/*

Copyright (c) 2004, 2005 Carl Byington - 510 Software Group, released
under the GPL version 2 or any later version at your choice available at
http://www.fsf.org/licenses/gpl.txt

Based on a sample milter Copyright (c) 2000-2003 Sendmail, Inc. and its
suppliers.  Inspired by the DCC by Rhyolite Software

-r port  The port used to talk to our internal dns resolver processes
-p port  The port through which the MTA will connect to this milter.
-t sec   The timeout value.
-c       Check the config, and print a copy to stdout. Don't start the
         milter or do anything with the socket.
-d       Add debug syslog entries


TODO:
1) Add config for max_recipients for each mail domain. Recipients in
excess of that limit will be rejected, and the entire data will be
rejected if it is sent.

2) Add config for poison addresses. If any recipient is poison, all
recipients are rejected even if they would be whitelisted, and the
data is rejected if sent.

3) Add option to only allow one recipient if the return path is empty.

4) Check if the envelope from domain name primary MX points 127.0.0.0/8

5) Add option for using smtp connections to verify addresses from backup
mx machines. This allows the backup mx to learn the valid addresses
on the primary machine.

*/


// from sendmail sample
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sysexits.h>
#include <unistd.h>

// needed for socket io
#include <sys/ioctl.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/un.h>

// needed for thread
#include <pthread.h>

// needed for std c++ collections
#include <set>
#include <map>
#include <list>

// for the dns resolver
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>

// misc stuff needed here
#include <ctype.h>
#include <fstream>
#include <syslog.h>
#include <pwd.h>

static char* dnsbl_version="$Id$";

#define DEFAULT "default"
#define WHITE   "white"
#define BLACK   "black"
#define OK      "ok"
#define MANY    "many"

enum status {oksofar,       // not rejected yet
             white,         // whitelisted by envelope from
             black,         // blacklisted by envelope from or to
             reject,        // rejected by a dns list
             reject_tag,    // too many bad html tags
             reject_host};  // too many hosts/urls in body

using namespace std;

extern "C" {
    #include "libmilter/mfapi.h"
    sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr);
    sfsistat mlfi_envfrom(SMFICTX *ctx, char **argv);
    sfsistat mlfi_envrcpt(SMFICTX *ctx, char **argv);
    sfsistat mlfi_body(SMFICTX *ctx, u_char *data, size_t len);
    sfsistat mlfi_eom(SMFICTX *ctx);
    sfsistat mlfi_abort(SMFICTX *ctx);
    sfsistat mlfi_close(SMFICTX *ctx);
}

struct ltstr {
    bool operator()(char* s1, char* s2) const {
        return strcmp(s1, s2) < 0;
    }
};

struct DNSBL {
    char    *suffix;    // blacklist suffix like blackholes.five-ten-sg.com
    char    *message;   // error message with one or two %s operators for the ip address replacement
    DNSBL(char *s, char *m);
};
DNSBL::DNSBL(char *s, char *m) {
    suffix  = s;
    message = m;
}

typedef DNSBL *                           DNSBLP;
typedef list<DNSBLP>                      DNSBLL;
typedef DNSBLL *                          DNSBLLP;
typedef map<char *, char *, ltstr>        string_map;
typedef map<char *, string_map *, ltstr>  from_map;
typedef map<char *, DNSBLP, ltstr>        dnsblp_map;
typedef map<char *, DNSBLLP, ltstr>       dnsbllp_map;
typedef set<char *, ltstr>                string_set;
typedef set<int>                          int_set;
typedef list<char *>                      string_list;
typedef map<char *, int, ltstr>           ns_mapper;

struct ns_map {
    // all the strings are owned by the keys/values in the ns_host string map
    string_map  ns_host;    // nameserver name -> host name that uses this name server
    ns_mapper   ns_ip;      // nameserver name -> ip address of the name server
};

struct CONFIG {
    // the only mutable stuff once it has been loaded from the config file
    int         reference_count;    // protected by the global config_mutex
    // all the rest is constant after loading from the config file
    int         generation;
    time_t      load_time;
    string_list config_files;
    dnsblp_map  dnsbls;
    dnsbllp_map dnsblls;
    from_map    env_from;
    string_map  env_to_dnsbll;      // map recipient to a named dnsbll
    string_map  env_to_chkfrom;     // map recipient to a named from map
    char *      content_suffix;     // for sbl url body filtering
    char *      content_message;    // ""
    string_set  content_host_ignore;// hosts to ignore for content sbl checking
    char *      host_limit_message; // error message for excessive host names
    int         host_limit;         // limit on host names
    bool        host_random;        // pick a random selection of host names rather than error for excessive hosts
    char *      tag_limit_message;  // error message for excessive bad html tags
    int         tag_limit;          // limit on bad html tags
    string_set  html_tags;          // set of valid html tags
    string_set  tlds;               // set of valid tld components
    CONFIG();
    ~CONFIG();
};
CONFIG::CONFIG() {
    reference_count    = 0;
    generation         = 0;
    load_time          = 0;
    content_suffix     = NULL;
    content_message    = NULL;
    host_limit_message = NULL;
    host_limit         = 0;
    host_random        = false;
    tag_limit_message  = NULL;
    tag_limit          = 0;
}
CONFIG::~CONFIG() {
    for (dnsblp_map::iterator i=dnsbls.begin(); i!=dnsbls.end(); i++) {
        DNSBLP d = (*i).second;
        // delete the underlying DNSBL objects.
        delete d;
    }
    for (dnsbllp_map::iterator i=dnsblls.begin(); i!=dnsblls.end(); i++) {
        DNSBLLP d = (*i).second;
        // *d is a list of pointers to DNSBL objects, but
        // the underlying objects have already been deleted above.
        delete d;
    }
    for (from_map::iterator i=env_from.begin(); i!=env_from.end(); i++) {
        string_map *d = (*i).second;
        delete d;
    }
}

static bool debug_syslog = false;
static bool loader_run   = true;    // used to stop the config loader thread
static string_set all_strings;      // owns all the strings, only modified by the config loader thread
static CONFIG * config = NULL;      // protected by the config_mutex
static int  generation = 0;         // protected by the config_mutex

static pthread_mutex_t  config_mutex;
static pthread_mutex_t  syslog_mutex;
static pthread_mutex_t  resolve_mutex;
static pthread_mutex_t  fd_pool_mutex;

static std::set<int>    fd_pool;
static int    NULL_SOCKET       = -1;
static char  *resolver_port     = NULL;         // unix domain socket to talk to the dns resolver process
static int    resolver_socket   = NULL_SOCKET;  // socket used to listen for resolver requests
static time_t ERROR_SOCKET_TIME = 60;           // number of seconds between attempts to open the spam filter socket
static time_t last_error_time;
static int    resolver_sock_count = 0;          // protected with fd_pool_mutex
static int    resolver_pool_size  = 0;          // protected with fd_pool_mutex


// packed structure to allow a single socket write to dump the
// length and the following answer. The packing attribute is gcc specific.
struct glommer {
    int    length;
    #ifdef NS_PACKETSZ
        u_char answer[NS_PACKETSZ];     // with a resolver, we return resolver answers
    #else
        int    answer;                  // without a resolver, we return a single ip4 address, 0 == no answer
    #endif
} __attribute__ ((packed));

struct mlfiPriv;


////////////////////////////////////////////////
// helper to discard the strings and objects held by an ns_map
//
static void discard(ns_map &s);
static void discard(ns_map &s) {
    for (string_map::iterator i=s.ns_host.begin(); i!=s.ns_host.end(); i++) {
        char *x = (*i).first;
        char *y = (*i).second;
        free(x);
        free(y);
    }
    s.ns_ip.clear();
    s.ns_host.clear();
}

