SCP/SFTP: avoid busy loop on receive #17533
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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
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bagder
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Jun 5, 2025
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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).