xref: /system/core/libnetutils/dhcp_utils.c

/*
 * Copyright 2008, 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.
 */

/* Utilities for managing the dhcpcd DHCP client daemon */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#include <cutils/properties.h>

static const char DAEMON_NAME[]        = "dhcpcd";
static const char DAEMON_PROP_NAME[]   = "init.svc.dhcpcd";
static const char HOSTNAME_PROP_NAME[] = "net.hostname";
static const char DHCP_PROP_NAME_PREFIX[]  = "dhcp";
static const int NAP_TIME = 200;   /* wait for 200ms at a time */
                                  /* when polling for property values */
static char errmsg[100];

/*
 * Wait for a system property to be assigned a specified value.
 * If desired_value is NULL, then just wait for the property to
 * be created with any value. maxwait is the maximum amount of
 * time in seconds to wait before giving up.
 */
static int wait_for_property(const char *name, const char *desired_value, int maxwait)
{
    char value[PROPERTY_VALUE_MAX] = {'\0'};
    int maxnaps = (maxwait * 1000) / NAP_TIME;

    if (maxnaps < 1) {
        maxnaps = 1;
    }

    while (maxnaps-- > 0) {
        usleep(NAP_TIME * 1000);
        if (property_get(name, value, NULL)) {
            if (desired_value == NULL ||
                    strcmp(value, desired_value) == 0) {
                return 0;
            }
        }
    }
    return -1; /* failure */
}

static int fill_ip_info(const char *interface,
                     char *ipaddr,
                     char *gateway,
                     uint32_t *prefixLength,
                     char *dns1,
                     char *dns2,
                     char *server,
                     uint32_t  *lease)
{
    char prop_name[PROPERTY_KEY_MAX];
    char prop_value[PROPERTY_VALUE_MAX];

    snprintf(prop_name, sizeof(prop_name), "%s.%s.ipaddress", DHCP_PROP_NAME_PREFIX, interface);
    property_get(prop_name, ipaddr, NULL);

    snprintf(prop_name, sizeof(prop_name), "%s.%s.gateway", DHCP_PROP_NAME_PREFIX, interface);
    property_get(prop_name, gateway, NULL);

    snprintf(prop_name, sizeof(prop_name), "%s.%s.mask", DHCP_PROP_NAME_PREFIX, interface);
    if (property_get(prop_name, prop_value, NULL)) {
        int p;
        // this conversion is v4 only, but this dhcp client is v4 only anyway
        in_addr_t mask = ntohl(inet_addr(prop_value));
        // Check netmask is a valid IP address.  ntohl gives NONE response (all 1's) for
        // non 255.255.255.255 inputs.  if we get that value check if it is legit..
        if (mask == INADDR_NONE && strcmp(prop_value, "255.255.255.255") != 0) {
            snprintf(errmsg, sizeof(errmsg), "DHCP gave invalid net mask %s", prop_value);
            return -1;
        }
        for (p = 0; p < 32; p++) {
            if (mask == 0) break;
            // check for non-contiguous netmask, e.g., 255.254.255.0
            if ((mask & 0x80000000) == 0) {
                snprintf(errmsg, sizeof(errmsg), "DHCP gave invalid net mask %s", prop_value);
                return -1;
            }
            mask = mask << 1;
        }
        *prefixLength = p;
    }
    snprintf(prop_name, sizeof(prop_name), "%s.%s.dns1", DHCP_PROP_NAME_PREFIX, interface);
    property_get(prop_name, dns1, NULL);

    snprintf(prop_name, sizeof(prop_name), "%s.%s.dns2", DHCP_PROP_NAME_PREFIX, interface);
    property_get(prop_name, dns2, NULL);

    snprintf(prop_name, sizeof(prop_name), "%s.%s.server", DHCP_PROP_NAME_PREFIX, interface);
    property_get(prop_name, server, NULL);

    snprintf(prop_name, sizeof(prop_name), "%s.%s.leasetime", DHCP_PROP_NAME_PREFIX, interface);
    if (property_get(prop_name, prop_value, NULL)) {
        *lease = atol(prop_value);
    }
    return 0;
}

static const char *ipaddr_to_string(in_addr_t addr)
{
    struct in_addr in_addr;