////////////////////////////////////////////////
// helper to register a string in an ns_map
//
static void register_string(ns_map &s, char *name, char *refer);
static void register_string(ns_map &s, char *name, char *refer) {
    string_map::iterator i = s.ns_host.find(name);
    if (i != s.ns_host.end()) return;
    char *x = strdup(name);
    char *y = strdup(refer);
    s.ns_ip[x]   = 0;
    s.ns_host[x] = y;

}

////////////////////////////////////////////////
// helper to discard the strings held by a string_set
//
static void discard(string_set &s);
static void discard(string_set &s) {
    for (string_set::iterator i=s.begin(); i!=s.end(); i++) {
        free(*i);
    }
    s.clear();
}

////////////////////////////////////////////////
// helper to register a string in a string set
//
static char* register_string(string_set &s, char *name);
static char* register_string(string_set &s, char *name) {
    string_set::iterator i = s.find(name);
    if (i != s.end()) return *i;
    char *x = strdup(name);
    s.insert(x);
    return x;
}

////////////////////////////////////////////////
// syslog a message
//
static void my_syslog(mlfiPriv *priv, char *text);


// include the content scanner
#include "scanner.cpp"


////////////////////////////////////////////////
// disconnect the fd from the dns resolver process
//
void my_disconnect(int sock);
void my_disconnect(int sock)
{
    if (sock != NULL_SOCKET) {
        pthread_mutex_lock(&fd_pool_mutex);
            resolver_sock_count--;
        pthread_mutex_unlock(&fd_pool_mutex);
        shutdown(sock, SHUT_RDWR);
        close(sock);
    }
}


////////////////////////////////////////////////
// return fd connected to the dns resolver process
//
int my_connect();
int my_connect()
{
    // if we have had recent errors, don't even try to open the socket
    time_t now = time(NULL);
    if ((now - last_error_time) < ERROR_SOCKET_TIME) return NULL_SOCKET;

    // nothing recent, maybe this time it will work
    int sock = NULL_SOCKET;
    sockaddr_un server;
    memset(&server, '\0', sizeof(server));
    server.sun_family = AF_UNIX;
    strncpy(server.sun_path, resolver_port, sizeof(server.sun_path)-1);
    sock = socket(AF_UNIX, SOCK_STREAM, 0);
    if (sock != NULL_SOCKET) {
        bool rc = (connect(sock, (sockaddr *)&server, sizeof(server)) == 0);
        if (!rc) {
            my_disconnect(sock);
            sock = NULL_SOCKET;
            last_error_time = now;
        }
    }
    else last_error_time = now;
    if (sock != NULL_SOCKET) {
        pthread_mutex_lock(&fd_pool_mutex);
            resolver_sock_count++;
        pthread_mutex_unlock(&fd_pool_mutex);
    }
    return sock;
}


////////////////////////////////////////////////
// mail filter private data, held for us by sendmail
//
struct mlfiPriv
{
    // connection specific data
    CONFIG  *pc;                    // global context with our maps
    int     fd;                     // to talk to dns resolvers process
    bool    err;                    // did we get any errors on the resolver socket?
    int     ip;                     // ip4 address of the smtp client
    map<DNSBLP, status> checked;    // status from those lists
    // message specific data
    char    *mailaddr;      // envelope from value
    char    *queueid;       // sendmail queue id
    bool    authenticated;  // client authenticated? if so, suppress all dnsbl checks
    bool    have_whites;    // have at least one whitelisted recipient? need to accept content and remove all non-whitelisted recipients if it fails
    bool    only_whites;    // every recipient is whitelisted?
    string_set  non_whites; // remember the non-whitelisted recipients so we can remove them if need be
    recorder    *memory;    // memory for the content scanner
    url_scanner *scanner;   // object to handle body scanning
    mlfiPriv();
    ~mlfiPriv();
    void reset(bool final = false); // for a new message
    void get_fd();
    void return_fd();
    int  my_read(char *buf, int len);
    int  my_write(char *buf, int len);
};

mlfiPriv::mlfiPriv() {
    pthread_mutex_lock(&config_mutex);
        pc = config;
        pc->reference_count++;
    pthread_mutex_unlock(&config_mutex);
    get_fd();
    ip            = 0;
    mailaddr      = NULL;
    queueid       = NULL;
    authenticated = false;
    have_whites   = false;
    only_whites   = true;
    memory        = new recorder(this, &pc->html_tags, &pc->tlds);
    scanner       = new url_scanner(memory);
}

mlfiPriv::~mlfiPriv() {
    return_fd();
    pthread_mutex_lock(&config_mutex);
        pc->reference_count--;
    pthread_mutex_unlock(&config_mutex);
    reset(true);
}

void mlfiPriv::reset(bool final) {
    if (mailaddr) free(mailaddr);
    if (queueid)  free(queueid);
    discard(non_whites);
    delete memory;
    delete scanner;
    if (!final) {
        mailaddr      = NULL;
        queueid       = NULL;
        authenticated = false;
        have_whites   = false;
        only_whites   = true;
        memory        = new recorder(this, &pc->html_tags, &pc->tlds);
        scanner       = new url_scanner(memory);
    }
}

void mlfiPriv::get_fd()
{
    err = true;
    fd  = NULL_SOCKET;
    int result = pthread_mutex_lock(&fd_pool_mutex);
    if (!result) {
        std::set<int>::iterator i;
        i = fd_pool.begin();
        if (i != fd_pool.end()) {
            // have at least one fd in the pool
            err = false;
            fd  = *i;
            fd_pool.erase(fd);
            resolver_pool_size--;
        }
        else {
            // pool is empty, get a new fd
            fd  = my_connect();
            err = (fd == NULL_SOCKET);
        }
        pthread_mutex_unlock(&fd_pool_mutex);
    }
    else {
        // cannot lock the pool, just get a new fd
        fd  = my_connect();
        err = (fd == NULL_SOCKET);
    }
}

void mlfiPriv::return_fd()
{
    if (err) {
        // this fd got a socket error, so close it, rather than returning it to the pool
        my_disconnect(fd);
    }
    else {
        int result = pthread_mutex_lock(&fd_pool_mutex);
        if (!result) {
            if (resolver_sock_count > resolver_pool_size*5) {
                // return the fd to the pool
                fd_pool.insert(fd);
                resolver_pool_size++;
            }
            else {
                // more than 20% of the open resolver sockets are in the pool
                // that is enough, so just close this one.
                my_disconnect(fd);
            }
            pthread_mutex_unlock(&fd_pool_mutex);
        }
        else {
            // could not lock the pool, so just close the fd
            my_disconnect(fd);
        }
    }
}

int mlfiPriv::my_write(char *buf, int len)
{
    if (err) return 0;
    int rs = 0;
    while (len) {
        int ws = write(fd, buf, len);
        if (ws > 0) {
            rs  += ws;
            len -= ws;
            buf += ws;
        }
        else {
            // peer closed the socket!
            rs = 0;
            err = true;
            break;
        }
    }
    return rs;
}

int mlfiPriv::my_read(char *buf, int len)
{
    if (err) return 0;
    int rs = 0;
    while (len > 1) {
        int ws = read(fd, buf, len);
        if (ws > 0) {
            rs  += ws;
            len -= ws;
            buf += ws;
        }
        else {
            // peer closed the socket!
            rs = 0;
            err = true;
            break;
        }
    }
    return rs;
}

#define MLFIPRIV    ((struct mlfiPriv *) smfi_getpriv(ctx))


