curl –connect-timeout and –max-time does not work as expected

curl –connect-timeout and –max-time does not work as expected

Problem Description:

The following command will wait > 60 seconds on Ubuntu 22.04:

curl --verbose --retry-max-time 0 --retry 0 --connect-timeout "30" --max-time "60" ""

Here is the testing result:

root@test:~# echo $(date)
Tue Dec 6 07:26:04 PM CST 2022

root@test:~# curl --verbose --retry-max-time 0 --retry 0 --connect-timeout "30" --max-time "60" ""

* Resolving timed out after 30000 milliseconds
* Closing connection 0
curl: (28) Resolving timed out after 30000 milliseconds

root@test:~# echo $(date)
Tue Dec 6 07:28:26 PM CST 2022

Here is the version:

root@test:~# curl --version
curl 7.81.0 (x86_64-pc-linux-gnu) libcurl/7.81.0 OpenSSL/3.0.2 zlib/1.2.11 brotli/1.0.9 zstd/1.4.8 libidn2/2.3.2 libpsl/0.21.0 (+libidn2/2.3.2) libssh/0.9.6/openssl/zlib nghttp2/1.43.0 librtmp/2.3 OpenLDAP/2.5.12
Release-Date: 2022-01-05
Protocols: dict file ftp ftps gopher gophers http https imap imaps ldap ldaps mqtt pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp 
Features: alt-svc AsynchDNS brotli GSS-API HSTS HTTP2 HTTPS-proxy IDN IPv6 Kerberos Largefile libz NTLM NTLM_WB PSL SPNEGO SSL TLS-SRP UnixSockets zstd

The expected behavior:

The whole timeout should not exceed the 60 seconds or 30 seconds as it
already timeout in Resolving DNS.

What’s the problem and how to fix the timeout with curl?

Solution – 1

It is possible that DNS is not resolving properly and causing cURL to take longer. The issue you describe, looking at your cURL version seems to be similar to what is below:

Instead of cracking your head with rebuilding cURL and configuring it with c-ares, it might be worth a try to test whether a server is reachable first and then initiate cURL:

ping -c 1 &>/dev/null && cURL ...whatever

By default ping will extend timeout by max 4 seconds, which you can finetune using -W option

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