wip

Author: jandro996

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/http/ClientIpAddressResolver.java

@@ -204,96 +204,105 @@ enum ForwardedParseState {
 
     @Override
     public InetAddress apply(String headerValue) {
-      String[] entries = headerValue.split(",");
-      for (int i = entries.length - 1; i >= 0; i--) {
-        String entry = entries[i].trim();
-        InetAddress resultPrivate = null;
-        ForwardedParseState state = ForwardedParseState.BETWEEN;
-        // https://datatracker.ietf.org/doc/html/rfc7239#section-4
-        int pos = 0;
-        int end = entry.length();
-        // compiler requires that these two be initialized:
-        int start = 0;
-        boolean considerValue = false;
-        while (pos < end) {
-          char c = entry.charAt(pos);
-          switch (state) {
-            case BETWEEN:
-              if (c == ' ' || c == ';' || c == ',') {
+      int end = headerValue.length();
+      int entryEnd = end;
+      // Parse entries right-to-left, separated by ','
+      for (int i = end - 1; i >= -1; i--) {
+        if (i == -1 || headerValue.charAt(i) == ',') {
+          int entryStart = i + 1;
+          // skip leading spaces
+          while (entryStart < entryEnd && headerValue.charAt(entryStart) == ' ') {
+            entryStart++;
+          }
+          String entry = headerValue.substring(entryStart, entryEnd);
+          InetAddress resultPrivate = null;
+          ForwardedParseState state = ForwardedParseState.BETWEEN;
+          // https://datatracker.ietf.org/doc/html/rfc7239#section-4
+          int pos = 0;
+          int entryLen = entry.length();
+          // compiler requires that these two be initialized:
+          int start = 0;
+          boolean considerValue = false;
+          while (pos < entryLen) {
+            char c = entry.charAt(pos);
+            switch (state) {
+              case BETWEEN:
+                if (c == ' ' || c == ';' || c == ',') {
+                  break;
+                }
+                start = pos;
+                state = ForwardedParseState.KEY;
                 break;
-              }
-              start = pos;
-              state = ForwardedParseState.KEY;
-              break;
-            case KEY:
-              if (c != '=') {
+              case KEY:
+                if (c != '=') {
+                  break;
+                }
+                state = ForwardedParseState.BEFORE_VALUE;
+                if (pos - start == 3) {
+                  String key = entry.substring(start, pos);
+                  considerValue = key.equalsIgnoreCase("for");
+                } else {
+                  considerValue = false;
+                }
                 break;
-              }
-
-              state = ForwardedParseState.BEFORE_VALUE;
-              if (pos - start == 3) {
-                String key = entry.substring(start, pos);
-                considerValue = key.equalsIgnoreCase("for");
-              } else {
-                considerValue = false;
-              }
-              break;
-            case BEFORE_VALUE:
-              if (c == '"') {
-                start = pos + 1;
-                state = ForwardedParseState.VALUE_QUOTED;
-              } else if (c == ' ' || c == ';' || c == ',') {
-                // empty value
-                state = ForwardedParseState.BETWEEN;
-              } else {
-                start = pos;
-                state = ForwardedParseState.VALUE_TOKEN;
-              }
-              break;
-            case VALUE_TOKEN:
-              {
-                int tokenEnd;
-                if (c == ' ' || c == ';' || c == ',') {
-                  tokenEnd = pos;
-                } else if (pos + 1 == end) {
-                  tokenEnd = end;
+              case BEFORE_VALUE:
+                if (c == '"') {
+                  start = pos + 1;
+                  state = ForwardedParseState.VALUE_QUOTED;
+                } else if (c == ' ' || c == ';' || c == ',') {
+                  // empty value
+                  state = ForwardedParseState.BETWEEN;
                 } else {
-                  break;
+                  start = pos;
+                  state = ForwardedParseState.VALUE_TOKEN;
                 }
-
-                if (considerValue) {
-                  InetAddress ipAddr = parseIpAddressAndMaybePort(entry.substring(start, tokenEnd));
-                  if (ipAddr != null) {
-                    if (isIpAddrPrivate(ipAddr)) {
-                      if (resultPrivate == null) {
-                        resultPrivate = ipAddr;
+                break;
+              case VALUE_TOKEN:
+                {
+                  int tokenEnd;
+                  if (c == ' ' || c == ';' || c == ',') {
+                    tokenEnd = pos;
+                  } else if (pos + 1 == entryLen) {
+                    tokenEnd = entryLen;
+                  } else {
+                    break;
+                  }
+                  if (considerValue) {
+                    InetAddress ipAddr =
+                        parseIpAddressAndMaybePort(entry.substring(start, tokenEnd));
+                    if (ipAddr != null) {
+                      if (isIpAddrPrivate(ipAddr)) {
+                        if (resultPrivate == null) {
+                          resultPrivate = ipAddr;
+                        }
+                      } else {
+                        return ipAddr;
                       }
-                    } else {
-                      return ipAddr;
                     }
                   }
+                  state = ForwardedParseState.BETWEEN;
+                  break;
                 }
-                state = ForwardedParseState.BETWEEN;
-                break;
-              }
-            case VALUE_QUOTED:
-              if (c == '"') {
-                if (considerValue) {
-                  InetAddress ipAddr = parseIpAddressAndMaybePort(entry.substring(start, pos));
-                  if (ipAddr != null && !isIpAddrPrivate(ipAddr)) {
-                    return ipAddr;
+              case VALUE_QUOTED:
+                if (c == '"') {
+                  if (considerValue) {
+                    InetAddress ipAddr = parseIpAddressAndMaybePort(entry.substring(start, pos));
+                    if (ipAddr != null && !isIpAddrPrivate(ipAddr)) {
+                      return ipAddr;
+                    }
                   }
+                  state = ForwardedParseState.BETWEEN;
+                } else if (c == '\\') {
+                  pos++;
                 }
-                state = ForwardedParseState.BETWEEN;
-              } else if (c == '\\') {
-                pos++;
-              }
-              break;
+                break;
+            }
+            pos++;
           }
-          pos++;
-        }
-        if (resultPrivate != null) {
-          return resultPrivate;
+          if (resultPrivate != null) {
+            return resultPrivate;
+          }
+          entryEnd = i;
         }
       }
       return null;