Convert to ANSI C

[ppp.git] / pppd / options.c

/*
 * options.c - handles option processing for PPP.
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <ctype.h>
#include <stdarg.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <syslog.h>
#include <string.h>
#include <pwd.h>
#ifdef PLUGIN
#include <dlfcn.h>
#endif

#ifdef PPP_FILTER
#include <pcap.h>
/*
 * There have been 3 or 4 different names for this in libpcap CVS, but
 * this seems to be what they have settled on...
 * For older versions of libpcap, use DLT_PPP - but that means
 * we lose the inbound and outbound qualifiers.
 */
#ifndef DLT_PPP_PPPD
#ifdef DLT_PPP_WITHDIRECTION
#define DLT_PPP_PPPD    DLT_PPP_WITHDIRECTION
#else
#define DLT_PPP_PPPD    DLT_PPP
#endif
#endif
#endif /* PPP_FILTER */

#include "pppd.h"
#include "pathnames.h"

#if defined(ultrix) || defined(NeXT)
char *strdup(char *);
#endif


struct option_value {
    struct option_value *next;
    const char *source;
    char value[1];
};

/*
 * Option variables and default values.
 */
int     debug = 0;              /* Debug flag */
int     kdebugflag = 0;         /* Tell kernel to print debug messages */
int     default_device = 1;     /* Using /dev/tty or equivalent */
char    devnam[MAXPATHLEN];     /* Device name */
bool    nodetach = 0;           /* Don't detach from controlling tty */
bool    updetach = 0;           /* Detach once link is up */
bool    master_detach;          /* Detach when we're (only) multilink master */
#ifdef SYSTEMD
bool    up_sdnotify = 0;        /* Notify systemd once link is up */
#endif
int     maxconnect = 0;         /* Maximum connect time */
char    user[MAXNAMELEN];       /* Username for PAP */
char    passwd[MAXSECRETLEN];   /* Password for PAP */
bool    persist = 0;            /* Reopen link after it goes down */
char    our_name[MAXNAMELEN];   /* Our name for authentication purposes */
bool    demand = 0;             /* do dial-on-demand */
char    *ipparam = NULL;        /* Extra parameter for ip up/down scripts */
int     idle_time_limit = 0;    /* Disconnect if idle for this many seconds */
int     holdoff = 30;           /* # seconds to pause before reconnecting */
bool    holdoff_specified;      /* true if a holdoff value has been given */
int     log_to_fd = 1;          /* send log messages to this fd too */
bool    log_default = 1;        /* log_to_fd is default (stdout) */
int     maxfail = 10;           /* max # of unsuccessful connection attempts */
char    linkname[MAXPATHLEN];   /* logical name for link */
bool    tune_kernel;            /* may alter kernel settings */
int     connect_delay = 1000;   /* wait this many ms after connect script */
int     req_unit = -1;          /* requested interface unit */
char    req_ifname[MAXIFNAMELEN];       /* requested interface name */
bool    multilink = 0;          /* Enable multilink operation */
char    *bundle_name = NULL;    /* bundle name for multilink */
bool    dump_options;           /* print out option values */
bool    dryrun;                 /* print out option values and exit */
char    *domain;                /* domain name set by domain option */
int     child_wait = 5;         /* # seconds to wait for children at exit */
struct userenv *userenv_list;   /* user environment variables */
int     dfl_route_metric = -1;  /* metric of the default route to set over the PPP link */

#ifdef MAXOCTETS
unsigned int  maxoctets = 0;    /* default - no limit */
int maxoctets_dir = 0;       /* default - sum of traffic */
int maxoctets_timeout = 1;   /* default 1 second */ 
#endif


extern option_t auth_options[];
extern struct stat devstat;

#ifdef PPP_FILTER
struct  bpf_program pass_filter;/* Filter program for packets to pass */
struct  bpf_program active_filter; /* Filter program for link-active pkts */
#endif

static option_t *curopt;        /* pointer to option being processed */
char *current_option;           /* the name of the option being parsed */
int  privileged_option;         /* set iff the current option came from root */
char *option_source;            /* string saying where the option came from */
int  option_priority = OPRIO_CFGFILE; /* priority of the current options */
bool devnam_fixed;              /* can no longer change device name */

static int logfile_fd = -1;     /* fd opened for log file */
static char logfile_name[MAXPATHLEN];   /* name of log file */

/*
 * Prototypes
 */
static int setdomain(char **);
static int readfile(char **);
static int callfile(char **);
static int showversion(char **);
static int showhelp(char **);
static void usage(void);
static int setlogfile(char **);
#ifdef PLUGIN
static int loadplugin(char **);
#endif

#ifdef PPP_FILTER
static int setpassfilter(char **);
static int setactivefilter(char **);
#endif

#ifdef MAXOCTETS
static int setmodir(char **);
#endif

static int user_setenv(char **);
static void user_setprint(option_t *, printer_func, void *);
static int user_unsetenv(char **);
static void user_unsetprint(option_t *, printer_func, void *);

static option_t *find_option(char *name);
static int process_option(option_t *, char *, char **);
static int n_arguments(option_t *);
static int number_option(char *, u_int32_t *, int);

/*
 * Structure to store extra lists of options.
 */
struct option_list {
    option_t *options;
    struct option_list *next;
};

static struct option_list *extra_options = NULL;

/*
 * Valid arguments.
 */
option_t general_options[] = {
    { "debug", o_int, &debug,
      "Increase debugging level", OPT_INC | OPT_NOARG | 1 },
    { "-d", o_int, &debug,
      "Increase debugging level",
      OPT_ALIAS | OPT_INC | OPT_NOARG | 1 },

    { "kdebug", o_int, &kdebugflag,
      "Set kernel driver debug level", OPT_PRIO },

    { "nodetach", o_bool, &nodetach,
      "Don't detach from controlling tty", OPT_PRIO | 1 },
    { "-detach", o_bool, &nodetach,
      "Don't detach from controlling tty", OPT_ALIAS | OPT_PRIOSUB | 1 },
#ifdef SYSTEMD
    { "up_sdnotify", o_bool, &up_sdnotify,
      "Notify systemd once link is up (implies nodetach)",
      OPT_PRIOSUB | OPT_A2COPY | 1, &nodetach },
#endif
    { "updetach", o_bool, &updetach,
      "Detach from controlling tty once link is up",
      OPT_PRIOSUB | OPT_A2CLR | 1, &nodetach },

