/*
 * 2004, Ben Winslow <rain bluecherry net>
 *
 * libc wrapper to support ACE-encoded DNS names (per IDNA, RFC 3492)
 *
 * gcc -shared -o idnawrap.so idnawrap.c -ldl \
 * 	`pkg-config --cflags --libs-only-l libidn`
 */

#include <assert.h>
#include <dlfcn.h>
#include <locale.h>
#include <idna.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#define LIBC "libc.so.6"
#define NAME "idnawrap"
#define NAMEPREFIX NAME ": "

struct hostent;
struct addrinfo;

typedef struct hostent *(ghbn_t)(const char *);
typedef int (gai_t)(const char *, const char *, const struct addrinfo *, struct addrinfo **);

void *libc;
ghbn_t *real_gethostbyname;
gai_t *real_getaddrinfo;

static void moof_init(void) __attribute__((constructor));
static void moof_fini(void) __attribute__((destructor));

static void moof_init(void)
{
	char *err;

	setlocale(LC_ALL, "");

	if ((libc = dlopen(LIBC, RTLD_NOW)) == NULL) {
		fprintf(stderr, NAMEPREFIX "fatal: error opening %s: %s\n", LIBC, dlerror());
		abort();
	}
	
	dlerror(); /* clear any previous errors */
	
	if ((real_gethostbyname = (ghbn_t *)dlsym(libc, "gethostbyname")) == NULL) {
		err = dlerror();
		fprintf(stderr, NAMEPREFIX "fatal: error resolving %s: %s\n", "gethostbyname", err != NULL ? err : "NULL symbol");
		abort();
	}

	if ((real_getaddrinfo = (gai_t *)dlsym(libc, "getaddrinfo")) == NULL) {
		err = dlerror();
		fprintf(stderr, NAMEPREFIX "fatal: error resolving %s: %s\n", "getaddrinfo", err != NULL ? err : "NULL symbol");
		abort();
	}
} 

static void moof_fini(void)
{
	if (libc != NULL)
		dlclose(libc);
}

struct hostent *gethostbyname(const char *addr)
{
	struct hostent *he = NULL;
	char *encoded;
	int same = 0;
	
	assert(addr != NULL);
	
	if (idna_to_ascii_lz(addr, &encoded, 0) == IDNA_SUCCESS) {
		he = real_gethostbyname(encoded);
		same = !strcmp(encoded, addr);
		free(encoded);

		if (he != NULL || same)
			return he;
	}
	
	return real_gethostbyname(addr);
}

int getaddrinfo(const char *addr, const char *svc, const struct addrinfo *hints, struct addrinfo **res)
{
	int ret, same = 0;
	char *encoded;
	
	if (addr != NULL && idna_to_ascii_lz(addr, &encoded, 0) == IDNA_SUCCESS) {
		ret = real_getaddrinfo(encoded, svc, hints, res);
		same = !strcmp(encoded, addr);
		free(encoded);

		if (ret == 0 || same)
			return ret;
	}
	
	return real_getaddrinfo(addr, svc, hints, res);
}