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Add test-before-evict discipline to addrman

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Changes addrman to use the test-before-evict discipline in which an
address is to be evicted from the tried table is first tested and if
it is still online it is not evicted.

Adds tests to provide test coverage for this change.

This change was suggested as Countermeasure 3 in
Eclipse Attacks on Bitcoin’s Peer-to-Peer Network, Ethan Heilman,
Alison Kendler, Aviv Zohar, Sharon Goldberg. ePrint Archive Report
2015/263. March 2015.
This commit is contained in:
Ethan Heilman
2016-10-27 13:55:39 -04:00
committed by e0
parent bf3353de90
commit e68172ed9f
4 changed files with 319 additions and 19 deletions
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99
src/addrman.cpp
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@@ -187,7 +187,7 @@ void CAddrMan::MakeTried(CAddrInfo& info, int nId)
info.fInTried = true;
}
void CAddrMan::Good_(const CService& addr, int64_t nTime)
void CAddrMan::Good_(const CService& addr, bool test_before_evict, int64_t nTime)
{
int nId;
@@ -233,10 +233,22 @@ void CAddrMan::Good_(const CService& addr, int64_t nTime)
if (nUBucket == -1)
return;
LogPrint(BCLog::ADDRMAN, "Moving %s to tried\n", addr.ToString());
// which tried bucket to move the entry to
int tried_bucket = info.GetTriedBucket(nKey);
int tried_bucket_pos = info.GetBucketPosition(nKey, false, tried_bucket);
// move nId to the tried tables
MakeTried(info, nId);
// Will moving this address into tried evict another entry?
if (test_before_evict && (vvTried[tried_bucket][tried_bucket_pos] != -1)) {
LogPrint(BCLog::ADDRMAN, "addrman", "Collision inserting element into tried table, moving %s to m_tried_collisions=%d\n", addr.ToString(), m_tried_collisions.size());
if (m_tried_collisions.size() < ADDRMAN_SET_TRIED_COLLISION_SIZE) {
m_tried_collisions.insert(nId);
}
} else {
LogPrint(BCLog::ADDRMAN, "Moving %s to tried\n", addr.ToString());
// move nId to the tried tables
MakeTried(info, nId);
}
}
bool CAddrMan::Add_(const CAddress& addr, const CNetAddr& source, int64_t nTimePenalty)
@@ -521,3 +533,82 @@ void CAddrMan::SetServices_(const CService& addr, ServiceFlags nServices)
int CAddrMan::RandomInt(int nMax){
return GetRandInt(nMax);
}
void CAddrMan::ResolveCollisions_()
{
for (std::set<int>::iterator it = m_tried_collisions.begin(); it != m_tried_collisions.end();) {
int id_new = *it;
bool erase_collision = false;
// If id_new not found in mapInfo remove it from m_tried_collisions
if (mapInfo.count(id_new) != 1) {
erase_collision = true;
} else {
CAddrInfo& info_new = mapInfo[id_new];
// Which tried bucket to move the entry to.
int tried_bucket = info_new.GetTriedBucket(nKey);
int tried_bucket_pos = info_new.GetBucketPosition(nKey, false, tried_bucket);
if (!info_new.IsValid()) { // id_new may no longer map to a valid address
erase_collision = true;
} else if (vvTried[tried_bucket][tried_bucket_pos] != -1) { // The position in the tried bucket is not empty
// Get the to-be-evicted address that is being tested
int id_old = vvTried[tried_bucket][tried_bucket_pos];
CAddrInfo& info_old = mapInfo[id_old];
// Has successfully connected in last X hours
if (GetAdjustedTime() - info_old.nLastSuccess < ADDRMAN_REPLACEMENT_HOURS*(60*60)) {
erase_collision = true;
} else if (GetAdjustedTime() - info_old.nLastTry < ADDRMAN_REPLACEMENT_HOURS*(60*60)) { // attempted to connect and failed in last X hours
// Give address at least 60 seconds to successfully connect
if (GetAdjustedTime() - info_old.nLastTry > 60) {
LogPrint(BCLog::ADDRMAN, "addrman", "Swapping %s for %s in tried table\n", info_new.ToString(), info_old.ToString());
// Replaces an existing address already in the tried table with the new address
Good_(info_new, false, GetAdjustedTime());
erase_collision = true;
}
}
} else { // Collision is not actually a collision anymore
Good_(info_new, false, GetAdjustedTime());
erase_collision = true;
}
}
if (erase_collision) {
m_tried_collisions.erase(it++);
} else {
it++;
}
}
}
CAddrInfo CAddrMan::SelectTriedCollision_()
{
if (m_tried_collisions.size() == 0) return CAddrInfo();
std::set<int>::iterator it = m_tried_collisions.begin();
// Selects a random element from m_tried_collisions
std::advance(it, GetRandInt(m_tried_collisions.size()));
int id_new = *it;
// If id_new not found in mapInfo remove it from m_tried_collisions
if (mapInfo.count(id_new) != 1) {
m_tried_collisions.erase(it);
return CAddrInfo();
}
CAddrInfo& newInfo = mapInfo[id_new];
// which tried bucket to move the entry to
int tried_bucket = newInfo.GetTriedBucket(nKey);
int tried_bucket_pos = newInfo.GetBucketPosition(nKey, false, tried_bucket);
int id_old = vvTried[tried_bucket][tried_bucket_pos];
return mapInfo[id_old];
}