ESP8266 Developer Zone

Re: ESP8266 CIPDOMAIN limitation

2017-07-11T00:31:57+08:00

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?

Statistics: Posted by imsherlock — Tue Jul 11, 2017 12:31 am

Re: ESP8266 CIPDOMAIN limitation

2017-07-10T14:35:30+08:00

Hi,

Yes, there is a limitation of 64 bytes.

We will update the documentation to add this description.

Sorry for the inconvenience.

Statistics: Posted by ESP_Faye — Mon Jul 10, 2017 2:35 pm

ESP8266 CIPDOMAIN limitation

2017-07-08T04:19:30+08:00

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?

Statistics: Posted by imsherlock — Sat Jul 08, 2017 4:19 am