@chainsafe/libp2p-gossipsub/dist/src/score/compute-score.js

A typescript implementation of gossipsub

export function computeScore(peer, pstats, params, peerIPs) {
    let score = 0;
    // topic stores
    Object.entries(pstats.topics).forEach(([topic, tstats]) => {
        // the topic parameters
        const topicParams = params.topics[topic];
        if (topicParams === undefined) {
            // we are not scoring this topic
            return;
        }
        let topicScore = 0;
        // P1: time in Mesh
        if (tstats.inMesh) {
            let p1 = tstats.meshTime / topicParams.timeInMeshQuantum;
            if (p1 > topicParams.timeInMeshCap) {
                p1 = topicParams.timeInMeshCap;
            }
            topicScore += p1 * topicParams.timeInMeshWeight;
        }
        // P2: first message deliveries
        let p2 = tstats.firstMessageDeliveries;
        if (p2 > topicParams.firstMessageDeliveriesCap) {
            p2 = topicParams.firstMessageDeliveriesCap;
        }
        topicScore += p2 * topicParams.firstMessageDeliveriesWeight;
        // P3: mesh message deliveries
        if (tstats.meshMessageDeliveriesActive &&
            tstats.meshMessageDeliveries < topicParams.meshMessageDeliveriesThreshold) {
            const deficit = topicParams.meshMessageDeliveriesThreshold - tstats.meshMessageDeliveries;
            const p3 = deficit * deficit;
            topicScore += p3 * topicParams.meshMessageDeliveriesWeight;
        }
        // P3b:
        // NOTE: the weight of P3b is negative (validated in validateTopicScoreParams) so this detracts
        const p3b = tstats.meshFailurePenalty;
        topicScore += p3b * topicParams.meshFailurePenaltyWeight;
        // P4: invalid messages
        // NOTE: the weight of P4 is negative (validated in validateTopicScoreParams) so this detracts
        const p4 = tstats.invalidMessageDeliveries * tstats.invalidMessageDeliveries;
        topicScore += p4 * topicParams.invalidMessageDeliveriesWeight;
        // update score, mixing with topic weight
        score += topicScore * topicParams.topicWeight;
    });
    // apply the topic score cap, if any
    if (params.topicScoreCap > 0 && score > params.topicScoreCap) {
        score = params.topicScoreCap;
    }
    // P5: application-specific score
    const p5 = params.appSpecificScore(peer);
    score += p5 * params.appSpecificWeight;
    // P6: IP colocation factor
    pstats.knownIPs.forEach((ip) => {
        if (params.IPColocationFactorWhitelist.has(ip)) {
            return;
        }
        // P6 has a cliff (IPColocationFactorThreshold)
        // It's only applied if at least that many peers are connected to us from that source IP addr.
        // It is quadratic, and the weight is negative (validated in validatePeerScoreParams)
        const peersInIP = peerIPs.get(ip);
        const numPeersInIP = (peersInIP != null) ? peersInIP.size : 0;
        if (numPeersInIP > params.IPColocationFactorThreshold) {
            const surplus = numPeersInIP - params.IPColocationFactorThreshold;
            const p6 = surplus * surplus;
            score += p6 * params.IPColocationFactorWeight;
        }
    });
    // P7: behavioural pattern penalty
    if (pstats.behaviourPenalty > params.behaviourPenaltyThreshold) {
        const excess = pstats.behaviourPenalty - params.behaviourPenaltyThreshold;
        const p7 = excess * excess;
        score += p7 * params.behaviourPenaltyWeight;
    }
    return score;
}
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