////////////////////////////////////////////////
// syslog a message
//
static void my_syslog(mlfiPriv *priv, char *text) {
    char buf[1000];
    if (priv) {
        snprintf(buf, sizeof(buf), "%s: %s", priv->queueid, text);
        text = buf;
    }
    pthread_mutex_lock(&syslog_mutex);
        openlog("dnsbl", LOG_PID, LOG_MAIL);
        syslog(LOG_NOTICE, "%s", text);
        closelog();
    pthread_mutex_unlock(&syslog_mutex);
}

static void my_syslog(char *text);
static void my_syslog(char *text) {
    my_syslog(NULL, text);
}

////////////////////////////////////////////////
// register a global string
//
static char* register_string(char *name);
static char* register_string(char *name) {
    return register_string(all_strings, name);
}


static char* next_token(char *delim);
static char* next_token(char *delim) {
    char *name = strtok(NULL, delim);
    if (!name) return name;
    return register_string(name);
}


////////////////////////////////////////////////
// lookup an email address in the env_from or env_to maps
//
static char* lookup1(char *email, string_map map);
static char* lookup1(char *email, string_map map) {
    string_map::iterator i = map.find(email);
    if (i != map.end()) return (*i).second;
    char *x = strchr(email, '@');
    if (!x) return DEFAULT;
    x++;
    i = map.find(x);
    if (i != map.end()) return (*i).second;
    return DEFAULT;
}


////////////////////////////////////////////////
// lookup an email address in the env_from or env_to maps
// this email address is passed in from sendmail, and will
// always be enclosed in <>. It may have mixed case, just
// as the mail client sent it.
//
static char* lookup(char* email, string_map map);
static char* lookup(char* email, string_map map) {
    int n = strlen(email)-2;
    if (n < 1) return DEFAULT;  // malformed
    char *key = strdup(email+1);
    key[n] = '\0';
    for (int i=0; i<n; i++) key[i] = tolower(key[i]);
    char *rc = lookup1(key, map);
    free(key);
    return rc;
}


////////////////////////////////////////////////
//  find the dnsbl with a specific name
//
static DNSBLP find_dnsbl(CONFIG &dc, char *name);
static DNSBLP find_dnsbl(CONFIG &dc, char *name) {
    dnsblp_map::iterator i = dc.dnsbls.find(name);
    if (i == dc.dnsbls.end()) return NULL;
    return (*i).second;
}


////////////////////////////////////////////////
//  find the dnsbll with a specific name
//
static DNSBLLP find_dnsbll(CONFIG &dc, char *name);
static DNSBLLP find_dnsbll(CONFIG &dc, char *name) {
    dnsbllp_map::iterator i = dc.dnsblls.find(name);
    if (i == dc.dnsblls.end()) return NULL;
    return (*i).second;
}


////////////////////////////////////////////////
//  find the envfrom map with a specific name
//
static string_map* find_from_map(CONFIG &dc, char *name);
static string_map* find_from_map(CONFIG &dc, char *name) {
    from_map::iterator i = dc.env_from.find(name);
    if (i == dc.env_from.end()) return NULL;
    return (*i).second;
}


static string_map& really_find_from_map(CONFIG &dc, char *name);
static string_map& really_find_from_map(CONFIG &dc, char *name) {
    string_map *sm = find_from_map(dc, name);
    if (!sm) {
        sm = new string_map;
        dc.env_from[name] = sm;
    }
    return *sm;
}



////////////////////////////////////////////////
//  read a resolver request from the socket, process it, and
//  write the result back to the socket.

static void process_resolver_requests(int socket);
static void process_resolver_requests(int socket) {
#ifdef NS_MAXDNAME
    char question[NS_MAXDNAME];
#else
    char question[1000];
#endif
    glommer glom;

    int maxq = sizeof(question);
    while (true) {
        // read a question
        int rs = 0;
        while (true) {
            int ns = read(socket, question+rs, maxq-rs);
            if (ns > 0) {
                rs += ns;
                if (question[rs-1] == '\0') {
                    // last byte read was the null terminator, we are done
                    break;
                }
            }
            else {
                // peer closed the socket
              //my_syslog("!!child worker process, peer closed socket while reading question");
                shutdown(socket, SHUT_RDWR);
                close(socket);
                return;
            }
        }

        // find the answer
#ifdef NS_PACKETSZ
      //char text[1000];
      //snprintf(text, sizeof(text), "!!child worker process has a question %s", question);
      //my_syslog(text);
        glom.length = res_search(question, ns_c_in, ns_t_a, glom.answer, sizeof(glom.answer));
        if (glom.length < 0) glom.length = 0;   // represent all errors as zero length answers
#else
        glom.length = sizeof(glom.answer);
        glom.answer = 0;
        struct hostent *host = gethostbyname(question);
        if (host && (host->h_addrtype == AF_INET)) {
            memcpy(&glom.answer, host->h_addr, sizeof(glom.answer));
        }
#endif

        // write the answer
        char *buf = (char *)&glom;
        int   len = glom.length + sizeof(glom.length);
      //snprintf(text, sizeof(text), "!!child worker process writing answer length %d for total %d", glom.length, len);
      //my_syslog(text);
        int    ws = 0;
        while (len > ws) {
            int ns = write(socket, buf+ws, len-ws);
            if (ns > 0) {
                ws += ns;
            }
            else {
                // peer closed the socket!
              //my_syslog("!!child worker process, peer closed socket while writing answer");
                shutdown(socket, SHUT_RDWR);
                close(socket);
                return;
            }
        }
    }
}


////////////////////////////////////////////////
//  ask a dns question and get an A record answer - we don't try
//  very hard, just using the default resolver retry settings.
//  If we cannot get an answer, we just accept the mail.
//
//
static int dns_interface(mlfiPriv &priv, char *question, bool maybe_ip, ns_map *nameservers);
static int dns_interface(mlfiPriv &priv, char *question, bool maybe_ip, ns_map *nameservers) {
    // this part can be done without locking the resolver mutex. Each
    // milter thread is talking over its own socket to a separate resolver
    // process, which does the actual dns resolution.
    if (priv.err) return 0; // cannot ask more questions on this socket.
    priv.my_write(question, strlen(question)+1);   // write the question including the null terminator
    glommer glom;
    char *buf = (char *)&glom;
    priv.my_read(buf, sizeof(glom.length));
    buf += sizeof(glom.length);
 ///char text[1000];
 ///snprintf(text, sizeof(text), "!!milter thread wrote question %s and has answer length %d", question, glom.length);
 ///my_syslog(text);
    if ((glom.length < 0) || (glom.length > sizeof(glom.answer))) {
        priv.err = true;
        return 0;  // cannot process overlarge answers
    }
    priv.my_read(buf, glom.length);

