Add option 3 to connect down policy

doc/admin-guide/files/records.yaml.en.rst

@@ -1833,9 +1833,13 @@ Origin Server Connect Attempts
 .. ts:cv:: CONFIG proxy.config.http.connect.down.policy INT 2
    :overridable:
 
-   Controls what origin server connection failures contribute to marking a server down. When set to 2, any connection failure during the TCP and TLS
-   handshakes will contribute to marking the server down. When set to 1, only TCP handshake failures will contribute to marking a server down.
-   When set to 0, no connection failures will be used towards marking a server down.
+   Controls what origin server connection failures contribute to marking a server down.
+   When set to ``2``, any connection failure during the TCP and TLS handshakes will
+   contribute to marking the server down. When set to ``1``, only TCP handshake failures
+   will contribute to marking a server down. When set to ``0``, no connection failures
+   will be used towards marking a server down. When set to ``3``, all failures covered
+   by ``2`` plus transaction inactive timeouts (server goes silent after connection is
+   established) will contribute to marking a server down.
 
 .. ts:cv:: CONFIG proxy.config.http.server_max_connections INT 0
    :reloadable:

src/proxy/http/HttpSM.cc

@@ -4671,12 +4671,18 @@ HttpSM::track_connect_fail() const
   bool retval = false;
   if (t_state.current.server->had_connect_fail()) {
     // What does our policy say?
-    if (t_state.txn_conf->connect_down_policy == 2) { // Any connection error through TLS handshake
+    if (t_state.txn_conf->connect_down_policy == 2 ||
+        t_state.txn_conf->connect_down_policy == 3) { // Any connection error through TLS handshake
       retval = true;
     } else if (t_state.txn_conf->connect_down_policy == 1) { // Any connection error through TCP
       retval = t_state.current.server->connect_result != -ENET_SSL_CONNECT_FAILED;
     }
   }
+  // Policy 3 additionally marks the server down on transaction inactive timeout,
+  // even when had_connect_fail() is false (connect_result was cleared at CONNECTION_ALIVE).
+  if (!retval && t_state.txn_conf->connect_down_policy == 3) {
+    retval = (t_state.current.server->state == HttpTransact::INACTIVE_TIMEOUT);
+  }
   return retval;
 }