1 files changed, 92 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/modules/isc_dhcpd/parse.go b/src/go/collectors/go.d.plugin/modules/isc_dhcpd/parse.go
new file mode 100644
index 000000000..cb4161745
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/modules/isc_dhcpd/parse.go
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package isc_dhcpd
+
+import (
+	"bufio"
+	"bytes"
+	"net"
+	"os"
+)
+
+/*
+Documentation (v4.4): https://kb.isc.org/docs/en/isc-dhcp-44-manual-pages-dhcpdleases
+
+DHCPv4 prepare declaration:
+  prepare ip-address {
+    statements...
+  }
+
+DHCPv6 prepare declaration:
+  ia_ta IAID_DUID {
+    cltt date;
+    iaaddr ipv6-address {
+      statements...
+    }
+  }
+  ia_na IAID_DUID {
+    cltt date;
+    iaaddr ipv6-address {
+      statements...
+    }
+  }
+  ia_pd IAID_DUID {
+    cltt date;
+    iaprefix ipv6-address/prefix-length {
+      statements...
+    }
+  }
+*/
+
+type leaseEntry struct {
+	ip           net.IP
+	bindingState string
+}
+
+func (l leaseEntry) hasIP() bool           { return l.ip != nil }
+func (l leaseEntry) hasBindingState() bool { return l.bindingState != "" }
+
+func parseDHCPdLeasesFile(filepath string) ([]leaseEntry, error) {
+	f, err := os.Open(filepath)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = f.Close() }()
+
+	leasesSet := make(map[string]leaseEntry)
+	l := leaseEntry{}
+	sc := bufio.NewScanner(f)
+
+	for sc.Scan() {
+		bs := bytes.TrimSpace(sc.Bytes())
+		switch {
+		case !l.hasIP() && bytes.HasPrefix(bs, []byte("lease")):
+			// "lease 192.168.0.1 {" => "192.168.0.1"
+			s := string(bs)
+			l.ip = net.ParseIP(s[6 : len(s)-2])
+		case !l.hasIP() && bytes.HasPrefix(bs, []byte("iaaddr")):
+			// "iaaddr 1985:470:1f0b:c9a::001 {" =>  "1985:470:1f0b:c9a::001"
+			s := string(bs)
+			l.ip = net.ParseIP(s[7 : len(s)-2])
+		case l.hasIP() && !l.hasBindingState() && bytes.HasPrefix(bs, []byte("binding state")):
+			// "binding state active;" => "active"
+			s := string(bs)
+			l.bindingState = s[14 : len(s)-1]
+		case bytes.HasPrefix(bs, []byte("}")):
+			if l.hasIP() && l.hasBindingState() {
+				leasesSet[l.ip.String()] = l
+			}
+			l = leaseEntry{}
+		}
+	}
+
+	if len(leasesSet) == 0 {
+		return nil, nil
+	}
+
+	leases := make([]leaseEntry, 0, len(leasesSet))
+	for _, l := range leasesSet {
+		leases = append(leases, l)
+	}
+	return leases, nil
+}