#ifdef NS_PACKETSZ
    // now we need to lock the resolver mutex to keep the milter threads from
    // stepping on each other while parsing the dns answer.
    int ret_address = 0;
    pthread_mutex_lock(&resolve_mutex);
        if (glom.length > 0) {
            // parse the answer
            ns_msg handle;
            ns_rr  rr;
            if (ns_initparse(glom.answer, glom.length, &handle) == 0) {
                // look for ns names
                if (nameservers) {
                    ns_map &ns = *nameservers;
                    int rrnum = 0;
                    while (ns_parserr(&handle, ns_s_ns, rrnum++, &rr) == 0) {
                        if (ns_rr_type(rr) == ns_t_ns) {
                            char nam[NS_MAXDNAME+1];
                            char         *n = nam;
                            const u_char *p = ns_rr_rdata(rr);
                            while (((n-nam) < NS_MAXDNAME) && ((p-glom.answer) < glom.length) && *p) {
                                size_t s = *(p++);
                                if (s > 191) {
                                    // compression pointer
                                    s = (s-192)*256 + *(p++);
                                    if (s >= glom.length) break; // pointer outside bounds of answer
                                    p = glom.answer + s;
                                    s = *(p++);
                                }
                                if (s > 0) {
                                    if ((n-nam)         >= (NS_MAXDNAME-s)) break;  // destination would overflow name buffer
                                    if ((p-glom.answer) >= (glom.length-s)) break;  // source outside bounds of answer
                                    memcpy(n, p, s);
                                    n += s;
                                    p += s;
                                    *(n++) = '.';
                                }
                            }
                            if (n-nam) n--;             // remove trailing .
                            *n = '\0';                  // null terminate it
                            register_string(ns, nam, question);     // ns host to lookup later
                        }
                    }
                    rrnum = 0;
                    while (ns_parserr(&handle, ns_s_ar, rrnum++, &rr) == 0) {
                        if (ns_rr_type(rr) == ns_t_a) {
                            char* nam = (char*)ns_rr_name(rr);
                            ns_mapper::iterator i = ns.ns_ip.find(nam);
                            if (i != ns.ns_ip.end()) {
                                // we want this ip address
                                int address;
                                memcpy(&address, ns_rr_rdata(rr), sizeof(address));
                                ns.ns_ip[nam] = address;
                            }
                        }
                    }
                }
                int rrnum = 0;
                while (ns_parserr(&handle, ns_s_an, rrnum++, &rr) == 0) {
                    if (ns_rr_type(rr) == ns_t_a) {
                        int address;
                        memcpy(&address, ns_rr_rdata(rr), sizeof(address));
                        ret_address = address;
                    }
                }
            }
        }
        if (maybe_ip && !ret_address) {
            // might be a bare ip address
            in_addr ip;
            if (inet_aton(question, &ip)) {
                ret_address = ip.s_addr;
            }
        }
    pthread_mutex_unlock(&resolve_mutex);
    return ret_address;
#else
    return glom.answer;
#endif
}


////////////////////////////////////////////////
//  check a single dnsbl
//
static status check_single(mlfiPriv &priv, int ip, char *suffix);
static status check_single(mlfiPriv &priv, int ip, char *suffix) {
    // make a dns question
    const u_char *src = (const u_char *)&ip;
    if (src[0] == 127) return oksofar;  // don't do dns lookups on localhost
#ifdef NS_MAXDNAME
    char question[NS_MAXDNAME];
#else
    char question[1000];
#endif
    snprintf(question, sizeof(question), "%u.%u.%u.%u.%s.", src[3], src[2], src[1], src[0], suffix);
    // ask the question, if we get an A record it implies a blacklisted ip address
    return (dns_interface(priv, question, false, NULL)) ? reject : oksofar;
}


////////////////////////////////////////////////
//  check a single dnsbl
//
static status check_single(mlfiPriv &priv, int ip, DNSBL &bl);
static status check_single(mlfiPriv &priv, int ip, DNSBL &bl) {
    return check_single(priv, ip, bl.suffix);
}


////////////////////////////////////////////////
//  check the dnsbls specified for this recipient
//
static status check_dnsbl(mlfiPriv &priv, DNSBLLP dnsbllp, DNSBLP &rejectlist);
static status check_dnsbl(mlfiPriv &priv, DNSBLLP dnsbllp, DNSBLP &rejectlist) {
    if (priv.authenticated) return oksofar;
    if (!dnsbllp)           return oksofar;
    DNSBLL &dnsbll = *dnsbllp;
    for (DNSBLL::iterator i=dnsbll.begin(); i!=dnsbll.end(); i++) {
        DNSBLP dp = *i;     // non null by construction
        status st;
        map<DNSBLP, status>::iterator f = priv.checked.find(dp);
        if (f == priv.checked.end()) {
            // have not checked this list yet
            st = check_single(priv, priv.ip, *dp);
            rejectlist = dp;
            priv.checked[dp] = st;
        }
        else {
            st = (*f).second;
            rejectlist = (*f).first;
        }
        if (st == reject) return st;
    }
    return oksofar;
}


////////////////////////////////////////////////
//  check the hosts from the body against the content dnsbl
//
static status check_hosts(mlfiPriv &priv, char *&host, int &ip);
static status check_hosts(mlfiPriv &priv, char *&host, int &ip) {
    CONFIG &dc = *priv.pc;
    int count = 0;
    ns_map nameservers;
    bool ran = priv.pc->host_random;
    int  lim = priv.pc->host_limit;         // we should not look at more than this many hosts
    int  cnt = priv.memory->hosts.size();   // number of hosts we could look at
    int_set ips;    // remove duplicate ip addresses
    for (string_set::iterator i=priv.memory->hosts.begin(); i!=priv.memory->hosts.end(); i++) {
        host = *i;  // a reference into priv.memory->hosts, which will live until this smtp transaction is closed

        // don't bother looking up hosts on the ignore list
        string_set::iterator j = priv.pc->content_host_ignore.find(host);
        if (j != priv.pc->content_host_ignore.end()) continue;

        // try to only look at lim/cnt fraction of the available cnt host names in random mode
        if ((cnt > lim) && (lim > 0) && ran) {
            int r = rand() % cnt;
            if (r >= lim) {
                char buf[1000];
                snprintf(buf, sizeof(buf), "host %s skipped", host);
                my_syslog(&priv, buf);
                continue;
            }
        }
        count++;
        if ((count > lim) && (lim > 0) && (!ran)) {
            discard(nameservers);
            return reject_host;
        }
        ip = dns_interface(priv, host, true, &nameservers);
        if (debug_syslog) {
            char buf[1000];
            if (ip) {
                char adr[sizeof "255.255.255.255"];
                adr[0] = '\0';
                inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr));
                snprintf(buf, sizeof(buf), "host %s found at %s", host, adr);
            }
            else {
                snprintf(buf, sizeof(buf), "host %s not found", host);
            }
            my_syslog(&priv, buf);
        }
        if (ip) {
            int_set::iterator i = ips.find(ip);
            if (i == ips.end()) {
                ips.insert(ip);
                status st = check_single(priv, ip, dc.content_suffix);
                if (st == reject) {
                    discard(nameservers);
                    return st;
                }
            }
        }
    }
    lim *= 4;   // allow average of 3 ns per host name
    for (ns_mapper::iterator i=nameservers.ns_ip.begin(); i!=nameservers.ns_ip.end(); i++) {
        count++;
        if ((count > lim) && (lim > 0)) {
            if (ran) continue; // don't complain
            discard(nameservers);
            return reject_host;
        }
        host = (*i).first;  // a transient reference that needs to be replaced before we return it
        ip   = (*i).second;
        if (!ip) ip = dns_interface(priv, host, false, NULL);
        if (debug_syslog) {
            char buf[200];
            if (ip) {
                char adr[sizeof "255.255.255.255"];
                adr[0] = '\0';
                inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr));
                snprintf(buf, sizeof(buf), "ns %s found at %s", host, adr);
            }
            else {
                snprintf(buf, sizeof(buf), "ns %s not found", host);
            }
            my_syslog(&priv, buf);
        }
        if (ip) {
            int_set::iterator i = ips.find(ip);
            if (i == ips.end()) {
                ips.insert(ip);
                status st = check_single(priv, ip, dc.content_suffix);
                if (st == reject) {
                    string_map::iterator j = nameservers.ns_host.find(host);
                    if (j != nameservers.ns_host.end()) {
                        char *refer = (*j).second;
                        char buf[1000];
                        snprintf(buf, sizeof(buf), "%s with nameserver %s", refer, host);
                        host = register_string(priv.memory->hosts, buf);    // put a copy into priv.memory->hosts, and return that reference
                    }
                    else {
                        host = register_string(priv.memory->hosts, host);   // put a copy into priv.memory->hosts, and return that reference
                    }
                    discard(nameservers);
                    return st;
                }
            }
        }
    }
    discard(nameservers);
    host = NULL;
    int bin = priv.memory->binary_tags;
    int bad = priv.memory->bad_html_tags;
    lim = priv.pc->tag_limit;
    if (3*bin > bad) return oksofar;    // probably .zip or .tar.gz with random content
    if ((bad > lim) && (lim > 0)) return reject_tag;
    return oksofar;
}


