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#include "resolve.h"
/* ntpdate [SERVER]: set the clock from SNTP (default pool.ntp.org).
*
* An MBC5 cart has no RTC, so this is the only way gbos can know the real
* time. One 48-byte UDP exchange with port 123: the reply's transmit
* timestamp is seconds since 1900, and unix time is that minus 2208988800.
* The kernel keeps the stamp plus the tick it arrived at (SYS_SETTIME), so
* date(1) can add the elapsed ticks back.
*
* The clock does not survive a power cycle - put ntpdate in /rc. */
#define NTP_PORT 123
#define UNIX_EPOCH_HI 0x8383 /* 2208988800 = 0x83AA7E80 */
static unsigned char pkt[48];
static unsigned char namebuf[64];
static unsigned char srv[4];
static unsigned char now[4];
void main(void) {
char args[40];
unsigned char s, n, i;
{
char *a = getargs();
for (i = 0; a[i] && i < 39; i++) args[i] = a[i];
args[i] = 0;
}
if (!args[0]) {
const char *d = "pool.ntp.org";
for (i = 0; d[i]; i++) args[i] = d[i];
args[i] = 0;
}
for (i = 0; args[i] && i < 63; i++) namebuf[i] = (unsigned char)args[i];
namebuf[i] = 0;
if (!resolve((char *)namebuf, srv)) {
puts("ntpdate: cannot resolve ");
puts((char *)namebuf);
nl();
sexit(1);
}
for (i = 0; i < 48; i++) pkt[i] = 0;
pkt[0] = 0x1B; /* LI=0, VN=3, mode=3 (client) */
s = net_socket(SOCK_UDP);
if (s == 0xFF) {
puts("ntpdate: no socket");
nl();
sexit(1);
}
net_bind(s, 40123);
net_connect(s, srv, NTP_PORT);
net_send(s, pkt, 48);
n = net_recv(s, pkt, 48);
net_close(s);
if (n == 0xFF || n < 48) {
puts("ntpdate: no reply");
nl();
sexit(1);
}
/* transmit timestamp: seconds since 1900 at bytes 40..43, big-endian.
unix = ntp - 2208988800 ($83AA7E80), done bytewise - no long math. */
{
unsigned char b0 = pkt[43], b1 = pkt[42], b2 = pkt[41], b3 = pkt[40];
unsigned int t;
t = (unsigned int)b0 - 0x80;
now[0] = (unsigned char)t;
t = (unsigned int)b1 - 0x7E - ((t >> 8) & 1);
now[1] = (unsigned char)t;
t = (unsigned int)b2 - 0xAA - ((t >> 8) & 1);
now[2] = (unsigned char)t;
t = (unsigned int)b3 - 0x83 - ((t >> 8) & 1);
now[3] = (unsigned char)t;
}
settime(now);
puts("ntpdate: clock set from ");
puts((char *)namebuf);
nl();
}
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