/* vi: set sw=4 ts=4: */
/*
 *  ifupdown for busybox
 *  Copyright (c) 2002 Glenn McGrath
 *  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 GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"
/* After libbb.h, since it needs sys/types.h on some systems */
#include <sys/utsname.h>
#include <fnmatch.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 UDHCPC_CMD_OPTIONS CONFIG_IFUPDOWN_UDHCPC_CMD_OPTIONS

#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) FAST_FUNC;
        int (*down)(struct interface_defn_t *ifd, execfn *e) FAST_FUNC;
};

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" IF_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)


struct globals {
        char **my_environ;
        const char *startup_PATH;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define INIT_G() do { } while (0)


#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 - (unsigned char)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) {
                // ubuntu's ifup doesn't do this:
                //static char *label_buf;
                //char *result;
                //free(label_buf);
                //label_buf = xstrdup(ifd->iface);
                // Remove virtual iface suffix
                //result = strchrnul(label_buf, ':');
                //*result = '\0';
                //return label_buf;

                return ifd->iface;
        }
        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) {
# if ENABLE_FEATURE_IFUPDOWN_IP
                                        /* "hwaddress <class> <address>":
                                         * unlike ifconfig, ip doesnt want <class>
                                         * (usually "ether" keyword). Skip it. */
                                        if (strncmp(command, "hwaddress", 9) == 0) {
                                                varvalue = skip_whitespace(skip_non_whitespace(varvalue));
                                        }
# endif
                                        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 /* FEATURE_IFUPDOWN_IPV4 || FEATURE_IFUPDOWN_IPV6 */


#if ENABLE_FEATURE_IFUPDOWN_IPV6

static int FAST_FUNC 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 FAST_FUNC 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 FAST_FUNC manual_up_down6(struct interface_defn_t *ifd UNUSED_PARAM, execfn *exec UNUSED_PARAM)
{
        return 1;
}

static int FAST_FUNC 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%]][[ addr %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 FAST_FUNC 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 FAST_FUNC 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 FAST_FUNC 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    , },
        { "manual"   , manual_up_down6 , manual_up_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 FAST_FUNC 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 FAST_FUNC 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 FAST_FUNC 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%]][[ addr %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 FAST_FUNC 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); */
        /* Bringing the interface down deletes the routes in itself.
           Otherwise this fails if we reference 'gateway' when using this from dhcp_down */
        result = 1;
        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 %client%]][[ -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 " UDHCPC_CMD_OPTIONS " -p /var/run/udhcpc.%iface%.pid -i %iface%[[ -H %hostname%]][[ -c %client%]]"
                                "[[ -s %script%]][[ %udhcpc_opts%]]",
                "kill `cat /var/run/udhcpc.%iface%.pid` 2>/dev/null",
        },
};
# endif /* FEATURE_IFUPDOWN_EXTERNAL_DHCPC */

# if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
static int FAST_FUNC dhcp_up(struct interface_defn_t *ifd, execfn *exec)
{
        unsigned i;
#  if ENABLE_FEATURE_IFUPDOWN_IP
        /* ip doesn't up iface when it configures it (unlike ifconfig) */
        if (!execute("ip link set[[ addr %hwaddress%]] %iface% up", ifd, exec))
                return 0;
#  else
        /* needed if we have hwaddress on dhcp iface */
        if (!execute("ifconfig %iface%[[ hw %hwaddress%]] 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_UDHCPC
static int FAST_FUNC dhcp_up(struct interface_defn_t *ifd, execfn *exec)
{
#  if ENABLE_FEATURE_IFUPDOWN_IP
        /* ip doesn't up iface when it configures it (unlike ifconfig) */
        if (!execute("ip link set[[ addr %hwaddress%]] %iface% up", ifd, exec))
                return 0;
#  else
        /* needed if we have hwaddress on dhcp iface */
        if (!execute("ifconfig %iface%[[ hw %hwaddress%]] up", ifd, exec))
                return 0;
#  endif
        return execute("udhcpc " UDHCPC_CMD_OPTIONS " -p /var/run/udhcpc.%iface%.pid "
                        "-i %iface%[[ -H %hostname%]][[ -c %client%]][[ -s %script%]][[ %udhcpc_opts%]]",
                        ifd, exec);
}
# else
static int FAST_FUNC dhcp_up(struct interface_defn_t *ifd UNUSED_PARAM,
                execfn *exec UNUSED_PARAM)
{
        return 0; /* no dhcp support */
}
# endif

