Merge branch 'iprange' into 'master'

[iprange] Fuzzing task.

See merge request slon/shad-go-private!69

iprange/README.md

@@ -0,0 +1,34 @@
+## iprange [BONUS]
+
+В этой задаче вам предстоит познакомиться с фаззингом, и его нативной поддержкой в go.
+
+Нужно поправить баг в функции `ParseList`.
+
+`ParseList` принимает на вход строку с описанием рейнджей ip адрессов в одном из `n` форматов
+* `10.0.0.1`
+* `10.0.0.0/24`
+* `10.0.0.*`
+* `10.0.0.1-10`
+
+и возвращает список пар `(min ip, max ip)` (см. [example](./example_test.go)).
+
+Для обнаружения бага (crash функции) предлагается написать fuzz тест на функцию `ParseList`.
+
+#### Проверка решения
+
+Во-первых должны работать имеющиеся тесты
+```
+go test -v ./iprange...
+```
+
+Во-вторых, в CI есть приватные тесты, молча падающие на неправильной `ParseList`.
+
+Как запустить fuzz тесты?
+```
+go test -v -fuzz=. ./iprange...
+```
+
+### Ссылки
+
+* fuzzing tutorial https://go.dev/doc/tutorial/fuzz
+* fuzzing design draft https://go.googlesource.com/proposal/+/master/design/draft-fuzzing.md

iprange/example_test.go

@@ -0,0 +1,25 @@
+package iprange_test
+
+import (
+	"fmt"
+	"log"
+
+	"gitlab.com/slon/shad-go/iprange"
+)
+
+func ExampleParseList() {
+	list, err := iprange.ParseList("10.0.0.1, 10.0.0.5-10, 192.168.1.*, 192.168.10.0/24")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, i := range list {
+		fmt.Println(i)
+	}
+
+	// Output:
+	// {10.0.0.1 10.0.0.1}
+	// {10.0.0.5 10.0.0.10}
+	// {192.168.1.0 192.168.1.255}
+	// {192.168.10.0 192.168.10.255}
+}

iprange/funcs.go

@@ -0,0 +1,94 @@
+//go:build !solution
+
+package iprange
+
+import (
+	"encoding/binary"
+	"net"
+	"sort"
+)
+
+func streamRange(lower, upper net.IP) chan net.IP {
+	ipchan := make(chan net.IP, 1)
+
+	rangeMask := net.IP([]byte{
+		upper[0] - lower[0],
+		upper[1] - lower[1],
+		upper[2] - lower[2],
+		upper[3] - lower[3],
+	})
+
+	go func() {
+		defer close(ipchan)
+
+		lower32 := binary.BigEndian.Uint32([]byte(lower))
+		upper32 := binary.BigEndian.Uint32([]byte(upper))
+		diff := upper32 - lower32
+
+		if diff < 0 {
+			panic("Lower address is actually higher than upper address.")
+		}
+
+		mask := net.IP([]byte{0, 0, 0, 0})
+
+		for {
+			ipchan <- net.IP([]byte{
+				lower[0] + mask[0],
+				lower[1] + mask[1],
+				lower[2] + mask[2],
+				lower[3] + mask[3],
+			})
+
+			if mask.Equal(rangeMask) {
+				break
+			}
+
+			for i := 3; i >= 0; i-- {
+				if rangeMask[i] > 0 {
+					if mask[i] < rangeMask[i] {
+						mask[i] = mask[i] + 1
+						break
+					} else {
+						mask[i] = mask[i] % rangeMask[i]
+						if i < 1 {
+							break
+						}
+					}
+				}
+			}
+		}
+
+	}()
+
+	return ipchan
+}
+
+// Expand expands an address with a mask taken from a stream
+func (r *AddressRange) Expand() []net.IP {
+	ips := []net.IP{}
+	for ip := range streamRange(r.Min, r.Max) {
+		ips = append(ips, ip)
+	}
+	return ips
+}
+
+// Expand expands and normalizes a set of parsed target specifications
+func (l AddressRangeList) Expand() []net.IP {
+	var res []net.IP
+	for i := range l {
+		res = append(res, l[i].Expand()...)
+	}
+	return normalize(res)
+}
+
+func normalize(src []net.IP) []net.IP {
+	sort.Sort(asc(src))
+	dst := make([]net.IP, 1, len(src))
+	dst[0] = src[0]
+	for i := range src {
+		if !dst[len(dst)-1].Equal(src[i]) {
+			dst = append(dst, src[i])
+		}
+	}
+	return dst
+}

