BUG/MEDIUM: http: don't forward client shutdown without NOLINGER except for tunnels
There's an issue related with shutting down POST transfers or closing the
connection after the end of the upload : the shutdown is forwarded to the
server regardless of the abortonclose option. The problem it causes is that
during a scan, brute force or whatever, it becomes possible that all source
ports are exhausted with all sockets in TIME_WAIT state.
There are multiple issues at once in fact :
- no action is done for the close, it automatically happens at the lower
layers thanks for channel_auto_close(), so we cannot act on NOLINGER ;
- we *do* want to continue to send a clean shutdown in tunnel mode because
some protocols transported over HTTP may need this, regardless of option
abortonclose, thus we can't set the option inconditionally
- for all other modes, we do want to close the dirty way because we're
certain whether we've sent everything or not, and we don't want to eat
all source ports.
The solution is a bit complex and applies to DONE/TUNNEL states :
1) disable automatic close for everything not a tunnel and not just
keep-alive / server-close. Force-close is now covered, as is HTTP/1.0
which implicitly works in force-close mode ;
2) when processing option abortonclose, we know we can disable lingering
if the client has closed and the connection is not in tunnel mode.
Since the last case above leads to a situation where the client side reports
an error, we know the connection will not be reused, so leaving the flag on
the stream-interface is safe. A client closing in the middle of the data
transmission already aborts the transaction so this case is not a problem.
This fix must be backported to 1.5 where the problem was detected.
1 file changed