again.
    // The format is android_log_event_int_t with a single integer in the payload indicating the
    // number of logs that failed. (*FORMAT MUST BE IN SYNC WITH system/core/libstats*)
    // Note that all normal stats logs are in the format of event_list, so there won't be confusion.
    //
    // TODO(b/80538532): In addition to log it in StatsdStats, we should properly reset the config.
    if (n == sizeof(android_log_event_long_t)) {
        android_log_event_long_t* long_event = reinterpret_cast<android_log_event_long_t*>(ptr);
        if (long_event->payload.type == EVENT_TYPE_LONG) {
            int64_t composed_long = long_event->payload.data;

            // format:
            // |last_tag|dropped_count|
            int32_t dropped_count = (int32_t)(0xffffffff & composed_long);
            int32_t last_atom_tag = (int32_t)((0xffffffff00000000 & (uint64_t)composed_long) >> 32);

            ALOGE("Found dropped events: %d error %d last atom tag %d from uid %d", dropped_count,
                  long_event->header.tag, last_atom_tag, cred->uid);
            StatsdStats::getInstance().noteLogLost((int32_t)getWallClockSec(), dropped_count,
                                                   long_event->header.tag, last_atom_tag, cred->uid,
                                                   cred->pid);
            return true;
        }
    }

    // move past the 4-byte StatsEventTag
    uint8_t* msg = ptr + sizeof(uint32_t);
    uint32_t len = n - sizeof(uint32_t);
    uint32_t uid = cred->uid;

    int64_t oldestTimestamp;
    if (!mQueue->push(std::make_unique<LogEvent>(msg, len, uid), &oldestTimestamp)) {
        StatsdStats::getInstance().noteEventQueueOverflow(oldestTimestamp);
    }

    return true;
}

int StatsSocketListener::getLogSocket() {
    static const char socketName[] = "statsdw";
    int sock = android_get_control_socket(socketName);

    if (sock < 0) {  // statsd started up in init.sh
        sock = socket_local_server(socketName, ANDROID_SOCKET_NAMESPACE_RESERVED, SOCK_DGRAM);

        int on = 1;
        if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
            return -1;
        }
    }
    return sock;
}

}  // namespace statsd
}  // namespace os
}  // namespace android