ESP8266 CIPDOMAIN limitation

imsherlock
Posts: 2
Joined: Sat Jul 08, 2017 4:11 am

ESP8266 CIPDOMAIN limitation

Postby imsherlock » Sat Jul 08, 2017 4:19 am

Attempting to resolve a DNS name with a length of 64 characters or greater fails when using the CIPDOMAIN command.
Example:

AT+CIPDOMAIN="firmware-catalog-media-ca57.s3.dualstack.us-east-1.amazonaws.com"
DNS Fail
ERROR


The above DNS name should resolve as a CNAME record to s3.dualstack.us-east-1.amazonaws.com
Reducing the string to 63 characters works (-ca57 has been replaced with -ca1)

AT+CIPDOMAIN="firmware-catalog-media-ca1.s3.dualstack.us-east-1.amazonaws.com"
+CIPDOMAIN:54.231.72.106
OK


The above is also a CNAME record which points to s3.dualstack.us-east-1.amazonaws.com.
I dumped the the libat.a archive and found the at_setupCipomain function which seems to allocate only a character string of 64 bytes to be copied on the stack.

First, can someone confirm this limitation?
Second, can we get an updated firmware with a larger allocation? Or just a fix?

ESP_Faye
Posts: 1646
Joined: Mon Oct 27, 2014 11:08 am

Re: ESP8266 CIPDOMAIN limitation

Postby ESP_Faye » Mon Jul 10, 2017 2:35 pm

Hi,

Yes, there is a limitation of 64 bytes.

We will update the documentation to add this description.

Sorry for the inconvenience.

imsherlock
Posts: 2
Joined: Sat Jul 08, 2017 4:11 am

Re: ESP8266 CIPDOMAIN limitation

Postby imsherlock » Tue Jul 11, 2017 12:31 am

Is there any chance we can get an increase in size? The RFC for DNS states that the domain name may be up to 253 characters, while a given label may contain up to 63 characters. Shouldn't the command be updated to align with this?

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