aboutsummaryrefslogtreecommitdiff
path: root/toys/net
diff options
context:
space:
mode:
Diffstat (limited to 'toys/net')
-rw-r--r--toys/net/sntp.c269
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;
+ }
+ }
+ }
+}