1//+build ignore
2
3// types_generate.go is meant to run with go generate. It will use
4// go/{importer,types} to track down all the RR struct types. Then for each type
5// it will generate conversion tables (TypeToRR and TypeToString) and banal
6// methods (len, Header, copy) based on the struct tags. The generated source is
7// written to ztypes.go, and is meant to be checked into git.
8package main
9
10import (
11	"bytes"
12	"fmt"
13	"go/format"
14	"go/types"
15	"log"
16	"os"
17	"strings"
18	"text/template"
19
20	"golang.org/x/tools/go/packages"
21)
22
23var skipLen = map[string]struct{}{
24	"NSEC":  {},
25	"NSEC3": {},
26	"OPT":   {},
27	"CSYNC": {},
28}
29
30var packageHdr = `
31// Code generated by "go run types_generate.go"; DO NOT EDIT.
32
33package dns
34
35import (
36	"encoding/base64"
37	"net"
38)
39
40`
41
42var TypeToRR = template.Must(template.New("TypeToRR").Parse(`
43// TypeToRR is a map of constructors for each RR type.
44var TypeToRR = map[uint16]func() RR{
45{{range .}}{{if ne . "RFC3597"}}  Type{{.}}:  func() RR { return new({{.}}) },
46{{end}}{{end}}                    }
47
48`))
49
50var typeToString = template.Must(template.New("typeToString").Parse(`
51// TypeToString is a map of strings for each RR type.
52var TypeToString = map[uint16]string{
53{{range .}}{{if ne . "NSAPPTR"}}  Type{{.}}: "{{.}}",
54{{end}}{{end}}                    TypeNSAPPTR:    "NSAP-PTR",
55}
56
57`))
58
59var headerFunc = template.Must(template.New("headerFunc").Parse(`
60{{range .}}  func (rr *{{.}}) Header() *RR_Header { return &rr.Hdr }
61{{end}}
62
63`))
64
65// getTypeStruct will take a type and the package scope, and return the
66// (innermost) struct if the type is considered a RR type (currently defined as
67// those structs beginning with a RR_Header, could be redefined as implementing
68// the RR interface). The bool return value indicates if embedded structs were
69// resolved.
70func getTypeStruct(t types.Type, scope *types.Scope) (*types.Struct, bool) {
71	st, ok := t.Underlying().(*types.Struct)
72	if !ok {
73		return nil, false
74	}
75	if st.Field(0).Type() == scope.Lookup("RR_Header").Type() {
76		return st, false
77	}
78	if st.Field(0).Anonymous() {
79		st, _ := getTypeStruct(st.Field(0).Type(), scope)
80		return st, true
81	}
82	return nil, false
83}
84
85// loadModule retrieves package description for a given module.
86func loadModule(name string) (*types.Package, error) {
87	conf := packages.Config{Mode: packages.NeedTypes | packages.NeedTypesInfo}
88	pkgs, err := packages.Load(&conf, name)
89	if err != nil {
90		return nil, err
91	}
92	return pkgs[0].Types, nil
93}
94
95func main() {
96	// Import and type-check the package
97	pkg, err := loadModule("github.com/miekg/dns")
98	fatalIfErr(err)
99	scope := pkg.Scope()
100
101	// Collect constants like TypeX
102	var numberedTypes []string
103	for _, name := range scope.Names() {
104		o := scope.Lookup(name)
105		if o == nil || !o.Exported() {
106			continue
107		}
108		b, ok := o.Type().(*types.Basic)
109		if !ok || b.Kind() != types.Uint16 {
110			continue
111		}
112		if !strings.HasPrefix(o.Name(), "Type") {
113			continue
114		}
115		name := strings.TrimPrefix(o.Name(), "Type")
116		if name == "PrivateRR" {
117			continue
118		}
119		numberedTypes = append(numberedTypes, name)
120	}
121
122	// Collect actual types (*X)
123	var namedTypes []string
124	for _, name := range scope.Names() {
125		o := scope.Lookup(name)
126		if o == nil || !o.Exported() {
127			continue
128		}
129		if st, _ := getTypeStruct(o.Type(), scope); st == nil {
130			continue
131		}
132		if name == "PrivateRR" {
133			continue
134		}
135
136		// Check if corresponding TypeX exists
137		if scope.Lookup("Type"+o.Name()) == nil && o.Name() != "RFC3597" {
138			log.Fatalf("Constant Type%s does not exist.", o.Name())
139		}
140
141		namedTypes = append(namedTypes, o.Name())
142	}
143
144	b := &bytes.Buffer{}
145	b.WriteString(packageHdr)
146
147	// Generate TypeToRR
148	fatalIfErr(TypeToRR.Execute(b, namedTypes))
149
150	// Generate typeToString
151	fatalIfErr(typeToString.Execute(b, numberedTypes))
152
153	// Generate headerFunc
154	fatalIfErr(headerFunc.Execute(b, namedTypes))
155
156	// Generate len()
157	fmt.Fprint(b, "// len() functions\n")
158	for _, name := range namedTypes {
159		if _, ok := skipLen[name]; ok {
160			continue
161		}
162		o := scope.Lookup(name)
163		st, isEmbedded := getTypeStruct(o.Type(), scope)
164		if isEmbedded {
165			continue
166		}
167		fmt.Fprintf(b, "func (rr *%s) len(off int, compression map[string]struct{}) int {\n", name)
