fix(hostname): correct max hostname length from 255 to 253 characters#76
Merged
Conversation
rewiko
approved these changes
Feb 5, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Fixes the maximum hostname length validation from 255 to 253 characters per DNS specifications.
Motivation
RFC 1035 specifies that domain names are limited to 255 octets in wire format. However, this includes the length byte of the first label and the terminating zero-length root label byte. The actual maximum length of a hostname as a human-readable string is 253 characters.
Fox was incorrectly using 255 as the limit, which could allow invalid hostnames that would fail in practice.
Changes
fox.go: Change hostname length check from 255 to 253fox_test.go: Update test cases to use 253-character hostnamesREADME.md: Correct documentation from "255-character limit" to "253-character limit"References