# if ENABLE_FEATURE_IFUPDOWN_EXTERNAL_DHCP
static int FAST_FUNC dhcp_down(struct interface_defn_t *ifd, execfn *exec)
{
        int result = 0;
        unsigned i;

        for (i = 0; i < ARRAY_SIZE(ext_dhcp_clients); i++) {
                if (exists_execable(ext_dhcp_clients[i].name)) {
                        result = execute(ext_dhcp_clients[i].stopcmd, ifd, exec);
                        if (result)
                                break;
                }
        }

        if (!result)
                bb_error_msg("warning: no dhcp clients found and stopped");

        /* Sleep a bit, otherwise static_down tries to bring down interface too soon,
           and it may come back up because udhcpc is still shutting down */
        usleep(100000);
        result += static_down(ifd, exec);
        return ((result == 3) ? 3 : 0);
}
# elif ENABLE_UDHCPC
static int FAST_FUNC dhcp_down(struct interface_defn_t *ifd, execfn *exec)
{
        int result;
        result = execute(
                "test -f /var/run/udhcpc.%iface%.pid && "
                "kill `cat /var/run/udhcpc.%iface%.pid` 2>/dev/null",
                ifd, exec);
        /* Also bring the hardware interface down since
           killing the dhcp client alone doesn't do it.
           This enables consecutive ifup->ifdown->ifup */
        /* Sleep a bit, otherwise static_down tries to bring down interface too soon,
           and it may come back up because udhcpc is still shutting down */
        usleep(100000);
        result += static_down(ifd, exec);
        return ((result == 3) ? 3 : 0);
}
# else
static int FAST_FUNC dhcp_down(struct interface_defn_t *ifd UNUSED_PARAM,
                execfn *exec UNUSED_PARAM)
{
        return 0; /* no dhcp support */
}
# endif

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

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

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

static int FAST_FUNC 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 FAST_FUNC 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  /* FEATURE_IFUPDOWN_IPV4 */


/* Returns pointer to the next word, or NULL.
 * In 1st case, advances *buf to the word after this one.
 */
static char *next_word(char **buf)
{
        unsigned length;
        char *word;

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

        /* Stop on EOL */
        if (*word == '\0')
                return NULL;

        /* Find the length of this word (can't be 0) */
        length = strcspn(word, " \t\n");

        /* Unless we are already at NUL, store NUL and advance */
        if (word[length] != '\0')
                word[length++] = '\0';

        *buf = skip_whitespace(word + length);

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

static struct interfaces_file_t *read_interfaces(const char *filename)
{
        /* Let's try to be compatible.
         *
         * "man 5 interfaces" says:
         * Lines starting with "#" are ignored. Note that end-of-line
         * comments are NOT supported, comments must be on a line of their own.
         * A line may be extended across multiple lines by making
         * the last character a backslash.
         *
         * Seen elsewhere in example config file:
         * A first non-blank "#" character makes the rest of the line
         * be ignored. Blank lines are ignored. Lines may be indented freely.
         * A "\" character at the very end of the line indicates the next line
         * should be treated as a continuation of the current one.
         */
#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 *buf;
        char *first_word;
        char *rest_of_line;
        enum { NONE, IFACE, MAPPING } currently_processing = NONE;

        defn = xzalloc(sizeof(*defn));
        f = xfopen_for_read(filename);

