diff options
Diffstat (limited to 'toys/net')
| -rw-r--r-- | toys/net/sntp.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/toys/net/sntp.c b/toys/net/sntp.c new file mode 100644 index 00000000..edccd209 --- /dev/null +++ b/toys/net/sntp.c @@ -0,0 +1,269 @@ +/* sntp.c - sntp client and server + * + * Copyright 2019 Rob Landley <rob@landley.net> + * + * See https://www.ietf.org/rfc/rfc4330.txt + + modes: oneshot display, oneshot set, persist, serve, multi + +USE_SNTP(NEWTOY(sntp, "m:Sp:asdDqr#<4>17=10[!as]", TOYFLAG_USR|TOYFLAG_BIN)) + +config SNTP + bool "sntp" + default y + help + usage: sntp [-saSdDqm] [-r SHIFT] [-m ADDRESS] [-p PORT] [SERVER] + + Simple Network Time Protocol client. Query SERVER and display time. + + -p Use PORT (default 123) + -s Set system clock suddenly + -a Adjust system clock gradually + -S Serve time instead of querying (bind to SERVER address if specified) + -m Wait for updates from multicast ADDRESS (RFC 4330 says use 224.0.1.1) + -d Daemonize (run in background re-querying ) + -D Daemonize but stay in foreground: re-query time every 1000 seconds + -r Retry shift (every 1<<SHIFT seconds) + -q Quiet (don't display time) +*/ + +#define FOR_sntp +#include "toys.h" + +GLOBALS( + long r; + 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; +}; + +// timeout in milliseconds +int xrecvwait(int fd, char *buf, int len, union socksaddr *sa, int timeout) +{ + socklen_t sl = sizeof(*sa); + + if (timeout >= 0) { + struct pollfd pfd; + + pfd.fd = fd; + pfd.events = POLLIN; + if (!xpoll(&pfd, 1, timeout)) return 0; + } + + len = recvfrom(fd, buf, len, 0, (void *)sa, &sl); + if (len<0) perror_exit("recvfrom"); + + return len; +} + +// 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; +} + +// 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. +// diff is how far off we think our clock is from reality (in nanoseconds) +static unsigned long long lunchtime(struct timespec *television, long long diff) +{ + struct timespec tv; + + clock_gettime(CLOCK_REALTIME, &tv); + if (diff) nanomove(&tv, diff); + + 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) + (1LL<<32)*!(now&(1LL<<63)); + tv->tv_sec -= SEVENTIES; // Force signed math for Y2038 fixup + tv->tv_nsec = ((now&0xFFFFFFFF)*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); +} + +void sntp_main(void) +{ + struct timespec tv, tv2; + unsigned long long *pktime = (void *)toybuf, now, then, before = before; + long long diff = 0; + struct addrinfo *ai; + union socksaddr sa; + int fd, tries = 0; + + if (!(FLAG(S)||FLAG(m)) && !*toys.optargs) + error_exit("Need -Sm or SERVER address"); + + // Lookup address and open server or client UDP socket + if (!TT.p || !*TT.p) TT.p = "123"; + ai = xgetaddrinfo(*toys.optargs, TT.p, AF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, + AI_PASSIVE*!*toys.optargs); + + if (FLAG(d) && daemon(0, 0)) perror_exit("daemonize"); + + // Act as server if necessary + if (FLAG(S)|FLAG(m)) { + fd = xbind(ai); + if (TT.m) { + struct ip_mreq group; + + // subscribe to multicast group + memset(&group, 0, sizeof(group)); + group.imr_multiaddr.s_addr = inet_addr(TT.m); + xsetsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &group, sizeof(group)); + } + } else fd = xsocket(ai->ai_family, SOCK_DGRAM, IPPROTO_UDP); + + // -Sm = loop waiting for input + // -Dd = loop polling time and waiting until next poll period + // Otherwise poll up to 3 times to get 2 responses, then exit + + // loop sending/receiving packets + for (;;) { + now = millitime(); + + // Figure out if we're in server and multicast modes don't poll + if (FLAG(m) || FLAG(S)) then = -1; + + // daemon and oneshot modes send a packet each time through outer loop + else { + then = now + 3000; + if (FLAG(d) || FLAG(D)) then = now + (1<<TT.r)*1000; + + // Send NTP query 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, diff)); + xsendto(fd, toybuf, 48, ai->ai_addr); + } + + // Loop receiving packets until it's time to send the next one. + for (;;) { + int strike; + + // Wait to receive a packet + + if (then>0 && then<(now = millitime())) break;; + strike = xrecvwait(fd, toybuf, sizeof(toybuf), &sa, then-now); + if (strike<1) { + if (!