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CAddrMan: stochastic address manager
Design goals: * Only keep a limited number of addresses around, so that addr.dat does not grow without bound. * Keep the address tables in-memory, and occasionally write the table to addr.dat. * Make sure no (localized) attacker can fill the entire table with his nodes/addresses. See comments in addrman.h for more detailed information.
This commit is contained in:
Pieter Wuille
499
src/addrman.h
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499
src/addrman.h
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@@ -0,0 +1,499 @@
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// Copyright (c) 2012 Pieter Wuille
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// Distributed under the MIT/X11 software license, see the accompanying
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// file license.txt or http://www.opensource.org/licenses/mit-license.php.
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#ifndef _BITCOIN_ADDRMAN
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#define _BITCOIN_ADDRMAN 1
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#include "netbase.h"
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#include "protocol.h"
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#include "util.h"
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#include <map>
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#include <vector>
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#include <openssl/rand.h>
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// Extended statistics about a CAddress
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class CAddrInfo : public CAddress
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{
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private:
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// where knowledge about this address first came from
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CNetAddr source;
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// last succesfull connection by us
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int64 nLastSuccess;
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// last try whatsoever by us:
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// int64 CAddress::nLastTry
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// connection attempts since last succesful attempt
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int nAttempts;
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// reference count in new sets (memory only)
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int nRefCount;
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// in tried set? (memory only)
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bool fInTried;
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// position in vRandom
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int nRandomPos;
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friend class CAddrMan;
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public:
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IMPLEMENT_SERIALIZE(
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CAddress* pthis = (CAddress*)(this);
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READWRITE(*pthis);
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READWRITE(source);
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READWRITE(nLastSuccess);
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READWRITE(nAttempts);
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)
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void Init()
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{
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nLastSuccess = 0;
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nLastTry = 0;
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nAttempts = 0;
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nRefCount = 0;
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fInTried = false;
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nRandomPos = -1;
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}
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CAddrInfo(const CAddress &addrIn, const CNetAddr &addrSource) : CAddress(addrIn)
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{
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Init();
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}
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CAddrInfo() : CAddress(), source()
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{
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Init();
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}
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// Calculate in which "tried" bucket this entry belongs
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int GetTriedBucket(const std::vector<unsigned char> &nKey) const;
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// Calculate in which "new" bucket this entry belongs, given a certain source
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int GetNewBucket(const std::vector<unsigned char> &nKey, const CNetAddr& src) const;
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// Calculate in which "new" bucket this entry belongs, using its default source
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int GetNewBucket(const std::vector<unsigned char> &nKey) const
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{
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return GetNewBucket(nKey, source);
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}
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// Determine whether the statistics about this entry are bad enough so that it can just be deleted
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bool IsTerrible(int64 nNow = GetAdjustedTime()) const;
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// Calculate the relative chance this entry should be given when selecting nodes to connect to
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double GetChance(int64 nNow = GetAdjustedTime()) const;
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};
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// Stochastic address manager
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//
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// Design goals:
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// * Only keep a limited number of addresses around, so that addr.dat and memory requirements do not grow without bound.
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// * Keep the address tables in-memory, and asynchronously dump the entire to able in addr.dat.
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// * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.
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//
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// To that end:
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// * Addresses are organized into buckets.
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// * Address that have not yet been tried go into 256 "new" buckets.
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// * Based on the address range (/16 for IPv4) of source of the information, 32 buckets are selected at random
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// * The actual bucket is chosen from one of these, based on the range the address itself is located.
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// * One single address can occur in up to 4 different buckets, to increase selection chances for addresses that
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// are seen frequently. The chance for increasing this multiplicity decreases exponentially.
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// * When adding a new address to a full bucket, a randomly chosen entry (with a bias favoring less recently seen
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// ones) is removed from it first.
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// * Addresses of nodes that are known to be accessible go into 64 "tried" buckets.
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// * Each address range selects at random 4 of these buckets.
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// * The actual bucket is chosen from one of these, based on the full address.
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// * When adding a new good address to a full bucket, a randomly chosen entry (with a bias favoring less recently
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// tried ones) is evicted from it, back to the "new" buckets.
