SCP/SFTP: avoid busy loop on receive #17533
Closed
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The libssh libraries do not reveal if they still have data buffered from the peer. Only when their buffers are read empty can curl be sure that it is safe to rely on socket polling. This change adds detection of EGAIN on receive in the transfer loop and allows SFTP/SCP transfers to avoid a busy loop in such a case (which should happen often when CPU exceeds network bandwidth).
icing
changed the title
bagder
approved these changes
Jun 5, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The libssh libraries do not reveal if they still have data buffered from the peer. Only when their buffers are read empty can curl be sure that it is safe to rely on socket polling.
This change adds detection of EAGAIN on receive in the transfer loop and allows SFTP/SCP transfers to avoid a busy loop in such a case (which should happen often when CPU exceeds network bandwidth).