fix(inputs.chrony): use DGRAM for the unix socket

We must use the DGRAM type when connecting to the chrony socket. On top
of that, the socket must be duplicated in order to allow concurrent
calls to it.

Fixes influxdata#15549

Signed-off-by: Frank Villaro-Dixon <[email protected]>

plugins/inputs/chrony/chrony.go

@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"os"
+	"path"
 	"strconv"
 	"syscall"
 	"time"
@@ -38,6 +40,23 @@ func (*Chrony) SampleConfig() string {
 	return sampleConfig
 }
 
+// dialUnix opens a unixgram connection with chrony
+func dialUnix(address string) (*net.UnixConn, error) {
+	base, _ := path.Split(address)
+	local := path.Join(base, fmt.Sprintf("chronyc.%d.sock", os.Getpid()))
+	conn, err := net.DialUnix("unixgram",
+		&net.UnixAddr{Name: local, Net: "unixgram"},
+		&net.UnixAddr{Name: address, Net: "unixgram"},
+	)
+	if err != nil {
+		return nil, err
+	}
+	if err := os.Chmod(local, 0666); err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
 func (c *Chrony) Init() error {
 	// Use the configured server, if none set, we try to guess it in Start()
 	if c.Server != "" {
@@ -48,6 +67,7 @@ func (c *Chrony) Init() error {
 		}
 		switch u.Scheme {
 		case "unix":
+		case "unixdram":
 			// Keep the server unmodified
 		case "udp":
 			// Check if we do have a port and add the default port if we don't
@@ -90,7 +110,10 @@ func (c *Chrony) Start(_ telegraf.Accumulator) error {
 		}
 		switch u.Scheme {
 		case "unix":
-			conn, err := net.DialTimeout("unix", u.Path, time.Duration(c.Timeout))
+			// Actually we need a unixgram connection, allow this typo
+			// FALLTHROUGH
+		case "unixgram":
+			conn, err := dialUnix(u.Path)
 			if err != nil {
 				return fmt.Errorf("dialing %q failed: %w", c.Server, err)
 			}
@@ -106,7 +129,7 @@ func (c *Chrony) Start(_ telegraf.Accumulator) error {
 		}
 	} else {
 		// If no server is given, reproduce chronyc's behavior
-		if conn, err := net.DialTimeout("unix", "/run/chrony/chronyd.sock", time.Duration(c.Timeout)); err == nil {
+		if conn, err := dialUnix("/run/chrony/chronyd.sock"); err == nil {
 			c.Server = "unix:///run/chrony/chronyd.sock"
 			c.conn = conn
 		} else if conn, err := net.DialTimeout("udp", "127.0.0.1:323", time.Duration(c.Timeout)); err == nil {