Linux下电骡aMule Kademlia网络构建分析4
aMule中联系人的管理
aMule中主要通过CContact，CRoutingBin和CRoutingZone这样几个类来管理它的联系人。
CContact表示一个联系人，它包含了与一个联系人有关的所有的信息，这个类的对象可能是根据从文件中读出来的信息创建的，也可能是根据其它节点发送的连接请求中的信息创建的。
CRoutingBin是CContact的容器，保存了一组CContact，也就是一个Zone的联系人。
CRoutingZone是aMule中管理联系人的核心。aMule用CRoutingZone将它的所有联系人组织为一颗二叉树。
aMule联系人的表示CContact
先来简单的看一下aMule中的联系人的表示CContact类。这个类在amule-2.3.1/src/kademlia/routing/Contact.h文件中定义：
class CContact
{
public:
~CContact();
CContact(const CUInt128 &clientID,
uint32_t ip, uint16_t udpPort, uint16_t tcpPort, uint8_t version,
const CKadUDPKey& kadKey, bool ipVerified,
const CUInt128 &target = CKademlia::GetPrefs()->GetKadID());
CContact(const CContact& k1);
const CUInt128& GetClientID() const throw() { return m_clientID; }
void SetClientID(const CUInt128& clientID) throw() { m_clientID = clientID; m_distance = CKademlia::GetPrefs()->GetKadID() ^ clientID; }
const wxString GetClientIDString() const { return m_clientID.ToHexString(); }
const CUInt128& GetDistance() const throw() { return m_distance; }
const wxString GetDistanceString() const { return m_distance.ToBinaryString(); }
uint32_t GetIPAddress() const throw() { return m_ip; }
void SetIPAddress(uint32_t ip) throw() { if (m_ip != ip) { SetIPVerified(false); m_ip = ip; } }
uint16_t GetTCPPort() const throw() { return m_tcpPort; }
void SetTCPPort(uint16_t port) throw() { m_tcpPort = port; }
uint16_t GetUDPPort() const throw() { return m_udpPort; }
void SetUDPPort(uint16_t port) throw() { m_udpPort = port; }
uint8_t GetType() const throw() { return m_type; }
void UpdateType() throw();
void CheckingType() throw();
bool InUse() const throw() { return m_inUse > 0; }
void IncUse() throw() { m_inUse++; }
void DecUse() { if (m_inUse) m_inUse--; else { wxFAIL; } }
time_t GetCreatedTime() const throw() { return m_created; }
void SetExpireTime(time_t value) throw() { m_expires = value; };
time_t GetExpireTime() const throw() { return m_expires; }
time_t GetLastTypeSet() const throw() { return m_lastTypeSet; }
time_t GetLastSeen() const throw();
uint8_t GetVersion() const throw() { return m_version; }
void SetVersion(uint8_t value) throw() { m_version = value; }
const CKadUDPKey& GetUDPKey() const throw() { return m_udpKey; }
void SetUDPKey(const CKadUDPKey& key) throw() { m_udpKey = key; }
bool IsIPVerified() const throw() { return m_ipVerified; }
void SetIPVerified(bool ipVerified) throw() { m_ipVerified = ipVerified; }
bool GetReceivedHelloPacket() const throw() { return m_receivedHelloPacket; }
void SetReceivedHelloPacket() throw() { m_receivedHelloPacket = true; }
private:
CUInt128 m_clientID;
CUInt128 m_distance;
uint32_t m_ip;
uint16_t m_tcpPort;
uint16_t m_udpPort;
uint8_t m_type;
time_t m_lastTypeSet;
time_t m_expires;
time_t m_created;
uint32_t m_inUse;
uint8_t m_version;
bool m_ipVerified;
bool m_receivedHelloPacket;
CKadUDPKey m_udpKey;
};
我们主要关注这个类所具有的成员变量，以便于了解在aMule中，它会管理联系人的哪些信息。可以看到有ip地址，clientID，client的TCP端口号，client的UDP端口好，版本号等静态信息，以及对象创建时间，对象的有效期等动态的信息。
注意CContact构造函数的声明，target参数的默认值为本节点KadID。
再来看一下这个class的成员函数的实现：
CContact::~CContact()
{
theStats::RemoveKadNode();
}
CContact::CContact(const CUInt128 &clientID, uint32_t ip, uint16_t udpPort, uint16_t tcpPort, uint8_t version, const CKadUDPKey& key, bool ipVerified, const CUInt128 &target)
: m_clientID(clientID),
m_distance(target ^ clientID),
m_ip(ip),
m_tcpPort(tcpPort),
m_udpPort(udpPort),
m_type(3),
m_lastTypeSet(time(NULL)),
m_expires(0),
m_created(m_lastTypeSet),
m_inUse(0),
m_version(version),
m_ipVerified(ipVerified),
m_receivedHelloPacket(false),
m_udpKey(key)
{
wxASSERT(udpPort);
theStats::AddKadNode();
}
CContact::CContact(const CContact& k1)
{
*this = k1;
theStats::AddKadNode();
}
void CContact::CheckingType() throw()
{
time_t now = time(NULL);
if(now - m_lastTypeSet < 10 || m_type == 4) {
return;
}
m_lastTypeSet = now;
m_expires = now + MIN2S(2);
m_type++;
}
void CContact::UpdateType() throw()
{
time_t now = time(NULL);
uint32_t hours = (now - m_created) / HR2S(1);
switch (hours) {
case 0:
m_type = 2;
m_expires = now + HR2S(1);
break;
case 1:
m_type = 1;
m_expires = now + MIN2S(90); //HR2S(1.5)
break;
default:
m_type = 0;
m_expires = now + HR2S(2);
}
}
time_t CContact::GetLastSeen() const throw()
{
// calculating back from expire time, so we don't need an additional field.