iprange/iprange_test.go

@@ -0,0 +1,172 @@
+package iprange
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSimpleAddress(t *testing.T) {
+	ipRange, err := Parse("192.168.1.1")
+	assert.Nil(t, err)
+
+	assert.Equal(t, net.IPv4(192, 168, 1, 1).To4(), ipRange.Min)
+	assert.Equal(t, ipRange.Min, ipRange.Max)
+}
+
+func TestCIDRAddress(t *testing.T) {
+	{
+		ipRange, err := Parse("192.168.1.1/24")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(192, 168, 1, 0).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(192, 168, 1, 255).To4(), ipRange.Max)
+	}
+
+	{
+		ipRange, err := Parse("192.168.2.1/24")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(192, 168, 2, 0).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(192, 168, 2, 255).To4(), ipRange.Max)
+
+		out := ipRange.Expand()
+		assert.Equal(t, int(0xffffffff-0xffffff00), len(out)-1)
+		for i := 0; i < 256; i++ {
+			assert.Equal(t, net.IP([]byte{192, 168, 2, byte(i)}), out[i])
+		}
+	}
+
+	{
+		ipRange, err := Parse("10.1.2.3/16")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(10, 1, 0, 0).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(10, 1, 255, 255).To4(), ipRange.Max)
+
+		out := ipRange.Expand()
+		assert.Equal(t, int(0xffffffff-0xffff0000), len(out)-1)
+		for i := 0; i < 65536; i++ {
+			assert.Equal(t, net.IP([]byte{10, 1, byte(i / 256), byte(i % 256)}), out[i])
+		}
+	}
+
+	{
+		ipRange, err := Parse("10.1.2.3/32")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(10, 1, 2, 3).To4(), ipRange.Min)
+		assert.Equal(t, ipRange.Min, ipRange.Max)
+	}
+}
+
+func TestWildcardAddress(t *testing.T) {
+	ipRange, err := Parse("192.168.1.*")
+	assert.Nil(t, err)
+
+	assert.Equal(t, net.IPv4(192, 168, 1, 0).To4(), ipRange.Min)
+	assert.Equal(t, net.IPv4(192, 168, 1, 255).To4(), ipRange.Max)
+}
+
+func TestRangeAddress(t *testing.T) {
+	{
+		ipRange, err := Parse("192.168.1.10-20")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(192, 168, 1, 10).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(192, 168, 1, 20).To4(), ipRange.Max)
+	}
+
+	{
+		ipRange, err := Parse("192.168.10-20.1")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(192, 168, 10, 1).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(192, 168, 20, 1).To4(), ipRange.Max)
+	}
+
+	{
+		ipRange, err := Parse("0-255.1.1.1")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(0, 1, 1, 1).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(255, 1, 1, 1).To4(), ipRange.Max)
+	}
+
+	{
+		ipRange, err := Parse("1-2.3-4.5-6.7-8")
+		assert.Nil(t, err)
+
+		assert.Equal(t, net.IPv4(1, 3, 5, 7).To4(), ipRange.Min)
+		assert.Equal(t, net.IPv4(2, 4, 6, 8).To4(), ipRange.Max)
+
+		out := ipRange.Expand()
+
+		assert.Equal(t, 16, len(out))
+		assert.Equal(t, out, []net.IP{
+			net.IP([]byte{1, 3, 5, 7}),
+			net.IP([]byte{1, 3, 5, 8}),
+			net.IP([]byte{1, 3, 6, 7}),
+			net.IP([]byte{1, 3, 6, 8}),
+			net.IP([]byte{1, 4, 5, 7}),
+			net.IP([]byte{1, 4, 5, 8}),
+			net.IP([]byte{1, 4, 6, 7}),
+			net.IP([]byte{1, 4, 6, 8}),
+			net.IP([]byte{2, 3, 5, 7}),
+			net.IP([]byte{2, 3, 5, 8}),
+			net.IP([]byte{2, 3, 6, 7}),
+			net.IP([]byte{2, 3, 6, 8}),
+			net.IP([]byte{2, 4, 5, 7}),
+			net.IP([]byte{2, 4, 5, 8}),
+			net.IP([]byte{2, 4, 6, 7}),
+			net.IP([]byte{2, 4, 6, 8}),
+		})
+	}
+}
+
+func TestMixedAddress(t *testing.T) {
+	ipRange, err := Parse("192.168.10-20.*/25")
+	assert.Nil(t, err)
+
+	assert.Equal(t, net.IPv4(192, 168, 10, 0).To4(), ipRange.Min)
+	assert.Equal(t, net.IPv4(192, 168, 10, 127).To4(), ipRange.Max)
+}
+
+func TestList(t *testing.T) {
+	rangeList, err := ParseList("192.168.1.1, 192.168.1.1/24, 192.168.1.*, 192.168.1.10-20")
+	assert.Nil(t, err)
+	assert.Len(t, rangeList, 4)
+
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 1}), rangeList[0].Min)
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 1}), rangeList[0].Max)
+
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 0}), rangeList[1].Min)
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 255}), rangeList[1].Max)
+
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 0}), rangeList[2].Min)
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 255}), rangeList[2].Max)
+
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 10}), rangeList[3].Min)
+	assert.Equal(t, net.IP([]byte{192, 168, 1, 20}), rangeList[3].Max)
+}
+
+func TestBadAddress(t *testing.T) {
+	ipRange, err := Parse("192.168.10")
+	assert.Nil(t, ipRange)
+	assert.Error(t, err)
+}
+
+func TestBadList(t *testing.T) {
+	rangeList, err := ParseList("192.168.1,, 192.168.1.1/24, 192.168.1.*, 192.168.1.10-20")
+	assert.Error(t, err)
+	assert.Nil(t, rangeList)
+}
+
+func TestListExpansion(t *testing.T) {
+	rangeList, err := ParseList("192.168.1.10, 192.168.1.1-20, 192.168.1.10/29")
+	assert.Nil(t, err)
+
+	expanded := rangeList.Expand()
+	assert.Len(t, expanded, 20)
+}

