[GitHub] incubator-brooklyn pull request: BindDnsServer strips invalid char...

[grkvlt <gi...@git.apache.org>]

Github user grkvlt commented on a diff in the pull request:

    https://github.com/apache/incubator-brooklyn/pull/357#discussion_r21098987
  
    --- Diff: software/network/src/main/java/brooklyn/entity/network/bind/BindDnsServerImpl.java ---
    @@ -73,6 +74,23 @@
     
         private static final Logger LOG = LoggerFactory.getLogger(BindDnsServerImpl.class);
     
    +    // As per RFC 952 and RFC 1123.
    +    private static final CharMatcher DOMAIN_NAME_FIRST_CHAR_MATCHER = CharMatcher.inRange('a', 'z')
    +                .or(CharMatcher.inRange('A', 'Z'))
    +                .or(CharMatcher.inRange('0', '9'));
    +    private static final CharMatcher DOMAIN_NAME_MATCHER = DOMAIN_NAME_FIRST_CHAR_MATCHER
    +            .or(CharMatcher.is('-'));
    +
    +
    +    private class HostnameTransformer implements Function<Entity, String> {
    +        @Override
    +        public String apply(Entity input) {
    +            String hostname = input.getAttribute(getConfig(HOSTNAME_SENSOR));
    +            hostname = DOMAIN_NAME_FIRST_CHAR_MATCHER.negate().trimFrom(hostname);
    +            return DOMAIN_NAME_MATCHER.retainFrom(hostname);
    --- End diff --
    
    ```
    hostname = DOMAIN_NAME_FIRST_CHAR_MATCHER.negate().trimLeadingFrom(hostname);
    return DOMAIN_NAME_MATCHER.negate().trimAndCollapseFrom(hostname, '-');
    ```
    
    This would be better, it only removes disallowed characters from the start, and replaces anything else disallowed in the body of the string with `-`.
    
    There's length restrictions too, 63 characters per segment and 255 characters overall maximum.


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