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.
>
