Create unique lookup file in net for darwin, move libSystem bindings …

…for res_search into runtime package

Signed-off-by: grant <[email protected]>

src/net/lookup_darwin.go

@@ -0,0 +1,376 @@
+// 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.
+
+// +build darwin
+
+package net
+
+import (
+	"context"
+	"internal/bytealg"
+	"sync"
+	"syscall"
+
+	"internal/x/net/dns/dnsmessage"
+)
+
+var onceReadProtocols sync.Once
+
+// readProtocols loads contents of /etc/protocols into protocols map
+// for quick access.
+func readProtocols() {
+	file, err := open("/etc/protocols")
+	if err != nil {
+		return
+	}
+	defer file.close()
+
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		// tcp    6   TCP    # transmission control protocol
+		if i := bytealg.IndexByteString(line, '#'); i >= 0 {
+			line = line[0:i]
+		}
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		if proto, _, ok := dtoi(f[1]); ok {
+			if _, ok := protocols[f[0]]; !ok {
+				protocols[f[0]] = proto
+			}
+			for _, alias := range f[2:] {
+				if _, ok := protocols[alias]; !ok {
+					protocols[alias] = proto
+				}
+			}
+		}
+	}
+}
+
+// lookupProtocol looks up IP protocol name in /etc/protocols and
+// returns correspondent protocol number.
+func lookupProtocol(_ context.Context, name string) (int, error) {
+	onceReadProtocols.Do(readProtocols)
+	return lookupProtocolMap(name)
+}
+
+func (r *Resolver) dial(ctx context.Context, network, server string) (Conn, error) {
+	// Calling Dial here is scary -- we have to be sure not to
+	// dial a name that will require a DNS lookup, or Dial will
+	// call back here to translate it. The DNS config parser has
+	// already checked that all the cfg.servers are IP
+	// addresses, which Dial will use without a DNS lookup.
+	var c Conn
+	var err error
+	if r != nil && r.Dial != nil {
+		c, err = r.Dial(ctx, network, server)
+	} else {
+		var d Dialer
+		c, err = d.DialContext(ctx, network, server)
+	}
+	if err != nil {
+		return nil, mapErr(err)
+	}
+	return c, nil
+}
+
+func (r *Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
+	order := systemConf().hostLookupOrder(r, host)
+	if !r.preferGo() && order == hostLookupCgo {
+		if addrs, err, ok := cgoLookupHost(ctx, host); ok {
+			return addrs, err
+		}
+		// cgo not available (or netgo); fall back to linked bindings
+		order = hostLookupFilesDNS
+	}
+
+	// darwin has unique resolution files, use libSystem binding if cgo is disabled.
+	addrs, err := resolverSearch(ctx, host, int32(dnsmessage.TypeALL), int32(dnsmessage.ClassINET))
+	if err == nil {
+		return addrs, nil
+	}
+	// something went wrong, fallback to Go's DNS resolver
+
+	return r.goLookupHostOrder(ctx, host, order)
+}
+
+func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) {
+	if r.preferGo() {
+		return r.goLookupIP(ctx, host)
+	}
+	order := systemConf().hostLookupOrder(r, host)
+	if order == hostLookupCgo {
+		if addrs, err, ok := cgoLookupIP(ctx, network, host); ok {
+			return addrs, err
+		}
+
+		// darwin has unique resolution files, use libSystem binding if cgo is disabled.
+		addrs, err := resolverSearch(ctx, host, int32(dnsmessage.TypeALL), int32(dnsmessage.ClassINET))
+		if err == nil {
+			return addrs, nil
+		}
+		// something went wrong, fallback to Go's DNS resolver
+
+		order = hostLookupFilesDNS
+	}
+	ips, _, err := r.goLookupIPCNAMEOrder(ctx, host, order)
+	return ips, err
+}
+
+func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
+	if !r.preferGo() && systemConf().canUseCgo() {
+		if port, err, ok := cgoLookupPort(ctx, network, service); ok {
+			if err != nil {
+				// Issue 18213: if cgo fails, first check to see whether we
+				// have the answer baked-in to the net package.
+				if port, err := goLookupPort(network, service); err == nil {
+					return port, nil
+				}
+			}
+			return port, err
+		}
+	}
+	return goLookupPort(network, service)
+}
+
+func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
+	if !r.preferGo() && systemConf().canUseCgo() {
+		if cname, err, ok := cgoLookupCNAME(ctx, name); ok {
+			return cname, err
+		}
+	}
+
+	// darwin has unique resolution files, use libSystem binding if cgo is not an option.
+	addrs, err := resolverSearch(ctx, name, int32(dnsmessage.TypeCNAME), int32(dnsmessage.ClassINET))
+	if err == nil {
+		return addrs, nil
+	}
+
+	// something went wrong, fallback to Go's DNS resolver
+	return r.goLookupCNAME(ctx, name)
+}
+
+func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
+	var target string
+	if service == "" && proto == "" {
+		target = name
+	} else {
+		target = "_" + service + "._" + proto + "." + name
+	}
+	p, server, err := r.lookup(ctx, target, dnsmessage.TypeSRV)
