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setopt: add CURLOPT_DOH_URL #2668

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setopt: add CURLOPT_DOH_URL #2668

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@bagder
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@bagder bagder commented Jun 18, 2018

Support for DNS-over-HTTPS for name resolving when doing transfers.

Complies with dns-over-https-14, tested a bit against the cloudflare end-point.

Wiki page with status, TODO and more.

This is still early days.

simplest example:

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;
  CURLcode res;

  curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://curl.haxx.se/");
    curl_easy_setopt(curl, CURLOPT_DOH_URL, "https://dns.cloudflare.com/dns-query");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
  return 0;
}
@bagder bagder force-pushed the bagder/DOH branch 3 times, most recently from 6bf97fc to eca3d0b Jun 24, 2018
@bagder bagder changed the title setopt: add CURLOPT_DOH_URL [WIP] setopt: add CURLOPT_DOH_URL Jun 27, 2018
@bagder bagder removed the on-hold label Jun 27, 2018
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@danielgustafsson danielgustafsson left a comment

A few scattered comments from skimming the code.

lib/doh.c Outdated

static const char *doh_strerror(DOHcode code)
{
return errors[code];
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@danielgustafsson danielgustafsson Aug 30, 2018

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Should this do bounds checking? While not at risk in the current coding, belts are stylish when coupled with suspenders..

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@bagder bagder Aug 31, 2018

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You're totally correct of course. I'll fix!

lib/doh.c Outdated
result = CURLE_OUT_OF_MEMORY;
goto error;
}
p->serverdoh.size = 0;
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@danielgustafsson danielgustafsson Aug 30, 2018

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Shouldn't this be set to 1 per the above allocation? (the addition in doh_write_cb() relies on this being "incorrect" but that seems a bit magic) On that note, is there a reason to allocate 1 rather than use a NULL ptr to indicate "reallocation required" since realloc() on a NULL ptr is identical to malloc()?

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@bagder bagder Aug 31, 2018

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You're right on the size assign. But I think it should rather allocate a sensible default size that can make it avoid the realloc in typical responses. I'll make it a 100 bytes I think.

heap space.

Note that \fIcurl_easy_setopt(3)\fP won't actually parse the given string so
given a bad DOH URL, curl will not be detected a problem until it tries to
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@danielgustafsson danielgustafsson Aug 30, 2018

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Was this intended to say "will not detect a problem"?

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@bagder bagder Aug 31, 2018

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Yes!

lib/doh.c Outdated
}

#define ERROR_CHECK_SETOPT(x,y) result = curl_easy_setopt(doh, x, y); \
if(result) goto error;
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@gvanem gvanem Aug 31, 2018

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This will trigger -Wextra-semi warnings with clang.

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@bagder bagder Aug 31, 2018

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Thanks, I'll fix!

lib/urldata.h Outdated
size_t size;
};

/* one of these for each DOH HTTP request */
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@danielgustafsson danielgustafsson Aug 31, 2018

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Nitpick, but should this say "DOH HTTPS request"?

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@bagder bagder Sep 1, 2018

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correct!

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@bagder bagder Sep 1, 2018

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or perhaps just "each DoH request" ...

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@bagder bagder commented Sep 1, 2018

The short name of the protocol became DoH while this patch was in development, I'm changing source comments to use the new abbreviation.

lib/doh.c Outdated Show resolved Hide resolved
lib/doh.c Outdated Show resolved Hide resolved
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@danielgustafsson danielgustafsson commented Sep 4, 2018

@bagder bagder closed this in abff183 Sep 6, 2018
@bagder bagder deleted the bagder/DOH branch Sep 6, 2018
falconindy added a commit to falconindy/curl that referenced this issue Sep 10, 2018
@lock lock bot locked as resolved and limited conversation to collaborators Dec 5, 2018
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3 participants