i wrote:
|Below a simple C version for the interested. It doesn't iterate
just an update with encode mode and different integer types (and
ooops bug fixes: accept a "0" adjustment and don't print print two
hyphens for negative drifts).
I wonder wether the drift shouldn't be made unsigned.
Juhuuuu,
--steffen
/*@ Fetch a PHK DNS A record and calculate current leapsecond status.
*@ Compile: $ cc -o leapsec phk-utcdrift.c
*@ Fallback: $ cc -DWANT_GETHOSTBYNAME -o leapsec phk-utcdrift.c
*@ Synopsis:
*@ Fetching: $ ./leapsec SERVER
*@ Encode: $ ./leapsec YEAR MONTH BASE-DRIFT ADJUSTMENT
*
* Public Domain.
*/
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#if defined __STDC_VERSION__ && __STDC_VERSION__ + 0 >= 199901L
# include <stdint.h>
#else
# include <inttypes.h>
#endif
#ifndef NI_MAXHOST
# define NI_MAXHOST 1025
#endif
#define _EX_OK EXIT_SUCCESS
#define _EX_USAGE 64
#define _EX_DATAERR 65
#define _EX_NOHOST 68
#ifndef NELEM
# define NELEM(X) (sizeof(X) / sizeof((X)[0]))
#endif
#ifdef UINT8_MAX
typedef uint8_t ui8_t;
typedef int8_t si8_t;
#elif UCHAR_MAX != 255
# error UCHAR_MAX must be 255
#else
typedef unsigned char ui8_t;
typedef signed char si8_t;
#endif
#ifdef UINT16_MAX
typedef uint16_t ui16_t;
typedef int16_t si16_t;
#elif USHRT_MAX != 0xFFFFu
# error USHRT_MAX must be 0xFFFF
#else
typedef unsigned short ui16_t;
typedef signed short si16_t;
#endif
#ifdef UINT32_MAX
typedef uint32_t ui32_t;
typedef int32_t si32_t;
#elif ULONG_MAX == 0xFFFFFFFFu
typedef unsigned long int ui32_t;
typedef signed long int si32_t;
#elif UINT_MAX != 0xFFFFFFFFu
# error UINT_MAX must be 0xFFFFFFFF
#else
typedef unsigned int ui32_t;
typedef signed int si32_t;
#endif
typedef enum {FAL0, TRU1} bool_t;
/*
* PHK DNS A:
* - Class E: 4-bit (0b1111)
* - Months since 1972: 10-bit
* - Base drift before leapsecond: 8-bit
* - Drift adjustment: 2-bit
* - CRC-8 PHK checksum: 8-bit
*/
struct dns_leapinfo {
ui32_t dl_addr_parts[4];
ui8_t _dl_pad1[1];
si8_t dl_adjust;
si8_t dl_drift;
ui8_t dl_month;
ui16_t dl_year;
ui8_t _dl_pad2[2];
char dl_addr[NI_MAXHOST];
};
static int _encode(char **argv, struct dns_leapinfo *dlp);
static bool_t _fetch_addr(char const *host, struct dns_leapinfo *dlp);
static bool_t _dl_addr_to_aparts(struct dns_leapinfo *dlp);
/* count specifies the number of array entries to be walked */
static ui32_t _dl_crc8_phk(struct dns_leapinfo const *dlp, ui32_t count);
static bool_t _dl_explode(struct dns_leapinfo *dlp);
int
main(int argc, char **argv)
{
struct dns_leapinfo dl;
int rv;
rv = _EX_USAGE;
if (argc != 2 && argc != 5) {
fprintf(stderr,
"Synopsis fetch : %s SERVER\n"
" encode: %s YEAR MONTH BASE-DRIFT ADJUSTMENT\n",
argv[0], argv[0]);
goto jleave;
}
if (argc == 5)