iprange/lex.go

@@ -0,0 +1,86 @@
+//go:build !solution
+
+package iprange
+
+import (
+	"bytes"
+	"errors"
+	"log"
+	"strconv"
+	"unicode/utf8"
+)
+
+const eof = 0
+
+type ipLex struct {
+	line   []byte
+	peek   rune
+	output AddressRangeList
+	err    error
+}
+
+func (ip *ipLex) Lex(yylval *ipSymType) int {
+	for {
+		c := ip.next()
+		switch c {
+		case eof:
+			return eof
+		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			return ip.byte(c, yylval)
+		default:
+			return int(c)
+		}
+	}
+}
+
+func (ip *ipLex) byte(c rune, yylval *ipSymType) int {
+	add := func(b *bytes.Buffer, c rune) {
+		if _, err := b.WriteRune(c); err != nil {
+			log.Fatalf("WriteRune: %s", err)
+		}
+	}
+	var b bytes.Buffer
+	add(&b, c)
+L:
+	for {
+		c = ip.next()
+		switch c {
+		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+			add(&b, c)
+		default:
+			break L
+		}
+	}
+	if c != eof {
+		ip.peek = c
+	}
+	octet, err := strconv.ParseUint(b.String(), 10, 32)
+	if err != nil {
+		log.Printf("badly formatted octet")
+		return eof
+	}
+	yylval.num = byte(octet)
+	return num
+}
+
+func (ip *ipLex) next() rune {
+	if ip.peek != eof {
+		r := ip.peek
+		ip.peek = eof
+		return r
+	}
+	if len(ip.line) == 0 {
+		return eof
+	}
+	c, size := utf8.DecodeRune(ip.line)
+	ip.line = ip.line[size:]
+	if c == utf8.RuneError && size == 1 {
+		log.Print("invalid utf8")
+		return ip.next()
+	}
+	return c
+}
+
+func (ip *ipLex) Error(s string) {
+	ip.err = errors.New(s)
+}

