filetransfer: abort transfer on receiver exception

not doing this will cause transfers that had their readers disappear to
linger. with lingering transfers the curl thread can't shut down, which
will cause nix itself to not shut down until the transfer finishes some
other way (most likely network timeouts). also add a new test for this.

Change-Id: Id2401b3ac85731c824db05918d4079125be25b57

1 files changed, 9 insertions, 7 deletions

diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index c9f5d6260..aa8f4be1d 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -708,7 +708,7 @@ struct curlFileTransfer : public FileTransfer
            download thread and the calling thread. */
 
         struct State {
-            bool quit = false;
+            bool done = false, failed = false;
             std::exception_ptr exc;
             std::string data;
             std::condition_variable avail, request;
@@ -717,18 +717,17 @@ struct curlFileTransfer : public FileTransfer
 
         auto _state = std::make_shared<Sync<State>>();
 
-        /* In case of an exception, wake up the download thread. FIXME:
-           abort the download request. */
+        /* In case of an exception, wake up the download thread. */
         Finally finally([&]() {
             auto state(_state->lock());
-            state->quit = true;
+            state->failed |= std::uncaught_exceptions() != 0;
             state->request.notify_one();
         });
 
         enqueueFileTransfer(request,
             {[_state](std::future<FileTransferResult> fut) {
                 auto state(_state->lock());
-                state->quit = true;
+                state->done = true;
                 try {
                     fut.get();
                 } catch (...) {
@@ -740,7 +739,10 @@ struct curlFileTransfer : public FileTransfer
             [_state, &sink](TransferItem & transfer, std::string_view data) {
                 auto state(_state->lock());
 
-                if (state->quit) return;
+                if (state->failed) {
+                    // actual exception doesn't matter, the other end is already dead
+                    throw std::exception{};
+                }
 
                 if (!state->decompressor) {
                     state->decompressor = makeDecompressionSink(transfer.encoding, sink);
@@ -775,7 +777,7 @@ struct curlFileTransfer : public FileTransfer
 
                 if (state->data.empty()) {
 
-                    if (state->quit) {
+                    if (state->done) {
                         if (state->exc) std::rethrow_exception(state->exc);
                         if (state->decompressor) {
                             state->decompressor->finish();