////////////////////////////////////////////////
// start of sendmail milter interfaces
//
sfsistat mlfi_connect(SMFICTX *ctx, char *hostname, _SOCK_ADDR *hostaddr)
{
    // allocate some private memory
    mlfiPriv *priv = new mlfiPriv;
    if (hostaddr->sa_family == AF_INET) {
        priv->ip = ((struct sockaddr_in *)hostaddr)->sin_addr.s_addr;
    }

    // save the private data
    smfi_setpriv(ctx, (void*)priv);

    // continue processing
    return SMFIS_CONTINUE;
}

sfsistat mlfi_envfrom(SMFICTX *ctx, char **from)
{
    mlfiPriv &priv = *MLFIPRIV;
    priv.mailaddr      = strdup(from[0]);
    priv.authenticated = (smfi_getsymval(ctx, "{auth_authen}") != NULL);
    return SMFIS_CONTINUE;
}

sfsistat mlfi_envrcpt(SMFICTX *ctx, char **rcpt)
{
    DNSBLP rejectlist = NULL;   // list that caused the reject
    status st = oksofar;
    mlfiPriv &priv = *MLFIPRIV;
    CONFIG &dc = *priv.pc;
    if (!priv.queueid) priv.queueid = strdup(smfi_getsymval(ctx, "i"));
    char *rcptaddr = rcpt[0];
    char *dnsname  = lookup(rcptaddr, dc.env_to_dnsbll);
    char *fromname = lookup(rcptaddr, dc.env_to_chkfrom);
    if ((strcmp(dnsname,  BLACK) == 0) ||
        (strcmp(fromname, BLACK) == 0)) {
        st = black; // two options to blacklist this recipient
    }
    else if (strcmp(fromname, WHITE) == 0) {
        st = white;
    }
    else {
        // check an env_from map
        string_map *sm = find_from_map(dc, fromname);
        if (sm != NULL) {
            fromname = lookup(priv.mailaddr, *sm);  // returns default if name not in map
            if (strcmp(fromname, BLACK) == 0) {
                st = black; // blacklist this envelope from value
            }
            if (strcmp(fromname, WHITE) == 0) {
                st = white; // blacklist this envelope from value
            }
        }
    }
    if ((st == oksofar) && (strcmp(dnsname, WHITE) != 0)) {
        // check dns lists
        st = check_dnsbl(priv, find_dnsbll(dc, dnsname), rejectlist);
    }

    if (st == reject) {
        // reject the recipient based on some dnsbl
        char adr[sizeof "255.255.255.255"];
        adr[0] = '\0';
        inet_ntop(AF_INET, (const u_char *)&priv.ip, adr, sizeof(adr));
        char buf[2000];
        snprintf(buf, sizeof(buf), rejectlist->message, adr, adr);
        smfi_setreply(ctx, "550", "5.7.1", buf);
        return SMFIS_REJECT;
    }
    else if (st == black) {
        // reject the recipient based on blacklisting either from or to
        smfi_setreply(ctx, "550", "5.7.1", "no such user");
        return SMFIS_REJECT;
    }
    else {
        // accept the recipient
        if (st == oksofar) {
            // but remember the non-whites
            register_string(priv.non_whites, rcptaddr);
            priv.only_whites = false;
        }
        if (st == white) {
            priv.have_whites = true;
        }
        return SMFIS_CONTINUE;
    }
}

sfsistat mlfi_body(SMFICTX *ctx, u_char *data, size_t len)
{
    mlfiPriv &priv = *MLFIPRIV;
    if (priv.authenticated)       return SMFIS_CONTINUE;
    if (priv.only_whites)         return SMFIS_CONTINUE;
    if (!priv.pc->content_suffix) return SMFIS_CONTINUE;
    priv.scanner->scan(data, len);
    return SMFIS_CONTINUE;
}

sfsistat mlfi_eom(SMFICTX *ctx)
{
    sfsistat  rc;
    mlfiPriv &priv = *MLFIPRIV;
    char     *host = NULL;
    int       ip;
    status    st;
    // process end of message
    if (priv.authenticated         ||
        priv.only_whites           ||
        (!priv.pc->content_suffix) ||
        ((st=check_hosts(priv, host, ip)) == oksofar)) rc = SMFIS_CONTINUE;
    else {
        if (!priv.have_whites) {
            // can reject the entire message
            char buf[2000];
            if (st == reject_tag) {
                // rejected due to excessive bad html tags
                snprintf(buf, sizeof(buf), priv.pc->tag_limit_message);
            }
            else if (st == reject_host) {
                // rejected due to excessive unique host/urls
                snprintf(buf, sizeof(buf), priv.pc->host_limit_message);
            }
            else {
                char adr[sizeof "255.255.255.255"];
                adr[0] = '\0';
                inet_ntop(AF_INET, (const u_char *)&ip, adr, sizeof(adr));
                snprintf(buf, sizeof(buf), priv.pc->content_message, host, adr);
            }
            smfi_setreply(ctx, "550", "5.7.1", buf);
            rc = SMFIS_REJECT;
        }
        else {
            // need to accept it but remove the recipients that don't want it
            for (string_set::iterator i=priv.non_whites.begin(); i!=priv.non_whites.end(); i++) {
                char *rcpt = *i;
                smfi_delrcpt(ctx, rcpt);
            }
            rc = SMFIS_CONTINUE;
        }
    }
    // reset for a new message on the same connection
    mlfi_abort(ctx);
    return rc;
}

sfsistat mlfi_abort(SMFICTX *ctx)
{
    mlfiPriv &priv = *MLFIPRIV;
    priv.reset();
    return SMFIS_CONTINUE;
}

sfsistat mlfi_close(SMFICTX *ctx)
{
    mlfiPriv *priv = MLFIPRIV;
    if (!priv) return SMFIS_CONTINUE;
    delete priv;
    smfi_setpriv(ctx, NULL);
    return SMFIS_CONTINUE;
}

struct smfiDesc smfilter =
{
    "DNSBL",            // filter name
    SMFI_VERSION,       // version code -- do not change
    SMFIF_DELRCPT,      // flags
    mlfi_connect,       // connection info filter
    NULL,               // SMTP HELO command filter
    mlfi_envfrom,       // envelope sender filter
    mlfi_envrcpt,       // envelope recipient filter
    NULL,               // header filter
    NULL,               // end of header
    mlfi_body,          // body block filter
    mlfi_eom,           // end of message
    mlfi_abort,         // message aborted
    mlfi_close,         // connection cleanup
};


static void dumpit(char *name, string_map map);
static void dumpit(char *name, string_map map) {
    fprintf(stdout, "\n");
    for (string_map::iterator i=map.begin(); i!=map.end(); i++) {
        fprintf(stdout, "%s %s->%s\n", name, (*i).first, (*i).second);
    }
}


static void dumpit(from_map map);
static void dumpit(from_map map) {
    for (from_map::iterator i=map.begin(); i!=map.end(); i++) {
        char buf[2000];
        snprintf(buf, sizeof(buf), "envelope from map for %s", (*i).first);
        string_map *sm = (*i).second;
        dumpit(buf, *sm);
    }
}


