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Support HTLC interception by source channel#4338

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TheBlueMatt wants to merge 2 commits intolightningdevkit:mainfrom
TheBlueMatt:2026-01-intercept-by-source-v2
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Support HTLC interception by source channel#4338
TheBlueMatt wants to merge 2 commits intolightningdevkit:mainfrom
TheBlueMatt:2026-01-intercept-by-source-v2

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@TheBlueMatt TheBlueMatt commented Jan 23, 2026 •
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Just a few more flags and a small cleanup.

Based on #4300

@TheBlueMatt TheBlueMatt requested a review from tnull January 23, 2026 02:21
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ldk-reviews-bot commented Jan 26, 2026

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@tnull tnull removed their request for review January 27, 2026 10:22
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Please re-request review once #4300 lands and this is rebased.

@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from b793c1e to 79952e1 Compare January 28, 2026 14:11
@TheBlueMatt TheBlueMatt requested a review from tnull January 28, 2026 14:11
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TheBlueMatt commented Jan 28, 2026

Rebased.

@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from 79952e1 to 779fce3 Compare January 28, 2026 14:14
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Seems CI is very unhappy as this doesn't build currently.

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@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from 779fce3 to 0bf2200 Compare January 29, 2026 15:03
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TheBlueMatt commented Jan 29, 2026

Oops, silent conflict.

@TheBlueMatt TheBlueMatt requested a review from tnull January 29, 2026 15:03
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codecov bot commented Jan 29, 2026 •
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Codecov Report

❌ Patch coverage is 93.75000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.89%. Comparing base (3497b59) to head (9a9531f).
⚠️ Report is 10 commits behind head on main.

Files with missing lines Patch % Lines
lightning/src/ln/channelmanager.rs 93.75% 5 Missing and 1 partial ⚠️
Additional details and impacted files 
@@            Coverage Diff             @@
##             main    #4338      +/-   ##
==========================================
- Coverage   86.09%   85.89%   -0.20%     
==========================================
  Files         156      156              
  Lines      103623   103958     +335     
  Branches   103623   103958     +335     
==========================================
+ Hits        89211    89299      +88     
- Misses      11895    12139     +244     
- Partials     2517     2520       +3
Flag Coverage Δ
tests 85.89% <93.75%> (-0.20%) ⬇️

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ldk-reviews-bot commented Jan 31, 2026

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ldk-reviews-bot commented Feb 2, 2026

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rustfmt is unhappy but code changes look good to me

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ldk-reviews-bot commented Feb 4, 2026

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ldk-reviews-bot commented Feb 7, 2026

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@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from 0bf2200 to f6ecc61 Compare February 7, 2026 16:51
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fixups lgtm

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LGTM, feel free to squash.

@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from f6ecc61 to c4ae026 Compare February 12, 2026 15:16
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TheBlueMatt commented Feb 12, 2026

Squashed without any further changes.

@TheBlueMatt TheBlueMatt requested a review from tnull February 12, 2026 15:16
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ldk-reviews-bot commented Feb 12, 2026

✅ Added second reviewer: @tankyleo

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TheBlueMatt commented Feb 17, 2026

Rebased to address conflict.

@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from c4ae026 to ec84d55 Compare February 17, 2026 18:28
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@tankyleo tankyleo requested a review from tnull February 17, 2026 22:51
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Pass constructed PendingAddHTLCInfo to chanman forward_htlcs
113f9cb 
We jump through some hoops in order to pass a small list of objects
to `forward_htlcs` on a per-channel basis rather than per-HTLC.
Then, `forward_htlcs` builds a `PendingAddHTLCInfo` for each HTLC
for insertion. Worse, in some `forward_htlcs` callsites we're
actually starting with a `PendingAddHTLCInfo`, converting it to a
tuple, then back inside `forward_htlcs`.

Instead, here we just pass a list of built `PendingAddHTLCInfo`s to
`forward_htlcs`, cleaning up a good bit of code and even avoiding
an allocation of the HTLCs vec in many cases.
@TheBlueMatt
Allow intercepting HTLCs based on the source channel
9a9531f 
It may be useful in some situations to select HTLCs for
interception based on the source channel in addition to the sink.
Here we add the ability to do so by adding new flags to
`HTLCInterceptionFlags`.
@TheBlueMatt TheBlueMatt force-pushed the 2026-01-intercept-by-source-v2 branch from ec84d55 to 9a9531f Compare February 18, 2026 00:05
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TheBlueMatt commented Feb 18, 2026

Grr, rebase broke rustfmt:

$ git diff-tree -U1 ec84d5549 9a9531f3c
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index a013b1905d..b417e023f4 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -9578,4 +9578,3 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		user_channel_id: u128, unbroadcasted_batch_funding_txid: Option<Txid>,
-		update_actions: Vec<MonitorUpdateCompletionAction>,
-		htlc_forwards: Vec<PendingAddHTLCInfo>,
+		update_actions: Vec<MonitorUpdateCompletionAction>, htlc_forwards: Vec<PendingAddHTLCInfo>,
 		decode_update_add_htlcs: Option<(u64, Vec<msgs::UpdateAddHTLC>)>,

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