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Diffstat (limited to 'osdep/Arp.hpp')
| -rw-r--r-- | osdep/Arp.hpp | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/osdep/Arp.hpp b/osdep/Arp.hpp new file mode 100644 index 00000000..b747cf85 --- /dev/null +++ b/osdep/Arp.hpp @@ -0,0 +1,156 @@ +/* + * ZeroTier One - Network Virtualization Everywhere + * Copyright (C) 2011-2015 ZeroTier, Inc. + * + * 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/>. + * + * -- + * + * ZeroTier may be used and distributed under the terms of the GPLv3, which + * are available at: http://www.gnu.org/licenses/gpl-3.0.html + * + * If you would like to embed ZeroTier into a commercial application or + * redistribute it in a modified binary form, please contact ZeroTier Networks + * LLC. Start here: http://www.zerotier.com/ + */ + +#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 ip 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 ip,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 |