// might result in wrong values if doing CheckingType() for example, so don't use for important timing stuff
if (m_expires != 0) {
switch (m_type) {
case 2: return m_expires - HR2S(1);
case 1: return m_expires - MIN2S(90) /*(unsigned)HR2S(1.5)*/;
case 0: return m_expires - HR2S(2);
}
}
return 0;
}
这里主要关注CContact的构造函数。可以看到，m_distance被初始化为clientID和target的异或。如前面CContact构造函数的声明，则m_distance默认情况下将是clientID和本节点的KadID的异或。m_lastTypeSet和m_created被设置为了当前时间，m_expires节点有效期则被设置为了0。
跟type有关的数字，全用的是magic number，这code好烂。
CRoutingZone的构造
接着来看，CContact的二叉树是如何被一步步构造出来的。
先来看一下CRoutingZone都有哪写成员变量：
time_t m_nextBigTimer; time_t m_nextSmallTimer; /** * Zone pair is an array of two. Either both entries are null, which * means that *this* is a leaf zone, or both are non-null which means * that *this* has been split into equally sized finer zones. * The zone with index 0 is the one closer to our *self* token. */ CRoutingZone *m_subZones[2]; CRoutingZone *m_superZone; static wxString m_filename; static CUInt128 me; /** * The level indicates what size chunk of the address space * this zone is representing. Level 0 is the whole space, * level 1 is 1/2 of the space, level 2 is 1/4, etc. */ uint32_t m_level; /** * This is the distance in number of zones from the zone at this level * that contains the center of the system; distance is wrt the XOR metric. */ CUInt128 m_zoneIndex; /** List of contacts, if this zone is a leaf zone. */ CRoutingBin *m_bin; };
m_subZones和m_superZone是构造二叉树所必须的结构，m_subZones[0]指向子树0，m_subZones[1]指向子树1，而m_superZone则指向树中本节点的父节点。
m_bin是本CRoutingZone的CRoutingBin，如我们在本文最开头所述，这是CContact的容器，用来保存CContact，如果当前CRoutingZone不是叶子节点的话，则这个变量将为NULL。
m_level表示当前CRoutingZone在二叉树中的层次，最顶层的CRoutingZone该值为0，子CRoutingZone的m_level值是其父CRoutingZone的m_level值加一。此外，如注释中所述的那样，这个值指示了当前zone表示的地址空间的块大小。Level 0是整个空间，Level 1是1/2个空间，Level 2是1/4个，等等等等，依次类推。
回想 Linux下电骡aMule Kademlia网络构建分析I 一文中，我们有看到，CRoutingZone::ReadFile()函数在读取了文件中的联系人信息之后，会调用AddUnfiltered()将一个联系人添加到CRoutingZone中。这里我们就来仔仔细细地看一下，CContact的添加过程(amule-2.3.1/src/kademlia/routing/RoutingZone.cpp)：
// Returns true if a contact was added or updated, false if the routing table was not touched.
bool CRoutingZone::AddUnfiltered(const CUInt128& id, uint32_t ip, uint16_t port, uint16_t tport, uint8_t version, const CKadUDPKey& key, bool& ipVerified, bool update, bool fromHello)
{
if (id != me) {
CContact *contact = new CContact(id, ip, port, tport, version, key, ipVerified);
if (fromHello) {
contact->SetReceivedHelloPacket();
}
if (Add(contact, update, ipVerified)) {
wxASSERT(!update);
return true;
} else {
delete contact;
return update;
}
}
return false;
}
在这个函数里，会首先创建一个CContact，如果节点信息来自于一个连接建立请求的Hello消息，则设置ReceivedHelloPacket，然后调用CRoutingZone::Add()函数向RoutingZone中添加节点：
bool CRoutingZone::Add(CContact *contact, bool& update, bool& outIpVerified)
{
// If we're not a leaf, call add on the correct branch.
if (!IsLeaf()) {
return m_subZones[contact->GetDistance().GetBitNumber(m_level)]->Add(contact, update, outIpVerified);
} else {
// Do we already have a contact with this KadID?
