Add to the Denial of Service section of the man page an explanation about the
three different mitigation Tor has.
Fixes#25248.
Signed-off-by: David Goulet <dgoulet@torproject.org>
This test works by having two post-loop events activate one another
in a tight loop. If the "post-loop" mechanism didn't work, this
would be enough to starve all other events.
A linked connection_t is one that gets its I/O, not from the
network, but from another connection_t. When such a connection has
something to write, we want the corresponding connection to run its
read callback ... but not immediately, to avoid infinite recursion
and/or event loop starvation.
Previously we handled this case by activating the read events
outside the event loop. Now we use the "postloop event" logic.
This lets us simplify do_main_loop_once() a little.
We've been labeling some events as happening "outside the event
loop", to avoid Libevent starvation. This patch provides a cleaner
mechanism to avoid that starvation.
For background, the problem here is that Libevent only scans for new
events once it has run all its active callbacks. So if the
callbacks keep activating new callbacks, they could potentially
starve Libevent indefinitely and keep it from ever checking for
timed, socket, or signal events.
To solve this, we add the ability to label some events as
"post-loop". The rule for a "post-loop" event is that any events
_it_ activates can only be run after libevent has re-scanned for new
events at least once.
This differs from our previous token bucket abstraction in a few
ways:
1) It is an abstraction, and not a collection of fields.
2) It is meant to be used with monotonic timestamps, which should
produce better results than calling gettimeofday over and over.
In d1874b4339, we adjusted this check so that we insist on
using routerinfos for bridges. That's almost correct... but if we
have a bridge that is also a regular relay, then we should use
insist on its routerinfo when connecting to it as a bridge
(directly), and be willing to use its microdescriptor when
connecting to it elsewhere in our circuits.
This bug is a likely cause of some (all?) of the (exit_ei == NULL)
failures we've been seeing.
Fixes bug 25691; bugfix on 0.3.3.4-alpha
When size_t is 32 bits, the unit tests can't fit anything more than
4GB-1 into a size_t.
Additionally, tt_int_op() uses "long" -- we need tt_u64_op() to
safely test uint64_t values for equality.
Bug caused by tests for #24782 fix; not in any released Tor.
This patch changes the algorithm of compute_real_max_mem_in_queues() to
use 0.4 * RAM iff the system has more than or equal to 8 GB of RAM, but
will continue to use the old value of 0.75 * RAM if the system have less
than * GB of RAM available.
This patch also adds tests for compute_real_max_mem_in_queues().
See: https://bugs.torproject.org/24782
This patch makes get_total_system_memory mockable, which allows us to
alter the return value of the function in tests.
See: https://bugs.torproject.org/24782
Nick Mathewson
Mike Perry
David Goulet
Alexander Færøy
Isis Lovecruft