diff options
| -rw-r--r-- | toys/pending/sntp.c | 131 |
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)); } |