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Fix emargo timeout in dandelion++
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@ -68,4 +68,30 @@ namespace crypto
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//! Generate random duration with 1/4 second precision
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using random_poisson_subseconds =
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random_poisson_duration<std::chrono::duration<std::chrono::milliseconds::rep, std::ratio<1, 4>>>;
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template<typename D>
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struct random_exponential_duration
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{
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using result_type = D;
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using rep = typename result_type::rep;
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explicit random_exponential_duration(double rate)
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: dist(rate)
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{}
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result_type operator()()
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{
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/* Note this always rounds down to nearest whole number. if `std::lround`
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was used instead, then 0 seconds would be used less frequently. Not sure
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which is better, since we cannot broadcast on sub-seconds intervals. */
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crypto::random_device rand{};
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return result_type{rep(dist(rand))};
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}
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private:
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std::exponential_distribution<double> dist;
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};
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using random_exponential_seconds = random_exponential_duration<std::chrono::seconds>;
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}
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@ -104,11 +104,12 @@
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#define CRYPTONOTE_DANDELIONPP_STEMS 2 // number of outgoing stem connections per epoch
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#define CRYPTONOTE_DANDELIONPP_FLUFF_PROBABILITY 20 // out of 100
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#define CRYPTONOTE_DANDELIONPP_FLUFF_PROBABILITY 12 // out of 100
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#define CRYPTONOTE_DANDELIONPP_MIN_EPOCH 10 // minutes
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#define CRYPTONOTE_DANDELIONPP_EPOCH_RANGE 30 // seconds
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#define CRYPTONOTE_DANDELIONPP_FLUSH_AVERAGE 5 // seconds average for poisson distributed fluff flush
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#define CRYPTONOTE_DANDELIONPP_EMBARGO_AVERAGE 39 // seconds (see tx_pool.cpp for more info)
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#define CRYPTONOTE_DANDELIONPP_EMBARGO_RATE double(1)/double(46.5) // seconds (see tx_pool.cpp for more info)
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#define CRYPTONOTE_DANDELIONPP_EMBARGO_MAX 180 // seconds
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// see src/cryptonote_protocol/levin_notify.cpp
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#define CRYPTONOTE_NOISE_MIN_EPOCH 5 // minutes
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@ -58,28 +58,27 @@ namespace cryptonote
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{
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namespace
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{
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/*! The Dandelion++ has formula for calculating the average embargo timeout:
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(-k*(k-1)*hop)/(2*log(1-ep))
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where k is the number of hops before this node and ep is the probability
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that one of the k hops hits their embargo timer, and hop is the average
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time taken between hops. So decreasing ep will make it more probable
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that "this" node is the first to expire the embargo timer. Increasing k
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will increase the number of nodes that will be "hidden" as a prior
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recipient of the tx.
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/*! The Dandelion++ has formula for calculating the embargo rate:
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(-k*(k-1)*hop)/(2*ln(1-ep))
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where k is the number of hops before the fluff node and ep is the
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probability that one of the k hops hits their embargo timer before
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reaching the fluff node, and hop is the average time taken between hops.
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As example, k=5 and ep=0.1 means "this" embargo timer has a 90%
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probability of being the first to expire amongst 5 nodes that saw the
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tx before "this" one. These values are independent to the fluff
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probability, but setting a low k with a low p (fluff probability) is
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not ideal since a blackhole is more likely to reveal earlier nodes in
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the chain.
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NOTE: The paper says `2*log(1-ep)`, however if you read the explanation
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in b.5 it is clear they meant `ln`.
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This value was calculated with k=5, ep=0.10, and hop = 175 ms. A
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As example, k=10 and ep=0.1 means "this" embargo timer has a 90%
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probability of reaching 10 hops before the embargo timer fires. These
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values are independent to the fluff probability.
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The embargo rate was calculated with k=8, ep=0.1, and hop = 175 ms. A
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testrun from a recent Intel laptop took ~80ms to
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receive+parse+proces+send transaction. At least 50ms will be added to
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the latency if crossing an ocean. So 175ms is the fudge factor for
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a single hop with 39s being the embargo timer. */
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constexpr const std::chrono::seconds dandelionpp_embargo_average{CRYPTONOTE_DANDELIONPP_EMBARGO_AVERAGE};
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a single hop with 1/46.5 being the embargo _rate_. The average time
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to blackhole fluff will be 46.5/hops where hops is the number of hops
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before being blackholed. */
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// see cryptonote_config.h CRYPTONOTE_DANDELIONPP_EMBARGO_RATE
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//TODO: constants such as these should at least be in the header,
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// but probably somewhere more accessible to the rest of the
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@ -889,7 +888,7 @@ namespace cryptonote
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{
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just_broadcasted.clear();
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crypto::random_poisson_seconds embargo_duration{dandelionpp_embargo_average};
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crypto::random_exponential_seconds embargo_duration{CRYPTONOTE_DANDELIONPP_EMBARGO_RATE};
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const auto now = std::chrono::system_clock::now();
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uint64_t next_relay = uint64_t{std::numeric_limits<time_t>::max()};
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@ -911,7 +910,12 @@ namespace cryptonote
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if (meta.dandelionpp_stem)
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{
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meta.last_relayed_time = std::chrono::system_clock::to_time_t(now + embargo_duration());
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// if `embargo_duration() == 0`, the next `on_idle()` will broadcast
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// the tx.
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meta.last_relayed_time =
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std::chrono::system_clock::to_time_t(
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now + std::min(std::chrono::seconds{CRYPTONOTE_DANDELIONPP_EMBARGO_MAX}, embargo_duration())
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);
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next_relay = std::min(next_relay, meta.last_relayed_time);
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}
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else
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@ -74,7 +74,6 @@ namespace levin
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5000 milliseconds is given, 95% of the values fall between 4859ms-5141ms
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in 1ms increments (not enough time variance). Providing 20 quarter
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seconds yields 95% of the values between 3s-7.25s in 1/4s increments. */
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using fluff_stepsize = std::chrono::duration<std::chrono::milliseconds::rep, std::ratio<1, 4>>;
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constexpr const std::chrono::seconds fluff_average_in{CRYPTONOTE_DANDELIONPP_FLUSH_AVERAGE};
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/*! Bitcoin Core is using 1/2 average seconds for outgoing connections
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