#include
void CRYPTO_set_locking_callback(void (*locking_function)(int mode, int n, const char *file, int line));
void CRYPTO_set_id_callback(unsigned long (*id_function)(void));
void CRYPTO_set_idptr_callback(void *(*idptr_function)(void));
int CRYPTO_num_locks(void);
/* struct CRYPTO_dynlock_value needs to be defined by the user */ struct CRYPTO_dynlock_value;
void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value * (*dyn_create_function)(char *file, int line)); void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function) (int mode, struct CRYPTO_dynlock_value *l, const char *file, int line)); void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function) (struct CRYPTO_dynlock_value *l, const char *file, int line));
int CRYPTO_get_new_dynlockid(void);
void CRYPTO_destroy_dynlockid(int i);
void CRYPTO_lock(int mode, int n, const char *file, int line);
#define CRYPTO_w_lock(type) \ CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__) #define CRYPTO_w_unlock(type) \ CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__) #define CRYPTO_r_lock(type) \ CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__) #define CRYPTO_r_unlock(type) \ CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__) #define CRYPTO_add(addr,amount,type) \ CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
locking_function(int mode, int n, const char *file, int line) is needed to perform locking on shared data structures. (Note that OpenSSL uses a number of global data structures that will be implicitly shared whenever multiple threads use OpenSSL.) Multi-threaded applications will crash at random if it is not set.
_l_o_c_k_i_n_g___f_u_n_c_t_i_o_n_(_) must be able to handle up to _C_R_Y_P_T_O___n_u_m___l_o_c_k_s_(_) different mutex locks. It sets the nn-th lock if mmooddee & CCRRYYPPTTOO__LLOOCCKK, and releases it otherwise.
ffiillee and lliinnee are the file number of the function setting the lock. They can be useful for debugging.
id_function(void) is a function that returns a numerical thread ID, for example _p_t_h_r_e_a_d___s_e_l_f_(_) if it returns an integer (see NOTES below). By OpenSSL's defaults, this is not needed on Windows nor on platforms where _g_e_t_p_i_d_(_) returns a different ID for each thread (see NOTES below).
idptr_function(void) is a function that similarly returns a thread ID, but of type void *. This is not needed on platforms where &errno is different for each thread.
Additionally, OpenSSL supports dynamic locks, and sometimes, some parts of OpenSSL need it for better performance. To enable this, the following is required:
struct CRYPTO_dynlock_value has to be defined to contain whatever structure is needed to handle locks.
dyn_create_function(const char *file, int line) is needed to create a lock. Multi-threaded applications might crash at random if it is not set.
dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line) is needed to perform locking off dynamic lock numbered n. Multi-threaded applications might crash at random if it is not set.
dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is needed to destroy the lock l. Multi-threaded applications might crash at random if it is not set.
_C_R_Y_P_T_O___g_e_t___n_e_w___d_y_n_l_o_c_k_i_d_(_) is used to create locks. It will call dyn_create_function for the actual creation.
_C_R_Y_P_T_O___d_e_s_t_r_o_y___d_y_n_l_o_c_k_i_d_(_) is used to destroy locks. It will call dyn_destroy_function for the actual destruction.
_C_R_Y_P_T_O___l_o_c_k_(_) is used to lock and unlock the locks. mode is a bitfield describing what should be done with the lock. n is the number of the lock as returned from _C_R_Y_P_T_O___g_e_t___n_e_w___d_y_n_l_o_c_k_i_d_(_). mode can be combined from the following values. These values are pairwise exclusive, with undefined behaviour if misused (for example, CRYPTO_READ and CRYPTO_WRITE should not be used together):
CRYPTO_LOCK 0x01 CRYPTO_UNLOCK 0x02 CRYPTO_READ 0x04 CRYPTO_WRITE 0x08
_C_R_Y_P_T_O___g_e_t___n_e_w___d_y_n_l_o_c_k_i_d_(_) returns the index to the newly created lock.
The other functions return no values.
#define OPENSSL_THREAD_DEFINES #include#if defined(OPENSSL_THREADS) // thread support enabled #else // no thread support #endif
Also, dynamic locks are currently not used internally by OpenSSL, but may do so in the future.
Defining id_function(void) has it's own issues. Generally speaking, _p_t_h_r_e_a_d___s_e_l_f_(_) should be used, even on platforms where _g_e_t_p_i_d_(_) gives different answers in each thread, since that may depend on the machine the program is run on, not the machine where the program is being compiled. For instance, Red Hat 8 Linux and earlier used LinuxThreads, whose _g_e_t_p_i_d_(_) returns a different value for each thread. Red Hat 9 Linux and later use NPTL, which is Posix-conformant, and has a _g_e_t_p_i_d_(_) that returns the same value for all threads in a process. A program compiled on Red Hat 8 and run on Red Hat 9 will therefore see _g_e_t_p_i_d_(_) returning the same value for all threads.
There is still the issue of platforms where _p_t_h_r_e_a_d___s_e_l_f_(_) returns something other than an integer. It is for cases like this that _C_R_Y_P_T_O___s_e_t___i_d_p_t_r___c_a_l_l_b_a_c_k_(_) comes in handy. (E.g., call _m_a_l_l_o_c(1) once in each thread, and have _i_d_p_t_r___f_u_n_c_t_i_o_n_(_) return a pointer to this object.) Note that if neither _i_d___f_u_n_c_t_i_o_n_(_) or _i_d_p_t_r___f_u_n_c_t_i_o_n_(_) are provided, OpenSSL will use (&errno) as a fallback (as this usually returns a unique address for each thread).
_C_R_Y_P_T_O___s_e_t___i_d_p_t_r___c_a_l_l_b_a_c_k_(_) was added in OpenSSL 0.9.9.