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resolv_compiler.go
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/
resolv_compiler.go
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package dns
import (
"fmt"
"net"
"regexp"
"strings"
)
type ResolvCompiler struct{}
func (n *ResolvCompiler) Determine(resolvContents string, hostIP net.IP, pluginNameservers, operatorNameservers, additionalNameservers []net.IP, pluginSearchDomains []string) (entries []string) {
if pluginSearchDomains != nil {
defer func() {
entries = append(entries, searchDomainEntry(pluginSearchDomains))
}()
}
if pluginNameservers != nil {
return nameserverEntries(pluginNameservers)
}
if len(operatorNameservers) > 0 {
return nameserverEntries(append(operatorNameservers, additionalNameservers...))
}
nameserversFromHost := parseResolvContents(resolvContents, hostIP, pluginSearchDomains != nil)
return append(nameserversFromHost, nameserverEntries(additionalNameservers)...)
}
func parseResolvContents(resolvContents string, hostIP net.IP, ignoreSearchDomains bool) []string {
loopbackNameserver := regexp.MustCompile(`^\s*nameserver\s+127\.0\.0\.\d+\s*$`)
if loopbackNameserver.MatchString(resolvContents) {
return nameserverEntries([]net.IP{hostIP})
}
entries := []string{}
for _, resolvEntry := range strings.Split(strings.TrimSpace(resolvContents), "\n") {
if resolvEntry == "" {
continue
}
if ignoreSearchDomains && strings.HasPrefix(resolvEntry, "search") {
continue
}
if !strings.HasPrefix(resolvEntry, "nameserver") {
entries = append(entries, resolvEntry)
continue
}
pattern := regexp.MustCompile(`127\.\d{1,3}\.\d{1,3}\.\d{1,3}`)
if !pattern.MatchString(resolvEntry) {
nameserverFields := strings.Fields(resolvEntry)
if len(nameserverFields) != 2 {
continue
}
entries = append(entries, nameserverEntry(nameserverFields[1]))
}
}
return entries
}
func nameserverEntries(ips []net.IP) []string {
nameserverEntries := []string{}
for _, ip := range ips {
nameserverEntries = append(nameserverEntries, nameserverEntry(ip.String()))
}
return nameserverEntries
}
func nameserverEntry(ip string) string {
return fmt.Sprintf("nameserver %s", ip)
}
func searchDomainEntry(entries []string) string {
searchDomains := "search"
for _, entry := range entries {
searchDomains += " " + entry
}
return searchDomains
}