[or-cvs] r8571: Disprefer exit nodes for entry, middle positions (fixes bug (in tor/trunk: . doc src/or)
nickm at seul.org
nickm at seul.org
Sun Oct 1 21:59:10 UTC 2006
Author: nickm
Date: 2006-10-01 17:59:09 -0400 (Sun, 01 Oct 2006)
New Revision: 8571
Modified:
tor/trunk/
tor/trunk/ChangeLog
tor/trunk/doc/TODO
tor/trunk/doc/path-spec.txt
tor/trunk/src/or/circuitbuild.c
tor/trunk/src/or/or.h
tor/trunk/src/or/rendservice.c
tor/trunk/src/or/routerlist.c
Log:
r8826 at totoro: nickm | 2006-10-01 17:58:45 -0400
Disprefer exit nodes for entry, middle positions (fixes bug 200). Also, switch to using a uint64_t to hold "total bandwidth for all nodes" under consideration; crypt_rand_int would have died at 2GB/s network capacity.
Property changes on: tor/trunk
___________________________________________________________________
svk:merge ticket from /tor/trunk [r8826] on 96637b51-b116-0410-a10e-9941ebb49b64
Modified: tor/trunk/ChangeLog
===================================================================
--- tor/trunk/ChangeLog 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/ChangeLog 2006-10-01 21:59:09 UTC (rev 8571)
@@ -47,6 +47,9 @@
and including the function name only seems to confuse users.
- Fix CIRC controller events so that controllers can learn the identity
digests of non-Named servers used in circuit paths. (Fixes bug 336.)
+ - Avoid choosing Exit nodes for entry or middle hops when the bandwidth
+ available in non-Exit nodes is much higher then the bandwidth available
+ in Exit nodes. (Fixes bug 200.)
o Security Fixes, minor:
- If a client asked for a server by name, and we didn't have a
@@ -93,6 +96,8 @@
With the old code, if a guard was unreachable by us but listed as
running, it would clog our guard list forever.
- Make eventdns give strings for DNS errors, not just error numbers.
+ - Be prepared in case we ever have a network with more than 2GB per
+ second total advertised capacity.
o Documentation
- Documented (and renamed) ServerDNSSearchDomains and
Modified: tor/trunk/doc/TODO
===================================================================
--- tor/trunk/doc/TODO 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/doc/TODO 2006-10-01 21:59:09 UTC (rev 8571)
@@ -35,12 +35,10 @@
D The right thing here is to revamp our node selection implementation.
(Deferred until oprofile says this matters.)
o make it configurable, so people can turn it on or off.
-N - Add script to grep for identical log msgs.
-N - Bug 200: disprefer exit nodes for entry, middle.
- - If less than 1/3 support port X, only use as exit.
- - If 2/3 support port X, weight exits 1/2; weight non-exits 1.
- - (Exit fraction - 1/3):Non-exit fraction
- - (e - 1/3)/(1-e)
+ o Add script to grep for identical log msgs.
+ o Bug 200: disprefer exit nodes for entry, middle.
+ o Specify
+ o Implement
o Bug 303: block exit from circuits created with create-fast
o Specify and document
o Implement
Modified: tor/trunk/doc/path-spec.txt
===================================================================
--- tor/trunk/doc/path-spec.txt 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/doc/path-spec.txt 2006-10-01 21:59:09 UTC (rev 8571)
@@ -157,16 +157,25 @@
below)
- XXXX Choosing the length
- For circuits that are not "fast", when choosing among multiple
- candidates for a path element, we choose randomly. For "fast" circuits,
- we choose
- a given router with probability proportional to its advertised bandwidth
- [the smaller of the 'rate' and 'observed' arguments to the "bandwidth"
- element in its descriptor]. If a router's advertised bandwidth is greater
- than MAX_BELIEVEABLE_BANDWIDTH (1.5 MB/sec), we clip to that value.
+ For circuits that do not need to be not "fast", when choosing among
+ multiple candidates for a path element, we choose randomly.
- (XXXX We should do something to shift traffic away from exit nodes.)
