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https://github.com/openssl/openssl.git
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347 lines
10 KiB
Plaintext
347 lines
10 KiB
Plaintext
=pod
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=for openssl foreign manual atexit(3)
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=head1 NAME
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OSSL_trace_set_channel, OSSL_trace_set_prefix, OSSL_trace_set_suffix,
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OSSL_trace_set_callback, OSSL_trace_cb - Enabling trace output
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=head1 SYNOPSIS
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#include <openssl/trace.h>
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typedef size_t (*OSSL_trace_cb)(const char *buf, size_t cnt,
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int category, int cmd, void *data);
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void OSSL_trace_set_channel(int category, BIO *bio);
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void OSSL_trace_set_prefix(int category, const char *prefix);
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void OSSL_trace_set_suffix(int category, const char *suffix);
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void OSSL_trace_set_callback(int category, OSSL_trace_cb cb, void *data);
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=head1 DESCRIPTION
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If available (see L</Configure Tracing> below), the application can request
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internal trace output.
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This output comes in form of free text for humans to read.
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The trace output is divided into categories which can be
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enabled individually.
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Every category can be enabled individually by attaching a so-called
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I<trace channel> to it, which in the simplest case is just a BIO object
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to which the application can write the tracing output for this category.
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Alternatively, the application can provide a tracer callback in order to
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get more finegrained trace information. This callback will be wrapped
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internally by a dedicated BIO object.
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For the tracing code, both trace channel types are indistinguishable.
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These are called a I<simple trace channel> and a I<callback trace channel>,
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respectively.
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L<OSSL_TRACE_ENABLED(3)> can be used to check whether tracing is currently
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enabled for the given category.
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Functions like L<OSSL_TRACE1(3)> and macros like L<OSSL_TRACE_BEGIN(3)>
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can be used for producing free-text trace output.
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=head2 Functions
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OSSL_trace_set_channel() is used to enable the given trace C<category>
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by attaching the B<BIO> I<bio> object as (simple) trace channel.
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On success the ownership of the BIO is transferred to the channel,
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so the caller must not free it directly.
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OSSL_trace_set_prefix() and OSSL_trace_set_suffix() can be used to add
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an extra line for each channel, to be output before and after group of
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tracing output.
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What constitutes an output group is decided by the code that produces
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the output.
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The lines given here are considered immutable; for more dynamic
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tracing prefixes, consider setting a callback with
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OSSL_trace_set_callback() instead.
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OSSL_trace_set_callback() is used to enable the given trace
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I<category> by giving it the tracer callback I<cb> with the associated
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data I<data>, which will simply be passed through to I<cb> whenever
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it's called. The callback function is internally wrapped by a
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dedicated BIO object, the so-called I<callback trace channel>.
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This should be used when it's desirable to do form the trace output to
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something suitable for application needs where a prefix and suffix
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line aren't enough.
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OSSL_trace_set_channel() and OSSL_trace_set_callback() are mutually
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exclusive, calling one of them will clear whatever was set by the
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previous call.
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Calling OSSL_trace_set_channel() with NULL for I<channel> or
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OSSL_trace_set_callback() with NULL for I<cb> disables tracing for
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the given I<category>.
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=head2 Trace callback
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The tracer callback must return a B<size_t>, which must be zero on
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error and otherwise return the number of bytes that were output.
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It receives a text buffer I<buf> with I<cnt> bytes of text, as well as
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the I<category>, a control number I<cmd>, and the I<data> that was
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passed to OSSL_trace_set_callback().
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The possible control numbers are:
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=over 4
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=item B<OSSL_TRACE_CTRL_BEGIN>
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The callback is called from OSSL_trace_begin(), which gives the
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callback the possibility to output a dynamic starting line, or set a
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prefix that should be output at the beginning of each line, or
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something other.
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=item B<OSSL_TRACE_CTRL_WRITE>
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This callback is called whenever data is written to the BIO by some
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regular BIO output routine.
