Add a basic regression test for DHCP parsing.

dhcp/dhcp.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"sort"
 )
 
 var magic = []byte{99, 130, 83, 99}
@@ -68,6 +69,40 @@ type Packet struct {
 	Options Options
 }
 
+func (p *Packet) testString() string {
+	var b bytes.Buffer
+	bcast := "Unicast"
+	if p.Broadcast {
+		bcast = "Broadcast"
+	}
+	fmt.Fprintf(&b, `=====
+%s
+  %#v
+  %s
+  MAC: %s
+  ClientIP: %s
+  YourIP: %s
+  RelayIP: %s
+
+  BootServerIP: %s
+  BootServerName: %s
+  BootFilename: %s
+
+  Options:
+`, p.Type, p.TransactionID, bcast, p.HardwareAddr, p.ClientAddr, p.YourAddr, p.RelayAddr, p.BootServerAddr, p.BootServerName, p.BootFilename)
+
+	var opts []int
+	for n := range p.Options {
+		opts = append(opts, n)
+	}
+	sort.Ints(opts)
+	for _, n := range opts {
+		fmt.Fprintf(&b, "    %d: %#v\n", n, p.Options[n])
+	}
+	b.WriteString("=====\n")
+	return b.String()
+}
+
 // Marshal returns the wire encoding of p.
 func (p *Packet) Marshal() ([]byte, error) {
 	if len(p.TransactionID) != 4 {

dhcp/dhcp_test.go

@@ -0,0 +1,73 @@
+package dhcp
+
+import (
+	"bytes"
+	"errors"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"go.universe.tf/netboot/pcap"
+)
+
+func udpFromPcap(fname string) ([][]byte, error) {
+	f, err := os.Open(fname)
+	if err != nil {
+		return nil, err
+	}
+	r, err := pcap.NewReader(f)
+	if err != nil {
+		return nil, err
+	}
+
+	if r.LinkType != pcap.LinkEthernet {
+		return nil, errors.New("Pcap packets are not ethernet")
+	}
+
+	ret := [][]byte{}
+	for r.Next() {
+		// Assume here that the packets are UDPv4, and just chop off
+		// the headers in front of the UDP payload
+		pkt := r.Packet()
+		hdrLen := 14                             // Ethernet header
+		hdrLen += int(pkt.Bytes[hdrLen]&0xF) * 4 // IP header
+		hdrLen += 8                              // UDP header
+		ret = append(ret, pkt.Bytes[hdrLen:])
+	}
+	if r.Err() != nil {
+		return nil, r.Err()
+	}
+
+	return ret, nil
+}
+
+func TestParse(t *testing.T) {
+	rawPkts, err := udpFromPcap("testdata/dhcp.pcap")
+	if err != nil {
+		t.Fatalf("Getting test packets from pcap: %s", err)
+	}
+
+	var pkts bytes.Buffer
+	for i, rawPkt := range rawPkts {
+		pkt, err := Unmarshal(rawPkt)
+		if err != nil {
+			t.Fatalf("Parsing DHCP packet #%d: %s", i+1, err)
+		}
+		pkts.WriteString(pkt.testString())
+	}
+
+	expectedFile := "testdata/dhcp.parsed"
+	expected, err := ioutil.ReadFile(expectedFile)
+	if err != nil {
+		t.Fatalf("Reading expected file: %s", err)
+	}
+
+	if pkts.String() != string(expected) {
+		if os.Getenv("UPDATE_TESTDATA") != "" {
+			ioutil.WriteFile(expectedFile, pkts.Bytes(), 0644)
+			t.Errorf("dhcp.pcap didn't decode to dhcp.parsed (updated dhcp.parsed)")
+		} else {
+			t.Fatalf("dhcp.pcap didn't decode to dhcp.parsed (rerun with UPDATE_TESTDATA=1 to get diff)")
+		}
+	}
+}

