libnetutils 中的 ifc_utils.c

最新推荐文章于 2025-01-14 00:07:47 发布

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文章标签：

#struct #socket #interface #returning #string #null

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本文详细解析了Android系统中用于网络配置的关键接口实现，包括接口的初始化、关闭、启用及禁用等功能。此外还介绍了如何设置IP地址、前缀长度、网关以及DNS服务器等网络参数，并展示了移除默认路由和清理连接的方法。

源代码位于： system/core/libnetutils/*

0605$ ls system/core/libnetutils/
Android.mk    dhcpclient.c  dhcpmsg.c     dhcpmsg.h     dhcp_utils.c  ifc_utils.c   ifc_utils.c~  NOTICE        packet.c      packet.h

1. ifc_init(), ifc_close() :

int ifc_init(void)
{
    int ret;
    if (ifc_ctl_sock == -1) {
        ifc_ctl_sock = socket(AF_INET, SOCK_DGRAM, 0); //socket通信
        if (ifc_ctl_sock < 0) {
            printerr("socket() failed: %s\n", strerror(errno));
        }
    }

    ret = ifc_ctl_sock < 0 ? -1 : 0;
    if (DBG) printerr("ifc_init_returning %d", ret);
    return ret;
}

int ifc_init6(void)
{
    if (ifc_ctl_sock6 == -1) {
        ifc_ctl_sock6 = socket(AF_INET6, SOCK_DGRAM, 0);
        if (ifc_ctl_sock6 < 0) {
            printerr("socket() failed: %s\n", strerror(errno));
        }
    }
    return ifc_ctl_sock6 < 0 ? -1 : 0;
}

void ifc_close(void)
{
    if (DBG) printerr("ifc_close");
    if (ifc_ctl_sock != -1) {
        (void)close(ifc_ctl_sock); // close socket
        ifc_ctl_sock = -1;
    }
}

void ifc_close6(void)
{
    if (ifc_ctl_sock6 != -1) {
        (void)close(ifc_ctl_sock6);
        ifc_ctl_sock6 = -1;
    }
}

2. ifc_up(), ifc_down():

int ifc_up(const char *name)
{
    int ret = ifc_set_flags(name, IFF_UP, 0);
    if (DBG) printerr("ifc_up(%s) = %d", name, ret);
    return ret;
}

int ifc_down(const char *name)
{
    int ret = ifc_set_flags(name, 0, IFF_UP);
    if (DBG) printerr("ifc_down(%s) = %d", name, ret);
    return ret;
}

static int ifc_set_flags(const char *name, unsigned set, unsigned clr)
{
    struct ifreq ifr;
    ifc_init_ifr(name, &ifr);

    if(ioctl(ifc_ctl_sock, SIOCGIFFLAGS, &ifr) < 0) return -1;
    ifr.ifr_flags = (ifr.ifr_flags & (~clr)) | set;
    return ioctl(ifc_ctl_sock, SIOCSIFFLAGS, &ifr);
}

static void ifc_init_ifr(const char *name, struct ifreq *ifr)
{
    memset(ifr, 0, sizeof(struct ifreq));
    strncpy(ifr->ifr_name, name, IFNAMSIZ);
    ifr->ifr_name[IFNAMSIZ - 1] = 0;
}

3. ifc_enable(), ifc_disable():

int ifc_enable(const char *ifname)
{
    int result;

    ifc_init();
    result = ifc_up(ifname);
    ifc_close();
    return result;
}

int ifc_disable(const char *ifname)
{
    unsigned addr, count;
    int result;

    ifc_init();
    result = ifc_down(ifname);

    ifc_set_addr(ifname, 0);
    for (count=0, addr=1;((addr != 0) && (count < 255)); count++) {
       if (ifc_get_addr(ifname, &addr) < 0)
            break;
       if (addr)
          ifc_set_addr(ifname, 0);
    }

    ifc_close();
    return result;
}

d. int ifc_set_addr(const char *name, in_addr_t addr)

int ifc_set_addr(const char *name, in_addr_t addr)
{
    struct ifreq ifr;
    int ret;

    ifc_init_ifr(name, &ifr);
    init_sockaddr_in(&ifr.ifr_addr, addr);

    ret = ioctl(ifc_ctl_sock, SIOCSIFADDR, &ifr);
    if (DBG) printerr("ifc_set_addr(%s, xx) = %d", name, ret);
    return ret;
}

static void init_sockaddr_in(struct sockaddr *sa, in_addr_t addr)
{
    struct sockaddr_in *sin = (struct sockaddr_in *) sa;
    sin->sin_family = AF_INET;
    sin->sin_port = 0;
    sin->sin_addr.s_addr = addr;
}

4. int ifc_reset_connections(const char *ifname, const int reset_mask)

