sendmail/libmilter/listener.c

/*
 *  Copyright (c) 1999-2007 Proofpoint, Inc. and its suppliers.
 *  All rights reserved.
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the sendmail distribution.
 *
 */

#include <sm/gen.h>
SM_RCSID("@(#)$Id: listener.c,v 8.127 2013-11-22 20:51:36 ca Exp $")

/*
**  listener.c -- threaded network listener
*/

#include "libmilter.h"
#include <sm/errstring.h>

#include <sys/types.h>
#include <sys/stat.h>


# if NETINET || NETINET6
#  include <arpa/inet.h>
# endif /* NETINET || NETINET6 */
# if SM_CONF_POLL
#  undef SM_FD_OK_SELECT
#  define SM_FD_OK_SELECT(fd)       true
# endif /* SM_CONF_POLL */

static smutex_t L_Mutex;
static int L_family;
static SOCKADDR_LEN_T L_socksize;
static socket_t listenfd = INVALID_SOCKET;

static socket_t mi_milteropen __P((char *, int, bool, char *));
#if !_FFR_WORKERS_POOL
static void *mi_thread_handle_wrapper __P((void *));
#endif /* !_FFR_WORKERS_POOL */

/*
**  MI_OPENSOCKET -- create the socket where this filter and the MTA will meet
**
**  Parameters:
**      conn -- connection description
**      backlog -- listen backlog
**      dbg -- debug level
**      rmsocket -- if true, try to unlink() the socket first
**          (UNIX domain sockets only)
**      smfi -- filter structure to use
**
**  Return value:
**      MI_SUCCESS/MI_FAILURE
*/

int
mi_opensocket(conn, backlog, dbg, rmsocket, smfi)
    char *conn;
    int backlog;
    int dbg;
    bool rmsocket;
    smfiDesc_ptr smfi;
{
    if (smfi == NULL || conn == NULL)
        return MI_FAILURE;

    if (ValidSocket(listenfd))
        return MI_SUCCESS;

    if (dbg > 0)
    {
        smi_log(SMI_LOG_DEBUG,
            "%s: Opening listen socket on conn %s",
            smfi->xxfi_name, conn);
    }
    (void) smutex_init(&L_Mutex);
    (void) smutex_lock(&L_Mutex);
    listenfd = mi_milteropen(conn, backlog, rmsocket, smfi->xxfi_name);
    if (!ValidSocket(listenfd))
    {
        smi_log(SMI_LOG_FATAL,
            "%s: Unable to create listening socket on conn %s",
            smfi->xxfi_name, conn);
        (void) smutex_unlock(&L_Mutex);
        return MI_FAILURE;
    }
    if (!SM_FD_OK_SELECT(listenfd))
    {
        smi_log(SMI_LOG_ERR, "%s: fd %d is larger than FD_SETSIZE %d",
            smfi->xxfi_name, listenfd, FD_SETSIZE);
        (void) smutex_unlock(&L_Mutex);
        return MI_FAILURE;
    }
    (void) smutex_unlock(&L_Mutex);
    return MI_SUCCESS;
}

/*
**  MI_MILTEROPEN -- setup socket to listen on
**
**  Parameters:
**      conn -- connection description
**      backlog -- listen backlog
**      rmsocket -- if true, try to unlink() the socket first
**          (UNIX domain sockets only)
**      name -- name for logging
**
**  Returns:
**      socket upon success, error code otherwise.
**
**  Side effect:
**      sets sockpath if UNIX socket.
*/

#if NETUNIX
static char *sockpath = NULL;
#endif /* NETUNIX */

static socket_t
mi_milteropen(conn, backlog, rmsocket, name)
    char *conn;
    int backlog;
    bool rmsocket;
    char *name;
{
    socket_t sock;
    int sockopt = 1;
    int fdflags;
    size_t len = 0;
    char *p;
    char *colon;
    char *at;
    SOCKADDR addr;

    if (conn == NULL || conn[0] == '\0')
    {
        smi_log(SMI_LOG_ERR, "%s: empty or missing socket information",
            name);
        return INVALID_SOCKET;
    }
    (void) memset(&addr, '\0', sizeof addr);