+ For "fast" circuits, we a given router as an exit with probability
+ proportional to its advertised bandwidth [the smaller of the 'rate' and
+ 'observed' arguments to the "bandwidth" element in its descriptor]. If a
+ router's advertised bandwidth is greater than MAX_BELIEVEABLE_BANDWIDTH
+ (1.5 MB/sec), we clip to that value.
+ For non-exit positions on "fast" circuits, we pick routers as above, but
+ we weight the clipped advertised bandwidth of Exit-flagged nodes depending
+ on the fraction of bandwidth available from non-Exit nodes. Call the
+ total clipped advertised bandwidth for Exit nodes under consideration E,
+ and the total clipped advertised bandwidth for non-Exit nodes under
+ consideration N. If E<N/2, we do not consider Exit-flagged nodes.
+ Otherwise, we weight their bandwidth with the factor (E-N/2)/(N+E-N/2) ==
+ (2E - N)/(2E + N). This ensures that bandwidth is evenly distributed over
+ nodes in 3-hop paths.
+
Additionally, we may be building circuits with one or more requests in
mind. Each kind of request puts certain constraints on paths:
Modified: tor/trunk/src/or/circuitbuild.c
===================================================================
--- tor/trunk/src/or/circuitbuild.c 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/src/or/circuitbuild.c 2006-10-01 21:59:09 UTC (rev 8571)
@@ -1199,7 +1199,7 @@
smartlist_subtract(sl,excludedexits);
if (options->StrictExitNodes || smartlist_overlap(sl,preferredexits))
smartlist_intersect(sl,preferredexits);
- router = routerlist_sl_choose_by_bandwidth(sl);
+ router = routerlist_sl_choose_by_bandwidth(sl, 1);
} else {
/* Either there are no pending connections, or no routers even seem to
* possibly support any of them. Choose a router at random that satisfies
@@ -1238,7 +1238,7 @@
smartlist_intersect(sl,preferredexits);
/* XXX sometimes the above results in null, when the requested
* exit node is down. we should pick it anyway. */
- router = routerlist_sl_choose_by_bandwidth(sl);
+ router = routerlist_sl_choose_by_bandwidth(sl, 1);
if (router)
break;
}
@@ -1282,14 +1282,14 @@
if (is_internal) /* pick it like a middle hop */
return router_choose_random_node(NULL, get_options()->ExcludeNodes,
NULL, need_uptime, need_capacity, 0,
- get_options()->_AllowInvalid & ALLOW_INVALID_MIDDLE, 0);
+ get_options()->_AllowInvalid & ALLOW_INVALID_MIDDLE, 0, 0);
else
return choose_good_exit_server_general(dir,need_uptime,need_capacity);
case CIRCUIT_PURPOSE_C_ESTABLISH_REND:
return router_choose_random_node(
options->RendNodes, options->RendExcludeNodes,
NULL, need_uptime, need_capacity, 0,
- options->_AllowInvalid & ALLOW_INVALID_RENDEZVOUS, 0);
+ options->_AllowInvalid & ALLOW_INVALID_RENDEZVOUS, 0, 0);
}
log_warn(LD_BUG,"Bug: unhandled purpose %d", purpose);
tor_fragile_assert();
@@ -1508,7 +1508,7 @@
choice = router_choose_random_node(preferred,
options->ExcludeNodes, excluded,
state->need_uptime, state->need_capacity, 0,
- options->_AllowInvalid & ALLOW_INVALID_MIDDLE, 0);
+ options->_AllowInvalid & ALLOW_INVALID_MIDDLE, 0, 0);
if (preferred)
tor_free(preferred);
smartlist_free(excluded);
@@ -1571,7 +1571,7 @@
excluded, state ? state->need_uptime : 0,
state ? state->need_capacity : 0,
