inet_connect.c

[詳解]

/*++
/* NAME
/*  inet_connect 3
/* SUMMARY
/*  connect to TCP listener
/* SYNOPSIS
/*  #include <connect.h>
/*
/*  int inet_windowsize;
/*
/*  int inet_connect(addr, block_mode, timeout)
/*  const char *addr;
/*  int block_mode;
/*  int timeout;
/* DESCRIPTION
/*  inet_connect connects to a TCP listener at
/*  the specified address, and returns the resulting file descriptor.
/*
/*  Specify an inet_windowsize value > 0 to override the TCP
/*  window size that the client advertises to the server.
/*
/*  Arguments:
/* .IP addr
/*  The destination to connect to. The format is host:port. If no
/*  host is specified, a port on the local host is assumed.
/*  Host and port information may be given in numerical form
/*  or as symbolical names.
/* .IP block_mode
/*  Either NON_BLOCKING for a non-blocking socket, or BLOCKING for
/*  blocking mode.
/* .IP timeout
/*  Bounds the number of seconds that the operation may take. Specify
/*  a value <= 0 to disable the time limit.
/* DIAGNOSTICS
/*  The result is -1 when the connection could not be made.
/*  The nature of the error is available via the global \fIerrno\fR
/*  variable.
/*  Fatal errors: other system call failures.
/* 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 interfaces. */

#include <sys_defs.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <netdb.h>

/* Utility library. */

#include "mymalloc.h"
#include "msg.h"
#include "iostuff.h"
#include "host_port.h"
#include "sane_connect.h"
#include "connect.h"
#include "timed_connect.h"
#include "myaddrinfo.h"
#include "sock_addr.h"
#include "inet_proto.h"

static int inet_connect_one(struct addrinfo *, int, int);

/* inet_connect - connect to TCP listener */

int     inet_connect(const char *addr, int block_mode, int timeout)
{
    char   *buf;
    char   *host;
    char   *port;
    const char *parse_err;
    struct addrinfo *res;
    struct addrinfo *res0;
    int     aierr;
    int     sock;
    MAI_HOSTADDR_STR hostaddr;
    INET_PROTO_INFO *proto_info;
    int     found;

    /*
     * Translate address information to internal form. No host defaults to
     * the local host.
     */
    buf = mystrdup(addr);
    if ((parse_err = host_port(buf, &host, "localhost", &port, (char *) 0)) != 0)
    msg_fatal("%s: %s", addr, parse_err);
    if ((aierr = hostname_to_sockaddr(host, port, SOCK_STREAM, &res0)) != 0)
    msg_fatal("host/service %s/%s not found: %s",
          host, port, MAI_STRERROR(aierr));
    myfree(buf);

    proto_info = inet_proto_info();
    for (sock = -1, found = 0, res = res0; res != 0; res = res->ai_next) {

    /*
     * Safety net.
     */
    if (strchr((char *) proto_info->sa_family_list, res->ai_family) == 0) {
        msg_info("skipping address family %d for host %s",
             res->ai_family, host);
        continue;
    }
    found++;

    /*
     * In case of multiple addresses, show what address we're trying now.
     */
    if (msg_verbose) {
        SOCKADDR_TO_HOSTADDR(res->ai_addr, res->ai_addrlen,
                 &hostaddr, (MAI_SERVPORT_STR *) 0, 0);
        msg_info("trying... [%s]", hostaddr.buf);
    }
    if ((sock = inet_connect_one(res, block_mode, timeout)) < 0) {
        if (msg_verbose)
        msg_info("%m");
    } else
        break;
    }
    if (found == 0)
    msg_fatal("host not found: %s", addr);
    freeaddrinfo(res0);
    return (sock);
}

/* inet_connect_one - try to connect to one address */

static int inet_connect_one(struct addrinfo * res, int block_mode, int timeout)
{
    int     sock;

    /*
     * Create a client socket.
     */
    sock = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
    if (sock < 0)
    return (-1);

    /*
     * Window scaling workaround.
     */
    if (inet_windowsize > 0)
    set_inet_windowsize(sock, inet_windowsize);

    /*
     * Timed connect.
     */
    if (timeout > 0) {
    non_blocking(sock, NON_BLOCKING);
    if (timed_connect(sock, res->ai_addr, res->ai_addrlen, timeout) < 0) {
        close(sock);
        return (-1);
    }
    if (block_mode != NON_BLOCKING)
        non_blocking(sock, block_mode);
    return (sock);
    }

    /*
     * Maybe block until connected.
     */
    else {
    non_blocking(sock, block_mode);
    if (sane_connect(sock, res->ai_addr, res->ai_addrlen) < 0
        && errno != EINPROGRESS) {
        close(sock);
        return (-1);
    }
    return (sock);
    }
}