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Merge remote-tracking branch 'asn-mytor/bug4726'
This commit is contained in:
Nick Mathewson
commit
37504b5efa
@ -4,6 +4,83 @@
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/**
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* \file transports.c
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* \brief Pluggable Transports related code.
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*
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* \details
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* Each managed proxy is represented by a <b>managed_proxy_t</b>.
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* Each managed proxy can support multiple transports.
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* Each managed proxy gets configured through a multistep process.
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*
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* ::managed_proxy_list contains all the managed proxies this tor
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* instance is supporting.
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* In the ::managed_proxy_list there are ::unconfigured_proxies_n
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* managed proxies that are still unconfigured.
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*
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* In every run_scheduled_event() tick, we attempt to launch and then
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* configure the unconfiged managed proxies, using the configuration
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* protocol defined in the 180_pluggable_transport.txt proposal. A
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* managed proxy might need several ticks to get fully configured.
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*
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* When a managed proxy is fully configured, we register all its
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* transports to the circuitbuild.c subsystem. At that point the
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* transports are owned by the circuitbuild.c subsystem.
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*
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* When a managed proxy fails to follow the 180 configuration
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* protocol, it gets marked as broken and gets destroyed.
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*
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* <b>In a little more detail:</b>
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*
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* While we are serially parsing torrc, we store all the transports
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* that a proxy should spawn in its <em>transports_to_launch</em>
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* element.
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*
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* When we finish reading the torrc, we spawn the managed proxy and
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* expect {S,C}METHOD lines from its output. We add transports
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* described by METHOD lines to its <em>transports</em> element, as
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* transport_t structs.
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*
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* When the managed proxy stops spitting METHOD lines (signified by a
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* '{S,C}METHODS DONE' message) we register all the transports
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* collected to the circuitbuild.c subsystem. At this point, the
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* pointers to transport_t can be transformed into dangling pointers
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* at any point by the circuitbuild.c subsystem, and so we replace all
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* transport_t pointers with strings describing the transport names.
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* We can still go from a transport name to a transport_t using the
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* fact that each transport name uniquely identifies a transport_t.
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*
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* <b>In even more detail, this is what happens when a SIGHUP
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* occurs:</b>
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*
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* We immediately destroy all unconfigured proxies (We shouldn't have
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* unconfigured proxies in the first place, except when SIGHUP rings
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* immediately after tor is launched.).
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*
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* We mark all managed proxies and transports to signify that they
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* must be removed if they don't contribute by the new torrc
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* (we mark using the <b>marked_for_removal</b> element).
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* We also mark all managed proxies to signify that they might need to
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* be restarted so that they end up supporting all the transports the
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* new torrc wants them to support (using the <b>got_hup</b> element).
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* We also clear their <b>transports_to_launch</b> list so that we can
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* put there the transports we need to launch according to the new
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* torrc.
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*
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* We then start parsing torrc again.
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*
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* Everytime we encounter a transport line using a known pre-SIGHUP
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* managed proxy, we cleanse that proxy from the removal mark.
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* We also mark it as unconfigured so that on the next scheduled
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* events tick, we investigate whether we need to restart the proxy
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* so that it also spawns the new transports.
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* If the post-SIGHUP <b>transports_to_launch</b> list is identical to
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* the pre-SIGHUP one, it means that no changes were introduced to
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* this proxy during the SIGHUP and no restart has to take place.
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*
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* During the post-SIGHUP torrc parsing, we unmark all transports
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* spawned by managed proxies that we find in our torrc.
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* We do that so that if we don't need to restart a managed proxy, we
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* can continue using its old transports normally.
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* If we end up restarting the proxy, we destroy and unregister all
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* old transports from the circuitbuild.c subsystem.
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**/
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#define PT_PRIVATE
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@ -64,84 +141,6 @@ static smartlist_t *managed_proxy_list = NULL;
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/** Number of still unconfigured proxies. */
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static int unconfigured_proxies_n = 0;
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/** "The main idea is:"
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Each managed proxy is represented by a 'managed_proxy_t'.
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Each managed proxy can support multiple transports.
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Each managed proxy gets configured through a multistep process.
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'managed_proxy_list' contains all the managed proxies this tor
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instance is supporting.
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In the 'managed_proxy_list' there are 'unconfigured_proxies_n'
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managed proxies that are still unconfigured.
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In every run_scheduled_event() tick, we attempt to launch and then
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configure the unconfiged managed proxies, using the configuration
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protocol defined in the 180_pluggable_transport.txt proposal. A
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managed proxy might need several ticks to get fully configured.
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When a managed proxy is fully configured, we register all its
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transports to the circuitbuild.c subsystem. At that point the
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transports are owned by the circuitbuild.c subsystem.
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When a managed proxy fails to follow the 180 configuration
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protocol, it gets marked as broken and gets destroyed.
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"In a little more technical detail:"
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While we are serially parsing torrc, we store all the transports
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that a proxy should spawn in its 'transports_to_launch' element.
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When we finish reading the torrc, we spawn the managed proxy and
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expect {S,C}METHOD lines from its output. We add transports
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described by METHOD lines to its 'transports' element, as
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'transport_t' structs.
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When the managed proxy stops spitting METHOD lines (signified by a
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'{S,C}METHODS DONE' message) we register all the transports
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collected to the circuitbuild.c subsystem. At this point, the
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'transport_t's can be transformed into dangling pointers at any
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point by the circuitbuild.c subsystem, and so we replace all
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'transport_t's with strings describing the transport names. We
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can still go from a transport name to a 'transport_t' using the
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fact that transport names uniquely identify 'transport_t's.
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"In even more technical detail I shall describe what happens when
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the SIGHUP bell tolls:"
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We immediately destroy all unconfigured proxies (We shouldn't have
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unconfigured proxies in the first place, except when SIGHUP rings
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immediately after tor is launched.).
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We mark all managed proxies and transports to signify that they
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must be removed if they don't contribute by the new torrc
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(marked_for_removal).
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We also mark all managed proxies to signify that they might need
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to be restarted so that they end up supporting all the transports
|
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the new torrc wants them to support (got_hup).
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We also clear their 'transports_to_launch' list so that we can put
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there the transports we need to launch according to the new torrc.
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We then start parsing torrc again.
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Everytime we encounter a transport line using a known pre-SIGHUP
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managed proxy, we cleanse that proxy from the removal mark.
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We also mark it as unconfigured so that on the next scheduled
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events tick, we investigate whether we need to restart the proxy
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so that it also spawns the new transports.
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If the post-SIGHUP 'transports_to_launch' list is identical to the
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pre-SIGHUP one, it means that no changes were introduced to this
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proxy during the SIGHUP and no restart has to take place.
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During the post-SIGHUP torrc parsing, we unmark all transports
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spawned by managed proxies that we find in our torrc.
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We do that so that if we don't need to restart a managed proxy, we
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can continue using its old transports normally.
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If we end up restarting the proxy, we destroy and unregister all
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old transports from the circuitbuild.c subsystem.
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*/
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/** Return true if there are still unconfigured managed proxies. */
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int
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pt_proxies_configuration_pending(void)
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