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/* ISC license. */
#undef _POSIX_C_SOURCE
#undef _XOPEN_SOURCE
#ifndef _BSD_SOURCE
#define _BSD_SOURCE
#endif
#ifndef _XPG4_2
#define _XPG4_2
#endif
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/uio.h>
union aligner_u
{
struct cmsghdr cmsghdr ;
int i ;
} ;
static int ancil_send_fd (int sock, int fd)
{
union aligner_u ancilbuf[1 + CMSG_SPACE(sizeof(int)) / sizeof(union aligner_u)] ;
char s[8] = "blahblah" ;
struct iovec v = { .iov_base = s, .iov_len = 8 } ;
struct msghdr msghdr =
{
.msg_name = 0,
.msg_namelen = 0,
.msg_iov = &v,
.msg_iovlen = 1,
.msg_flags = 0,
.msg_control = ancilbuf,
.msg_controllen = CMSG_SPACE(sizeof(int))
} ;
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr) ;
cmsg->cmsg_len = CMSG_LEN(sizeof(int)) ;
cmsg->cmsg_level = SOL_SOCKET ;
cmsg->cmsg_type = SCM_RIGHTS ;
*((int *)CMSG_DATA(cmsg)) = fd ;
if (sendmsg(sock, &msghdr, 0) < 0) return 0 ;
return 1 ;
}
static int ancil_recv_fd (int sock)
{
union aligner_u ancilbuf[1 + CMSG_SPACE(sizeof(int)) / sizeof(union aligner_u)] ;
char s[8] ;
struct iovec v = { .iov_base = s, .iov_len = 8 } ;
struct msghdr msghdr =
{
.msg_name = 0,
.msg_namelen = 0,
.msg_iov = &v,
.msg_iovlen = 1,
.msg_flags = 0,
.msg_control = ancilbuf,
.msg_controllen = CMSG_SPACE(sizeof(int))
} ;
struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr) ;
cmsg->cmsg_len = msghdr.msg_controllen ;
cmsg->cmsg_level = SOL_SOCKET ;
cmsg->cmsg_type = SCM_RIGHTS ;
*((int *)CMSG_DATA(cmsg)) = -1 ;
if (recvmsg(sock, &msghdr, 0) != 8) return -1 ;
if (memcmp(s, "blahblah", 8)) return -1 ;
return *((int *)CMSG_DATA(cmsg)) ;
}
static int client (int sock)
{
int p ;
char c ;
if (read(sock, &c, 1) < 1) return 111 ;
if (c != 'b') return 111 ;
p = ancil_recv_fd(sock) ;
if (p < 0) return 111 ;
if (read(sock, &c, 1) < 1) return 111 ;
if (c != 'a') return 111 ;
if (read(p, &c, 1) < 1) return 111 ;
if (c != 'K') return 111 ;
if (read(p, &c, 1) < 1) return 111 ;
return c ;
}
static void server (int sock)
{
int p[2] ;
char c = 1 ;
if (pipe(p) < 0) return ;
if (write(sock, "b", 1) < 1) return ;
if (!ancil_send_fd(sock, p[0])) return ;
if (write(sock, "a", 1) < 1) return ;
if (write(p[1], "K", 1) < 1) return ;
if ((close(p[0]) < 0) && (errno == EBADF)) c = 0 ;
write(p[1], &c, 1) ;
}
int main (void)
{
int fd[2] ;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, fd) < 0) return 111 ;
switch (fork())
{
case -1 : return 111 ;
case 0 : close(fd[0]) ; server(fd[1]) ; return 0 ;
default : close(fd[1]) ; return client(fd[0]) ;
}
}
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