Line data    Source code

       1             : /*
       2             :     Mosh: the mobile shell
       3             :     Copyright 2012 Keith Winstein
       4             : 
       5             :     This program is free software: you can redistribute it and/or modify
       6             :     it under the terms of the GNU General Public License as published by
       7             :     the Free Software Foundation, either version 3 of the License, or
       8             :     (at your option) any later version.
       9             : 
      10             :     This program is distributed in the hope that it will be useful,
      11             :     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12             :     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      13             :     GNU General Public License for more details.
      14             : 
      15             :     You should have received a copy of the GNU General Public License
      16             :     along with this program.  If not, see <http://www.gnu.org/licenses/>.
      17             : 
      18             :     In addition, as a special exception, the copyright holders give
      19             :     permission to link the code of portions of this program with the
      20             :     OpenSSL library under certain conditions as described in each
      21             :     individual source file, and distribute linked combinations including
      22             :     the two.
      23             : 
      24             :     You must obey the GNU General Public License in all respects for all
      25             :     of the code used other than OpenSSL. If you modify file(s) with this
      26             :     exception, you may extend this exception to your version of the
      27             :     file(s), but you are not obligated to do so. If you do not wish to do
      28             :     so, delete this exception statement from your version. If you delete
      29             :     this exception statement from all source files in the program, then
      30             :     also delete it here.
      31             : */
      32             : 
      33             : #ifndef NETWORK_HPP
      34             : #define NETWORK_HPP
      35             : 
      36             : #include <stdint.h>
      37             : #include <deque>
      38             : #include <sys/socket.h>
      39             : #include <netinet/in.h>
      40             : #include <string>
      41             : #include <math.h>
      42             : #include <vector>
      43             : #include <assert.h>
      44             : #include <exception>
      45             : #include <string.h>
      46             : 
      47             : #include "crypto.h"
      48             : 
      49             : using namespace Crypto;
      50             : 
      51             : namespace Network {
      52             :   static const unsigned int MOSH_PROTOCOL_VERSION = 2; /* bumped for echo-ack */
      53             : 
      54             :   uint64_t timestamp( void );
      55             :   uint16_t timestamp16( void );
      56             :   uint16_t timestamp_diff( uint16_t tsnew, uint16_t tsold );
      57             : 
      58             :   class NetworkException : public std::exception {
      59             :   public:
      60             :     string function;
      61             :     int the_errno;
      62             :   private:
      63             :     string my_what;
      64             :   public:
      65           0 :     NetworkException( string s_function="<none>", int s_errno=0)
      66           0 :       : function( s_function ), the_errno( s_errno ),
      67           0 :         my_what(function + ": " + strerror(the_errno)) {}
      68           0 :     const char *what() const throw () { return my_what.c_str(); }
      69           0 :     ~NetworkException() throw () {}
      70             :   };
      71             : 
      72             :   enum Direction {
      73             :     TO_SERVER = 0,
      74             :     TO_CLIENT = 1
      75             :   };
      76             : 
      77     8021236 :   class Packet {
      78             :   public:
      79             :     const uint64_t seq;
      80             :     Direction direction;
      81             :     uint16_t timestamp, timestamp_reply;
      82             :     string payload;
      83             :     
      84     8005333 :     Packet( Direction s_direction,
      85             :             uint16_t s_timestamp, uint16_t s_timestamp_reply, const string & s_payload )
      86     8005333 :       : seq( Crypto::unique() ), direction( s_direction ),
      87     8005333 :         timestamp( s_timestamp ), timestamp_reply( s_timestamp_reply ), payload( s_payload )
      88     8000000 :     {}
      89             :     
      90             :     Packet( const Message & message );
      91             :     
      92             :     Message toMessage( void );
      93             :   };
      94             : 
      95             :   union Addr {
      96             :     struct sockaddr sa;
      97             :     struct sockaddr_in sin;
      98             :     struct sockaddr_in6 sin6;
      99             :     struct sockaddr_storage ss;
     100             :   };
     101             : 
     102             :   class Connection {
     103             :   private:
     104             :     /*
     105             :      * For IPv4, guess the typical (minimum) header length;
     106             :      * fragmentation is not dangerous, just inefficient.
     107             :      */
     108             :     static const int IPV4_HEADER_LEN = 20 /* base IP header */
     109             :       + 8 /* UDP */;
     110             :     /*
     111             :      * For IPv6, we don't want to ever have MTU issues, so make a
     112             :      * conservative guess about header size.
     113             :      */
     114             :     static const int IPV6_HEADER_LEN = 40 /* base IPv6 header */
     115             :       + 16 /* 2 minimum-sized extension headers */
     116             :       + 8 /* UDP */;
     117             :     /* Application datagram MTU. For constructors and fallback. */
     118             :     static const int DEFAULT_SEND_MTU = 500;
     119             :     /*
     120             :      * IPv4 MTU. Don't use full Ethernet-derived MTU,
     121             :      * mobile networks have high tunneling overhead.