CContact *contactUpdate = m_bin->GetContact(contact->GetClientID());
if (contactUpdate) {
if (update) {
if (contactUpdate->GetUDPKey().GetKeyValue(theApp->GetPublicIP(false)) != 0 && contactUpdate->GetUDPKey().GetKeyValue(theApp->GetPublicIP(false)) != contact->GetUDPKey().GetKeyValue(theApp->GetPublicIP(false))) {
// if our existing contact has a UDPSender-Key (which should be the case for all > = 0.49a clients)
// except if our IP has changed recently, we demand that the key is the same as the key we received
// from the packet which wants to update this contact in order to make sure this is not a try to
// hijack this entry
AddDebugLogLineN(logKadRouting, wxT("Sender (") + KadIPToString(contact->GetIPAddress()) + wxT(") tried to update contact entry but failed to provide the proper sender key (Sent Empty: ") + (contact->GetUDPKey().GetKeyValue(theApp->GetPublicIP(false)) == 0 ? wxT("Yes") : wxT("No")) + wxT(") for the entry (") + KadIPToString(contactUpdate->GetIPAddress()) + wxT(") - denying update"));
update = false;
} else if (contactUpdate->GetVersion() >= 1 && contactUpdate->GetVersion() < 6 && contactUpdate->GetReceivedHelloPacket()) {
// legacy kad2 contacts are allowed only to update their RefreshTimer to avoid having them hijacked/corrupted by an attacker
// (kad1 contacts do not have this restriction as they might turn out as kad2 later on)
// only exception is if we didn't received a HELLO packet from this client yet
if (contactUpdate->GetIPAddress() == contact->GetIPAddress() && contactUpdate->GetTCPPort() == contact->GetTCPPort() && contactUpdate->GetVersion() == contact->GetVersion() && contactUpdate->GetUDPPort() == contact->GetUDPPort()) {
wxASSERT(!contact->IsIPVerified()); // legacy kad2 nodes should be unable to verify their IP on a HELLO
outIpVerified = contactUpdate->IsIPVerified();
m_bin->SetAlive(contactUpdate);
AddDebugLogLineN(logKadRouting, CFormat(wxT("Updated kad contact refreshtimer only for legacy kad2 contact (%s, %u)")) % KadIPToString(contactUpdate->GetIPAddress()) % contactUpdate->GetVersion());
} else {
AddDebugLogLineN(logKadRouting, CFormat(wxT("Rejected value update for legacy kad2 contact (%s -> %s, %u -> %u)"))
% KadIPToString(contactUpdate->GetIPAddress()) % KadIPToString(contact->GetIPAddress()) % contactUpdate->GetVersion() % contact->GetVersion());
update = false;
}
} else {
#ifdef __DEBUG__
// just for outlining, get removed anyway
//debug logging stuff - remove later
if (contact->GetUDPKey().GetKeyValue(theApp->GetPublicIP(false)) == 0) {
if (contact->GetVersion() >= 6 && contact->GetType() < 2) {
AddDebugLogLineN(logKadRouting, wxT("Updating > 0.49a + type < 2 contact without valid key stored ") + KadIPToString(contact->GetIPAddress()));
}
} else {
AddDebugLogLineN(logKadRouting, wxT("Updating contact, passed key check ") + KadIPToString(contact->GetIPAddress()));
}
if (contactUpdate->GetVersion() >= 1 && contactUpdate->GetVersion() < 6) {
wxASSERT(!contactUpdate->GetReceivedHelloPacket());
AddDebugLogLineN(logKadRouting, CFormat(wxT("Accepted update for legacy kad2 contact, because of first HELLO (%s -> %s, %u -> %u)"))
% KadIPToString(contactUpdate->GetIPAddress()) % KadIPToString(contact->GetIPAddress()) % contactUpdate->GetVersion() % contact->GetVersion());
}
#endif
// All other nodes (Kad1, Kad2 > 0.49a with UDPKey checked or not set, first hello updates) are allowed to do full updates
// do not let Kad1 responses overwrite Kad2 ones
if (m_bin->ChangeContactIPAddress(contactUpdate, contact->GetIPAddress()) && contact->GetVersion() >= contactUpdate->GetVersion()) {
contactUpdate->SetUDPPort(contact->GetUDPPort());
contactUpdate->SetTCPPort(contact->GetTCPPort());
contactUpdate->SetVersion(contact->GetVersion());
contactUpdate->SetUDPKey(contact->GetUDPKey());
// don't unset the verified flag (will clear itself on ipchanges)
if (!contactUpdate->IsIPVerified()) {
contactUpdate->SetIPVerified(contact->IsIPVerified());
}
outIpVerified = contactUpdate->IsIPVerified();
m_bin->SetAlive(contactUpdate);
if (contact->GetReceivedHelloPacket()) {
contactUpdate->SetReceivedHelloPacket();
}
} else {
update = false;
}
}
}
return false;
} else if (m_bin->GetRemaining()) {
update = false;
// This bin is not full, so add the new contact
return m_bin->AddContact(contact);
} else if (CanSplit()) {
// This bin was full and split, call add on the correct branch.
