83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
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package dnsutil
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import (
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"fmt"
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"net"
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"os"
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"github.com/miekg/dns"
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)
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// ParseHostPortOrFile parses the strings in s, each string can either be a address,
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// address:port or a filename. The address part is checked and the filename case a
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// resolv.conf like file is parsed and the nameserver found are returned.
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func ParseHostPortOrFile(s ...string) ([]string, error) {
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var servers []string
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for _, host := range s {
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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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if net.ParseIP(host) == nil {
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// Not an IP address.
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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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ss := net.JoinHostPort(host, "53")
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servers = append(servers, ss)
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continue
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}
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if net.ParseIP(addr) == nil {
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// No an IP address.
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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, host)
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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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// ParseHostPort 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 ParseHostPort(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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