On Fri, Mar 31, 2017 at 06:51:44PM +0000, Luke Small wrote:
> I'm not asking for help. I'm suggesting a change to the man page. This code
> performs the tasks performed in the existing examples better. The code on
> the man page fails if you perform it a second time. This code works when
> you do it twice. So if you use this code with one process sittting on a
> port, listening for socket connections and it sends those file descriptors
> to multiple processes, my examples will work and the existing one won't.
You still do not say *what* is going wrong and how you observe that.
Be explicit.
When I made the man page example code, I tested it. Various daemons
in OpenBSD use the same idiom. But if I find some time, I'll test it
with you scenario: using the code to send muliple fd's.
-Otto
>
> On Fri, Mar 31, 2017 at 11:07 AM Otto Moerbeek <[email protected]> wrote:
>
> On Fri, Mar 31, 2017 at 07:45:31AM +0000, Luke Small wrote:
>
> > I found the code from
> > http://www.techdeviancy.com/uds.html, but there are many references to
> code
> > like this on google with the line:
> > "message_buffer[0] = 'F';".
> >
> > I made an amalgamation of that code and the EXAMPLE section of
> CMSG_DATA(3):
> >
> > EXAMPLES
> > The following example constructs a control message containing a file
> > descriptor and passes it over a socket:
> >
> > struct msghdr msg;
> > struct iovec io_vector[1];
> > struct cmsghdr *cmsg;
> > char message_buffer[1];
> > char ancillary_buffer[CMSG_SPACE(sizeof(int))];
> >
> > /*
> > * at least one vector of one byte must be
> > * sent or successive reads will fail.
> > */
> > message_buffer[0] = 'F';
> > io_vector[0].iov_base = message_buffer;
> > io_vector[0].iov_len = 1;
> >
> > memset(&msg, 0, sizeof(struct msghdr));
> > msg.msg_iov = io_vector;
> > msg.msg_iovlen = 1;
> > memset(ancillary_buffer, 0, CMSG_SPACE(sizeof(int)));
> > msg.msg_control = ancillary_buffer;
> > msg.msg_controllen = CMSG_SPACE(sizeof(int));
> >
> > cmsg = CMSG_FIRSTHDR(&msg);
> > cmsg->cmsg_level = SOL_SOCKET;
> > cmsg->cmsg_type = SCM_RIGHTS;
> > cmsg->cmsg_len = CMSG_LEN(sizeof(int));
> > *((int *) CMSG_DATA(cmsg)) = fd;
> >
> > if (sendmsg(socket, &msg, 0) == -1)
> > err(1, "sendmsg");
> >
> > And an example that receives and decomposes the control message:
> >
> > struct msghdr msg;
> > struct cmsghdr *cmsg;
> > struct iovec io_vector[1];
> > char message_buffer[1];
> > char ancillary_buffer[CMSG_SPACE(sizeof(int))];
> >
> > memset(&msg, 0, sizeof(struct msghdr));
> > memset(ancillary_buffer, 0, CMSG_SPACE(sizeof(int)));
> > io_vector[0].iov_base = message_buffer;
> > io_vector[0].iov_len = 1;
> > msg.msg_iov = io_vector;
> > msg.msg_iovlen = 1;
> > msg.msg_control = ancillary_buffer;
> > msg.msg_controllen = CMSG_SPACE(sizeof(int));
> >
> > if (recvmsg(socket, &msg, 0) == -1)
> > err(1, "recvmsg");
> > if (message_buffer[0] != 'F')
> > errx(1, "corrupted message");
> > if ((msg.msg_flags & MSG_TRUNC) || (msg.msg_flags & MSG_CTRUNC))
> > errx(1, "control message truncated");
> > for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
> > cmsg = CMSG_NXTHDR(&msg, cmsg)) {
> > if (cmsg->cmsg_len == CMSG_LEN(sizeof(int)) &&
> > cmsg->cmsg_level == SOL_SOCKET &&
> > cmsg->cmsg_type == SCM_RIGHTS) {
> > fd = *((int *) CMSG_DATA(cmsg));
> > /* Do something with the descriptor. */
> > }
> > }
> >
> >
> >
> >
> > On Fri, Mar 31, 2017 at 12:03 AM Theo de Raadt <[email protected]>
> wrote:
> >
> > > This is not a "i want help" group.
> > >
> > > If you have a diff, you can try submitting it.
> > >
> > > If you don't, your questions come off very false.
> > >
>
> If you want help, this is not the right mailing list. This list is for
> bug reports.
>
> And if you send stuff to anoyther mailing list show real, complete
> example code demonstrating your problem, including a description of
> expected and observed behaviour.
>
> -Otto