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// * Bucket selection is based on cryptographic hashing, using a randomly-generated 256-bit key, which should not
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// be observable by adversaries.
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// * Several indexes are kept for high performance. Defining DEBUG_ADDRMAN will introduce frequent (and expensive)
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// consistency checks for the entire datastructure.
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// total number of buckets for tried addresses
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#define ADDRMAN_TRIED_BUCKET_COUNT 64
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// maximum allowed number of entries in buckets for tried addresses
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#define ADDRMAN_TRIED_BUCKET_SIZE 64
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// total number of buckets for new addresses
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#define ADDRMAN_NEW_BUCKET_COUNT 256
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// maximum allowed number of entries in buckets for new addresses
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#define ADDRMAN_NEW_BUCKET_SIZE 64
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// over how many buckets entries with tried addresses from a single group (/16 for IPv4) are spread
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#define ADDRMAN_TRIED_BUCKETS_PER_GROUP 4
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// over how many buckets entries with new addresses originating from a single group are spread
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#define ADDRMAN_NEW_BUCKETS_PER_SOURCE_GROUP 32
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// in how many buckets for entries with new addresses a single address may occur
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#define ADDRMAN_NEW_BUCKETS_PER_ADDRESS 4
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// how many entries in a bucket with tried addresses are inspected, when selecting one to replace
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#define ADDRMAN_TRIED_ENTRIES_INSPECT_ON_EVICT 4
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// how old addresses can maximally be
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#define ADDRMAN_HORIZON_DAYS 30
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// after how many failed attempts we give up on a new node
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#define ADDRMAN_RETRIES 3
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// how many successive failures are allowed ...
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#define ADDRMAN_MAX_FAILURES 10
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// ... in at least this many days
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#define ADDRMAN_MIN_FAIL_DAYS 7
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// the maximum percentage of nodes to return in a getaddr call
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#define ADDRMAN_GETADDR_MAX_PCT 23
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// the maximum number of nodes to return in a getaddr call
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#define ADDRMAN_GETADDR_MAX 2500
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class CAddrMan
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{
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private:
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// critical section to protect the inner data structures
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mutable CCriticalSection cs;
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// secret key to randomize bucket select with
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std::vector<unsigned char> nKey;
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// last used nId
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int nIdCount;
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// table with information about all nId's
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std::map<int, CAddrInfo> mapInfo;
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// find an nId based on its network address
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std::map<CNetAddr, int> mapAddr;
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// randomly-ordered vector of all nId's
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std::vector<int> vRandom;
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// number of "tried" entries
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int nTried;
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// list of "tried" buckets
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std::vector<std::vector<int> > vvTried;
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// number of (unique) "new" entries
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int nNew;
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// list of "new" buckets
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std::vector<std::set<int> > vvNew;
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protected:
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// Find an entry.
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CAddrInfo* Find(const CNetAddr& addr, int *pnId = NULL);
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// find an entry, creating it if necessary.
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// nTime and nServices of found node is updated, if necessary.
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CAddrInfo* Create(const CAddress &addr, const CNetAddr &addrSource, int *pnId = NULL);
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// Swap two elements in vRandom.
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void SwapRandom(int nRandomPos1, int nRandomPos2);
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// Return position in given bucket to replace.
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int SelectTried(int nKBucket);
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// Remove an element from a "new" bucket.
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// This is the only place where actual deletes occur.
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// They are never deleted while in the "tried" table, only possibly evicted back to the "new" table.
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int ShrinkNew(int nUBucket);
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// Move an entry from the "new" table(s) to the "tried" table
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// @pre vvUnkown[nOrigin].count(nId) != 0
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void MakeTried(CAddrInfo& info, int nId, int nOrigin);
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// Mark an entry "good", possibly moving it from "new" to "tried".
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void Good_(const CService &addr, int64 nTime);
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// Add an entry to the "new" table.
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bool Add_(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty);
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// Mark an entry as attempted to connect.
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void Attempt_(const CService &addr, int64 nTime);
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// Select an address to connect to.
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// nUnkBias determines how much to favor new addresses over tried ones (min=0, max=100)
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CAddress Select_(int nUnkBias);
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#ifdef DEBUG_ADDRMAN
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// Perform consistency check. Returns an error code or zero.
