A new behaviour was introduced in OpenSSL 1.1.1e, when a peer does not send
close_notify before closing the connection. Previously, it was to return
SSL_ERROR_SYSCALL with errno 0, known since at least OpenSSL 0.9.7, and is
handled gracefully in unitd. Now it returns SSL_ERROR_SSL with a distinct
reason SSL_R_UNEXPECTED_EOF_WHILE_READING ("unexpected eof while reading").
This leads to critical errors seen in nginx within various routines such as
SSL_do_handshake(), SSL_read(), SSL_shutdown(). The behaviour was restored
in OpenSSL 1.1.1f, but presents in OpenSSL 3.0 by default.
Use of the SSL_OP_IGNORE_UNEXPECTED_EOF option added in OpenSSL 3.0 allows
setting a compatible behaviour to return SSL_ERROR_ZERO_RETURN:
https://git.openssl.org/?p=openssl.git;a=commitdiff;h=09b90e0
See for additional details: https://github.com/openssl/openssl/issues/11381
The macro is used to suppress deprecation warnings with OpenSSL 3.0.
Unlike OPENSSL_API_COMPAT, it works well with OpenSSL built with no-deprecated.
In particular, it doesn't unhide various macros in OpenSSL includes, which are
meant to be hidden under OPENSSL_NO_DEPRECATED.
In case nxt_unit_tracking_read() failed, execution would jump to the error path,
where it could try to release buffers from uninitialized yet incoming_buf queue.
Use double quotes to quote a string with the backslash/newline pair.
Newer gmake versions, such as GNU Make 4.1, do not remove the backslash
from a string quoted with single quotes, which results in an extraneous
backslash passed to the shell and, eventually, to the Go compiler.
Redefinition of typedef is a C11 feature. On older compilers that
default to C99, such as clang 3.4.1 supplied with FreeBSD 10, this
caused -Wtypedef-redefinition warnings.
Sergey Kandaurov