    in_addr.s_addr = addr;
    return inet_ntoa(in_addr);
}

/*
 * Start the dhcp client daemon, and wait for it to finish
 * configuring the interface.
 */
int dhcp_do_request(const char *interface,
                    char *ipaddr,
                    char *gateway,
                    uint32_t *prefixLength,
                    char *dns1,
                    char *dns2,
                    char *server,
                    uint32_t  *lease)
{
    char result_prop_name[PROPERTY_KEY_MAX];
    char prop_value[PROPERTY_VALUE_MAX] = {'\0'};
    char daemon_cmd[PROPERTY_VALUE_MAX * 2];
    const char *ctrl_prop = "ctl.start";
    const char *desired_status = "running";

    snprintf(result_prop_name, sizeof(result_prop_name), "%s.%s.result",
            DHCP_PROP_NAME_PREFIX,
            interface);
    /* Erase any previous setting of the dhcp result property */
    property_set(result_prop_name, "");

    /* Start the daemon and wait until it's ready */
    if (property_get(HOSTNAME_PROP_NAME, prop_value, NULL) && (prop_value[0] != '\0'))
        snprintf(daemon_cmd, sizeof(daemon_cmd), "%s:-h %s %s", DAEMON_NAME,
                 prop_value, interface);
    else
        snprintf(daemon_cmd, sizeof(daemon_cmd), "%s:%s", DAEMON_NAME, interface);
    memset(prop_value, '\0', PROPERTY_VALUE_MAX);
    property_set(ctrl_prop, daemon_cmd);
    if (wait_for_property(DAEMON_PROP_NAME, desired_status, 10) < 0) {
        snprintf(errmsg, sizeof(errmsg), "%s", "Timed out waiting for dhcpcd to start");
        return -1;
    }

    /* Wait for the daemon to return a result */
    if (wait_for_property(result_prop_name, NULL, 30) < 0) {
        snprintf(errmsg, sizeof(errmsg), "%s", "Timed out waiting for DHCP to finish");
        return -1;
    }

    if (!property_get(result_prop_name, prop_value, NULL)) {
        /* shouldn't ever happen, given the success of wait_for_property() */
        snprintf(errmsg, sizeof(errmsg), "%s", "DHCP result property was not set");
        return -1;
    }
    if (strcmp(prop_value, "ok") == 0) {
        char dns_prop_name[PROPERTY_KEY_MAX];
        if (fill_ip_info(interface, ipaddr, gateway, prefixLength, dns1, dns2, server, lease)
                == -1) {
            return -1;
        }

        /* copy dns data to system properties - TODO - remove this after we have async
         * notification of renewal's */
        snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns1", interface);
        property_set(dns_prop_name, *dns1 ? ipaddr_to_string(*dns1) : "");
        snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns2", interface);
        property_set(dns_prop_name, *dns2 ? ipaddr_to_string(*dns2) : "");
        return 0;
    } else {
        snprintf(errmsg, sizeof(errmsg), "DHCP result was %s", prop_value);
        return -1;
    }
}

/**
 * Stop the DHCP client daemon.
 */
int dhcp_stop(const char *interface)
{
    char result_prop_name[PROPERTY_KEY_MAX];
    const char *ctrl_prop = "ctl.stop";
    const char *desired_status = "stopped";

    snprintf(result_prop_name, sizeof(result_prop_name), "%s.%s.result",
            DHCP_PROP_NAME_PREFIX,
            interface);
    /* Stop the daemon and wait until it's reported to be stopped */
    property_set(ctrl_prop, DAEMON_NAME);
    if (wait_for_property(DAEMON_PROP_NAME, desired_status, 5) < 0) {
        return -1;
    }
    property_set(result_prop_name, "failed");
    return 0;
}

/**
 * Release the current DHCP client lease.
 */
int dhcp_release_lease(const char *interface)
{
    const char *ctrl_prop = "ctl.stop";
    const char *desired_status = "stopped";

    /* Stop the daemon and wait until it's reported to be stopped */
    property_set(ctrl_prop, DAEMON_NAME);
    if (wait_for_property(DAEMON_PROP_NAME, desired_status, 5) < 0) {
        return -1;
    }
    return 0;
}

char *dhcp_get_errmsg() {
    return errmsg;
}