117 lines
3.0 KiB
Go
117 lines
3.0 KiB
Go
package parse
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import (
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"errors"
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"fmt"
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"net"
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"os"
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"strings"
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"github.com/coredns/coredns/plugin/pkg/transport"
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"github.com/miekg/dns"
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)
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// ErrNoNameservers is returned by HostPortOrFile if no servers can be parsed.
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var ErrNoNameservers = errors.New("no nameservers found")
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// Strips the zone, but preserves any port that comes after the zone
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func stripZone(host string) string {
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if strings.Contains(host, "%") {
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lastPercent := strings.LastIndex(host, "%")
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newHost := host[:lastPercent]
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return newHost
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}
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return host
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}
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// HostPortOrFile parses the strings in s, each string can either be a
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// address, [scheme://]address:port or a filename. The address part is checked
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// and in case of filename a resolv.conf like file is (assumed) and parsed and
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// the nameservers found are returned.
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func HostPortOrFile(s ...string) ([]string, error) {
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var servers []string
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for _, h := range s {
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trans, host := Transport(h)
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addr, _, err := net.SplitHostPort(host)
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if err != nil {
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// Parse didn't work, it is not a addr:port combo
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hostNoZone := stripZone(host)
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if net.ParseIP(hostNoZone) == nil {
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ss, err := tryFile(host)
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if err == nil {
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servers = append(servers, ss...)
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continue
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}
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return servers, fmt.Errorf("not an IP address or file: %q", host)
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}
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var ss string
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switch trans {
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case transport.DNS:
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ss = net.JoinHostPort(host, transport.Port)
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case transport.TLS:
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ss = transport.TLS + "://" + net.JoinHostPort(host, transport.TLSPort)
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case transport.GRPC:
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ss = transport.GRPC + "://" + net.JoinHostPort(host, transport.GRPCPort)
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case transport.HTTPS:
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ss = transport.HTTPS + "://" + net.JoinHostPort(host, transport.HTTPSPort)
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}
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servers = append(servers, ss)
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continue
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}
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if net.ParseIP(stripZone(addr)) == nil {
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ss, err := tryFile(host)
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if err == nil {
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servers = append(servers, ss...)
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continue
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}
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return servers, fmt.Errorf("not an IP address or file: %q", host)
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}
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servers = append(servers, h)
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}
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if len(servers) == 0 {
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return servers, ErrNoNameservers
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}
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return servers, nil
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}
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// Try to open this is a file first.
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func tryFile(s string) ([]string, error) {
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c, err := dns.ClientConfigFromFile(s)
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if err == os.ErrNotExist {
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return nil, fmt.Errorf("failed to open file %q: %q", s, err)
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} else if err != nil {
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return nil, err
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}
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servers := []string{}
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for _, s := range c.Servers {
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servers = append(servers, net.JoinHostPort(s, c.Port))
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}
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return servers, nil
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}
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// HostPort will check if the host part is a valid IP address, if the
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// IP address is valid, but no port is found, defaultPort is added.
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func HostPort(s, defaultPort string) (string, error) {
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addr, port, err := net.SplitHostPort(s)
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if port == "" {
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port = defaultPort
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}
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if err != nil {
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if net.ParseIP(s) == nil {
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return "", fmt.Errorf("must specify an IP address: `%s'", s)
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}
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return net.JoinHostPort(s, port), nil
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}
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if net.ParseIP(addr) == nil {
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return "", fmt.Errorf("must specify an IP address: `%s'", addr)
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}
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return net.JoinHostPort(addr, port), nil
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}
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