source: MondoRescue/branches/stable/mindi-busybox/networking/ifupdown.c@ 1770

/* vi: set sw=4 ts=4: */
/*
 *  ifupdown for busybox
 *  Copyright (c) 2002 Glenn McGrath <bug1@iinet.net.au>
 *  Copyright (c) 2003-2004 Erik Andersen <andersen@codepoet.org>
 *
 *  Based on ifupdown v 0.6.4 by Anthony Towns
 *  Copyright (c) 1999 Anthony Towns <aj@azure.humbug.org.au>
 *
 *  Changes to upstream version
 *  Remove checks for kernel version, assume kernel version 2.2.0 or better.
 *  Lines in the interfaces file cannot wrap.
 *  To adhere to the FHS, the default state file is /var/run/ifstate
 *  (defined via CONFIG_IFUPDOWN_IFSTATE_PATH) and can be overridden by build
 *  configuration.
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include <sys/utsname.h>
#include <fnmatch.h>
#include <getopt.h>

#include "libbb.h"

#define MAX_OPT_DEPTH 10
#define EUNBALBRACK 10001
#define EUNDEFVAR   10002
#define EUNBALPER   10000

#if ENABLE_FEATURE_IFUPDOWN_MAPPING
#define MAX_INTERFACE_LENGTH 10
#endif

#define debug_noise(args...) /*fprintf(stderr, args)*/

/* Forward declaration */
struct interface_defn_t;

typedef int execfn(char *command);

struct method_t {
    const char *name;
    int (*up)(struct interface_defn_t *ifd, execfn *e);
    int (*down)(struct interface_defn_t *ifd, execfn *e);
};

struct address_family_t {
    const char *name;
    int n_methods;
    const struct method_t *method;
};

struct mapping_defn_t {
    struct mapping_defn_t *next;

    int max_matches;
    int n_matches;
    char **match;

    char *script;

    int max_mappings;
    int n_mappings;
    char **mapping;
};

struct variable_t {
    char *name;
    char *value;
};

struct interface_defn_t {
    const struct address_family_t *address_family;
    const struct method_t *method;

    char *iface;
    int max_options;
    int n_options;
    struct variable_t *option;
};

struct interfaces_file_t {
    llist_t *autointerfaces;
    llist_t *ifaces;
    struct mapping_defn_t *mappings;
};

#define OPTION_STR "anvf" USE_FEATURE_IFUPDOWN_MAPPING("m") "i:"
enum {
    OPT_do_all = 0x1,
    OPT_no_act = 0x2,
    OPT_verbose = 0x4,
    OPT_force = 0x8,
    OPT_no_mappings = 0x10,
};
#define DO_ALL (option_mask32 & OPT_do_all)
#define NO_ACT (option_mask32 & OPT_no_act)
#define VERBOSE (option_mask32 & OPT_verbose)
#define FORCE (option_mask32 & OPT_force)
#define NO_MAPPINGS (option_mask32 & OPT_no_mappings)

static char **my_environ;

static const char *startup_PATH;

#if ENABLE_FEATURE_IFUPDOWN_IPV4 || ENABLE_FEATURE_IFUPDOWN_IPV6

static void addstr(char **bufp, const char *str, size_t str_length)
{
    /* xasprintf trick will be smaller, but we are often
     * called with str_length == 1 - don't want to have
     * THAT much of malloc/freeing! */
    char *buf = *bufp;
    int len = (buf ? strlen(buf) : 0);
    str_length++;
    buf = xrealloc(buf, len + str_length);
    /* copies at most str_length-1 chars! */
    safe_strncpy(buf + len, str, str_length);
    *bufp = buf;
}

static int strncmpz(const char *l, const char *r, size_t llen)
{
    int i = strncmp(l, r, llen);

    if (i == 0)
        return -r[llen];
    return i;
}

static char *get_var(const char *id, size_t idlen, struct interface_defn_t *ifd)
{
    int i;

    if (strncmpz(id, "iface", idlen) == 0) {
        char *result;
        static char label_buf[20];
        safe_strncpy(label_buf, ifd->iface, sizeof(label_buf));
        result = strchr(label_buf, ':');
        if (result) {
            *result = '\0';
        }
        return label_buf;
    }
    if (strncmpz(id, "label", idlen) == 0) {
        return ifd->iface;
    }
    for (i = 0; i < ifd->n_options; i++) {
        if (strncmpz(id, ifd->option[i].name, idlen) == 0) {
            return ifd->option[i].value;
        }
    }
    return NULL;
}

#if ENABLE_FEATURE_IFUPDOWN_IP
static int count_netmask_bits(const char *dotted_quad)
{
//  int result;
//  unsigned a, b, c, d;
//  /* Found a netmask...  Check if it is dotted quad */
//  if (sscanf(dotted_quad, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
//      return -1;
//  if ((a|b|c|d) >> 8)
//      return -1; /* one of numbers is >= 256 */
//  d |= (a << 24) | (b << 16) | (c << 8); /* IP */
//  d = ~d; /* 11110000 -> 00001111 */

