1=pod
2
3=head1 NAME
4
5SSL_write - write bytes to a TLS/SSL connection.
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 int SSL_write(SSL *ssl, const void *buf, int num);
12
13=head1 DESCRIPTION
14
15SSL_write() writes B<num> bytes from the buffer B<buf> into the specified
16B<ssl> connection.
17
18=head1 NOTES
19
20If necessary, SSL_write() will negotiate a TLS/SSL session, if
21not already explicitly performed by L<SSL_connect(3)|SSL_connect(3)> or
22L<SSL_accept(3)|SSL_accept(3)>. If the
23peer requests a re-negotiation, it will be performed transparently during
24the SSL_write() operation. The behaviour of SSL_write() depends on the
25underlying BIO.
26
27For the transparent negotiation to succeed, the B<ssl> must have been
| 1=pod
2
3=head1 NAME
4
5SSL_write - write bytes to a TLS/SSL connection.
6
7=head1 SYNOPSIS
8
9 #include <openssl/ssl.h>
10
11 int SSL_write(SSL *ssl, const void *buf, int num);
12
13=head1 DESCRIPTION
14
15SSL_write() writes B<num> bytes from the buffer B<buf> into the specified
16B<ssl> connection.
17
18=head1 NOTES
19
20If necessary, SSL_write() will negotiate a TLS/SSL session, if
21not already explicitly performed by L<SSL_connect(3)|SSL_connect(3)> or
22L<SSL_accept(3)|SSL_accept(3)>. If the
23peer requests a re-negotiation, it will be performed transparently during
24the SSL_write() operation. The behaviour of SSL_write() depends on the
25underlying BIO.
26
27For the transparent negotiation to succeed, the B<ssl> must have been
|
28initialized to client or server mode. This is not the case if a generic
29method is being used (see L<SSL_CTX_new(3)|SSL_CTX_new(3)>, so that
| 28initialized to client or server mode. This is being done by calling
|
30L<SSL_set_connect_state(3)|SSL_set_connect_state(3)> or SSL_set_accept_state()
| 29L<SSL_set_connect_state(3)|SSL_set_connect_state(3)> or SSL_set_accept_state()
|
31must be used before the first call to an L<SSL_read(3)|SSL_read(3)>
32or SSL_write() function.
| 30before the first call to an L<SSL_read(3)|SSL_read(3)> or SSL_write() function.
|
33
34If the underlying BIO is B<blocking>, SSL_write() will only return, once the
35write operation has been finished or an error occurred, except when a
36renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
37This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
38L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
39
40If the underlying BIO is B<non-blocking>, SSL_write() will also return,
41when the underlying BIO could not satisfy the needs of SSL_write()
42to continue the operation. In this case a call to
43L<SSL_get_error(3)|SSL_get_error(3)> with the
44return value of SSL_write() will yield B<SSL_ERROR_WANT_READ> or
45B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
46call to SSL_write() can also cause read operations! The calling process
47then must repeat the call after taking appropriate action to satisfy the
48needs of SSL_write(). The action depends on the underlying BIO. When using a
49non-blocking socket, nothing is to be done, but select() can be used to check
50for the required condition. When using a buffering BIO, like a BIO pair, data
51must be written into or retrieved out of the BIO before being able to continue.
52
53SSL_write() will only return with success, when the complete contents
54of B<buf> of length B<num> has been written. This default behaviour
55can be changed with the SSL_MODE_ENABLE_PARTIAL_WRITE option of
56L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>. When this flag is set,
57SSL_write() will also return with success, when a partial write has been
58successfully completed. In this case the SSL_write() operation is considered
59completed. The bytes are sent and a new SSL_write() operation with a new
60buffer (with the already sent bytes removed) must be started.
61A partial write is performed with the size of a message block, which is
6216kB for SSLv3/TLSv1.
63
64=head1 WARNING
65
66When an SSL_write() operation has to be repeated because of
67B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
68with the same arguments.
69
70=head1 RETURN VALUES
71
72The following return values can occur:
73
74=over 4
75
76=item E<gt>0
77
78The write operation was successful, the return value is the number of
79bytes actually written to the TLS/SSL connection.
80
81=item 0
82
| 31
32If the underlying BIO is B<blocking>, SSL_write() will only return, once the
33write operation has been finished or an error occurred, except when a
34renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
35This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
36L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
37
38If the underlying BIO is B<non-blocking>, SSL_write() will also return,
39when the underlying BIO could not satisfy the needs of SSL_write()
40to continue the operation. In this case a call to
41L<SSL_get_error(3)|SSL_get_error(3)> with the
42return value of SSL_write() will yield B<SSL_ERROR_WANT_READ> or
43B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
44call to SSL_write() can also cause read operations! The calling process
45then must repeat the call after taking appropriate action to satisfy the
46needs of SSL_write(). The action depends on the underlying BIO. When using a
47non-blocking socket, nothing is to be done, but select() can be used to check
48for the required condition. When using a buffering BIO, like a BIO pair, data
49must be written into or retrieved out of the BIO before being able to continue.
50
51SSL_write() will only return with success, when the complete contents
52of B<buf> of length B<num> has been written. This default behaviour
53can be changed with the SSL_MODE_ENABLE_PARTIAL_WRITE option of
54L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>. When this flag is set,
55SSL_write() will also return with success, when a partial write has been
56successfully completed. In this case the SSL_write() operation is considered
57completed. The bytes are sent and a new SSL_write() operation with a new
58buffer (with the already sent bytes removed) must be started.
59A partial write is performed with the size of a message block, which is
6016kB for SSLv3/TLSv1.
61
62=head1 WARNING
63
64When an SSL_write() operation has to be repeated because of
65B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
66with the same arguments.
67
68=head1 RETURN VALUES
69
70The following return values can occur:
71
72=over 4
73
74=item E<gt>0
75
76The write operation was successful, the return value is the number of
77bytes actually written to the TLS/SSL connection.
78
79=item 0
80
|
83The write operation was not successful. Call SSL_get_error() with the return
84value B<ret> to find out, whether an error occurred.
| 81The write operation was not successful. Probably the underlying connection
82was closed. Call SSL_get_error() with the return value B<ret> to find out,
83whether an error occurred or the connection was shut down cleanly
84(SSL_ERROR_ZERO_RETURN).
|
85
| 85
|
| 86SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
87only be detected, whether the underlying connection was closed. It cannot
88be checked, why the closure happened.
89
|
86=item E<lt>0
87
88The write operation was not successful, because either an error occurred
89or action must be taken by the calling process. Call SSL_get_error() with the
90return value B<ret> to find out the reason.
91
92=back
93
94=head1 SEE ALSO
95
96L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
97L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)|SSL_CTX_new(3)>,
98L<SSL_connect(3)|SSL_connect(3)>, L<SSL_accept(3)|SSL_accept(3)>
99L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>,
100L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>
101
102=cut
| 90=item E<lt>0
91
92The write operation was not successful, because either an error occurred
93or action must be taken by the calling process. Call SSL_get_error() with the
94return value B<ret> to find out the reason.
95
96=back
97
98=head1 SEE ALSO
99
100L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_read(3)|SSL_read(3)>,
101L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)|SSL_CTX_new(3)>,
102L<SSL_connect(3)|SSL_connect(3)>, L<SSL_accept(3)|SSL_accept(3)>
103L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>,
104L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>
105
106=cut
|