Option `--dns-servers` not supported

[mschaefers]

docker run --rm mirror.gcr.io/curlimages/curl:latest curl --dns-servers 8.8.8.8 https://google.com

fails with

curl: option --dns-servers: the installed libcurl version doesn't support this
curl: try 'curl --help' or 'curl --manual' for more information

man page states --dns-servers requires that the underlying libcurl was built to support c-ares.

was c-ares support dropped on purpose? Does a workaround or an alternative image exist?

[ahmadalkhansa]

It seems that the image was built using enabled threaded resolver instead. According to the dependencies section in the everything curl book, threaded resolver is a substitute to c-ares that does all the asynchronous name resolution within the same thread.

[acelinkio]

Would be awesome if newer containers supported this functionality. thanks!

[natevw]

Ran into this today. The macOS version of curl had the error so I figured I'd be able to container run curlimages/curl --dns-servers "$mitmIp" https://ipcalf.com as a workaround but got the same error with this.

The link in #59 (comment) is more authoritative but found a similar answer/explanation re. the c-ares backend at https://unix.stackexchange.com/questions/588916/problem-running-curl-with-the-dns-option/588928#588928 as well which mentions (citing) that c-ares has [update: or had — the mailing list citation is from 2009!] some IPv6-related limitations.