net: make all Resolver methods respect Resolver.PreferGo

Fixes #17532

Change-Id: Id62671d505c77ea924b3570a504cdc3b157e5a0d
Reviewed-on: https://go-review.googlesource.com/31734
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/lookup.go

@@ -101,13 +101,6 @@ type Resolver struct {
 	// TODO(bradfitz): Timeout time.Duration?
 }
 
-func (r *Resolver) lookupIPFunc() func(context.Context, string) ([]IPAddr, error) {
-	if r != nil && r.PreferGo {
-		return goLookupIP
-	}
-	return lookupIP
-}
-
 // LookupHost looks up the given host using the local resolver.
 // It returns a slice of that host's addresses.
 func LookupHost(host string) (addrs []string, err error) {
@@ -125,7 +118,7 @@ func (r *Resolver) LookupHost(ctx context.Context, host string) (addrs []string,
 	if ip := ParseIP(host); ip != nil {
 		return []string{host}, nil
 	}
-	return lookupHost(ctx, host)
+	return r.lookupHost(ctx, host)
 }
 
 // LookupIP looks up host using the local resolver.
@@ -160,7 +153,7 @@ func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, err
 	// The underlying resolver func is lookupIP by default but it
 	// can be overridden by tests. This is needed by net/http, so it
 	// uses a context key instead of unexported variables.
-	resolverFunc := r.lookupIPFunc()
+	resolverFunc := r.lookupIP
 	if alt, _ := ctx.Value(nettrace.LookupIPAltResolverKey{}).(func(context.Context, string) ([]IPAddr, error)); alt != nil {
 		resolverFunc = alt
 	}
@@ -229,7 +222,7 @@ func LookupPort(network, service string) (port int, err error) {
 func (r *Resolver) LookupPort(ctx context.Context, network, service string) (port int, err error) {
 	port, needsLookup := parsePort(service)
 	if needsLookup {
-		port, err = lookupPort(ctx, network, service)
+		port, err = r.lookupPort(ctx, network, service)
 		if err != nil {
 			return 0, err
 		}
@@ -245,7 +238,7 @@ func (r *Resolver) LookupPort(ctx context.Context, network, service string) (por
 // LookupHost or LookupIP directly; both take care of resolving
 // the canonical name as part of the lookup.
 func LookupCNAME(name string) (cname string, err error) {
-	return lookupCNAME(context.Background(), name)
+	return DefaultResolver.lookupCNAME(context.Background(), name)
 }
 
 // LookupCNAME returns the canonical DNS host for the given name.
@@ -253,7 +246,7 @@ func LookupCNAME(name string) (cname string, err error) {
 // LookupHost or LookupIP directly; both take care of resolving
 // the canonical name as part of the lookup.
 func (r *Resolver) LookupCNAME(ctx context.Context, name string) (cname string, err error) {
-	return lookupCNAME(ctx, name)
+	return r.lookupCNAME(ctx, name)
 }
 
 // LookupSRV tries to resolve an SRV query of the given service,
@@ -266,7 +259,7 @@ func (r *Resolver) LookupCNAME(ctx context.Context, name string) (cname string,
 // publishing SRV records under non-standard names, if both service
 // and proto are empty strings, LookupSRV looks up name directly.
 func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
-	return lookupSRV(context.Background(), service, proto, name)
+	return DefaultResolver.lookupSRV(context.Background(), service, proto, name)
 }
 
 // LookupSRV tries to resolve an SRV query of the given service,
@@ -279,47 +272,47 @@ func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err err
 // publishing SRV records under non-standard names, if both service
 // and proto are empty strings, LookupSRV looks up name directly.
 func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
-	return lookupSRV(ctx, service, proto, name)
+	return r.lookupSRV(ctx, service, proto, name)
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
 func LookupMX(name string) ([]*MX, error) {
-	return lookupMX(context.Background(), name)
+	return DefaultResolver.lookupMX(context.Background(), name)
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
 func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error) {
-	return lookupMX(ctx, name)
+	return r.lookupMX(ctx, name)
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
 func LookupNS(name string) ([]*NS, error) {
-	return lookupNS(context.Background(), name)
+	return DefaultResolver.lookupNS(context.Background(), name)
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
 func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error) {
-	return lookupNS(ctx, name)
+	return r.lookupNS(ctx, name)
 }
 