    /* Shorter version */
    int result;
    struct in_addr ip;
    unsigned d;

    if (inet_aton(dotted_quad, &ip) == 0)
        return -1; /* malformed dotted IP */
    d = ntohl(ip.s_addr); /* IP in host order */
    d = ~d; /* 11110000 -> 00001111 */
    if (d & (d+1)) /* check that it is in 00001111 form */
        return -1; /* no it is not */
    result = 32;
    while (d) {
        d >>= 1;
        result--;
    }
    return result;
}
#endif

static char *parse(const char *command, struct interface_defn_t *ifd)
{
    size_t old_pos[MAX_OPT_DEPTH] = { 0 };
    int okay[MAX_OPT_DEPTH] = { 1 };
    int opt_depth = 1;
    char *result = NULL;

    while (*command) {
        switch (*command) {
        default:
            addstr(&result, command, 1);
            command++;
            break;
        case '\\':
            if (command[1]) {
                addstr(&result, command + 1, 1);
                command += 2;
            } else {
                addstr(&result, command, 1);
                command++;
            }
            break;
        case '[':
            if (command[1] == '[' && opt_depth < MAX_OPT_DEPTH) {
                old_pos[opt_depth] = result ? strlen(result) : 0;
                okay[opt_depth] = 1;
                opt_depth++;
                command += 2;
            } else {
                addstr(&result, "[", 1);
                command++;
            }
            break;
        case ']':
            if (command[1] == ']' && opt_depth > 1) {
                opt_depth--;
                if (!okay[opt_depth]) {
                    result[old_pos[opt_depth]] = '\0';
                }
                command += 2;
            } else {
                addstr(&result, "]", 1);
                command++;
            }
            break;
        case '%':
            {
                char *nextpercent;
                char *varvalue;

                command++;
                nextpercent = strchr(command, '%');
                if (!nextpercent) {
                    errno = EUNBALPER;
                    free(result);
                    return NULL;
                }

                varvalue = get_var(command, nextpercent - command, ifd);

                if (varvalue) {
                    addstr(&result, varvalue, strlen(varvalue));
                } else {
#if ENABLE_FEATURE_IFUPDOWN_IP
                    /* Sigh...  Add a special case for 'ip' to convert from
                     * dotted quad to bit count style netmasks.  */
                    if (strncmp(command, "bnmask", 6) == 0) {
                        unsigned res;
                        varvalue = get_var("netmask", 7, ifd);
                        if (varvalue) {
                            res = count_netmask_bits(varvalue);
                            if (res > 0) {
                                const char *argument = utoa(res);
                                addstr(&result, argument, strlen(argument));
                                command = nextpercent + 1;
                                break;
                            }
                        }
                    }
#endif
                    okay[opt_depth - 1] = 0;
                }

                command = nextpercent + 1;
            }
            break;
        }
    }

    if (opt_depth > 1) {
        errno = EUNBALBRACK;
        free(result);
        return NULL;
    }

    if (!okay[0]) {
        errno = EUNDEFVAR;
        free(result);
        return NULL;
    }

    return result;
}

/* execute() returns 1 for success and 0 for failure */
static int execute(const char *command, struct interface_defn_t *ifd, execfn *exec)
{
    char *out;
    int ret;

    out = parse(command, ifd);
    if (!out) {
        /* parse error? */
        return 0;
    }
    /* out == "": parsed ok but not all needed variables known, skip */
    ret = out[0] ? (*exec)(out) : 1;

    free(out);
    if (ret != 1) {
        return 0;
    }
    return 1;
}
#endif

#if ENABLE_FEATURE_IFUPDOWN_IPV6
static int loopback_up6(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_IP
    int result;
    result = execute("ip addr add ::1 dev %iface%", ifd, exec);
    result += execute("ip link set %iface% up", ifd, exec);
    return ((result == 2) ? 2 : 0);
#else
    return execute("ifconfig %iface% add ::1", ifd, exec);
#endif
}

static int loopback_down6(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_IP
    return execute("ip link set %iface% down", ifd, exec);
#else
    return execute("ifconfig %iface% del ::1", ifd, exec);
#endif
}

static int static_up6(struct interface_defn_t *ifd, execfn *exec)
{
    int result;
#if ENABLE_FEATURE_IFUPDOWN_IP
    result = execute("ip addr add %address%/%netmask% dev %iface%[[ label %label%]]", ifd, exec);
    result += execute("ip link set[[ mtu %mtu%]][[ address %hwaddress%]] %iface% up", ifd, exec);
    /* Was: "[[ ip ....%gateway% ]]". Removed extra spaces w/o checking */
    result += execute("[[ip route add ::/0 via %gateway%]]", ifd, exec);
#else
    result = execute("ifconfig %iface%[[ media %media%]][[ hw %hwaddress%]][[ mtu %mtu%]] up", ifd, exec);
    result += execute("ifconfig %iface% add %address%/%netmask%", ifd, exec);
    result += execute("[[route -A inet6 add ::/0 gw %gateway%]]", ifd, exec);
#endif
    return ((result == 3) ? 3 : 0);
}

static int static_down6(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_IP
    return execute("ip link set %iface% down", ifd, exec);
#else
    return execute("ifconfig %iface% down", ifd, exec);
#endif
}

