1 /* $NetBSD: fifo_rdwr_bug.c,v 1.1.1.1 2009/06/23 10:08:59 tron Exp $ */
2
3 /*++
4 /* NAME
5 /* fifo_rdwr_bug 1
6 /* SUMMARY
7 /* fifo server test program
8 /* SYNOPSIS
9 /* fifo_rdwr_bug
10 /* DESCRIPTION
11 /* fifo_rdwr_bug creates a FIFO and opens it read-write mode.
12 /* On BSD/OS 3.1 select() will report that the FIFO is readable
13 /* even before any data is written to it. Doing an actual read
14 /* causes the read to block; a non-blocking read fails.
15 /* DIAGNOSTICS
16 /* Problems are reported to the standard error stream.
17 /* LICENSE
18 /* .ad
19 /* .fi
20 /* The Secure Mailer license must be distributed with this software.
21 /* AUTHOR(S)
22 /* Wietse Venema
23 /* IBM T.J. Watson Research
24 /* P.O. Box 704
25 /* Yorktown Heights, NY 10598, USA
26 /*--*/
27
28 #include <sys_defs.h>
29 #include <sys/time.h>
30 #include <sys/param.h>
31 #include <sys/stat.h>
32 #include <stdio.h>
33 #include <fcntl.h>
34 #include <signal.h>
35 #include <unistd.h>
36 #include <stdlib.h>
37 #include <string.h>
38
39 #define FIFO_PATH "test-fifo"
40 #define perrorexit(s) { perror(s); exit(1); }
41
cleanup(void)42 static void cleanup(void)
43 {
44 printf("Removing fifo %s...\n", FIFO_PATH);
45 if (unlink(FIFO_PATH))
46 perrorexit("unlink");
47 printf("Done.\n");
48 }
49
main(int unused_argc,char ** unused_argv)50 int main(int unused_argc, char **unused_argv)
51 {
52 struct timeval tv;
53 fd_set read_fds;
54 fd_set except_fds;
55 int fd;
56
57 (void) unlink(FIFO_PATH);
58
59 printf("Creating fifo %s...\n", FIFO_PATH);
60 if (mkfifo(FIFO_PATH, 0600) < 0)
61 perrorexit("mkfifo");
62
63 printf("Opening fifo %s, read-write mode...\n", FIFO_PATH);
64 if ((fd = open(FIFO_PATH, O_RDWR, 0)) < 0) {
65 perror("open");
66 cleanup();
67 exit(1);
68 }
69 printf("Selecting the fifo for readability...\n");
70 FD_ZERO(&read_fds);
71 FD_SET(fd, &read_fds);
72 FD_ZERO(&except_fds);
73 FD_SET(fd, &except_fds);
74 tv.tv_sec = 1;
75 tv.tv_usec = 0;
76
77 switch (select(fd + 1, &read_fds, (fd_set *) 0, &except_fds, &tv)) {
78 case -1:
79 perrorexit("select");
80 default:
81 if (FD_ISSET(fd, &read_fds)) {
82 printf("Opening a fifo read-write makes it readable!!\n");
83 break;
84 }
85 case 0:
86 printf("The fifo is not readable, as it should be.\n");
87 break;
88 }
89 cleanup();
90 exit(0);
91 }
92