static void dumpit(CONFIG &dc);
static void dumpit(CONFIG &dc) {
    dumpit(dc.env_from);
    dumpit("envelope to (dnsbl list)", dc.env_to_dnsbll);
    dumpit("envelope to (from map)", dc.env_to_chkfrom);
    fprintf(stdout, "\ndnsbls\n");
    for (dnsblp_map::iterator i=dc.dnsbls.begin(); i!=dc.dnsbls.end(); i++) {
        fprintf(stdout, "%s %s %s\n", (*i).first, (*i).second->suffix, (*i).second->message);
    }
    fprintf(stdout, "\ndnsbl_lists\n");
    for (dnsbllp_map::iterator i=dc.dnsblls.begin(); i!=dc.dnsblls.end(); i++) {
        char *name = (*i).first;
        DNSBLL &dl = *((*i).second);
        fprintf(stdout, "%s", name);
        for (DNSBLL::iterator j=dl.begin(); j!=dl.end(); j++) {
            DNSBL &d = **j;
            fprintf(stdout, " %s", d.suffix);
        }
        fprintf(stdout, "\n");
    }
    if (dc.content_suffix) {
        fprintf(stdout, "\ncontent filtering enabled with %s %s\n", dc.content_suffix, dc.content_message);
    }
    for (string_set::iterator i=dc.content_host_ignore.begin(); i!=dc.content_host_ignore.end(); i++) {
        fprintf(stdout, "ignore %s\n", (*i));
    }
    if (dc.host_limit && !dc.host_random) {
        fprintf(stdout, "\ncontent filtering for host names hard limit %d %s\n", dc.host_limit, dc.host_limit_message);
    }
    if (dc.host_limit && dc.host_random) {
        fprintf(stdout, "\ncontent filtering for host names soft limit %d\n", dc.host_limit);
    }
    if (dc.tag_limit) {
        fprintf(stdout, "\ncontent filtering for excessive html tags enabled with limit %d %s\n", dc.tag_limit, dc.tag_limit_message);
    }
    fprintf(stdout, "\nfiles\n");
    for (string_list::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
        char *f = *i;
        fprintf(stdout, "config includes %s\n", f);
    }
}


////////////////////////////////////////////////
//  check for redundant or recursive include files
//
static bool ok_to_include(CONFIG &dc, char *fn);
static bool ok_to_include(CONFIG &dc, char *fn) {
    if (!fn) return false;
    bool ok = true;
    for (string_list::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
        char *f = *i;
        if (strcmp(f, fn) == 0) {
            my_syslog("redundant or recursive include file detected");
            ok = false;
            break;
        }
    }
    return ok;
}


////////////////////////////////////////////////
//  load a single config file
//
static void load_conf_dcc(CONFIG &dc, char *name, char *fn);
static void load_conf_dcc(CONFIG &dc, char *name, char *fn) {
    ifstream is(fn);
    if (is.fail()) {
        char buf[1000];
        snprintf(buf, sizeof(buf), "include file %s not found", fn);
        my_syslog(buf);
        return;
    }
    dc.config_files.push_back(fn);
    const int LINE_SIZE = 2000;
    char line[LINE_SIZE];
    char *list  = BLACK;
    char *delim = " \t";
    int curline = 0;
    while (!is.eof()) {
        is.getline(line, LINE_SIZE);
        curline++;
        int n = strlen(line);
        if (!n) continue;
        for (int i=0; i<n; i++) line[i] = tolower(line[i]);
        if (line[0] == '#') continue;
        char *head = line;
        if (strspn(line, delim) == 0) {
            // have a leading ok/many tag to fetch
            char *cmd = strtok(line, delim);
                 if (strcmp(cmd, MANY) == 0) list = BLACK;
            else if (strcmp(cmd, OK) == 0)   list = WHITE;
            head = cmd + strlen(cmd) + 1;
        }
        char *cmd = strtok(head, delim);
        if (!cmd) continue;
        if (strcmp(cmd, "env_from") == 0) {
            char *from = next_token(delim);
            if (from) {
                string_map &fm = really_find_from_map(dc, name);
                fm[from] = list;
            }
        }
        else if (strcmp(cmd, "env_to") == 0) {
            char *to = next_token(delim);
            if (to) {
                dc.env_to_dnsbll[to]  = list;
                dc.env_to_chkfrom[to] = list;
            }
        }
        else if (strcmp(cmd, "substitute") == 0) {
            char *tag = next_token(delim);
            if (tag && (strcmp(tag, "mail_host") == 0)) {
                char *from = next_token(delim);
                if (from) {
                    string_map &fm = really_find_from_map(dc, name);
                    fm[from] = list;
                }
            }
        }
        else if (strcmp(cmd, "include") == 0) {
            char *fn = next_token(delim);
            if (ok_to_include(dc, fn)) {
                load_conf_dcc(dc, name, fn);
            }
        }

    }
    is.close();
}


static void load_conf(CONFIG &dc, char *fn);
static void load_conf(CONFIG &dc, char *fn) {
    ifstream is(fn);
    if (is.fail()) {
        char buf[1000];
        snprintf(buf, sizeof(buf), "include file %s not found", fn);
        my_syslog(buf);
        return;
    }
    dc.config_files.push_back(fn);
    map<char*, int, ltstr> commands;
    enum {dummy, tld, content, ignore, hostlimit, hostslimit, htmllimit, htmltag, dnsbl, dnsbll, envfrom, envto, include, includedcc};
    commands["tld"            ] = tld;
    commands["content"        ] = content;
    commands["ignore"         ] = ignore;
    commands["host_limit"     ] = hostlimit;
    commands["host_soft_limit"] = hostslimit;
    commands["html_limit"     ] = htmllimit;
    commands["html_tag"       ] = htmltag;
    commands["dnsbl"          ] = dnsbl;
    commands["dnsbl_list"     ] = dnsbll;
    commands["env_from"       ] = envfrom;
    commands["env_to"         ] = envto;
    commands["include"        ] = include;
    commands["include_dcc"    ] = includedcc;
    const int LINE_SIZE = 2000;
    char line[LINE_SIZE];
    char orig[LINE_SIZE];
    char *delim = " \t";
    int curline = 0;
    while (!is.eof()) {
        is.getline(line, LINE_SIZE);
        snprintf(orig, sizeof(orig), "%s", line);
        curline++;
        int n = strlen(line);
        for (int i=0; i<n; i++) line[i] = tolower(line[i]);
        char *cmd = strtok(line, delim);
        if (cmd && (cmd[0] != '#') && (cmd[0] != '\0')) {
            // have a decent command
            bool processed = false;
            switch (commands[cmd]) {
                case tld: {
                    char *tld = next_token(delim);
                    if (!tld) break;                            // no tld value
                    dc.tlds.insert(tld);
                    processed = true;
                    } break;

                case content: {
                    char *suff = strtok(NULL, delim);
                    if (!suff) break;                           // no dns suffix
                    char *msg = suff + strlen(suff);
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the dns suffix
                    msg  = strchr(msg+1, '\'');
                    if (!msg) break;                            // no reply message template
                    msg++; // move over the leading '
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the leading quote
                    char *last = strchr(msg, '\'');
                    if (!last) break;                           // no trailing quote
                    *last = '\0';                               // make it a null terminator
                    dc.content_suffix  = register_string(suff);
                    dc.content_message = register_string(msg);
                    processed = true;
                    } break;

                case ignore: {
                    char *host = next_token(delim);
                    if (!host) break;
                    dc.content_host_ignore.insert(host);
                    processed = true;
                    } break;

                case hostlimit: {
                    char *limit = strtok(NULL, delim);
                    if (!limit) break;                          // no integer limit
                    char *msg = limit + strlen(limit);
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the limit
                    msg  = strchr(msg+1, '\'');
                    if (!msg) break;                            // no reply message template
                    msg++; // move over the leading '
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the leading quote
                    char *last = strchr(msg, '\'');
                    if (!last) break;                           // no trailing quote
                    *last = '\0';                               // make it a null terminator
                    dc.host_limit         = atoi(limit);
                    dc.host_limit_message = register_string(msg);
                    dc.host_random        = false;
                    processed = true;
                    } break;