    /* protocol:filename or protocol:port@host */
    p = conn;
    colon = strchr(p, ':');
    if (colon != NULL)
    {
        *colon = '\0';

        if (*p == '\0')
        {
#if NETUNIX
            /* default to AF_UNIX */
            addr.sa.sa_family = AF_UNIX;
            L_socksize = sizeof (struct sockaddr_un);
#else /* NETUNIX */
# if NETINET
            /* default to AF_INET */
            addr.sa.sa_family = AF_INET;
            L_socksize = sizeof addr.sin;
# else /* NETINET */
#  if NETINET6
            /* default to AF_INET6 */
            addr.sa.sa_family = AF_INET6;
            L_socksize = sizeof addr.sin6;
#  else /* NETINET6 */
            /* no protocols available */
            smi_log(SMI_LOG_ERR,
                "%s: no valid socket protocols available",
                name);
            return INVALID_SOCKET;
#  endif /* NETINET6 */
# endif /* NETINET */
#endif /* NETUNIX */
        }
#if NETUNIX
        else if (strcasecmp(p, "unix") == 0 ||
             strcasecmp(p, "local") == 0)
        {
            addr.sa.sa_family = AF_UNIX;
            L_socksize = sizeof (struct sockaddr_un);
        }
#endif /* NETUNIX */
#if NETINET
        else if (strcasecmp(p, "inet") == 0)
        {
            addr.sa.sa_family = AF_INET;
            L_socksize = sizeof addr.sin;
        }
#endif /* NETINET */
#if NETINET6
        else if (strcasecmp(p, "inet6") == 0)
        {
            addr.sa.sa_family = AF_INET6;
            L_socksize = sizeof addr.sin6;
        }
#endif /* NETINET6 */
        else
        {
            smi_log(SMI_LOG_ERR, "%s: unknown socket type %s",
                name, p);
            return INVALID_SOCKET;
        }
        *colon++ = ':';
    }
    else
    {
        colon = p;
#if NETUNIX
        /* default to AF_UNIX */
        addr.sa.sa_family = AF_UNIX;
        L_socksize = sizeof (struct sockaddr_un);
#else /* NETUNIX */
# if NETINET
        /* default to AF_INET */
        addr.sa.sa_family = AF_INET;
        L_socksize = sizeof addr.sin;
# else /* NETINET */
#  if NETINET6
        /* default to AF_INET6 */
        addr.sa.sa_family = AF_INET6;
        L_socksize = sizeof addr.sin6;
#  else /* NETINET6 */
        smi_log(SMI_LOG_ERR, "%s: unknown socket type %s",
            name, p);
        return INVALID_SOCKET;
#  endif /* NETINET6 */
# endif /* NETINET */
#endif /* NETUNIX */
    }

#if NETUNIX
    if (addr.sa.sa_family == AF_UNIX)
    {
# if 0
        long sff = SFF_SAFEDIRPATH|SFF_OPENASROOT|SFF_NOLINK|SFF_CREAT|SFF_MUSTOWN;
# endif /* 0 */

        at = colon;
        len = strlen(colon) + 1;
        if (len >= sizeof addr.sunix.sun_path)
        {
            errno = EINVAL;
            smi_log(SMI_LOG_ERR, "%s: UNIX socket name %s too long",
                name, colon);
            return INVALID_SOCKET;
        }
        (void) sm_strlcpy(addr.sunix.sun_path, colon,
                sizeof addr.sunix.sun_path);
# if 0
        errno = safefile(colon, RunAsUid, RunAsGid, RunAsUserName, sff,
                 S_IRUSR|S_IWUSR, NULL);

        /* if not safe, don't create */
        if (errno != 0)
        {
            smi_log(SMI_LOG_ERR,
                "%s: UNIX socket name %s unsafe",
                name, colon);
            return INVALID_SOCKET;
        }
# endif /* 0 */
    }
#endif /* NETUNIX */

#if NETINET || NETINET6
    if (
# if NETINET
        addr.sa.sa_family == AF_INET
# endif /* NETINET */
# if NETINET && NETINET6
        ||
# endif /* NETINET && NETINET6 */
# if NETINET6
        addr.sa.sa_family == AF_INET6
# endif /* NETINET6 */
       )
    {
        unsigned short port;

        /* Parse port@host */
        at = strchr(colon, '@');
        if (at == NULL)
        {
            switch (addr.sa.sa_family)
            {
# if NETINET
              case AF_INET:
                addr.sin.sin_addr.s_addr = INADDR_ANY;
                break;
# endif /* NETINET */

