Skip metadata lines in dnsmasq leases

collector/collector.go

@@ -17,6 +17,7 @@ package collector
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"log"
 	"os"
@@ -256,6 +257,13 @@ func question(name string) dns.Question {
 }
 
 func parseLease(line string) (*lease, error) {
+	if strings.TrimSpace(line) == "" {
+		return nil, errSkipLease
+	}
+	if strings.HasPrefix(line, "duid ") || strings.HasPrefix(line, "vendorclass ") {
+		return nil, errSkipLease
+	}
+
 	arr := strings.Fields(line)
 	if got, want := len(arr), 5; got != want {
 		return nil, fmt.Errorf("illegal lease: expected %d fields, got %d", want, got)
@@ -275,6 +283,8 @@ func parseLease(line string) (*lease, error) {
 	}, nil
 }
 
+var errSkipLease = errors.New("skip lease line")
+
 // Read the DHCP lease file with the given path and return a list of leases.
 //
 // The format of the DHCP lease file written by dnsmasq is not formally
@@ -303,7 +313,11 @@ func readLeaseFile(path string) ([]lease, error) {
 	activeLeases := []lease{}
 	for i := 1; scanner.Scan(); i++ {
 		leaseLine := scanner.Text()
-		if activeLease, err := parseLease(leaseLine); err == nil {
+		activeLease, err := parseLease(leaseLine)
+		if errors.Is(err, errSkipLease) {
+			continue
+		}
+		if err == nil {
 			activeLeases = append(activeLeases, *activeLease)
 		} else {
 			log.Printf("Error parsing lease (%d, %q): %s", i, leaseLine, err)

collector/collector_test.go

@@ -15,6 +15,7 @@
 package collector
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -222,3 +223,17 @@ func fetchMetrics(t *testing.T, c *Collector) map[string]string {
 	}
 	return metrics
 }
+
+func TestParseLeaseSkipsMetadataLines(t *testing.T) {
+	t.Parallel()
+
+	for _, line := range []string{
+		"duid 00:01:00:01:ff:6f:ff:6e:aa:cf:ff:af:4a:8b",
+		"vendorclass something",
+		"   ",
+	} {
+		if lease, err := parseLease(line); !errors.Is(err, errSkipLease) || lease != nil {
+			t.Fatalf("parseLease(%q) = (%v, %v), want skip error", line, lease, err)
+		}
+	}
+}

collector/testdata/dnsmasq.leases

@@ -1,2 +1,5 @@
+duid 00:01:00:01:ff:6f:ff:6e:aa:cf:ff:af:4a:8b
+vendorclass some-vendor-info
 1625595932 00:00:00:00:00:00 10.10.10.10 host-1 00:00:00:00:00:00
-0 00:00:00:00:00:01 10.10.10.11 host-2 00:00:00:00:00:01
+0 00:00:00:00:00:01 10.10.10.11 host-2 00:00:00:00:00:01
+