#if ENABLE_FEATURE_IFUPDOWN_IP
static int v4tunnel_up(struct interface_defn_t *ifd, execfn *exec)
{
    int result;
    result = execute("ip tunnel add %iface% mode sit remote "
            "%endpoint%[[ local %local%]][[ ttl %ttl%]]", ifd, exec);
    result += execute("ip link set %iface% up", ifd, exec);
    result += execute("ip addr add %address%/%netmask% dev %iface%", ifd, exec);
    result += execute("[[ip route add ::/0 via %gateway%]]", ifd, exec);
    return ((result == 4) ? 4 : 0);
}

static int v4tunnel_down(struct interface_defn_t * ifd, execfn * exec)
{
    return execute("ip tunnel del %iface%", ifd, exec);
}
#endif

static const struct method_t methods6[] = {
#if ENABLE_FEATURE_IFUPDOWN_IP
    { "v4tunnel", v4tunnel_up, v4tunnel_down, },
#endif
    { "static", static_up6, static_down6, },
    { "loopback", loopback_up6, loopback_down6, },
};

static const struct address_family_t addr_inet6 = {
    "inet6",
    ARRAY_SIZE(methods6),
    methods6
};
#endif /* FEATURE_IFUPDOWN_IPV6 */

#if ENABLE_FEATURE_IFUPDOWN_IPV4
static int loopback_up(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_IP
    int result;
    result = execute("ip addr add 127.0.0.1/8 dev %iface%", ifd, exec);
    result += execute("ip link set %iface% up", ifd, exec);
    return ((result == 2) ? 2 : 0);
#else
    return execute("ifconfig %iface% 127.0.0.1 up", ifd, exec);
#endif
}

static int loopback_down(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_IP
    int result;
    result = execute("ip addr flush dev %iface%", ifd, exec);
    result += execute("ip link set %iface% down", ifd, exec);
    return ((result == 2) ? 2 : 0);
#else
    return execute("ifconfig %iface% 127.0.0.1 down", ifd, exec);
#endif
}

static int static_up(struct interface_defn_t *ifd, execfn *exec)
{
    int result;
#if ENABLE_FEATURE_IFUPDOWN_IP
    result = execute("ip addr add %address%/%bnmask%[[ broadcast %broadcast%]] "
            "dev %iface%[[ peer %pointopoint%]][[ label %label%]]", ifd, exec);
    result += execute("ip link set[[ mtu %mtu%]][[ address %hwaddress%]] %iface% up", ifd, exec);
    result += execute("[[ip route add default via %gateway% dev %iface%]]", ifd, exec);
    return ((result == 3) ? 3 : 0);
#else
    /* ifconfig said to set iface up before it processes hw %hwaddress%,
     * which then of course fails. Thus we run two separate ifconfig */
    result = execute("ifconfig %iface%[[ hw %hwaddress%]][[ media %media%]][[ mtu %mtu%]] up",
                ifd, exec);
    result += execute("ifconfig %iface% %address% netmask %netmask%"
                "[[ broadcast %broadcast%]][[ pointopoint %pointopoint%]] ",
                ifd, exec);
    result += execute("[[route add default gw %gateway% %iface%]]", ifd, exec);
    return ((result == 3) ? 3 : 0);
#endif
}

static int static_down(struct interface_defn_t *ifd, execfn *exec)
{
    int result;
#if ENABLE_FEATURE_IFUPDOWN_IP
    result = execute("ip addr flush dev %iface%", ifd, exec);
    result += execute("ip link set %iface% down", ifd, exec);
#else
    result = execute("[[route del default gw %gateway% %iface%]]", ifd, exec);
    result += execute("ifconfig %iface% down", ifd, exec);
#endif
    return ((result == 2) ? 2 : 0);
}

