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Merge #17428: p2p: Try to preserve outbound block-relay-only connections during restart

Browse Source 
a490d074b3 doc: Add anchors.dat to files.md (Hennadii Stepanov)
0a85e5a7bc p2p: Try to connect to anchors once (Hennadii Stepanov)
5543c7ab28 p2p: Fix off-by-one error in fetching address loop (Hennadii Stepanov)
4170b46544 p2p: Integrate DumpAnchors() and ReadAnchors() into CConnman (Hennadii Stepanov)
bad16aff49 p2p: Add CConnman::GetCurrentBlockRelayOnlyConns() (Hennadii Stepanov)
c29272a157 p2p: Add ReadAnchors() (Hennadii Stepanov)
567008d2a0 p2p: Add DumpAnchors() (Hennadii Stepanov)

Pull request description:

  This is an implementation of #17326:
  - all (currently 2) outbound block-relay-only connections (#15759) are dumped to `anchors.dat` file
  - on restart a node tries to connect to the addresses from `anchors.dat`

  This PR prevents a type of eclipse attack when an attacker exploits a victim node restart to force it to connect to new, probably adversarial, peers.

ACKs for top commit:
  jnewbery:
    code review ACK a490d074b3
  laanwj:
    Code review ACK a490d074b3

Tree-SHA512: 0f5098a3882f2814be1aa21de308cd09e6654f4e7054b79f3cfeaf26bc02b814ca271497ed00018d199ee596a8cb9b126acee8b666a29e225b08eb2a49b02ddd
This commit is contained in:
Wladimir J. van der Laan
2020-10-15 18:33:43 +02:00
parent 0d22482353 a490d074b3
commit 9855422e65
5 changed files with 115 additions and 12 deletions
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71
src/net.cpp
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@@ -47,6 +47,12 @@ static_assert(MINIUPNPC_API_VERSION >= 10, "miniUPnPc API version >= 10 assumed"
#include <math.h>
/** Maximum number of block-relay-only anchor connections */
static constexpr size_t MAX_BLOCK_RELAY_ONLY_ANCHORS = 2;
static_assert (MAX_BLOCK_RELAY_ONLY_ANCHORS <= static_cast<size_t>(MAX_BLOCK_RELAY_ONLY_CONNECTIONS), "MAX_BLOCK_RELAY_ONLY_ANCHORS must not exceed MAX_BLOCK_RELAY_ONLY_CONNECTIONS.");
/** Anchor IP address database file name */
const char* const ANCHORS_DATABASE_FILENAME = "anchors.dat";
// How often to dump addresses to peers.dat
static constexpr std::chrono::minutes DUMP_PEERS_INTERVAL{15};
@@ -1933,10 +1939,12 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
ConnectionType conn_type = ConnectionType::OUTBOUND_FULL_RELAY;
int64_t nTime = GetTimeMicros();
bool anchor = false;
bool fFeeler = false;
// Determine what type of connection to open. Opening
// OUTBOUND_FULL_RELAY connections gets the highest priority until we
// BLOCK_RELAY connections to addresses from anchors.dat gets the highest
// priority. Then we open OUTBOUND_FULL_RELAY priority until we
// meet our full-relay capacity. Then we open BLOCK_RELAY connection
// until we hit our block-relay-only peer limit.
// GetTryNewOutboundPeer() gets set when a stale tip is detected, so we
@@ -1944,7 +1952,10 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
// these conditions are met, check the nNextFeeler timer to decide if
// we should open a FEELER.
if (nOutboundFullRelay < m_max_outbound_full_relay) {
if (!m_anchors.empty() && (nOutboundBlockRelay < m_max_outbound_block_relay)) {
conn_type = ConnectionType::BLOCK_RELAY;
anchor = true;
} else if (nOutboundFullRelay < m_max_outbound_full_relay) {
// OUTBOUND_FULL_RELAY
} else if (nOutboundBlockRelay < m_max_outbound_block_relay) {
conn_type = ConnectionType::BLOCK_RELAY;
@@ -1965,6 +1976,24 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
int nTries = 0;
while (!interruptNet)
{
if (anchor && !m_anchors.empty()) {
const CAddress addr = m_anchors.back();
m_anchors.pop_back();
if (!addr.IsValid() || IsLocal(addr) || !IsReachable(addr) ||
!HasAllDesirableServiceFlags(addr.nServices) ||
setConnected.count(addr.GetGroup(addrman.m_asmap))) continue;
addrConnect = addr;
LogPrint(BCLog::NET, "Trying to make an anchor connection to %s\n", addrConnect.ToString());
break;
}
// If we didn't find an appropriate destination after trying 100 addresses fetched from addrman,
// stop this loop, and let the outer loop run again (which sleeps, adds seed nodes, recalculates
// already-connected network ranges, ...) before trying new addrman addresses.
nTries++;
if (nTries > 100)
break;
CAddrInfo addr = addrman.SelectTriedCollision();
// SelectTriedCollision returns an invalid address if it is empty.
@@ -1982,13 +2011,6 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
break;
}
// If we didn't find an appropriate destination after trying 100 addresses fetched from addrman,
// stop this loop, and let the outer loop run again (which sleeps, adds seed nodes, recalculates
// already-connected network ranges, ...) before trying new addrman addresses.
nTries++;
if (nTries > 100)
break;
if (!IsReachable(addr))
continue;
@@ -2028,6 +2050,19 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
}
}
std::vector<CAddress> CConnman::GetCurrentBlockRelayOnlyConns() const
{
std::vector<CAddress> ret;
LOCK(cs_vNodes);
for (const CNode* pnode : vNodes) {
if (pnode->IsBlockOnlyConn()) {
ret.push_back(pnode->addr);
}
}
return ret;
}
std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo()
{
std::vector<AddedNodeInfo> ret;
@@ -2427,6 +2462,15 @@ bool CConnman::Start(CScheduler& scheduler, const Options& connOptions)
}
}
if (m_use_addrman_outgoing) {
// Load addresses from anchors.dat
m_anchors = ReadAnchors(GetDataDir() / ANCHORS_DATABASE_FILENAME);
if (m_anchors.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
m_anchors.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
}
LogPrintf("%i block-relay-only anchors will be tried for connections.\n", m_anchors.size());
}
uiInterface.InitMessage(_("Starting network threads...").translated);
fAddressesInitialized = true;
@@ -2542,6 +2586,15 @@ void CConnman::StopNodes()
if (fAddressesInitialized) {
DumpAddresses();
fAddressesInitialized = false;
if (m_use_addrman_outgoing) {
// Anchor connections are only dumped during clean shutdown.
std::vector<CAddress> anchors_to_dump = GetCurrentBlockRelayOnlyConns();
if (anchors_to_dump.size() > MAX_BLOCK_RELAY_ONLY_ANCHORS) {
anchors_to_dump.resize(MAX_BLOCK_RELAY_ONLY_ANCHORS);
}
DumpAnchors(GetDataDir() / ANCHORS_DATABASE_FILENAME, anchors_to_dump);
}
}
// Close sockets