From 095bad65689e623fa7aba6978ef196e54216022b Mon Sep 17 00:00:00 2001
From: Yat Ho <lagoho7@gmail.com>
Date: Tue, 9 Dec 2025 05:43:56 +0800
Subject: [PATCH] fix: check if piece is wanted upon receiving block (#7866)

* fix: check if piece is wanted upon receiving block

* test: block_last_loc
---
 libtransmission/block-info.h             |  6 ++++
 libtransmission/peer-msgs.cc             | 16 +++++++----
 libtransmission/torrent-metainfo.h       |  4 +++
 libtransmission/torrent.h                |  4 +++
 tests/libtransmission/block-info-test.cc | 35 ++++++++++++++++++++++++
 5 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/libtransmission/block-info.h b/libtransmission/block-info.h
index 02696b895..64ce23de6 100644
--- a/libtransmission/block-info.h
+++ b/libtransmission/block-info.h
@@ -97,6 +97,12 @@ public:
         return byte_loc(uint64_t{ block } * BlockSize);
     }
 
+    // Location of the last byte in `block`.
+    [[nodiscard]] constexpr auto block_last_loc(tr_block_index_t const block) const noexcept
+    {
+        return byte_loc((uint64_t{ block } * BlockSize) + block_size(block) - 1U);
+    }
+
     // Location of the first byte (+ optional offset and length) in `piece`
     [[nodiscard]] constexpr auto piece_loc(tr_piece_index_t piece, uint32_t offset = {}, uint32_t length = {}) const noexcept
     {
diff --git a/libtransmission/peer-msgs.cc b/libtransmission/peer-msgs.cc
index cfb1966d8..c7aad71b1 100644
--- a/libtransmission/peer-msgs.cc
+++ b/libtransmission/peer-msgs.cc
@@ -1688,18 +1688,22 @@ ReadResult tr_peerMsgsImpl::read_piece_data(MessageReader& payload)
         return { ReadState::Err, len };
     }
 
-    if (!active_requests.test(block))
-    {
-        logwarn(this, fmt::format("got unrequested block {:d} ({:d}:{:d}->{:d})", block, piece, offset, len));
-        return { ReadState::Err, len };
-    }
-
     if (tor_.has_block(block))
     {
         logtrace(this, fmt::format("got completed block {:d} ({:d}:{:d}->{:d})", block, piece, offset, len));
         return { ReadState::Err, len };
     }
 
+    if (auto const block_loc = tor_.block_loc(block); !tor_.piece_is_wanted(block_loc.piece))
+    {
+        if (auto const block_last_loc = tor_.block_last_loc(block);
+            block_loc.piece == block_last_loc.piece || !tor_.piece_is_wanted(block_last_loc.piece))
+        {
+            logwarn(this, fmt::format("got unwanted block {:d} ({:d}:{:d}->{:d})", block, piece, offset, len));
+            return { ReadState::Err, len };
+        }
+    }
+
     peer_info->set_latest_piece_data_time(tr_time());
     bytes_sent_to_client.add(tr_time(), len);
     publish(tr_peer_event::GotPieceData(len));
diff --git a/libtransmission/torrent-metainfo.h b/libtransmission/torrent-metainfo.h
index 7f14d236d..0c7c9ffe5 100644
--- a/libtransmission/torrent-metainfo.h
+++ b/libtransmission/torrent-metainfo.h
@@ -79,6 +79,10 @@ public:
     {
         return block_info().block_loc(block);
     }
+    [[nodiscard]] constexpr auto block_last_loc(tr_block_index_t block) const noexcept
+    {
+        return block_info().block_last_loc(block);
+    }
     [[nodiscard]] constexpr auto piece_loc(tr_piece_index_t piece, uint32_t offset = 0, uint32_t length = 0) const noexcept
     {
         return block_info().piece_loc(piece, offset, length);
diff --git a/libtransmission/torrent.h b/libtransmission/torrent.h
index 12703ed28..108dfd71f 100644
--- a/libtransmission/torrent.h
+++ b/libtransmission/torrent.h
@@ -267,6 +267,10 @@ struct tr_torrent
     {
         return metainfo_.block_loc(block);
     }
+    [[nodiscard]] constexpr auto block_last_loc(tr_block_index_t block) const noexcept
+    {
+        return metainfo_.block_last_loc(block);
+    }
     [[nodiscard]] constexpr auto piece_loc(tr_piece_index_t piece, uint32_t offset = 0, uint32_t length = 0) const noexcept
     {
         return metainfo_.piece_loc(piece, offset, length);
diff --git a/tests/libtransmission/block-info-test.cc b/tests/libtransmission/block-info-test.cc
index 59a014426..f74e95335 100644
--- a/tests/libtransmission/block-info-test.cc
+++ b/tests/libtransmission/block-info-test.cc
@@ -136,6 +136,41 @@ TEST_F(BlockInfoTest, blockLoc)
     EXPECT_EQ(0U, loc.piece_offset);
 }
 
+TEST_F(BlockInfoTest, blockLastLoc)
+{
+    static auto constexpr ExpectedBlockSize = uint64_t{ 1024U } * 16U;
+    static auto constexpr ExpectedBlocksPerPiece = uint64_t{ 4U };
+    static auto constexpr PieceSize = ExpectedBlockSize * ExpectedBlocksPerPiece;
+    static auto constexpr PieceCount = uint64_t{ 5U };
+    static auto constexpr TotalSize = (PieceSize * (PieceCount - 1U)) + 1U;
+
+    auto const info = tr_block_info{ TotalSize, PieceSize };
+
+    // begin
+    auto loc = info.block_last_loc(0);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.byte);
+    EXPECT_EQ(0U, loc.block);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.block_offset);
+    EXPECT_EQ(0U, loc.piece);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.piece_offset);
+
+    // third block is halfway through the first piece
+    loc = info.block_last_loc(2);
+    EXPECT_EQ((ExpectedBlockSize * 3U) - 1U, loc.byte);
+    EXPECT_EQ(2U, loc.block);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.block_offset);
+    EXPECT_EQ(0U, loc.piece);
+    EXPECT_EQ((ExpectedBlockSize * 3U) - 1U, loc.piece_offset);
+
+    // second piece aligns with fifth block
+    loc = info.block_last_loc(4);
+    EXPECT_EQ(PieceSize + ExpectedBlockSize - 1U, loc.byte);
+    EXPECT_EQ(4U, loc.block);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.block_offset);
+    EXPECT_EQ(1U, loc.piece);
+    EXPECT_EQ(ExpectedBlockSize - 1U, loc.piece_offset);
+}
+
 TEST_F(BlockInfoTest, pieceLoc)
 {
     static auto constexpr ExpectedBlockSize = uint64_t{ 1024U } * 16U;