 // LookupTXT returns the DNS TXT records for the given domain name.
 func LookupTXT(name string) ([]string, error) {
-	return lookupTXT(context.Background(), name)
+	return DefaultResolver.lookupTXT(context.Background(), name)
 }
 
 // LookupTXT returns the DNS TXT records for the given domain name.
 func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error) {
-	return lookupTXT(ctx, name)
+	return r.lookupTXT(ctx, name)
 }
 
 // LookupAddr performs a reverse lookup for the given address, returning a list
 // of names mapping to that address.
 func LookupAddr(addr string) (names []string, err error) {
-	return lookupAddr(context.Background(), addr)
+	return DefaultResolver.lookupAddr(context.Background(), addr)
 }
 
 // LookupAddr performs a reverse lookup for the given address, returning a list
 // of names mapping to that address.
 func (r *Resolver) LookupAddr(ctx context.Context, addr string) (names []string, err error) {
-	return lookupAddr(ctx, addr)
+	return r.lookupAddr(ctx, addr)
 }

src/net/lookup_nacl.go

@@ -15,42 +15,38 @@ func lookupProtocol(ctx context.Context, name string) (proto int, err error) {
 	return lookupProtocolMap(name)
 }
 
-func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
+func (*Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
 	return nil, syscall.ENOPROTOOPT
 }
 
-func goLookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
+func (*Resolver) lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
 	return nil, syscall.ENOPROTOOPT
 }
 
-func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
-	return nil, syscall.ENOPROTOOPT
-}
-
-func lookupPort(ctx context.Context, network, service string) (port int, err error) {
+func (*Resolver) lookupPort(ctx context.Context, network, service string) (port int, err error) {
 	return goLookupPort(network, service)
 }
 
-func lookupCNAME(ctx context.Context, name string) (cname string, err error) {
+func (*Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) {
 	return "", syscall.ENOPROTOOPT
 }
 
-func lookupSRV(ctx context.Context, service, proto, name string) (cname string, srvs []*SRV, err error) {
+func (*Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, srvs []*SRV, err error) {
 	return "", nil, syscall.ENOPROTOOPT
 }
 
-func lookupMX(ctx context.Context, name string) (mxs []*MX, err error) {
+func (*Resolver) lookupMX(ctx context.Context, name string) (mxs []*MX, err error) {
 	return nil, syscall.ENOPROTOOPT
 }
 
-func lookupNS(ctx context.Context, name string) (nss []*NS, err error) {
+func (*Resolver) lookupNS(ctx context.Context, name string) (nss []*NS, err error) {
 	return nil, syscall.ENOPROTOOPT
 }
 
-func lookupTXT(ctx context.Context, name string) (txts []string, err error) {
+func (*Resolver) lookupTXT(ctx context.Context, name string) (txts []string, err error) {
 	return nil, syscall.ENOPROTOOPT
 }
 
-func lookupAddr(ctx context.Context, addr string) (ptrs []string, err error) {
+func (*Resolver) lookupAddr(ctx context.Context, addr string) (ptrs []string, err error) {
 	return nil, syscall.ENOPROTOOPT
 }

src/net/lookup_plan9.go

@@ -117,7 +117,7 @@ func lookupProtocol(ctx context.Context, name string) (proto int, err error) {
 	return 0, UnknownNetworkError(name)
 }
 
-func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
+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")
@@ -148,10 +148,8 @@ loop:
 	return
 }
 
-var goLookupIP = lookupIP
-
-func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
-	lits, err := lookupHost(ctx, host)
+func (r *Resolver) lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
+	lits, err := r.lookupHost(ctx, host)
 	if err != nil {
 		return
 	}
@@ -165,7 +163,7 @@ func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
 	return
 }
 
-func lookupPort(ctx context.Context, network, service string) (port int, err error) {
+func (*Resolver) lookupPort(ctx context.Context, network, service string) (port int, err error) {
 	switch network {
 	case "tcp4", "tcp6":
 		network = "tcp"
@@ -194,7 +192,7 @@ func lookupPort(ctx context.Context, network, service string) (port int, err err
 	return 0, unknownPortError
 }
 
