Workaround for bug in iOS 14 related to setting LMT flag (#1159)

src/main/java/org/prebid/server/auction/AuctionRequestFactory.java

@@ -38,6 +38,7 @@
 import org.prebid.server.log.ConditionalLogger;
 import org.prebid.server.metric.MetricName;
 import org.prebid.server.privacy.model.PrivacyContext;
+import org.prebid.server.proto.openrtb.ext.request.ExtDevice;
 import org.prebid.server.proto.openrtb.ext.request.ExtMediaTypePriceGranularity;
 import org.prebid.server.proto.openrtb.ext.request.ExtPriceGranularity;
 import org.prebid.server.proto.openrtb.ext.request.ExtPublisher;
@@ -276,7 +277,7 @@ BidRequest fillImplicitParameters(BidRequest bidRequest, RoutingContext context,
         final HttpServerRequest request = context.request();
 
         final Device device = bidRequest.getDevice();
-        final Device populatedDevice = populateDevice(device, request);
+        final Device populatedDevice = populateDevice(device, bidRequest.getApp(), request);
 
         final Site site = bidRequest.getSite();
         final Site populatedSite = bidRequest.getApp() != null ? null : populateSite(site, request);
@@ -334,7 +335,7 @@ private void checkBlacklistedApp(BidRequest bidRequest) {
      * Populates the request body's 'device' section from the incoming http request if the original is partially filled
      * and the request contains necessary info (User-Agent, IP-address).
      */
-    private Device populateDevice(Device device, HttpServerRequest request) {
+    private Device populateDevice(Device device, App app, HttpServerRequest request) {
         final String deviceIp = device != null ? device.getIp() : null;
         final String deviceIpv6 = device != null ? device.getIpv6() : null;
 
@@ -352,10 +353,13 @@ private Device populateDevice(Device device, HttpServerRequest request) {
 
         final String ua = device != null ? device.getUa() : null;
         final Integer dnt = resolveDntHeader(request);
+        final Integer lmt = resolveLmt(device, app);
 
         if (!Objects.equals(deviceIp, resolvedIp)
                 || !Objects.equals(deviceIpv6, resolvedIpv6)
-                || StringUtils.isBlank(ua) || dnt != null) {
+                || StringUtils.isBlank(ua)
+                || dnt != null
+                || lmt != null) {
 
             final Device.DeviceBuilder builder = device == null ? Device.builder() : device.toBuilder();
 
@@ -366,6 +370,10 @@ private Device populateDevice(Device device, HttpServerRequest request) {
                 builder.dnt(dnt);
             }
 
+            if (lmt != null) {
+                builder.lmt(lmt);
+            }
+
             builder
                     .ip(resolvedIp)
                     .ipv6(resolvedIpv6);
@@ -405,6 +413,86 @@ private void logWarnIfNoIp(String resolvedIp, String resolvedIpv6) {
         }
     }
 
+    private Integer resolveLmt(Device device, App app) {
+        if (app == null || device == null || !StringUtils.equalsIgnoreCase(device.getOs(), "ios")) {
+            return null;
+        }
+
+        final String osv = device.getOsv();
+        if (osv == null) {
+            return null;
+        }
+
+        // osv format expected: "[major].[minor]". Example: 14.0
+        final String[] versionParts = StringUtils.split(osv, '.');
+        if (versionParts.length != 2) {
+            return null;
+        }
+
+        final Integer versionMajor = tryParse(versionParts[0]);
+        final Integer versionMinor = tryParse(versionParts[1]);
+        if (versionMajor == null || versionMinor == null) {
+            return null;
+        }
+
+        if (versionMajor < 14) {
+            return null;
+        }
+
+        return resolveLmtForIos14AndHigher(device, versionMinor);
+    }
+
+    private static Integer tryParse(String number) {
+        try {
+            return Integer.parseUnsignedInt(number);
+        } catch (NumberFormatException e) {
+            return null;
+        }
+    }
+
+    private Integer resolveLmtForIos14AndHigher(Device device, Integer versionMinor) {
+        if (versionMinor == 0 || versionMinor == 1) {
+            return resolveLmtForIos14Minor0And1(device);
+        }
+
+        if (versionMinor >= 2) {
+            return resolveLmtForIos14Minor2AndHigher(device);
+        }
+
+        return null;
+    }
+
+    private static Integer resolveLmtForIos14Minor0And1(Device device) {
+        final String ifa = device.getIfa();
+        final Integer lmt = device.getLmt();
+
+        if (StringUtils.isEmpty(ifa) || ifa.equals("00000000-0000-0000-0000-000000000000")) {
+            return !Objects.equals(lmt, 1) ? 1 : null;
+        }
+
+        return !Objects.equals(lmt, 0) ? 0 : null;
+    }
+
+    private static Integer resolveLmtForIos14Minor2AndHigher(Device device) {
+        final ExtDevice deviceExt = device.getExt();
+        final Integer atts = deviceExt != null ? deviceExt.getAtts() : null;
+        final Integer lmt = device.getLmt();
+
+        if (atts == null) {
+            return null;
+        }
+
+        if (atts == 1 || atts == 2) {
+            return !Objects.equals(lmt, 1) ? 1 : null;
+        }
+
+        if (atts == 0 || atts == 3) {
+            return !Objects.equals(lmt, 0) ? 0 : null;
+        }
+
+        return null;
+    }
+
     /**
      * Populates the request body's 'site' section from the incoming http request if the original is partially filled
      * and the request contains necessary info (domain, page).

src/main/java/org/prebid/server/proto/openrtb/ext/request/ExtDevice.java

@@ -13,9 +13,11 @@
 @ToString(callSuper = true)
 public class ExtDevice extends FlexibleExtension {
 
+    Integer atts;
+
     ExtDevicePrebid prebid;
 
     public static ExtDevice empty() {
-        return of(null);
+        return of(null, null);
     }
 }