On 05/14/14 18:57, Denis Fondras wrote:
> Hello all,
>
> I am burning my last neurons with a behavior I can't explain. I wonder
> why getaddrinfo() fails when called after chroot() with root user.
>
>
> I have this piece of code :
>
> /*--- test.c ---*/
> #include <sys/types.h>
> #include <stdio.h>
> #include <sys/socket.h>
> #include <netdb.h>
> #include <pwd.h>
>
> int main(int argc, char *argv[])
> {
> struct addrinfo *ai_out;
> struct passwd *pw;
> int error;
>
> pw = getpwnam("_bgpd");
>
> error = getaddrinfo("rpki.liopen.eu", NULL, NULL, &ai_out);
> if (error)
> printf("getaddrinfo() failed\n");
> else printf("getaddrinfo() succeed\n");
>
> chroot(pw->pw_dir);
> chdir("/");
>
> error = getaddrinfo("rpki.liopen.eu", NULL, NULL, &ai_out);
> if (error)
> printf("getaddrinfo() failed\n");
> else printf("getaddrinfo() succeed\n");
>
> return 0;
> }
> /*--- test.c ---*/
>
> $ ./a.out
> getaddrinfo() succeed
> getaddrinfo() succeed
>
> # ./a.out
> getaddrinfo() succeed
> getaddrinfo() succeed
>
>
>
>
> Everything is good. Now if I compile :
>
> /*--- test.c ---*/
> #include <sys/types.h>
> #include <stdio.h>
> #include <sys/socket.h>
> #include <netdb.h>
> #include <pwd.h>
>
> int main(int argc, char *argv[])
> {
> struct addrinfo *ai_out;
> struct passwd *pw;
> int error;
>
> pw = getpwnam("_bgpd");
>
> error = 0
> if (error)
> printf("getaddrinfo() failed\n");
> else printf("getaddrinfo() succeed\n");
>
> chroot(pw->pw_dir);
>
> error = getaddrinfo("rpki.liopen.eu", NULL, NULL, &ai_out);
> if (error)
> printf("getaddrinfo() failed\n");
> else printf("getaddrinfo() succeed\n");
>
> return 0;
> }
> /*--- test.c ---*/
>
> $ ./a.out
> getaddrinfo() succeed
> getaddrinfo() succeed
>
> # ./a.out
> getaddrinfo() succeed
> getaddrinfo() failed
>
>
>
> If this an expected behavior, what would be the preferred way to resolve
> a name from a chrooted process ? I am extending OpenBGPd and I need to
> resolve domain names and connect to a service (no BGP protocol). I am
> currently using the "session" process to handle the connection part but
> I am stuck on name resolution for now.
>
> Thank you in advance,
> Denis
>
I wonder if you're using the wrong function. There is gethostbyname for
forward lookups?
Regards,
-peter