    { "master_detach", o_bool, &master_detach,
      "Detach when we're multilink master but have no link", 1 },

    { "holdoff", o_int, &holdoff,
      "Set time in seconds before retrying connection",
      OPT_PRIO, &holdoff_specified },

    { "idle", o_int, &idle_time_limit,
      "Set time in seconds before disconnecting idle link", OPT_PRIO },

    { "maxconnect", o_int, &maxconnect,
      "Set connection time limit",
      OPT_PRIO | OPT_LLIMIT | OPT_NOINCR | OPT_ZEROINF },

    { "domain", o_special, (void *)setdomain,
      "Add given domain name to hostname",
      OPT_PRIO | OPT_PRIV | OPT_A2STRVAL, &domain },

    { "file", o_special, (void *)readfile,
      "Take options from a file", OPT_NOPRINT },
    { "call", o_special, (void *)callfile,
      "Take options from a privileged file", OPT_NOPRINT },

    { "persist", o_bool, &persist,
      "Keep on reopening connection after close", OPT_PRIO | 1 },
    { "nopersist", o_bool, &persist,
      "Turn off persist option", OPT_PRIOSUB },

    { "demand", o_bool, &demand,
      "Dial on demand", OPT_INITONLY | 1, &persist },

    { "--version", o_special_noarg, (void *)showversion,
      "Show version number" },
    { "--help", o_special_noarg, (void *)showhelp,
      "Show brief listing of options" },
    { "-h", o_special_noarg, (void *)showhelp,
      "Show brief listing of options", OPT_ALIAS },

    { "logfile", o_special, (void *)setlogfile,
      "Append log messages to this file",
      OPT_PRIO | OPT_A2STRVAL | OPT_STATIC, &logfile_name },
    { "logfd", o_int, &log_to_fd,
      "Send log messages to this file descriptor",
      OPT_PRIOSUB | OPT_A2CLR, &log_default },
    { "nolog", o_int, &log_to_fd,
      "Don't send log messages to any file",
      OPT_PRIOSUB | OPT_NOARG | OPT_VAL(-1) },
    { "nologfd", o_int, &log_to_fd,
      "Don't send log messages to any file descriptor",
      OPT_PRIOSUB | OPT_ALIAS | OPT_NOARG | OPT_VAL(-1) },

    { "linkname", o_string, linkname,
      "Set logical name for link",
      OPT_PRIO | OPT_PRIV | OPT_STATIC, NULL, MAXPATHLEN },

    { "maxfail", o_int, &maxfail,
      "Maximum number of unsuccessful connection attempts to allow",
      OPT_PRIO },

    { "ktune", o_bool, &tune_kernel,
      "Alter kernel settings as necessary", OPT_PRIO | 1 },
    { "noktune", o_bool, &tune_kernel,
      "Don't alter kernel settings", OPT_PRIOSUB },

    { "connect-delay", o_int, &connect_delay,
      "Maximum time (in ms) to wait after connect script finishes",
      OPT_PRIO },

    { "unit", o_int, &req_unit,
      "PPP interface unit number to use if possible",
      OPT_PRIO | OPT_LLIMIT, 0, 0 },

    { "ifname", o_string, req_ifname,
      "Set PPP interface name",
      OPT_PRIO | OPT_PRIV | OPT_STATIC, NULL, MAXIFNAMELEN },

    { "dump", o_bool, &dump_options,
      "Print out option values after parsing all options", 1 },
    { "dryrun", o_bool, &dryrun,
      "Stop after parsing, printing, and checking options", 1 },

    { "child-timeout", o_int, &child_wait,
      "Number of seconds to wait for child processes at exit",
      OPT_PRIO },

    { "set", o_special, (void *)user_setenv,
      "Set user environment variable",
      OPT_A2PRINTER | OPT_NOPRINT, (void *)user_setprint },
    { "unset", o_special, (void *)user_unsetenv,
      "Unset user environment variable",
      OPT_A2PRINTER | OPT_NOPRINT, (void *)user_unsetprint },

    { "defaultroute-metric", o_int, &dfl_route_metric,
      "Metric to use for the default route (Linux only; -1 for default behavior)",
      OPT_PRIV|OPT_LLIMIT|OPT_INITONLY, NULL, 0, -1 },

#ifdef HAVE_MULTILINK
    { "multilink", o_bool, &multilink,
      "Enable multilink operation", OPT_PRIO | 1 },
    { "mp", o_bool, &multilink,
      "Enable multilink operation", OPT_PRIOSUB | OPT_ALIAS | 1 },
    { "nomultilink", o_bool, &multilink,
      "Disable multilink operation", OPT_PRIOSUB | 0 },
    { "nomp", o_bool, &multilink,
      "Disable multilink operation", OPT_PRIOSUB | OPT_ALIAS | 0 },

    { "bundle", o_string, &bundle_name,
      "Bundle name for multilink", OPT_PRIO },
#endif /* HAVE_MULTILINK */

#ifdef PLUGIN
    { "plugin", o_special, (void *)loadplugin,
      "Load a plug-in module into pppd", OPT_PRIV | OPT_A2LIST },
#endif

#ifdef PPP_FILTER
    { "pass-filter", o_special, setpassfilter,
      "set filter for packets to pass", OPT_PRIO },

    { "active-filter", o_special, setactivefilter,
      "set filter for active pkts", OPT_PRIO },
#endif

#ifdef MAXOCTETS
    { "maxoctets", o_int, &maxoctets,
      "Set connection traffic limit",
      OPT_PRIO | OPT_LLIMIT | OPT_NOINCR | OPT_ZEROINF },
    { "mo", o_int, &maxoctets,
      "Set connection traffic limit",
      OPT_ALIAS | OPT_PRIO | OPT_LLIMIT | OPT_NOINCR | OPT_ZEROINF },
    { "mo-direction", o_special, setmodir,
      "Set direction for limit traffic (sum,in,out,max)" },
    { "mo-timeout", o_int, &maxoctets_timeout,
      "Check for traffic limit every N seconds", OPT_PRIO | OPT_LLIMIT | 1 },
#endif

    { NULL }
};

