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67 lines
2.1 KiB
Go
67 lines
2.1 KiB
Go
package bridge
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import (
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"bytes"
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"io/ioutil"
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"regexp"
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)
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const (
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ipv4NumBlock = `(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)`
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ipv4Address = `(` + ipv4NumBlock + `\.){3}` + ipv4NumBlock
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// This is not an IPv6 address verifier as it will accept a super-set of IPv6, and also
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// will *not match* IPv4-Embedded IPv6 Addresses (RFC6052), but that and other variants
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// -- e.g. other link-local types -- either won't work in containers or are unnecessary.
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// For readability and sufficiency for Docker purposes this seemed more reasonable than a
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// 1000+ character regexp with exact and complete IPv6 validation
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ipv6Address = `([0-9A-Fa-f]{0,4}:){2,7}([0-9A-Fa-f]{0,4})`
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)
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var nsRegexp = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`)
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func readResolvConf() ([]byte, error) {
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resolv, err := ioutil.ReadFile("/etc/resolv.conf")
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if err != nil {
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return nil, err
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}
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return resolv, nil
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}
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// getLines parses input into lines and strips away comments.
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func getLines(input []byte, commentMarker []byte) [][]byte {
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lines := bytes.Split(input, []byte("\n"))
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var output [][]byte
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for _, currentLine := range lines {
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var commentIndex = bytes.Index(currentLine, commentMarker)
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if commentIndex == -1 {
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output = append(output, currentLine)
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} else {
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output = append(output, currentLine[:commentIndex])
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}
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}
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return output
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}
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// GetNameserversAsCIDR returns nameservers (if any) listed in
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// /etc/resolv.conf as CIDR blocks (e.g., "1.2.3.4/32")
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// This function's output is intended for net.ParseCIDR
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func getNameserversAsCIDR(resolvConf []byte) []string {
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nameservers := []string{}
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for _, nameserver := range getNameservers(resolvConf) {
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nameservers = append(nameservers, nameserver+"/32")
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}
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return nameservers
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}
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// GetNameservers returns nameservers (if any) listed in /etc/resolv.conf
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func getNameservers(resolvConf []byte) []string {
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nameservers := []string{}
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for _, line := range getLines(resolvConf, []byte("#")) {
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var ns = nsRegexp.FindSubmatch(line)
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if len(ns) > 0 {
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nameservers = append(nameservers, string(ns[1]))
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}
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}
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return nameservers
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}
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