X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=doc%2Fssl%2FSSL_shutdown.pod;h=89911acbcac89a89c8de068297be4b7f7858b4ef;hb=5a84b7fc2db33cdefc5a7b62f0169f2c08fb3d9b;hp=ada25c8cae1ef9f8e3b6ddf2ef64828c374d0832;hpb=9e09eebf94c933686077a1b1b2d60248acb9ba67;p=oweals%2Fopenssl.git diff --git a/doc/ssl/SSL_shutdown.pod b/doc/ssl/SSL_shutdown.pod index ada25c8cae..89911acbca 100644 --- a/doc/ssl/SSL_shutdown.pod +++ b/doc/ssl/SSL_shutdown.pod @@ -23,24 +23,38 @@ a currently open session is considered closed and good and will be kept in the session cache for further reuse. The shutdown procedure consists of 2 steps: the sending of the "close notify" -shutdown alert and the receipt ion of the peer's "close notify" shutdown -alert: +shutdown alert and the reception of the peer's "close notify" shutdown +alert. According to the TLS standard, it is acceptable for an application +to only send its shutdown alert and then close the underlying connection +without waiting for the peer's response (this way resources can be saved, +as the process can already terminate or serve another connection). +When the underlying connection shall be used for more communications, the +complete shutdown procedure (bidirectional "close notify" alerts) must be +performed, so that the peers stay synchronized. + +SSL_shutdown() supports both uni- and bidirectional shutdown by its 2 step +behaviour. =over 4 =item When the application is the first party to send the "close notify" -alert, SSL_shutdown() will only send the alert and the set the +alert, SSL_shutdown() will only send the alert and then set the SSL_SENT_SHUTDOWN flag (so that the session is considered good and will -be kept in cache). SSL_shutdown() will then return with 0. In order to -complete the shutdown handshake, SSL_shutdown() must be called again. +be kept in cache). SSL_shutdown() will then return with 0. If a unidirectional +shutdown is enough (the underlying connection shall be closed anyway), this +first call to SSL_shutdown() is sufficient. In order to complete the +bidirectional shutdown handshake, SSL_shutdown() must be called again. The second call will make SSL_shutdown() wait for the peer's "close notify" shutdown alert. On success, the second call to SSL_shutdown() will return with 1. =item If the peer already sent the "close notify" alert B it was -already processed implicitly inside another call of e.g. -B, SSL_shutdown() will send the "close notify" -alert and will immediately return with 1. +already processed implicitly inside another function +(L), the SSL_RECEIVED_SHUTDOWN flag is set. +SSL_shutdown() will send the "close notify" alert, set the SSL_SENT_SHUTDOWN +flag and will immediately return with 1. +Whether SSL_RECEIVED_SHUTDOWN is already set can be checked using the +SSL_get_shutdown() (see also L call. =back @@ -66,6 +80,12 @@ nothing is to be done, but select() can be used to check for the required condition. When using a buffering BIO, like a BIO pair, data must be written into or retrieved out of the BIO before being able to continue. +SSL_shutdown() can be modified to only set the connection to "shutdown" +state but not actually send the "close notify" alert messages, +see L. +When "quiet shutdown" is enabled, SSL_shutdown() will always succeed +and return 1. + =head1 RETURN VALUES The following return values can occur: @@ -79,7 +99,8 @@ and the peer's "close notify" alert was received. =item 0 -The shutdown is not yet finished. Call SSL_shutdown() for a second time. +The shutdown is not yet finished. Call SSL_shutdown() for a second time, +if a bidirectional shutdown shall be performed. The output of L may be misleading, as an erroneous SSL_ERROR_SYSCALL may be flagged even though no error occurred. @@ -97,6 +118,7 @@ to find out the reason. L, L, L, L, +L, L, L, L, L