# if NETINET6
              case AF_INET6:
                addr.sin6.sin6_addr = in6addr_any;
                break;
# endif /* NETINET6 */
            }
        }
        else
            *at = '\0';

        if (isascii(*colon) && isdigit(*colon))
            port = htons((unsigned short) atoi(colon));
        else
        {
# ifdef NO_GETSERVBYNAME
            smi_log(SMI_LOG_ERR, "%s: invalid port number %s",
                name, colon);
            return INVALID_SOCKET;
# else /* NO_GETSERVBYNAME */
            register struct servent *sp;

            sp = getservbyname(colon, "tcp");
            if (sp == NULL)
            {
                smi_log(SMI_LOG_ERR,
                    "%s: unknown port name %s",
                    name, colon);
                return INVALID_SOCKET;
            }
            port = sp->s_port;
# endif /* NO_GETSERVBYNAME */
        }
        if (at != NULL)
        {
            *at++ = '@';
            if (*at == '[')
            {
                char *end;

                end = strchr(at, ']');
                if (end != NULL)
                {
                    bool found = false;
# if NETINET
                    unsigned long hid = INADDR_NONE;
# endif /* NETINET */
# if NETINET6
                    struct sockaddr_in6 hid6;
# endif /* NETINET6 */

                    *end = '\0';
# if NETINET
                    if (addr.sa.sa_family == AF_INET &&
                        (hid = inet_addr(&at[1])) != INADDR_NONE)
                    {
                        addr.sin.sin_addr.s_addr = hid;
                        addr.sin.sin_port = port;
                        found = true;
                    }
# endif /* NETINET */
# if NETINET6
                    (void) memset(&hid6, '\0', sizeof hid6);
                    if (addr.sa.sa_family == AF_INET6 &&
                        mi_inet_pton(AF_INET6, &at[1],
                             &hid6.sin6_addr) == 1)
                    {
                        addr.sin6.sin6_addr = hid6.sin6_addr;
                        addr.sin6.sin6_port = port;
                        found = true;
                    }
# endif /* NETINET6 */
                    *end = ']';
                    if (!found)
                    {
                        smi_log(SMI_LOG_ERR,
                            "%s: Invalid numeric domain spec \"%s\"",
                            name, at);
                        return INVALID_SOCKET;
                    }
                }
                else
                {
                    smi_log(SMI_LOG_ERR,
                        "%s: Invalid numeric domain spec \"%s\"",
                        name, at);
                    return INVALID_SOCKET;
                }
            }
            else
            {
                struct hostent *hp = NULL;

                hp = mi_gethostbyname(at, addr.sa.sa_family);
                if (hp == NULL)
                {
                    smi_log(SMI_LOG_ERR,
                        "%s: Unknown host name %s",
                        name, at);
                    return INVALID_SOCKET;
                }
                addr.sa.sa_family = hp->h_addrtype;
                switch (hp->h_addrtype)
                {
# if NETINET
                  case AF_INET:
                    (void) memmove(&addr.sin.sin_addr,
                               hp->h_addr,
                               INADDRSZ);
                    addr.sin.sin_port = port;
                    break;
# endif /* NETINET */

# if NETINET6
                  case AF_INET6:
                    (void) memmove(&addr.sin6.sin6_addr,
                               hp->h_addr,
                               IN6ADDRSZ);
                    addr.sin6.sin6_port = port;
                    break;
# endif /* NETINET6 */

                  default:
                    smi_log(SMI_LOG_ERR,
                        "%s: Unknown protocol for %s (%d)",
                        name, at, hp->h_addrtype);
                    return INVALID_SOCKET;
                }
# if NETINET6
                freehostent(hp);
# endif /* NETINET6 */
            }
        }
        else
        {
            switch (addr.sa.sa_family)
            {
# if NETINET
              case AF_INET:
                addr.sin.sin_port = port;
                break;
# endif /* NETINET */
# if NETINET6
              case AF_INET6:
                addr.sin6.sin6_port = port;
                break;
# endif /* NETINET6 */
            }
        }
    }
#endif /* NETINET || NETINET6 */

    sock = socket(addr.sa.sa_family, SOCK_STREAM, 0);
    if (!ValidSocket(sock))
    {
        smi_log(SMI_LOG_ERR,
            "%s: Unable to create new socket: %s",
            name, sm_errstring(errno));
        return INVALID_SOCKET;
    }

