Main Event Loop module

This main event loop module drives the packet processing of OpenVPN. More...

Functions
static void	tunnel_server_loop (struct multi_context *multi)
	Main event loop for OpenVPN in point-to-multipoint server mode.
void	tunnel_server (struct context *top)
	Main event loop for OpenVPN in server mode.
static void	tunnel_point_to_point (struct context *c)
	Main event loop for OpenVPN in client mode, where only one VPN tunnel is active.
static int	openvpn_main (int argc, char *argv[])
	OpenVPN's main init-run-cleanup loop.

Detailed Description

This main event loop module drives the packet processing of OpenVPN.

OpenVPN is an event driven system. Its activities are driven by a main event loop, which repeatedly waits for one of several predefined events to occur, and then calls the appropriate module to handle the event. The major types of network events that OpenVPN processes are:

• A packet can be read from the external network interface.
  • The main event loop activates the External Multiplexer to read and process the packet.
• A packet can be read from the virtual tun/tap network interface.
  • The main event loop activates the Internal Multiplexer to read and process the packet.
• If a packet is ready to be sent out as a VPN tunnel packet: the external network interface can be written to.
  • The main event loop activates the External Multiplexer to send the packet.
• If a packet is ready to be sent to a locally reachable destination: the virtual tun/tap network interface can be written to.
  • The main event loop activates the Internal Multiplexer to send the packet.

Beside these external events, OpenVPN also processes other types of internal events. These include scheduled events, such as resending of non-acknowledged control channel messages.

Main event loop implementations

Depending on the mode in which OpenVPN is running, a different main event loop function is called to drive the event processing. The following implementations are available:

• Client mode using UDP or TCP: tunnel_point_to_point()
• Server mode using UDP: tunnel_server_udp()
• Server mode using TCP: tunnel_server_tcp()

Function Documentation

openvpn_main()

static int openvpn_main ( int  argc, char *  argv[]  )

static

OpenVPN's main init-run-cleanup loop.

This function contains the two outer OpenVPN loops. Its structure is as follows:

• Once-per-process initialization.
• Outer loop, run at startup and then once per SIGHUP:
  • Level 1 initialization
  • Inner loop, run at startup and then once per SIGUSR1:
    • Call event loop function depending on client or server mode:
      • tunnel_point_to_point()
      • tunnel_server()
  • Level 1 cleanup
• Once-per-process cleanup.

Parameters

argc	- Commandline argument count.
argv	- Commandline argument values.

Definition at line 162 of file openvpn.c.

References ASSERT, options::chroot_dir, CLEAR, close_management(), context_clear_all_except_first_time(), context_gc_free(), context_init_1(), context::did_we_daemonize, do_genkey(), do_persist_tuntap(), do_test_crypto(), env_set_create(), env_set_destroy(), context::es, context::first_time, context::gc, gc_init(), gc_reset(), init_early(), init_management(), init_options(), init_options_dev(), init_plugins(), init_query_passwords(), init_static(), init_verb_mute(), IS_SIG, IVM_LEVEL_1, M_INFO, M_USAGE, options::management_flags, MF_QUERY_PASSWORDS, options::mode, MODE_POINT_TO_POINT, MODE_SERVER, msg, context::net_ctx, open_management(), open_plugins(), openvpn_exit(), OPENVPN_EXIT_STATUS_GOOD, OPT_P_DEFAULT, context::options, options_postprocess(), parse_argv(), possibly_become_daemon(), pre_init_signal_catch(), pre_setup(), print_openssl_info(), print_signal(), set_win_sys_path_via_env(), setenv_settings(), show_dco_version(), show_library_versions(), show_settings(), show_windows_version(), context::sig, siginfo_static, signal_reset(), signal_restart_status(), title_string, tunnel_point_to_point(), tunnel_server(), uninit_early(), uninit_options(), uninit_static(), write_pid_file(), and options::writepid.

Referenced by wmain().

tunnel_point_to_point()

static void tunnel_point_to_point ( struct context *  c )

static

Main event loop for OpenVPN in client mode, where only one VPN tunnel is active.

Parameters

c	- The context structure of the single active VPN tunnel.

Definition at line 58 of file openvpn.c.

References context::c2, CC_HARD_USR1_TO_HUP, close_instance(), CM_P2P, options::config, context_clear_2(), context::es, ES_TIMEOUT, context_2::event_set_status, init_instance_handle_signals(), io_wait(), IS_SIG, context_2::link_sockets, context::mode, context::options, P2P_CHECK_SIG, p2p_iow_flags(), PERF_EVENT_LOOP, perf_pop(), perf_push(), persist_client_stats(), pre_select(), process_io(), and uninit_management_callback().

Referenced by openvpn_main().

tunnel_server()

void tunnel_server

(

struct context *

top

)

Main event loop for OpenVPN in server mode.

Parameters

top	- Top-level context structure.

Definition at line 4219 of file multi.c.

References ASSERT, context::c2, CC_HARD_USR1_TO_HUP, close_instance(), CM_TOP, context_clear_2(), D_MULTI_ERRORS, context::es, init_instance_handle_signals(), init_management_callback_multi(), initialization_sequence_completed(), IS_SIG, ISC_SERVER, M_ERRNO, context::mode, options::mode, MODE_SERVER, msg, multi_ifconfig_pool_persist(), multi_init(), multi_top_free(), multi_top_init(), multi_uninit(), context::options, multi_context::top, tunnel_server_loop(), and uninit_management_callback().

Referenced by openvpn_main().

tunnel_server_loop()

static void tunnel_server_loop ( struct multi_context *  multi )

static

Main event loop for OpenVPN in point-to-multipoint server mode.

Parameters

top	- Top-level context structure.

Definition at line 4183 of file multi.c.

References context::c2, MULTI_CHECK_SIG, multi_get_timeout(), multi_io_action(), multi_io_process_io(), multi_io_wait(), multi_process_per_second_timers(), PERF_EVENT_LOOP, perf_pop(), perf_push(), status, TA_TIMEOUT, context_2::timeval, and multi_context::top.

Referenced by tunnel_server().