mirror of
https://github.com/didyouexpectthat/zerotierone.git
synced 2024-11-14 04:00:07 -08:00
149 lines
4.7 KiB
C++
149 lines
4.7 KiB
C++
/*
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* ZeroTier One - Network Virtualization Everywhere
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* Copyright (C) 2011-2016 ZeroTier, Inc. https://www.zerotier.com/
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ZT_ARP_HPP
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#define ZT_ARP_HPP
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#include <stdint.h>
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#include <utility>
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#include "../node/Constants.hpp"
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#include "../node/Hashtable.hpp"
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#include "../node/MAC.hpp"
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/**
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* Maximum possible ARP length
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*
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* ARPs are 28 bytes in length, but specify a 128 byte buffer since
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* some weird extensions we may support in the future can pad them
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* out to as long as 72 bytes.
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*/
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#define ZT_ARP_BUF_LENGTH 128
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/**
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* Minimum permitted interval between sending ARP queries for a given IP
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*/
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#define ZT_ARP_QUERY_INTERVAL 2000
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/**
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* Maximum time between query and response, otherwise responses are discarded to prevent poisoning
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*/
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#define ZT_ARP_QUERY_MAX_TTL 5000
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/**
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* ARP expiration time
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*/
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#define ZT_ARP_EXPIRE 600000
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namespace ZeroTier {
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/**
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* ARP cache and resolver
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*
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* To implement ARP:
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*
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* (1) Call processIncomingArp() on all ARP packets received and then always
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* check responseLen after calling. If it is non-zero, send the contents
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* of response to responseDest.
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*
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* (2) Call query() to look up IP addresses, and then check queryLen. If it
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* is non-zero, send the contents of query to queryDest (usually broadcast).
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*
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* Note that either of these functions can technically generate a response or
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* a query at any time, so their result parameters for sending ARPs should
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* always be checked.
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*
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* This class is not thread-safe and must be guarded if used in multi-threaded
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* code.
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*/
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class Arp
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{
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public:
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Arp();
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/**
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* Set a local IP entry that we should respond to ARPs for
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*
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* @param mac Our local MAC address
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* @param ip IP in big-endian byte order (sin_addr.s_addr)
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*/
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void addLocal(uint32_t ip,const MAC &mac);
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/**
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* Delete a local IP entry or a cached ARP entry
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*
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* @param ip IP in big-endian byte order (sin_addr.s_addr)
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*/
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void remove(uint32_t ip);
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/**
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* Process ARP packets
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*
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* For ARP queries, a response is generated and responseLen is set to its
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* frame payload length in bytes.
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*
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* For ARP responses, the cache is populated and the IP address entry that
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* was learned is returned.
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*
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* @param arp ARP frame data
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* @param len Length of ARP frame (usually 28)
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* @param response Response buffer -- MUST be a minimum of ZT_ARP_BUF_LENGTH in size
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* @param responseLen Response length, or set to 0 if no response
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* @param responseDest Destination of response, or set to null if no response
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* @return IP address learned or 0 if no new IPs in cache
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*/
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uint32_t processIncomingArp(const void *arp,unsigned int len,void *response,unsigned int &responseLen,MAC &responseDest);
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/**
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* Get the MAC corresponding to an IP, generating a query if needed
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*
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* This returns a MAC for a remote IP. The local MAC is returned for local
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* IPs as well. It may also generate a query if the IP is not known or the
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* entry needs to be refreshed. In this case queryLen will be set to a
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* non-zero value, so this should always be checked on return even if the
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* MAC returned is non-null.
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*
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* @param localMac Local MAC address of host interface
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* @param localIp Local IP address of host interface
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* @param targetIp IP to look up
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* @param query Buffer for generated query -- MUST be a minimum of ZT_ARP_BUF_LENGTH in size
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* @param queryLen Length of generated query, or set to 0 if no query generated
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* @param queryDest Destination of query, or set to null if no query generated
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* @return MAC or 0 if no cached entry for this IP
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*/
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MAC query(const MAC &localMac,uint32_t localIp,uint32_t targetIp,void *query,unsigned int &queryLen,MAC &queryDest);
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private:
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struct _ArpEntry
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{
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_ArpEntry() : lastQuerySent(0),lastResponseReceived(0),mac(),local(false) {}
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uint64_t lastQuerySent; // Time last query was sent or 0 for local IP
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uint64_t lastResponseReceived; // Time of last ARP response or 0 for local IP
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MAC mac; // MAC address of device responsible for IP or null if not known yet
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bool local; // True if this is a local ARP entry
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};
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Hashtable< uint32_t,_ArpEntry > _cache;
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uint64_t _lastCleaned;
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};
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} // namespace ZeroTier
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#endif
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