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An arbitrary number of B<OSSL_TRACE_CTRL_WRITE> callbacks can occur
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inside a group marked by a pair of B<OSSL_TRACE_CTRL_BEGIN> and
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B<OSSL_TRACE_CTRL_END> calls, but never outside such a group.
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=item B<OSSL_TRACE_CTRL_END>
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The callback is called from OSSL_trace_end(), which gives the callback
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the possibility to output a dynamic ending line, or reset the line
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prefix that was set with B<OSSL_TRACE_CTRL_BEGIN>, or something other.
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=back
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=head2 Trace categories
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The trace categories are simple numbers available through macros.
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=over 4
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=item B<OSSL_TRACE_CATEGORY_TRACE>
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Traces the OpenSSL trace API itself.
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More precisely, this will generate trace output any time a new
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trace hook is set.
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=item B<OSSL_TRACE_CATEGORY_INIT>
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Traces OpenSSL library initialization and cleanup.
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This needs special care, as OpenSSL will do automatic cleanup after
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exit from C<main()>, and any tracing output done during this cleanup
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will be lost if the tracing channel or callback were cleaned away
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prematurely.
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A suggestion is to make such cleanup part of a function that's
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registered very early with L<atexit(3)>.
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=item B<OSSL_TRACE_CATEGORY_TLS>
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Traces the TLS/SSL protocol.
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=item B<OSSL_TRACE_CATEGORY_TLS_CIPHER>
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Traces the ciphers used by the TLS/SSL protocol.
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=item B<OSSL_TRACE_CATEGORY_CONF>
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Traces details about the provider and engine configuration.
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=item B<OSSL_TRACE_CATEGORY_ENGINE_TABLE>
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Traces the ENGINE algorithm table selection.
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More precisely, functions like ENGINE_get_pkey_asn1_meth_engine(),
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ENGINE_get_pkey_meth_engine(), ENGINE_get_cipher_engine(),
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ENGINE_get_digest_engine(), will generate trace summaries of the
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handling of internal tables.
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=item B<OSSL_TRACE_CATEGORY_ENGINE_REF_COUNT>
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Traces the ENGINE reference counting.
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More precisely, both reference counts in the ENGINE structure will be
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monitored with a line of trace output generated for each change.
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=item B<OSSL_TRACE_CATEGORY_PKCS5V2>
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Traces PKCS#5 v2 key generation.
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=item B<OSSL_TRACE_CATEGORY_PKCS12_KEYGEN>
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Traces PKCS#12 key generation.
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=item B<OSSL_TRACE_CATEGORY_PKCS12_DECRYPT>
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Traces PKCS#12 decryption.
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=item B<OSSL_TRACE_CATEGORY_X509V3_POLICY>
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Traces X509v3 policy processing.
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More precisely, this generates the complete policy tree at various
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point during evaluation.
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=item B<OSSL_TRACE_CATEGORY_BN_CTX>
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Traces BIGNUM context operations.
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=item B<OSSL_TRACE_CATEGORY_CMP>
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Traces CMP client and server activity.
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=item B<OSSL_TRACE_CATEGORY_STORE>
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Traces STORE operations.
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=item B<OSSL_TRACE_CATEGORY_DECODER>
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Traces decoder operations.
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=item B<OSSL_TRACE_CATEGORY_ENCODER>
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Traces encoder operations.
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=item B<OSSL_TRACE_CATEGORY_REF_COUNT>
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Traces decrementing certain ASN.1 structure references.
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=item B<OSSL_TRACE_CATEGORY_HTTP>
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Traces the HTTP client, such as message headers being sent and received.
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=back
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There is also B<OSSL_TRACE_CATEGORY_ALL>, which works as a fallback
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and can be used to get I<all> trace output.
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Note, however, that in this case all trace output will effectively be
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associated with the 'ALL' category, which is undesirable if the
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application intends to include the category name in the trace output.
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In this case it is better to register separate channels for each
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trace category instead.
