dhcpv6: Add a fuzzing entrypoint for go-fuzz

This adds the required function for running
[go-fuzz](https://github.com/dvyukov/go-fuzz) on the dhcpv6 library.
It tests the following behaviour:
 * Parsing messages doesn't crash
 * Parsed messages are identical after being serialized and deserialized

Signed-off-by: Anatole Denis <natolumin@unverle.fr>

1 files changed, 33 insertions, 0 deletions

diff --git a/dhcpv6/fuzz.go b/dhcpv6/fuzz.go
new file mode 100644
index 0000000..3f5afef
--- /dev/null
+++ b/dhcpv6/fuzz.go
@@ -0,0 +1,33 @@
+// +build gofuzz
+
+package dhcpv6
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// Fuzz is an entrypoint for go-fuzz (github.com/dvyukov/go-fuzz)
+func Fuzz(data []byte) int {
+	msg, err := FromBytes(data)
+	if err != nil {
+		return 0
+	}
+
+	serialized := msg.ToBytes()
+	if !bytes.Equal(data, serialized) {
+		rtMsg, err := FromBytes(serialized)
+		fmt.Printf("Input:      %x\n", data)
+		fmt.Printf("Round-trip: %x\n", serialized)
+		fmt.Println("Message: ", msg.Summary())
+		fmt.Printf("Go repr: %#v\n", msg)
+		fmt.Println("round-trip reserialized: ", rtMsg.Summary())
+		fmt.Printf("Go repr: %#v\n", rtMsg)
+		if err != nil {
+			fmt.Printf("failed to parse after deserialize-serialize: %v\n", err)
+		}
+		panic("round-trip different")
+	}
+
+	return 1
+}