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