PuTTY bug ssh-stuck-queue

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summary: SSH data can get stuck in a queue if session throttled
class: bug: This is clearly an actual problem we want fixed.
priority: historic: This is an old bug report that we think is either fixed without noticing, or confined to old systems, or too vague.
present-in: 0.58

If an SSH connection is throttled ("frozen"), incoming data can end up stuck in ssh->queued_incoming_data and not processed until more data arrives from the network (or ever, if the socket has closed in the meantime), since that buffer is only examined when new data arrives. In general, queued data may be being processed rather later than it could be.

For instance, cat'ing a large text file might hang, only to resume when a key is pressed (which will result in outgoing and then incoming traffic).

There's been a report that this shows up in real life when receiving lots of data down an SSH-1 connection, where ssh1_throttle() is called.
<OF39FE4940.43DB4418-ONCC257067.000BF4DD-CC257067.000F5220@bnz.co.nz>

Another likely report of this problem:
<4460FE84.10303@bytte.plus.com>

ssh_set_frozen() should probably signal something, but I'm not sure enough of the control flow to know quite what. (This is already done in some places, e.g., ssh_dialog_callback().)

SGT, 2024-11-17: classifying this bug as historic. Data queuing has had multiple rewrites since then, which have likely fixed this, but the report is vague enough that it's impossible to confirm for sure.

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Audit trail for this bug.

(last revision of this bug record was at 2024-11-17 15:29:37 +0000)