fix(netxlite/errorsx): map "use of closed network connection" (#510)

Part of https://github.com/ooni/probe/issues/1733 and diff has been
extracted from https://github.com/ooni/probe-cli/pull/506.

internal/netxlite/errorsx/classify.go

@@ -90,6 +90,9 @@ func classifyWithStringSuffix(err error) string {
 		// that we return here is significantly more specific.
 		return FailureDNSNXDOMAINError
 	}
+	if strings.HasSuffix(s, "use of closed network connection") {
+		return FailureConnectionAlreadyClosed
+	}
 	return "" // not found
 }
 

internal/netxlite/errorsx/classify_test.go

@@ -77,6 +77,13 @@ func TestClassifyGenericError(t *testing.T) {
 		}
 	})
 
+	t.Run("for use of closed network connection", func(t *testing.T) {
+		err := errors.New("read tcp 10.0.2.15:56948->93.184.216.34:443: use of closed network connection")
+		if ClassifyGenericError(err) != FailureConnectionAlreadyClosed {
+			t.Fatal("unexpected results")
+		}
+	})
+
 	// Now we're back in ClassifyGenericError
 
 	t.Run("for context.Canceled", func(t *testing.T) {
@@ -87,8 +94,8 @@ func TestClassifyGenericError(t *testing.T) {
 
 	t.Run("for unknown errors", func(t *testing.T) {
 		t.Run("with an IPv4 address", func(t *testing.T) {
-			input := errors.New("read tcp 10.0.2.15:56948->93.184.216.34:443: use of closed network connection")
+			input := errors.New("read tcp 10.0.2.15:56948->93.184.216.34:443: some error")
-			expected := "unknown_failure: read tcp [scrubbed]->[scrubbed]: use of closed network connection"
+			expected := "unknown_failure: read tcp [scrubbed]->[scrubbed]: some error"
 			out := ClassifyGenericError(input)
 			if out != expected {
 				t.Fatal(cmp.Diff(expected, out))
@@ -96,8 +103,8 @@ func TestClassifyGenericError(t *testing.T) {
 		})
 
 		t.Run("with an IPv6 address", func(t *testing.T) {
-			input := errors.New("read tcp [::1]:56948->[::1]:443: use of closed network connection")
+			input := errors.New("read tcp [::1]:56948->[::1]:443: some error")
-			expected := "unknown_failure: read tcp [scrubbed]->[scrubbed]: use of closed network connection"
+			expected := "unknown_failure: read tcp [scrubbed]->[scrubbed]: some error"
 			out := ClassifyGenericError(input)
 			if out != expected {
 				t.Fatal(cmp.Diff(expected, out))

internal/netxlite/errorsx/errno.go

@@ -1,5 +1,5 @@
 // Code generated by go generate; DO NOT EDIT.
-// Generated: 2021-09-08 23:09:33.336763 +0200 CEST m=+0.192836793
+// Generated: 2021-09-27 14:20:26.411929 +0200 CEST m=+0.233208042
 
 package errorsx
 
@@ -58,6 +58,7 @@ const (
 	FailureSSLUnknownAuthority     = "ssl_unknown_authority"
 	FailureSSLInvalidCertificate   = "ssl_invalid_certificate"
 	FailureJSONParseError          = "json_parse_error"
+	FailureConnectionAlreadyClosed = "connection_already_closed"
 )
 
 // failureMap lists all failures so we can match them
@@ -101,6 +102,7 @@ var failuresMap = map[string]string{
 	"ssl_unknown_authority":          "ssl_unknown_authority",
 	"ssl_invalid_certificate":        "ssl_invalid_certificate",
 	"json_parse_error":               "json_parse_error",
+	"connection_already_closed":      "connection_already_closed",
 }
 
 // classifySyscallError converts a syscall error to the

internal/netxlite/errorsx/errno_test.go

@@ -1,5 +1,5 @@
 // Code generated by go generate; DO NOT EDIT.
-// Generated: 2021-09-08 23:09:33.382965 +0200 CEST m=+0.239039834
+// Generated: 2021-09-27 14:20:26.459041 +0200 CEST m=+0.280321626
 
 package errorsx
 

internal/netxlite/errorsx/errno_unix.go

@@ -1,5 +1,5 @@
 // Code generated by go generate; DO NOT EDIT.
-// Generated: 2021-09-08 23:09:33.144513 +0200 CEST m=+0.000582543
+// Generated: 2021-09-27 14:20:26.179327 +0200 CEST m=+0.000601459
 
 package errorsx
 

internal/netxlite/errorsx/errno_windows.go

@@ -1,5 +1,5 @@
 // Code generated by go generate; DO NOT EDIT.
-// Generated: 2021-09-08 23:09:33.310337 +0200 CEST m=+0.166410043
+// Generated: 2021-09-27 14:20:26.380511 +0200 CEST m=+0.201789292
 
 package errorsx
 

internal/netxlite/errorsx/internal/generrno/main.go

@@ -101,6 +101,7 @@ var Specs = []*ErrorSpec{
 	NewLibraryError("SSL_unknown_authority"),
 	NewLibraryError("SSL_invalid_certificate"),
 	NewLibraryError("JSON_parse_error"),
+	NewLibraryError("connection_already_closed"),
 }
 
 func fileCreate(filename string) *os.File {