Merge pull request #280953 from duongau/afdheaders

Front Door - Rules engine action (add note about reserved headers)

Author: prmerger-automator[bot]

articles/frontdoor/front-door-rules-engine-actions.md

@@ -6,7 +6,7 @@ services: frontdoor
 author: duongau
 ms.service: frontdoor
 ms.topic: conceptual
-ms.date: 05/07/2024
+ms.date: 07/16/2024
 ms.author: duau
 zone_pivot_groups: front-door-tiers
 ---
@@ -237,6 +237,39 @@ In this example, we append the value `AdditionalValue` to the `MyRequestHeader`
 
 ---
 
+> [!NOTE]
+> Certain Azure Front Door reserved headers can't be modified using rules engine actions, including the actions to modify request headers and response headers. The following list of reserved headers can't be modified, along with any headers prefixed with `x-ec` and `x-fd`.
+>
+> * `Accept-Ranges`
+> * `Host`
+> * `Connection`
+> * `Content-Length`
+> * `Transfer-Encoding`
+> * `TE`
+> * `Last-Modified`
+> * `Keep-Alive`
+> * `Expect`
+> * `Upgrade`
+> * `If-Modified-Since`
+> * `If-Unmodified-Since`
+> * `If-None-Match`
+> * `If-Match`
+> * `Range`
+> * `If-Range`
+> * `X-Ms-Via`
+> * `X-Ms-Force-Refresh`
+> * `X-MSEdge-Ref`
+> * `Warning`
+> * `Forwarded`
+> * `Via`
+> * `X-Forwarded-For`
+> * `X-Forwarded-Proto`
+> * `X-Forwarded-Host`
+> * `X-Azure-RequestChain`
+> * `X-Azure-FDID`
+> * `X-Azure-RequestChainv2`
+> * `X-Azure-Ref`
+
 ## <a name="ModifyResponseHeader"></a> Modify response header
 
 Use the **modify response header** action to modify headers that are present in responses before they're returned to your clients.
@@ -285,6 +318,39 @@ In this example, we delete the header with the name `X-Powered-By` from the resp
 
 ---
 
+> [!NOTE]
+> Certain Azure Front Door reserved headers can't be modified using rules engine actions, including the actions to modify request headers and response headers. The following list of reserved headers can't be modified, along with any headers prefixed with `x-ec` and `x-fd`.
+>
+> * `Accept-Ranges`
+> * `Host`
+> * `Connection`
+> * `Content-Length`
+> * `Transfer-Encoding`
+> * `TE`
+> * `Last-Modified`
+> * `Keep-Alive`
+> * `Expect`
+> * `Upgrade`
+> * `If-Modified-Since`
+> * `If-Unmodified-Since`
+> * `If-None-Match`
+> * `If-Match`
+> * `Range`
+> * `If-Range`
+> * `X-Ms-Via`
+> * `X-Ms-Force-Refresh`
+> * `X-MSEdge-Ref`
+> * `Warning`
+> * `Forwarded`
+> * `Via`
+> * `X-Forwarded-For`
+> * `X-Forwarded-Proto`
+> * `X-Forwarded-Host`
+> * `X-Azure-RequestChain`
+> * `X-Azure-FDID`
+> * `X-Azure-RequestChainv2`
+> * `X-Azure-Ref`
+
 ## <a name="UrlRedirect"></a> URL redirect
 
 Use the **URL redirect** action to redirect clients to a new URL. Clients are sent a redirection response from Front Door. Azure Front Door supports dynamic capture of URL path with `{url_path:seg#}` server variable, and converts URL path to lowercase or uppercase with `{url_path.tolower}` or `{url_path.toupper}`. For more information, see [Server variables](rule-set-server-variables.md).