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110 lines
3.2 KiB
110 lines
3.2 KiB
/* |
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* ZeroTier One - Global Peer to Peer Ethernet |
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* Copyright (C) 2011-2015 ZeroTier Networks |
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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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* -- |
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* |
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* ZeroTier may be used and distributed under the terms of the GPLv3, which |
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* are available at: http://www.gnu.org/licenses/gpl-3.0.html |
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* |
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* If you would like to embed ZeroTier into a commercial application or |
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* redistribute it in a modified binary form, please contact ZeroTier Networks |
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* LLC. Start here: http://www.zerotier.com/ |
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*/ |
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#ifndef ZT_ANTIRECURSION_HPP |
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#define ZT_ANTIRECURSION_HPP |
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#include <string.h> |
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#include <stdlib.h> |
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#include "Constants.hpp" |
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namespace ZeroTier { |
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#define ZT_ANTIRECURSION_TAIL_LEN 256 |
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/** |
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* Filter to prevent recursion (ZeroTier-over-ZeroTier) |
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* |
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* This works by logging ZeroTier packets that we send. It's then invoked |
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* again against packets read from local Ethernet taps. If the last N |
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* bytes representing the ZeroTier packet match in the tap frame, then |
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* the frame is a re-injection of a frame that we sent and is rejected. |
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* |
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* This means that ZeroTier packets simply will not traverse ZeroTier |
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* networks, which would cause all sorts of weird problems. |
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* |
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* NOTE: this is applied to low-level packets before they are sent to |
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* SocketManager and/or sockets, not to fully assembled packets before |
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* (possible) fragmentation. |
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*/ |
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class AntiRecursion |
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{ |
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public: |
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AntiRecursion() |
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throw() |
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{ |
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memset(_history,0,sizeof(_history)); |
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_ptr = 0; |
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} |
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/** |
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* Add an outgoing ZeroTier packet to the circular log |
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* |
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* @param data ZT packet data |
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* @param len Length of packet |
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*/ |
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inline void logOutgoingZT(const void *data,unsigned int len) |
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throw() |
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{ |
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ArItem *i = &(_history[_ptr++ % ZT_ANTIRECURSION_HISTORY_SIZE]); |
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const unsigned int tl = (len > ZT_ANTIRECURSION_TAIL_LEN) ? ZT_ANTIRECURSION_TAIL_LEN : len; |
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memcpy(i->tail,((const unsigned char *)data) + (len - tl),tl); |
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i->len = tl; |
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} |
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/** |
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* Check an ethernet frame from a local tap against anti-recursion history |
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* |
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* @param data Raw frame data |
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* @param len Length of frame |
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* @return True if frame is OK to be passed, false if it's a ZT frame that we sent |
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*/ |
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inline bool checkEthernetFrame(const void *data,unsigned int len) |
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throw() |
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{ |
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for(unsigned int h=0;h<ZT_ANTIRECURSION_HISTORY_SIZE;++h) { |
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ArItem *i = &(_history[h]); |
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if ((i->len > 0)&&(len >= i->len)&&(!memcmp(((const unsigned char *)data) + (len - i->len),i->tail,i->len))) |
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return false; |
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} |
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return true; |
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} |
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private: |
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struct ArItem |
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{ |
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unsigned char tail[ZT_ANTIRECURSION_TAIL_LEN]; |
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unsigned int len; |
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}; |
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ArItem _history[ZT_ANTIRECURSION_HISTORY_SIZE]; |
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volatile unsigned int _ptr; |
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}; |
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} // namespace ZeroTier |
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#endif
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