#if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
struct dhcp_client_t
{
    const char *name;
    const char *startcmd;
    const char *stopcmd;
};

static const struct dhcp_client_t ext_dhcp_clients[] = {
    { "dhcpcd",
        "dhcpcd[[ -h %hostname%]][[ -i %vendor%]][[ -I %clientid%]][[ -l %leasetime%]] %iface%",
        "dhcpcd -k %iface%",
    },
    { "dhclient",
        "dhclient -pf /var/run/dhclient.%iface%.pid %iface%",
        "kill -9 `cat /var/run/dhclient.%iface%.pid` 2>/dev/null",
    },
    { "pump",
        "pump -i %iface%[[ -h %hostname%]][[ -l %leasehours%]]",
        "pump -i %iface% -k",
    },
    { "udhcpc",
        "udhcpc -R -n -p /var/run/udhcpc.%iface%.pid -i %iface%[[ -H %hostname%]][[ -c %clientid%]][[ -s %script%]]",
        "kill `cat /var/run/udhcpc.%iface%.pid` 2>/dev/null",
    },
};
#endif /* ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCPC */

static int dhcp_up(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
    int i;
#if ENABLE_FEATURE_IFUPDOWN_IP
    /* ip doesn't up iface when it configures it (unlike ifconfig) */
    if (!execute("ip link set %iface% up", ifd, exec))
        return 0;
#endif
    for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) {
        if (exists_execable(ext_dhcp_clients[i].name))
            return execute(ext_dhcp_clients[i].startcmd, ifd, exec);
    }
    bb_error_msg("no dhcp clients found");
    return 0;
#elif ENABLE_APP_UDHCPC
#if ENABLE_FEATURE_IFUPDOWN_IP
    /* ip doesn't up iface when it configures it (unlike ifconfig) */
    if (!execute("ip link set %iface% up", ifd, exec))
        return 0;
#endif
    return execute("udhcpc -R -n -p /var/run/udhcpc.%iface%.pid "
            "-i %iface%[[ -H %hostname%]][[ -c %clientid%]][[ -s %script%]]",
            ifd, exec);
#else
    return 0; /* no dhcp support */
#endif
}

static int dhcp_down(struct interface_defn_t *ifd, execfn *exec)
{
#if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
    int i;
    for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) {
        if (exists_execable(ext_dhcp_clients[i].name))
            return execute(ext_dhcp_clients[i].stopcmd, ifd, exec);
    }
    bb_error_msg("no dhcp clients found, using static interface shutdown");
    return static_down(ifd, exec);
#elif ENABLE_APP_UDHCPC
    return execute("kill "
                   "`cat /var/run/udhcpc.%iface%.pid` 2>/dev/null", ifd, exec);
#else
    return 0; /* no dhcp support */
#endif
}

static int manual_up_down(struct interface_defn_t *ifd, execfn *exec)
{
    return 1;
}

static int bootp_up(struct interface_defn_t *ifd, execfn *exec)
{
    return execute("bootpc[[ --bootfile %bootfile%]] --dev %iface%"
            "[[ --server %server%]][[ --hwaddr %hwaddr%]]"
            " --returniffail --serverbcast", ifd, exec);
}

static int ppp_up(struct interface_defn_t *ifd, execfn *exec)
{
    return execute("pon[[ %provider%]]", ifd, exec);
}

static int ppp_down(struct interface_defn_t *ifd, execfn *exec)
{
    return execute("poff[[ %provider%]]", ifd, exec);
}

static int wvdial_up(struct interface_defn_t *ifd, execfn *exec)
{
    return execute("start-stop-daemon --start -x wvdial "
        "-p /var/run/wvdial.%iface% -b -m --[[ %provider%]]", ifd, exec);
}

static int wvdial_down(struct interface_defn_t *ifd, execfn *exec)
{
    return execute("start-stop-daemon --stop -x wvdial "
            "-p /var/run/wvdial.%iface% -s 2", ifd, exec);
}

static const struct method_t methods[] = {
    { "manual", manual_up_down, manual_up_down, },
    { "wvdial", wvdial_up, wvdial_down, },
    { "ppp", ppp_up, ppp_down, },
    { "static", static_up, static_down, },
    { "bootp", bootp_up, static_down, },
    { "dhcp", dhcp_up, dhcp_down, },
    { "loopback", loopback_up, loopback_down, },
};

static const struct address_family_t addr_inet = {
    "inet",
    ARRAY_SIZE(methods),
    methods
};

#endif  /* if ENABLE_FEATURE_IFUPDOWN_IPV4 */

static char *next_word(char **buf)
{
    unsigned short length;
    char *word;

    if (!buf || !*buf || !**buf) {
        return NULL;
    }

    /* Skip over leading whitespace */
    word = skip_whitespace(*buf);

    /* Skip over comments */
    if (*word == '#') {
        return NULL;
    }

    /* Find the length of this word */
    length = strcspn(word, " \t\n");
    if (length == 0) {
        return NULL;
    }
    *buf = word + length;
    /*DBU:[dave@cray.com] if we are already at EOL dont't increment beyond it */
    if (**buf) {
        **buf = '\0';
        (*buf)++;
    }

    return word;
}

static const struct address_family_t *get_address_family(const struct address_family_t *const af[], char *name)
{
    int i;

    if (!name)
        return NULL;

    for (i = 0; af[i]; i++) {
        if (strcmp(af[i]->name, name) == 0) {
            return af[i];
        }
    }
    return NULL;
}

static const struct method_t *get_method(const struct address_family_t *af, char *name)
{
    int i;