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=head1 RETURN VALUES
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OSSL_trace_set_channel(), OSSL_trace_set_prefix(),
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OSSL_trace_set_suffix(), and OSSL_trace_set_callback() return 1 on
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success, or 0 on failure.
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=head1 EXAMPLES
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In all examples below, the trace producing code is assumed to be
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the following:
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int foo = 42;
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const char bar[] = { 0, 1, 2, 3, 4, 5, 6, 7,
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8, 9, 10, 11, 12, 13, 14, 15 };
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OSSL_TRACE_BEGIN(TLS) {
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BIO_puts(trc_out, "foo: ");
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BIO_printf(trc_out, "%d\n", foo);
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BIO_dump(trc_out, bar, sizeof(bar));
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} OSSL_TRACE_END(TLS);
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=head2 Simple example
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An example with just a channel and constant prefix / suffix.
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int main(int argc, char *argv[])
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{
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BIO *err = BIO_new_fp(stderr, BIO_NOCLOSE | BIO_FP_TEXT);
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OSSL_trace_set_channel(OSSL_TRACE_CATEGORY_SSL, err);
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OSSL_trace_set_prefix(OSSL_TRACE_CATEGORY_SSL, "BEGIN TRACE[TLS]");
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OSSL_trace_set_suffix(OSSL_TRACE_CATEGORY_SSL, "END TRACE[TLS]");
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/* ... work ... */
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}
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When the trace producing code above is performed, this will be output
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on standard error:
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BEGIN TRACE[TLS]
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foo: 42
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0000 - 00 01 02 03 04 05 06 07-08 09 0a 0b 0c 0d 0e 0f ................
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END TRACE[TLS]
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=head2 Advanced example
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This example uses the callback, and depends on pthreads functionality.
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static size_t cb(const char *buf, size_t cnt,
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int category, int cmd, void *vdata)
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{
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BIO *bio = vdata;
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const char *label = NULL;
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switch (cmd) {
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case OSSL_TRACE_CTRL_BEGIN:
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label = "BEGIN";
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break;
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case OSSL_TRACE_CTRL_END:
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label = "END";
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break;
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}
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if (label != NULL) {
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union {
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pthread_t tid;
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unsigned long ltid;
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} tid;
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tid.tid = pthread_self();
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BIO_printf(bio, "%s TRACE[%s]:%lx\n",
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label, OSSL_trace_get_category_name(category), tid.ltid);
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}
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return (size_t)BIO_puts(bio, buf);
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}
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int main(int argc, char *argv[])
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{
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BIO *err = BIO_new_fp(stderr, BIO_NOCLOSE | BIO_FP_TEXT);
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OSSL_trace_set_callback(OSSL_TRACE_CATEGORY_SSL, cb, err);
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/* ... work ... */
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}
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The output is almost the same as for the simple example above.
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BEGIN TRACE[TLS]:7f9eb0193b80
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foo: 42
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0000 - 00 01 02 03 04 05 06 07-08 09 0a 0b 0c 0d 0e 0f ................
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END TRACE[TLS]:7f9eb0193b80
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=head1 NOTES
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=head2 Configure Tracing
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By default, the OpenSSL library is built with tracing disabled. To
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use the tracing functionality documented here, it is therefore
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necessary to configure and build OpenSSL with the 'enable-trace' option.
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When the library is built with tracing disabled, the macro
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B<OPENSSL_NO_TRACE> is defined in F<< <openssl/opensslconf.h> >> and all
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functions described here are inoperational, i.e. will do nothing.
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=head1 SEE ALSO
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L<OSSL_TRACE_ENABLED(3)>, L<OSSL_TRACE_BEGIN(3)>, L<OSSL_TRACE1(3)>,
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L<atexit(3)>
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=head1 HISTORY
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OSSL_trace_set_channel(), OSSL_trace_set_prefix(),
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OSSL_trace_set_suffix(), and OSSL_trace_set_callback() were all added
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in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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