mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-20 18:22:09 +01:00
Implement new Wxx constraints.
Cases 1 and 3b are provably correct. Case 2b has a fallback to first try to maximize entropy.
This commit is contained in:
Mike Perry
parent
9b49a89430
commit
0ff86042ac
279
src/or/dirvote.c
279
src/or/dirvote.c
@ -50,7 +50,7 @@ static int dirvote_publish_consensus(void);
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static char *make_consensus_method_list(int low, int high, const char *sep);
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/** The highest consensus method that we currently support. */
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#define MAX_SUPPORTED_CONSENSUS_METHOD 9
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#define MAX_SUPPORTED_CONSENSUS_METHOD 10
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/** Lowest consensus method that contains a 'directory-footer' marker */
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#define MIN_METHOD_FOR_FOOTER 9
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@ -766,15 +766,275 @@ networkstatus_check_weights(int64_t Wgg, int64_t Wgd, int64_t Wmg,
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if (berr) {
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log_info(LD_DIR,
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"Bw weight mismatch %d. G="I64_FORMAT" M="I64_FORMAT
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" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT,
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" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT
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" Wmd=%d Wme=%d Wmg=%d Wed=%d Wee=%d"
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" Wgd=%d Wgg=%d Wme=%d Wmg=%d",
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berr,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T));
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T),
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(int)Wmd, (int)Wme, (int)Wmg, (int)Wed, (int)Wee,
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(int)Wgd, (int)Wgg, (int)Wme, (int)Wmg);
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}
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return berr;
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}
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/**
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* This function computes the bandwidth weights for consensus method 10.
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*
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* It returns true if weights could be computed, false otherwise.
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*/
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static int
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networkstatus_compute_bw_weights_v10(smartlist_t *chunks, int64_t G,
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int64_t M, int64_t E, int64_t D,
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int64_t T, int64_t weight_scale)
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{
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bw_weights_error_t berr = 0;
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int64_t Wgg = -1, Wgd = -1;
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int64_t Wmg = -1, Wme = -1, Wmd = -1;
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int64_t Wed = -1, Wee = -1;
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const char *casename;
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char buf[512];
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int r;
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if (G <= 0 || M <= 0 || E <= 0 || D <= 0) {
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log_warn(LD_DIR, "Consensus with empty bandwidth: "
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"G="I64_FORMAT" M="I64_FORMAT" E="I64_FORMAT
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" D="I64_FORMAT" T="I64_FORMAT,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T));
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return 0;
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}
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/*
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* Computed from cases in 3.4.3 of dir-spec.txt
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*
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* 1. Neither are scarce
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* 2. Both Guard and Exit are scarce
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* a. R+D <= S
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* b. R+D > S
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* 3. One of Guard or Exit is scarce
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* a. S+D < T/3
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* b. S+D >= T/3
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*/
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if (3*E >= T && 3*G >= T) { // E >= T/3 && G >= T/3
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/* Case 1: Neither are scarce. */
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casename = "Case 1 (Wgd=Wmd=Wed)";
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Wgd = weight_scale/3;
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Wed = weight_scale/3;
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Wmd = weight_scale/3;
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Wee = (weight_scale*(E+G+M))/(3*E);
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Wme = weight_scale - Wee;
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Wmg = (weight_scale*(2*G-E-M))/(3*G);
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Wgg = weight_scale - Wmg;
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berr = networkstatus_check_weights(Wgg, Wgd, Wmg, Wme, Wmd, Wee, Wed,
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weight_scale, G, M, E, D, T, 10, 1);
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if (berr) {
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log_warn(LD_DIR,
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"Bw Weights error %d for %s v10. G="I64_FORMAT" M="I64_FORMAT
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" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT
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" Wmd=%d Wme=%d Wmg=%d Wed=%d Wee=%d"
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" Wgd=%d Wgg=%d Wme=%d Wmg=%d weight_scale=%d",
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berr, casename,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T),
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(int)Wmd, (int)Wme, (int)Wmg, (int)Wed, (int)Wee,
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(int)Wgd, (int)Wgg, (int)Wme, (int)Wmg, (int)weight_scale);
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return 0;
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}
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} else if (3*E < T && 3*G < T) { // E < T/3 && G < T/3
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int64_t R = MIN(E, G);
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int64_t S = MAX(E, G);
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/*
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* Case 2: Both Guards and Exits are scarce
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* Balance D between E and G, depending upon
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* D capacity and scarcity.
