[tor-commits] [tor/master] prop224: Clear list of prev hsdirs before we upload all descs.

[nickm at torproject.org]

commit b9f849bdee20f36264fe061498536e0d3a8616a6
Author: George Kadianakis <desnacked at riseup.net>
Date:   Tue Aug 29 16:02:01 2017 +0300

    prop224: Clear list of prev hsdirs before we upload all descs.
    
    This fixes a serious bug in our hsdir set change logic:
    
    We used to add nodes in the list of previous hsdirs everytime we
    uploaded to a new hsdir and we only cleared the list when we built a new
    descriptor. This means that our prev_hsdirs list could end up with 7
    hsdirs, if for some reason we ended up uploading our desc to 7 hsdirs
    before rebuilding our descriptor (e.g. this can happen if the set of
    hsdirs changed).
    
    After our previous hdsir set had 7 nodes, then our old algorithm would
    always think that the set has changed since it was comparing a smartlist
    with 7 elements against a smartlist with 6 elements.
    
    This commit fixes this bug, by clearning the prev_hsdirs list before we
    upload to all hsdirs. This makes sure that our prev_hsdirs list always
    contains the latest hsdirs!
---
 src/or/hs_service.c       | 4 ++++
 src/test/test_hs_common.c | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/or/hs_service.c b/src/or/hs_service.c
index 0fba0d7f9..218d49ace 100644
--- a/src/or/hs_service.c
+++ b/src/or/hs_service.c
@@ -2316,6 +2316,10 @@ upload_descriptor_to_all(const hs_service_t *service,
   hs_get_responsible_hsdirs(&desc->blinded_kp.pubkey, desc->time_period_num,
                             for_next_period, 0, responsible_dirs);
 
+  /** Clear list of previous hsdirs since we are about to upload to a new
+   *  list. Let's keep it up to date. */
+  service_desc_clear_previous_hsdirs(desc);
+
   /* For each responsible HSDir we have, initiate an upload command. */
   SMARTLIST_FOREACH_BEGIN(responsible_dirs, const routerstatus_t *,
                           hsdir_rs) {
diff --git a/src/test/test_hs_common.c b/src/test/test_hs_common.c
index 6bb03f39d..998089295 100644
--- a/src/test/test_hs_common.c
+++ b/src/test/test_hs_common.c
@@ -613,10 +613,10 @@ test_desc_reupload_logic(void *arg)
   tt_int_op(service_desc_hsdirs_changed(service, desc), OP_EQ, 1);
   tt_int_op(smartlist_len(desc->previous_hsdirs), OP_EQ, 6);
 
-  /* Now order another upload and see how we end up with 7 hsdirs */
+  /* Now order another upload and see that we keep having 6 prev hsdirs */
   upload_descriptor_to_all(service, desc, 0);
   /* Check that previous hsdirs were populated */
-  tt_int_op(smartlist_len(desc->previous_hsdirs), OP_EQ, 7);
+  tt_int_op(smartlist_len(desc->previous_hsdirs), OP_EQ, 6);
 
   /* Now restore the HSDir hash ring to its original state by swapping back
      aaron for nora */