Split();
return m_subZones[contact->GetDistance().GetBitNumber(m_level)]->Add(contact, update, outIpVerified);
} else {
update = false;
return false;
}
}
}
这个函数在添加节点时，主要分为以下的几种情况来处理：
1. 当前的这个RoutingZone不是二叉树的一个叶子节点。若当前的这个RoutingZone不是二叉树的一个叶子节点，则把contact加入到子树中。那究竟要将contact添加进0和1两个子树中的哪一个呢？这主要由contact的m_distance，对应于当前层的那一位上的值决定。(contact的m_distance通常是contact与本Kademlia节点KadID的异或值。)
amule-2.3.1/src/kademlia/utils/UInt128.h：
/** Bit at level 0 being most significant. */
unsigned GetBitNumber(unsigned bit) const throw()
{
return bit <= 127 ? (m_data[bit / 32] >> (31 - (bit % 32))) & 1 : 0;
}
比如当前为第0层，如果m_distance的第0位上是0，则节点将被放进当前RoutingZone的子树0中，若为1，则将被放入当前RoutingZone的子树1中。
这个地方还可以再看一下，UInt128的第n位的含义，0～31位存放于m_data[0]，32～63位存放于m_data[1]，其它各位存放的m_data index依此类推。
m_data[0]的最高位，也就是第31位为UInt128的第0位，m_data[0]的第30位为UInt128的第1位，UInt128的其它各位存放的位置依此类推。
2. 当前的RoutingZone为叶子节点，但其m_bin中已经有了clientID与要加入的contact的clientID相同的contact。如果是这种情况，则将更新原contact的信息。
3. 当前的RoutingZone为叶子节点，其RoutingBin m_bin中仍然可以放下更多的contact。在这种情况下，则直接向RoutingBin中添加contact。
4. 当前的RoutingZone为叶子节点，其RoutingBin m_bin中无法放下更多的节点，但是RoutingZone可以被分割。如果是这种情况，则首先执行RoutingZone的分割，然后依照第1中情况中的规则，添加contact。
这里可以再来看一下判断RoutingZone是否可以被分割的依据：
bool CRoutingZone::CanSplit() const throw()
{
// Max levels allowed.
if (m_level >= 127) {
return false;
}
// Check if this zone is allowed to split.
return ((m_zoneIndex < KK || m_level < KBASE) && m_bin->GetSize() == K);
}
CRoutingZone::CanSplit()根据多个条件来判断一个RoutingZone是否可以被分割。
如果m_level大于等于127，也就是KadID的位长度，则直接返回不能再分割。
此外只有当前RoutingZone的RoutingBin中所包含的contact数达到上限时才有可能被分割。此上限也就是K，在amule-2.3.1/src/kademlia/kademlia/Defines.h中，我们可以看到，这个值是被定义为了10。
RoutingBin中所包含的contact数达到上限，并不是RoutingZone能够被分割的充分条件。在此之外，还需要满足两个条件中的一个：RoutingZone的层次不能太低，也就是说m_level不能太大，具体点说，就是小于KBASE，在amule-2.3.1/src/kademlia/kademlia/Defines.h中，我们可以看到，这个值是被定义为了4；或者m_zoneIndex不能太大，小于KK值，该值定义为5。
再来看下分割动作具体如何执行：
void CRoutingZone::Split()
{
StopTimer();
m_subZones[0] = GenSubZone(0);
m_subZones[1] = GenSubZone(1);
ContactList entries;
m_bin->GetEntries(&entries);
m_bin->m_dontDeleteContacts = true;
delete m_bin;
m_bin = NULL;
for (ContactList::const_iterator it = entries.begin(); it != entries.end(); ++it) {
if (!m_subZones[(*it)->GetDistance().GetBitNumber(m_level)]->m_bin->AddContact(*it)) {
delete *it;
}
}
}
。。。。。。
CRoutingZone *CRoutingZone::GenSubZone(unsigned side)
{
wxASSERT(side <= 1);
CUInt128 newIndex(m_zoneIndex);
newIndex <<= 1;
newIndex += side;
return new CRoutingZone(this, m_level + 1, newIndex);
}
void CRoutingZone::StopTimer()
{
CKademlia::RemoveEvent(this);
}
在CRoutingZone::Split()中将本RoutingZone分割为两个。
1. 它首先调用StopTimer()停掉定时器。在 Linux下电骡aMule Kademlia网络构建分析3 一文中，我们有看到在定期会被执行的CKademlia::Process()函数中，会执行RoutingZone的OnSmallTimer()等函数。此处调用StopTimer()也就是停掉这些函数的定期执行。