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int Check_();
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#endif
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// Select several addresses at once.
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void GetAddr_(std::vector<CAddress> &vAddr);
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// Mark an entry as currently-connected-to.
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void Connected_(const CService &addr, int64 nTime);
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public:
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IMPLEMENT_SERIALIZE
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(({
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// serialized format:
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// * version byte (currently 0)
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// * nKey
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// * nNew
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// * nTried
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// * number of "new" buckets
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// * all nNew addrinfo's in vvNew
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// * all nTried addrinfo's in vvTried
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// * for each bucket:
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// * number of elements
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// * for each element: index
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//
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// Notice that vvTried, mapAddr and vVector are never encoded explicitly;
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// they are instead reconstructed from the other information.
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//
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// vvNew is serialized, but only used if ADDRMAN_UNKOWN_BUCKET_COUNT didn't change,
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// otherwise it is reconstructed as well.
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//
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// This format is more complex, but significantly smaller (at most 1.5 MiB), and supports
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// changes to the ADDRMAN_ parameters without breaking the on-disk structure.
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CRITICAL_BLOCK(cs)
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{
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unsigned char nVersion = 0;
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READWRITE(nVersion);
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READWRITE(nKey);
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READWRITE(nNew);
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READWRITE(nTried);
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CAddrMan *am = const_cast<CAddrMan*>(this);
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if (fWrite)
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{
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int nUBuckets = ADDRMAN_NEW_BUCKET_COUNT;
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READWRITE(nUBuckets);
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std::map<int, int> mapUnkIds;
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int nIds = 0;
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for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
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{
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if (nIds == nNew) break; // this means nNew was wrong, oh ow
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mapUnkIds[(*it).first] = nIds;
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CAddrInfo &info = (*it).second;
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if (info.nRefCount)
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{
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READWRITE(info);
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nIds++;
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}
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}
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nIds = 0;
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for (std::map<int, CAddrInfo>::iterator it = am->mapInfo.begin(); it != am->mapInfo.end(); it++)
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{
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if (nIds == nTried) break; // this means nTried was wrong, oh ow
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CAddrInfo &info = (*it).second;
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if (info.fInTried)
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{
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READWRITE(info);
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nIds++;
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}
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}
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for (std::vector<std::set<int> >::iterator it = am->vvNew.begin(); it != am->vvNew.end(); it++)
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{
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const std::set<int> &vNew = (*it);
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int nSize = vNew.size();
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READWRITE(nSize);
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for (std::set<int>::iterator it2 = vNew.begin(); it2 != vNew.end(); it2++)
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{
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int nIndex = mapUnkIds[*it2];
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READWRITE(nIndex);
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}
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}
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} else {
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int nUBuckets = 0;
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READWRITE(nUBuckets);
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am->nIdCount = 0;
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am->mapInfo.clear();
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am->mapAddr.clear();
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am->vRandom.clear();
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am->vvTried = std::vector<std::vector<int> >(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0));
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am->vvNew = std::vector<std::set<int> >(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>());
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for (int n = 0; n < am->nNew; n++)
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{
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CAddrInfo &info = am->mapInfo[n];
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READWRITE(info);
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am->mapAddr[info] = n;
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info.nRandomPos = vRandom.size();
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am->vRandom.push_back(n);
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if (nUBuckets != ADDRMAN_NEW_BUCKET_COUNT)
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{
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am->vvNew[info.GetNewBucket(am->nKey)].insert(n);
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info.nRefCount++;
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}
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}
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am->nIdCount = am->nNew;
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int nLost = 0;
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for (int n = 0; n < am->nTried; n++)
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{
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CAddrInfo info;
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READWRITE(info);
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std::vector<int> &vTried = am->vvTried[info.GetTriedBucket(am->nKey)];
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if (vTried.size() < ADDRMAN_TRIED_BUCKET_SIZE)
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{
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info.nRandomPos = vRandom.size();
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info.fInTried = true;
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am->vRandom.push_back(am->nIdCount);
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am->mapInfo[am->nIdCount] = info;
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am->mapAddr[info] = am->nIdCount;
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vTried.push_back(am->nIdCount);
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am->nIdCount++;
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} else {
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nLost++;
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}
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}
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am->nTried -= nLost;
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for (int b = 0; b < nUBuckets; b++)
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{
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std::set<int> &vNew = am->vvNew[b];
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int nSize = 0;
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READWRITE(nSize);
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for (int n = 0; n < nSize; n++)
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{
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int nIndex = 0;
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READWRITE(nIndex);
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CAddrInfo &info = am->mapInfo[nIndex];
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if (nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS)
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{
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info.nRefCount++;
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vNew.insert(nIndex);
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}
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}
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}
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}
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}
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});)
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CAddrMan() : vRandom(0), vvTried(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0)), vvNew(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>())
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{
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nKey.resize(32);
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RAND_bytes(&nKey[0], 32);
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nIdCount = 0;
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nTried = 0;
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nNew = 0;
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}
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// Return the number of (unique) addresses in all tables.
