These APIs were used by Chromium to control the carve-out for the TLS
1.3 downgrade signal. As of
https://chromium-review.googlesource.com/c/chromium/src/+/2324170,
Chromium no longer uses them.
Update-Note: SSL_CTX_set_ignore_tls13_downgrade,
SSL_set_ignore_tls13_downgrade, and SSL_is_tls13_downgrade now do
nothing. Calls sites should be removed. (There are some copies of older
Chromium lying around, so I haven't removed the functions yet.) The
enforcement was already on by default, so this CL does not affect
callers that don't use those functions.
Change-Id: I016af8291cd92051472d239c4650602fe2a68f5b
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/44124
Reviewed-by: Adam Langley <agl@google.com>