#ifndef IMPLEMENTATION
#define IMPLEMENTATION ""
#endif

static char *usage_string = "\
pppd version %s\n\
Usage: %s [ options ], where options are:\n\
        <device>        Communicate over the named device\n\
        <speed>         Set the baud rate to <speed>\n\
        <loc>:<rem>     Set the local and/or remote interface IP\n\
                        addresses.  Either one may be omitted.\n\
        asyncmap <n>    Set the desired async map to hex <n>\n\
        auth            Require authentication from peer\n\
        connect <p>     Invoke shell command <p> to set up the serial line\n\
        crtscts         Use hardware RTS/CTS flow control\n\
        defaultroute    Add default route through interface\n\
        file <f>        Take options from file <f>\n\
        modem           Use modem control lines\n\
        mru <n>         Set MRU value to <n> for negotiation\n\
See pppd(8) for more options.\n\
";

/*
 * parse_args - parse a string of arguments from the command line.
 */
int
parse_args(int argc, char **argv)
{
    char *arg;
    option_t *opt;
    int n;

    privileged_option = privileged;
    option_source = "command line";
    option_priority = OPRIO_CMDLINE;
    while (argc > 0) {
        arg = *argv++;
        --argc;
        opt = find_option(arg);
        if (opt == NULL) {
            option_error("unrecognized option '%s'", arg);
            usage();
            return 0;
        }
        n = n_arguments(opt);
        if (argc < n) {
            option_error("too few parameters for option %s", arg);
            return 0;
        }
        if (!process_option(opt, arg, argv))
            return 0;
        argc -= n;
        argv += n;
    }
    return 1;
}

/*
 * options_from_file - Read a string of options from a file,
 * and interpret them.
 */
int
options_from_file(char *filename, int must_exist, int check_prot, int priv)
{
    FILE *f;
    int i, newline, ret, err;
    option_t *opt;
    int oldpriv, n;
    char *oldsource;
    uid_t euid;
    char *argv[MAXARGS];
    char args[MAXARGS][MAXWORDLEN];
    char cmd[MAXWORDLEN];

    euid = geteuid();
    if (check_prot && seteuid(getuid()) == -1) {
        option_error("unable to drop privileges to open %s: %m", filename);
        return 0;
    }
    f = fopen(filename, "r");
    err = errno;
    if (check_prot && seteuid(euid) == -1)
        fatal("unable to regain privileges");
    if (f == NULL) {
        errno = err;
        if (!must_exist) {
            if (err != ENOENT && err != ENOTDIR)
                warn("Warning: can't open options file %s: %m", filename);
            return 1;
        }
        option_error("Can't open options file %s: %m", filename);
        return 0;
    }

    oldpriv = privileged_option;
    privileged_option = priv;
    oldsource = option_source;
    option_source = strdup(filename);
    if (option_source == NULL)
        option_source = "file";
    ret = 0;
    while (getword(f, cmd, &newline, filename)) {
        opt = find_option(cmd);
        if (opt == NULL) {
            option_error("In file %s: unrecognized option '%s'",
                         filename, cmd);
            goto err;
        }
        n = n_arguments(opt);
        for (i = 0; i < n; ++i) {
            if (!getword(f, args[i], &newline, filename)) {
                option_error(
                        "In file %s: too few parameters for option '%s'",
                        filename, cmd);
                goto err;
            }
            argv[i] = args[i];
        }
        if (!process_option(opt, cmd, argv))
            goto err;
    }
    ret = 1;

err:
    fclose(f);
    privileged_option = oldpriv;
    option_source = oldsource;
    return ret;
}

/*
 * options_from_user - See if the use has a ~/.ppprc file,
 * and if so, interpret options from it.
 */
int
options_from_user(void)
{
    char *user, *path, *file;
    int ret;
    struct passwd *pw;
    size_t pl;

    pw = getpwuid(getuid());
    if (pw == NULL || (user = pw->pw_dir) == NULL || user[0] == 0)
        return 1;
    file = _PATH_USEROPT;
    pl = strlen(user) + strlen(file) + 2;
    path = malloc(pl);
    if (path == NULL)
        novm("init file name");
    slprintf(path, pl, "%s/%s", user, file);
    option_priority = OPRIO_CFGFILE;
    ret = options_from_file(path, 0, 1, privileged);
    free(path);
    return ret;
}

/*
 * options_for_tty - See if an options file exists for the serial
 * device, and if so, interpret options from it.
 * We only allow the per-tty options file to override anything from
 * the command line if it is something that the user can't override
 * once it has been set by root; this is done by giving configuration
 * files a lower priority than the command line.
 */
int
options_for_tty(void)
{
    char *dev, *path, *p;
    int ret;
    size_t pl;

    dev = devnam;
    if ((p = strstr(dev, "/dev/")) != NULL)
        dev = p + 5;
    if (dev[0] == 0 || strcmp(dev, "tty") == 0)
        return 1;               /* don't look for /etc/ppp/options.tty */
    pl = strlen(_PATH_TTYOPT) + strlen(dev) + 1;
    path = malloc(pl);
    if (path == NULL)
        novm("tty init file name");
    slprintf(path, pl, "%s%s", _PATH_TTYOPT, dev);
    /* Turn slashes into dots, for Solaris case (e.g. /dev/term/a) */
    for (p = path + strlen(_PATH_TTYOPT); *p != 0; ++p)
        if (*p == '/')
            *p = '.';
    option_priority = OPRIO_CFGFILE;
    ret = options_from_file(path, 0, 0, 1);
    free(path);
    return ret;
}

/*
 * options_from_list - process a string of options in a wordlist.
 */
int
options_from_list(struct wordlist *w, int priv)
{
    char *argv[MAXARGS];
    option_t *opt;
    int i, n, ret = 0;
    struct wordlist *w0;

    privileged_option = priv;
    option_source = "secrets file";
    option_priority = OPRIO_SECFILE;

    while (w != NULL) {
        opt = find_option(w->word);
        if (opt == NULL) {
            option_error("In secrets file: unrecognized option '%s'",
                         w->word);
            goto err;
        }
        n = n_arguments(opt);
        w0 = w;
        for (i = 0; i < n; ++i) {
            w = w->next;
            if (w == NULL) {
                option_error(
                        "In secrets file: too few parameters for option '%s'",
                        w0->word);
                goto err;
            }
            argv[i] = w->word;
        }
        if (!process_option(opt, w0->word, argv))
            goto err;
        w = w->next;
    }
    ret = 1;

err:
    return ret;
}

/*
 * match_option - see if this option matches an option_t structure.
 */
static int
match_option(char *name, option_t *opt, int dowild)
{
        int (*match)(char *, char **, int);

        if (dowild != (opt->type == o_wild))
                return 0;
        if (!dowild)
                return strcmp(name, opt->name) == 0;
        match = (int (*)(char *, char **, int)) opt->addr;
        return (*match)(name, NULL, 0);
}

