diff options
| -rw-r--r-- | core/dnsserver/directives.go | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/core/dnsserver/directives.go b/core/dnsserver/directives.go index 7f0c1a8f7..17b421741 100644 --- a/core/dnsserver/directives.go +++ b/core/dnsserver/directives.go @@ -1,5 +1,67 @@ package dnsserver +import ( + "fmt" + "os" + "strings" +) + +// RegisterDirective splices name into the list of directives +// immediately before another directive. . +// If before is empty, +// the directive will be appended to the end of the list. +// +// It is imperative that directives execute in the proper +// order, and hard-coding the list of directives guarantees +// a correct, absolute order every time. This function is +// convenient when developing a plugin, but it does not +// guarantee absolute ordering. Multiple plugins registering +// directives with this function will lead to non- +// deterministic builds and buggy software. +// +// Directive names must be lower-cased and unique. Any errors +// here are fatal, and even successful calls print a message +// to stdout as a reminder to use it only in development. +func RegisterDirective(name, before string) { + if name == "" { + fmt.Println("[FATAL] Cannot register empty directive name") + os.Exit(1) + } + if strings.ToLower(name) != name { + fmt.Printf("[FATAL] %s: directive name must be lowercase\n", name) + os.Exit(1) + } + for _, dir := range directives { + if dir == name { + fmt.Printf("[FATAL] %s: directive name already exists\n", name) + os.Exit(1) + } + } + if before == "" { + directives = append(directives, name) + } else { + var found bool + for i, dir := range directives { + if dir == before { + directives = append(directives[:i], append([]string{name}, directives[i:]...)...) + found = true + break + } + } + if !found { + fmt.Printf("[FATAL] %s: directive not found\n", before) + os.Exit(1) + } + } + msg := fmt.Sprintf("Registered directive '%s' ", name) + if before == "" { + msg += "at end of list" + } else { + msg += fmt.Sprintf("before '%s'", before) + } + fmt.Printf("[INFO] %s\n", msg) +} + // Add here, and in core/coredns.go to use them. // Directives are registered in the order they should be |