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/* ISC license. */
#undef _POSIX_C_SOURCE
#undef _XOPEN_SOURCE
#ifndef _XPG4_2
#define _XPG4_2
#endif
#ifndef _BSD_SOURCE
#define _BSD_SOURCE
#endif
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <sys/uio.h>
#ifndef MSG_NOSIGNAL
#define MSG_NOSIGNAL 0
#endif
#ifndef MSG_DONTWAIT
#define MSG_DONTWAIT 0
#endif
static int ndelay_on (int fd)
{
int got = fcntl(fd, F_GETFL) ;
return (got == -1) ? -1 : fcntl(fd, F_SETFL, got | O_NONBLOCK) ;
}
static int child (int p, int fd)
{
char buf[8] ;
struct iovec v = { .iov_base = buf, .iov_len = 8 } ;
struct msghdr msg =
{
.msg_name = 0,
.msg_namelen = 0,
.msg_iov = &v,
.msg_iovlen = 1,
.msg_control = 0,
.msg_controllen = 0
} ;
fd_set rfds ;
if (ndelay_on(fd) < 0) return 111 ;
FD_ZERO(&rfds) ;
FD_SET(fd, &rfds) ;
if (write(p, "", 1) < 1) return 111 ; /* sync with the parent */
if (select(fd+1, &rfds, 0, 0, 0) < 1) return 111 ;
/* The following recvmsg may block, despite setting the fd
non-blocking. That is what we're testing. */
if (recvmsg(fd, &msg, MSG_WAITALL | MSG_DONTWAIT) < 1) return 111 ;
if (write(p, "", 1) < 1) return 111 ;
return 0 ;
}
static int parent (pid_t pid, int p, int fd)
{
char c ;
struct iovec v = { .iov_base = &c, .iov_len = 1 } ;
struct msghdr msg =
{
.msg_name = 0,
.msg_namelen = 0,
.msg_iov = &v,
.msg_iovlen = 1,
.msg_control = 0,
.msg_controllen = 0
} ;
struct timeval tv = { .tv_sec = 2, .tv_usec = 0 } ;
fd_set rfds ;
unsigned int n = p > fd ? p : fd ;
int r ;
FD_ZERO(&rfds) ;
FD_SET(p, &rfds) ;
if (read(p, &c, 1) < 1) return 111 ;
if (sendmsg(fd, &msg, MSG_NOSIGNAL) < 1) return 111 ;
for (;;)
{
r = select(n+1, &rfds, 0, 0, &tv) ;
if (r >= 0 || errno != EINTR) break ;
}
if (!r) /* child is still blocking on recvmsg() after 2 seconds */
{
kill(pid, SIGTERM) ;
return 1 ;
}
if (read(p, &c, 1) < 1) return 111 ;
return 0 ;
}
int main (void)
{
pid_t pid ;
int fd[2] ;
int p[2] ;
if (pipe(p) < 0) return 111 ;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) return 111 ;
pid = fork() ;
if (pid < 0) return 111 ;
if (!pid)
{
close(p[0]) ;
close(fd[0]) ;
return child(p[1], fd[1]) ;
}
close(p[1]) ;
close(fd[1]) ;
return parent(pid, p[0], fd[0]) ;
}
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