/*
 * find_option - scan the option lists for the various protocols
 * looking for an entry with the given name.
 * This could be optimized by using a hash table.
 */
static option_t *
find_option(char *name)
{
        option_t *opt;
        struct option_list *list;
        int i, dowild;

        for (dowild = 0; dowild <= 1; ++dowild) {
                for (opt = general_options; opt->name != NULL; ++opt)
                        if (match_option(name, opt, dowild))
                                return opt;
                for (opt = auth_options; opt->name != NULL; ++opt)
                        if (match_option(name, opt, dowild))
                                return opt;
                for (list = extra_options; list != NULL; list = list->next)
                        for (opt = list->options; opt->name != NULL; ++opt)
                                if (match_option(name, opt, dowild))
                                        return opt;
                for (opt = the_channel->options; opt->name != NULL; ++opt)
                        if (match_option(name, opt, dowild))
                                return opt;
                for (i = 0; protocols[i] != NULL; ++i)
                        if ((opt = protocols[i]->options) != NULL)
                                for (; opt->name != NULL; ++opt)
                                        if (match_option(name, opt, dowild))
                                                return opt;
        }
        return NULL;
}

/*
 * process_option - process one new-style option.
 */
static int
process_option(option_t *opt, char *cmd, char **argv)
{
    u_int32_t v;
    int iv, a;
    char *sv;
    int (*parser)(char **);
    int (*wildp)(char *, char **, int);
    char *optopt = (opt->type == o_wild)? "": " option";
    int prio = option_priority;
    option_t *mainopt = opt;

    current_option = opt->name;
    if ((opt->flags & OPT_PRIVFIX) && privileged_option)
        prio += OPRIO_ROOT;
    while (mainopt->flags & OPT_PRIOSUB)
        --mainopt;
    if (mainopt->flags & OPT_PRIO) {
        if (prio < mainopt->priority) {
            /* new value doesn't override old */
            if (prio == OPRIO_CMDLINE && mainopt->priority > OPRIO_ROOT) {
                option_error("%s%s set in %s cannot be overridden\n",
                             opt->name, optopt, mainopt->source);
                return 0;
            }
            return 1;
        }
        if (prio > OPRIO_ROOT && mainopt->priority == OPRIO_CMDLINE)
            warn("%s%s from %s overrides command line",
                 opt->name, optopt, option_source);
    }

    if ((opt->flags & OPT_INITONLY) && phase != PHASE_INITIALIZE) {
        option_error("%s%s cannot be changed after initialization",
                     opt->name, optopt);
        return 0;
    }
    if ((opt->flags & OPT_PRIV) && !privileged_option) {
        option_error("using the %s%s requires root privilege",
                     opt->name, optopt);
        return 0;
    }
    if ((opt->flags & OPT_ENABLE) && *(bool *)(opt->addr2) == 0) {
        option_error("%s%s is disabled", opt->name, optopt);
        return 0;
    }
    if ((opt->flags & OPT_DEVEQUIV) && devnam_fixed) {
        option_error("the %s%s may not be changed in %s",
                     opt->name, optopt, option_source);
        return 0;
    }

    switch (opt->type) {
    case o_bool:
        v = opt->flags & OPT_VALUE;
        *(bool *)(opt->addr) = v;
        if (opt->addr2 && (opt->flags & OPT_A2COPY))
            *(bool *)(opt->addr2) = v;
        else if (opt->addr2 && (opt->flags & OPT_A2CLR))
            *(bool *)(opt->addr2) = 0;
        else if (opt->addr2 && (opt->flags & OPT_A2CLRB))
            *(u_char *)(opt->addr2) &= ~v;
        else if (opt->addr2 && (opt->flags & OPT_A2OR))
            *(u_char *)(opt->addr2) |= v;
        break;

    case o_int:
        iv = 0;
        if ((opt->flags & OPT_NOARG) == 0) {
            if (!int_option(*argv, &iv))
                return 0;
            if ((((opt->flags & OPT_LLIMIT) && iv < opt->lower_limit)
                 || ((opt->flags & OPT_ULIMIT) && iv > opt->upper_limit))
                && !((opt->flags & OPT_ZEROOK && iv == 0))) {
                char *zok = (opt->flags & OPT_ZEROOK)? " zero or": "";
                switch (opt->flags & OPT_LIMITS) {
                case OPT_LLIMIT:
                    option_error("%s value must be%s >= %d",
                                 opt->name, zok, opt->lower_limit);
                    break;
                case OPT_ULIMIT:
                    option_error("%s value must be%s <= %d",
                                 opt->name, zok, opt->upper_limit);
                    break;
                case OPT_LIMITS:
                    option_error("%s value must be%s between %d and %d",
                                opt->name, zok, opt->lower_limit, opt->upper_limit);
                    break;
                }
                return 0;
            }
        }
        a = opt->flags & OPT_VALUE;
        if (a >= 128)
            a -= 256;           /* sign extend */
        iv += a;
        if (opt->flags & OPT_INC)
            iv += *(int *)(opt->addr);
        if ((opt->flags & OPT_NOINCR) && !privileged_option) {
            int oldv = *(int *)(opt->addr);
            if ((opt->flags & OPT_ZEROINF) ?
                (oldv != 0 && (iv == 0 || iv > oldv)) : (iv > oldv)) {
                option_error("%s value cannot be increased", opt->name);
                return 0;
            }
        }
        *(int *)(opt->addr) = iv;
        if (opt->addr2 && (opt->flags & OPT_A2COPY))
            *(int *)(opt->addr2) = iv;
        break;

    case o_uint32:
        if (opt->flags & OPT_NOARG) {
            v = opt->flags & OPT_VALUE;
            if (v & 0x80)
                    v |= 0xffffff00U;
        } else if (!number_option(*argv, &v, 16))
            return 0;
        if (opt->flags & OPT_OR)
            v |= *(u_int32_t *)(opt->addr);
        *(u_int32_t *)(opt->addr) = v;
        if (opt->addr2 && (opt->flags & OPT_A2COPY))
            *(u_int32_t *)(opt->addr2) = v;
        break;

