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Make sure to requeue a datagram and let the caller know that it could not be sent. An example of this is when a pending ack has consumed space before the datagram.
holleman
requested review from
agnosticdev,
kkuk24,
rpaulo and
tfpauly
as code owners
September 18, 2026 21:21
agnosticdev
reviewed
Sep 18, 2026
| connection.log.datapath( | ||
| "datagram for flow \(firstFlowID.debugDescription) does not fit \(roomBeforeWriting) free bytes; requeueing" | ||
| ) | ||
| datagrams.prepend(frame: datagramFrame) |
Collaborator
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Okay, so here we just add the frame back in and frame array and that way pending items knows to build a packet here for that flow again, correct?
Contributor
Author
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Yes, redo it. If it was a pending ack it would have gone out and then when we return we can pick up an empty packet and then send the datagram.
Collaborator
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In general, this seems like a good idea to not drop locally -- but does this cause a case where not being able to send a particular datagram to be at the front of the list forever and if it is too big to fit, no other datagrams can send?
rpaulo
reviewed
Sep 18, 2026
| connection.log.error("Unable to write datagram for flow \(firstFlowID)") | ||
| // Requeue rather than finalize and pass up the error so a retry is possible | ||
| connection.log.datapath( | ||
| "datagram for flow \(firstFlowID.debugDescription) does not fit \(roomBeforeWriting) free bytes; requeueing" |
Contributor
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Suggested change
| "datagram for flow \(firstFlowID.debugDescription) does not fit \(roomBeforeWriting) free bytes; requeueing" | |
| "Datagram for flow \(firstFlowID.debugDescription) does not fit \(roomBeforeWriting) free bytes; requeueing" |
A datagram too big for the flow should be dropped and prevent any head-of-line blocking. That works, but add a test to ensure that as well.
tfpauly
approved these changes
Sep 18, 2026
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Make sure to requeue a datagram and let the caller know that it could not be sent. An example of this is when a pending ack has consumed space before the datagram.