Unable to create long TXT records #376

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Habbie opened this Issue Apr 26, 2013 · 6 comments

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@Habbie
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Habbie commented Apr 26, 2013

TXT records can be up to 64k long per the specs (though not all resolvers or clients actually handle this much).

in modules/pipebackend/coprocess.cc we have the following that limits the input from the pipe backend process to 1024 chars:

void CoProcess::receive(string &receive)
{
char line[1024];
memset(line,0,1024);
...

if(!fgets(line,1023,d_fp))
throw AhuException("Child closed pipe");

Tweaking this would allow us to have larger TXT responses.

@Habbie Habbie was assigned Apr 26, 2013
@Habbie Habbie closed this Apr 26, 2013
@Habbie
Member
Habbie commented Apr 26, 2013

Author: ahu
fixed in 3.0

@indolering

@Habbie I'm trying to track down the TXT length limits imposed by different DNS servers. Looking at the code, it appears as if the limit checking was just removed.

Was this moved to somewhere else in the code? Could you give me some hints to figure this out?

@Habbie
Member
Habbie commented Nov 25, 2016

@indolering as the first line of this issue states, the limit is 64 kilobytes, as per RFC1035.

@indolering

@Habbie but there is usually an implementation specific limit, I believe that Bind's is 2MB.

@Habbie
Member
Habbie commented Nov 25, 2016

@indolering no; the RFC limit is 64k, no implementation can go beyond that.

If you want to discuss more, please use our community support facilities https://www.powerdns.com/opensource.html or, of course, the community support facilities of products like BIND.

@indolering
indolering commented Nov 26, 2016 edited

no; the RFC limit is 64k, no implementation can go beyond that.

Err, not 2MB, 2KB! Well, technically speaking it's technically 2KiB.

If you want to discuss more, please use our community support facilities

Ahh, fantastic! Sorry for spamming your notification feed.

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