CRYPTO_set_dynlock_create_callback(3ssl)

1threads(3)                          OpenSSL                         threads(3)
2
3
4

NAME

6       CRYPTO_set_locking_callback, CRYPTO_set_id_callback, CRYPTO_num_locks,
7       CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
8       CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
9       CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread support
10

SYNOPSIS

12        #include <openssl/crypto.h>
13
14        void CRYPTO_set_locking_callback(void (*locking_function)(int mode,
15               int n, const char *file, int line));
16
17        void CRYPTO_set_id_callback(unsigned long (*id_function)(void));
18
19        int CRYPTO_num_locks(void);
20
21        /* struct CRYPTO_dynlock_value needs to be defined by the user */
22        struct CRYPTO_dynlock_value;
23
24        void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
25               (*dyn_create_function)(char *file, int line));
26        void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
27               (int mode, struct CRYPTO_dynlock_value *l,
28               const char *file, int line));
29        void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
30               (struct CRYPTO_dynlock_value *l, const char *file, int line));
31
32        int CRYPTO_get_new_dynlockid(void);
33
34        void CRYPTO_destroy_dynlockid(int i);
35
36        void CRYPTO_lock(int mode, int n, const char *file, int line);
37
38        #define CRYPTO_w_lock(type)    \
39               CRYPTO_lock(CRYPTO_LOCK⎪CRYPTO_WRITE,type,__FILE__,__LINE__)
40        #define CRYPTO_w_unlock(type)  \
41               CRYPTO_lock(CRYPTO_UNLOCK⎪CRYPTO_WRITE,type,__FILE__,__LINE__)
42        #define CRYPTO_r_lock(type)    \
43               CRYPTO_lock(CRYPTO_LOCK⎪CRYPTO_READ,type,__FILE__,__LINE__)
44        #define CRYPTO_r_unlock(type)  \
45               CRYPTO_lock(CRYPTO_UNLOCK⎪CRYPTO_READ,type,__FILE__,__LINE__)
46        #define CRYPTO_add(addr,amount,type)   \
47               CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
48

DESCRIPTION

50       OpenSSL can safely be used in multi-threaded applications provided that
51       at least two callback functions are set.
52
53       locking_function(int mode, int n, const char *file, int line) is needed
54       to perform locking on shared data structures.  (Note that OpenSSL uses
55       a number of global data structures that will be implicitly shared when‐
56       ever multiple threads use OpenSSL.)  Multi-threaded applications will
57       crash at random if it is not set.
58
59       locking_function() must be able to handle up to CRYPTO_num_locks() dif‐
60       ferent mutex locks. It sets the n-th lock if mode & CRYPTO_LOCK, and
61       releases it otherwise.
62
63       file and line are the file number of the function setting the lock.
64       They can be useful for debugging.
65
66       id_function(void) is a function that returns a thread ID, for example
67       pthread_self() if it returns an integer (see NOTES below).  It isn't
68       needed on Windows nor on platforms where getpid() returns a different
69       ID for each thread (see NOTES below).
70
71       Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
72       of OpenSSL need it for better performance.  To enable this, the follow‐
73       ing is required:
74
75       * Three additional callback function, dyn_create_function,
76       dyn_lock_function and dyn_destroy_function.
77       * A structure defined with the data that each lock needs to handle.
78
79       struct CRYPTO_dynlock_value has to be defined to contain whatever
80       structure is needed to handle locks.
81
82       dyn_create_function(const char *file, int line) is needed to create a
83       lock.  Multi-threaded applications might crash at random if it is not
84       set.
85
86       dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int
87       line) is needed to perform locking off dynamic lock numbered n. Multi-
88       threaded applications might crash at random if it is not set.
89
90       dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is
91       needed to destroy the lock l. Multi-threaded applications might crash
92       at random if it is not set.
93
94       CRYPTO_get_new_dynlockid() is used to create locks.  It will call
95       dyn_create_function for the actual creation.
96
97       CRYPTO_destroy_dynlockid() is used to destroy locks.  It will call
98       dyn_destroy_function for the actual destruction.
99
100       CRYPTO_lock() is used to lock and unlock the locks.  mode is a bitfield
101       describing what should be done with the lock.  n is the number of the
102       lock as returned from CRYPTO_get_new_dynlockid().  mode can be combined
103       from the following values.  These values are pairwise exclusive, with
104       undefined behaviour if misused (for example, CRYPTO_READ and
105       CRYPTO_WRITE should not be used together):
106
107               CRYPTO_LOCK     0x01
108               CRYPTO_UNLOCK   0x02
109               CRYPTO_READ     0x04
110               CRYPTO_WRITE    0x08
111

RETURN VALUES

113       CRYPTO_num_locks() returns the required number of locks.
114
115       CRYPTO_get_new_dynlockid() returns the index to the newly created lock.
116
117       The other functions return no values.
118

NOTES

120       You can find out if OpenSSL was configured with thread support:
121
122        #define OPENSSL_THREAD_DEFINES
123        #include <openssl/opensslconf.h>
124        #if defined(OPENSSL_THREADS)
125          // thread support enabled
126        #else
127          // no thread support
128        #endif
129
130       Also, dynamic locks are currently not used internally by OpenSSL, but
131       may do so in the future.
132
133       Defining id_function(void) has it's own issues.  Generally speaking,
134       pthread_self() should be used, even on platforms where getpid() gives
135       different answers in each thread, since that may depend on the machine
136       the program is run on, not the machine where the program is being com‐
137       piled.  For instance, Red Hat 8 Linux and earlier used LinuxThreads,
138       whose getpid() returns a different value for each thread.  Red Hat 9
139       Linux and later use NPTL, which is Posix-conformant, and has a getpid()
140       that returns the same value for all threads in a process.  A program
141       compiled on Red Hat 8 and run on Red Hat 9 will therefore see getpid()
142       returning the same value for all threads.
143
144       There is still the issue of platforms where pthread_self() returns
145       something other than an integer.  This is a bit unusual, and this man‐
146       ual has no cookbook solution for that case.
147

EXAMPLES

149       crypto/threads/mttest.c shows examples of the callback functions on
150       Solaris, Irix and Win32.
151

HISTORY

153       CRYPTO_set_locking_callback() and CRYPTO_set_id_callback() are avail‐
154       able in all versions of SSLeay and OpenSSL.  CRYPTO_num_locks() was
155       added in OpenSSL 0.9.4.  All functions dealing with dynamic locks were
156       added in OpenSSL 0.9.5b-dev.
157