    if ((fdflags = fcntl(sock, F_GETFD, 0)) == -1 ||
        fcntl(sock, F_SETFD, fdflags | FD_CLOEXEC) == -1)
    {
        smi_log(SMI_LOG_ERR,
            "%s: Unable to set close-on-exec: %s", name,
            sm_errstring(errno));
        (void) closesocket(sock);
        return INVALID_SOCKET;
    }

    if (
#if NETUNIX
        addr.sa.sa_family != AF_UNIX &&
#endif /* NETUNIX */
        setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *) &sockopt,
               sizeof(sockopt)) == -1)
    {
        smi_log(SMI_LOG_ERR,
            "%s: set reuseaddr failed (%s)", name,
            sm_errstring(errno));
        (void) closesocket(sock);
        return INVALID_SOCKET;
    }

#if NETUNIX
    if (addr.sa.sa_family == AF_UNIX && rmsocket)
    {
        struct stat s;

        if (stat(colon, &s) != 0)
        {
            if (errno != ENOENT)
            {
                smi_log(SMI_LOG_ERR,
                    "%s: Unable to stat() %s: %s",
                    name, colon, sm_errstring(errno));
                (void) closesocket(sock);
                return INVALID_SOCKET;
            }
        }
        else if (!S_ISSOCK(s.st_mode))
        {
            smi_log(SMI_LOG_ERR,
                "%s: %s is not a UNIX domain socket",
                name, colon);
            (void) closesocket(sock);
            return INVALID_SOCKET;
        }
        else if (unlink(colon) != 0)
        {
            smi_log(SMI_LOG_ERR,
                "%s: Unable to remove %s: %s",
                name, colon, sm_errstring(errno));
            (void) closesocket(sock);
            return INVALID_SOCKET;
        }
    }
#endif /* NETUNIX */

    if (bind(sock, &addr.sa, L_socksize) < 0)
    {
        smi_log(SMI_LOG_ERR,
            "%s: Unable to bind to port %s: %s",
            name, conn, sm_errstring(errno));
        (void) closesocket(sock);
        return INVALID_SOCKET;
    }

    if (listen(sock, backlog) < 0)
    {
        smi_log(SMI_LOG_ERR,
            "%s: listen call failed: %s", name,
            sm_errstring(errno));
        (void) closesocket(sock);
        return INVALID_SOCKET;
    }

#if NETUNIX
    if (addr.sa.sa_family == AF_UNIX && len > 0)
    {
        /*
        **  Set global variable sockpath so the UNIX socket can be
        **  unlink()ed at exit.
        */

        sockpath = (char *) malloc(len);
        if (sockpath != NULL)
            (void) sm_strlcpy(sockpath, colon, len);
        else
        {
            smi_log(SMI_LOG_ERR,
                "%s: can't malloc(%d) for sockpath: %s",
                name, (int) len, sm_errstring(errno));
            (void) closesocket(sock);
            return INVALID_SOCKET;
        }
    }
#endif /* NETUNIX */
    L_family = addr.sa.sa_family;
    return sock;
}

#if !_FFR_WORKERS_POOL
/*
**  MI_THREAD_HANDLE_WRAPPER -- small wrapper to handle session
**
**  Parameters:
**      arg -- argument to pass to mi_handle_session()
**
**  Returns:
**      results from mi_handle_session()
*/

static void *
mi_thread_handle_wrapper(arg)
    void *arg;
{
    /*
    **  Note: on some systems this generates a compiler warning:
    **  cast to pointer from integer of different size
    **  You can safely ignore this warning as the result of this function
    **  is not used anywhere.
    */

    return (void *) mi_handle_session(arg);
}
#endif /* _FFR_WORKERS_POOL */

/*
**  MI_CLOSENER -- close listen socket
**
**  Parameters:
**      none.
**
**  Returns:
**      none.
*/

void
mi_closener()
{
    (void) smutex_lock(&L_Mutex);
    if (ValidSocket(listenfd))
    {
#if NETUNIX
        bool removable;
        struct stat sockinfo;
        struct stat fileinfo;

        removable = sockpath != NULL &&
                geteuid() != 0 &&
                fstat(listenfd, &sockinfo) == 0 &&
                (S_ISFIFO(sockinfo.st_mode)
# ifdef S_ISSOCK
                 || S_ISSOCK(sockinfo.st_mode)
# endif /* S_ISSOCK */
                );
#endif /* NETUNIX */

