TS-3944: Add documentation for TSHttpTxnServerAddrSet to clarify when it can be called.

doc/developer-guide/api/functions/TSHttpTxnServerAddrSet.en.rst

@@ -0,0 +1,42 @@
+.. Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed
+   with this work for additional information regarding copyright
+   ownership.  The ASF licenses this file to you under the Apache
+   License, Version 2.0 (the "License"); you may not use this file
+   except in compliance with the License.  You may obtain a copy of
+   the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied.  See the License for the specific language governing
+   permissions and limitations under the License.
+
+.. include:: ../../../common.defs
+
+.. default-domain:: c
+
+TSHttpTxnServerAddrSet
+**********************
+
+Synopsis
+========
+
+`#include <ts/ts.h>`
+
+.. function:: TSReturnCode TSHttpTxnServerAddrGet(TSHttpTxn txnp, struct sockaddr const* addr)
+
+Description
+===========
+
+Set the origin server address for transaction :arg:`txnp`. This includes the port in :arg:`addr`.
+The address family is also set by the contents of :arg:`addr`. The address data is copied out of
+:arg:`addr` so there is no dependency on the lifetime of that object.
+
+This hook must be called no later than TS_HTTP_OS_DNS_HOOK. If this is called then DNS resolution
+will not be done as the address of the server is already know.
+
+An error value is returned if :arg:`addr` does not contain a valid IPv4 or IPv6 address with a valid
+(non-zero) port.

doc/developer-guide/plugins/hooks-and-transactions/http-transactions.en.rst

@@ -179,6 +179,8 @@ The HTTP transaction functions are:
 
 -  :c:func:`TSHttpTxnNextHopAddrGet`
 
+-  :c:func:`TSHttpTxnNextHopAddrSet`
+
 -  :c:func:`TSHttpTxnParentProxySet`
 
 -  :c:func:`TSHttpTxnReenable`