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int size()
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{
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return vRandom.size();
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}
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// Consistency check
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void Check()
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{
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#ifdef DEBUG_ADDRMAN
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CRITICAL_BLOCK(cs)
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{
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int err;
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if ((err=Check_()))
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printf("ADDRMAN CONSISTENCY CHECK FAILED!!! err=%i\n", err);
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}
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#endif
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}
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// Add a single address.
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bool Add(const CAddress &addr, const CNetAddr& source, int64 nTimePenalty = 0)
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{
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bool fRet = false;
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CRITICAL_BLOCK(cs)
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{
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Check();
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fRet |= Add_(addr, source, nTimePenalty);
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Check();
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}
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if (fRet)
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printf("Added %s from %s: %i tried, %i new\n", addr.ToStringIPPort().c_str(), source.ToString().c_str(), nTried, nNew);
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return fRet;
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}
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// Add multiple addresses.
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bool Add(const std::vector<CAddress> &vAddr, const CNetAddr& source, int64 nTimePenalty = 0)
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{
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int nAdd = 0;
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CRITICAL_BLOCK(cs)
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{
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Check();
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for (std::vector<CAddress>::const_iterator it = vAddr.begin(); it != vAddr.end(); it++)
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nAdd += Add_(*it, source, nTimePenalty) ? 1 : 0;
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Check();
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}
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if (nAdd)
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printf("Added %i addresses from %s: %i tried, %i new\n", nAdd, source.ToString().c_str(), nTried, nNew);
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return nAdd > 0;
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}
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// Mark an entry as accessible.
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void Good(const CService &addr, int64 nTime = GetAdjustedTime())
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{
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CRITICAL_BLOCK(cs)
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{
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Check();
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Good_(addr, nTime);
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Check();
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}
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}
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// Mark an entry as connection attempted to.
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void Attempt(const CService &addr, int64 nTime = GetAdjustedTime())
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{
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CRITICAL_BLOCK(cs)
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{
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Check();
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Attempt_(addr, nTime);
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Check();
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}
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}
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// Choose an address to connect to.
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// nUnkBias determines how much "new" entries are favored over "tried" ones (0-100).
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CAddress Select(int nUnkBias = 50)
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{
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CAddress addrRet;
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CRITICAL_BLOCK(cs)
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{
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Check();
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addrRet = Select_(nUnkBias);
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Check();
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||||
}
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return addrRet;
|
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}
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// Return a bunch of addresses, selected at random.
|
||||
std::vector<CAddress> GetAddr()
|
||||
{
|
||||
Check();
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||||
std::vector<CAddress> vAddr;
|
||||
CRITICAL_BLOCK(cs)
|
||||
GetAddr_(vAddr);
|
||||
Check();
|
||||
return vAddr;
|
||||
}
|
||||
|
||||
// Mark an entry as currently-connected-to.
|
||||
void Connected(const CService &addr, int64 nTime = GetAdjustedTime())
|
||||
{
|
||||
CRITICAL_BLOCK(cs)
|
||||
{
|
||||
Check();
|
||||
Connected_(addr, nTime);
|
||||
Check();
|
||||
}
|
||||
}
|
||||
};
|
||||
|
||||
#endif
|
||||
Reference in New Issue
Block a user