Document necessary error code processing

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16187)

diff --git a/doc/man7/migration_guide.pod b/doc/man7/migration_guide.pod
index 462ef9f12217c83c1c993cdf087556f43a4c06cd..8cc017dfa67edc186fbf73c638fe67003a9187c5 100644 (file)
--- a/doc/man7/migration_guide.pod
+++ b/doc/man7/migration_guide.pod
@@ -469,6 +469,18 @@ Remove your usage of the low level APIs. In this case you will need to rewrite y
 
 =back
 
+=head3 Error code changes
+
+As OpenSSL 3.0 provides a brand new Encoder/Decoder mechanism for working with
+widely used file formats, application code that checks for particular error
+reason codes on key loading failures might need an update.
+
+Password-protected keys may deserve special attention. If only some errors
+are treated as an indicator that the user should be asked about the password again,
+it's worth testing these scenarios and processing the newly relevant codes.
+
+There may be more cases to treat specially, depending on the calling application code.
+
 =head2 Upgrading from OpenSSL 1.0.2
 
 Upgrading to OpenSSL 3.0 from OpenSSL 1.0.2 is likely to be significantly more