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Copy pathpacketshell.cc
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146 lines (117 loc) · 5.33 KB
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/* -*-mode:c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
#include <thread>
#include <chrono>
#include <sys/socket.h>
#include <net/route.h>
#include "packetshell.hh"
#include "netdevice.hh"
#include "nat.hh"
#include "util.hh"
#include "interfaces.hh"
#include "address.hh"
#include "dns_server.hh"
#include "timestamp.hh"
#include "config.h"
using namespace std;
using namespace PollerShortNames;
template <class FerryQueueType>
PacketShell<FerryQueueType>::PacketShell( const std::string & device_prefix )
: egress_ingress( two_unassigned_addresses() ),
nameserver_( first_nameserver() ),
egress_tun_( device_prefix + "-" + to_string( getpid() ) , egress_addr(), ingress_addr() ),
dns_outside_( Address( egress_addr().ip(), "domain" ), nameserver_, nameserver_ ),
nat_rule_( ingress_addr() ),
pipe_( UnixDomainSocket::make_pair() ),
event_loop_()
{
/* make sure environment has been cleared */
if ( environ != nullptr ) {
throw Exception( "PacketShell", "environment was not cleared" );
}
/* initialize base timestamp value before any forking */
initial_timestamp();
}
template <class FerryQueueType>
template <typename... Targs>
void PacketShell<FerryQueueType>::start_uplink( const string & shell_prefix,
char ** const user_environment,
const vector< string > & command,
Targs&&... Fargs )
{
/* g++ bug 55914 makes this hard before version 4.9 */
auto ferry_maker = std::bind( []( Targs&&... Fargs ) {
return FerryQueueType( forward<Targs>( Fargs )... );
}, forward<Targs>( Fargs )... );
/* Fork */
event_loop_.add_child_process( ChildProcess( "packetshell", [&]() {
TunDevice ingress_tun( "ingress", ingress_addr(), egress_addr() );
/* bring up localhost */
interface_ioctl( Socket( UDP ), SIOCSIFFLAGS, "lo",
[] ( ifreq &ifr ) { ifr.ifr_flags = IFF_UP; } );
/* create default route */
rtentry route;
zero( route );
route.rt_gateway = egress_addr().raw_sockaddr();
route.rt_dst = route.rt_genmask = Address().raw_sockaddr();
route.rt_flags = RTF_UP | RTF_GATEWAY;
SystemCall( "ioctl SIOCADDRT", ioctl( Socket( UDP ).num(), SIOCADDRT, &route ) );
Ferry inner_ferry;
/* run dnsmasq as local caching nameserver */
inner_ferry.add_child_process( ChildProcess( start_dnsmasq( {
"-S", dns_outside_.udp_listener().local_addr().str( "#" ) } ) ) );
/* Fork again after dropping root privileges */
drop_privileges();
inner_ferry.add_child_process( ChildProcess( join( command ), [&]() {
/* restore environment and tweak bash prompt */
environ = user_environment;
prepend_shell_prefix( shell_prefix );
return ezexec( command, true );
} ) );
/* allow downlink to write directly to inner namespace's TUN device */
pipe_.first.send_fd( ingress_tun );
FerryQueueType uplink_queue = ferry_maker();
return inner_ferry.loop( uplink_queue, ingress_tun, egress_tun_ );
}, true ) ); /* new network namespace */
}
template <class FerryQueueType>
template <typename... Targs>
void PacketShell<FerryQueueType>::start_downlink( Targs&&... Fargs )
{
auto ferry_maker = std::bind( []( Targs&&... Fargs ) {
return FerryQueueType( forward<Targs>( Fargs )... );
}, forward<Targs>( Fargs )... );
event_loop_.add_child_process( ChildProcess( "downlink", [&] () {
drop_privileges();
/* downlink packets go to inner namespace's TUN device */
FileDescriptor ingress_tun = pipe_.second.recv_fd();
Ferry outer_ferry;
dns_outside_.register_handlers( outer_ferry );
FerryQueueType downlink_queue = ferry_maker();
return outer_ferry.loop( downlink_queue, egress_tun_, ingress_tun );
} ) );
}
template <class FerryQueueType>
int PacketShell<FerryQueueType>::wait_for_exit( void )
{
return event_loop_.loop();
}
template <class FerryQueueType>
int PacketShell<FerryQueueType>::Ferry::loop( FerryQueueType & ferry_queue,
FileDescriptor & tun,
FileDescriptor & sibling )
{
/* tun device gets datagram -> read it -> give to ferry */
add_simple_input_handler( tun,
[&] () {
ferry_queue.read_packet( tun.read() );
return ResultType::Continue;
} );
/* ferry ready to write datagram -> send to sibling's tun device */
add_action( Poller::Action( sibling, Direction::Out,
[&] () {
ferry_queue.write_packets( sibling );
return ResultType::Continue;
},
[&] () { return ferry_queue.wait_time() <= 0; } ) );
return internal_loop( [&] () { return ferry_queue.wait_time(); } );
}