attr_clnt.c

[詳解]

/*++
/* NAME
/*  attr_clnt 3
/* SUMMARY
/*  attribute query-reply client
/* SYNOPSIS
/*  #include <attr_clnt.h>
/*
/*  typedef int (*ATTR_CLNT_PRINT_FN) (VSTREAM *, int, va_list);
/*  typedef int (*ATTR_CLNT_SCAN_FN) (VSTREAM *, int, va_list);
/*
/*  ATTR_CLNT *attr_clnt_create(server, timeout, max_idle, max_ttl)
/*  const char *server;
/*  int timeout;
/*  int max_idle;
/*  int max_ttl;
/*
/*  int attr_clnt_request(client,
/*          send_flags, send_type, send_name, ..., ATTR_TYPE_END,
/*          recv_flags, recv_type, recv_name, ..., ATTR_TYPE_END)
/*  ATTR_CLNT *client;
/*  int send_flags;
/*  int send_type;
/*  const char *send_name;
/*  int recv_flags;
/*  int recv_type;
/*  const char *recv_name;
/*
/*  void    attr_clnt_free(client)
/*  ATTR_CLNT *client;
/*
/*  void    attr_clnt_control(client, name, value, ... ATTR_CLNT_CTL_END)
/*  ATTR_CLNT *client;
/*  int name;
/* DESCRIPTION
/*  This module implements a client for a simple attribute-based
/*  protocol. The default protocol is described in attr_scan_plain(3).
/*
/*  attr_clnt_create() creates a client handle. See auto_clnt(3) for
/*  a description of the arguments.
/*
/*  attr_clnt_request() sends the specified request attributes and
/*  receives a reply. The reply argument specifies a name-value table.
/*  The other arguments are as described in attr_print_plain(3). The
/*  result is the number of attributes received or -1 in case of trouble.
/*
/*  attr_clnt_free() destroys a client handle and closes its connection.
/*
/*  attr_clnt_control() allows the user to fine tune the behavior of
/*  the specified client. The arguments are a list of (name, value)
/*  terminated with ATTR_CLNT_CTL_END.
/*  The following lists the names and the types of the corresponding
/*  value arguments.
/* .IP "ATTR_CLNT_CTL_PROTO(ATTR_CLNT_PRINT_FN, ATTR_CLNT_SCAN_FN)"
/*  Specifies alternatives for the attr_plain_print() and
/*  attr_plain_scan() functions.
/* .IP "ATTR_CLNT_CTL_REQ_LIMIT(int)"
/*  The maximal number of requests per connection (default: 0,
/*  i.e. no limit).  To enable the limit, specify a value greater
/*  than zero.
/* .IP "ATTR_CLNT_CTL_TRY_LIMIT(int)"
/*  The maximal number of attempts to send a request before
/*  giving up (default: 2). To disable the limit, specify a
/*  value equal to zero.
/* .IP "ATTR_CLNT_CTL_TRY_DELAY(int)"
/*  The time in seconds between attempts to send a request
/*  (default: 1).  Specify a value greater than zero.
/* DIAGNOSTICS
/*  Warnings: communication failure.
/* SEE ALSO
/*  auto_clnt(3), client endpoint management
/*  attr_scan_plain(3), attribute protocol
/*  attr_print_plain(3), attribute protocol
/* 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 <unistd.h>
#include <errno.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <vstream.h>
#include <htable.h>
#include <attr.h>
#include <iostuff.h>
#include <compat_va_copy.h>
#include <auto_clnt.h>
#include <attr_clnt.h>

/* Application-specific. */

struct ATTR_CLNT {
    AUTO_CLNT *auto_clnt;
    /* Remaining properties are set with attr_clnt_control(). */
    ATTR_CLNT_PRINT_FN print;
    ATTR_CLNT_SCAN_FN scan;
    int     req_limit;
    int     req_count;
    int     try_limit;
    int     try_delay;
};

#define ATTR_CLNT_DEF_REQ_LIMIT (0) /* default per-session request limit */
#define ATTR_CLNT_DEF_TRY_LIMIT (2) /* default request (re)try limit */
#define ATTR_CLNT_DEF_TRY_DELAY (1) /* default request (re)try delay */

/* attr_clnt_free - destroy attribute client */

void    attr_clnt_free(ATTR_CLNT *client)
{
    auto_clnt_free(client->auto_clnt);
    myfree((void *) client);
}

/* attr_clnt_create - create attribute client */

ATTR_CLNT *attr_clnt_create(const char *service, int timeout,
                        int max_idle, int max_ttl)
{
    ATTR_CLNT *client;

    client = (ATTR_CLNT *) mymalloc(sizeof(*client));
    client->auto_clnt = auto_clnt_create(service, timeout, max_idle, max_ttl);
    client->scan = attr_vscan_plain;
    client->print = attr_vprint_plain;
    client->req_limit = ATTR_CLNT_DEF_REQ_LIMIT;
    client->req_count = 0;
    client->try_limit = ATTR_CLNT_DEF_TRY_LIMIT;
    client->try_delay = ATTR_CLNT_DEF_TRY_DELAY;
    return (client);
}