iprange/sortip.go

@@ -0,0 +1,29 @@
+//go:build !solution
+
+package iprange
+
+import (
+	"math/big"
+	"net"
+)
+
+// Asc implements sorting in ascending order for IP addresses
+type asc []net.IP
+
+func (a asc) Len() int {
+	return len(a)
+}
+
+func (a asc) Swap(i, j int) {
+	a[i], a[j] = a[j], a[i]
+}
+
+func (a asc) Less(i, j int) bool {
+	bigi := big.NewInt(0).SetBytes(a[i])
+	bigj := big.NewInt(0).SetBytes(a[j])
+
+	if bigi.Cmp(bigj) == -1 {
+		return true
+	}
+	return false
+}

iprange/y.go

@@ -0,0 +1,540 @@
+//go:build !solution
+
+package iprange
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+)
+
+type AddressRangeList []AddressRange
+
+type AddressRange struct {
+	Min net.IP
+	Max net.IP
+}
+
+type octetRange struct {
+	min byte
+	max byte
+}
+
+type ipSymType struct {
+	yys       int
+	num       byte
+	octRange  octetRange
+	addrRange AddressRange
+	result    AddressRangeList
+}
+
+const num = 57346
+
+var ipToknames = [...]string{
+	"$end",
+	"error",
+	"$unk",
+	"num",
+	"','",
+	"' '",
+	"'/'",
+	"'.'",
+	"'*'",
+	"'-'",
+}
+var ipStatenames = [...]string{}
+
+const ipEofCode = 1
+const ipErrCode = 2
+const ipInitialStackSize = 16
+
+// ParseList takes a list of target specifications and returns a list of ranges,
+// even if the list contains a single element.
+func ParseList(in string) (AddressRangeList, error) {
+	lex := &ipLex{line: []byte(in)}
+	errCode := ipParse(lex)
+	if errCode != 0 || lex.err != nil {
+		return nil, fmt.Errorf("could not parse target: %w", lex.err)
+	}
+	return lex.output, nil
+}
+
+// Parse takes a single target specification and returns a range. It effectively calls ParseList
+// and returns the first result
+func Parse(in string) (*AddressRange, error) {
+	l, err := ParseList(in)
+	if err != nil {
+		return nil, err
+	}
+	return &l[0], nil
+}
+
+var ipExca = [...]int{
+	-1, 1,
+	1, -1,
+	-2, 0,
+}
+
+const ipNprod = 12
+const ipPrivate = 57344
+
+var ipTokenNames []string
+var ipStates []string
+
+const ipLast = 22
+
+var ipAct = [...]int{
+
+	4, 5, 12, 20, 2, 10, 6, 18, 11, 14,
+	9, 17, 16, 13, 15, 8, 1, 7, 3, 19,
+	0, 21,
+}
+var ipPact = [...]int{
+
+	-3, 5, -1000, -2, 0, -8, -1000, -1000, -3, 3,
+	10, -3, 7, -1000, -1000, -1000, -1, -1000, -3, -5,
+	-3, -1000,
+}
+var ipPgo = [...]int{
+
+	0, 18, 4, 0, 17, 16, 15,
+}
+var ipR1 = [...]int{
+
+	0, 5, 5, 6, 6, 2, 2, 1, 3, 3,
+	3, 4,
+}
+var ipR2 = [...]int{
+
+	0, 1, 3, 1, 2, 3, 1, 7, 1, 1,
+	1, 3,
+}
+var ipChk = [...]int{
+
+	-1000, -5, -2, -1, -3, 4, 9, -4, -6, 5,
+	7, 8, 10, -2, 6, 4, -3, 4, 8, -3,
+	8, -3,
+}
+var ipDef = [...]int{
+
+	0, -2, 1, 6, 0, 8, 9, 10, 0, 3,
+	0, 0, 0, 2, 4, 5, 0, 11, 0, 0,
+	0, 7,
+}
+var ipTok1 = [...]int{
+
+	1, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+	3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+	3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+	3, 3, 6, 3, 3, 3, 3, 3, 3, 3,
+	3, 3, 9, 3, 5, 10, 8, 7,
