Subdomains exceed maximum length of 63 characters.

Problem/Motivation

RFC 1035 states that the maximum length of a DNS label is 63 characters. The Subdomain module schema has a textfield for the subdomain value with a maximum length of 255. Creating subdomains exceeding the length of 63 can result in URI’s with FQDN's that do not resolve.

Proposed resolution

Update the module schema and form definition, limiting subdomains to 63 characters, and add a new hook_update_N() to retroactively trim subdomains exceeding 63 characters, and change the field definition afterwards.