168		fmt.Fprintf(b, "l := rr.Hdr.len(off, compression)\n")
169		for i := 1; i < st.NumFields(); i++ {
170			o := func(s string) { fmt.Fprintf(b, s, st.Field(i).Name()) }
171
172			if _, ok := st.Field(i).Type().(*types.Slice); ok {
173				switch st.Tag(i) {
174				case `dns:"-"`:
175					// ignored
176				case `dns:"cdomain-name"`:
177					o("for _, x := range rr.%s { l += domainNameLen(x, off+l, compression, true) }\n")
178				case `dns:"domain-name"`:
179					o("for _, x := range rr.%s { l += domainNameLen(x, off+l, compression, false) }\n")
180				case `dns:"txt"`:
181					o("for _, x := range rr.%s { l += len(x) + 1 }\n")
182				case `dns:"apl"`:
183					o("for _, x := range rr.%s { l += x.len() }\n")
184				default:
185					log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
186				}
187				continue
188			}
189
190			switch {
191			case st.Tag(i) == `dns:"-"`:
192				// ignored
193			case st.Tag(i) == `dns:"cdomain-name"`:
194				o("l += domainNameLen(rr.%s, off+l, compression, true)\n")
195			case st.Tag(i) == `dns:"domain-name"`:
196				o("l += domainNameLen(rr.%s, off+l, compression, false)\n")
197			case st.Tag(i) == `dns:"octet"`:
198				o("l += len(rr.%s)\n")
199			case strings.HasPrefix(st.Tag(i), `dns:"size-base64`):
200				fallthrough
201			case st.Tag(i) == `dns:"base64"`:
202				o("l += base64.StdEncoding.DecodedLen(len(rr.%s))\n")
203			case strings.HasPrefix(st.Tag(i), `dns:"size-hex:`): // this has an extra field where the length is stored
204				o("l += len(rr.%s)/2\n")
205			case st.Tag(i) == `dns:"hex"`:
206				o("l += len(rr.%s)/2\n")
207			case st.Tag(i) == `dns:"any"`:
208				o("l += len(rr.%s)\n")
209			case st.Tag(i) == `dns:"a"`:
210				o("if len(rr.%s) != 0 { l += net.IPv4len }\n")
211			case st.Tag(i) == `dns:"aaaa"`:
212				o("if len(rr.%s) != 0 { l += net.IPv6len }\n")
213			case st.Tag(i) == `dns:"txt"`:
214				o("for _, t := range rr.%s { l += len(t) + 1 }\n")
215			case st.Tag(i) == `dns:"uint48"`:
216				o("l += 6 // %s\n")
217			case st.Tag(i) == "":
218				switch st.Field(i).Type().(*types.Basic).Kind() {
219				case types.Uint8:
220					o("l++ // %s\n")
221				case types.Uint16:
222					o("l += 2 // %s\n")
223				case types.Uint32:
224					o("l += 4 // %s\n")
225				case types.Uint64:
226					o("l += 8 // %s\n")
227				case types.String:
228					o("l += len(rr.%s) + 1\n")
229				default:
230					log.Fatalln(name, st.Field(i).Name())
231				}
232			default:
233				log.Fatalln(name, st.Field(i).Name(), st.Tag(i))
234			}
235		}
236		fmt.Fprintf(b, "return l }\n")
237	}
238
239	// Generate copy()
240	fmt.Fprint(b, "// copy() functions\n")
241	for _, name := range namedTypes {
242		o := scope.Lookup(name)
243		st, isEmbedded := getTypeStruct(o.Type(), scope)
244		if isEmbedded {
245			continue
246		}
247		fmt.Fprintf(b, "func (rr *%s) copy() RR {\n", name)
248		fields := []string{"rr.Hdr"}
249		for i := 1; i < st.NumFields(); i++ {
250			f := st.Field(i).Name()
251			if sl, ok := st.Field(i).Type().(*types.Slice); ok {
252				t := sl.Underlying().String()
253				t = strings.TrimPrefix(t, "[]")
254				if strings.Contains(t, ".") {
255					splits := strings.Split(t, ".")
256					t = splits[len(splits)-1]
257				}
258				// For the EDNS0 interface (used in the OPT RR), we need to call the copy method on each element.
259				if t == "EDNS0" {
260					fmt.Fprintf(b, "%s := make([]%s, len(rr.%s));\nfor i,e := range rr.%s {\n %s[i] = e.copy()\n}\n",
261						f, t, f, f, f)
262					fields = append(fields, f)
263					continue
264				}
265				if t == "APLPrefix" {
266					fmt.Fprintf(b, "%s := make([]%s, len(rr.%s));\nfor i := range rr.%s {\n %s[i] = rr.%s[i].copy()\n}\n",
267						f, t, f, f, f, f)
268					fields = append(fields, f)
269					continue
270				}
271				fmt.Fprintf(b, "%s := make([]%s, len(rr.%s)); copy(%s, rr.%s)\n",
272					f, t, f, f, f)
273				fields = append(fields, f)
274				continue
275			}
276			if st.Field(i).Type().String() == "net.IP" {
277				fields = append(fields, "copyIP(rr."+f+")")
278				continue
279			}
280			fields = append(fields, "rr."+f)
281		}
282		fmt.Fprintf(b, "return &%s{%s}\n", name, strings.Join(fields, ","))
283		fmt.Fprintf(b, "}\n")
284	}
285
286	// gofmt
287	res, err := format.Source(b.Bytes())
288	if err != nil {
289		b.WriteTo(os.Stderr)
290		log.Fatal(err)
291	}
292
293	// write result
294	f, err := os.Create("ztypes.go")
295	fatalIfErr(err)
296	defer f.Close()
297	f.Write(res)
298}
299
300func fatalIfErr(err error) {
301	if err != nil {
302		log.Fatal(err)
303	}
304}
305