source: MondoRescue/branches/3.3/mindi-busybox/networking/ifupdown.c@ 3790

/* 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.
 */

//usage:#define ifup_trivial_usage
//usage:       "[-an"IF_FEATURE_IFUPDOWN_MAPPING("m")"vf] [-i FILE] IFACE..."
//usage:#define ifup_full_usage "\n\n"
//usage:       "    -a  De/configure all interfaces automatically"
//usage:     "\n    -i FILE Use FILE for interface definitions"
//usage:     "\n    -n  Print out what would happen, but don't do it"
//usage:    IF_FEATURE_IFUPDOWN_MAPPING(
//usage:     "\n        (note: doesn't disable mappings)"
//usage:     "\n    -m  Don't run any mappings"
//usage:    )
//usage:     "\n    -v  Print out what would happen before doing it"
//usage:     "\n    -f  Force de/configuration"
//usage:
//usage:#define ifdown_trivial_usage
//usage:       "[-an"IF_FEATURE_IFUPDOWN_MAPPING("m")"vf] [-i FILE] IFACE..."
//usage:#define ifdown_full_usage "\n\n"
//usage:       "    -a  De/configure all interfaces automatically"
//usage:     "\n    -i FILE Use FILE for interface definitions"
//usage:     "\n    -n  Print out what would happen, but don't do it"
//usage:    IF_FEATURE_IFUPDOWN_MAPPING(
//usage:     "\n        (note: doesn't disable mappings)"
//usage:     "\n    -m  Don't run any mappings"
//usage:    )
//usage:     "\n    -v  Print out what would happen before doing it"
//usage:     "\n    -f  Force de/configuration"

#include "libbb.h"
#include "common_bufsiz.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

#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 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 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;
    char *shell;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { setup_common_bufsiz(); } while (0)


static const char keywords_up_down[] ALIGN1 =
    "up\0"
    "down\0"
    "pre-up\0"
    "post-down\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 };
    smallint 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])
                command++;
            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, command, 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, command, 1);
                command++;
            }
            break;
        case '%':
            {
                char *nextpercent;
                char *varvalue;

                command++;
                nextpercent = strchr(command, '%');
                if (!nextpercent) {
                    /* Unterminated %var% */
                    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 (is_prefixed_with(command, "hwaddress")) {
                        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 (is_prefixed_with(command, "bnmask")) {
                        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) {
        /* Unbalanced bracket */
        free(result);
        return NULL;
    }

    if (!okay[0]) {
        /* Undefined variable and we aren't in a bracket */
        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);
    /* Reportedly, IPv6 needs "dev %iface%", but IPv4 does not: */
    result += execute("[[ip route add ::/0 via %gateway% dev %iface%]][[ metric %metric%]]", 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%[[ metric %metric%]]]]", 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);
    /* Reportedly, IPv6 needs "dev %iface%", but IPv4 does not: */
    result += execute("[[ip route add ::/0 via %gateway% dev %iface%]]", 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%[[ metric %metric%]]]]", 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%[[ metric %metric%]] %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%[[ -x hostname:%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 (executable_exists(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%[[ -x hostname:%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 (executable_exists(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 */

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

static const struct method_t link_methods[] = {
    { "none", link_up_down, link_up_down }
};

static const struct address_family_t addr_link = {
    "link", ARRAY_SIZE(link_methods), link_methods
};

/* 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, struct interfaces_file_t *defn)
{
    /* 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.
     *
     * Lines  beginning with "source" are used to include stanzas from
     * other files, so configuration can be split into many files.
     * The word "source" is followed by the path of file to be sourced.
     */
#if ENABLE_FEATURE_IFUPDOWN_MAPPING
    struct mapping_defn_t *currmap = NULL;
#endif
    struct interface_defn_t *currif = NULL;
    FILE *f;
    char *buf;
    char *first_word;
    char *rest_of_line;
    enum { NONE, IFACE, MAPPING } currently_processing = NONE;

    if (!defn)
        defn = xzalloc(sizeof(*defn));

    debug_noise("reading %s file:\n", filename);
    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->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
                &addr_link,
                NULL
            };
            char *iface_name;
            char *address_family_name;
            char *method_name;

            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);
#if 0
// Allegedly, Debian allows a duplicate definition:
// iface eth0 inet static
//     address 192.168.0.15
//     netmask 255.255.0.0
//     gateway 192.168.0.1
//
// iface eth0 inet static
//     address 10.0.0.1
//     netmask 255.255.255.0
//
// This adds *two* addresses to eth0 (probably requires use of "ip", not "ifconfig"
//
            llist_t *iface_list;
            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);
                }
            }
#endif
            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 if (strcmp(first_word, "source") == 0) {
            read_interfaces(next_word(&rest_of_line), defn);
        } 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, "post-up") == 0)
                    first_word += 5; /* "up" */
                else if (strcmp(first_word, "pre-down") == 0)
                    first_word += 4; /* "down" */

                /* If not one of "up", "down",... words... */
                if (index_in_strings(keywords_up_down, first_word) < 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);
                    }
                }
                debug_noise("\t%s=%s\n", first_word, rest_of_line);
                currif->option = xrealloc_vector(currif->option, 4, currif->n_options);
                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) {
                    currmap->mapping = xrealloc_vector(currmap->mapping, 2, currmap->n_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);
    debug_noise("\ndone reading %s\n\n", filename);

    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, const char *opt)
{
    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 + 7));
    pp = G.my_environ;

    for (i = 0; i < iface->n_options; i++) {
        if (index_in_strings(keywords_up_down, iface->option[i].name) >= 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);
    *pp++ = setlocalenv("%s=%s", "PHASE", opt);
    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();
        if (child < 0) /* failure */
            return 0;
        if (child == 0) { /* child */
            execle(G.shell, G.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", "pre-up");
    if (!execute_all(iface, "pre-up")) return 0;
    if (!iface->method->up(iface, doit)) return 0;
    set_environ(iface, "start", "post-up");
    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", "pre-down");
    if (!execute_all(iface, "down")) return 0;
    if (!iface->method->down(iface, doit)) return 0;
    set_environ(iface, "stop", "post-down");
    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)
{
    llist_t *search = state_list;

    while (search) {
        char *after_iface = is_prefixed_with(search->data, iface);
        if (after_iface
         && *after_iface == '='
        ) {
            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");
    G.shell = xstrdup(get_shell_name());

    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();
    }

    defn = read_interfaces(interfaces, NULL);

    /* 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;
        bool curr_failure = 0;

        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);
                    goto next;
                }
            } else {
                /* ifdown */
                if (!iface_state) {
                    bb_error_msg("interface %s not configured", iface);
                    goto next;
                }
            }
            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 have all variables for %s/%s",
                            liface, currif->address_family->name);
                    any_failures = curr_failure = 1;
                } else if (cmds_ret == 0) {
                    any_failures = curr_failure = 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 && !curr_failure) {
                char *newiface = xasprintf("%s=%s", iface, liface);
                if (!iface_state) {
                    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);
        }
 next:
        free(iface);
        free(liface);
    }

    return any_failures;
}