2. 然后两次调用GenSubZone()，创建两个子RoutingZone。对于GenSubZone()，主要看一下，RoutingZone的zoneIndex和level的计算。
3. 从RoutingBin m_bin中获取所有的contacts。然后删除m_bin。
4. 将所有的contacts依据规则添加进两个子RoutingZone中。
由前面的分析我们看到，无论是什么样的case，要实际添加contact，最终总会调到CRoutingBin::AddContact()，这里我们再来看一下这个函数的实现(amule-2.3.1/src/kademlia/routing/RoutingBin.cpp)：
bool CRoutingBin::AddContact(CContact *contact)
{
wxASSERT(contact != NULL);
uint32_t sameSubnets = 0;
// Check if we already have a contact with this ID in the list.
for (ContactList::const_iterator it = m_entries.begin(); it != m_entries.end(); ++it) {
if (contact->GetClientID() == (*it)->GetClientID()) {
return false;
}
if ((contact->GetIPAddress() & 0xFFFFFF00) == ((*it)->GetIPAddress() & 0xFFFFFF00)) {
sameSubnets++;
}
}
// Several checks to make sure that we don't store multiple contacts from the same IP or too many contacts from the same subnet
// This is supposed to add a bit of protection against several attacks and raise the resource needs (IPs) for a successful contact on the attacker side
// Such IPs are not banned from Kad, they still can index, search, etc so multiple KAD clients behind one IP still work
if (!CheckGlobalIPLimits(contact->GetIPAddress(), contact->GetUDPPort())) {
return false;
}
// no more than 2 IPs from the same /24 netmask in one bin, except if its a LANIP (if we don't accept LANIPs they already have been filtered before)
if (sameSubnets >= 2 && !::IsLanIP(wxUINT32_SWAP_ALWAYS(contact->GetIPAddress()))) {
AddDebugLogLineN(logKadRouting, wxT("Ignored kad contact (IP=") + KadIPPortToString(contact->GetIPAddress(), contact->GetUDPPort()) + wxT(") - too many contact with the same subnet in RoutingBin"));
return false;
}
// If not full, add to the end of list
if (m_entries.size() < K) {
m_entries.push_back(contact);
AdjustGlobalTracking(contact->GetIPAddress(), true);
return true;
}
return false;
}
即便是走到了CRoutingBin::AddContact()，contact也并不一定会真的被加进本节点的联系人列表中。
如上所示，在CRoutingBin::AddContact()中还是会再次进行过滤。
1. CRoutingBin::AddContact()首先会遍历已经保存的所有的contact。遍历的过程中会计算这一zone中，与所传入contact处于相同子网段内的contact的数量。同时会检查要添加的contact的clientID是否与某个已经保存了的contact的clientID相同，如果是则直接返回；如前面看到的，这种case应该在CRoutingZone::Add()中处理的。
2. 执行CheckGlobalIPLimits()对IP及UDPPort做一个检查。若检查不通过，则直接返回。
3. 确保一个RoutingBin中，来自同一个/24网络掩码内的contact IP不多于2个，除非它是一个LANIP。
4. 还要再次检查RoutingBin已经保存的contacts的数量是否超出了上限K，也就是10个。没有超出时，才会真正地添加contact。并调整GlobalTracking。
此处的CheckGlobalIPLimits()和检查LanIP的方法还是值得我们再看一下。
先来看CheckGlobalIPLimits()，其执行过程如下：
bool CRoutingBin::CheckGlobalIPLimits(uint32_t ip, uint16_t DEBUG_ONLY(port))
{
// no more than 1 KadID per IP
uint32_t sameIPCount = 0;
GlobalTrackingMap::const_iterator itIP = s_globalContactIPs.find(ip);
if (itIP != s_globalContactIPs.end()) {
sameIPCount = itIP->second;
}
if (sameIPCount >= MAX_CONTACTS_IP) {