dhcp/testdata/dhcp.parsed

@@ -0,0 +1,68 @@
+=====
+DHCPDISCOVER
+  "\x9bN\x05W"
+  Broadcast
+  MAC: d0:50:99:4e:05:57
+  ClientIP: 0.0.0.0
+  YourIP: 0.0.0.0
+  RelayIP: 0.0.0.0
+
+  BootServerIP: 0.0.0.0
+  BootServerName: 
+  BootFilename: 
+
+  Options:
+    53: []byte{0x1}
+    55: []byte{0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0xb, 0xc, 0xd, 0xf, 0x10, 0x11, 0x12, 0x16, 0x17, 0x1c, 0x28, 0x29, 0x2a, 0x2b, 0x32, 0x33, 0x36, 0x3a, 0x3b, 0x3c, 0x42, 0x43, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87}
+    57: []byte{0x4, 0xec}
+    60: []byte{0x50, 0x58, 0x45, 0x43, 0x6c, 0x69, 0x65, 0x6e, 0x74, 0x3a, 0x41, 0x72, 0x63, 0x68, 0x3a, 0x30, 0x30, 0x30, 0x30, 0x30, 0x3a, 0x55, 0x4e, 0x44, 0x49, 0x3a, 0x30, 0x30, 0x32, 0x30, 0x30, 0x31}
+    93: []byte{0x0, 0x0}
+    94: []byte{0x1, 0x2, 0x1}
+    97: []byte{0x0, 0x0, 0x2, 0x0, 0x3, 0x0, 0x4, 0x0, 0x5, 0x0, 0x6, 0x0, 0x7, 0x0, 0x8, 0x0, 0x9}
+=====
+=====
+DHCPOFFER
+  "\x9bN\x05W"
+  Broadcast
+  MAC: d0:50:99:4e:05:57
+  ClientIP: 0.0.0.0
+  YourIP: 0.0.0.0
+  RelayIP: 0.0.0.0
+
+  BootServerIP: 0.0.0.0
+  BootServerName: 
+  BootFilename: 
+
+  Options:
+    43: []byte{0x6, 0x1, 0x3, 0x8, 0x7, 0x80, 0x0, 0x1, 0xc0, 0xa8, 0x10, 0xa, 0x9, 0xc, 0x80, 0x0, 0x9, 0x50, 0x69, 0x78, 0x69, 0x65, 0x63, 0x6f, 0x72, 0x65, 0xa, 0xa, 0x0, 0x50, 0x69, 0x78, 0x69, 0x65, 0x63, 0x6f, 0x72, 0x65, 0xff}
+    53: []byte{0x2}
+    54: []byte{0xc0, 0xa8, 0x10, 0xa}
+    60: []byte{0x50, 0x58, 0x45, 0x43, 0x6c, 0x69, 0x65, 0x6e, 0x74}
+    97: []byte{0x0, 0x0, 0x2, 0x0, 0x3, 0x0, 0x4, 0x0, 0x5, 0x0, 0x6, 0x0, 0x7, 0x0, 0x8, 0x0, 0x9}
+=====
+=====
+DHCPOFFER
+  "\x9bN\x05W"
+  Broadcast
+  MAC: d0:50:99:4e:05:57
+  ClientIP: 0.0.0.0
+  YourIP: 192.168.16.12
+  RelayIP: 0.0.0.0
+
+  BootServerIP: 192.168.16.1
+  BootServerName: 
+  BootFilename: 
+
+  Options:
+    1: []byte{0xff, 0xff, 0xff, 0x0}
+    3: []byte{0xc0, 0xa8, 0x10, 0x1}
+    6: []byte{0xc0, 0xa8, 0x10, 0x1}
+    12: []byte{0x63, 0x6f, 0x72, 0x65, 0x30, 0x31}
+    15: []byte{0x68, 0x6f, 0x6d, 0x65, 0x2e, 0x75, 0x6e, 0x69, 0x76, 0x65, 0x72, 0x73, 0x65, 0x2e, 0x74, 0x66}
+    28: []byte{0xc0, 0xa8, 0x10, 0xff}
+    51: []byte{0x0, 0x0, 0xe, 0x10}
+    53: []byte{0x2}
+    54: []byte{0xc0, 0xa8, 0x10, 0x1}
+    58: []byte{0x0, 0x0, 0x7, 0x8}
+    59: []byte{0x0, 0x0, 0xc, 0x4e}
+=====