net: fix resolving local windows machine ptr

Fixes #29600

Change-Id: Ie60b5c8f8356dfc16b3ef6d3cee520b9ce6a61aa
GitHub-Last-Rev: 76cbdb96a69fb48a2c65966174e53e5aa68ce13d
GitHub-Pull-Request: golang/go#32214
Reviewed-on: https://go-review.googlesource.com/c/go/+/178701
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

diff --git a/src/net/lookup_windows.go b/src/net/lookup_windows.go
index d7b28f5e18571ff0a436112afdda13d0556536d4..adf1e368e1eb5a7bc5d955aac209bfb996827c88 100644 (file)
--- a/src/net/lookup_windows.go
+++ b/src/net/lookup_windows.go
@@ -358,7 +358,8 @@ func validRecs(r *syscall.DNSRecord, dnstype uint16, name string) []*syscall.DNS
        }
        rec := make([]*syscall.DNSRecord, 0, 10)
        for p := r; p != nil; p = p.Next {
-               if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer {
+               // in case of a local machine, DNS records are returned with DNSREC_QUESTION flag instead of DNS_ANSWER
+               if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer && p.Dw&dnsSectionMask != syscall.DnsSectionQuestion {
                        continue
                }
                if p.Type != dnstype {

diff --git a/src/net/lookup_windows_test.go b/src/net/lookup_windows_test.go
index d3748f28c3f98b59517a3fe9b0ce792e6ff3511b..62b61ed6c2f3ce9ed43a0bff92358be6a731db34 100644 (file)
--- a/src/net/lookup_windows_test.go
+++ b/src/net/lookup_windows_test.go
@@ -8,6 +8,7 @@ import (
        "bytes"
        "encoding/json"
        "errors"
+       "fmt"
        "internal/testenv"
        "os/exec"
        "reflect"
@@ -18,6 +19,7 @@ import (
 )
 
 var nslookupTestServers = []string{"mail.golang.com", "gmail.com"}
+var lookupTestIPs = []string{"8.8.8.8", "1.1.1.1"}
 
 func toJson(v interface{}) string {
        data, _ := json.Marshal(v)
@@ -124,6 +126,54 @@ func TestNSLookupTXT(t *testing.T) {
        }
 }
 
+func TestLookupLocalPTR(t *testing.T) {
+       testenv.MustHaveExternalNetwork(t)
+
+       addr, err := localIP()
+       if err != nil {
+               t.Errorf("failed to get local ip: %s", err)
+       }
+       names, err := LookupAddr(addr.String())
+       if err != nil {
+               t.Errorf("failed %s: %s", addr, err)
+       }
+       if len(names) == 0 {
+               t.Errorf("no results")
+       }
+       expected, err := lookupPTR(addr.String())
+       if err != nil {
+               t.Logf("skipping failed lookup %s test: %s", addr.String(), err)
+       }
+       sort.Strings(expected)
+       sort.Strings(names)
+       if !reflect.DeepEqual(expected, names) {
+               t.Errorf("different results %s:\texp:%v\tgot:%v", addr, toJson(expected), toJson(names))
+       }
+}
+
+func TestLookupPTR(t *testing.T) {
+       testenv.MustHaveExternalNetwork(t)
+
+       for _, addr := range lookupTestIPs {
+               names, err := LookupAddr(addr)
+               if err != nil {
+                       t.Errorf("failed %s: %s", addr, err)
+               }
+               if len(names) == 0 {
+                       t.Errorf("no results")
+               }
+               expected, err := lookupPTR(addr)
+               if err != nil {
+                       t.Logf("skipping failed lookup %s test: %s", addr, err)
+               }
+               sort.Strings(expected)
+               sort.Strings(names)
+               if !reflect.DeepEqual(expected, names) {
+                       t.Errorf("different results %s:\texp:%v\tgot:%v", addr, toJson(expected), toJson(names))
+               }
+       }
+}
+
 type byPrefAndHost []*MX
 
 func (s byPrefAndHost) Len() int { return len(s) }
@@ -230,3 +280,38 @@ func nslookupTXT(name string) (txt []string, err error) {
        }
        return
 }
+
+func ping(name string) (string, error) {
+       cmd := exec.Command("ping", "-n", "1", "-a", name)
+       stdoutStderr, err := cmd.CombinedOutput()
+       if err != nil {
+               return "", fmt.Errorf("%v: %v", err, string(stdoutStderr))
+       }
+       r := strings.ReplaceAll(string(stdoutStderr), "\r\n", "\n")
+       return r, nil
+}
+
+func lookupPTR(name string) (ptr []string, err error) {
+       var r string
+       if r, err = ping(name); err != nil {
+               return
+       }
+       ptr = make([]string, 0, 10)
+       rx := regexp.MustCompile(`(?m)^Pinging\s+([a-zA-Z0-9.\-]+)\s+\[.*$`)
+       for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+               ptr = append(ptr, ans[1]+".")
+       }
+       return
+}
+
+func localIP() (ip IP, err error) {
+       conn, err := Dial("udp", "golang.org:80")
+       if err != nil {
+               return nil, err
+       }
+       defer conn.Close()
+
+       localAddr := conn.LocalAddr().(*UDPAddr)
+
+       return localAddr.IP, nil
+}