AddDebugLogLineN(logKadRouting, wxT("Ignored kad contact (IP=") + KadIPPortToString(ip, port) + wxT(") - too many contacts with the same IP (global)"));
return false;
}
// no more than 10 IPs from the same /24 netmask global, except if its a LANIP (if we don't accept LANIPs they already have been filtered before)
uint32_t sameSubnetGlobalCount = 0;
GlobalTrackingMap::const_iterator itSubnet = s_globalContactSubnets.find(ip & 0xFFFFFF00);
if (itSubnet != s_globalContactSubnets.end()) {
sameSubnetGlobalCount = itSubnet->second;
}
if (sameSubnetGlobalCount >= MAX_CONTACTS_SUBNET && !::IsLanIP(wxUINT32_SWAP_ALWAYS(ip))) {
AddDebugLogLineN(logKadRouting, wxT("Ignored kad contact (IP=") + KadIPPortToString(ip, port) + wxT(") - too many contacts with the same subnet (global)"));
return false;
}
return true;
}
这里主要确保两个事情：
1. 在全局所有的contact中，每个IP不多于一个KadID。也就是对于一个IP而言，只能有一个contact。
2. 在全局所有的contact中，位于相同的/24子网中的contacts不多于10个，除非要加入的节点的ip是LanIP。
这个地方的检查规则与前面CRoutingBin::AddContact()的很相似，只不过这里是在全局contacts范围内。
我们可以再来看一下，在aMule中，是如何判断一个IP地址是否是LanIP的。在amule-2.3.1/src/NetworkFunctions.cpp中：
/**
* Used to store the ranges.
*/
struct IPRange
{
const wxChar *addr;
unsigned int mask;
bool isLAN;
};
const IPRange ranges[] = {
// Here is reserved blocks from RFC 3330 at http://www.rfc-editor.org/rfc/rfc3330.txt
//
//Address Block Present Use Reference
//----------------------------------------------------------------------------------
{ wxT("0.0.0.0"), 8, false }, // "This" Network [RFC1700, page 4]
{ wxT("10.0.0.0"), 8, true }, // Private-Use Networks [RFC1918]
// Acording to RFC3330, 24.* and 14.* must be parsed as normal ips.
//{ wxT("14.0.0.0"), 8, false }, // Public-Data Networks [RFC1700, page 181]
//{ wxT("24.0.0.0"), 8, false }, // Cable Television Networks --
{ wxT("39.0.0.0"), 8, false }, // Reserved but subject
// to allocation [RFC1797]
{ wxT("127.0.0.0"), 8, false }, // Loopback [RFC1700, page 5]
{ wxT("128.0.0.0"), 16, false }, // Reserved but subject
// to allocation --
{ wxT("169.254.0.0"), 16, false }, // Link Local --
{ wxT("172.16.0.0"), 12, true }, // Private-Use Networks [RFC1918]
{ wxT("191.255.0.0"), 16, false }, // Reserved but subject
// to allocation --
{ wxT("192.0.0.0"), 24, false }, // Reserved but subject
// to allocation --
{ wxT("192.0.2.0"), 24, false }, // Test-Net
{ wxT("192.88.99.0"), 24, false }, // 6to4 Relay Anycast [RFC3068]
{ wxT("192.168.0.0"), 16, true }, // Private-Use Networks [RFC1918]
{ wxT("198.18.0.0"), 15, false }, // Network Interconnect
// Device Benchmark Testing [RFC2544]
{ wxT("223.255.255.0"), 24, false }, // Reserved but subject
// to allocation --
{ wxT("224.0.0.0"), 4, false }, // Multicast [RFC3171]
{ wxT("240.0.0.0"), 4, false } // Reserved for Future Use [RFC1700, page 4]
};
struct filter_st {
uint32 addr; // Address and mask in anti-host order.
