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#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <assert.h>
#include <err.h>
#include <stdlib.h>
static int own_child(int *us)
{
int pid;
int s[2];
struct msghdr mh;
char crap[1024];
struct iovec iov;
struct cmsghdr *c;
int *fd;
int rc;
pid = fork();
if (pid == -1)
err(1, "fork()");
if (pid) {
close(us[1]);
return pid;
}
close(us[0]);
memset(&mh, 0, sizeof(mh));
iov.iov_base = "a";
iov.iov_len = 1;
mh.msg_iov = &iov;
mh.msg_iovlen = 1;
mh.msg_control = crap;
mh.msg_controllen = sizeof(crap);
c = CMSG_FIRSTHDR(&mh);
assert(c);
c->cmsg_level = SOL_SOCKET;
c->cmsg_type = SCM_RIGHTS;
fd = (int*) CMSG_DATA(c);
assert(fd);
c->cmsg_len = CMSG_LEN(sizeof(int));
mh.msg_controllen = c->cmsg_len;
while (1) {
if (socketpair(PF_UNIX, SOCK_STREAM, 0, s) == -1)
err(1, "socketpair()");
*fd = s[0];
rc = sendmsg(us[1], &mh, 0);
if (rc == -1)
err(1, "sendmsg()");
if (rc != iov.iov_len)
errx(1, "sent short");
close(s[0]);
close(us[1]);
us[1] = s[1];
}
}
static void own(void)
{
static int pid;
static int us[2];
char crap[1024];
char morte[1024];
struct cmsghdr *c;
int rc;
struct msghdr mh;
struct iovec iov;
int *fds;
if (!pid) {
if (socketpair(PF_UNIX, SOCK_STREAM, 0, us) == -1)
err(1, "socketpair()");
pid = own_child(us);
}
iov.iov_base = morte;
iov.iov_len = sizeof(morte);
memset(&mh, 0, sizeof(mh));
mh.msg_iov = &iov;
mh.msg_iovlen = 1;
mh.msg_control = crap;
mh.msg_controllen = sizeof(crap);
rc = recvmsg(us[0], &mh, 0);
if (rc == -1)
err(1, "recvmsg()");
if (rc == 0)
errx(1, "EOF");
c = CMSG_FIRSTHDR(&mh);
assert(c);
assert(c->cmsg_type == SCM_RIGHTS);
fds = (int*) CMSG_DATA(c);
assert(fds);
close(us[0]);
us[0] = *fds;
}
int main(int argc, char *argv[])
{
own();
exit(0);
}
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