    case o_string:
        if (opt->flags & OPT_STATIC) {
            strlcpy((char *)(opt->addr), *argv, opt->upper_limit);
        } else {
            char **optptr = (char **)(opt->addr);
            sv = strdup(*argv);
            if (sv == NULL)
                novm("option argument");
            if (*optptr)
                free(*optptr);
            *optptr = sv;
        }
        /* obfuscate original argument for things like password */
        if (opt->flags & OPT_HIDE) {
            memset(*argv, '?', strlen(*argv));
            *argv = "********";
        }
        break;

    case o_special_noarg:
    case o_special:
        parser = (int (*)(char **)) opt->addr;
        curopt = opt;
        if (!(*parser)(argv))
            return 0;
        if (opt->flags & OPT_A2LIST) {
            struct option_value *ovp, *pp;

            ovp = malloc(sizeof(*ovp) + strlen(*argv));
            if (ovp != 0) {
                strcpy(ovp->value, *argv);
                ovp->source = option_source;
                ovp->next = NULL;
                if (opt->addr2 == NULL) {
                    opt->addr2 = ovp;
                } else {
                    for (pp = opt->addr2; pp->next != NULL; pp = pp->next)
                        ;
                    pp->next = ovp;
                }
            }
        }
        break;

    case o_wild:
        wildp = (int (*)(char *, char **, int)) opt->addr;
        if (!(*wildp)(cmd, argv, 1))
            return 0;
        break;
    }

    /*
     * If addr2 wasn't used by any flag (OPT_A2COPY, etc.) but is set,
     * treat it as a bool and set/clear it based on the OPT_A2CLR bit.
     */
    if (opt->addr2 && (opt->flags & (OPT_A2COPY|OPT_ENABLE
                |OPT_A2PRINTER|OPT_A2STRVAL|OPT_A2LIST|OPT_A2OR)) == 0)
        *(bool *)(opt->addr2) = !(opt->flags & OPT_A2CLR);

    mainopt->source = option_source;
    mainopt->priority = prio;
    mainopt->winner = opt - mainopt;

    return 1;
}

/*
 * override_value - if the option priorities would permit us to
 * override the value of option, return 1 and update the priority
 * and source of the option value.  Otherwise returns 0.
 */
int
override_value(char *option, int priority, const char *source)
{
        option_t *opt;

        opt = find_option(option);
        if (opt == NULL)
                return 0;
        while (opt->flags & OPT_PRIOSUB)
                --opt;
        if ((opt->flags & OPT_PRIO) && priority < opt->priority)
                return 0;
        opt->priority = priority;
        opt->source = source;
        opt->winner = -1;
        return 1;
}

/*
 * n_arguments - tell how many arguments an option takes
 */
static int
n_arguments(option_t *opt)
{
        return (opt->type == o_bool || opt->type == o_special_noarg
                || (opt->flags & OPT_NOARG))? 0: 1;
}

/*
 * add_options - add a list of options to the set we grok.
 */
void
add_options(option_t *opt)
{
    struct option_list *list;

    list = malloc(sizeof(*list));
    if (list == 0)
        novm("option list entry");
    list->options = opt;
    list->next = extra_options;
    extra_options = list;
}

/*
 * check_options - check that options are valid and consistent.
 */
void
check_options(void)
{
        if (logfile_fd >= 0 && logfile_fd != log_to_fd)
                close(logfile_fd);
}

/*
 * print_option - print out an option and its value
 */
static void
print_option(option_t *opt, option_t *mainopt, printer_func printer, void *arg)
{
        int i, v;
        char *p;

        if (opt->flags & OPT_NOPRINT)
                return;
        switch (opt->type) {
        case o_bool:
                v = opt->flags & OPT_VALUE;
                if (*(bool *)opt->addr != v)
                        /* this can happen legitimately, e.g. lock
                           option turned off for default device */
                        break;
                printer(arg, "%s", opt->name);
                break;
        case o_int:
                v = opt->flags & OPT_VALUE;
                if (v >= 128)
                        v -= 256;
                i = *(int *)opt->addr;
                if (opt->flags & OPT_NOARG) {
                        printer(arg, "%s", opt->name);
                        if (i != v) {
                                if (opt->flags & OPT_INC) {
                                        for (; i > v; i -= v)
                                                printer(arg, " %s", opt->name);
                                } else
                                        printer(arg, " # oops: %d not %d\n",
                                                i, v);
                        }
                } else {
                        printer(arg, "%s %d", opt->name, i);
                }
                break;
        case o_uint32:
                printer(arg, "%s", opt->name);
                if ((opt->flags & OPT_NOARG) == 0)
                        printer(arg, " %x", *(u_int32_t *)opt->addr);
                break;

        case o_string:
                if (opt->flags & OPT_HIDE) {
                        p = "??????";
                } else {
                        p = (char *) opt->addr;
                        if ((opt->flags & OPT_STATIC) == 0)
                                p = *(char **)p;
                }
                printer(arg, "%s %q", opt->name, p);
                break;

        case o_special:
        case o_special_noarg:
        case o_wild:
                if (opt->type != o_wild) {
                        printer(arg, "%s", opt->name);
                        if (n_arguments(opt) == 0)
                                break;
                        printer(arg, " ");
                }
                if (opt->flags & OPT_A2PRINTER) {
                        void (*oprt)(option_t *, printer_func, void *);
                        oprt = (void (*)(option_t *, printer_func, void *))
                                opt->addr2;
                        (*oprt)(opt, printer, arg);
                } else if (opt->flags & OPT_A2STRVAL) {
                        p = (char *) opt->addr2;
                        if ((opt->flags & OPT_STATIC) == 0)
                                p = *(char **)p;
                        printer(arg, "%q", p);
                } else if (opt->flags & OPT_A2LIST) {
                        struct option_value *ovp;

                        ovp = (struct option_value *) opt->addr2;
                        for (;;) {
                                printer(arg, "%q", ovp->value);
                                if ((ovp = ovp->next) == NULL)
                                        break;
                                printer(arg, "\t\t# (from %s)\n%s ",
                                        ovp->source, opt->name);
                        }
                } else {
                        printer(arg, "xxx # [don't know how to print value]");
                }
                break;

        default:
                printer(arg, "# %s value (type %d\?\?)", opt->name, opt->type);
                break;
        }
        printer(arg, "\t\t# (from %s)\n", mainopt->source);
}

