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/*
* ZeroTier One - Network Virtualization Everywhere
* Copyright (C) 2011-2016 ZeroTier, Inc. https://www.zerotier.com/
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef ZT_ARP_HPP
#define ZT_ARP_HPP
#include <stdint.h>
#include <utility>
#include "../node/Constants.hpp"
#include "../node/Hashtable.hpp"
#include "../node/MAC.hpp"
/**
* Maximum possible ARP length
*
* ARPs are 28 bytes in length, but specify a 128 byte buffer since
* some weird extensions we may support in the future can pad them
* out to as long as 72 bytes.
*/
#define ZT_ARP_BUF_LENGTH 128
/**
* Minimum permitted interval between sending ARP queries for a given IP
*/
#define ZT_ARP_QUERY_INTERVAL 2000
/**
* Maximum time between query and response, otherwise responses are discarded to prevent poisoning
*/
#define ZT_ARP_QUERY_MAX_TTL 5000
/**
* ARP expiration time
*/
#define ZT_ARP_EXPIRE 600000
namespace ZeroTier {
/**
* ARP cache and resolver
*
* To implement ARP:
*
* (1) Call processIncomingArp() on all ARP packets received and then always
* check responseLen after calling. If it is non-zero, send the contents
* of response to responseDest.
*
* (2) Call query() to look up IP addresses, and then check queryLen. If it
* is non-zero, send the contents of query to queryDest (usually broadcast).
*
* Note that either of these functions can technically generate a response or
* a query at any time, so their result parameters for sending ARPs should
* always be checked.
*
* This class is not thread-safe and must be guarded if used in multi-threaded
* code.
*/
class Arp
{
public:
Arp();
/**
* Set a local IP entry that we should respond to ARPs for
*
* @param mac Our local MAC address
* @param ip IP in big-endian byte order (sin_addr.s_addr)
*/
void addLocal(uint32_t ip,const MAC &mac);
/**
* Delete a local IP entry or a cached ARP entry
*
* @param ip IP in big-endian byte order (sin_addr.s_addr)
*/
void remove(uint32_t ip);
/**
* Process ARP packets
*
* For ARP queries, a response is generated and responseLen is set to its
* frame payload length in bytes.
*
* For ARP responses, the cache is populated and the IP address entry that
* was learned is returned.
*
* @param arp ARP frame data
* @param len Length of ARP frame (usually 28)
* @param response Response buffer -- MUST be a minimum of ZT_ARP_BUF_LENGTH in size
* @param responseLen Response length, or set to 0 if no response
* @param responseDest Destination of response, or set to null if no response
* @return IP address learned or 0 if no new IPs in cache
*/
uint32_t processIncomingArp(const void *arp,unsigned int len,void *response,unsigned int &responseLen,MAC &responseDest);
/**
* Get the MAC corresponding to an IP, generating a query if needed
*
* This returns a MAC for a remote IP. The local MAC is returned for local
* IPs as well. It may also generate a query if the IP is not known or the
* entry needs to be refreshed. In this case queryLen will be set to a
* non-zero value, so this should always be checked on return even if the
* MAC returned is non-null.
*
* @param localMac Local MAC address of host interface
* @param localIp Local IP address of host interface
* @param targetIp IP to look up
* @param query Buffer for generated query -- MUST be a minimum of ZT_ARP_BUF_LENGTH in size
* @param queryLen Length of generated query, or set to 0 if no query generated
* @param queryDest Destination of query, or set to null if no query generated
* @return MAC or 0 if no cached entry for this IP
*/
MAC query(const MAC &localMac,uint32_t localIp,uint32_t targetIp,void *query,unsigned int &queryLen,MAC &queryDest);
private:
struct _ArpEntry
{
_ArpEntry() : lastQuerySent(0),lastResponseReceived(0),mac(),local(false) {}
uint64_t lastQuerySent; // Time last query was sent or 0 for local IP
uint64_t lastResponseReceived; // Time of last ARP response or 0 for local IP
MAC mac; // MAC address of device responsible for IP or null if not known yet
bool local; // True if this is a local ARP entry
};
Hashtable< uint32_t,_ArpEntry > _cache;
uint64_t _lastCleaned;
};
} // namespace ZeroTier
#endif
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