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*/
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if (R+D < S) { // Subcase a
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Wgg = weight_scale;
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Wee = weight_scale;
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Wmg = 0;
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Wme = 0;
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Wmd = 0;
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if (E < G) {
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casename = "Case 2a (E scarce)";
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Wed = weight_scale;
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Wgd = 0;
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} else { /* E >= G */
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casename = "Case 2a (G scarce)";
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Wed = 0;
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Wgd = weight_scale;
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}
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} else { // Subcase b: R+D >= S
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casename = "Case 2b1 (Wgg=1, Wmd=Wgd)";
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Wee = (weight_scale*(E - G + M))/E;
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Wed = (weight_scale*(D - 2*E + 4*G - 2*M))/(3*D);
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Wme = (weight_scale*(G-M))/E;
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Wmg = 0;
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Wgg = weight_scale;
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Wmd = (weight_scale - Wed)/2;
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Wgd = (weight_scale - Wed)/2;
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berr = networkstatus_check_weights(Wgg, Wgd, Wmg, Wme, Wmd, Wee, Wed,
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weight_scale, G, M, E, D, T, 10, 1);
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if (berr) {
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casename = "Case 2b2 (Wgg=1, Wee=1)";
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Wgg = weight_scale;
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Wee = weight_scale;
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Wed = (weight_scale*(D - 2*E + G + M))/(3*D);
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Wmd = (weight_scale*(D - 2*M + G + E))/(3*D);
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Wme = 0;
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Wmg = 0;
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if (Wmd < 0) { // Can happen if M > T/3
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casename = "Case 2b3 (Wmd=0)";
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Wmd = 0;
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log_warn(LD_DIR,
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"Too much Middle bandwidth on the network to calculate "
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"balanced bandwidth-weights. Consider increasing the "
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"number of Guard nodes by lowering the requirements.");
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}
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Wgd = weight_scale - Wed - Wmd;
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berr = networkstatus_check_weights(Wgg, Wgd, Wmg, Wme, Wmd, Wee,
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Wed, weight_scale, G, M, E, D, T, 10, 1);
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}
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if (berr != BW_WEIGHTS_NO_ERROR &&
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berr != BW_WEIGHTS_BALANCE_MID_ERROR) {
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log_warn(LD_DIR,
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"Bw Weights error %d for %s v10. G="I64_FORMAT" M="I64_FORMAT
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" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT
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" Wmd=%d Wme=%d Wmg=%d Wed=%d Wee=%d"
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" Wgd=%d Wgg=%d Wme=%d Wmg=%d weight_scale=%d",
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berr, casename,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T),
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(int)Wmd, (int)Wme, (int)Wmg, (int)Wed, (int)Wee,
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(int)Wgd, (int)Wgg, (int)Wme, (int)Wmg, (int)weight_scale);
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return 0;
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}
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}
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} else { // if (E < T/3 || G < T/3) {
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int64_t S = MIN(E, G);
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// Case 3: Exactly one of Guard or Exit is scarce
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if (!(3*E < T || 3*G < T) || !(3*G >= T || 3*E >= T)) {
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log_warn(LD_BUG,
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"Bw-Weights Case 3 v10 but with G="I64_FORMAT" M="
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I64_FORMAT" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T));
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}
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if (3*(S+D) < T) { // Subcase a: S+D < T/3
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if (G < E) {
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casename = "Case 3a (G scarce)";
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Wgg = Wgd = weight_scale;
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Wmd = Wed = Wmg = 0;
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// Minor subcase, if E is more scarce than M,
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// keep its bandwidth in place.
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if (E < M) Wme = 0;
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else Wme = (weight_scale*(E-M))/(2*E);
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Wee = weight_scale-Wme;
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} else { // G >= E
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casename = "Case 3a (E scarce)";
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Wee = Wed = weight_scale;
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Wmd = Wgd = Wme = 0;
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// Minor subcase, if G is more scarce than M,
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// keep its bandwidth in place.
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if (G < M) Wmg = 0;
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else Wmg = (weight_scale*(G-M))/(2*G);
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Wgg = weight_scale-Wmg;
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}
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} else { // Subcase b: S+D >= T/3
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// D != 0 because S+D >= T/3
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if (G < E) {
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casename = "Case 3bg (G scarce, Wgg=1, Wmd == Wed)";
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Wgg = weight_scale;
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Wgd = (weight_scale*(D - 2*G + E + M))/(3*D);
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Wmg = 0;
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Wee = (weight_scale*(E+M))/(2*E);
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Wme = weight_scale - Wee;
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Wmd = (weight_scale - Wgd)/2;
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Wed = (weight_scale - Wgd)/2;
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berr = networkstatus_check_weights(Wgg, Wgd, Wmg, Wme, Wmd, Wee,
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Wed, weight_scale, G, M, E, D, T, 10, 1);
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} else { // G >= E
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casename = "Case 3be (E scarce, Wee=1, Wmd == Wgd)";
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Wee = weight_scale;
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Wed = (weight_scale*(D - 2*E + G + M))/(3*D);
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Wme = 0;
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Wgg = (weight_scale*(G+M))/(2*G);
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Wmg = weight_scale - Wgg;
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Wmd = (weight_scale - Wed)/2;
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Wgd = (weight_scale - Wed)/2;
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berr = networkstatus_check_weights(Wgg, Wgd, Wmg, Wme, Wmd, Wee,
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Wed, weight_scale, G, M, E, D, T, 10, 1);
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}
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if (berr) {
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log_warn(LD_DIR,
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"Bw Weights error %d for %s v10. G="I64_FORMAT" M="I64_FORMAT
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" E="I64_FORMAT" D="I64_FORMAT" T="I64_FORMAT
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" Wmd=%d Wme=%d Wmg=%d Wed=%d Wee=%d"
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" Wgd=%d Wgg=%d Wme=%d Wmg=%d weight_scale=%d",
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berr, casename,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T),
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(int)Wmd, (int)Wme, (int)Wmg, (int)Wed, (int)Wee,
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(int)Wgd, (int)Wgg, (int)Wme, (int)Wmg, (int)weight_scale);
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return 0;
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}
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}
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}
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/* We cast down the weights to 32 bit ints on the assumption that
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* weight_scale is ~= 10000. We need to ensure a rogue authority
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* doesn't break this assumption to rig our weights */
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tor_assert(0 < weight_scale && weight_scale < INT32_MAX);
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/*
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* Provide Wgm=Wgg, Wmm=1, Wem=Wee, Weg=Wed. May later determine
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* that middle nodes need different bandwidth weights for dirport traffic,
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* or that weird exit policies need special weight, or that bridges
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* need special weight.
