Some small improvements

README.md

@@ -4,7 +4,7 @@ NTPal is an in-development, incomplete, and rough around the edges implementatio
 
 ## Code Credits
 
-The code for NTPal is _very_ similar to pseudocode provided in the [NTPv4 RFC](https://datatracker.ietf.org/doc/html/rfc5905), which is nicely documented and made for a good rewriting experience. Certain changes were made based on more recent additions to projects such as [ntpd](https://github.com/ntp-project/ntp), [chrony](https://github.com/mlichvar/chrony), and others. Additionally, some care was taken to map the program's requirements into better-fit Golang structures, but there's still some room for improvement (especially regarding race conditions).
+The code for NTPal is _very_ similar to pseudocode provided in the [NTPv4 RFC](https://datatracker.ietf.org/doc/html/rfc5905), which is nicely documented and made for a good rewriting experience. Certain changes were made based on more recent additions to projects such as [ntpd](https://github.com/ntp-project/ntp), [chrony](https://github.com/mlichvar/chrony), and others. Additionally, some care was taken to map the program's requirements into better-fit Golang structures, but there's room for improvement (especially regarding race conditions).
 
 ## Usage
 
@@ -25,6 +25,12 @@ NTPal uses a configuration format similar to the [standard `ntpd` config](https:
 -   `server <address> [key _key_] [burst] [iburst] [version _version_] [prefer] [minpoll _minpoll_] [maxpoll _maxpoll_]`
 -   `driftfile <path>`
 
+Some environment variables are also available to configure the application's runtime and logging:
+
+-   `SYMMETRIC`: Set to "1" to allow symmetric active servers to connect.
+-   `INFO`: Set to "1" to print periodic system information logs.
+-   `DEBUG`: Set to "1" to print timeseries clock statistics meant for graphing.
+
 ### NTPal &mdash; Query
 
 NTPal supports a simpler "query" flag to simply obtain your device's time offset from an NTP server. Accessible via `--query` or `-q`, 5 messages are sent in an attempt to obtain the best measurement possible. This command functions almost identically to the `sntp` command shipped with OSX, though NTPal has far less functionality.

fly.toml

@@ -8,7 +8,6 @@ kill_timeout = 5
   NTP_PORT = "123"
   NTP_HOST = "fly-global-services"
   REPORT_PORT = "8080"
-  ENABLED = "1"
   INFO = "1"
 
 [[mounts]]

internal/templates/templates/index.tmpl.html

@@ -289,26 +289,23 @@ <h2>According to this server,</h2>
                 }
 
                 const { offset } = minDelayAttempt;
-                let serverTime = new Date((Date.now() / 1e3 + offset) * 1e3);
+                let serverTime = new Date(Date.now() + offset / 1e3);
 
                 // Wait for the second to hit
                 await sleep(1e3 - (serverTime % 1e3));
                 setInterval(() => {
-                    const serverTime = new Date(
-                        (Date.now() / 1e3 + offset) * 1e3
-                    );
+                    const serverTime = new Date(Date.now() + offset / 1e3);
                     displayTime(serverTime);
                 }, 1000);
 
-                serverTime = new Date((Date.now() / 1e3 + offset) * 1e3);
+                serverTime = new Date(Date.now() + offset / 1e3);
                 displayTime(serverTime);
 
                 const offsetMessage = offset < 0 ? 'ahead' : 'behind';
                 elems.offset.textContent = `${offsetMessage} by ${Math.abs(
                     offset
                 ).toFixed(3)} seconds`; // We do have up to microsecond precision, but it's not great...
                 elems.offset.classList.add('done');
-
                 elems.time.classList.add('done');
             }
 

