1 files changed, 384 insertions, 0 deletions
diff --git a/src/net/lookup_plan9.go b/src/net/lookup_plan9.go
new file mode 100644
index 0000000..1995742
--- /dev/null
+++ b/src/net/lookup_plan9.go
@@ -0,0 +1,384 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"context"
+	"errors"
+	"internal/bytealg"
+	"internal/itoa"
+	"io"
+	"os"
+)
+
+func query(ctx context.Context, filename, query string, bufSize int) (addrs []string, err error) {
+	queryAddrs := func() (addrs []string, err error) {
+		file, err := os.OpenFile(filename, os.O_RDWR, 0)
+		if err != nil {
+			return nil, err
+		}
+		defer file.Close()
+
+		_, err = file.Seek(0, io.SeekStart)
+		if err != nil {
+			return nil, err
+		}
+		_, err = file.WriteString(query)
+		if err != nil {
+			return nil, err
+		}
+		_, err = file.Seek(0, io.SeekStart)
+		if err != nil {
+			return nil, err
+		}
+		buf := make([]byte, bufSize)
+		for {
+			n, _ := file.Read(buf)
+			if n <= 0 {
+				break
+			}
+			addrs = append(addrs, string(buf[:n]))
+		}
+		return addrs, nil
+	}
+
+	type ret struct {
+		addrs []string
+		err   error
+	}
+
+	ch := make(chan ret, 1)
+	go func() {
+		addrs, err := queryAddrs()
+		ch <- ret{addrs: addrs, err: err}
+	}()
+
+	select {
+	case r := <-ch:
+		return r.addrs, r.err
+	case <-ctx.Done():
+		return nil, &DNSError{
+			Name:      query,
+			Err:       ctx.Err().Error(),
+			IsTimeout: ctx.Err() == context.DeadlineExceeded,
+		}
+	}
+}
+
+func queryCS(ctx context.Context, net, host, service string) (res []string, err error) {
+	switch net {
+	case "tcp4", "tcp6":
+		net = "tcp"
+	case "udp4", "udp6":
+		net = "udp"
+	}
+	if host == "" {
+		host = "*"
+	}
+	return query(ctx, netdir+"/cs", net+"!"+host+"!"+service, 128)
+}
+
+func queryCS1(ctx context.Context, net string, ip IP, port int) (clone, dest string, err error) {
+	ips := "*"
+	if len(ip) != 0 && !ip.IsUnspecified() {
+		ips = ip.String()
+	}
+	lines, err := queryCS(ctx, net, ips, itoa.Itoa(port))
+	if err != nil {
+		return
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return "", "", errors.New("bad response from ndb/cs")
+	}
+	clone, dest = f[0], f[1]
+	return
+}
+
+func queryDNS(ctx context.Context, addr string, typ string) (res []string, err error) {
+	return query(ctx, netdir+"/dns", addr+" "+typ, 1024)
+}
+
+// toLower returns a lower-case version of in. Restricting us to
+// ASCII is sufficient to handle the IP protocol names and allow
+// us to not depend on the strings and unicode packages.
+func toLower(in string) string {
+	for _, c := range in {
+		if 'A' <= c && c <= 'Z' {
+			// Has upper case; need to fix.
+			out := []byte(in)
+			for i := 0; i < len(in); i++ {
+				c := in[i]
+				if 'A' <= c && c <= 'Z' {
+					c += 'a' - 'A'
+				}
+				out[i] = c
+			}
+			return string(out)
+		}
+	}
+	return in
+}
+
+// lookupProtocol looks up IP protocol name and returns
+// the corresponding protocol number.
+func lookupProtocol(ctx context.Context, name string) (proto int, err error) {
+	lines, err := query(ctx, netdir+"/cs", "!protocol="+toLower(name), 128)
+	if err != nil {
+		return 0, err
+	}
+	if len(lines) == 0 {
+		return 0, UnknownNetworkError(name)
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return 0, UnknownNetworkError(name)
+	}
+	s := f[1]
+	if n, _, ok := dtoi(s[bytealg.IndexByteString(s, '=')+1:]); ok {
+		return n, nil
+	}
+	return 0, UnknownNetworkError(name)
+}
+
+func (*Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
+	// Use netdir/cs instead of netdir/dns because cs knows about
+	// host names in local network (e.g. from /lib/ndb/local)
+	lines, err := queryCS(ctx, "net", host, "1")
+	if err != nil {
+		dnsError := &DNSError{Err: err.Error(), Name: host}
+		if stringsHasSuffix(err.Error(), "dns failure") {
+			dnsError.Err = errNoSuchHost.Error()
+			dnsError.IsNotFound = true
+		}
+		return nil, dnsError
+	}
+loop:
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		addr := f[1]
+		if i := bytealg.IndexByteString(addr, '!'); i >= 0 {
+			addr = addr[:i] // remove port
+		}
+		if ParseIP(addr) == nil {
+			continue
+		}
+		// only return unique addresses
+		for _, a := range addrs {
+			if a == addr {
+				continue loop
+			}
+		}
+		addrs = append(addrs, addr)
+	}
+	return
+}
+
+// preferGoOverPlan9 reports whether the resolver should use the
+// "PreferGo" implementation rather than asking plan9 services
+// for the answers.
