So, just to help me understand, let's say that running as root wasn't a
problem. Like, if you didn't have to be root to open a raw socket.
Would that mean that the open_usrp2_socket() function would just look like
this
usrp2::open_usrp2_socket() {
int fd = socket(PF_PACKET, SOCK_RAW, htons(0xBEEF);
return fd;
}
and you wouldn't need the helper program, usrp2_socket_opener.cc? But, you
would still need the read_fd(...) and write_fd(...) functions right?
Thanks again for the help.
Devin
On Wed, Apr 15, 2009 at 4:41 PM, Eric Blossom <e...@comsec.com> wrote:
> On Wed, Apr 15, 2009 at 04:20:20PM -0400, devin kelly wrote:
> > I've been looking over the GNU Radio code and I can't seem to figure what
> is
> > being done in /usrp2/host/lib/open_usrp2_socket.cc file. Specifically,
> > lines 97 through to 128.
> >
> > What I think is happening is that a pair of connected sockets is created
> > (97) then a process is forked (102). So, the child process has it's own
> > pair of sockets? Are sockfd[0] in each process connected? That would
> > explain why sockfd[1] is closed (114) immediately after the fork, but it
> > would not explain the need for socketpair to begin with.
> >
> > So, my questions are: why is socketpair needed? What is the fork doing?
> > And, why is the socket closed right after the fork?
> >
> > Any help is appreciated.
> > Devin
>
>
> This code allows us to open a SOCK_RAW socket without being root by
> using a setuid-root helper program, usrp2_socket_opener. The setuid
> program opens the socket on our behalf and passes it back to us
> through the socket pair using the socket capability feature.
>
> Look at the code for the helper program, usrp2_socket_opener.c
> and read the man pages for each system call to see what's going on.
>
> Eric
>
--
http://users.wpi.edu/~dkelly/ <http://users.wpi.edu/%7Edkelly/>
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