quic: fix reader backpressure deadlock on idle connections - #63950

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quic: fix reader backpressure deadlock on idle connections#63950
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.

When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.

Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).

If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.

This PR fixes that, by ensuring we always flush a send after we update the stream window.

@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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@nodejs-github-botnodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. needs-ci PRs that need a full CI run. quic Issues and PRs related to the QUIC transport implementation. labels Jun 16, 2026
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.

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aduh95 pushed a commit that referenced this pull request Jun 20, 2026
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quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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aduh95 pushed a commit to aduh95/node that referenced this pull request Jul 30, 2026
@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit to aduh95/node that referenced this pull request Aug 3, 2026
@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit that referenced this pull request Aug 6, 2026
@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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quic: fix reader backpressure deadlock on idle connections - #63950
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quic: fix reader backpressure deadlock on idle connections#63950
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pimterry:fix-blocked-backpressure
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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, 'i');
if (__m === '*' || __re.test(location.href)) {
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try {
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quic: fix reader backpressure deadlock on idle connections - #63950
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quic: fix reader backpressure deadlock on idle connections#63950
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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quic: fix reader backpressure deadlock on idle connections - #63950
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quic: fix reader backpressure deadlock on idle connections#63950
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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quic: fix reader backpressure deadlock on idle connections
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Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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quic: fix reader backpressure deadlock on idle connections - #63950
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pimterry:fix-blocked-backpressure
Jun 20, 2026
Merged
quic: fix reader backpressure deadlock on idle connections#63950
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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quic: fix reader backpressure deadlock on idle connections - #63950
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pimterry:fix-blocked-backpressure
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quic: fix reader backpressure deadlock on idle connections#63950
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
that referenced
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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, 'i');
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try {
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quic: fix reader backpressure deadlock on idle connections - #63950
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quic: fix reader backpressure deadlock on idle connections#63950
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pimterry:fix-blocked-backpressure
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@QardQardQard approved these changes
@jasnelljasnelljasnell approved these changes
@Ethan-ArrowoodEthan-ArrowoodEthan-Arrowood approved these changes

+2 more reviewers

@metcoder95metcoder95metcoder95 approved these changes
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c++Issues and PRs that require attention from people who are familiar with C++.commit-queue-squashPRs the Commit Queue should land as one squashed commit.needs-ciPRs that need a full CI run.quicIssues and PRs related to the QUIC transport implementation.

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
quic: fix reader backpressure deadlock on idle connections - #63950
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nodejs-github-bot merged 2 commits into
nodejs:mainfrom 
pimterry:fix-blocked-backpressure
Jun 20, 2026
Merged
quic: fix reader backpressure deadlock on idle connections#63950
nodejs-github-bot merged 2 commits into
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pimterry:fix-blocked-backpressure
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When we're not reading from a QUIC stream, inbound data will build up until it hits the stream flow control window, and then the remote peer will stop sending until we're ready to continue.
When we're ready, we call session().ExtendStreamOffset (which calls ngtcp2_conn_extend_max_stream_offset) to send a MAX_STREAM_DATA frame to the peer expanding the window, telling them they can send us more.
Right now this doesn't always work: we call ExtendStreamOffset but that only queues the frame, it doesn't actually send it. This is masked in most cases by other activity on most sessions that ends up sending the frame with it implicitly (most commonly acks).
If you ever have an idle session though, and then you read a stream that's been blocked like this, the frame will never be sent, which deadlocks: you're waiting for more data, and the remote peer is waiting to be told it's allowed to send some.
This PR fixes that, by ensuring we always flush a send after we update the stream window.
@pimterry
quic: fix reader backpressure deadlock on idle connections
7af487d
Signed-off-by: Tim Perry <pimterry@gmail.com>
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Suggestions applied, thanks both! I'll need a quick rereview when somebody has a sec please.
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
b62d569
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
9faca2e
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
to aduh95/node
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@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
bd9c68d
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: nodejs#63950
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
aduh95 pushed a commit
that referenced
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Aug 6, 2026
@pimterry@aduh95
quic: fix reader backpressure deadlock on idle connections
e264c5c
Signed-off-by: Tim Perry <pimterry@gmail.com>
PR-URL: #63950
Backport-PR-URL: #64675
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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