uint32 mask;
};
const unsigned int number_of_ranges = sizeof(ranges) / sizeof(IPRange);
static filter_st filters[number_of_ranges];
// This function is used to initialize the IP filter
bool SetupFilter()
{
for (unsigned int i = 0; i < number_of_ranges; ++i) {
filters[i].addr = StringIPtoUint32( ranges[i].addr );
filters[i].mask = ~wxUINT32_SWAP_ALWAYS((1 << (32 - ranges[i].mask)) - 1);
}
return true;
}
bool IsLanIP(uint32_t ip) throw()
{
for (unsigned int i = 0; i < number_of_ranges; i++) {
if (((ip ^ filters[i].addr) & filters[i].mask) == 0) {
return ranges[i].isLAN;
}
}
return false;
}
这里先是定义了一张表ranges，其中包含了RFC已有明确定义的网段，网段可能是Lan的，也可能不是。
在SetupFilter()中，会根据ranges表，构造一个filters表，主要就是将ranges表中没一个item的IP字段和mask字段做一个适当的转换，以方便查询。
判断一个ip是否是LanIP，则遍历filters表，找到该IP属于哪个网段。然后找到ranges表中的对应项，根据找到的项的属性，来确认一个IP是否是LanIP。
联系人CContact的查找
CRoutingZone提供了多种查找一个联系人的方式。可以根据contact的clientID来查找，可以根据contact的ip和端口号来查询，也可查询满足maxType和minKadVersion的随便的一个contact。
根据contact的clientID查询
根据contact的clientID查询使用CRoutingZone::GetContact(const CUInt128& id)函数，其定义如下：
CContact *CRoutingZone::GetContact(const CUInt128& id) const throw()
{
if (IsLeaf()) {
return m_bin->GetContact(id);
} else {
CUInt128 distance = CKademlia::GetPrefs()->GetKadID();
distance ^= id;
return m_subZones[distance.GetBitNumber(m_level)]->GetContact(id);
}
}
如果当前RoutingZone是叶子节点，则直接在它的RoutingBin m_bin中查找相应的contact。否则的话，就计算出要查找的contact与本节点的distance，递归地在适当的子RoutingZone中查找。
然后来看CRoutingBin::GetContact(const CUInt128 &id)，实现如下：
CContact *CRoutingBin::GetContact(const CUInt128 &id) const throw()
{
for (ContactList::const_iterator it = m_entries.begin(); it != m_entries.end(); ++it) {
if ((*it)->GetClientID() == id) {
return *it;
}
}
return NULL;
}
在这个函数中，遍历保存的所有的contact，逐个对比clientID，找出满足条件的返回给调用者。找不到时返回NULL。
根据contact的ip和端口号查询
根据contact的ip和端口号来查询使用GetContact(uint32_t ip, uint16_t port, bool tcpPort)，实现如下：
CContact *CRoutingZone::GetContact(uint32_t ip, uint16_t port, bool tcpPort) const throw()
{
if (IsLeaf()) {
return m_bin->GetContact(ip, port, tcpPort);
} else {
CContact *contact = m_subZones[0]->GetContact(ip, port, tcpPort);
return (contact != NULL) ? contact : m_subZones[1]->GetContact(ip, port, tcpPort);
}
}
同样，如果当前RoutingZone是叶子节点，则直接在它的RoutingBin m_bin中查找相应的contact。否则，就递归地查找子zone 0，如果没找到，则递归地查找子zone 1。在RoutingBin中：
CContact *CRoutingBin::GetContact(uint32_t ip, uint16_t port, bool tcpPort) const throw()
{
for (ContactList::const_iterator it = m_entries.begin(); it != m_entries.end(); ++it) {
CContact *contact = *it;
if ((contact->GetIPAddress() == ip)
&& ((!tcpPort && port == contact->GetUDPPort()) || (tcpPort && port == contact->GetTCPPort()) || port == 0)) {
return contact;
}
}
return NULL;
}
同样是遍历保存的所有的contact，查找完全满足条件者。
查询满足maxType和minKadVersion的随机contact
然后是查询满足maxType和minKadVersion的随便的一个contact，使用CRoutingZone::GetRandomContact()：
CContact *CRoutingZone::GetRandomContact(uint32_t maxType, uint32_t minKadVersion) const
{
if (IsLeaf()) {
return m_bin->GetRandomContact(maxType, minKadVersion);
} else {
unsigned zone = GetRandomUint16() & 1 /* GetRandomUint16() % 2 */;
CContact *contact = m_subZones[zone]->GetRandomContact(maxType, minKadVersion);
return (contact != NULL) ? contact : m_subZones[1 - zone]->GetRandomContact(maxType, minKadVersion);
}
}
同样，如果当前RoutingZone是叶子节点，则直接在它的RoutingBin m_bin中查找相应的contact。否则，随机地从两个子zone中选择一个递归地查找，如果没找到，则递归地查找另一个子zone。在RoutingBin中：
CContact *CRoutingBin::GetRandomContact(uint32_t maxType, uint32_t minKadVersion) const
{
if (m_entries.empty()) {
return NULL;
}
// Find contact
CContact *lastFit = NULL;
uint32_t randomStartPos = GetRandomUint16() % m_entries.size();
uint32_t index = 0;
for (ContactList::const_iterator it = m_entries.begin(); it != m_entries.end(); ++it) {
