1 files changed, 27 insertions, 14 deletions

diff --git a/libgo/go/net/dnsclient_unix.go b/libgo/go/net/dnsclient_unix.go
index c03c1b1..17188f0 100644
--- a/libgo/go/net/dnsclient_unix.go
+++ b/libgo/go/net/dnsclient_unix.go
@@ -20,14 +20,22 @@ import (
 	"io"
 	"math/rand"
 	"os"
-	"strconv"
 	"sync"
 	"time"
 )
 
+// A dnsDialer provides dialing suitable for DNS queries.
+type dnsDialer interface {
+	dialDNS(string, string) (dnsConn, error)
+}
+
+var testHookDNSDialer = func(d time.Duration) dnsDialer { return &Dialer{Timeout: d} }
+
 // A dnsConn represents a DNS transport endpoint.
 type dnsConn interface {
-	Conn
+	io.Closer
+
+	SetDeadline(time.Time) error
 
 	// readDNSResponse reads a DNS response message from the DNS
 	// transport endpoint and returns the received DNS response
@@ -122,7 +130,7 @@ func (d *Dialer) dialDNS(network, server string) (dnsConn, error) {
 
 // exchange sends a query on the connection and hopes for a response.
 func exchange(server, name string, qtype uint16, timeout time.Duration) (*dnsMsg, error) {
-	d := Dialer{Timeout: timeout}
+	d := testHookDNSDialer(timeout)
 	out := dnsMsg{
 		dnsMsgHdr: dnsMsgHdr{
 			recursion_desired: true,
@@ -165,9 +173,6 @@ func tryOneName(cfg *dnsConfig, name string, qtype uint16) (string, []dnsRR, err
 	if len(cfg.servers) == 0 {
 		return "", nil, &DNSError{Err: "no DNS servers", Name: name}
 	}
-	if len(name) >= 256 {
-		return "", nil, &DNSError{Err: "DNS name too long", Name: name}
-	}
 	timeout := time.Duration(cfg.timeout) * time.Second
 	var lastErr error
 	for i := 0; i < cfg.attempts; i++ {
@@ -186,7 +191,11 @@ func tryOneName(cfg *dnsConfig, name string, qtype uint16) (string, []dnsRR, err
 				continue
 			}
 			cname, rrs, err := answer(name, server, msg, qtype)
-			if err == nil || msg.rcode == dnsRcodeSuccess || msg.rcode == dnsRcodeNameError && msg.recursion_available {
+			// If answer errored for rcodes dnsRcodeSuccess or dnsRcodeNameError,
+			// it means the response in msg was not useful and trying another
+			// server probably won't help. Return now in those cases.
+			// TODO: indicate this in a more obvious way, such as a field on DNSError?
+			if err == nil || msg.rcode == dnsRcodeSuccess || msg.rcode == dnsRcodeNameError {
 				return cname, rrs, err
 			}
 			lastErr = err
@@ -374,7 +383,7 @@ func (o hostLookupOrder) String() string {
 	if s, ok := lookupOrderName[o]; ok {
 		return s
 	}
-	return "hostLookupOrder=" + strconv.Itoa(int(o)) + "??"
+	return "hostLookupOrder=" + itoa(int(o)) + "??"
 }
 
 // goLookupHost is the native Go implementation of LookupHost.
@@ -440,7 +449,8 @@ func goLookupIPOrder(name string, order hostLookupOrder) (addrs []IPAddr, err er
 	conf := resolvConf.dnsConfig
 	resolvConf.mu.RUnlock()
 	type racer struct {
-		rrs []dnsRR
+		fqdn string
+		rrs  []dnsRR
 		error
 	}
 	lane := make(chan racer, 1)
@@ -450,13 +460,16 @@ func goLookupIPOrder(name string, order hostLookupOrder) (addrs []IPAddr, err er
 		for _, qtype := range qtypes {
 			go func(qtype uint16) {
 				_, rrs, err := tryOneName(conf, fqdn, qtype)
-				lane <- racer{rrs, err}
+				lane <- racer{fqdn, rrs, err}
 			}(qtype)
 		}
 		for range qtypes {
 			racer := <-lane
 			if racer.error != nil {
-				lastErr = racer.error
+				// Prefer error for original name.
+				if lastErr == nil || racer.fqdn == name+"." {
+					lastErr = racer.error
+				}
 				continue
 			}
 			addrs = append(addrs, addrRecordList(racer.rrs)...)
@@ -473,12 +486,12 @@ func goLookupIPOrder(name string, order hostLookupOrder) (addrs []IPAddr, err er
 	}
 	sortByRFC6724(addrs)
 	if len(addrs) == 0 {
-		if lastErr != nil {
-			return nil, lastErr
-		}
 		if order == hostLookupDNSFiles {
 			addrs = goLookupIPFiles(name)
 		}
+		if len(addrs) == 0 && lastErr != nil {
+			return nil, lastErr
+		}
 	}
 	return addrs, nil
 }