                case hostslimit: {
                    char *limit = next_token(delim);
                    if (!limit) break;                          // no integer limit
                    dc.host_limit  = atoi(limit);
                    dc.host_random = true;
                    processed = true;
                    } break;

                case htmllimit: {
                    char *limit = strtok(NULL, delim);
                    if (!limit) break;                          // no integer limit
                    char *msg = limit + strlen(limit);
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the limit
                    msg  = strchr(msg+1, '\'');
                    if (!msg) break;                            // no reply message template
                    msg++; // move over the leading '
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the leading quote
                    char *last = strchr(msg, '\'');
                    if (!last) break;                           // no trailing quote
                    *last = '\0';                               // make it a null terminator
                    dc.tag_limit         = atoi(limit);
                    dc.tag_limit_message = register_string(msg);
                    processed = true;
                    } break;

                case htmltag: {
                    char *tag = next_token(delim);
                    if (!tag) break;                            // no html tag value
                    dc.html_tags.insert(tag);                   // base version
                    char buf[200];
                    snprintf(buf, sizeof(buf), "/%s", tag);
                    dc.html_tags.insert(register_string(buf));  // leading /
                    snprintf(buf, sizeof(buf), "%s/", tag);
                    dc.html_tags.insert(register_string(buf));  // trailing /
                    processed = true;
                    } break;

                case dnsbl: {
                    // have a new dnsbl to use
                    char *name = next_token(delim);
                    if (!name) break;                           // no name name
                    if (find_dnsbl(dc, name)) break;            // duplicate entry
                    char *suff = strtok(NULL, delim);
                    if (!suff) break;                           // no dns suffic
                    char *msg = suff + strlen(suff);
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the dns suffix
                    msg  = strchr(msg+1, '\'');
                    if (!msg) break;                            // no reply message template
                    msg++; // move over the leading '
                    if ((msg - line) >= strlen(orig)) break;    // line ended with the leading quote
                    char *last = strchr(msg, '\'');
                    if (!last) break;                           // no trailing quote
                    *last = '\0';                               // make it a null terminator
                    dc.dnsbls[name] = new DNSBL(register_string(suff), register_string(msg));
                    processed = true;
                    } break;

                case dnsbll: {
                    // define a new combination of dnsbls
                    char *name = next_token(delim);
                    if (!name) break;
                    if (find_dnsbll(dc, name)) break;               // duplicate entry
                    char *list = next_token(delim);
                    if (!list || (*list == '\0') || (*list == '#')) break;
                    DNSBLLP d = new DNSBLL;
                    DNSBLP p = find_dnsbl(dc, list);
                    if (p) d->push_back(p);
                    while (true) {
                        list = next_token(delim);
                        if (!list || (*list == '\0') || (*list == '#')) break;
                        DNSBLP p = find_dnsbl(dc, list);
                        if (p) d->push_back(p);
                    }
                    dc.dnsblls[name] = d;
                    processed = true;
                    } break;

                case envfrom: {
                    // add an entry into the named string_map
                    char *name = next_token(delim);
                    if (!name) break;
                    char *from = next_token(delim);
                    if (!from) break;
                    char *list = next_token(delim);
                    if (!list) break;
                    if ((strcmp(list, WHITE) == 0) ||
                        (strcmp(list, BLACK) == 0)) {
                        string_map &fm = really_find_from_map(dc, name);
                        fm[from] = list;
                        processed = true;
                    }
                    else {
                        // list may be the name of a previously defined from_map
                        string_map *m = find_from_map(dc, list);
                        if (m && (strcmp(list,name) != 0)) {
                            string_map &pm = *m;
                            string_map &fm = really_find_from_map(dc, name);
                            fm.insert(pm.begin(), pm.end());
                            processed = true;
                        }
                    }
                    } break;

                case envto: {
                    // define the dnsbl_list and env_from maps to use for this recipient
                    char *to   = next_token(delim);
                    if (!to) break;
                    char *list = next_token(delim);
                    if (!list) break;
                    char *from = next_token(delim);
                    if (!from) break;
                    dc.env_to_dnsbll[to]  = list;
                    dc.env_to_chkfrom[to] = from;
                    processed = true;
                    } break;

                case include: {
                    char *fn = next_token(delim);
                    if (ok_to_include(dc, fn)) {
                        load_conf(dc, fn);
                        processed = true;
                    }
                    } break;

                case includedcc: {
                    char *name = next_token(delim);
                    if (!name) break;
                    char *fn = next_token(delim);
                    if (ok_to_include(dc, fn)) {
                        load_conf_dcc(dc, name, fn);
                        processed = true;
                    }
                    } break;

                default: {
                    } break;
            }
            if (!processed) {
                pthread_mutex_lock(&syslog_mutex);
                    openlog("dnsbl", LOG_PID, LOG_MAIL);
                    syslog(LOG_ERR, "ignoring file %s line %d : %s\n", fn, curline, orig);
                    closelog();
                pthread_mutex_unlock(&syslog_mutex);
            }
        }
    }
    is.close();
}


////////////////////////////////////////////////
//  reload the config
//
static CONFIG* new_conf();
static CONFIG* new_conf() {
    CONFIG *newc = new CONFIG;
    pthread_mutex_lock(&config_mutex);
        newc->generation = generation++;
    pthread_mutex_unlock(&config_mutex);
    char buf[200];
    snprintf(buf, sizeof(buf), "loading configuration generation %d", newc->generation);
    my_syslog(buf);
    load_conf(*newc, "dnsbl.conf");
    newc->load_time = time(NULL);
    return newc;
}


////////////////////////////////////////////////
//  thread to watch the old config files for changes
//  and reload when needed. we also cleanup old
//  configs whose reference count has gone to zero.
//
static void* config_loader(void *arg);
static void* config_loader(void *arg) {
    typedef set<CONFIG *> configp_set;
    configp_set old_configs;
    while (loader_run) {
        sleep(180);  // look for modifications every 3 minutes
        if (!loader_run) break;
        CONFIG &dc = *config;
        time_t then = dc.load_time;
        struct stat st;
        bool reload = false;
        for (string_list::iterator i=dc.config_files.begin(); i!=dc.config_files.end(); i++) {
            char *fn = *i;
            if (stat(fn, &st))           reload = true; // file disappeared
            else if (st.st_mtime > then) reload = true; // file modified
            if (reload) break;
        }
        if (reload) {
            CONFIG *newc = new_conf();
            // replace the global config pointer
            pthread_mutex_lock(&config_mutex);
                CONFIG *old = config;
                config = newc;
            pthread_mutex_unlock(&config_mutex);
            if (old) old_configs.insert(old);
        }
        // now look for old configs with zero ref counts
        for (configp_set::iterator i=old_configs.begin(); i!=old_configs.end(); ) {
            CONFIG *old = *i;
            if (!old->reference_count) {
                char buf[200];
                snprintf(buf, sizeof(buf), "freeing memory for old configuration generation %d", old->generation);
                my_syslog(buf);
                delete old; // destructor does all the work
                old_configs.erase(i++);
            }
            else i++;
        }
    }
    return NULL;
}


static void usage(char *prog);
static void usage(char *prog)
{
    fprintf(stderr, "Usage: %s  [-d] [-c] -r port -p sm-sock-addr [-t timeout]\n", prog);
    fprintf(stderr, "where port is for the connection to our own dns resolver processes\n");
    fprintf(stderr, "    and should be local-domain-socket-file-name\n");
    fprintf(stderr, "where sm-sock-addr is for the connection to sendmail\n");
    fprintf(stderr, "    and should be one of\n");
    fprintf(stderr, "        inet:port@ip-address\n");
    fprintf(stderr, "        local:local-domain-socket-file-name\n");
    fprintf(stderr, "-c will load and dump the config to stdout\n");
    fprintf(stderr, "-d will add some syslog debug messages\n");
}



static void setup_socket(char *sock);
static void setup_socket(char *sock) {
    unlink(sock);
    //  sockaddr_un addr;
    //  memset(&addr, '\0', sizeof addr);
    //  addr.sun_family = AF_UNIX;
    //  strncpy(addr.sun_path, sock, sizeof(addr.sun_path)-1);
    //  int s = socket(AF_UNIX, SOCK_STREAM, 0);
    //  bind(s, (sockaddr*)&addr, sizeof(addr));
    //  close(s);
}


int main(int argc, char**argv)
{
    bool check   = false;
    bool setconn = false;
    bool setreso = false;
    int c;
    const char *args = "r:p:t:hcd";
    extern char *optarg;