    if (!name)
        return NULL;

    for (i = 0; i < af->n_methods; i++) {
        if (strcmp(af->method[i].name, name) == 0) {
            return &af->method[i];
        }
    }
    return NULL;
}

static const llist_t *find_list_string(const llist_t *list, const char *string)
{
    if (string == NULL)
        return NULL;

    while (list) {
        if (strcmp(list->data, string) == 0) {
            return list;
        }
        list = list->link;
    }
    return NULL;
}

static struct interfaces_file_t *read_interfaces(const char *filename)
{
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
    struct mapping_defn_t *currmap = NULL;
#endif
    struct interface_defn_t *currif = NULL;
    struct interfaces_file_t *defn;
    FILE *f;
    char *firstword;
    char *buf;

    enum { NONE, IFACE, MAPPING } currently_processing = NONE;

    defn = xzalloc(sizeof(struct interfaces_file_t));

    f = xfopen(filename, "r");

    while ((buf = xmalloc_getline(f)) != NULL) {
        char *buf_ptr = buf;

        firstword = next_word(&buf_ptr);
        if (firstword == NULL) {
            free(buf);
            continue;   /* blank line */
        }

        if (strcmp(firstword, "mapping") == 0) {
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
            currmap = xzalloc(sizeof(struct mapping_defn_t));

            while ((firstword = next_word(&buf_ptr)) != NULL) {
                if (currmap->max_matches == currmap->n_matches) {
                    currmap->max_matches = currmap->max_matches * 2 + 1;
                    currmap->match = xrealloc(currmap->match, sizeof(currmap->match) * currmap->max_matches);
                }

                currmap->match[currmap->n_matches++] = xstrdup(firstword);
            }
            currmap->max_mappings = 0;
            currmap->n_mappings = 0;
            currmap->mapping = NULL;
            currmap->script = NULL;
            {
                struct mapping_defn_t **where = &defn->mappings;
                while (*where != NULL) {
                    where = &(*where)->next;
                }
                *where = currmap;
                currmap->next = NULL;
            }
            debug_noise("Added mapping\n");
#endif
            currently_processing = MAPPING;
        } else if (strcmp(firstword, "iface") == 0) {
            static const struct address_family_t *const addr_fams[] = {
#if ENABLE_FEATURE_IFUPDOWN_IPV4
                &addr_inet,
#endif
#if ENABLE_FEATURE_IFUPDOWN_IPV6
                &addr_inet6,
#endif
                NULL
            };

            char *iface_name;
            char *address_family_name;
            char *method_name;
            llist_t *iface_list;

            currif = xzalloc(sizeof(struct interface_defn_t));
            iface_name = next_word(&buf_ptr);
            address_family_name = next_word(&buf_ptr);
            method_name = next_word(&buf_ptr);

            if (buf_ptr == NULL) {
                bb_error_msg("too few parameters for line \"%s\"", buf);
                return NULL;
            }

            /* ship any trailing whitespace */
            buf_ptr = skip_whitespace(buf_ptr);

            if (buf_ptr[0] != '\0') {
                bb_error_msg("too many parameters \"%s\"", buf);
                return NULL;
            }

            currif->iface = xstrdup(iface_name);

            currif->address_family = get_address_family(addr_fams, address_family_name);
            if (!currif->address_family) {
                bb_error_msg("unknown address type \"%s\"", address_family_name);
                return NULL;
            }

            currif->method = get_method(currif->address_family, method_name);
            if (!currif->method) {
                bb_error_msg("unknown method \"%s\"", method_name);
                return NULL;
            }

            for (iface_list = defn->ifaces; iface_list; iface_list = iface_list->link) {
                struct interface_defn_t *tmp = (struct interface_defn_t *) iface_list->data;
                if ((strcmp(tmp->iface, currif->iface) == 0) &&
                    (tmp->address_family == currif->address_family)) {
                    bb_error_msg("duplicate interface \"%s\"", tmp->iface);
                    return NULL;
                }
            }
            llist_add_to_end(&(defn->ifaces), (char*)currif);

            debug_noise("iface %s %s %s\n", currif->iface, address_family_name, method_name);
            currently_processing = IFACE;
        } else if (strcmp(firstword, "auto") == 0) {
            while ((firstword = next_word(&buf_ptr)) != NULL) {

                /* Check the interface isnt already listed */
                if (find_list_string(defn->autointerfaces, firstword)) {
                    bb_perror_msg_and_die("interface declared auto twice \"%s\"", buf);
                }

