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XMoveFunds: on FEE_INSUFFICIENT, exclude the incoming channel, not the outgoing
A FEE_INSUFFICIENT at a forwarding node means the node required more than we paid, where its required fee is outbound_fee(outgoing channel) + inbound_fee(incoming channel). The onion error names and carries the policy for the node's OUTGOING channel only; the inbound fee that actually causes the shortfall lives on the INCOMING channel (route[erring_index-1]) and is not in the payload. The previous code keyed off the outgoing channel's own inbound-fee TLV and excluded the outgoing channel -- the wrong edge -- and only worked by luck when the node set positive inbound fees broadly or when no channel_update was present. Replace that with discriminating logic for failcode 0x100c: - Compute the fee we allocated at the erring hop (amount_in - amount_out). - If the error carried a channel_update, compute the outgoing channel's required outbound fee (base + prop*amount_out/1e6). - If we already paid the outbound fee (allocated >= required_out) but still failed, the shortfall is the inbound fee on the incoming channel: hard-exclude route[erring_index-1] with inform_channel_constrained(amount=1) -> max_msat=0. This is a self-aging constraint, so it recovers automatically if the peer later drops the inbound fee. - If we underpaid the outbound fee (allocated < required_out), it is a stale outbound policy: refresh the outgoing channel from the channel_update. - If there is no channel_update to compare, treat it as the inbound case and exclude the incoming channel (a plain stale-outbound failure normally carries the update). This also covers the terminally-failed-MPP-part case where waitsendpay omits raw_message. - Never self-exclude one of our own channels; fall through if the incoming hop is local. Other policy-carrying failcodes (amount_below_minimum, incorrect_cltv_expiry, expiry_too_soon) still refresh the outgoing channel, since those genuinely concern the outgoing channel's published policy. Needs prod1 retest against the cyberdyne/Tachyon positive-inbound paths.
This commit is contained in:
Ken Sedgwick
parent
b844a4f146
commit
118a722b32
1 changed files with 96 additions and 23 deletions
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@ -1244,15 +1244,104 @@ private:
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return;
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}
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/* Policy-carrying failcodes: try to refresh
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* the forwarder's published policy from the
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* embedded channel_update. Applies even to
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* our local-channel scids (the failing
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* direction is the peer's outbound, gossip-
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* derived). */
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/* FEE_INSUFFICIENT (0x100c): the required fee at the
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* erring node is outbound_fee(erring/OUTGOING channel) +
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* inbound_fee(INCOMING channel). The error names and
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* carries the policy for the OUTGOING channel only, so we
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* must decide which side is actually at fault:
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* - if we already paid the outgoing channel's advertised
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* outbound fee (allocated >= required_out) yet still
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* failed, the shortfall is the INBOUND fee on the
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* incoming channel route[eidx-1] -> hard-exclude that
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* channel (a max_msat=0 constraint that self-ages, so it
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* recovers if the peer later drops the inbound fee);
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* - if we underpaid the outbound fee (allocated <
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* required_out), it is a stale outbound policy -> refresh
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* the outgoing channel from the embedded channel_update;
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* - no channel_update to compare -> treat as the inbound
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* case (a plain stale-outbound failure normally carries
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* the update) and exclude the incoming channel.
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* NB: the OUTGOING channel's own inbound-fee TLV is NOT the
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* fee that bit us (that is the incoming channel's), so we no
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* longer key off it. */
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if (fail == 0x100c) {
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/* fee we allocated at the erring (outgoing) hop */
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auto alloc = std::uint64_t(0);
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if (eidx < askrene_path.size()
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&& askrene_path[eidx].has("amount_in_msat")
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&& askrene_path[eidx].has("amount_out_msat")) {
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auto in = Ln::Amount::object(
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askrene_path[eidx]["amount_in_msat"]).to_msat();
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auto out = Ln::Amount::object(
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askrene_path[eidx]["amount_out_msat"]).to_msat();
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alloc = (in >= out) ? in - out : std::uint64_t(0);
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}
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ChanUpdate cu;
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auto have_cu = data.has("raw_message")
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&& eidx < askrene_path.size()
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&& askrene_path[eidx].has("amount_out_msat")
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&& parse_chan_update(
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std::string(data["raw_message"]), cu);
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auto outbound_satisfied = true;
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if (have_cu) {
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auto out = Ln::Amount::object(
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askrene_path[eidx]["amount_out_msat"]).to_msat();
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auto required_out =
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std::uint64_t(cu.fee_base_msat)
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+ std::uint64_t(
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cu.fee_proportional_millionths)
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* out / 1000000;
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outbound_satisfied = (alloc >= required_out);
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}
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/* Inbound-fee case: exclude the INCOMING channel
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* route[eidx-1], unless it is one of our own channels
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* (auto.localchans owns those; never self-exclude). */
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if (outbound_satisfied && eidx >= 1
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&& (eidx - 1) < askrene_path.size()
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&& askrene_path[eidx - 1].has("short_channel_id_dir")) {
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auto scidd = std::string(
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askrene_path[eidx - 1]["short_channel_id_dir"]);
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auto slash = scidd.find('/');
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auto in_scid = scidd.substr(0, slash);
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if (!our_scids.count(in_scid)) {
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auto in_dir = std::uint32_t(std::stoul(
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scidd.substr(slash + 1)));
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actions.push_back(
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Boss::Mod::AskreneLayer::
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inform_channel_constrained(
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*rpc,
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Boss::Mod::AskreneLayer::
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xrebalance_layer_name,
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Ln::Scid(in_scid), in_dir,
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Ln::Amount::msat(1)));
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return;
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}
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}
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/* Stale outbound fee: refresh the outgoing channel. */
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if (have_cu) {
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actions.push_back(
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Boss::Mod::AskreneLayer::update_channel(
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*rpc,
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Boss::Mod::AskreneLayer::
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xrebalance_layer_name,
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Ln::Scid(echan_str), edir,
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cu.enabled,
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Ln::Amount::msat(cu.htlc_minimum_msat),
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Ln::Amount::msat(cu.htlc_maximum_msat),
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Ln::Amount::msat(cu.fee_base_msat),
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cu.fee_proportional_millionths,
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cu.cltv_expiry_delta));
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return;
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}
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/* else: fall through to the capacity constraint. */
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}
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/* Other policy-carrying failcodes (amount_below_minimum,
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* incorrect_cltv_expiry, expiry_too_soon) genuinely concern
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* the OUTGOING channel's published policy -- refresh it from
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* the embedded channel_update. */
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auto policy_carrying =
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fail == 0x100b
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|| fail == 0x100c
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|| fail == 0x100d
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|| fail == 0x100e;
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if (policy_carrying && data.has("raw_message")) {
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@ -1260,22 +1349,6 @@ private:
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std::string(data["raw_message"]);
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ChanUpdate cu;
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if (parse_chan_update(raw, cu)) {
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/* Positive inbound fee: askrene cannot
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* price it, so applying the update just
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* loops. Exclude the channel instead. */
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if (cu.has_inbound_fee
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&& (cu.inbound_fee_base_msat > 0
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|| cu.inbound_fee_proportional_millionths > 0)) {
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actions.push_back(
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Boss::Mod::AskreneLayer::
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inform_channel_constrained(
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*rpc,
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Boss::Mod::AskreneLayer::
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xrebalance_layer_name,
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Ln::Scid(echan_str), edir,
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Ln::Amount::msat(1)));
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return;
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}
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actions.push_back(
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Boss::Mod::AskreneLayer::
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update_channel(
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