        (void) closesocket(listenfd);
        listenfd = INVALID_SOCKET;

#if NETUNIX
        /* XXX sleep() some time before doing this? */
        if (sockpath != NULL)
        {
            if (removable &&
                stat(sockpath, &fileinfo) == 0 &&
                ((fileinfo.st_dev == sockinfo.st_dev &&
                  fileinfo.st_ino == sockinfo.st_ino)
# ifdef S_ISSOCK
                 || S_ISSOCK(fileinfo.st_mode)
# endif /* S_ISSOCK */
                )
                &&
                (S_ISFIFO(fileinfo.st_mode)
# ifdef S_ISSOCK
                 || S_ISSOCK(fileinfo.st_mode)
# endif /* S_ISSOCK */
                 ))
                (void) unlink(sockpath);
            free(sockpath);
            sockpath = NULL;
        }
#endif /* NETUNIX */
    }
    (void) smutex_unlock(&L_Mutex);
}

/*
**  MI_LISTENER -- Generic listener harness
**
**  Open up listen port
**  Wait for connections
**
**  Parameters:
**      conn -- connection description
**      dbg -- debug level
**      smfi -- filter structure to use
**      timeout -- timeout for reads/writes
**      backlog -- listen queue backlog size
**
**  Returns:
**      MI_SUCCESS -- Exited normally
**             (session finished or we were told to exit)
**      MI_FAILURE -- Network initialization failed.
*/

#if BROKEN_PTHREAD_SLEEP

/*
**  Solaris 2.6, perhaps others, gets an internal threads library panic
**  when sleep() is used:
**
**  thread_create() failed, returned 11 (EINVAL)
**  co_enable, thr_create() returned error = 24
**  libthread panic: co_enable failed (PID: 17793 LWP 1)
**  stacktrace:
**  ef526b10
**  ef52646c
**  ef534cbc
**  156a4
**  14644
**  1413c
**  135e0
**  0
*/

# define MI_SLEEP(s)                            \
{                                   \
    int rs = 0;                         \
    struct timeval st;                      \
                                    \
    st.tv_sec = (s);                        \
    st.tv_usec = 0;                         \
    if (st.tv_sec > 0)                      \
    {                               \
        for (;;)                        \
        {                           \
            rs = select(0, NULL, NULL, NULL, &st);      \
            if (rs < 0 && errno == EINTR)           \
                continue;               \
            if (rs != 0)                    \
            {                       \
                smi_log(SMI_LOG_ERR,            \
                    "MI_SLEEP(): select() returned non-zero result %d, errno = %d", \
                    rs, errno);         \
            }                       \
            break;                      \
        }                           \
    }                               \
}
#else /* BROKEN_PTHREAD_SLEEP */
# define MI_SLEEP(s)    sleep((s))
#endif /* BROKEN_PTHREAD_SLEEP */

int
mi_listener(conn, dbg, smfi, timeout, backlog)
    char *conn;
    int dbg;
    smfiDesc_ptr smfi;
    time_t timeout;
    int backlog;
{
    socket_t connfd = INVALID_SOCKET;
#if _FFR_DUP_FD
    socket_t dupfd = INVALID_SOCKET;
#endif /* _FFR_DUP_FD */
    int sockopt = 1;
    int r, mistop;
    int ret = MI_SUCCESS;
    int mcnt = 0;   /* error count for malloc() failures */
    int tcnt = 0;   /* error count for thread_create() failures */
    int acnt = 0;   /* error count for accept() failures */
    int scnt = 0;   /* error count for select() failures */
    int save_errno = 0;
#if !_FFR_WORKERS_POOL
    sthread_t thread_id;
#endif /* !_FFR_WORKERS_POOL */
    _SOCK_ADDR cliaddr;
    SOCKADDR_LEN_T clilen;
    SMFICTX_PTR ctx;
    FD_RD_VAR(rds, excs);
    struct timeval chktime;

    if (mi_opensocket(conn, backlog, dbg, false, smfi) == MI_FAILURE)
        return MI_FAILURE;

