net: make spuriousENOTAVAIL to be able to parse EADDRNOTAVAIL correctly

Change-Id: I82e3aadbd18fccb98a76d1c36876510f5e1c3089
Reviewed-on: https://go-review.googlesource.com/12750Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/error_posix_test.go

@@ -6,7 +6,11 @@
 
 package net
 
-import "syscall"
+import (
+	"os"
+	"syscall"
+	"testing"
+)
 
 var (
 	errTimedout       = syscall.ETIMEDOUT
@@ -17,3 +21,24 @@ func isPlatformError(err error) bool {
 	_, ok := err.(syscall.Errno)
 	return ok
 }
+
+func TestSpuriousENOTAVAIL(t *testing.T) {
+	for _, tt := range []struct {
+		error
+		ok bool
+	}{
+		{syscall.EADDRNOTAVAIL, true},
+		{&os.SyscallError{Syscall: "syscall", Err: syscall.EADDRNOTAVAIL}, true},
+		{&OpError{Op: "op", Err: syscall.EADDRNOTAVAIL}, true},
+		{&OpError{Op: "op", Err: &os.SyscallError{Syscall: "syscall", Err: syscall.EADDRNOTAVAIL}}, true},
+
+		{syscall.EINVAL, false},
+		{&os.SyscallError{Syscall: "syscall", Err: syscall.EINVAL}, false},
+		{&OpError{Op: "op", Err: syscall.EINVAL}, false},
+		{&OpError{Op: "op", Err: &os.SyscallError{Syscall: "syscall", Err: syscall.EINVAL}}, false},
+	} {
+		if ok := spuriousENOTAVAIL(tt.error); ok != tt.ok {
+			t.Errorf("spuriousENOTAVAIL(%v) = %v; want %v", tt.error, ok, tt.ok)
+		}
+	}
+}

src/net/tcpsock_posix.go

@@ -230,8 +230,13 @@ func selfConnect(fd *netFD, err error) bool {
 }
 
 func spuriousENOTAVAIL(err error) bool {
-	e, ok := err.(*OpError)
-	return ok && e.Err == syscall.EADDRNOTAVAIL
+	if op, ok := err.(*OpError); ok {
+		err = op.Err
+	}
+	if sys, ok := err.(*os.SyscallError); ok {
+		err = sys.Err
+	}
+	return err == syscall.EADDRNOTAVAIL
 }
 
 // TCPListener is a TCP network listener.  Clients should typically