                /* Add the interface to the list */
                llist_add_to_end(&(defn->autointerfaces), xstrdup(firstword));
                debug_noise("\nauto %s\n", firstword);
            }
            currently_processing = NONE;
        } else {
            switch (currently_processing) {
            case IFACE:
                {
                    int i;

                    if (strlen(buf_ptr) == 0) {
                        bb_error_msg("option with empty value \"%s\"", buf);
                        return NULL;
                    }

                    if (strcmp(firstword, "up") != 0
                            && strcmp(firstword, "down") != 0
                            && strcmp(firstword, "pre-up") != 0
                            && strcmp(firstword, "post-down") != 0) {
                        for (i = 0; i < currif->n_options; i++) {
                            if (strcmp(currif->option[i].name, firstword) == 0) {
                                bb_error_msg("duplicate option \"%s\"", buf);
                                return NULL;
                            }
                        }
                    }
                }
                if (currif->n_options >= currif->max_options) {
                    struct variable_t *opt;

                    currif->max_options = currif->max_options + 10;
                    opt = xrealloc(currif->option, sizeof(*opt) * currif->max_options);
                    currif->option = opt;
                }
                currif->option[currif->n_options].name = xstrdup(firstword);
                currif->option[currif->n_options].value = xstrdup(buf_ptr);
                if (!currif->option[currif->n_options].name) {
                    perror(filename);
                    return NULL;
                }
                if (!currif->option[currif->n_options].value) {
                    perror(filename);
                    return NULL;
                }
                debug_noise("\t%s=%s\n", currif->option[currif->n_options].name,
                        currif->option[currif->n_options].value);
                currif->n_options++;
                break;
            case MAPPING:
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
                if (strcmp(firstword, "script") == 0) {
                    if (currmap->script != NULL) {
                        bb_error_msg("duplicate script in mapping \"%s\"", buf);
                        return NULL;
                    } else {
                        currmap->script = xstrdup(next_word(&buf_ptr));
                    }
                } else if (strcmp(firstword, "map") == 0) {
                    if (currmap->max_mappings == currmap->n_mappings) {
                        currmap->max_mappings = currmap->max_mappings * 2 + 1;
                        currmap->mapping = xrealloc(currmap->mapping, sizeof(char *) * currmap->max_mappings);
                    }
                    currmap->mapping[currmap->n_mappings] = xstrdup(next_word(&buf_ptr));
                    currmap->n_mappings++;
                } else {
                    bb_error_msg("misplaced option \"%s\"", buf);
                    return NULL;
                }
#endif
                break;
            case NONE:
            default:
                bb_error_msg("misplaced option \"%s\"", buf);
                return NULL;
            }
        }
        free(buf);
    }
    if (ferror(f) != 0) {
        /* ferror does NOT set errno! */
        bb_error_msg_and_die("%s: I/O error", filename);
    }
    fclose(f);

    return defn;
}

static char *setlocalenv(const char *format, const char *name, const char *value)
{
    char *result;
    char *here;
    char *there;

    result = xasprintf(format, name, value);

    for (here = there = result; *there != '=' && *there; there++) {
        if (*there == '-')
            *there = '_';
        if (isalpha(*there))
            *there = toupper(*there);

        if (isalnum(*there) || *there == '_') {
            *here = *there;
            here++;
        }
    }
    memmove(here, there, strlen(there) + 1);

    return result;
}

static void set_environ(struct interface_defn_t *iface, const char *mode)
{
    char **environend;
    int i;
    const int n_env_entries = iface->n_options + 5;
    char **ppch;

    if (my_environ != NULL) {
        for (ppch = my_environ; *ppch; ppch++) {
            free(*ppch);
            *ppch = NULL;
        }
        free(my_environ);
    }
    my_environ = xzalloc(sizeof(char *) * (n_env_entries + 1 /* for final NULL */ ));
    environend = my_environ;

    for (i = 0; i < iface->n_options; i++) {
        if (strcmp(iface->option[i].name, "up") == 0
         || strcmp(iface->option[i].name, "down") == 0
         || strcmp(iface->option[i].name, "pre-up") == 0
         || strcmp(iface->option[i].name, "post-down") == 0
        ) {
            continue;
        }
        *(environend++) = setlocalenv("IF_%s=%s", iface->option[i].name, iface->option[i].value);
    }

    *(environend++) = setlocalenv("%s=%s", "IFACE", iface->iface);
    *(environend++) = setlocalenv("%s=%s", "ADDRFAM", iface->address_family->name);
    *(environend++) = setlocalenv("%s=%s", "METHOD", iface->method->name);
    *(environend++) = setlocalenv("%s=%s", "MODE", mode);
    *(environend++) = setlocalenv("%s=%s", "PATH", startup_PATH);
}

static int doit(char *str)
{
    if (option_mask32 & (OPT_no_act|OPT_verbose)) {
        puts(str);
    }
    if (!(option_mask32 & OPT_no_act)) {
        pid_t child;
        int status;

        fflush(NULL);
        child = fork();
        switch (child) {
        case -1: /* failure */
            return 0;
        case 0: /* child */
            execle(DEFAULT_SHELL, DEFAULT_SHELL, "-c", str, NULL, my_environ);
            exit(127);
        }
        waitpid(child, &status, 0);
        if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
            return 0;
        }
    }
    return 1;
}