        while ((buf = xmalloc_fgetline(f)) != NULL) {
#if ENABLE_DESKTOP
                /* Trailing "\" concatenates lines */
                char *p;
                while ((p = last_char_is(buf, '\\')) != NULL) {
                        *p = '\0';
                        rest_of_line = xmalloc_fgetline(f);
                        if (!rest_of_line)
                                break;
                        p = xasprintf("%s%s", buf, rest_of_line);
                        free(buf);
                        free(rest_of_line);
                        buf = p;
                }
#endif
                rest_of_line = buf;
                first_word = next_word(&rest_of_line);
                if (!first_word || *first_word == '#') {
                        free(buf);
                        continue; /* blank/comment line */
                }

                if (strcmp(first_word, "mapping") == 0) {
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
                        currmap = xzalloc(sizeof(*currmap));

                        while ((first_word = next_word(&rest_of_line)) != NULL) {
                                currmap->match = xrealloc_vector(currmap->match, 4, currmap->n_matches);
                                currmap->match[currmap->n_matches++] = xstrdup(first_word);
                        }
                        /*currmap->max_mappings = 0; - done by xzalloc */
                        /*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(first_word, "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(*currif));
                        iface_name = next_word(&rest_of_line);
                        address_family_name = next_word(&rest_of_line);
                        method_name = next_word(&rest_of_line);

                        if (method_name == NULL)
                                bb_error_msg_and_die("too few parameters for line \"%s\"", buf);

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

                        if (rest_of_line[0] != '\0' /* && rest_of_line[0] != '#' */)
                                bb_error_msg_and_die("too many parameters \"%s\"", buf);

                        currif->iface = xstrdup(iface_name);

                        currif->address_family = get_address_family(addr_fams, address_family_name);
                        if (!currif->address_family)
                                bb_error_msg_and_die("unknown address type \"%s\"", address_family_name);

                        currif->method = get_method(currif->address_family, method_name);
                        if (!currif->method)
                                bb_error_msg_and_die("unknown method \"%s\"", method_name);

                        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_and_die("duplicate interface \"%s\"", tmp->iface);
                                }
                        }
                        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(first_word, "auto") == 0) {
                        while ((first_word = next_word(&rest_of_line)) != NULL) {

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

                                /* Add the interface to the list */
                                llist_add_to_end(&(defn->autointerfaces), xstrdup(first_word));
                                debug_noise("\nauto %s\n", first_word);
                        }
                        currently_processing = NONE;
                } else {
                        switch (currently_processing) {
                        case IFACE:
                                if (rest_of_line[0] == '\0')
                                        bb_error_msg_and_die("option with empty value \"%s\"", buf);

                                if (strcmp(first_word, "up") != 0
                                 && strcmp(first_word, "down") != 0
                                 && strcmp(first_word, "pre-up") != 0
                                 && strcmp(first_word, "post-down") != 0
                                ) {
                                        int i;
                                        for (i = 0; i < currif->n_options; i++) {
                                                if (strcmp(currif->option[i].name, first_word) == 0)
                                                        bb_error_msg_and_die("duplicate option \"%s\"", buf);
                                        }
                                }
                                if (currif->n_options >= currif->max_options) {
                                        currif->max_options += 10;
                                        currif->option = xrealloc(currif->option,
                                                sizeof(*currif->option) * currif->max_options);
                                }
                                debug_noise("\t%s=%s\n", first_word, rest_of_line);
                                currif->option[currif->n_options].name = xstrdup(first_word);
                                currif->option[currif->n_options].value = xstrdup(rest_of_line);
                                currif->n_options++;
                                break;
                        case MAPPING:
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
                                if (strcmp(first_word, "script") == 0) {
                                        if (currmap->script != NULL)
                                                bb_error_msg_and_die("duplicate script in mapping \"%s\"", buf);
                                        currmap->script = xstrdup(next_word(&rest_of_line));
                                } else if (strcmp(first_word, "map") == 0) {
                                        if (currmap->n_mappings >= currmap->max_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(&rest_of_line));
                                        currmap->n_mappings++;
                                } else {
                                        bb_error_msg_and_die("misplaced option \"%s\"", buf);
                                }
#endif
                                break;
                        case NONE:
                        default:
                                bb_error_msg_and_die("misplaced option \"%s\"", buf);
                        }
                }
                free(buf);
        } /* while (fgets) */