/*
 * print_option_list - print out options in effect from an
 * array of options.
 */
static void
print_option_list(option_t *opt, printer_func printer, void *arg)
{
        while (opt->name != NULL) {
                if (opt->priority != OPRIO_DEFAULT
                    && opt->winner != (short int) -1)
                        print_option(opt + opt->winner, opt, printer, arg);
                do {
                        ++opt;
                } while (opt->flags & OPT_PRIOSUB);
        }
}

/*
 * print_options - print out what options are in effect.
 */
void
print_options(printer_func printer, void *arg)
{
        struct option_list *list;
        int i;

        printer(arg, "pppd options in effect:\n");
        print_option_list(general_options, printer, arg);
        print_option_list(auth_options, printer, arg);
        for (list = extra_options; list != NULL; list = list->next)
                print_option_list(list->options, printer, arg);
        print_option_list(the_channel->options, printer, arg);
        for (i = 0; protocols[i] != NULL; ++i)
                print_option_list(protocols[i]->options, printer, arg);
}

/*
 * usage - print out a message telling how to use the program.
 */
static void
usage(void)
{
    if (phase == PHASE_INITIALIZE)
        fprintf(stderr, usage_string, VERSION, progname);
}

/*
 * showhelp - print out usage message and exit.
 */
static int
showhelp(char **argv)
{
    if (phase == PHASE_INITIALIZE) {
        usage();
        exit(0);
    }
    return 0;
}

/*
 * showversion - print out the version number and exit.
 */
static int
showversion(char **argv)
{
    if (phase == PHASE_INITIALIZE) {
        fprintf(stdout, "pppd version %s\n", VERSION);
        exit(0);
    }
    return 0;
}

/*
 * option_error - print a message about an error in an option.
 * The message is logged, and also sent to
 * stderr if phase == PHASE_INITIALIZE.
 */
void
option_error(char *fmt, ...)
{
    va_list args;
    char buf[1024];

    va_start(args, fmt);
    vslprintf(buf, sizeof(buf), fmt, args);
    va_end(args);
    if (phase == PHASE_INITIALIZE)
        fprintf(stderr, "%s: %s\n", progname, buf);
    syslog(LOG_ERR, "%s", buf);
}

#if 0
/*
 * readable - check if a file is readable by the real user.
 */
int
readable(int fd)
{
    uid_t uid;
    int i;
    struct stat sbuf;

    uid = getuid();
    if (uid == 0)
        return 1;
    if (fstat(fd, &sbuf) != 0)
        return 0;
    if (sbuf.st_uid == uid)
        return sbuf.st_mode & S_IRUSR;
    if (sbuf.st_gid == getgid())
        return sbuf.st_mode & S_IRGRP;
    for (i = 0; i < ngroups; ++i)
        if (sbuf.st_gid == groups[i])
            return sbuf.st_mode & S_IRGRP;
    return sbuf.st_mode & S_IROTH;
}
#endif

/*
 * Read a word from a file.
 * Words are delimited by white-space or by quotes (" or ').
 * Quotes, white-space and \ may be escaped with \.
 * \<newline> is ignored.
 */
int
getword(FILE *f, char *word, int *newlinep, char *filename)
{
    int c, len, escape;
    int quoted, comment;
    int value, digit, got, n;

#define isoctal(c) ((c) >= '0' && (c) < '8')

    *newlinep = 0;
    len = 0;
    escape = 0;
    comment = 0;
    quoted = 0;

    /*
     * First skip white-space and comments.
     */
    for (;;) {
        c = getc(f);
        if (c == EOF)
            break;

        /*
         * A newline means the end of a comment; backslash-newline
         * is ignored.  Note that we cannot have escape && comment.
         */
        if (c == '\n') {
            if (!escape) {
                *newlinep = 1;
                comment = 0;
            } else
                escape = 0;
            continue;
        }

        /*
         * Ignore characters other than newline in a comment.
         */
        if (comment)
            continue;

        /*
         * If this character is escaped, we have a word start.
         */
        if (escape)
            break;

        /*
         * If this is the escape character, look at the next character.
         */
        if (c == '\\') {
            escape = 1;
            continue;
        }

        /*
         * If this is the start of a comment, ignore the rest of the line.
         */
        if (c == '#') {
            comment = 1;
            continue;
        }

        /*
         * A non-whitespace character is the start of a word.
         */
        if (!isspace(c))
            break;
    }

    /*
     * Process characters until the end of the word.
     */
    while (c != EOF) {
        if (escape) {
            /*
             * This character is escaped: backslash-newline is ignored,
             * various other characters indicate particular values
             * as for C backslash-escapes.
             */
            escape = 0;
            if (c == '\n') {
                c = getc(f);
                continue;
            }

            got = 0;
            switch (c) {
            case 'a':
                value = '\a';
                break;
            case 'b':
                value = '\b';
                break;
            case 'f':
                value = '\f';
                break;
            case 'n':
                value = '\n';
                break;
            case 'r':
                value = '\r';
                break;
            case 's':
                value = ' ';
                break;
            case 't':
                value = '\t';
                break;

            default:
                if (isoctal(c)) {
                    /*
                     * \ddd octal sequence
                     */
                    value = 0;
                    for (n = 0; n < 3 && isoctal(c); ++n) {
                        value = (value << 3) + (c & 07);
                        c = getc(f);
                    }
                    got = 1;
                    break;
                }

                if (c == 'x') {
                    /*
                     * \x<hex_string> sequence
                     */
                    value = 0;
                    c = getc(f);
                    for (n = 0; n < 2 && isxdigit(c); ++n) {
                        digit = toupper(c) - '0';
                        if (digit > 10)
                            digit += '0' + 10 - 'A';
                        value = (value << 4) + digit;
                        c = getc (f);
                    }
                    got = 1;
                    break;
                }

                /*
                 * Otherwise the character stands for itself.
                 */
                value = c;
                break;
            }

            /*
             * Store the resulting character for the escape sequence.
             */
            if (len < MAXWORDLEN) {
                word[len] = value;
                ++len;
            }

            if (!got)
                c = getc(f);
            continue;
        }

        /*
         * Backslash starts a new escape sequence.
         */
        if (c == '\\') {
            escape = 1;
            c = getc(f);
            continue;
        }

