Add check for DNS blocking just to make logs more informative

Author: echo-branch

Sources/BranchSDK/BNCServerInterface.m

@@ -122,7 +122,11 @@ - (void)genericHTTPRequest:(NSURLRequest *)request retryNumber:(NSInteger)retryN
 
             } else {
                 if (status != 200) {
-                    [[BranchLogger shared] logWarning: [NSString stringWithFormat:@"Giving up on request with HTTP status code %ld", (long)status] error:underlyingError];
+                    if ([NSError branchDNSBlockingError:underlyingError]) {
+                        [[BranchLogger shared] logWarning:[NSString stringWithFormat:@"Possible DNS Ad Blocker. Giving up on request with HTTP status code %ld", (long)status] error:underlyingError];
+                    } else {
+                        [[BranchLogger shared] logWarning: [NSString stringWithFormat:@"Giving up on request with HTTP status code %ld", (long)status] error:underlyingError];
+                    }
                 }
 
                 // Don't call on the main queue since it might be blocked.
@@ -301,7 +305,7 @@ - (BNCServerResponse *)processServerResponse:(NSURLResponse *)response data:(NSD
         serverResponse.requestId = requestId;
 
         if ([[BranchLogger shared] shouldLog:BranchLogLevelDebug]) {
-            [[BranchLogger shared] logWarning:@"Request failed with NSError" error:error];
+            [[BranchLogger shared] logDebug:@"Request failed with NSError" error:error];
         }
     }
 

Sources/BranchSDK/BNCURLFilter.m

@@ -11,6 +11,7 @@
 #import "BNCURLFilter.h"
 #import "Branch.h"
 #import "BranchLogger.h"
+#import "NSError+Branch.h"
 
 @interface BNCURLFilter ()
 
@@ -130,7 +131,11 @@ - (BOOL)foundUpdatedURLList:(id<BNCNetworkOperationProtocol>)operation {
         [[BranchLogger shared] logDebug:@"No update for URL ignore list found." error:nil];
         return NO;
     } else if (statusCode != 200 || error != nil || jsonString == nil) {
-        [[BranchLogger shared] logWarning:[NSString stringWithFormat:@"Failed to update URL ignore list. error: %@ status: %ld", operation.error, (long)operation.response.statusCode] error:operation.error];
+        if ([NSError branchDNSBlockingError:error]) {
+            [[BranchLogger shared] logWarning:@"Possible DNS Ad Blocker" error:error];
+        } else {
+            [[BranchLogger shared] logWarning:@"Failed to update URL ignore list" error:operation.error];
+        }
         return NO;
     } else {
         return YES;

Sources/BranchSDK/BranchQRCode.m

@@ -143,8 +143,12 @@ - (void)callQRCodeAPI:(nullable NSDictionary *)params
     NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
 
         if (error) {
-            [[BranchLogger shared] logError:@"QR Code request failed" error:error];
-            completion(nil, error);
+            if ([NSError branchDNSBlockingError:error]) {
+                [[BranchLogger shared] logWarning:@"Possible DNS Ad Blocker" error:error];
+            } else {
+                [[BranchLogger shared] logError:@"QR Code request failed" error:error];
+                completion(nil, error);
+            }
             return;
         }
 

Sources/BranchSDK/NSError+Branch.m

@@ -83,4 +83,36 @@ + (NSError *) branchErrorWithCode:(BNCErrorCode)errorCode localizedMessage:(NSSt
     return [NSError branchErrorWithCode:errorCode error:nil localizedMessage:message];
 }
 
++ (BOOL)branchDNSBlockingError:(NSError *)error {
+    if (error) {
+        NSError *underlyingError = error.userInfo[@"NSUnderlyingError"];
+        if (underlyingError) {
+
+            /**
+             Check if an NSError was likely caused by a DNS sinkhole, such as Pi-hole.
+             The OS level logs will show that the IP address that failed is all 0's, however App level logs will not contain that information.
+              
+             `Domain=kCFErrorDomainCFNetwork Code=-1000` - Connection failed due to a malformed URL. A bit misleading since Ad blockers DNS resolve the URL as 0.0.0.0.
+             https://developer.apple.com/documentation/cfnetwork/cfnetworkerrors/kcfurlerrorbadurl?language=objc
+             
+             `_kCFStreamErrorDomainKey=1` Error domain is a POSIX error.
+             https://opensource.apple.com/source/CF/CF-550.13/CFStream.h.auto.html
+                 
+             `_kCFStreamErrorCodeKey=22` POSIX error is invalid argument. In this case the IP address is 0.0.0.0, which is invalid.
+             https://opensource.apple.com/source/xnu/xnu-792/bsd/sys/errno.h.auto.html
+             */
+            BOOL isCFErrorDomainCFNetwork = [((NSString *)kCFErrorDomainCFNetwork) isEqualToString:underlyingError.domain];
+            BOOL isCodeMalFormedURL = [@(-1000) isEqual:@(underlyingError.code)];
+            
+            BOOL isErrorDomainPosix =  [@(1) isEqual:error.userInfo[@"_kCFStreamErrorDomainKey"]];
+            BOOL isPosixInvalidArgument = [@(22) isEqual:error.userInfo[@"_kCFStreamErrorCodeKey"]];
+            
+            if (isCFErrorDomainCFNetwork && isCodeMalFormedURL && isErrorDomainPosix && isPosixInvalidArgument) {
+                return YES;
+            }
+        }
+    }
+    return NO;
+}
+
 @end

Sources/BranchSDK/Private/NSError+Branch.h

@@ -43,6 +43,9 @@ typedef NS_ENUM(NSInteger, BNCErrorCode) {
 + (NSError *) branchErrorWithCode:(BNCErrorCode)errorCode error:(NSError *_Nullable)error;
 + (NSError *) branchErrorWithCode:(BNCErrorCode)errorCode localizedMessage:(NSString *_Nullable)message;
 
+// Checks if an NSError looks like a DNS blocking error
++ (BOOL)branchDNSBlockingError:(NSError *)error;
+
 @end
 
 NS_ASSUME_NONNULL_END