+}
+var ipTok2 = [...]int{
+
+	2, 3, 4,
+}
+var ipTok3 = [...]int{
+	0,
+}
+
+var ipErrorMessages = [...]struct {
+	state int
+	token int
+	msg   string
+}{}
+
+/*	parser for yacc output	*/
+
+var (
+	ipDebug        = 0
+	ipErrorVerbose = false
+)
+
+type ipLexer interface {
+	Lex(lval *ipSymType) int
+	Error(s string)
+}
+
+type ipParser interface {
+	Parse(ipLexer) int
+	Lookahead() int
+}
+
+type ipParserImpl struct {
+	lval  ipSymType
+	stack [ipInitialStackSize]ipSymType
+	char  int
+}
+
+func (p *ipParserImpl) Lookahead() int {
+	return p.char
+}
+
+func ipNewParser() ipParser {
+	return &ipParserImpl{}
+}
+
+const ipFlag = -1000
+
+func ipTokname(c int) string {
+	if c >= 1 && c-1 < len(ipToknames) {
+		if ipToknames[c-1] != "" {
+			return ipToknames[c-1]
+		}
+	}
+	return fmt.Sprintf("tok-%v", c)
+}
+
+func ipStatname(s int) string {
+	if s >= 0 && s < len(ipStatenames) {
+		if ipStatenames[s] != "" {
+			return ipStatenames[s]
+		}
+	}
+	return fmt.Sprintf("state-%v", s)
+}
+
+func ipErrorMessage(state, lookAhead int) string {
+	const TOKSTART = 4
+
+	if !ipErrorVerbose {
+		return "syntax error"
+	}
+
+	for _, e := range ipErrorMessages {
+		if e.state == state && e.token == lookAhead {
+			return "syntax error: " + e.msg
+		}
+	}
+
+	res := "syntax error: unexpected " + ipTokname(lookAhead)
+
+	// To match Bison, suggest at most four expected tokens.
+	expected := make([]int, 0, 4)
+
+	// Look for shiftable tokens.
+	base := ipPact[state]
+	for tok := TOKSTART; tok-1 < len(ipToknames); tok++ {
+		if n := base + tok; n >= 0 && n < ipLast && ipChk[ipAct[n]] == tok {
+			if len(expected) == cap(expected) {
+				return res
+			}
+			expected = append(expected, tok)
+		}
+	}
+
+	if ipDef[state] == -2 {
+		i := 0
+		for ipExca[i] != -1 || ipExca[i+1] != state {
+			i += 2
+		}
+
+		// Look for tokens that we accept or reduce.
+		for i += 2; ipExca[i] >= 0; i += 2 {
+			tok := ipExca[i]
+			if tok < TOKSTART || ipExca[i+1] == 0 {
+				continue
+			}
+			if len(expected) == cap(expected) {
+				return res
+			}
+			expected = append(expected, tok)
+		}
+
+		// If the default action is to accept or reduce, give up.
+		if ipExca[i+1] != 0 {
+			return res
+		}
+	}
+
+	for i, tok := range expected {
+		if i == 0 {
+			res += ", expecting "
+		} else {
+			res += " or "
+		}
+		res += ipTokname(tok)
+	}
+	return res
+}
+
+func iplex1(lex ipLexer, lval *ipSymType) (char, token int) {
+	token = 0
+	char = lex.Lex(lval)
+	if char <= 0 {
+		token = ipTok1[0]
+		goto out
+	}
+	if char < len(ipTok1) {
+		token = ipTok1[char]
+		goto out
+	}
+	if char >= ipPrivate {
+		if char < ipPrivate+len(ipTok2) {
+			token = ipTok2[char-ipPrivate]
+			goto out
+		}
+	}
+	for i := 0; i < len(ipTok3); i += 2 {
+		token = ipTok3[i+0]
+		if token == char {
+			token = ipTok3[i+1]
+			goto out
+		}
+	}
+
+out:
+	if token == 0 {
+		token = ipTok2[1] /* unknown char */
+	}
+	if ipDebug >= 3 {