state ? 0 : 1,
- options->_AllowInvalid & ALLOW_INVALID_ENTRY, 0);
+ options->_AllowInvalid & ALLOW_INVALID_ENTRY, 0, 0);
smartlist_free(excluded);
return choice;
}
Modified: tor/trunk/src/or/or.h
===================================================================
--- tor/trunk/src/or/or.h 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/src/or/or.h 2006-10-01 21:59:09 UTC (rev 8571)
@@ -918,6 +918,7 @@
unsigned int is_fast:1; /** Do we think this is a fast OR? */
unsigned int is_stable:1; /** Do we think this is a stable OR? */
unsigned int is_possible_guard:1; /**< Do we think this is an OK guard? */
+ unsigned int is_exit:1; /**< Do we think this is an OK exit? */
/** Tor can use this desc for circuit-building. */
#define ROUTER_PURPOSE_GENERAL 0
@@ -2562,13 +2563,15 @@
int router_is_unreliable(routerinfo_t *router, int need_uptime,
int need_capacity, int need_guard);
uint32_t router_get_advertised_bandwidth(routerinfo_t *router);
-routerinfo_t *routerlist_sl_choose_by_bandwidth(smartlist_t *sl);
+routerinfo_t *routerlist_sl_choose_by_bandwidth(smartlist_t *sl, int for_exit);
+
routerinfo_t *router_choose_random_node(const char *preferred,
const char *excluded,
smartlist_t *excludedsmartlist,
int need_uptime, int need_bandwidth,
int need_guard,
- int allow_invalid, int strict);
+ int allow_invalid, int strict,
+ int weight_for_exit);
routerinfo_t *router_get_by_nickname(const char *nickname,
int warn_if_unnamed);
routerinfo_t *router_get_by_hexdigest(const char *hexdigest);
Modified: tor/trunk/src/or/rendservice.c
===================================================================
--- tor/trunk/src/or/rendservice.c 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/src/or/rendservice.c 2006-10-01 21:59:09 UTC (rev 8571)
@@ -1005,7 +1005,7 @@
router = router_choose_random_node(service->intro_prefer_nodes,
service->intro_exclude_nodes, exclude_routers, 1, 0, 0,
get_options()->_AllowInvalid & ALLOW_INVALID_INTRODUCTION,
- 0);
+ 0, 0);
if (!router) {
log_warn(LD_REND,
"Could only establish %d introduction points for %s.",
Modified: tor/trunk/src/or/routerlist.c
===================================================================
--- tor/trunk/src/or/routerlist.c 2006-10-01 21:59:05 UTC (rev 8570)
+++ tor/trunk/src/or/routerlist.c 2006-10-01 21:59:09 UTC (rev 8571)
@@ -884,46 +884,70 @@
* the advertised bandwidth of each router.
*/
routerinfo_t *
-routerlist_sl_choose_by_bandwidth(smartlist_t *sl)
+routerlist_sl_choose_by_bandwidth(smartlist_t *sl, int for_exit)
{
int i;
routerinfo_t *router;
- smartlist_t *bandwidths;
- uint32_t this_bw, tmp, total_bw=0, rand_bw;
- uint32_t *p;
+ uint32_t *bandwidths;
+ uint32_t this_bw;
+ uint64_t total_nonexit_bw = 0, total_exit_bw = 0, total_bw = 0;
+ uint64_t rand_bw, tmp;
+ double exit_weight;
/* First count the total bandwidth weight, and make a smartlist
* of each value. */
- bandwidths = smartlist_create();
+ bandwidths = tor_malloc(sizeof(uint32_t)*smartlist_len(sl));
for (i = 0; i < smartlist_len(sl); ++i) {
router = smartlist_get(sl, i);
this_bw = router_get_advertised_bandwidth(router);
/* if they claim something huge, don't believe it */
if (this_bw > MAX_BELIEVABLE_BANDWIDTH)