-func lookupCNAME(ctx context.Context, name string) (cname string, err error) {
+func (*Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) {
 	lines, err := queryDNS(ctx, name, "cname")
 	if err != nil {
 		return
@@ -207,7 +205,7 @@ func lookupCNAME(ctx context.Context, name string) (cname string, err error) {
 	return "", errors.New("bad response from ndb/dns")
 }
 
-func lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
+func (*Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
 	var target string
 	if service == "" && proto == "" {
 		target = name
@@ -236,7 +234,7 @@ func lookupSRV(ctx context.Context, service, proto, name string) (cname string,
 	return
 }
 
-func lookupMX(ctx context.Context, name string) (mx []*MX, err error) {
+func (*Resolver) lookupMX(ctx context.Context, name string) (mx []*MX, err error) {
 	lines, err := queryDNS(ctx, name, "mx")
 	if err != nil {
 		return
@@ -254,7 +252,7 @@ func lookupMX(ctx context.Context, name string) (mx []*MX, err error) {
 	return
 }
 
-func lookupNS(ctx context.Context, name string) (ns []*NS, err error) {
+func (*Resolver) lookupNS(ctx context.Context, name string) (ns []*NS, err error) {
 	lines, err := queryDNS(ctx, name, "ns")
 	if err != nil {
 		return
@@ -269,7 +267,7 @@ func lookupNS(ctx context.Context, name string) (ns []*NS, err error) {
 	return
 }
 
-func lookupTXT(ctx context.Context, name string) (txt []string, err error) {
+func (*Resolver) lookupTXT(ctx context.Context, name string) (txt []string, err error) {
 	lines, err := queryDNS(ctx, name, "txt")
 	if err != nil {
 		return
@@ -282,7 +280,7 @@ func lookupTXT(ctx context.Context, name string) (txt []string, err error) {
 	return
 }
 
-func lookupAddr(ctx context.Context, addr string) (name []string, err error) {
+func (*Resolver) lookupAddr(ctx context.Context, addr string) (name []string, err error) {
 	arpa, err := reverseaddr(addr)
 	if err != nil {
 		return

src/net/lookup_unix.go

@@ -48,9 +48,9 @@ func lookupProtocol(_ context.Context, name string) (int, error) {
 	return lookupProtocolMap(name)
 }
 
-func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
+func (r *Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
 	order := systemConf().hostLookupOrder(host)
-	if order == hostLookupCgo {
+	if !r.PreferGo && order == hostLookupCgo {
 		if addrs, err, ok := cgoLookupHost(ctx, host); ok {
 			return addrs, err
 		}
@@ -60,7 +60,10 @@ func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
 	return goLookupHostOrder(ctx, host, order)
 }
 
-func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
+func (r *Resolver) lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
+	if r.PreferGo {
+		return goLookupIP(ctx, host)
+	}
 	order := systemConf().hostLookupOrder(host)
 	if order == hostLookupCgo {
 		if addrs, err, ok := cgoLookupIP(ctx, host); ok {
@@ -72,13 +75,13 @@ func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
 	return goLookupIPOrder(ctx, host, order)
 }
 
-func lookupPort(ctx context.Context, network, service string) (int, error) {
+func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
 	// TODO: use the context if there ever becomes a need. Related
 	// is issue 15321. But port lookup generally just involves
 	// local files, and the os package has no context support. The
 	// files might be on a remote filesystem, though. This should
 	// probably race goroutines if ctx != context.Background().
-	if systemConf().canUseCgo() {
+	if !r.PreferGo && systemConf().canUseCgo() {
 		if port, err, ok := cgoLookupPort(ctx, network, service); ok {
 			return port, err
 		}
@@ -86,8 +89,8 @@ func lookupPort(ctx context.Context, network, service string) (int, error) {
 	return goLookupPort(network, service)
 }
 
-func lookupCNAME(ctx context.Context, name string) (string, error) {
-	if systemConf().canUseCgo() {
+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
 		}
@@ -95,7 +98,7 @@ func lookupCNAME(ctx context.Context, name string) (string, error) {
 	return goLookupCNAME(ctx, name)
 }
 