pkg/ntp/ntp.go

@@ -18,7 +18,7 @@ const PORT = 123           // NTP port number
 const VERSION byte = 4     // NTP version number
 const TOLERANCE = 15e-6    //frequency tolerance PHI (s/s)
 const MINPOLL int8 = 6     //minimum poll exponent (64 s)
-const MAXPOLL int8 = 17    // maximum poll exponent (36 h)
+const MAXPOLL int8 = 16    // maximum poll exponent (36 h)
 const MAXDISP float64 = 16 // maximum dispersion (16 s)
 const MINDISP = 0.005      // minimum dispersion increment (s)
 const NOSYNC byte = 0x3    // leap unsync
@@ -696,8 +696,10 @@ func (system *NTPSystem) sendPoll(association *Association) {
 				if err != nil {
 					log.Fatal("Invalid address: ", association.hostname)
 				}
+				if association.srcaddr == addr {
+					hpoll++
+				}
 				association.srcaddr = addr
-				hpoll++
 				association.unreach = -1
 			}
 			association.unreach++
@@ -768,9 +770,20 @@ func (system *NTPSystem) receive(packet ReceivePacket) *TransmitPacket {
 		// else if (auth == A_ERROR)
 		// 		fast_xmit(r, M_SERV, A_CRYPTO);
 		// return;         /* M_SERV packet sent */
+	case NEWPS:
+		if !isSymmetricEnabled() {
+			return nil
+		}
+
+		association = &Association{
+			ReceivePacket: packet,
+			hmode:         SYMMETRIC_PASSIVE,
+			ephemeral:     true,
+		}
+		system.clear(association, INIT)
+		system.associations = append(system.associations, association)
 	case PROC:
-		break
-	case DSCRD:
+	default:
 		return nil
 	}
 
@@ -1086,6 +1099,9 @@ func (system *NTPSystem) clockFilter(association *Association, offset float64, d
 	for i := NSTAGE - 1; i > 0; i-- {
 		association.f[i] = association.f[i-1]
 		association.f[i].disp += PHI * (float64(system.clock.t) - association.t)
+		if association.f[i].disp > MAXDISP {
+			association.f[i].disp = MAXDISP
+		}
 		f[i] = association.f[i]
 	}
 	association.f[0].t = system.clock.t
@@ -1107,7 +1123,7 @@ func (system *NTPSystem) clockFilter(association *Association, offset float64, d
 	association.disp = 0
 	association.jitter = 0
 	for i := NSTAGE - 1; i >= 0; i-- {
-		association.disp += f[i].disp / math.Pow(2, float64(i+1))
+		association.disp = 0.5 * (association.disp + f[i].disp)
 		if i < m {
 			association.jitter += math.Pow((f[0].offset - f[i].offset), 2)
 		}
@@ -1443,8 +1459,7 @@ func (system *NTPSystem) clockUpdate(association *Association) {
 		}
 		system.reftime = association.Reftime
 		system.rootdelay = association.Rootdelay + association.delay
-		dtemp := math.Sqrt(math.Pow(association.jitter, 2) + math.Pow(system.jitter, 2))
-		dtemp += math.Max(association.disp+PHI*(float64(system.clock.t)-association.t)+
+		dtemp := math.Max(association.disp+system.jitter+PHI*(float64(system.clock.t)-association.t)+
 			math.Abs(association.offset), MINDISP)
 		system.rootdisp = association.Rootdisp + dtemp
 	/*

pkg/ntp/system.go

@@ -24,11 +24,10 @@ func stepTime(offset float64) {
 	Sec -= unixEraOffset
 
 	info("CURRENT:", NTPTimestampToTime(systemTime), "STEPPING TO:", NTPTimestampToTime(ntpTime), "OFFSET WAS:", offset)
-	if shouldSetTime() {
-		err := settimeofday.Settimeofday(Sec, Usec)
-		if err != nil {
-			info("SETTIMEOFDAYERR:", err)
-		}
+
+	err := settimeofday.Settimeofday(Sec, Usec)
+	if err != nil {
+		info("SETTIMEOFDAYERR:", err)
 	}
 }
 
@@ -50,10 +49,8 @@ func adjustTime(offset float64) {
 		Usec += 1e6
 	}
 
-	if shouldSetTime() {
-		err := adjtime.Adjtime(Sec, Usec)
-		if err != nil {
-			info("ADJTIME ERROR:", err, "offset:", offset)
-		}
+	err := adjtime.Adjtime(Sec, Usec)
+	if err != nil {
+		info("ADJTIME ERROR:", err, "offset:", offset)
 	}
 }

pkg/ntp/utils.go

@@ -5,10 +5,6 @@ import (
 	"os"
 )
 
-func shouldSetTime() bool {
-	return os.Getenv("ENABLED") == "1"
-}
-
 func info(args ...any) {
 	if isInfo() {
 		fmt.Println(args...)
@@ -28,3 +24,7 @@ func isInfo() bool {
 func isDebug() bool {
 	return os.Getenv("DEBUG") == "1"
 }
+
+func isSymmetricEnabled() bool {
+	return os.Getenv("SYMMETRIC") == "1"
+}