#if _FFR_WORKERS_POOL
    if (mi_pool_controller_init() == MI_FAILURE)
        return MI_FAILURE;
#endif /* _FFR_WORKERS_POOL */

    clilen = L_socksize;
    while ((mistop = mi_stop()) == MILTER_CONT)
    {
        (void) smutex_lock(&L_Mutex);
        if (!ValidSocket(listenfd))
        {
            ret = MI_FAILURE;
            smi_log(SMI_LOG_ERR,
                "%s: listenfd=%d corrupted, terminating, errno=%d",
                smfi->xxfi_name, listenfd, errno);
            (void) smutex_unlock(&L_Mutex);
            break;
        }

        /* select on interface ports */
        FD_RD_INIT(listenfd, rds, excs);
        chktime.tv_sec = MI_CHK_TIME;
        chktime.tv_usec = 0;
        r = FD_RD_READY(listenfd, rds, excs, &chktime);
        if (r == 0)     /* timeout */
        {
            (void) smutex_unlock(&L_Mutex);
            continue;   /* just check mi_stop() */
        }
        if (r < 0)
        {
            save_errno = errno;
            (void) smutex_unlock(&L_Mutex);
            if (save_errno == EINTR)
                continue;
            scnt++;
            smi_log(SMI_LOG_ERR,
                "%s: %s() failed (%s), %s",
                smfi->xxfi_name, MI_POLLSELECT,
                sm_errstring(save_errno),
                scnt >= MAX_FAILS_S ? "abort" : "try again");
            MI_SLEEP(scnt);
            if (scnt >= MAX_FAILS_S)
            {
                ret = MI_FAILURE;
                break;
            }
            continue;
        }
        if (!FD_IS_RD_RDY(listenfd, rds, excs))
        {
            /* some error: just stop for now... */
            ret = MI_FAILURE;
            (void) smutex_unlock(&L_Mutex);
            smi_log(SMI_LOG_ERR,
                "%s: %s() returned exception for socket, abort",
                smfi->xxfi_name, MI_POLLSELECT);
            break;
        }
        scnt = 0;   /* reset error counter for select() */

        (void) memset(&cliaddr, '\0', sizeof cliaddr);
        connfd = accept(listenfd, (struct sockaddr *) &cliaddr,
                &clilen);
        save_errno = errno;
        (void) smutex_unlock(&L_Mutex);

        /*
        **  If remote side closes before accept() finishes,
        **  sockaddr might not be fully filled in.
        */

        if (ValidSocket(connfd) &&
            (clilen == 0 ||
# ifdef BSD4_4_SOCKADDR
             cliaddr.sa.sa_len == 0 ||
# endif /* BSD4_4_SOCKADDR */
             cliaddr.sa.sa_family != L_family))
        {
            (void) closesocket(connfd);
            connfd = INVALID_SOCKET;
            save_errno = EINVAL;
        }

        /* check if acceptable for select() */
        if (ValidSocket(connfd) && !SM_FD_OK_SELECT(connfd))
        {
            (void) closesocket(connfd);
            connfd = INVALID_SOCKET;
            save_errno = ERANGE;
        }

        if (!ValidSocket(connfd))
        {
            if (save_errno == EINTR
#ifdef EAGAIN
                || save_errno == EAGAIN
#endif /* EAGAIN */
#ifdef ECONNABORTED
                || save_errno == ECONNABORTED
#endif /* ECONNABORTED */
#ifdef EMFILE
                || save_errno == EMFILE
#endif /* EMFILE */
#ifdef ENFILE
                || save_errno == ENFILE
#endif /* ENFILE */
#ifdef ENOBUFS
                || save_errno == ENOBUFS
#endif /* ENOBUFS */
#ifdef ENOMEM
                || save_errno == ENOMEM
#endif /* ENOMEM */
#ifdef ENOSR
                || save_errno == ENOSR
#endif /* ENOSR */
#ifdef EWOULDBLOCK
                || save_errno == EWOULDBLOCK
#endif /* EWOULDBLOCK */
               )
                continue;
            acnt++;
            smi_log(SMI_LOG_ERR,
                "%s: accept() returned invalid socket (%s), %s",
                smfi->xxfi_name, sm_errstring(save_errno),
                acnt >= MAX_FAILS_A ? "abort" : "try again");
            MI_SLEEP(acnt);
            if (acnt >= MAX_FAILS_A)
            {
                ret = MI_FAILURE;
                break;
            }
            continue;
        }
        acnt = 0;   /* reset error counter for accept() */
#if _FFR_DUP_FD
        dupfd = fcntl(connfd, F_DUPFD, 256);
        if (ValidSocket(dupfd) && SM_FD_OK_SELECT(dupfd))
        {
            close(connfd);
            connfd = dupfd;
            dupfd = INVALID_SOCKET;
        }
#endif /* _FFR_DUP_FD */

