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+Some old versions of OpenSSL have a bug with memory BIOs, where DTLSv1_listen consumes the ClientHello out of the BIO,
+but then do_handshake expects the ClientHello to still be in there (but not the one that ships with Ubuntu 20.04). In
+particular, this is known to affect the OpenSSL v1.1.1 that ships with Ubuntu 18.04. To work around this, we used to deliver a
+second copy of the ClientHello after DTLSv1_listen has completed. This was safe to do unconditionally, because on newer
+versions of OpenSSL, the second ClientHello is treated as a duplicate packet, which is a normal thing that can happen
+over UDP. For more details, see:
+
+    https://github.com/pyca/pyopenssl/blob/e84e7b57d1838de70ab7a27089fbee78ce0d2106/tests/test_ssl.py#L4226-L4293
+
+This was fixed in v1.1.1a, and all later versions. So now we should be able to delete this. The fix landed in
+OpenSSL master as 079ef6bd534d2, and then was backported to the 1.1.1 branch as d1bfd8076e28.