this_bw = MAX_BELIEVABLE_BANDWIDTH;
- p = tor_malloc(sizeof(uint32_t));
- *p = this_bw;
- smartlist_add(bandwidths, p);
- total_bw += this_bw;
+ bandwidths[i] = this_bw;
+ if (router->is_exit)
+ total_exit_bw += this_bw;
+ else
+ total_nonexit_bw += this_bw;
}
- if (!total_bw) {
- SMARTLIST_FOREACH(bandwidths, uint32_t*, p, tor_free(p));
- smartlist_free(bandwidths);
+ if (!(total_exit_bw+total_nonexit_bw)) {
+ tor_free(bandwidths);
return smartlist_choose(sl);
}
+ if (for_exit) {
+ exit_weight = 1.0;
+ total_bw = total_exit_bw + total_nonexit_bw;
+ } else if (total_exit_bw < total_nonexit_bw / 2) {
+ exit_weight = 0.0;
+ total_bw = total_nonexit_bw;
+ } else {
+ uint64_t leftover = (total_exit_bw - total_nonexit_bw / 2);
+ exit_weight = U64_TO_DBL(leftover) /
+ U64_TO_DBL(leftover + total_nonexit_bw);
+ total_bw = total_nonexit_bw +
+ DBL_TO_U64(exit_weight * U64_TO_DBL(total_exit_bw));
+ }
+ /*
+ log_debug(LD_CIRC, "Total bw = "U64_FORMAT", total exit bw = "U64_FORMAT
+ ", total nonexit bw = "U64_FORMAT", exit weight = %lf "
+ "(for exit == %d)",
+ U64_PRINTF_ARG(total_bw), U64_PRINTF_ARG(total_exit_bw),
+ U64_PRINTF_ARG(total_nonexit_bw), exit_weight, for_exit);
+ */
+
/* Second, choose a random value from the bandwidth weights. */
- rand_bw = crypto_rand_int(total_bw);
+ rand_bw = crypto_rand_uint64(total_bw);
/* Last, count through sl until we get to the element we picked */
tmp = 0;
- for (i=0; ; i++) {
- tor_assert(i < smartlist_len(sl));
- p = smartlist_get(bandwidths, i);
- tmp += *p;
+ for (i=0; i < smartlist_len(sl); i++) {
+ router = smartlist_get(sl, i);
+ if (router->is_exit)
+ tmp += ((uint64_t)(bandwidths[i] * exit_weight));
+ else
+ tmp += bandwidths[i];
if (tmp >= rand_bw)
break;
}
- SMARTLIST_FOREACH(bandwidths, uint32_t*, p, tor_free(p));
- smartlist_free(bandwidths);
+ tor_free(bandwidths);
return (routerinfo_t *)smartlist_get(sl, i);
}
@@ -944,7 +968,8 @@
smartlist_t *excludedsmartlist,
int need_uptime, int need_capacity,
int need_guard,
- int allow_invalid, int strict)
+ int allow_invalid, int strict,
+ int weight_for_exit)
{
smartlist_t *sl, *excludednodes;
routerinfo_t *choice = NULL;
@@ -975,8 +1000,8 @@
smartlist_subtract(sl,excludedsmartlist);
routerlist_sl_remove_unreliable_routers(sl, need_uptime,
need_capacity, need_guard);
- if (need_capacity)
- choice = routerlist_sl_choose_by_bandwidth(sl);
+ if (need_capacity) /* XXXX Is this documented in path spec. -NM */
+ choice = routerlist_sl_choose_by_bandwidth(sl, weight_for_exit);
else
choice = smartlist_choose(sl);
smartlist_free(sl);
@@ -989,7 +1014,8 @@
need_uptime?", stable":"",
need_guard?", guard":"");
choice = router_choose_random_node(
- NULL, excluded, excludedsmartlist, 0, 0, 0, allow_invalid, 0);
+ NULL, excluded, excludedsmartlist,
+ 0, 0, 0, allow_invalid, 0, weight_for_exit);
}
}
smartlist_free(excludednodes);
@@ -3422,6 +3448,7 @@
router->is_fast = rs->status.is_fast;
router->is_stable = rs->status.is_stable;
router->is_possible_guard = rs->status.is_possible_guard;
+ router->is_exit = rs->status.is_exit;
}
if (router->is_running && ds) {
ds->n_networkstatus_failures = 0;
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