From be186602f961768f3f2a237753c0f2cb8b4fdc2e Mon Sep 17 00:00:00 2001
From: paulhu <paulhu@google.com>
Date: Tue, 12 Apr 2022 07:18:23 +0000
Subject: [PATCH] Deal with non-ASCII characters on resolution info

The service name can include non-ASCII characters. So
NsdService need to have specific handling for these non-ASCII
characters that make resolution working properly.

Note: The unescape() method is the same one that was used in S,
but was removed by mistake.

Bug: 230698801
Test: atest FrameworksNetTests CtsNetTestCases
Change-Id: I42fc5618aa2d549ceae25f516ad17c78930ea41d
---
 .../src/com/android/server/NsdService.java    | 31 ++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index 4086e4ec9b..6816e82a27 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -513,7 +513,7 @@ public class NsdService extends INsdManager.Stub {
                             break;
                         }
 
-                        String name = fullName.substring(0, index);
+                        String name = unescape(fullName.substring(0, index));
                         String rest = fullName.substring(index);
                         String type = rest.replace(".local.", "");
 
@@ -590,6 +590,35 @@ public class NsdService extends INsdManager.Stub {
        }
     }
 
+    // The full service name is escaped from standard DNS rules on mdnsresponder, making it suitable
+    // for passing to standard system DNS APIs such as res_query() . Thus, make the service name
+    // unescape for getting right service address. See "Notes on DNS Name Escaping" on
+    // external/mdnsresponder/mDNSShared/dns_sd.h for more details.
+    private String unescape(String s) {
+        StringBuilder sb = new StringBuilder(s.length());
+        for (int i = 0; i < s.length(); ++i) {
+            char c = s.charAt(i);
+            if (c == '\\') {
+                if (++i >= s.length()) {
+                    Log.e(TAG, "Unexpected end of escape sequence in: " + s);
+                    break;
+                }
+                c = s.charAt(i);
+                if (c != '.' && c != '\\') {
+                    if (i + 2 >= s.length()) {
+                        Log.e(TAG, "Unexpected end of escape sequence in: " + s);
+                        break;
+                    }
+                    c = (char) ((c - '0') * 100 + (s.charAt(i + 1) - '0') * 10
+                            + (s.charAt(i + 2) - '0'));
+                    i += 2;
+                }
+            }
+            sb.append(c);
+        }
+        return sb.toString();
+    }
+
     @VisibleForTesting
     NsdService(Context ctx, Handler handler, long cleanupDelayMs) {
         mCleanupDelayMs = cleanupDelayMs;