+		fmt.Printf("lex %s(%d)\n", ipTokname(token), uint(char))
+	}
+	return char, token
+}
+
+func ipParse(iplex ipLexer) int {
+	return ipNewParser().Parse(iplex)
+}
+
+func (iprcvr *ipParserImpl) Parse(iplex ipLexer) int {
+	var ipn int
+	var ipVAL ipSymType
+	var ipDollar []ipSymType
+	_ = ipDollar // silence set and not used
+	ipS := iprcvr.stack[:]
+
+	Nerrs := 0   /* number of errors */
+	Errflag := 0 /* error recovery flag */
+	ipstate := 0
+	iprcvr.char = -1
+	iptoken := -1 // iprcvr.char translated into internal numbering
+	defer func() {
+		// Make sure we report no lookahead when not parsing.
+		ipstate = -1
+		iprcvr.char = -1
+		iptoken = -1
+	}()
+	ipp := -1
+	goto ipstack
+
+ret0:
+	return 0
+
+ret1:
+	return 1
+
+ipstack:
+	/* put a state and value onto the stack */
+	if ipDebug >= 4 {
+		fmt.Printf("char %v in %v\n", ipTokname(iptoken), ipStatname(ipstate))
+	}
+
+	ipp++
+	if ipp >= len(ipS) {
+		nyys := make([]ipSymType, len(ipS)*2)
+		copy(nyys, ipS)
+		ipS = nyys
+	}
+	ipS[ipp] = ipVAL
+	ipS[ipp].yys = ipstate
+
+ipnewstate:
+	ipn = ipPact[ipstate]
+	if ipn <= ipFlag {
+		goto ipdefault /* simple state */
+	}
+	if iprcvr.char < 0 {
+		iprcvr.char, iptoken = iplex1(iplex, &iprcvr.lval)
+	}
+	ipn += iptoken
+	if ipn < 0 || ipn >= ipLast {
+		goto ipdefault
+	}
+	ipn = ipAct[ipn]
+	if ipChk[ipn] == iptoken { /* valid shift */
+		iprcvr.char = -1
+		iptoken = -1
+		ipVAL = iprcvr.lval
+		ipstate = ipn
+		if Errflag > 0 {
+			Errflag--
+		}
+		goto ipstack
+	}
+
+ipdefault:
+	/* default state action */
+	ipn = ipDef[ipstate]
+	if ipn == -2 {
+		if iprcvr.char < 0 {
+			iprcvr.char, iptoken = iplex1(iplex, &iprcvr.lval)
+		}
+
+		/* look through exception table */
+		xi := 0
+		for {
+			if ipExca[xi+0] == -1 && ipExca[xi+1] == ipstate {
+				break
+			}
+			xi += 2
+		}
+		for xi += 2; ; xi += 2 {
+			ipn = ipExca[xi+0]
+			if ipn < 0 || ipn == iptoken {
+				break
+			}
+		}
+		ipn = ipExca[xi+1]
+		if ipn < 0 {
+			goto ret0
+		}
+	}
+	if ipn == 0 {
+		/* error ... attempt to resume parsing */
+		switch Errflag {
+		case 0: /* brand new error */
+			iplex.Error(ipErrorMessage(ipstate, iptoken))
+			Nerrs++
+			if ipDebug >= 1 {
+				fmt.Printf("%s", ipStatname(ipstate))
+				fmt.Printf(" saw %s\n", ipTokname(iptoken))
+			}
+			fallthrough
+
+		case 1, 2: /* incompletely recovered error ... try again */
+			Errflag = 3
+
+			/* find a state where "error" is a legal shift action */
+			for ipp >= 0 {
+				ipn = ipPact[ipS[ipp].yys] + ipErrCode
+				if ipn >= 0 && ipn < ipLast {
+					ipstate = ipAct[ipn] /* simulate a shift of "error" */
+					if ipChk[ipstate] == ipErrCode {
+						goto ipstack
+					}
+				}
+
+				/* the current p has no shift on "error", pop stack */
+				if ipDebug >= 2 {
+					fmt.Printf("error recovery pops state %d\n", ipS[ipp].yys)
+				}
+				ipp--
+			}
+			/* there is no state on the stack with an error shift ... abort */
