commit b2789ae72aab35443c2988d930495b8efa870f3e Author: Mike Perry <mikeperry-git@torproject.org> Date: Tue Nov 16 22:01:54 2021 +0000 Add hidden torrc option to always try CC negotiation. This is for public network testing and for sbws. Should not otherwise be used, hence it is an undocumented __option. The option deliberately does not allow force-disabling congestion control, as this is bad for queueing and fairness. --- src/app/config/config.c | 1 + src/app/config/or_options_st.h | 3 +++ src/core/or/congestion_control_common.c | 46 +++++++++++++++++++++++++++------ 3 files changed, 42 insertions(+), 8 deletions(-) diff --git a/src/app/config/config.c b/src/app/config/config.c index 8df5275cc6..05bd96fc6a 100644 --- a/src/app/config/config.c +++ b/src/app/config/config.c @@ -675,6 +675,7 @@ static const config_var_t option_vars_[] = { V(VanguardsLiteEnabled, AUTOBOOL, "auto"), V(UseMicrodescriptors, AUTOBOOL, "auto"), OBSOLETE("UseNTorHandshake"), + VAR("__AlwaysCongestionControl", BOOL, AlwaysCongestionControl, "0"), V_IMMUTABLE(User, STRING, NULL), OBSOLETE("UserspaceIOCPBuffers"), OBSOLETE("V1AuthoritativeDirectory"), diff --git a/src/app/config/or_options_st.h b/src/app/config/or_options_st.h index 3a1acad044..a1ef7a8cf8 100644 --- a/src/app/config/or_options_st.h +++ b/src/app/config/or_options_st.h @@ -601,6 +601,9 @@ struct or_options_t { /** Boolean: Switch to toggle the vanguards-lite subsystem */ int VanguardsLiteEnabled; + /** Boolean: Switch to override consensus to enable congestion control */ + int AlwaysCongestionControl; + int RephistTrackTime; /**< How many seconds do we keep rephist info? */ /** Should we always fetch our dir info on the mirror schedule (which * means directly from the authorities) no matter our other config? */ diff --git a/src/core/or/congestion_control_common.c b/src/core/or/congestion_control_common.c index d4b933a032..7e38510814 100644 --- a/src/core/or/congestion_control_common.c +++ b/src/core/or/congestion_control_common.c @@ -26,6 +26,7 @@ #include "core/or/trace_probes_cc.h" #include "lib/time/compat_time.h" #include "feature/nodelist/networkstatus.h" +#include "app/config/config.h" /* Consensus parameter defaults. * @@ -34,6 +35,7 @@ #define CIRCWINDOW_INIT (500) #define SENDME_INC_DFLT (50) #define CC_ALG_DFLT (CC_ALG_SENDME) +#define CC_ALG_DFLT_ALWAYS (CC_ALG_VEGAS) #define CWND_INC_DFLT (50) #define CWND_INC_PCT_SS_DFLT (100) @@ -161,6 +163,7 @@ static void congestion_control_init_params(congestion_control_t *cc, const circuit_params_t *params) { + const or_options_t *opts = get_options(); cc->sendme_inc = params->sendme_inc_cells; #define CWND_INIT_MIN 100 @@ -219,13 +222,14 @@ congestion_control_init_params(congestion_control_t *cc, BWE_SENDME_MIN_MIN, BWE_SENDME_MIN_MAX); -#define CC_ALG_MIN 0 -#define CC_ALG_MAX (NUM_CC_ALGS-1) - cc->cc_alg = - networkstatus_get_param(NULL, "cc_alg", - cc_alg, - CC_ALG_MIN, - CC_ALG_MAX); + /* If the consensus says to use OG sendme, but torrc has + * always-enabled, use the default "always" alg (vegas), + * else use cached conensus alg. */ + if (cc_alg == CC_ALG_SENDME && opts->AlwaysCongestionControl) { + cc->cc_alg = CC_ALG_DFLT_ALWAYS; + } else { + cc->cc_alg = cc_alg; + } bdp_alg_t default_bdp_alg = 0; @@ -262,10 +266,36 @@ congestion_control_init_params(congestion_control_t *cc, } /** Returns true if congestion control is enabled in the most recent - * consensus */ + * consensus, or if __AlwaysCongestionControl is set to true. + * + * Note that this function (and many many other functions) should not + * be called from the CPU worker threads when handling congestion + * control negotiation. Relevant values are marshaled into the + * `circuit_params_t` struct, in order to be used in worker threads + * without touching global state. Use those values in CPU worker + * threads, instead of calling this function. + * + * The danger is still present, in your time, as it was in ours. + */ bool congestion_control_enabled(void) { + const or_options_t *opts = NULL; + + tor_assert_nonfatal_once(in_main_thread()); + + opts = get_options(); + + /* If the user has set "__AlwaysCongesttionControl", + * then always try to negotiate congestion control, regardless + * of consensus param. This is to be used for testing and sbws. + * + * Note that we do *not* allow disabling congestion control + * if the consensus says to use it, as this is bad for queueing + * and fairness. */ + if (opts->AlwaysCongestionControl) + return 1; + return cc_alg != CC_ALG_SENDME; }