/* attr_clnt_request - send query, receive reply */

int     attr_clnt_request(ATTR_CLNT *client, int send_flags,...)
{
    const char *myname = "attr_clnt_request";
    VSTREAM *stream;
    int     count = 0;
    va_list saved_ap;
    va_list ap;
    int     type;
    int     recv_flags;
    int     err;
    int     ret;

    /*
     * XXX If the stream is readable before we send anything, then assume the
     * remote end disconnected.
     * 
     * XXX For some reason we can't simply call the scan routine after the print
     * routine, that messes up the argument list.
     */
#define SKIP_ARG(ap, type) { \
    (void) va_arg(ap, char *); \
    (void) va_arg(ap, type); \
    }
#define SKIP_ARG2(ap, t1, t2) { \
    SKIP_ARG(ap, t1); \
    (void) va_arg(ap, t2); \
    }

    /* Finalize argument lists before returning. */
    va_start(saved_ap, send_flags);
    for (;;) {
    errno = 0;
    if ((stream = auto_clnt_access(client->auto_clnt)) != 0
        && readable(vstream_fileno(stream)) == 0) {
        errno = 0;
        VA_COPY(ap, saved_ap);
        err = (client->print(stream, send_flags, ap) != 0
           || vstream_fflush(stream) != 0);
        va_end(ap);
        if (err == 0) {
        VA_COPY(ap, saved_ap);
        while ((type = va_arg(ap, int)) != ATTR_TYPE_END) {
            switch (type) {
            case ATTR_TYPE_STR:
            SKIP_ARG(ap, char *);
            break;
            case ATTR_TYPE_DATA:
            SKIP_ARG2(ap, ssize_t, char *);
            break;
            case ATTR_TYPE_INT:
            SKIP_ARG(ap, int);
            break;
            case ATTR_TYPE_LONG:
            SKIP_ARG(ap, long);
            break;
            case ATTR_TYPE_HASH:
            (void) va_arg(ap, HTABLE *);
            break;
            default:
            msg_panic("%s: unexpected attribute type %d",
                  myname, type);
            }
        }
        recv_flags = va_arg(ap, int);
        ret = client->scan(stream, recv_flags, ap);
        va_end(ap);
        /* Finalize argument lists before returning. */
        if (ret > 0) {
            if (client->req_limit > 0
            && (client->req_count += 1) >= client->req_limit) {
            auto_clnt_recover(client->auto_clnt);
            client->req_count = 0;
            }
            break;
        }
        }
    }
    if ((++count >= client->try_limit && client->try_limit > 0)
        || msg_verbose
        || (errno && errno != EPIPE && errno != ENOENT && errno != ECONNRESET))
        msg_warn("problem talking to server %s: %m",
             auto_clnt_name(client->auto_clnt));
    /* Finalize argument lists before returning. */
    if (count >= client->try_limit && client->try_limit > 0) {
        ret = -1;
        break;
    }
    sleep(client->try_delay);
    auto_clnt_recover(client->auto_clnt);
    client->req_count = 0;
    }
    /* Finalize argument lists before returning. */
    va_end(saved_ap);
    return (ret);
}

/* attr_clnt_control - fine control */

void    attr_clnt_control(ATTR_CLNT *client, int name,...)
{
    const char *myname = "attr_clnt_control";
    va_list ap;

    for (va_start(ap, name); name != ATTR_CLNT_CTL_END; name = va_arg(ap, int)) {
    switch (name) {
    case ATTR_CLNT_CTL_PROTO:
        client->print = va_arg(ap, ATTR_CLNT_PRINT_FN);
        client->scan = va_arg(ap, ATTR_CLNT_SCAN_FN);
        break;
    case ATTR_CLNT_CTL_REQ_LIMIT:
        client->req_limit = va_arg(ap, int);
        if (client->req_limit < 0)
        msg_panic("%s: bad request limit: %d",
              myname, client->req_limit);
        if (msg_verbose)
        msg_info("%s: new request limit %d",
             myname, client->req_limit);
        break;
    case ATTR_CLNT_CTL_TRY_LIMIT:
        client->try_limit = va_arg(ap, int);
        if (client->try_limit < 0)
        msg_panic("%s: bad retry limit: %d", myname, client->try_limit);
        if (msg_verbose)
        msg_info("%s: new retry limit %d", myname, client->try_limit);
        break;
    case ATTR_CLNT_CTL_TRY_DELAY:
        client->try_delay = va_arg(ap, int);
        if (client->try_delay <= 0)
        msg_panic("%s: bad retry delay: %d", myname, client->try_delay);
        if (msg_verbose)
        msg_info("%s: new retry delay %d", myname, client->try_delay);
        break;
    default:
        msg_panic("%s: bad name %d", myname, name);
    }
    }
    va_end(ap);
}