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-rw-r--r--toys/pending/sntp.c131
1 files changed, 120 insertions, 11 deletions
diff --git a/toys/pending/sntp.c b/toys/pending/sntp.c
index f34c3da2..446e3f75 100644
--- a/toys/pending/sntp.c
+++ b/toys/pending/sntp.c
@@ -4,24 +4,30 @@
*
* See https://www.ietf.org/rfc/rfc4330.txt
-USE_SNTP(NEWTOY(sntp, "<1", TOYFLAG_USR|TOYFLAG_BIN))
+USE_SNTP(NEWTOY(sntp, "sp:", TOYFLAG_USR|TOYFLAG_BIN))
config SNTP
bool "sntp"
default n
help
- usage: sntp SERVER...
+ usage: sntp [-sm] [-p PORT] SERVER...
Simple Network Time Protocol client, set system clock from a server.
+
+ -p Use PORT (default 123)
+ -s Serer
*/
#define FOR_sntp
#include "toys.h"
GLOBALS(
- int unused;
+ char *p, *m;
)
+// Seconds from 1900 to 1970, including appropriate leap days
+#define SEVENTIES 2208988800L
+
union socksaddr {
struct sockaddr_in in;
struct sockaddr_in6 in6;
@@ -46,20 +52,123 @@ int xrecvwait(int fd, char *buf, int len, union socksaddr *sa, int timeout)
return len;
}
+/// hardwired getaddrinfo() variant for what we want here.
+static struct addrinfo *gai(char *server)
+{
+ return xgetaddrinfo(server, TT.p, AF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, 0);
+}
+
+// Get time and return ntptime (saving timespec in pointer if not null)
+// NTP time is high 32 bits = seconds since 1970 (blame RFC 868), low 32 bits
+// fraction of a second.
+static unsigned long long lunchtime(struct timespec *television)
+{
+ struct timespec tv;
+
+ clock_gettime(CLOCK_REALTIME, &tv);
+
+ if (television) *television = tv;
+
+ // Unix time is 1970 but RFCs 868 and 958 said 1900, so add seconds 1900->1970
+ // If they'd done a 34/30 bit split the Y2036 problem would be centuries
+ // from now and still give us nanosecond accuracy, but no...
+ return ((tv.tv_sec+SEVENTIES)<<32)+(((long long)tv.tv_nsec)<<32)/1000000000;
+}
+
+// convert ntptime back to struct timespec.
+static void doublyso(unsigned long long now, struct timespec *tv)
+{
+ // Y2036 fixup: if time wrapped, it's in the future
+ tv->tv_sec = (now>>32) + (1L<<32)*!(now&(1L<<63));
+ tv->tv_sec -= SEVENTIES; // Force signed math for Y2038 fixup
+ tv->tv_nsec = ((now&((1L<<32)-1))*1000000000)>>32;
+}
+
+// return difference between two timespecs in nanosecs
+static long long nanodiff(struct timespec *old, struct timespec *new)
+{
+ return (new->tv_sec - old->tv_sec)*1000000000LL+(new->tv_nsec - old->tv_nsec);
+}
+
+// Adjust timespec by nanosecond offset
+static void nanomove(struct timespec *ts, long long offset)
+{
+ long long nano = ts->tv_nsec + offset, secs = nano/1000000000;
+
+ ts->tv_sec += secs;
+ nano %= 1000000000;
+ if (nano<0) {
+ ts->tv_sec--;
+ nano += 1000000000;
+ }
+ ts->tv_nsec = nano;
+}
+
+int multicast = 0;
+
void sntp_main(void)
{
+ struct timespec tv, tv2;
+ unsigned long long *pktime = (void *)toybuf, now, then, before;
+ long long diff;
struct addrinfo *ai;
union socksaddr sa;
- int fd, len;
+ int fd, attempts;
+
+ if (!FLAG(s) && !*toys.optargs) error_exit("Need -s or SERVER");
- ai = xgetaddrinfo(*toys.optargs, 0, AF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, 0);
+ // Lookup address and open server or client UDP socket
+ if (!TT.p || !*TT.p) TT.p = "123";
+ ai = gai(*toys.optargs);
// When root, bind to local server address
- if (!getuid())
- fd = xbind(xgetaddrinfo("", "123", AF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, 0));
+ if (!getuid()) fd = xbind(gai(""));
else fd = xsocket(ai->ai_family, SOCK_DGRAM, IPPROTO_UDP);
- xsendto(fd, toybuf, 48, ai->ai_addr);
- len = xrecvwait(fd, toybuf, sizeof(toybuf), &sa, 5000);
- printf("%d\n", len);
- if (len>0) write(1, toybuf, len);
+ // Try 3 times
+ for (attempts = 0; attempts < 3; attempts++) {
+ // Prepare outgoing NTP packet
+ memset(toybuf, 0, 48);
+ *toybuf = 0xe3; // li = 3 (unsynchronized), version = 4, mode = 3 (client)
+ toybuf[2] = 8; // poll frequency 1<<8 = 256 seconds
+ pktime[5] = SWAP_BE64(before = lunchtime(&tv));
+
+ // Send and ye shall receive
+ xsendto(fd, toybuf, 48, ai->ai_addr);
+ then = (now = millitime())+4000;
+ while (now<then) {
+ // TODO: confirm sa matches
+ if (48 == xrecvwait(fd, toybuf, sizeof(toybuf), &sa, then-now)) {
+ if (multicast || pktime[3] == SWAP_BE64(before)) break;
+ }
+ now = millitime();
+ }
+ if (now < then) break;
+ }
+ lunchtime(&tv2);
+
+//printf("before) %ld %ld\n", (long)tv.tv_sec, (long)tv.tv_nsec);
+//printf("after) %ld %ld\n", (long)tv2.tv_sec, (long)tv2.tv_nsec);
+
+ // determine midpoint of packet transit time according to local clock
+ // (simple calculation: assume each direction took same time so midpoint
+ // is time reported by other clock)
+ diff = nanodiff(&tv, &tv2)/2;
+//printf("halfoff = %lld %llx\n", diff, diff);
+ nanomove(&tv, diff);
+//printf("midpoint) %ld %ld\n", (long)tv.tv_sec, (long)tv.tv_nsec);
+
+ doublyso(SWAP_BE64(pktime[5]), &tv2);
+ diff = nanodiff(&tv2, &tv);
+//printf("server) %ld %ld\n", (long)tv2.tv_sec, (long)tv2.tv_nsec);
+//printf("offby = %lld\n", diff);
+
+//int i;
+//for (i=0; i<48; ) {
+// printf("%02x", toybuf[i]);
+// if (!(++i&15)) printf("\n");
+//}
+
+ format_iso_time(toybuf, sizeof(toybuf)-1, &tv);
+ printf("%s offset %c%d.%09d secs\n", toybuf, (diff<0) ? '-' : '+',
+ abs(diff/1000000000), abs(diff%1000000000));
}