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package dnsutil
import (
"fmt"
"net"
"os"
"github.com/miekg/dns"
)
// ParseHostPortOrFile parses the strings in s, each string can either be a address,
// address:port or a filename. The address part is checked and the filename case a
// resolv.conf like file is parsed and the nameserver found are returned.
func ParseHostPortOrFile(s ...string) ([]string, error) {
var servers []string
for _, host := range s {
addr, _, err := net.SplitHostPort(host)
if err != nil {
// Parse didn't work, it is not a addr:port combo
if net.ParseIP(host) == nil {
// Not an IP address.
ss, err := tryFile(host)
if err == nil {
servers = append(servers, ss...)
continue
}
return servers, fmt.Errorf("not an IP address or file: %q", host)
}
ss := net.JoinHostPort(host, "53")
servers = append(servers, ss)
continue
}
if net.ParseIP(addr) == nil {
// No an IP address.
ss, err := tryFile(host)
if err == nil {
servers = append(servers, ss...)
continue
}
return servers, fmt.Errorf("not an IP address or file: %q", host)
}
servers = append(servers, host)
}
return servers, nil
}
// Try to open this is a file first.
func tryFile(s string) ([]string, error) {
c, err := dns.ClientConfigFromFile(s)
if err == os.ErrNotExist {
return nil, fmt.Errorf("failed to open file %q: %q", s, err)
} else if err != nil {
return nil, err
}
servers := []string{}
for _, s := range c.Servers {
servers = append(servers, net.JoinHostPort(s, c.Port))
}
return servers, nil
}
// ParseHostPort will check if the host part is a valid IP address, if the
// IP address is valid, but no port is found, defaultPort is added.
func ParseHostPort(s, defaultPort string) (string, error) {
addr, port, err := net.SplitHostPort(s)
if port == "" {
port = defaultPort
}
if err != nil {
if net.ParseIP(s) == nil {
return "", fmt.Errorf("must specify an IP address: `%s'", s)
}
return net.JoinHostPort(s, port), nil
}
if net.ParseIP(addr) == nil {
return "", fmt.Errorf("must specify an IP address: `%s'", addr)
}
return net.JoinHostPort(addr, port), nil
}
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