-func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
+func (*Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
 	var target string
 	if service == "" && proto == "" {
 		target = name
@@ -115,7 +118,7 @@ func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV
 	return cname, srvs, nil
 }
 
-func lookupMX(ctx context.Context, name string) ([]*MX, error) {
+func (*Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
 	_, rrs, err := lookup(ctx, name, dnsTypeMX)
 	if err != nil {
 		return nil, err
@@ -129,7 +132,7 @@ func lookupMX(ctx context.Context, name string) ([]*MX, error) {
 	return mxs, nil
 }
 
-func lookupNS(ctx context.Context, name string) ([]*NS, error) {
+func (*Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
 	_, rrs, err := lookup(ctx, name, dnsTypeNS)
 	if err != nil {
 		return nil, err
@@ -141,7 +144,7 @@ func lookupNS(ctx context.Context, name string) ([]*NS, error) {
 	return nss, nil
 }
 
-func lookupTXT(ctx context.Context, name string) ([]string, error) {
+func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
 	_, rrs, err := lookup(ctx, name, dnsTypeTXT)
 	if err != nil {
 		return nil, err
@@ -153,8 +156,8 @@ func lookupTXT(ctx context.Context, name string) ([]string, error) {
 	return txts, nil
 }
 
-func lookupAddr(ctx context.Context, addr string) ([]string, error) {
-	if systemConf().canUseCgo() {
+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
 		}

src/net/lookup_windows.go

@@ -54,8 +54,8 @@ func lookupProtocol(ctx context.Context, name string) (int, error) {
 	}
 }
 
-func lookupHost(ctx context.Context, name string) ([]string, error) {
-	ips, err := lookupIP(ctx, name)
+func (r *Resolver) lookupHost(ctx context.Context, name string) ([]string, error) {
+	ips, err := r.lookupIP(ctx, name)
 	if err != nil {
 		return nil, err
 	}
@@ -66,13 +66,7 @@ func lookupHost(ctx context.Context, name string) ([]string, error) {
 	return addrs, nil
 }
 
-// goLookupIP isn't a Pure Go implementation on Windows.
-// TODO(bradfitz): should it be? Not sure it can be. It's always used syscall.GetAddrInfoW.
-func goLookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
-	return lookupIP(ctx, host)
-}
-
-func lookupIP(ctx context.Context, name string) ([]IPAddr, error) {
+func (r *Resolver) lookupIP(ctx context.Context, name string) ([]IPAddr, error) {
 	// TODO(bradfitz,brainman): use ctx more. See TODO below.
 
 	type ret struct {
@@ -131,7 +125,11 @@ func lookupIP(ctx context.Context, name string) ([]IPAddr, error) {
 	}
 }
 
-func lookupPort(ctx context.Context, network, service string) (int, error) {
+func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
+	if r.PreferGo {
+		return lookupPortMap(network, service)
+	}
+
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -171,7 +169,7 @@ func lookupPort(ctx context.Context, network, service string) (int, error) {
 	return 0, &DNSError{Err: syscall.EINVAL.Error(), Name: network + "/" + service}
 }
 
-func lookupCNAME(ctx context.Context, name string) (string, error) {
+func (*Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -192,7 +190,7 @@ func lookupCNAME(ctx context.Context, name string) (string, error) {
 	return absDomainName([]byte(cname)), nil
 }
 
-func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
+func (*Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -218,7 +216,7 @@ func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV
 	return absDomainName([]byte(target)), srvs, nil
 }
 
-func lookupMX(ctx context.Context, name string) ([]*MX, error) {
+func (*Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -238,7 +236,7 @@ func lookupMX(ctx context.Context, name string) ([]*MX, error) {
 	return mxs, nil
 }
 
-func lookupNS(ctx context.Context, name string) ([]*NS, error) {
+func (*Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -257,7 +255,7 @@ func lookupNS(ctx context.Context, name string) ([]*NS, error) {
 	return nss, nil
 }
 
-func lookupTXT(ctx context.Context, name string) ([]string, error) {
+func (*Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()
@@ -279,7 +277,7 @@ func lookupTXT(ctx context.Context, name string) ([]string, error) {
 	return txts, nil
 }
 
-func lookupAddr(ctx context.Context, addr string) ([]string, error) {
+func (*Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
 	// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
 	acquireThread()
 	defer releaseThread()