coredns/middleware/rewrite

rewrite

rewrite performs internal message rewriting. Rewrites are invisible to the client. There are simple rewrites (fast) and complex rewrites (slower), but they're powerful enough to accommodate most dynamic back-end applications.

Syntax

rewrite FIELD FROM TO

• FIELD is (type, class, name, ...)
• FROM is the exact name of type to match
• TO is the destination name or type to rewrite to

When the FIELD is type and FROM is (A, MX, etc.), the type of the message will be rewritten; e.g., to rewrite ANY queries to HINFO, use rewrite type ANY HINFO.

When the FIELD is class and FROM is (IN, CH, or HS) the class of the message will be rewritten; e.g., to rewrite CH queries to IN use rewrite class CH IN.

When the FIELD is name the query name in the message is rewritten; this needs to be a full match of the name, e.g., rewrite name miek.nl example.org.

If you specify multiple rules and an incoming query matches on multiple (simple) rules, only the first rewrite is applied.

Everything below this line has not been implemented, yet.

rewrite [basename] {
    regexp pattern
    ext    extensions...
    if     a cond b
    status code
    to     destinations...
}

• basepath is the base path to match before rewriting with a regular expression. Default is /.
• regexp (shorthand: r) will match the path with the given regular expression pattern. Extremely high-load servers should avoid using regular expressions.
• extensions... is a space-separated list of file extensions to include or ignore. Prefix an extension with ! to exclude an extension. The forward slash / symbol matches paths without file extensions.
• if specifies a rewrite condition. Multiple ifs are AND-ed together. a and b are any string and may use request placeholders. cond is the condition, with possible values explained below.
• status will respond with the given status code instead of performing a rewrite. In other words, use either "status" or "to" in your rule, but not both. The code must be a number in the format 2xx or 4xx.
• destinations... is one or more space-separated paths to rewrite to, with support for request placeholders as well as numbered regular expression captures such as {1}, {2}, etc. Rewrite will check each destination in order and rewrite to the first destination that exists. Each one is checked as a file or, if it ends with /, as a directory. The last destination will act as the default if no other destination exists. "if" Conditions

The if keyword is a powerful way to describe your rule. It takes the format a cond b, where the values a and b are separated by cond, a condition. The condition can be any of these:

is = a equals b
not = a does NOT equal b
has = a has b as a substring (b is a substring of a)
not_has = b is NOT a substring of a
starts_with = b is a prefix of a
ends_with = b is a suffix of a
match = a matches b, where b is a regular expression
not_match = a does NOT match b, where b is a regular expression

Examples

When requests come in for /mobile, actually serve /mobile/index. rewrite /mobile /mobile/index If the file is not favicon.ico and it is not a valid file or directory, serve the maintenance page if present, or finally, rewrite to index.php.

rewrite {
    if {file} not favicon.ico
    to {path} {path}/ /maintenance.html /index.php
}

If user agent includes "mobile" and path is not a valid file/directory, rewrite to the mobile index page.

rewrite {
    if if {>User-agent} has mobile
    to {path} {path}/ /mobile/index.php
}

If the request path starts with /source, respond with HTTP 403 Forbidden.

rewrite {
    regexp ^/source
    status 403
}

Rewrite /app to /index with a query string. {1} is the matched group (.*).

rewrite /app {
    r  (.*)
    to /index?path={1}
}