175 lines
6 KiB
Text
175 lines
6 KiB
Text
=pod
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=head1 NAME
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CRYPTO_set_locking_callback, CRYPTO_set_id_callback, CRYPTO_num_locks,
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CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
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CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
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CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread support
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=head1 SYNOPSIS
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#include <openssl/crypto.h>
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void CRYPTO_set_locking_callback(void (*locking_function)(int mode,
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int n, const char *file, int line));
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void CRYPTO_set_id_callback(unsigned long (*id_function)(void));
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int CRYPTO_num_locks(void);
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/* struct CRYPTO_dynlock_value needs to be defined by the user */
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struct CRYPTO_dynlock_value;
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void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
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(*dyn_create_function)(char *file, int line));
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void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
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(int mode, struct CRYPTO_dynlock_value *l,
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const char *file, int line));
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void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
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(struct CRYPTO_dynlock_value *l, const char *file, int line));
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int CRYPTO_get_new_dynlockid(void);
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void CRYPTO_destroy_dynlockid(int i);
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void CRYPTO_lock(int mode, int n, const char *file, int line);
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#define CRYPTO_w_lock(type) \
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CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
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#define CRYPTO_w_unlock(type) \
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CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
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#define CRYPTO_r_lock(type) \
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CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__)
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#define CRYPTO_r_unlock(type) \
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CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__)
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#define CRYPTO_add(addr,amount,type) \
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CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
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=head1 DESCRIPTION
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OpenSSL can safely be used in multi-threaded applications provided
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that at least two callback functions are set.
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locking_function(int mode, int n, const char *file, int line) is
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needed to perform locking on shared data structures.
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(Note that OpenSSL uses a number of global data structures that
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will be implicitly shared whenever multiple threads use OpenSSL.)
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Multi-threaded applications will crash at random if it is not set.
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locking_function() must be able to handle up to CRYPTO_num_locks()
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different mutex locks. It sets the B<n>-th lock if B<mode> &
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B<CRYPTO_LOCK>, and releases it otherwise.
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B<file> and B<line> are the file number of the function setting the
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lock. They can be useful for debugging.
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id_function(void) is a function that returns a thread ID, for example
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pthread_self() if it returns an integer (see NOTES below). It isn't
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needed on Windows nor on platforms where getpid() returns a different
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ID for each thread (see NOTES below).
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Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
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of OpenSSL need it for better performance. To enable this, the following
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is required:
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=over 4
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=item *
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Three additional callback function, dyn_create_function, dyn_lock_function
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and dyn_destroy_function.
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=item *
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A structure defined with the data that each lock needs to handle.
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=back
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struct CRYPTO_dynlock_value has to be defined to contain whatever structure
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is needed to handle locks.
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dyn_create_function(const char *file, int line) is needed to create a
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lock. Multi-threaded applications might crash at random if it is not set.
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dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line)
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is needed to perform locking off dynamic lock numbered n. Multi-threaded
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applications might crash at random if it is not set.
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dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is
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needed to destroy the lock l. Multi-threaded applications might crash at
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random if it is not set.
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CRYPTO_get_new_dynlockid() is used to create locks. It will call
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dyn_create_function for the actual creation.
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CRYPTO_destroy_dynlockid() is used to destroy locks. It will call
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dyn_destroy_function for the actual destruction.
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CRYPTO_lock() is used to lock and unlock the locks. mode is a bitfield
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describing what should be done with the lock. n is the number of the
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lock as returned from CRYPTO_get_new_dynlockid(). mode can be combined
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from the following values. These values are pairwise exclusive, with
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undefined behaviour if misused (for example, CRYPTO_READ and CRYPTO_WRITE
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should not be used together):
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CRYPTO_LOCK 0x01
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CRYPTO_UNLOCK 0x02
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CRYPTO_READ 0x04
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CRYPTO_WRITE 0x08
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=head1 RETURN VALUES
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CRYPTO_num_locks() returns the required number of locks.
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CRYPTO_get_new_dynlockid() returns the index to the newly created lock.
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The other functions return no values.
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=head1 NOTES
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You can find out if OpenSSL was configured with thread support:
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#define OPENSSL_THREAD_DEFINES
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#include <openssl/opensslconf.h>
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#if defined(OPENSSL_THREADS)
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// thread support enabled
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#else
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// no thread support
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#endif
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Also, dynamic locks are currently not used internally by OpenSSL, but
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may do so in the future.
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Defining id_function(void) has it's own issues. Generally speaking,
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pthread_self() should be used, even on platforms where getpid() gives
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different answers in each thread, since that may depend on the machine
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the program is run on, not the machine where the program is being
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compiled. For instance, Red Hat 8 Linux and earlier used
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LinuxThreads, whose getpid() returns a different value for each
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thread. Red Hat 9 Linux and later use NPTL, which is
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Posix-conformant, and has a getpid() that returns the same value for
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all threads in a process. A program compiled on Red Hat 8 and run on
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Red Hat 9 will therefore see getpid() returning the same value for
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all threads.
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There is still the issue of platforms where pthread_self() returns
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something other than an integer. This is a bit unusual, and this
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manual has no cookbook solution for that case.
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=head1 EXAMPLES
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B<crypto/threads/mttest.c> shows examples of the callback functions on
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Solaris, Irix and Win32.
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=head1 HISTORY
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CRYPTO_set_locking_callback() and CRYPTO_set_id_callback() are
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available in all versions of SSLeay and OpenSSL.
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CRYPTO_num_locks() was added in OpenSSL 0.9.4.
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All functions dealing with dynamic locks were added in OpenSSL 0.9.5b-dev.
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=head1 SEE ALSO
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L<crypto(3)|crypto(3)>
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=cut
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