Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

CURLOPT_RESOLVE and nearly expired DNS Cache entries: replace old entry #2622

Closed
wants to merge 4 commits into from

Conversation

ajorajev
Copy link

@ajorajev ajorajev commented May 30, 2018

We use CURLOPT_RESOLVE to tell Curl to use specific addresses instead of doing real DNS lookup.

when cached address is already there (saved by Curl internally) and close to expire, then by the time next http request is made, it can get expired.

Partial fix would be to mark existing entry as set by CURLOPT_RESOLVE (by setting timestamp to zero). This will keep this entry permanently in the cache as intended.

However, currently, if the cache entry already exists, CURLOPT_RESOLVE just leaves it, thus
an old address remains (while calling code expects new address to be saved).

Let's say that cURL already looked up "example.org" recently and found its IP address to be 1.1.1.1.
As usual, it's stored in the relevant DNS cache. Then, later, we issue a new request that uses the same DNS cache, and that 1.1.1.1 entry is still in the cache.

Then, if we do:
curl_easy_setopt(handle, CURLOPT_RESOLVE, [ "example.org:80:2.2.2.2" ]); and then issue the new request, we want this current request to use 2.2.2.2 as its IP

So it is best if we always override existing entries.

@bagder
Copy link
Member

bagder commented May 30, 2018

Thanks, try make checksrc to make sure there's no style warnings. The CI found this nit:

./unit1609.c:128:54: warning: sizeof without parenthesis (SIZEOFNOPAREN)
     int addressnum = sizeof tests[i].address / sizeof *tests[i].address;
                                                      ^

@ajorajev
Copy link
Author

ajorajev commented May 31, 2018

thanks, just fixed now, will always run "make checkrsc" from now on.

.gitignore Outdated
@@ -1,3 +1,4 @@
.DS_Store
Copy link
Member

@bagder bagder May 31, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't think this belongs here.

Copy link
Author

@ajorajev ajorajev May 31, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

this is local file, which MacOS creates to store custom attributes of its containing folder (position of icons, etc.). when I create local GIT copy, this file is always coming up and I assume it happens to other developers (who use Mac).
but yes, having perused all content of .gitignore I can see that it contains wildcards to files related to Curl itself. I will remove this now and check is there way to configure GIT locally to ignore some files.

Copy link
Author

@ajorajev ajorajev May 31, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

ok, I found solution - I can have my own gitignore using:

git config --global core.excludesfile ~/.gitignore

Copy link
Contributor

@jzakrzewski jzakrzewski May 31, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Maybe explicitly ignoring all dot-files + whitelisting those we need wouldn't be a bad idea?

Copy link
Member

@bagder bagder May 31, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't see a need for that. I think we should stick to ignoring files that are generated by a curl build. If you want to ignore more files, it is very easy to do what @ajorajev did and just set your own ignore files for those - I do that too.

Copy link
Contributor

@jzakrzewski jzakrzewski Jun 1, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I thought the same before I've spotted Vim, Eclipse, and backup files typical for Pluma/GEdit/etc there. But I won't argue on it.

Copy link
Member

@bagder bagder Jun 1, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Right, but I consider editor backup files to be sort of "generated by a curl build" or at least "created as a result of someone working on curl".

…ins wildcards related to Curl build, not local OS
@bagder
Copy link
Member

bagder commented Jun 1, 2018

Thanks!

@bagder bagder closed this in f66d97b Jun 1, 2018
@ajorajev
Copy link
Author

ajorajev commented Jun 1, 2018

thank you too.

@lock lock bot locked as resolved and limited conversation to collaborators Aug 30, 2018
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
Projects
None yet
Development

Successfully merging this pull request may close these issues.

None yet

3 participants