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*
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* NOTE: This list is sorted.
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*/
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r = tor_snprintf(buf, sizeof(buf),
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"bandwidth-weights Wbd=%d Wbe=%d Wbg=%d Wbm=%d "
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"Wdb=%d "
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"Web=%d Wed=%d Wee=%d Weg=%d Wem=%d "
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"Wgb=%d Wgd=%d Wgg=%d Wgm=%d "
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"Wmb=%d Wmd=%d Wme=%d Wmg=%d Wmm=%d\n",
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(int)Wmd, (int)Wme, (int)Wmg, (int)weight_scale,
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(int)weight_scale,
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(int)weight_scale, (int)Wed, (int)Wee, (int)Wed, (int)Wee,
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(int)weight_scale, (int)Wgd, (int)Wgg, (int)Wgg,
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(int)weight_scale, (int)Wmd, (int)Wme, (int)Wmg, (int)weight_scale);
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if (r<0) {
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log_warn(LD_BUG,
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"Not enough space in buffer for bandwidth-weights line.");
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*buf = '\0';
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return 0;
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}
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smartlist_add(chunks, tor_strdup(buf));
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log_notice(LD_CIRC, "Computed bandwidth weights for %s with v10: "
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"G="I64_FORMAT" M="I64_FORMAT" E="I64_FORMAT" D="I64_FORMAT
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" T="I64_FORMAT,
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casename,
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I64_PRINTF_ARG(G), I64_PRINTF_ARG(M), I64_PRINTF_ARG(E),
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I64_PRINTF_ARG(D), I64_PRINTF_ARG(T));
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return 1;
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}
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/**
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* This function computes the bandwidth weights for consensus method 9.
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*
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* It has been obsoleted in favor of consensus method 10.
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*/
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static void
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networkstatus_compute_bw_weights_v9(smartlist_t *chunks, int64_t G, int64_t M,
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int64_t E, int64_t D, int64_t T,
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@ -1064,7 +1324,7 @@ networkstatus_compute_bw_weights_v9(smartlist_t *chunks, int64_t G, int64_t M,
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*buf = '\0';
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}
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smartlist_add(chunks, tor_strdup(buf));
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log_notice(LD_CIRC, "Computed bandwidth weights for %s: "
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log_notice(LD_CIRC, "Computed bandwidth weights for %s with v9: "
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"G="I64_FORMAT" M="I64_FORMAT" E="I64_FORMAT" D="I64_FORMAT
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" T="I64_FORMAT,
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casename,
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@ -1101,6 +1361,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
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const routerstatus_format_type_t rs_format =
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flavor == FLAV_NS ? NS_V3_CONSENSUS : NS_V3_CONSENSUS_MICRODESC;
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char *params = NULL;
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int added_weights = 0;
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tor_assert(flavor == FLAV_NS || flavor == FLAV_MICRODESC);
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tor_assert(total_authorities >= smartlist_len(votes));
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@ -1783,7 +2044,13 @@ networkstatus_compute_consensus(smartlist_t *votes,
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}
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}
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networkstatus_compute_bw_weights_v9(chunks, G, M, E, D, T, weight_scale);
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if (consensus_method < 10) {
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networkstatus_compute_bw_weights_v9(chunks, G, M, E, D, T, weight_scale);
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added_weights = 1;
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} else {
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added_weights = networkstatus_compute_bw_weights_v10(chunks, G, M, E, D,
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T, weight_scale);
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}
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}
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/* Add a signature. */
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@ -1873,7 +2140,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
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return NULL;
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}
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// Verify balancing parameters
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if (consensus_method >= MIN_METHOD_FOR_BW_WEIGHTS) {
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if (consensus_method >= MIN_METHOD_FOR_BW_WEIGHTS && added_weights) {
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networkstatus_verify_bw_weights(c);
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}
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networkstatus_vote_free(c);
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