+	if err != nil {
+		return "", nil, err
+	}
+	var srvs []*SRV
+	var cname dnsmessage.Name
+	for {
+		h, err := p.AnswerHeader()
+		if err == dnsmessage.ErrSectionDone {
+			break
+		}
+		if err != nil {
+			return "", nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		if h.Type != dnsmessage.TypeSRV {
+			if err := p.SkipAnswer(); err != nil {
+				return "", nil, &DNSError{
+					Err:    "cannot unmarshal DNS message",
+					Name:   name,
+					Server: server,
+				}
+			}
+			continue
+		}
+		if cname.Length == 0 && h.Name.Length != 0 {
+			cname = h.Name
+		}
+		srv, err := p.SRVResource()
+		if err != nil {
+			return "", nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		srvs = append(srvs, &SRV{Target: srv.Target.String(), Port: srv.Port, Priority: srv.Priority, Weight: srv.Weight})
+	}
+	byPriorityWeight(srvs).sort()
+	return cname.String(), srvs, nil
+}
+
+func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
+	p, server, err := r.lookup(ctx, name, dnsmessage.TypeMX)
+	if err != nil {
+		return nil, err
+	}
+	var mxs []*MX
+	for {
+		h, err := p.AnswerHeader()
+		if err == dnsmessage.ErrSectionDone {
+			break
+		}
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		if h.Type != dnsmessage.TypeMX {
+			if err := p.SkipAnswer(); err != nil {
+				return nil, &DNSError{
+					Err:    "cannot unmarshal DNS message",
+					Name:   name,
+					Server: server,
+				}
+			}
+			continue
+		}
+		mx, err := p.MXResource()
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		mxs = append(mxs, &MX{Host: mx.MX.String(), Pref: mx.Pref})
+
+	}
+	byPref(mxs).sort()
+	return mxs, nil
+}
+
+func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
+	p, server, err := r.lookup(ctx, name, dnsmessage.TypeNS)
+	if err != nil {
+		return nil, err
+	}
+	var nss []*NS
+	for {
+		h, err := p.AnswerHeader()
+		if err == dnsmessage.ErrSectionDone {
+			break
+		}
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		if h.Type != dnsmessage.TypeNS {
+			if err := p.SkipAnswer(); err != nil {
+				return nil, &DNSError{
+					Err:    "cannot unmarshal DNS message",
+					Name:   name,
+					Server: server,
+				}
+			}
+			continue
+		}
+		ns, err := p.NSResource()
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		nss = append(nss, &NS{Host: ns.NS.String()})
+	}
+	return nss, nil
+}
+
+func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
+	p, server, err := r.lookup(ctx, name, dnsmessage.TypeTXT)
+	if err != nil {
+		return nil, err
+	}
+	var txts []string
+	for {
+		h, err := p.AnswerHeader()
+		if err == dnsmessage.ErrSectionDone {
+			break
+		}
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		if h.Type != dnsmessage.TypeTXT {
+			if err := p.SkipAnswer(); err != nil {
+				return nil, &DNSError{
+					Err:    "cannot unmarshal DNS message",
+					Name:   name,
+					Server: server,
+				}
+			}
+			continue
+		}
+		txt, err := p.TXTResource()
+		if err != nil {
+			return nil, &DNSError{
+				Err:    "cannot unmarshal DNS message",
+				Name:   name,
+				Server: server,
+			}
+		}
+		// Multiple strings in one TXT record need to be
+		// concatenated without separator to be consistent
+		// with previous Go resolver.
+		n := 0
+		for _, s := range txt.TXT {
+			n += len(s)
+		}
+		txtJoin := make([]byte, 0, n)
+		for _, s := range txt.TXT {
+			txtJoin = append(txtJoin, s...)
+		}
+		if len(txts) == 0 {
+			txts = make([]string, 0, 1)
+		}
+		txts = append(txts, string(txtJoin))
+	}
+	return txts, nil
+}
+
+func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
+	if !r.preferGo() && systemConf().canUseCgo() {
+		if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok {
+			return ptrs, err
+		}
+	}
+	return r.goLookupPTR(ctx, addr)
+}
+
+// concurrentThreadsLimit returns the number of threads we permit to
+// run concurrently doing DNS lookups via cgo. A DNS lookup may use a
+// file descriptor so we limit this to less than the number of
+// permitted open files. On some systems, notably Darwin, if
+// getaddrinfo is unable to open a file descriptor it simply returns
+// EAI_NONAME rather than a useful error. Limiting the number of
+// concurrent getaddrinfo calls to less than the permitted number of
+// file descriptors makes that error less likely. We don't bother to
+// apply the same limit to DNS lookups run directly from Go, because
+// there we will return a meaningful "too many open files" error.
+func concurrentThreadsLimit() int {
+	var rlim syscall.Rlimit
+	if err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rlim); err != nil {
+		return 500
+	}
+	r := int(rlim.Cur)
+	if r > 500 {
+		r = 500
+	} else if r > 30 {
+		r -= 30
+	}
+	return r
+}