82 lines
3.4 KiB
Diff
82 lines
3.4 KiB
Diff
From 33064cd077cf6fa386f0a5a840c2161868da7b3a Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
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Date: Tue, 8 Feb 2022 12:42:34 +0100
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Subject: [PATCH] Run .closehandle_cb asynchrounosly in nmhandle_detach_cb()
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When sock->closehandle_cb is set, we need to run nmhandle_detach_cb()
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asynchronously to ensure correct order of multiple packets processing in
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the isc__nm_process_sock_buffer(). When not run asynchronously, it
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would cause:
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a) out-of-order processing of the return codes from processbuffer();
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b) stack growth because the next TCP DNS message read callback will
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be called from within the current TCP DNS message read callback.
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The sock->closehandle_cb is set to isc__nm_resume_processing() for TCP
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sockets which calls isc__nm_process_sock_buffer(). If the read callback
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(called from isc__nm_process_sock_buffer()->processbuffer()) doesn't
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attach to the nmhandle (f.e. because it wants to drop the processing or
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we send the response directly via uv_try_write()), the
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isc__nm_resume_processing() (via .closehandle_cb) would call
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isc__nm_process_sock_buffer() recursively.
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The below shortened code path shows how the stack can grow:
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1: ns__client_request(handle, ...);
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2: isc_nm_tcpdns_sequential(handle);
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3: ns_query_start(client, handle);
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4: query_lookup(qctx);
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5: query_send(qctcx->client);
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6: isc__nmhandle_detach(&client->reqhandle);
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7: nmhandle_detach_cb(&handle);
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8: sock->closehandle_cb(sock); // isc__nm_resume_processing
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9: isc__nm_process_sock_buffer(sock);
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10: processbuffer(sock); // isc__nm_tcpdns_processbuffer
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11: isc_nmhandle_attach(req->handle, &handle);
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12: isc__nm_readcb(sock, req, ISC_R_SUCCESS);
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13: isc__nm_async_readcb(NULL, ...);
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14: uvreq->cb.recv(...); // ns__client_request
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Instead, if 'sock->closehandle_cb' is set, we need to run detach the
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handle asynchroniously in 'isc__nmhandle_detach', so that on line 8 in
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the code flow above does not start this recursion. This ensures the
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correct order when processing multiple packets in the function
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'isc__nm_process_sock_buffer()' and prevents the stack growth.
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When not run asynchronously, the out-of-order processing leaves the
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first TCP socket open until all requests on the stream have been
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processed.
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If the pipelining is disabled on the TCP via `keep-response-order`
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configuration option, named would keep the first socket in lingering
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CLOSE_WAIT state when the client sends an incomplete packet and then
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closes the connection from the client side.
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(cherry picked from commit afee2b5a7bc933a2d987907fc327a9f118fdbd17)
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---
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lib/isc/netmgr/netmgr.c | 6 +++++-
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1 file changed, 5 insertions(+), 1 deletion(-)
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diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
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index 3283eb6e4f..0ed3182fb6 100644
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--- a/lib/isc/netmgr/netmgr.c
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+++ b/lib/isc/netmgr/netmgr.c
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@@ -1746,8 +1746,12 @@ isc__nmhandle_detach(isc_nmhandle_t **handlep FLARG) {
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handle = *handlep;
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*handlep = NULL;
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+ /*
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+ * If the closehandle_cb is set, it needs to run asynchronously to
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+ * ensure correct ordering of the isc__nm_process_sock_buffer().
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+ */
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sock = handle->sock;
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- if (sock->tid == isc_nm_tid()) {
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+ if (sock->tid == isc_nm_tid() && sock->closehandle_cb == NULL) {
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nmhandle_detach_cb(&handle FLARG_PASS);
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} else {
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isc__netievent_detach_t *event =
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--
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2.34.1
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