Curl causes high load on Synology devices #12517
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I originally thought it might be Alpine related so I created this: alpinelinux/docker-alpine#365 For completeness, I paste the details here: As a test, I used the image standalone and got the same result silenus [~]$ docker pull alpine
Using default tag: latest
latest: Pulling from library/alpine
Digest: sha256:51b67269f354137895d43f3b3d810bfacd3945438e94dc5ac55fdac340352f48
Status: Image is up to date for alpine:latest
docker.io/library/alpine:latest
silenus [~]$ docker run --rm -ti alpine sh
/ # apk add --no-cache curl
fetch https://dl-cdn.alpinelinux.org/alpine/v3.19/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.19/community/x86_64/APKINDEX.tar.gz
(1/8) Installing ca-certificates (20230506-r0)
(2/8) Installing brotli-libs (1.1.0-r1)
(3/8) Installing c-ares (1.22.1-r0)
(4/8) Installing libunistring (1.1-r2)
(5/8) Installing libidn2 (2.3.4-r4)
(6/8) Installing nghttp2-libs (1.58.0-r0)
(7/8) Installing libcurl (8.5.0-r0)
(8/8) Installing curl (8.5.0-r0)
Executing busybox-1.36.1-r15.trigger
Executing ca-certificates-20230506-r0.trigger
OK: 12 MiB in 23 packages
/ # time curl https://google.com
^CCommand terminated by signal 2
real 8m 3.83s
user 4m 52.19s
sys 2m 56.06s
/ # Some more information: |
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Use |
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What is the output of curl -v https://google.com ? This is much more likely to
be an issue with the environment than an actual curl issue, e.g. a firewall or
other network issue (especially given that Docker is involved).
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This is curl on the synology Running in docker I canceled the curl call after a few of minutes To test that it is not firewall related I was able to use wget |
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/ # time curl -vvvv https://google.com
^CCommand terminated by signal 2
The lack of any output at all implies that there is a DNS resolution issue. The
c-ares resolver version being used there is well over 5 years out of date; I'd
try updating that to start with.
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Sorry for the confusion, I think the version you were looking at was the one on the actual device which is working. The version in the container is as follows: I have done the following: And getting the same result. These packages are pretty new. |
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Yes, I clearly mixed those versions up. Try running it under strace or ltrace
and you should get some clues as to where it's hanging.
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I tried replicating this on my laptop and got the following, which is also strange but at least it doesn't get stuck: I have attached a copy of the output from the strace it is getting stuck on |
The getrandom man page explains ENOSYS like this: But also: According to logs above, this runs on a 3.10 kernel. I believe c-ares is the one using this call, not curl itself. You can verify this by trying a curl build that does not use c-ares. |
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This is now fixed in c-ares. Not a curl bug. |
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I did this
I tried to run curl in a docker image using the latest Alpine image on a Synology DS1813+ and it just hangs.
I expected the following
I expected to get data returned from the URL.
curl/libcurl version
curl 8.5.0 (x86_64-alpine-linux-musl) libcurl/8.5.0 OpenSSL/3.1.4 zlib/1.3 brotli/1.1.0 c-ares/1.22.1 libidn2/2.3.4 nghttp2/1.58.0
Release-Date: 2023-12-06
Protocols: dict file ftp ftps gopher gophers http https imap imaps mqtt pop3 pop3s rtsp smb smbs smtp smtps telnet tftp ws wss
Features: alt-svc AsynchDNS brotli HSTS HTTP2 HTTPS-proxy IDN IPv6 Largefile libz NTLM SSL threadsafe TLS-SRP UnixSockets
operating system
alpine 3.19.0
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