    // Process command line options
    while ((c = getopt(argc, argv, args)) != -1) {
        switch (c) {
            case 'r':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf(stderr, "Illegal resolver socket: %s\n", optarg);
                    exit(EX_USAGE);
                }
                resolver_port = strdup(optarg);
                setup_socket(resolver_port);
                setreso = true;
                break;

            case 'p':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf(stderr, "Illegal sendmail socket: %s\n", optarg);
                    exit(EX_USAGE);
                }
                if (smfi_setconn(optarg) == MI_FAILURE) {
                    fprintf(stderr, "smfi_setconn failed\n");
                    exit(EX_SOFTWARE);
                }
                     if (strncasecmp(optarg, "unix:", 5) == 0)  setup_socket(optarg + 5);
                else if (strncasecmp(optarg, "local:", 6) == 0) setup_socket(optarg + 6);
                setconn = true;
                break;

            case 't':
                if (optarg == NULL || *optarg == '\0') {
                    fprintf(stderr, "Illegal timeout: %s\n", optarg);
                    exit(EX_USAGE);
                }
                if (smfi_settimeout(atoi(optarg)) == MI_FAILURE) {
                    fprintf(stderr, "smfi_settimeout failed\n");
                    exit(EX_SOFTWARE);
                }
                break;

            case 'c':
                check = true;
                break;

            case 'd':
                debug_syslog = true;
                break;

            case 'h':
            default:
                usage(argv[0]);
                exit(EX_USAGE);
        }
    }

    if (check) {
        CONFIG &dc = *new_conf();
        dumpit(dc);
        return 0;
    }

    if (!setconn) {
        fprintf(stderr, "%s: Missing required -p argument\n", argv[0]);
        usage(argv[0]);
        exit(EX_USAGE);
    }

    if (!setreso) {
        fprintf(stderr, "%s: Missing required -r argument\n", argv[0]);
        usage(argv[0]);
        exit(EX_USAGE);
    }

    if (smfi_register(smfilter) == MI_FAILURE) {
        fprintf(stderr, "smfi_register failed\n");
        exit(EX_UNAVAILABLE);
    }

    // switch to background mode
    if (daemon(1,0) < 0) {
        fprintf(stderr, "daemon() call failed\n");
        exit(EX_UNAVAILABLE);
    }

    // write the pid
    const char *pidpath = "/var/run/dnsbl.pid";
    unlink(pidpath);
    FILE *f = fopen(pidpath, "w");
    if (f) {
#ifdef linux
        // from a comment in the DCC source code:
        // Linux threads are broken.  Signals given the
        // original process are delivered to only the
        // thread that happens to have that PID.  The
        // sendmail libmilter thread that needs to hear
        // SIGINT and other signals does not, and that breaks
        // scripts that need to stop milters.
        // However, signaling the process group works.
        fprintf(f, "-%d\n", (u_int)getpgrp());
#else
        fprintf(f, "%d\n", (u_int)getpid());
#endif
        fclose(f);
    }

    // initialize the thread sync objects
    pthread_mutex_init(&config_mutex, 0);
    pthread_mutex_init(&syslog_mutex, 0);
    pthread_mutex_init(&resolve_mutex, 0);
    pthread_mutex_init(&fd_pool_mutex, 0);

    // drop root privs
    struct passwd *pw = getpwnam("dnsbl");
    if (pw) {
        if (setgid(pw->pw_gid) == -1) {
            my_syslog("failed to switch to group dnsbl");
        }
        if (setuid(pw->pw_uid) == -1) {
            my_syslog("failed to switch to user dnsbl");
        }
    }

    // fork off the resolver listener process
    pid_t child = fork();
    if (child < 0) {
        my_syslog("failed to create resolver listener process");
        exit(0);
    }
    if (child == 0) {
        // we are the child - dns resolver listener process
        resolver_socket = socket(AF_UNIX, SOCK_STREAM, 0);
        if (resolver_socket < 0) {
            my_syslog("child failed to create resolver socket");
            exit(0);   // failed
        }
        sockaddr_un server;
        memset(&server, '\0', sizeof(server));
        server.sun_family = AF_UNIX;
        strncpy(server.sun_path, resolver_port, sizeof(server.sun_path)-1);
        // set the socket options
     ///int      reuse_addr = 1;
     ///linger linger_opt;
     ///linger_opt.l_onoff  = 0;    // off
     ///linger_opt.l_linger = 0;
     ///setsockopt(resolver_socket, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char*>(&reuse_addr), sizeof(reuse_addr));
     ///setsockopt(resolver_socket, SOL_SOCKET, SO_LINGER,    reinterpret_cast<char*>(&linger_opt), sizeof(linger_opt));
     ///// set nonblocking mode
     ///int     dummy = 0;
     ///int     flags = fcntl(resolver_socket, F_GETFL, dummy);
     ///if (flags >= 0) fcntl(resolver_socket, F_SETFL, flags | O_NONBLOCK);
        //try to bind the address to the socket.
        if (bind(resolver_socket, (sockaddr *)&server, sizeof(server)) < 0) {
            // bind failed
            shutdown(resolver_socket, SHUT_RDWR);
            close(resolver_socket);
            my_syslog("child failed to bind resolver socket");
            exit(0);   // failed
        }

        //listen on the socket.
        if (listen(resolver_socket, 10) < 0) {
            // listen failed
            shutdown(resolver_socket, SHUT_RDWR);
            close(resolver_socket);
            my_syslog("child failed to listen to the resolver socket");
            exit(0);   // failed
        }
        while (true) {
            sockaddr_un client;
            socklen_t   clientlen = sizeof(client);
            int s = accept(resolver_socket, (sockaddr *)&client, &clientlen);
            if (s > 0) {
                // accept worked, it did not get cancelled before we could accept it
                // fork off a process to handle this connection
                int newchild = fork();
                if (newchild == 0) {
                    // this is the worker process
                    // child does not need the listening socket
                    close(resolver_socket);
                  //my_syslog("child forked a worker process");
                    process_resolver_requests(s);
                  //my_syslog("child terminated a worker process");
                    exit(0);
                }
                else {
                    // this is the parent
                    // parent does not need the accepted socket
                    close(s);
                }
            }
        }
        exit(0);    // make sure we don't fall thru.
    }
    else {
        sleep(2);   // allow child to get started
    }

    // load the initial config
    config = new_conf();

    // only create threads after the fork() in daemon
    pthread_t tid;
    if (pthread_create(&tid, 0, config_loader, 0))
        my_syslog("failed to create config loader thread");
    if (pthread_detach(tid))
        my_syslog("failed to detach config loader thread");

    time_t starting = time(NULL);
    int rc = smfi_main();
    if ((rc != MI_SUCCESS) && (time(NULL) > starting+5*60)) {
        my_syslog("trying to restart after smfi_main()");
        loader_run = false;     // eventually the config loader thread will terminate
        execvp(argv[0], argv);
    }
    exit((rc == MI_SUCCESS) ? 0 : EX_UNAVAILABLE);
}