When you use append_hf, the new headers are only used for messages that are sent! Calling is_present_hf or a similar function will RETURN FALSE if you are looking for a header you added.
append_hf(“Test: Test\r\n”); is_present_hf(“Test”); ←– This will return FALSE
route {
append_hf("Test: Test\r\n"); t_on_failure(2);
}
failure_route[1] {
is_present_hf("Test"); <--- This will return FALSE
}
So this should not be used for storing any kind of state. This is mentioned only briefly in “known limitations” section.