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qmcchem/ocaml/c_bindings.c
2019-07-17 11:49:34 +02:00

71 lines
1.8 KiB
C

#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/alloc.h>
#include <caml/custom.h>
#include <caml/threads.h>
#include <string.h>
/* Adapted from
https://github.com/monadbobo/ocaml-core/blob/master/base/core/lib/linux_ext_stubs.c
*/
#include <unistd.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
CAMLprim value get_ipv4_address_for_interface(value v_interface)
{
CAMLparam1(v_interface);
struct ifreq ifr;
int fd = -1;
value res;
char* error = NULL;
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_addr.sa_family = AF_INET;
/* [ifr] is already initialized to zero, so it doesn't matter if the
incoming string is too long, and [strncpy] fails to add a \0. */
strncpy(ifr.ifr_name, String_val(v_interface), IFNAMSIZ - 1);
caml_enter_blocking_section();
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd == -1)
error = "error: couldn't allocate socket";
else {
if (ioctl(fd, SIOCGIFADDR, &ifr) < 0)
error = "error: ioctl(fd, SIOCGIFADDR, ...) failed";
(void) close(fd);
}
caml_leave_blocking_section();
if (error == NULL) {
/* This is weird but doing the usual casting causes errors when using
* the new gcc on CentOS 6. This solution was picked up on Red Hat's
* bugzilla or something. It also works to memcpy a sockaddr into
* a sockaddr_in. This is faster hopefully.
*/
union {
struct sockaddr sa;
struct sockaddr_in sain;
} u;
u.sa = ifr.ifr_addr;
res = caml_copy_string(inet_ntoa(u.sain.sin_addr));
}
else
res = caml_copy_string(error);
CAMLreturn(res);
}