I've got a very weird SSH behavior and it's making me a bit nervous. Basically the progress meter is totally bogus: so bogus that it's nearly useless. And I fear that there may be something else going on (more on this below).
Basically I only have a 60 KB/s upload link or so, yet every single scp I initiate starts saying it's doing 2 MB/s.
Then it invariably tries to "fix" that number, slowly converging toward the real value.
Then, for "big" files (a few MB or more), it invariably stalls at 100% for many seconds (and eventually it succeeds and I get back to the prompt).
The output looks like this:
... test.tgz 16% 2112KB 2.1MB/s 00:04 ETA test.tgz 17% 2208KB 1.7MB/s 00:06 ETA test.tgz 18% 2320KB 1.2MB/s 00:08 ETA test.tgz 19% 2448KB 1.1MB/s 00:08 ETA test.tgz 20% 2576KB 942.2KB/s 00:10 ETA test.tgz 21% 2704KB 697.3KB/s 00:14 ETA test.tgz 22% 2832KB 576.3KB/s 00:16 ETA test.tgz 23% 2960KB 478.3KB/s 00:20 ETA test.tgz 24% 3088KB 399.0KB/s 00:23 ETA test.tgz 25% 3216KB 334.7KB/s 00:27 ETA test.tgz 26% 3344KB 282.6KB/s 00:32 ETA test.tgz 27% 3472KB 240.4KB/s 00:37 ETA test.tgz 28% 3600KB 185.6KB/s 00:48 ETA test.tgz 29% 3728KB 161.9KB/s 00:54 ETA test.tgz 30% 3856KB 142.7KB/s 01:01 ETA ...
(it's on a single line: I did paste multiple lines here, which I got using
scp -vvv to better explain my issue).
At the end, when the output is invariably stuck at 100%, there's actually quite a lot of data missing: I've checked this on the other end and the file is definitely not there in its entirety yet.
All the measurements in percentage are basically pointless: when it says that 80% of a 12 MB file are there, there are only about 65% on the server.
What can explain this?
I'm posting here because I was wondering how these numbers would look like if a man-in-the-middle attack was happening close to my system (maybe on a compromised router or something).
I'm using Linux and SSH / SCP since many years and I don't remember that these numbers were that off.
Download works as expected: if I scp from the remote host to my computer, then the %, ETA and KB/s are all correct.