external/ibm-public/postfix/dist/src/util/sane_accept.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      sane_accept 3
   6 /* SUMMARY
   7 /*      sanitize accept() error returns
   8 /* SYNOPSIS
   9 /*      #include <sane_accept.h>
  10 /*
  11 /*      int     sane_accept(sock, buf, len)
  12 /*      int     sock;
  13 /*      struct sockaddr *buf;
  14 /*      SOCKADDR_SIZE *len;
  15 /* DESCRIPTION
  16 /*      sane_accept() implements the accept(2) socket call, and maps
  17 /*      known harmless error results to EAGAIN.
  18 /*
  19 /*      If the buf and len arguments are not null, then additional
  20 /*      workarounds may be enabled that depend on the socket type.
  21 /* BUGS
  22 /*      Bizarre systems may have other harmless error results. Such
  23 /*      systems encourage programmers to ignore error results, and
  24 /*      penalize programmers who code defensively.
  25 /* LICENSE
  26 /* .ad
  27 /* .fi
  28 /*      The Secure Mailer license must be distributed with this software.
  29 /* AUTHOR(S)
  30 /*      Wietse Venema
  31 /*      IBM T.J. Watson Research
  32 /*      P.O. Box 704
  33 /*      Yorktown Heights, NY 10598, USA
  34 /*--*/
  35
  36 /* System library. */
  37
  38 #include "sys_defs.h"
  39 #include <sys/socket.h>
  40 #include <errno.h>
  41
  42 /* Utility library. */
  43
  44 #include "msg.h"
  45 #include "sane_accept.h"
  46
  47 /* sane_accept - sanitize accept() error returns */
  48
  49 int     sane_accept(int sock, struct sockaddr * sa, SOCKADDR_SIZE *len)
  50 {
  51     static int accept_ok_errors[] = {
  52         EAGAIN,
  53         ECONNREFUSED,
  54         ECONNRESET,
  55         EHOSTDOWN,
  56         EHOSTUNREACH,
  57         EINTR,
  58         ENETDOWN,
  59         ENETUNREACH,
  60         ENOTCONN,
  61         EWOULDBLOCK,
  62         ENOBUFS,                        /* HPUX11 */
  63         ECONNABORTED,
  64 #ifdef EPROTO
  65         EPROTO,                         /* SunOS 5.5.1 */
  66 #endif
  67         0,
  68     };
  69     int     count;
  70     int     err;
  71     int     fd;
  72
  73     /*
  74      * XXX Solaris 2.4 accept() returns EPIPE when a UNIX-domain client has
  75      * disconnected in the mean time. From then on, UNIX-domain sockets are
  76      * hosed beyond recovery. There is no point treating this as a beneficial
  77      * error result because the program would go into a tight loop.
  78      *
  79      * XXX Solaris 2.5.1 accept() returns EPROTO when a TCP client has
  80      * disconnected in the mean time. Since there is no connection, it is
  81      * safe to map the error code onto EAGAIN.
  82      *
  83      * XXX LINUX < 2.1 accept() wakes up before the three-way handshake is
  84      * complete, so it can fail with ECONNRESET and other "false alarm"
  85      * indications.
  86      *
  87      * XXX FreeBSD 4.2-STABLE accept() returns ECONNABORTED when a UNIX-domain
  88      * client has disconnected in the mean time. The data that was sent with
  89      * connect() write() close() is lost, even though the write() and close()
  90      * reported successful completion. This was fixed shortly before FreeBSD
  91      * 4.3.
  92      *
  93      * XXX HP-UX 11 returns ENOBUFS when the client has disconnected in the mean
  94      * time.
  95      */
  96     if ((fd = accept(sock, sa, len)) < 0) {
  97         for (count = 0; (err = accept_ok_errors[count]) != 0; count++) {
  98             if (errno == err) {
  99                 errno = EAGAIN;
 100                 break;
 101             }
 102         }
 103     }
 104
 105     /*
 106      * XXX Solaris select() produces false read events, so that read() blocks
 107      * forever on a blocking socket, and fails with EAGAIN on a non-blocking
 108      * socket. Turning on keepalives will fix a blocking socket provided that
 109      * the kernel's keepalive timer expires before the Postfix watchdog
 110      * timer.
 111      *
 112      * XXX Work around NAT induced damage by sending a keepalive before an idle
 113      * connection is expired. This requires that the kernel keepalive timer
 114      * is set to a short time, like 100s.
 115      */
 116     else if (sa && (sa->sa_family == AF_INET
 117 #ifdef HAS_IPV6
 118                     || sa->sa_family == AF_INET6
 119 #endif
 120                     )) {
 121         int     on = 1;
 122
 123         (void) setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE,
 124                           (char *) &on, sizeof(on));
 125     }
 126     return (fd);
 127 }