(FLAG(S)||FLAG(m)||FLAG(D)||FLAG(d)) && ++tries == 3) + error_exit("no reply from %s", *toys.optargs); + break; + } + if (strike<48) continue; + + // Validate packet + if (!FLAG(S) || FLAG(m)) { + char buf[128]; + int mode = 7&*toybuf; + + // Is source address what we expect? + xstrncpy(buf, ntop(ai->ai_addr), 128); + strike = strcmp(buf, ntop((void *)&sa)); + // Does this reply's originate timestamp match the packet we sent? + if (!FLAG(S) && !FLAG(m) && before != SWAP_BE64(pktime[3])) continue; + // Ignore packets from wrong address or with wrong mode + if (strike && !FLAG(S)) continue; + if (!((FLAG(m) && mode==5) || (FLAG(S) && mode==3) || + (!FLAG(m) && !FLAG(S) && mode==4))) continue; + } + + // If received a -S request packet, send server packet + if (strike) { + char *buf = toybuf+48; + + *buf = 0x24; // LI 0 VN 4 mode 4. + buf[1] = 3; // stratum 3 + buf[2] = 10; // recommended retry every 1<<10=1024 seconds + buf[3] = 250; // precision -6, minimum allowed + strcpy(buf+12, "LOCL"); + pktime[6+3] = pktime[5]; // send back reference time they sent us + // everything else is current time + pktime[6+2] = pktime[6+4] = pktime[6+5] = SWAP_BE64(lunchtime(0, 0)); + xsendto(fd, buf, 48, (void *)&sa); + + // Got a time packet from a recognized server + } else { + int unset = !diff; + + // First packet: figure out how far off our clock is from what server + // said and try again. Don't set clock, just record offset to use + // generating second reuest. (We know this time is in the past + // because transmission took time, but it's a start. And if time is + // miraculously exact, don't loop.) + + lunchtime(&tv2, diff); + diff = nanodiff(&tv, &tv2); + if (unset && diff) break; + + // Second packet: determine midpoint of packet transit time according + // to local clock, assuming each direction took same time so midpoint + // is time server reported. The first television was the adjusted time + // we sent the packet at, tv2 is what server replied, so now diff + // is round trip time. + + // What time did the server say and how far off are we? + nanomove(&tv, diff/2); + doublyso(SWAP_BE64(pktime[5]), &tv2); + diff = nanodiff(&tv, &tv2); + + if (FLAG(s)) { + // Do read/adjust/set to lose as little time as possible. + clock_gettime(CLOCK_REALTIME, &tv2); + nanomove(&tv2, diff); + if (clock_settime(CLOCK_REALTIME, &tv2)) + perror_exit("clock_settime"); + } else if (FLAG(a)) { + struct timeval why; + + // call adjtime() to move the clock gradually, copying nanoseconds + // into gratuitous microseconds structure for sad historical reasons + memset(&tv2, 0, sizeof(tv2)); + nanomove(&tv2, diff); + why.tv_sec = tv2.tv_sec; + why.tv_usec = tv2.tv_nsec/1000; + if (adjtime(&why, 0)) perror_exit("adjtime"); + } + + // Display the time and offset + if (!FLAG(q)) { + format_iso_time(toybuf, sizeof(toybuf)-1, &tv2); + printf("%s offset %c%lld.%09lld secs\n", toybuf, (diff<0) ? '-' : '+', + llabs(diff/1000000000), llabs(diff%1000000000)); + } + + // If we're not in daemon mode, we're done. (Can't get here for -S.) + if (!FLAG(d) && !FLAG(D)) return; + } + } + } +} |