     122             :      *
     123             :      * As of July 2016, VPN traffic over Amtrak Acela wifi seems to be
     124             :      * dropped if tunnelled packets are 1320 bytes or larger.  Use a
     125             :      * 1280-byte IPv4 MTU for now.
     126             :      *
     127             :      * We may have to implement ICMP-less PMTUD (RFC 4821) eventually.
     128             :      */
     129             :     static const int DEFAULT_IPV4_MTU = 1280;
     130             :     /* IPv6 MTU. Use the guaranteed minimum to avoid fragmentation. */
     131             :     static const int DEFAULT_IPV6_MTU = 1280;
     132             : 
     133             :     static const uint64_t MIN_RTO = 50; /* ms */
     134             :     static const uint64_t MAX_RTO = 1000; /* ms */
     135             : 
     136             :     static const int PORT_RANGE_LOW  = 60001;
     137             :     static const int PORT_RANGE_HIGH = 60999;
     138             : 
     139             :     static const unsigned int SERVER_ASSOCIATION_TIMEOUT = 40000;
     140             :     static const unsigned int PORT_HOP_INTERVAL          = 10000;
     141             : 
     142             :     static const unsigned int MAX_PORTS_OPEN             = 10;
     143             :     static const unsigned int MAX_OLD_SOCKET_AGE         = 60000;
     144             : 
     145             :     static const int CONGESTION_TIMESTAMP_PENALTY = 500; /* ms */
     146             : 
     147             :     bool try_bind( const char *addr, int port_low, int port_high );
     148             : 
     149             :     class Socket
     150             :     {
     151             :     private:
     152             :       int _fd;
     153             : 
     154             :     public:
     155       38417 :       int fd( void ) const { return _fd; }
     156             :       Socket( int family );
     157             :       ~Socket();
     158             : 
     159             :       Socket( const Socket & other );
     160             :       Socket & operator=( const Socket & other );
     161             :     };
     162             : 
     163             :     std::deque< Socket > socks;
     164             :     bool has_remote_addr;
     165             :     Addr remote_addr;
     166             :     socklen_t remote_addr_len;
     167             : 
     168             :     bool server;
     169             : 
     170             :     int MTU; /* application datagram MTU */
     171             : 
     172             :     Base64Key key;
     173             :     Session session;
     174             : 
     175             :     void setup( void );
     176             : 
     177             :     Direction direction;
     178             :     uint16_t saved_timestamp;
     179             :     uint64_t saved_timestamp_received_at;
     180             :     uint64_t expected_receiver_seq;
     181             : 
     182             :     uint64_t last_heard;
     183             :     uint64_t last_port_choice;
     184             :     uint64_t last_roundtrip_success; /* transport layer needs to tell us this */
     185             : 
     186             :     bool RTT_hit;
     187             :     double SRTT;
     188             :     double RTTVAR;
     189             : 
     190             :     /* Error from send()/sendto(). */
     191             :     string send_error;
     192             : 
     193             :     Packet new_packet( const string &s_payload );
     194             : 
     195             :     void hop_port( void );
     196             : 
     197        7659 :     int sock( void ) const { assert( !socks.empty() ); return socks.back().fd(); }
     198             : 
     199             :     void prune_sockets( void );
     200             : 
     201             :     string recv_one( int sock_to_recv );
     202             : 
     203             :     void set_MTU( int family );
     204             : 
     205             :   public:
     206             :     /* Network transport overhead. */
     207             :     static const int ADDED_BYTES = 8 /* seqno/nonce */ + 4 /* timestamps */;
     208             : 
     209             :     Connection( const char *desired_ip, const char *desired_port ); /* server */
     210             :     Connection( const char *key_str, const char *ip, const char *port ); /* client */
     211             : 
     212             :     void send( const string & s );
     213             :     string recv( void );
     214             :     const std::vector< int > fds( void ) const;
     215        5329 :     int get_MTU( void ) const { return MTU; }
     216             : 
     217             :     std::string port( void ) const;
     218         452 :     string get_key( void ) const { return key.printable_key(); }
     219       65370 :     bool get_has_remote_addr( void ) const { return has_remote_addr; }
     220             : 
     221             :     uint64_t timeout( void ) const;
     222        3385 :     double get_SRTT( void ) const { return SRTT; }
     223             : 
     224             :     const Addr &get_remote_addr( void ) const { return remote_addr; }
     225             :     socklen_t get_remote_addr_len( void ) const { return remote_addr_len; }
     226             : 
     227        5640 :     string &get_send_error( void )
     228             :     {
     229        5640 :       return send_error;
     230             :     }
     231             : 
     232        5281 :     void set_last_roundtrip_success( uint64_t s_success ) { last_roundtrip_success = s_success; }
     233             : 
     234             :     static bool parse_portrange( const char * desired_port_range, int & desired_port_low, int & desired_port_high );
     235             :   };
     236             : }
     237             : 
     238             : #endif