+			goto ret1
+
+		case 3: /* no shift yet; clobber input char */
+			if ipDebug >= 2 {
+				fmt.Printf("error recovery discards %s\n", ipTokname(iptoken))
+			}
+			if iptoken == ipEofCode {
+				goto ret1
+			}
+			iprcvr.char = -1
+			iptoken = -1
+			goto ipnewstate /* try again in the same state */
+		}
+	}
+
+	/* reduction by production ipn */
+	if ipDebug >= 2 {
+		fmt.Printf("reduce %v in:\n\t%v\n", ipn, ipStatname(ipstate))
+	}
+
+	ipnt := ipn
+	ippt := ipp
+	_ = ippt // guard against "declared and not used"
+
+	ipp -= ipR2[ipn]
+	// ipp is now the index of $0. Perform the default action. Iff the
+	// reduced production is ε, $1 is possibly out of range.
+	if ipp+1 >= len(ipS) {
+		nyys := make([]ipSymType, len(ipS)*2)
+		copy(nyys, ipS)
+		ipS = nyys
+	}
+	ipVAL = ipS[ipp+1]
+
+	/* consult goto table to find next state */
+	ipn = ipR1[ipn]
+	ipg := ipPgo[ipn]
+	ipj := ipg + ipS[ipp].yys + 1
+
+	if ipj >= ipLast {
+		ipstate = ipAct[ipg]
+	} else {
+		ipstate = ipAct[ipj]
+		if ipChk[ipstate] != -ipn {
+			ipstate = ipAct[ipg]
+		}
+	}
+	// dummy call; replaced with literal code
+	switch ipnt {
+
+	case 1:
+		ipDollar = ipS[ippt-1 : ippt+1]
+		{
+			ipVAL.result = append(ipVAL.result, ipDollar[1].addrRange)
+			iplex.(*ipLex).output = ipVAL.result
+		}
+	case 2:
+		ipDollar = ipS[ippt-3 : ippt+1]
+		{
+			ipVAL.result = append(ipDollar[1].result, ipDollar[3].addrRange)
+			iplex.(*ipLex).output = ipVAL.result
+		}
+	case 5:
+		ipDollar = ipS[ippt-3 : ippt+1]
+		{
+			mask := net.CIDRMask(int(ipDollar[3].num), 32)
+			min := ipDollar[1].addrRange.Min.Mask(mask)
+			maxInt := binary.BigEndian.Uint32([]byte(min)) +
+				0xffffffff -
+				binary.BigEndian.Uint32([]byte(mask))
+			maxBytes := make([]byte, 4)
+			binary.BigEndian.PutUint32(maxBytes, maxInt)
+			maxBytes = maxBytes[len(maxBytes)-4:]
+			max := net.IP(maxBytes)
+			ipVAL.addrRange = AddressRange{
+				Min: min.To4(),
+				Max: max.To4(),
+			}
+		}
+	case 6:
+		ipDollar = ipS[ippt-1 : ippt+1]
+		{
+			ipVAL.addrRange = ipDollar[1].addrRange
+		}
+	case 7:
+		ipDollar = ipS[ippt-7 : ippt+1]
+		{
+			ipVAL.addrRange = AddressRange{
+				Min: net.IPv4(ipDollar[1].octRange.min, ipDollar[3].octRange.min, ipDollar[5].octRange.min, ipDollar[7].octRange.min).To4(),
+				Max: net.IPv4(ipDollar[1].octRange.max, ipDollar[3].octRange.max, ipDollar[5].octRange.max, ipDollar[7].octRange.max).To4(),
+			}
+		}
+	case 8:
+		ipDollar = ipS[ippt-1 : ippt+1]
+		{
+			ipVAL.octRange = octetRange{ipDollar[1].num, ipDollar[1].num}
+		}
+	case 9:
+		// nolint
+		ipDollar = ipS[ippt-1 : ippt+1]
+		{
+			ipVAL.octRange = octetRange{0, 255}
+		}
+	case 10:
+		ipDollar = ipS[ippt-1 : ippt+1]
+		{
+			ipVAL.octRange = ipDollar[1].octRange
+		}
+	case 11:
+		ipDollar = ipS[ippt-3 : ippt+1]
+		{
+			ipVAL.octRange = octetRange{ipDollar[1].num, ipDollar[3].num}
+		}
+	}
+	goto ipstack /* stack new state and value */
+}