static int execute_all(struct interface_defn_t *ifd, const char *opt)
{
    int i;
    char *buf;
    for (i = 0; i < ifd->n_options; i++) {
        if (strcmp(ifd->option[i].name, opt) == 0) {
            if (!doit(ifd->option[i].value)) {
                return 0;
            }
        }
    }

    buf = xasprintf("run-parts /etc/network/if-%s.d", opt);
    /* heh, we don't bother free'ing it */
    return doit(buf);
}

static int check(char *str)
{
    return str != NULL;
}

static int iface_up(struct interface_defn_t *iface)
{
    if (!iface->method->up(iface, check)) return -1;
    set_environ(iface, "start");
    if (!execute_all(iface, "pre-up")) return 0;
    if (!iface->method->up(iface, doit)) return 0;
    if (!execute_all(iface, "up")) return 0;
    return 1;
}

static int iface_down(struct interface_defn_t *iface)
{
    if (!iface->method->down(iface,check)) return -1;
    set_environ(iface, "stop");
    if (!execute_all(iface, "down")) return 0;
    if (!iface->method->down(iface, doit)) return 0;
    if (!execute_all(iface, "post-down")) return 0;
    return 1;
}

#if ENABLE_FEATURE_IFUPDOWN_MAPPING
static int popen2(FILE **in, FILE **out, char *command, ...)
{
    va_list ap;
    char *argv[11] = { command };
    int argc;
    int infd[2], outfd[2];
    pid_t pid;

    argc = 1;
    va_start(ap, command);
    while ((argc < 10) && (argv[argc] = va_arg(ap, char *))) {
        argc++;
    }
    argv[argc] = NULL;  /* make sure */
    va_end(ap);

    if (pipe(infd) != 0) {
        return 0;
    }

    if (pipe(outfd) != 0) {
        close(infd[0]);
        close(infd[1]);
        return 0;
    }

    fflush(NULL);
    switch (pid = fork()) {
    case -1:            /* failure */
        close(infd[0]);
        close(infd[1]);
        close(outfd[0]);
        close(outfd[1]);
        return 0;
    case 0:         /* child */
        dup2(infd[0], 0);
        dup2(outfd[1], 1);
        close(infd[0]);
        close(infd[1]);
        close(outfd[0]);
        close(outfd[1]);
        BB_EXECVP(command, argv);
        exit(127);
    default:            /* parent */
        *in = fdopen(infd[1], "w");
        *out = fdopen(outfd[0], "r");
        close(infd[0]);
        close(outfd[1]);
        return pid;
    }
    /* unreached */
}

static char *run_mapping(char *physical, struct mapping_defn_t * map)
{
    FILE *in, *out;
    int i, status;
    pid_t pid;

    char *logical = xstrdup(physical);

    /* Run the mapping script. */
    pid = popen2(&in, &out, map->script, physical, NULL);

    /* popen2() returns 0 on failure. */
    if (pid == 0)
        return logical;

    /* Write mappings to stdin of mapping script. */
    for (i = 0; i < map->n_mappings; i++) {
        fprintf(in, "%s\n", map->mapping[i]);
    }
    fclose(in);
    waitpid(pid, &status, 0);

    if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
        /* If the mapping script exited successfully, try to
         * grab a line of output and use that as the name of the
         * logical interface. */
        char *new_logical = xmalloc(MAX_INTERFACE_LENGTH);

        if (fgets(new_logical, MAX_INTERFACE_LENGTH, out)) {
            /* If we are able to read a line of output from the script,
             * remove any trailing whitespace and use this value
             * as the name of the logical interface. */
            char *pch = new_logical + strlen(new_logical) - 1;

            while (pch >= new_logical && isspace(*pch))
                *(pch--) = '\0';

            free(logical);
            logical = new_logical;
        } else {
            /* If we are UNABLE to read a line of output, discard our
             * freshly allocated memory. */
            free(new_logical);
        }
    }

    fclose(out);

    return logical;
}
#endif /* FEATURE_IFUPDOWN_MAPPING */

static llist_t *find_iface_state(llist_t *state_list, const char *iface)
{
    unsigned short iface_len = strlen(iface);
    llist_t *search = state_list;

    while (search) {
        if ((strncmp(search->data, iface, iface_len) == 0)
         && (search->data[iface_len] == '=')) {
            return search;
        }
        search = search->link;
    }
    return NULL;
}

