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Merge remote branch 'origin/maint-0.2.2'

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This commit is contained in:
Nick Mathewson 2010-09-30 15:30:14 -04:00
commit d39e46c26d
3 changed files with 37 additions and 2 deletions
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9
changes/bug1912 Normal file
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@ -0,0 +1,9 @@
o Major bugfixes:
- When weighting bridges, we used to trust the bandwidths they provided
in their descriptor, only capping them at 10MB/s. This turned out to be
problematic for two reasons: Bridges could claim to handle a lot more
traffic then they actually would, thus making more clients pick them and
have a pretty effective DoS attack. The other issue is that new bridges
that might not have a good estimate for their bw capacity yet would not
get used at all unless no other bridges are available to a client.
This fixes bug 1912; bugfix on 0.2.2.7-alpha.

1
src/common/util.c
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@ -2877,3 +2877,4 @@ load_windows_system_library(const TCHAR *library_name)
return LoadLibrary(path);
}
#endif

29
src/or/routerlist.c
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@ -1579,6 +1579,29 @@ router_get_advertised_bandwidth_capped(routerinfo_t *router)
return result;
}
/** When weighting bridges, enforce these values as lower and upper
* bound for believable bandwidth, because there is no way for us
* to verify a bridge's bandwidth currently. */
#define BRIDGE_MIN_BELIEVABLE_BANDWIDTH 20000 /* 20 kB/sec */
#define BRIDGE_MAX_BELIEVABLE_BANDWIDTH 100000 /* 100 kB/sec */
/** Return the smaller of the router's configured BandwidthRate
* and its advertised capacity, making sure to stay within the
* interval between bridge-min-believe-bw and
* bridge-max-believe-bw. */
static uint32_t
bridge_get_advertised_bandwidth_bounded(routerinfo_t *router)
{
uint32_t result = router->bandwidthcapacity;
if (result > router->bandwidthrate)
result = router->bandwidthrate;
if (result > BRIDGE_MAX_BELIEVABLE_BANDWIDTH)
result = BRIDGE_MAX_BELIEVABLE_BANDWIDTH;
else if (result < BRIDGE_MIN_BELIEVABLE_BANDWIDTH)
result = BRIDGE_MIN_BELIEVABLE_BANDWIDTH;
return result;
}
/** Return bw*1000, unless bw*1000 would overflow, in which case return
* INT32_MAX. */
static INLINE int32_t
@ -1733,7 +1756,7 @@ smartlist_choose_by_bandwidth_weights(smartlist_t *sl,
if (rs && rs->has_bandwidth) {
this_bw = kb_to_bytes(rs->bandwidth);
} else { /* bridge or other descriptor not in our consensus */
this_bw = router_get_advertised_bandwidth_capped(router);
this_bw = bridge_get_advertised_bandwidth_bounded(router);
have_unknown = 1;
}
if (router_digest_is_me(router->cache_info.identity_digest))
@ -1904,7 +1927,7 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, bandwidth_weight_rule_t rule,
flags |= is_exit ? 2 : 0;
flags |= is_guard ? 4 : 0;
} else /* bridge or other descriptor not in our consensus */
this_bw = router_get_advertised_bandwidth_capped(router);
this_bw = bridge_get_advertised_bandwidth_bounded(router);
}
if (is_exit)
bitarray_set(exit_bits, i);
@ -1912,6 +1935,8 @@ smartlist_choose_by_bandwidth(smartlist_t *sl, bandwidth_weight_rule_t rule,
bitarray_set(guard_bits, i);
if (is_known) {
bandwidths[i] = (int32_t) this_bw; // safe since MAX_BELIEVABLE<INT32_MAX
// XXX this is no longer true! We don't always cap the bw anymore. Can
// a consensus make us overflow?-sh
tor_assert(bandwidths[i] >= 0);
if (is_guard)
total_guard_bw += this_bw;