argc = _encode(argv + 1, &dl);
else {
argc = _EX_OK;
rv = _EX_NOHOST;
if (!_fetch_addr(argv[1], &dl)) {
fprintf(stderr, "! DNS failed to resolve `%s'\n", argv[1]);
goto jleave;
}
}
rv = _EX_DATAERR;
if (!_dl_addr_to_aparts(&dl)) {
fprintf(stderr, "! Bogus IP address content: `%s'\n", dl.dl_addr);
goto jprint;
}
if (_dl_crc8_phk(&dl, NELEM(dl.dl_addr_parts)) != 0) {
fprintf(stderr, "! CRC checksum failure\n");
goto jprint;
}
if (!_dl_explode(&dl)) {
fprintf(stderr, "! Bogus leapsecond data / non-class E address: `%s'\n",
dl.dl_addr);
goto jprint;
}
rv = (argc != _EX_OK) ? argc : _EX_OK;
jprint:
printf("%s -> %s %04u-%02u %s%d %s%d\n",
dl.dl_addr, (rv == _EX_OK ? "OK" : "BAD"),
(ui32_t)dl.dl_year, (ui32_t)dl.dl_month,
(dl.dl_drift < 0 ? "" : "+"), (si32_t)dl.dl_drift,
(dl.dl_adjust < 0 ? "" : "+"), (si32_t)dl.dl_adjust);
jleave:
return rv;
}
static int
_encode(char **argv, struct dns_leapinfo *dlp)
{
ui32_t y, m, i;
si32_t drift, adj;
int rv = _EX_OK;
/* Regarding strto*() handling */
printf("Warning: encode mode doesn't truly verify arguments!\n");
y = (ui32_t)strtoul(argv[0], NULL, 0);
if (y < 1972 || y > 2057) {
fprintf(stderr, "! Invalid (non-representable) year: %u\n", y);
rv = _EX_DATAERR;
}
m = (ui32_t)strtoul(argv[1], NULL, 0);
if (m < 1 || m > 12 || (y == 2057 && m > 4)) {
fprintf(stderr, "! Invalid (non-representable) month %u (for year %u)\n",
m, y);
rv = _EX_DATAERR;
}
drift = (si32_t)strtol(argv[2], NULL, 0);
if (drift < -128 || drift > 127) {
fprintf(stderr, "! Invalid (non-representable) drift: %d\n", drift);
rv = _EX_DATAERR;
}
adj = (si32_t)strtol(argv[3], NULL, 0);
if (adj < -1 || adj > 1 || adj == 0) {
fprintf(stderr, "! Invalid adjustment: %d\n", adj);
rv = _EX_DATAERR;
}
i = (y - 1972) * 12 + (m - 1);
i <<= 8;
i |= drift;
i <<= 2;
switch (adj) {
case 1: i |= 0x1; break;
case -1: i |= 0x3; break;
default: break;
}
i <<= 8;
i |= 0xF0000000u;
dlp->dl_addr_parts[0] = i >> 24;
dlp->dl_addr_parts[1] = (i >> 16) & 0xFF;
dlp->dl_addr_parts[2] = (i >> 8) & 0xFF;
dlp->dl_addr_parts[3] = _dl_crc8_phk(dlp, NELEM(dlp->dl_addr_parts) - 1);
#if defined __STDC_VERSION__ && __STDC_VERSION__ + 0 >= 199901L
snprintf
#else
sprintf
#endif
(dlp->dl_addr,
#if defined __STDC_VERSION__ && __STDC_VERSION__ + 0 >= 199901L
sizeof dlp->dl_addr,
#endif
"%u.%u.%u.%u",
dlp->dl_addr_parts[0], dlp->dl_addr_parts[1], dlp->dl_addr_parts[2],
dlp->dl_addr_parts[3]
);
return rv;
}
#ifndef WANT_GETHOSTBYNAME
static bool_t
_fetch_addr(char const *host, struct dns_leapinfo *dlp)
{
struct addrinfo hints, *res;
int i;
bool_t rv = FAL0;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
res = NULL;
if ((i = getaddrinfo(host, NULL, &hints, &res)) != 0) {
fprintf(stderr, "! Cannot resolve `%s': %s\n", host, gai_strerror(i));