        /*
         * Not escaped: check for the start or end of a quoted
         * section and see if we've reached the end of the word.
         */
        if (quoted) {
            if (c == quoted) {
                quoted = 0;
                c = getc(f);
                continue;
            }
        } else if (c == '"' || c == '\'') {
            quoted = c;
            c = getc(f);
            continue;
        } else if (isspace(c) || c == '#') {
            ungetc (c, f);
            break;
        }

        /*
         * An ordinary character: store it in the word and get another.
         */
        if (len < MAXWORDLEN) {
            word[len] = c;
            ++len;
        }

        c = getc(f);
    }
    word[MAXWORDLEN-1] = 0;     /* make sure word is null-terminated */

    /*
     * End of the word: check for errors.
     */
    if (c == EOF) {
        if (ferror(f)) {
            if (errno == 0)
                errno = EIO;
            option_error("Error reading %s: %m", filename);
            die(1);
        }
        /*
         * If len is zero, then we didn't find a word before the
         * end of the file.
         */
        if (len == 0)
            return 0;
        if (quoted)
            option_error("warning: quoted word runs to end of file (%.20s...)",
                         filename, word);
    }

    /*
     * Warn if the word was too long, and append a terminating null.
     */
    if (len >= MAXWORDLEN) {
        option_error("warning: word in file %s too long (%.20s...)",
                     filename, word);
        len = MAXWORDLEN - 1;
    }
    word[len] = 0;

    return 1;

#undef isoctal

}

/*
 * number_option - parse an unsigned numeric parameter for an option.
 */
static int
number_option(char *str, u_int32_t *valp, int base)
{
    char *ptr;

    *valp = strtoul(str, &ptr, base);
    if (ptr == str) {
        option_error("invalid numeric parameter '%s' for %s option",
                     str, current_option);
        return 0;
    }
    return 1;
}


/*
 * int_option - like number_option, but valp is int *,
 * the base is assumed to be 0, and *valp is not changed
 * if there is an error.
 */
int
int_option(char *str, int *valp)
{
    u_int32_t v;

    if (!number_option(str, &v, 0))
        return 0;
    *valp = (int) v;
    return 1;
}


/*
 * The following procedures parse options.
 */

/*
 * readfile - take commands from a file.
 */
static int
readfile(char **argv)
{
    return options_from_file(*argv, 1, 1, privileged_option);
}

/*
 * callfile - take commands from /etc/ppp/peers/<name>.
 * Name may not contain /../, start with / or ../, or end in /..
 */
static int
callfile(char **argv)
{
    char *fname, *arg, *p;
    int l, ok;

    arg = *argv;
    ok = 1;
    if (arg[0] == '/' || arg[0] == 0)
        ok = 0;
    else {
        for (p = arg; *p != 0; ) {
            if (p[0] == '.' && p[1] == '.' && (p[2] == '/' || p[2] == 0)) {
                ok = 0;
                break;
            }
            while (*p != '/' && *p != 0)
                ++p;
            if (*p == '/')
                ++p;
        }
    }
    if (!ok) {
        option_error("call option value may not contain .. or start with /");
        return 0;
    }

    l = strlen(arg) + strlen(_PATH_PEERFILES) + 1;
    if ((fname = (char *) malloc(l)) == NULL)
        novm("call file name");
    slprintf(fname, l, "%s%s", _PATH_PEERFILES, arg);

    ok = options_from_file(fname, 1, 1, 1);

    free(fname);
    return ok;
}

#ifdef PPP_FILTER
/*
 * setpassfilter - Set the pass filter for packets
 */
static int
setpassfilter(char **argv)
{
    pcap_t *pc;
    int ret = 1;

    pc = pcap_open_dead(DLT_PPP_PPPD, 65535);
    if (pcap_compile(pc, &pass_filter, *argv, 1, netmask) == -1) {
        option_error("error in pass-filter expression: %s\n",
                     pcap_geterr(pc));
        ret = 0;
    }
    pcap_close(pc);

    return ret;
}

/*
 * setactivefilter - Set the active filter for packets
 */
static int
setactivefilter(char **argv)
{
    pcap_t *pc;
    int ret = 1;

    pc = pcap_open_dead(DLT_PPP_PPPD, 65535);
    if (pcap_compile(pc, &active_filter, *argv, 1, netmask) == -1) {
        option_error("error in active-filter expression: %s\n",
                     pcap_geterr(pc));
        ret = 0;
    }
    pcap_close(pc);

    return ret;
}
#endif

/*
 * setdomain - Set domain name to append to hostname 
 */
static int
setdomain(char **argv)
{
    gethostname(hostname, MAXNAMELEN);
    if (**argv != 0) {
        if (**argv != '.')
            strncat(hostname, ".", MAXNAMELEN - strlen(hostname));
        domain = hostname + strlen(hostname);
        strncat(hostname, *argv, MAXNAMELEN - strlen(hostname));
    }
    hostname[MAXNAMELEN-1] = 0;
    return (1);
}

static int
setlogfile(char **argv)
{
    int fd, err;
    uid_t euid;

    euid = geteuid();
    if (!privileged_option && seteuid(getuid()) == -1) {
        option_error("unable to drop permissions to open %s: %m", *argv);
        return 0;
    }
    fd = open(*argv, O_WRONLY | O_APPEND | O_CREAT | O_EXCL, 0644);
    if (fd < 0 && errno == EEXIST)
        fd = open(*argv, O_WRONLY | O_APPEND);
    err = errno;
    if (!privileged_option && seteuid(euid) == -1)
        fatal("unable to regain privileges: %m");
    if (fd < 0) {
        errno = err;
        option_error("Can't open log file %s: %m", *argv);
        return 0;
    }
    strlcpy(logfile_name, *argv, sizeof(logfile_name));
    if (logfile_fd >= 0)
        close(logfile_fd);
    logfile_fd = fd;
    log_to_fd = fd;
    log_default = 0;
    return 1;
}

#ifdef MAXOCTETS
static int
setmodir(char **argv)
{
    if(*argv == NULL)
        return 0;
    if(!strcmp(*argv,"in")) {
        maxoctets_dir = PPP_OCTETS_DIRECTION_IN;
    } else if (!strcmp(*argv,"out")) {
        maxoctets_dir = PPP_OCTETS_DIRECTION_OUT;
    } else if (!strcmp(*argv,"max")) {
        maxoctets_dir = PPP_OCTETS_DIRECTION_MAXOVERAL;
    } else {
        maxoctets_dir = PPP_OCTETS_DIRECTION_SUM;
    }
    return 1;
}
#endif