/* read the previous state from the state file */
static llist_t *read_iface_state(void)
{
    llist_t *state_list = NULL;
    FILE *state_fp = fopen(CONFIG_IFUPDOWN_IFSTATE_PATH, "r");

    if (state_fp) {
        char *start, *end_ptr;
        while ((start = xmalloc_fgets(state_fp)) != NULL) {
            /* We should only need to check for a single character */
            end_ptr = start + strcspn(start, " \t\n");
            *end_ptr = '\0';
            llist_add_to(&state_list, start);
        }
        fclose(state_fp);
    }
    return state_list;
}


int ifupdown_main(int argc, char **argv);
int ifupdown_main(int argc, char **argv)
{
    int (*cmds)(struct interface_defn_t *) = NULL;
    struct interfaces_file_t *defn;
    llist_t *target_list = NULL;
    const char *interfaces = "/etc/network/interfaces";
    bool any_failures = 0;

    cmds = iface_down;
    if (applet_name[2] == 'u') {
        /* ifup command */
        cmds = iface_up;
    }

    getopt32(argv, OPTION_STR, &interfaces);
    if (argc - optind > 0) {
        if (DO_ALL) bb_show_usage();
    } else {
        if (!DO_ALL) bb_show_usage();
    }

    debug_noise("reading %s file:\n", interfaces);
    defn = read_interfaces(interfaces);
    debug_noise("\ndone reading %s\n\n", interfaces);

    if (!defn) {
        return EXIT_FAILURE;
    }

    startup_PATH = getenv("PATH");
    if (!startup_PATH) startup_PATH = "";

    /* Create a list of interfaces to work on */
    if (DO_ALL) {
        target_list = defn->autointerfaces;
    } else {
        llist_add_to_end(&target_list, argv[optind]);
    }

    /* Update the interfaces */
    while (target_list) {
        llist_t *iface_list;
        struct interface_defn_t *currif;
        char *iface;
        char *liface;
        char *pch;
        bool okay = 0;
        unsigned cmds_ret;

        iface = xstrdup(target_list->data);
        target_list = target_list->link;

        pch = strchr(iface, '=');
        if (pch) {
            *pch = '\0';
            liface = xstrdup(pch + 1);
        } else {
            liface = xstrdup(iface);
        }

        if (!FORCE) {
            llist_t *state_list = read_iface_state();
            const llist_t *iface_state = find_iface_state(state_list, iface);

            if (cmds == iface_up) {
                /* ifup */
                if (iface_state) {
                    bb_error_msg("interface %s already configured", iface);
                    continue;
                }
            } else {
                /* ifdown */
                if (!iface_state) {
                    bb_error_msg("interface %s not configured", iface);
                    continue;
                }
            }
            llist_free(state_list, free);
        }

#if ENABLE_FEATURE_IFUPDOWN_MAPPING
        if ((cmds == iface_up) && !NO_MAPPINGS) {
            struct mapping_defn_t *currmap;

            for (currmap = defn->mappings; currmap; currmap = currmap->next) {
                int i;
                for (i = 0; i < currmap->n_matches; i++) {
                    if (fnmatch(currmap->match[i], liface, 0) != 0)
                        continue;
                    if (VERBOSE) {
                        printf("Running mapping script %s on %s\n", currmap->script, liface);
                    }
                    liface = run_mapping(iface, currmap);
                    break;
                }
            }
        }
#endif

        iface_list = defn->ifaces;
        while (iface_list) {
            currif = (struct interface_defn_t *) iface_list->data;
            if (strcmp(liface, currif->iface) == 0) {
                char *oldiface = currif->iface;

                okay = 1;
                currif->iface = iface;

                debug_noise("\nConfiguring interface %s (%s)\n", liface, currif->address_family->name);

                /* Call the cmds function pointer, does either iface_up() or iface_down() */
                cmds_ret = cmds(currif);
                if (cmds_ret == -1) {
                    bb_error_msg("don't seem to have all the variables for %s/%s",
                            liface, currif->address_family->name);
                    any_failures = 1;
                } else if (cmds_ret == 0) {
                    any_failures = 1;
                }

                currif->iface = oldiface;
            }
            iface_list = iface_list->link;
        }
        if (VERBOSE) {
            puts("");
        }

        if (!okay && !FORCE) {
            bb_error_msg("ignoring unknown interface %s", liface);
            any_failures = 1;
        } else if (!NO_ACT) {
            /* update the state file */
            FILE *state_fp;
            llist_t *state;
            llist_t *state_list = read_iface_state();
            llist_t *iface_state = find_iface_state(state_list, iface);

            if (cmds == iface_up) {
                char * const newiface = xasprintf("%s=%s", iface, liface);
                if (iface_state == NULL) {
                    llist_add_to_end(&state_list, newiface);
                } else {
                    free(iface_state->data);
                    iface_state->data = newiface;
                }
            } else {
                /* Remove an interface from state_list */
                llist_unlink(&state_list, iface_state);
                free(llist_pop(&iface_state));
            }

            /* Actually write the new state */
            state_fp = xfopen(CONFIG_IFUPDOWN_IFSTATE_PATH, "w");
            state = state_list;
            while (state) {
                if (state->data) {
                    fprintf(state_fp, "%s\n", state->data);
                }
                state = state->link;
            }
            fclose(state_fp);
            llist_free(state_list, free);
        }
    }

    return any_failures;
}