+func (r *Resolver) preferGoOverPlan9() bool {
+	_, _, res := r.preferGoOverPlan9WithOrderAndConf()
+	return res
+}
+
+func (r *Resolver) preferGoOverPlan9WithOrderAndConf() (hostLookupOrder, *dnsConfig, bool) {
+	order, conf := systemConf().hostLookupOrder(r, "") // name is unused
+
+	// TODO(bradfitz): for now we only permit use of the PreferGo
+	// implementation when there's a non-nil Resolver with a
+	// non-nil Dialer. This is a sign that they the code is trying
+	// to use their DNS-speaking net.Conn (such as an in-memory
+	// DNS cache) and they don't want to actually hit the network.
+	// Once we add support for looking the default DNS servers
+	// from plan9, though, then we can relax this.
+	return order, conf, order != hostLookupCgo && r != nil && r.Dial != nil
+}
+
+func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) {
+	if r.preferGoOverPlan9() {
+		return r.goLookupIP(ctx, network, host)
+	}
+	lits, err := r.lookupHost(ctx, host)
+	if err != nil {
+		return
+	}
+	for _, lit := range lits {
+		host, zone := splitHostZone(lit)
+		if ip := ParseIP(host); ip != nil {
+			addr := IPAddr{IP: ip, Zone: zone}
+			addrs = append(addrs, addr)
+		}
+	}
+	return
+}
+
+func (*Resolver) lookupPort(ctx context.Context, network, service string) (port int, err error) {
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp"
+	case "udp4", "udp6":
+		network = "udp"
+	}
+	lines, err := queryCS(ctx, network, "127.0.0.1", toLower(service))
+	if err != nil {
+		return
+	}
+	unknownPortError := &AddrError{Err: "unknown port", Addr: network + "/" + service}
+	if len(lines) == 0 {
+		return 0, unknownPortError
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return 0, unknownPortError
+	}
+	s := f[1]
+	if i := bytealg.IndexByteString(s, '!'); i >= 0 {
+		s = s[i+1:] // remove address
+	}
+	if n, _, ok := dtoi(s); ok {
+		return n, nil
+	}
+	return 0, unknownPortError
+}
+
+func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) {
+	if order, conf, preferGo := r.preferGoOverPlan9WithOrderAndConf(); preferGo {
+		return r.goLookupCNAME(ctx, name, order, conf)
+	}
+
+	lines, err := queryDNS(ctx, name, "cname")
+	if err != nil {
+		if stringsHasSuffix(err.Error(), "dns failure") || stringsHasSuffix(err.Error(), "resource does not exist; negrcode 0") {
+			cname = name + "."
+			err = nil
+		}
+		return
+	}
+	if len(lines) > 0 {
+		if f := getFields(lines[0]); len(f) >= 3 {
+			return f[2] + ".", nil
+		}
+	}
+	return "", errors.New("bad response from ndb/dns")
+}
+
+func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
+	if r.preferGoOverPlan9() {
+		return r.goLookupSRV(ctx, service, proto, name)
+	}
+	var target string
+	if service == "" && proto == "" {
+		target = name
+	} else {
+		target = "_" + service + "._" + proto + "." + name
+	}
+	lines, err := queryDNS(ctx, target, "srv")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 6 {
+			continue
+		}
+		port, _, portOk := dtoi(f[4])
+		priority, _, priorityOk := dtoi(f[3])
+		weight, _, weightOk := dtoi(f[2])
+		if !(portOk && priorityOk && weightOk) {
+			continue
+		}
+		addrs = append(addrs, &SRV{absDomainName(f[5]), uint16(port), uint16(priority), uint16(weight)})
+		cname = absDomainName(f[0])
+	}
+	byPriorityWeight(addrs).sort()
+	return
+}
+
+func (r *Resolver) lookupMX(ctx context.Context, name string) (mx []*MX, err error) {
+	if r.preferGoOverPlan9() {
+		return r.goLookupMX(ctx, name)
+	}
+	lines, err := queryDNS(ctx, name, "mx")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 4 {
+			continue
+		}
+		if pref, _, ok := dtoi(f[2]); ok {
+			mx = append(mx, &MX{absDomainName(f[3]), uint16(pref)})
+		}
+	}
+	byPref(mx).sort()
+	return
+}
+
+func (r *Resolver) lookupNS(ctx context.Context, name string) (ns []*NS, err error) {
+	if r.preferGoOverPlan9() {
+		return r.goLookupNS(ctx, name)
+	}
+	lines, err := queryDNS(ctx, name, "ns")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		ns = append(ns, &NS{absDomainName(f[2])})
+	}
+	return
+}
+
+func (r *Resolver) lookupTXT(ctx context.Context, name string) (txt []string, err error) {
+	if r.preferGoOverPlan9() {
+		return r.goLookupTXT(ctx, name)
+	}
+	lines, err := queryDNS(ctx, name, "txt")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		if i := bytealg.IndexByteString(line, '\t'); i >= 0 {
+			txt = append(txt, line[i+1:])
+		}
+	}
+	return
+}
+
+func (r *Resolver) lookupAddr(ctx context.Context, addr string) (name []string, err error) {
+	if _, conf, preferGo := r.preferGoOverPlan9WithOrderAndConf(); preferGo {
+		return r.goLookupPTR(ctx, addr, conf)
+	}
+	arpa, err := reverseaddr(addr)
+	if err != nil {
+		return
+	}
+	lines, err := queryDNS(ctx, arpa, "ptr")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		name = append(name, absDomainName(f[2]))
+	}
+	return
+}
+
+// concurrentThreadsLimit returns the number of threads we permit to
+// run concurrently doing DNS lookups.
+func concurrentThreadsLimit() int {
+	return 500
+}