transports: ssh: disconnect session before freeing it - #4596
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The function `ssh_stream_free` takes over the responsibility of closing
channels and streams just before freeing their memory, but it does not
do so for the session. In fact, we never disconnect the session
ourselves at all, as libssh2 will not do so itself upon freeing the
structure. Quoting the documentation of `libssh2_session_free`:
> Frees all resources associated with a session instance. Typically
> called after libssh2_session_disconnect_ex,
The missing disconnect probably stems from a misunderstanding what it
actually does. As we are already closing the TCP socket ourselves, the
assumption was that no additional disconnect is required. But calling
`libssh2_session_disconnect` will notify the server that we are cleanly
closing the connection, such that the server can free his own resources.
Add a call to `libssh2_session_disconnect` to fix that issue.
[1]: https://www.libssh2.org/libssh2_session_free.html
The function `libssh2_session_startup` has been deprecated since libssh2 version 1.2.8 in favor of `libssh2_session_handshake` introduced in the same version. libssh2 1.2.8 was released in April 2011, so it is already seven years old. It is available in Debian Wheezy, Ubuntu Trusty and CentOS 7.4, so the most important and conservative distros already have it available. As such, it seems safe to just use the new function.
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LGTM, thanks. |
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The function
ssh_stream_freetakes over the responsibility of closingchannels and streams just before freeing their memory, but it does not
do so for the session. In fact, we never disconnect the session
ourselves at all, as libssh2 will not do so itself upon freeing the
structure. Quoting the documentation of
libssh2_session_free:The missing disconnect probably stems from a misunderstanding what it
actually does. As we are already closing the TCP socket ourselves, the
assumption was that no additional disconnect is required. But calling
libssh2_session_disconnectwill notify the server that we are cleanlyclosing the connection, such that the server can free his own resources.
Add a call to
libssh2_session_disconnectto fix that issue.This fixes #3473. After all, it seems to me like the issue report is valid.
The other commit is just swapping out a deprecated function for its newer equivalent.
/cc @carlosmn