        if (setsockopt(connfd, SOL_SOCKET, SO_KEEPALIVE,
                (void *) &sockopt, sizeof sockopt) < 0)
        {
            smi_log(SMI_LOG_WARN,
                "%s: set keepalive failed (%s)",
                smfi->xxfi_name, sm_errstring(errno));
            /* XXX: continue? */
        }
        if ((ctx = (SMFICTX_PTR) malloc(sizeof *ctx)) == NULL)
        {
            (void) closesocket(connfd);
            mcnt++;
            smi_log(SMI_LOG_ERR, "%s: malloc(ctx) failed (%s), %s",
                smfi->xxfi_name, sm_errstring(save_errno),
                mcnt >= MAX_FAILS_M ? "abort" : "try again");
            MI_SLEEP(mcnt);
            if (mcnt >= MAX_FAILS_M)
            {
                ret = MI_FAILURE;
                break;
            }
            continue;
        }
        mcnt = 0;   /* reset error counter for malloc() */
        (void) memset(ctx, '\0', sizeof *ctx);
        ctx->ctx_sd = connfd;
        ctx->ctx_dbg = dbg;
        ctx->ctx_timeout = timeout;
        ctx->ctx_smfi = smfi;
        if (smfi->xxfi_connect == NULL)
            ctx->ctx_pflags |= SMFIP_NOCONNECT;
        if (smfi->xxfi_helo == NULL)
            ctx->ctx_pflags |= SMFIP_NOHELO;
        if (smfi->xxfi_envfrom == NULL)
            ctx->ctx_pflags |= SMFIP_NOMAIL;
        if (smfi->xxfi_envrcpt == NULL)
            ctx->ctx_pflags |= SMFIP_NORCPT;
        if (smfi->xxfi_header == NULL)
            ctx->ctx_pflags |= SMFIP_NOHDRS;
        if (smfi->xxfi_eoh == NULL)
            ctx->ctx_pflags |= SMFIP_NOEOH;
        if (smfi->xxfi_body == NULL)
            ctx->ctx_pflags |= SMFIP_NOBODY;
        if (smfi->xxfi_version <= 3 || smfi->xxfi_data == NULL)
            ctx->ctx_pflags |= SMFIP_NODATA;
        if (smfi->xxfi_version <= 2 || smfi->xxfi_unknown == NULL)
            ctx->ctx_pflags |= SMFIP_NOUNKNOWN;

#if _FFR_WORKERS_POOL
# define LOG_CRT_FAIL   "%s: mi_start_session() failed: %d, %s"
        if ((r = mi_start_session(ctx)) != MI_SUCCESS)
#else /* _FFR_WORKERS_POOL */
# define LOG_CRT_FAIL   "%s: thread_create() failed: %d, %s"
        if ((r = thread_create(&thread_id,
                    mi_thread_handle_wrapper,
                    (void *) ctx)) != 0)
#endif /* _FFR_WORKERS_POOL */
        {
            tcnt++;
            smi_log(SMI_LOG_ERR,
                LOG_CRT_FAIL,
                smfi->xxfi_name,  r,
                tcnt >= MAX_FAILS_T ? "abort" : "try again");
            MI_SLEEP(tcnt);
            (void) closesocket(connfd);
            free(ctx);
            if (tcnt >= MAX_FAILS_T)
            {
                ret = MI_FAILURE;
                break;
            }
            continue;
        }
        tcnt = 0;
    }
    if (ret != MI_SUCCESS)
        mi_stop_milters(MILTER_ABRT);
    else
    {
        if (mistop != MILTER_CONT)
            smi_log(SMI_LOG_INFO, "%s: mi_stop=%d",
                smfi->xxfi_name, mistop);
        mi_closener();
    }
    (void) smutex_destroy(&L_Mutex);
    return ret;
}