1/*++
2/* NAME
3/*	fifo_rdwr_bug 1
4/* SUMMARY
5/*	fifo server test program
6/* SYNOPSIS
7/*	fifo_rdwr_bug
8/* DESCRIPTION
9/*	fifo_rdwr_bug creates a FIFO and opens it read-write mode.
10/*	On BSD/OS 3.1 select() will report that the FIFO is readable
11/*	even before any data is written to it. Doing an actual read
12/*	causes the read to block; a non-blocking read fails.
13/* DIAGNOSTICS
14/*	Problems are reported to the standard error stream.
15/* LICENSE
16/* .ad
17/* .fi
18/*	The Secure Mailer license must be distributed with this software.
19/* AUTHOR(S)
20/*	Wietse Venema
21/*	IBM T.J. Watson Research
22/*	P.O. Box 704
23/*	Yorktown Heights, NY 10598, USA
24/*--*/
25
26#include <sys_defs.h>
27#include <sys/time.h>
28#include <sys/param.h>
29#include <sys/stat.h>
30#include <stdio.h>
31#include <fcntl.h>
32#include <signal.h>
33#include <unistd.h>
34#include <stdlib.h>
35#include <string.h>
36
37#define FIFO_PATH       "test-fifo"
38#define perrorexit(s)   { perror(s); exit(1); }
39
40static void cleanup(void)
41{
42    printf("Removing fifo %s...\n", FIFO_PATH);
43    if (unlink(FIFO_PATH))
44	perrorexit("unlink");
45    printf("Done.\n");
46}
47
48int     main(int unused_argc, char **unused_argv)
49{
50    struct timeval tv;
51    fd_set  read_fds;
52    fd_set  except_fds;
53    int     fd;
54
55    (void) unlink(FIFO_PATH);
56
57    printf("Creating fifo %s...\n", FIFO_PATH);
58    if (mkfifo(FIFO_PATH, 0600) < 0)
59	perrorexit("mkfifo");
60
61    printf("Opening fifo %s, read-write mode...\n", FIFO_PATH);
62    if ((fd = open(FIFO_PATH, O_RDWR, 0)) < 0) {
63	perror("open");
64	cleanup();
65	exit(1);
66    }
67    printf("Selecting the fifo for readability...\n");
68    FD_ZERO(&read_fds);
69    FD_SET(fd, &read_fds);
70    FD_ZERO(&except_fds);
71    FD_SET(fd, &except_fds);
72    tv.tv_sec = 1;
73    tv.tv_usec = 0;
74
75    switch (select(fd + 1, &read_fds, (fd_set *) 0, &except_fds, &tv)) {
76    case -1:
77	perrorexit("select");
78    default:
79	if (FD_ISSET(fd, &read_fds)) {
80	    printf("Opening a fifo read-write makes it readable!!\n");
81	    break;
82	}
83    case 0:
84	printf("The fifo is not readable, as it should be.\n");
85	break;
86    }
87    cleanup();
88    exit(0);
89}
90