        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 *dst;
        char *src;
        char c;

        result = xasprintf(format, name, value);

        for (dst = src = result; (c = *src) != '=' && c; src++) {
                if (c == '-')
                        c = '_';
                if (c >= 'a' && c <= 'z')
                        c -= ('a' - 'A');
                if (isalnum(c) || c == '_')
                        *dst++ = c;
        }
        overlapping_strcpy(dst, src);

        return result;
}

static void set_environ(struct interface_defn_t *iface, const char *mode)
{
        int i;
        char **pp;

        if (G.my_environ != NULL) {
                for (pp = G.my_environ; *pp; pp++) {
                        free(*pp);
                }
                free(G.my_environ);
        }

        /* note: last element will stay NULL: */
        G.my_environ = xzalloc(sizeof(char *) * (iface->n_options + 6));
        pp = G.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;
                }
                *pp++ = setlocalenv("IF_%s=%s", iface->option[i].name, iface->option[i].value);
        }

        *pp++ = setlocalenv("%s=%s", "IFACE", iface->iface);
        *pp++ = setlocalenv("%s=%s", "ADDRFAM", iface->address_family->name);
        *pp++ = setlocalenv("%s=%s", "METHOD", iface->method->name);
        *pp++ = setlocalenv("%s=%s", "MODE", mode);
        if (G.startup_PATH)
                *pp++ = setlocalenv("%s=%s", "PATH", G.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_all();
                child = vfork();
                switch (child) {
                case -1: /* failure */
                        return 0;
                case 0: /* child */
                        execle(DEFAULT_SHELL, DEFAULT_SHELL, "-c", str, (char *) NULL, G.my_environ);
                        _exit(127);
                }
                safe_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, char *param)
{
        char *argv[3] = { command, param, NULL };
        struct fd_pair infd, outfd;
        pid_t pid;

        xpiped_pair(infd);
        xpiped_pair(outfd);

        fflush_all();
        pid = xvfork();

        if (pid == 0) {
                /* Child */
                /* NB: close _first_, then move fds! */
                close(infd.wr);
                close(outfd.rd);
                xmove_fd(infd.rd, 0);
                xmove_fd(outfd.wr, 1);
                BB_EXECVP_or_die(argv);
        }
        /* parent */
        close(infd.rd);
        close(outfd.wr);
        *in = xfdopen_for_write(infd.wr);
        *out = xfdopen_for_read(outfd.rd);
        return pid;
}

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. Never fails. */
        pid = popen2(&in, &out, map->script, physical);

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

                if (new_logical) {
                        /* 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;
                }
        }

        fclose(out);

        return logical;
}
#endif /* FEATURE_IFUPDOWN_MAPPING */

static llist_t *find_iface_state(llist_t *state_list, const char *iface)
{
        unsigned 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_for_read(CONFIG_IFUPDOWN_IFSTATE_PATH);

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

        INIT_G();

        G.startup_PATH = getenv("PATH");

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

        getopt32(argv, OPTION_STR, &interfaces);
        argv += optind;
        if (argv[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);

        /* Create a list of interfaces to work on */
        if (DO_ALL) {
                target_list = defn->autointerfaces;
        } else {
                llist_add_to_end(&target_list, argv[0]);
        }

        /* Update the interfaces */
        while (target_list) {
                llist_t *iface_list;
                struct interface_defn_t *currif;
                char *iface;
                char *liface;
                char *pch;
                bool okay = 0;
                int 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) {
                        bb_putchar('\n');
                }

                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_for_write(CONFIG_IFUPDOWN_IFSTATE_PATH);
                        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;
}