#ifdef PLUGIN
static int
loadplugin(char **argv)
{
    char *arg = *argv;
    void *handle;
    const char *err;
    void (*init)(void);
    char *path = arg;
    const char *vers;

    if (strchr(arg, '/') == 0) {
        const char *base = _PATH_PLUGIN;
        int l = strlen(base) + strlen(arg) + 2;
        path = malloc(l);
        if (path == 0)
            novm("plugin file path");
        strlcpy(path, base, l);
        strlcat(path, "/", l);
        strlcat(path, arg, l);
    }
    handle = dlopen(path, RTLD_GLOBAL | RTLD_NOW);
    if (handle == 0) {
        err = dlerror();
        if (err != 0)
            option_error("%s", err);
        option_error("Couldn't load plugin %s", arg);
        goto err;
    }
    init = (void (*)(void))dlsym(handle, "plugin_init");
    if (init == 0) {
        option_error("%s has no initialization entry point", arg);
        goto errclose;
    }
    vers = (const char *) dlsym(handle, "pppd_version");
    if (vers == 0) {
        warn("Warning: plugin %s has no version information", arg);
    } else if (strcmp(vers, VERSION) != 0) {
        option_error("Plugin %s is for pppd version %s, this is %s",
                     arg, vers, VERSION);
        goto errclose;
    }
    info("Plugin %s loaded.", arg);
    (*init)();
    return 1;

 errclose:
    dlclose(handle);
 err:
    if (path != arg)
        free(path);
    return 0;
}
#endif /* PLUGIN */

/*
 * Set an environment variable specified by the user.
 */
static int
user_setenv(char **argv)
{
    char *arg = argv[0];
    char *eqp;
    struct userenv *uep, **insp;

    if ((eqp = strchr(arg, '=')) == NULL) {
        option_error("missing = in name=value: %s", arg);
        return 0;
    }
    if (eqp == arg) {
        option_error("missing variable name: %s", arg);
        return 0;
    }
    for (uep = userenv_list; uep != NULL; uep = uep->ue_next) {
        int nlen = strlen(uep->ue_name);
        if (nlen == (eqp - arg) &&
            strncmp(arg, uep->ue_name, nlen) == 0)
            break;
    }
    /* Ignore attempts by unprivileged users to override privileged sources */
    if (uep != NULL && !privileged_option && uep->ue_priv)
        return 1;
    /* The name never changes, so allocate it with the structure */
    if (uep == NULL) {
        uep = malloc(sizeof (*uep) + (eqp-arg));
        strncpy(uep->ue_name, arg, eqp-arg);
        uep->ue_name[eqp-arg] = '\0';
        uep->ue_next = NULL;
        insp = &userenv_list;
        while (*insp != NULL)
            insp = &(*insp)->ue_next;
        *insp = uep;
    } else {
        struct userenv *uep2;
        for (uep2 = userenv_list; uep2 != NULL; uep2 = uep2->ue_next) {
            if (uep2 != uep && !uep2->ue_isset)
                break;
        }
        if (uep2 == NULL && !uep->ue_isset)
            find_option("unset")->flags |= OPT_NOPRINT;
        free(uep->ue_value);
    }
    uep->ue_isset = 1;
    uep->ue_priv = privileged_option;
    uep->ue_source = option_source;
    uep->ue_value = strdup(eqp + 1);
    curopt->flags &= ~OPT_NOPRINT;
    return 1;
}

static void
user_setprint(option_t *opt, printer_func printer, void *arg)
{
    struct userenv *uep, *uepnext;

    uepnext = userenv_list;
    while (uepnext != NULL && !uepnext->ue_isset)
        uepnext = uepnext->ue_next;
    while ((uep = uepnext) != NULL) {
        uepnext = uep->ue_next;
        while (uepnext != NULL && !uepnext->ue_isset)
            uepnext = uepnext->ue_next;
        (*printer)(arg, "%s=%s", uep->ue_name, uep->ue_value);
        if (uepnext != NULL)
            (*printer)(arg, "\t\t# (from %s)\n%s ", uep->ue_source, opt->name);
        else
            opt->source = uep->ue_source;
    }
}

static int
user_unsetenv(char **argv)
{
    struct userenv *uep, **insp;
    char *arg = argv[0];

    if (strchr(arg, '=') != NULL) {
        option_error("unexpected = in name: %s", arg);
        return 0;
    }
    if (*arg == '\0') {
        option_error("missing variable name for unset");
        return 0;
    }
    for (uep = userenv_list; uep != NULL; uep = uep->ue_next) {
        if (strcmp(arg, uep->ue_name) == 0)
            break;
    }
    /* Ignore attempts by unprivileged users to override privileged sources */
    if (uep != NULL && !privileged_option && uep->ue_priv)
        return 1;
    /* The name never changes, so allocate it with the structure */
    if (uep == NULL) {
        uep = malloc(sizeof (*uep) + strlen(arg));
        strcpy(uep->ue_name, arg);
        uep->ue_next = NULL;
        insp = &userenv_list;
        while (*insp != NULL)
            insp = &(*insp)->ue_next;
        *insp = uep;
    } else {
        struct userenv *uep2;
        for (uep2 = userenv_list; uep2 != NULL; uep2 = uep2->ue_next) {
            if (uep2 != uep && uep2->ue_isset)
                break;
        }
        if (uep2 == NULL && uep->ue_isset)
            find_option("set")->flags |= OPT_NOPRINT;
        free(uep->ue_value);
    }
    uep->ue_isset = 0;
    uep->ue_priv = privileged_option;
    uep->ue_source = option_source;
    uep->ue_value = NULL;
    curopt->flags &= ~OPT_NOPRINT;
    return 1;
}

static void
user_unsetprint(option_t *opt, printer_func printer, void *arg)
{
    struct userenv *uep, *uepnext;

    uepnext = userenv_list;
    while (uepnext != NULL && uepnext->ue_isset)
        uepnext = uepnext->ue_next;
    while ((uep = uepnext) != NULL) {
        uepnext = uep->ue_next;
        while (uepnext != NULL && uepnext->ue_isset)
            uepnext = uepnext->ue_next;
        (*printer)(arg, "%s", uep->ue_name);
        if (uepnext != NULL)
            (*printer)(arg, "\t\t# (from %s)\n%s ", uep->ue_source, opt->name);
        else
            opt->source = uep->ue_source;
    }
}