From c037bf9c5f65cb567123a7e03467e37370227f1c Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <stapelberg@google.com>
Date: Mon, 22 Oct 2018 18:39:25 +0200
Subject: [PATCH] dhcp4d: fix panic when receiving unsupported requests

---
 internal/dhcp4d/dhcp4d.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/internal/dhcp4d/dhcp4d.go b/internal/dhcp4d/dhcp4d.go
index 0cba287..3b39830 100644
--- a/internal/dhcp4d/dhcp4d.go
+++ b/internal/dhcp4d/dhcp4d.go
@@ -158,6 +158,9 @@ func (h *Handler) canLease(reqIP net.IP, hwaddr string) int {
 
 func (h *Handler) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dhcp4.Options) dhcp4.Packet {
 	reply := h.serveDHCP(p, msgType, options)
+	if reply == nil {
+		return nil // unsupported request
+	}
 	buf := gopacket.NewSerializeBuffer()
 	opts := gopacket.SerializeOptions{
 		ComputeChecksums: true,