#define RESET_IPV4_ADDRESSES 0x01
#define RESET_IPV6_ADDRESSES 0x02
#define RESET_ALL_ADDRESSES  (RESET_IPV4_ADDRESSES | RESET_IPV6_ADDRESSES)

int ifc_reset_connections(const char *ifname, const int reset_mask)
{
#ifdef HAVE_ANDROID_OS
    int result, success;
    in_addr_t myaddr;
    struct ifreq ifr;
    struct in6_ifreq ifr6;

    if (reset_mask & RESET_IPV4_ADDRESSES) {
        /* IPv4. Clear connections on the IP address. */
        ifc_init();
        ifc_get_info(ifname, &myaddr, NULL, NULL);
        ifc_init_ifr(ifname, &ifr);
        init_sockaddr_in(&ifr.ifr_addr, myaddr);
        result = ioctl(ifc_ctl_sock, SIOCKILLADDR,  &ifr);
        ifc_close();
    } else {
        result = 0;
    }

    if (reset_mask & RESET_IPV6_ADDRESSES) {
        /*
         * IPv6. On Linux, when an interface goes down it loses all its IPv6
         * addresses, so we don't know which connections belonged to that interface
         * So we clear all unused IPv6 connections on the device by specifying an
         * empty IPv6 address.
         */
        ifc_init6();
        // This implicitly specifies an address of ::, i.e., kill all IPv6 sockets.
        memset(&ifr6, 0, sizeof(ifr6));
        success = ioctl(ifc_ctl_sock6, SIOCKILLADDR,  &ifr6);
        if (result == 0) {
            result = success;
        }
        ifc_close6();
    }

    return result;
#else
    return 0;
#endif
}

int ifc_get_info(const char *name, in_addr_t *addr, int *prefixLength, unsigned *flags)
{
    struct ifreq ifr;
    ifc_init_ifr(name, &ifr);

    if (addr != NULL) {
        if(ioctl(ifc_ctl_sock, SIOCGIFADDR, &ifr) < 0) {
            *addr = 0;
        } else {
            *addr = ((struct sockaddr_in*) &ifr.ifr_addr)->sin_addr.s_addr;
        }
    }

    if (prefixLength != NULL) {
        if(ioctl(ifc_ctl_sock, SIOCGIFNETMASK, &ifr) < 0) {
            *prefixLength = 0;
        } else {
            *prefixLength = ipv4NetmaskToPrefixLength((int)
                    ((struct sockaddr_in*) &ifr.ifr_addr)->sin_addr.s_addr);
        }
    }

    if (flags != NULL) {
        if(ioctl(ifc_ctl_sock, SIOCGIFFLAGS, &ifr) < 0) {
            *flags = 0;
        } else {
            *flags = ifr.ifr_flags;
        }
    }

    return 0;
}

5. int ifc_remove_default_route(const char *ifname):

/*
 * Removes the default route for the named interface.
 */
int ifc_remove_default_route(const char *ifname)
{
    struct rtentry rt;
    int result;

    ifc_init();
    memset(&rt, 0, sizeof(rt));
    rt.rt_dev = (void *)ifname;
    rt.rt_flags = RTF_UP|RTF_GATEWAY;
    init_sockaddr_in(&rt.rt_dst, 0);
    if ((result = ioctl(ifc_ctl_sock, SIOCDELRT, &rt)) < 0) {
        LOGD("failed to remove default route for %s: %s", ifname, strerror(errno));
    }
    if (ifc_set_addr(ifname, 0)) {
        printerr("failed to set ipaddr to 0 : %s\n", strerror(errno));
    }
    ifc_close();
    return result;
}

6. ifc_configure()

int
ifc_configure(const char *ifname,
        in_addr_t address,
        in_addr_t prefixLength,
        in_addr_t gateway,
        in_addr_t dns1,
        in_addr_t dns2) {

    char dns_prop_name[PROPERTY_KEY_MAX];

    ifc_init();

    if (ifc_up(ifname)) {
        printerr("failed to turn on interface %s: %s\n", ifname, strerror(errno));
        ifc_close();
        return -1;
    }
    if (ifc_set_addr(ifname, address)) {
        printerr("failed to set ipaddr %s: %s\n", ipaddr_to_string(address), strerror(errno));
        ifc_close();
        return -1;
    }
    if (ifc_set_prefixLength(ifname, prefixLength)) {
        printerr("failed to set prefixLength %d: %s\n", prefixLength, strerror(errno));
        ifc_close();
        return -1;
    }
    if (ifc_create_default_route(ifname, gateway)) {
        printerr("failed to set default route %s: %s\n", ipaddr_to_string(gateway), strerror(errno));
        ifc_close();
        return -1;
    }

    ifc_close();

    snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns1", ifname);
    property_set(dns_prop_name, dns1 ? ipaddr_to_string(dns1) : "");
    snprintf(dns_prop_name, sizeof(dns_prop_name), "net.%s.dns2", ifname);
    property_set(dns_prop_name, dns2 ? ipaddr_to_string(dns2) : "");

    return 0;
}