if ((*it)->GetType() <= maxType && (*it)->GetVersion() >= minKadVersion) {
if (index >= randomStartPos) {
return *it;
} else {
lastFit = *it;
}
}
index++;
}
return lastFit;
}
这段code也没有什么太特别的地方，此处不再赘述。
查找与某个contact距离最近的一组contacts
CRoutingZone还提供了GetClosestTo()函数，来查找与某个contact距离最近的一组contact。其实现逻辑如下：
void CRoutingZone::GetClosestTo(uint32_t maxType, const CUInt128& target, const CUInt128& distance, uint32_t maxRequired, ContactMap *result, bool emptyFirst, bool inUse) const
{
// If leaf zone, do it here
if (IsLeaf()) {
m_bin->GetClosestTo(maxType, target, maxRequired, result, emptyFirst, inUse);
return;
}
// otherwise, recurse in the closer-to-the-target subzone first
int closer = distance.GetBitNumber(m_level);
m_subZones[closer]->GetClosestTo(maxType, target, distance, maxRequired, result, emptyFirst, inUse);
// if still not enough tokens found, recurse in the other subzone too
if (result->size() < maxRequired) {
m_subZones[1-closer]->GetClosestTo(maxType, target, distance, maxRequired, result, false, inUse);
}
}
同样，如果当前RoutingZone是叶子节点，则直接在它的RoutingBin m_bin中查找。否则，从两个子zone中与目标client距离更近的子zone中递归地查找。如果找到的contact数量不足，则递归地查找另一个子zone。
此处还可以再看一下，在aMule的Kademlia网络中，两个节点之间的距离的语义。距离distance是通过两个Kademlia网络节点的KadID通过异或操作计算而来，KadID是一个随机的值。所以distance是在两个Kademlia节点的KadID确定之后的一个逻辑距离，而并没有实际的物理意义，比如，这个距离与实际的网络中，两个节点的物理位置毫无关系。
那根据这个distance逻辑距离，又是怎么确定远近的呢？假设本节点为S，有A、B、C三个节点，它们与S的距离分别为DA、DB、DC（算法为两个KadID的异或），将DA、DB、DC转化为数字值LA，LB、LC（算法为distance值中每个位上的值与该位的权值相乘后相加，其中位0的权值为2^127，位1的权值为2^126，位2的权值为2^125，。。。），若abs(LA-LB) < abs(LA - LC)，则认为节点A与B的距离比节点A与C的距离要近。
也可以通过CUInt128的几个比较的operator的实现来看出这一点(在amule-2.3.1/src/kademlia/utils/UInt128.h中)：
bool operator< (const CUInt128& value) const throw() {return (CompareTo(value) < 0);}
bool operator> (const CUInt128& value) const throw() {return (CompareTo(value) > 0);}
bool operator<= (const CUInt128& value) const throw() {return (CompareTo(value) <= 0);}
bool operator>= (const CUInt128& value) const throw() {return (CompareTo(value) >= 0);}
bool operator== (const CUInt128& value) const throw() {return (CompareTo(value) == 0);}
bool operator!= (const CUInt128& value) const throw() {return (CompareTo(value) != 0);}
他们都通过CompareTo()来实现比较逻辑(在amule-2.3.1/src/kademlia/utils/UInt128.cpp中)：
int CUInt128::CompareTo(const CUInt128 &other) const throw()
{
for (int i = 0; i < 4; ++i) {
if (m_data[i] < other.m_data[i])
return -1;
if (m_data[i] > other.m_data[i])
return 1;
}
return 0;
}
在RoutingBin中：
void CRoutingBin::GetClosestTo(uint32_t maxType, const CUInt128 &target, uint32_t maxRequired, ContactMap *result, bool emptyFirst, bool inUse) const
{
// Empty list if requested.
if (emptyFirst) {
result->clear();
}
// No entries, no closest.
if (m_entries.size() == 0) {
return;
}
// First put results in sort order for target so we can insert them correctly.
// We don't care about max results at this time.
for (ContactList::const_iterator it = m_entries.begin(); it != m_entries.end(); ++it) {
if ((*it)->GetType() <= maxType && (*it)->IsIPVerified()) {
CUInt128 targetDistance((*it)->GetClientID() ^ target);
(*result)[targetDistance] = *it;
// This list will be used for an unknown time, Inc in use so it's not deleted.
if (inUse) {
(*it)->IncUse();
}
}
}
// Remove any extra results by least wanted first.
while (result->size() > maxRequired) {
// Dec in use count.
if (inUse) {
(--result->end())->second->DecUse();
}
// Remove from results
result->erase(--result->end());
}
}
这里可以看一下aMule中，所谓的distance closest的语义。在这个函数中也就是找出所有的type小于maxType，同时IP被Verified的contacts。
如果找到的节点过多，还会从结果map中再移除一些出去。
那IP Verified究竟又是什么含义呢？我们搜索所有创建CContact的地方，可以知道，已经连接上的CContact的IP会是Verified的。
Done。