sane_connect.c

[詳解]

/*++
/* NAME
/*  sane_connect 3
/* SUMMARY
/*  sanitize connect() results
/* SYNOPSIS
/*  #include <sane_connect.h>
/*
/*  int sane_connect(sock, buf, len)
/*  int sock;
/*  struct sockaddr *buf;
/*  SOCKADDR_SIZE *len;
/* DESCRIPTION
/*  sane_connect() implements the connect(2) socket call, and maps
/*  known harmless error results to EAGAIN.
/* BUGS
/*  Bizarre systems may have other harmless error results. Such
/*  systems encourage programmers to ignore error results, and
/*  penalize programmers who code defensively.
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include "sys_defs.h"
#include <sys/socket.h>
#include <errno.h>

/* Utility library. */

#include "msg.h"
#include "sane_connect.h"

/* sane_connect - sanitize connect() results */

int     sane_connect(int sock, struct sockaddr *sa, SOCKADDR_SIZE len)
{

    /*
     * XXX Solaris select() produces false read events, so that read() blocks
     * forever on a blocking socket, and fails with EAGAIN on a non-blocking
     * socket. Turning on keepalives will fix a blocking socket provided that
     * the kernel's keepalive timer expires before the Postfix watchdog
     * timer.
     * 
     * XXX Work around NAT induced damage by sending a keepalive before an idle
     * connection is expired. This requires that the kernel keepalive timer
     * is set to a short time, like 100s.
     */
    if (sa->sa_family == AF_INET) {
    int     on = 1;

    (void) setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
              (void *) &on, sizeof(on));
    }
    return (connect(sock, sa, len));
}