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fix(hostname): correct max hostname length from 255 to 253 characters #76

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Merged
tigerwill90 merged 1 commit into from
Feb 5, 2026
Merged

fix(hostname): correct max hostname length from 255 to 253 characters #76

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2 changes: 1 addition & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,7 @@ Use cases include:
Hostnames are validated to conform to the [LDH (letters, digits, hyphens) rule](https://datatracker.ietf.org/doc/html/rfc3696.html#section-2)
(lowercase only) and SRV-like "underscore labels". Wildcard segments within hostnames, such as `{sub}.example.com/`, are exempt from LDH validation
since they act as placeholders rather than actual domain labels. As such, they do not count toward the hard limit of 63 characters per label,
nor the 255-character limit for the full hostname (including periods). Internationalized domain names (IDNs) should be specified using an ASCII
nor the 253-character limit for the full hostname. Internationalized domain names (IDNs) should be specified using an ASCII
(Punycode) representation.

The DNS specification permits a trailing period to be used to denote the root, e.g., `example.com` and `example.com.` are equivalent,
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4 changes: 2 additions & 2 deletions fox.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1410,8 +1410,8 @@ func (fox *Router) parseRoute(url string) (parsedRoute, error) {
if partlen > 63 {
return parsedRoute{}, fmt.Errorf("%w: hostname label exceed 63 characters", ErrInvalidRoute)
}
if totallen > 255 {
return parsedRoute{}, fmt.Errorf("%w: hostname exceed 255 characters", ErrInvalidRoute)
if totallen > 253 {
return parsedRoute{}, fmt.Errorf("%w: hostname exceed 253 characters", ErrInvalidRoute)
}
}

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10 changes: 5 additions & 5 deletions fox_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2760,21 +2760,21 @@ func TestParseRoute(t *testing.T) {
)),
},
{
name: "255 character with .",
path: "78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr/",
name: "253 character with .",
path: "78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzj/",
wantN: 0,
wantTokens: slices.Collect(iterutil.SeqOf(
staticToken("78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr", true),
staticToken("78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzj", true),
staticToken("/", false),
)),
},
{
name: "param does not count at character",
path: "{a}.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjx.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr/",
path: "{a}.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjx.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzj/",
wantN: 1,
wantTokens: slices.Collect(iterutil.SeqOf(
paramToken("a", ""),
staticToken(".78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjx.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr", true),
staticToken(".78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjx.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzjxr.78fayzyiqkt3hh2mquv9szfroeexx8qztscu3oudoyfarjl6jmdyxk2cefvzj", true),
staticToken("/", false),
)),
},
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