goto jleave;
}
if ((i = getnameinfo(res->ai_addr, res->ai_addrlen,
dlp->dl_addr, sizeof dlp->dl_addr, NULL, 0, NI_NUMERICHOST)) != 0) {
fprintf(stderr, "! Cannot resolve name `%s': %s\n", host, gai_strerror(i));
goto jleave;
}
rv = TRU1;
jleave:
if (res != NULL)
freeaddrinfo(res);
return rv;
}
#else /* !WANT_GETHOSTBYNAME */
static bool_t
_fetch_addr(char const *host, struct dns_leapinfo *dlp)
{
struct hostent *hp;
struct in_addr *iaddr;
char const *saddr;
size_t i;
bool_t rv = FAL0;
if ((hp = gethostbyname(host)) == NULL) {
char const *emsg;
switch (h_errno) {
case HOST_NOT_FOUND:
emsg = "host not found";
break;
default:
case TRY_AGAIN:
emsg = "(maybe) try again later";
break;
case NO_RECOVERY:
emsg = "non-recoverable server error";
break;
case NO_DATA:
emsg = "valid name without IP address";
break;
}
fprintf(stderr, "! Cannot resolve `%s': %s\n", host, emsg);
goto jleave;
}
if (hp->h_addrtype != AF_INET) {
fprintf(stderr, "! DNS didn't return IPv4 address for `%s'\n", host);
goto jleave;
}
/* (Don't check h_length etc..) */
iaddr = (struct in_addr*)hp->h_addr_list[0];
saddr = inet_ntoa(*iaddr);
i = strlen(saddr) +1;
if (i <= sizeof dlp->dl_addr) {
memcpy(dlp->dl_addr, saddr, i);
rv = TRU1;
}
jleave:
return rv;
}
#endif /* WANT_GETHOSTBYNAME */
static bool_t
_dl_addr_to_aparts(struct dns_leapinfo *dlp)
{
ui32_t i;
char *eptr;
char const *sptr = dlp->dl_addr;
bool_t rv = FAL0;
for (i = 0;; ++i) {
unsigned long l = strtoul(sptr, &eptr, 10);
if (l != (ui32_t)l)
goto jleave;
dlp->dl_addr_parts[i] = (ui32_t)l;
if (sptr == eptr)
goto jleave;
switch (*eptr) {
case '.':
if (i == 3)
goto jleave;
sptr = eptr + 1;
break;
case '\0':
if (i == 3)
rv = TRU1;
/* FALLTHRU */
default:
goto jleave;
}
}
rv = TRU1;
jleave:
return rv;
}
static ui32_t
_dl_crc8_phk(struct dns_leapinfo const *dlp, ui32_t count)
{
ui32_t const poly = 0xCF;
ui32_t crc, i, slot, j, mix;
for (crc = i = 0; i < count; ++i)
for (slot = dlp->dl_addr_parts[i], j = 0; j < 8; ++j) {
mix = (crc ^ slot) & 0x01;
crc >>= 1;
if (mix != 0)
crc ^= poly;
slot >>= 1;
}
return crc;
}
static bool_t
_dl_explode(struct dns_leapinfo *dlp)
{
ui32_t i;
bool_t rv = FAL0;
i = dlp->dl_addr_parts[0] << 16;
i |= dlp->dl_addr_parts[1] << 8;
i |= dlp->dl_addr_parts[2];
/* Must be class E address */
if ((i & 0xF00000) != 0xF00000)
goto jleave;
i &= ~0xF00000;
switch ((dlp->dl_adjust = (si8_t)(i & 0x03))) {
case 0x02:
goto jleave;
case 0x03:
dlp->dl_adjust = -1;
case 0x00:
default:
break;
}
i >>= 2;
dlp->dl_drift = (si8_t)(i & 0xFF);
i >>= 8;
dlp->dl_month = (ui8_t)(i % 12) + 1;
dlp->dl_year = (ui16_t)(i / 12) + 1972;
rv = TRU1;
jleave:
return rv;
}
/* s-it2-mode */
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