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Rewrite state transition logic in entry_guards_note_success()

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asn found while testing that this function can be reached with
GUARD_STATE_COMPLETE circuits; I believe this happens when
cannibalization occurs.

The added complexity of handling one more state made it reasonable
to turn the main logic here into a switch statement.
This commit is contained in:
Nick Mathewson 2016-12-08 10:22:23 -05:00
parent 2e2f3a4d99
commit fc7751a989
1 changed files with 23 additions and 17 deletions
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40
src/or/entrynodes.c
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@ -1927,25 +1927,31 @@ entry_guards_note_guard_success(guard_selection_t *gs,
}
unsigned new_state;
if (old_state == GUARD_CIRC_STATE_USABLE_ON_COMPLETION) {
new_state = GUARD_CIRC_STATE_COMPLETE;
} else {
tor_assert_nonfatal(
old_state == GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD);
if (guard->is_primary) {
/* XXXX prop271 -- I don't actually like this logic. It seems to make us
* a little more susceptible to evil-ISP attacks. The mitigations I'm
* thinking of, however, aren't local to this point, so I'll leave it
* alone. */
/* This guard may have become primary by virtue of being confirmed.
If so, the circuit for it is now complete.
*/
switch (old_state) {
case GUARD_CIRC_STATE_COMPLETE:
case GUARD_CIRC_STATE_USABLE_ON_COMPLETION:
new_state = GUARD_CIRC_STATE_COMPLETE;
} else {
new_state = GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD;
}
break;
default:
tor_assert_nonfatal_unreached();
/* Fall through. */
case GUARD_CIRC_STATE_USABLE_IF_NO_BETTER_GUARD:
if (guard->is_primary) {
/* XXXX prop271 -- I don't actually like this logic. It seems to make
* us a little more susceptible to evil-ISP attacks. The mitigations
* I'm thinking of, however, aren't local to this point, so I'll leave
* it alone. */
/* This guard may have become primary by virtue of being confirmed.
* If so, the circuit for it is now complete.
*/
new_state = GUARD_CIRC_STATE_COMPLETE;
} else {
new_state = GUARD_CIRC_STATE_WAITING_FOR_BETTER_GUARD;
}
break;
}
if (! guard->is_primary) {
if (last_time_on_internet + get_internet_likely_down_interval()
< approx_time()) {
mark_primary_guards_maybe_reachable(gs);