1#include <sys/select.h>
2#include <err.h>
3#include <errno.h>
4#include <fcntl.h>
5#include <stdio.h>
6#include <stdlib.h>
7#include <string.h>
8#include <unistd.h>
9
10#define BIG_PIPE_SIZE  64*1024 /* From sys/pipe.h */
11
12/*
13 * Test for the non-blocking big pipe bug (write(2) returning
14 * EAGAIN while select(2) returns the descriptor as ready for write).
15 */
16
17static void
18write_frame(int fd, char *buf, unsigned long buflen)
19{
20	fd_set wfd;
21	int i;
22
23	while (buflen) {
24		FD_ZERO(&wfd);
25		FD_SET(fd, &wfd);
26		i = select(fd+1, NULL, &wfd, NULL, NULL);
27		if (i < 0)
28			err(1, "select failed");
29		if (i != 1) {
30			errx(1, "select returned unexpected value %d\n", i);
31			exit(1);
32		}
33		i = write(fd, buf, buflen);
34		if (i < 0) {
35			if (errno != EAGAIN)
36				warn("write failed");
37			exit(1);
38		}
39		buf += i;
40		buflen -= i;
41	}
42}
43
44int
45main(void)
46{
47	/* any value over PIPE_SIZE should do */
48	char buf[BIG_PIPE_SIZE];
49	int i, flags, fd[2];
50
51	if (pipe(fd) < 0)
52		errx(1, "pipe failed");
53
54	flags = fcntl(fd[1], F_GETFL);
55	if (flags == -1 || fcntl(fd[1], F_SETFL, flags|O_NONBLOCK) == -1) {
56		printf("fcntl failed: %s\n", strerror(errno));
57		exit(1);
58	}
59
60	switch (fork()) {
61	case -1:
62		err(1, "fork failed: %s\n", strerror(errno));
63		break;
64	case 0:
65		close(fd[1]);
66		for (;;) {
67			/* Any small size should do */
68			i = read(fd[0], buf, 256);
69			if (i == 0)
70				break;
71			if (i < 0)
72				err(1, "read");
73		}
74		exit(0);
75	default:
76		break;
77	}
78
79	close(fd[0]);
80	memset(buf, 0, sizeof buf);
81	for (i = 0; i < 1000; i++)
82		write_frame(fd[1], buf, sizeof buf);
83
84	printf("ok\n");
85	exit(0);
86}
87