OH 3.3 IPP binding: "bad request" error with CUPS

I’ve been using the IPP binding since OH2. After upgrading from OH 3.2 to OH 3.3, I started getting these warning messages in the log:

2022-10-07 15:24:09.310 [WARN ] [ethz.vppserver.ippclient.IppResponse] - <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
	<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
	<TITLE>Bad Request - CUPS v2.2.10</TITLE>
	<LINK REL="STYLESHEET" TYPE="text/css" HREF="/cups.css">
<H1>Bad Request</H1>

I posted an issue on GIthub, and after setting the CUPS log to DEBUG I saw this:

E [11/Oct/2022:21:52:24 -0700] [Client 1] Request from "" using invalid Host: field "localhost".

The issue appears to be due to a problem in the cups4j library, which was updated in 3.3. The solution is to edit the CUPS configuration (cupsd.conf) to include this line:

ServerAlias localhost

I’m posting here in case anyone else runs into this problem.

For more details, see the Github issue.