Drop libnetwork vendor and move the code into pkg/

The vendoring issues with libnetwork were significant (it was
dragging in massive amounts of code) and were just not worth
spending the time to work through. Highly unlikely we'll ever end
up needing to update this code, so move it directly into pkg/ so
we don't need to vendor libnetwork. Make a few small changes to
remove the need for the remainder of libnetwork.

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

1 files changed, 244 insertions, 0 deletions

diff --git a/pkg/resolvconf/resolvconf.go b/pkg/resolvconf/resolvconf.go
new file mode 100644
index 000000000..476999f00
--- /dev/null
+++ b/pkg/resolvconf/resolvconf.go
@@ -0,0 +1,244 @@
+// Package resolvconf provides utility code to query and update DNS configuration in /etc/resolv.conf.
+// Originally from github.com/docker/libnetwork/resolvconf.
+package resolvconf
+
+import (
+	"bytes"
+	"io/ioutil"
+	"regexp"
+	"strings"
+	"sync"
+
+	"github.com/containers/libpod/pkg/resolvconf/dns"
+	"github.com/docker/docker/pkg/ioutils"
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	// DefaultResolvConf points to the default file used for dns configuration on a linux machine
+	DefaultResolvConf = "/etc/resolv.conf"
+)
+
+var (
+	// Note: the default IPv4 & IPv6 resolvers are set to Google's Public DNS
+	defaultIPv4Dns = []string{"nameserver 8.8.8.8", "nameserver 8.8.4.4"}
+	defaultIPv6Dns = []string{"nameserver 2001:4860:4860::8888", "nameserver 2001:4860:4860::8844"}
+	ipv4NumBlock   = `(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)`
+	ipv4Address    = `(` + ipv4NumBlock + `\.){3}` + ipv4NumBlock
+	// This is not an IPv6 address verifier as it will accept a super-set of IPv6, and also
+	// will *not match* IPv4-Embedded IPv6 Addresses (RFC6052), but that and other variants
+	// -- e.g. other link-local types -- either won't work in containers or are unnecessary.
+	// For readability and sufficiency for Docker purposes this seemed more reasonable than a
+	// 1000+ character regexp with exact and complete IPv6 validation
+	ipv6Address = `([0-9A-Fa-f]{0,4}:){2,7}([0-9A-Fa-f]{0,4})(%\w+)?`
+
+	localhostNSRegexp = regexp.MustCompile(`(?m)^nameserver\s+` + dns.IPLocalhost + `\s*\n*`)
+	nsIPv6Regexp      = regexp.MustCompile(`(?m)^nameserver\s+` + ipv6Address + `\s*\n*`)
+	nsRegexp          = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`)
+	nsIPv6Regexpmatch = regexp.MustCompile(`^\s*nameserver\s*((` + ipv6Address + `))\s*$`)
+	nsIPv4Regexpmatch = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `))\s*$`)
+	searchRegexp      = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`)
+	optionsRegexp     = regexp.MustCompile(`^\s*options\s*(([^\s]+\s*)*)$`)
+)
+
+var lastModified struct {
+	sync.Mutex
+	sha256   string
+	contents []byte
+}
+
+// File contains the resolv.conf content and its hash
+type File struct {
+	Content []byte
+	Hash    string
+}
+
+// Get returns the contents of /etc/resolv.conf and its hash
+func Get() (*File, error) {
+	return GetSpecific(DefaultResolvConf)
+}
+
+// GetSpecific returns the contents of the user specified resolv.conf file and its hash
+func GetSpecific(path string) (*File, error) {
+	resolv, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	hash, err := ioutils.HashData(bytes.NewReader(resolv))
+	if err != nil {
+		return nil, err
+	}
+	return &File{Content: resolv, Hash: hash}, nil
+}
+
+// GetIfChanged retrieves the host /etc/resolv.conf file, checks against the last hash
+// and, if modified since last check, returns the bytes and new hash.
+// This feature is used by the resolv.conf updater for containers
+func GetIfChanged() (*File, error) {
+	lastModified.Lock()
+	defer lastModified.Unlock()
+
+	resolv, err := ioutil.ReadFile("/etc/resolv.conf")
+	if err != nil {
+		return nil, err
+	}
+	newHash, err := ioutils.HashData(bytes.NewReader(resolv))
+	if err != nil {
+		return nil, err
+	}
+	if lastModified.sha256 != newHash {
+		lastModified.sha256 = newHash
+		lastModified.contents = resolv
+		return &File{Content: resolv, Hash: newHash}, nil
+	}
+	// nothing changed, so return no data
+	return nil, nil
+}
+
+// GetLastModified retrieves the last used contents and hash of the host resolv.conf.
+// Used by containers updating on restart
+func GetLastModified() *File {
+	lastModified.Lock()
+	defer lastModified.Unlock()
+
+	return &File{Content: lastModified.contents, Hash: lastModified.sha256}
+}
+
+// FilterResolvDNS cleans up the config in resolvConf.  It has two main jobs:
+// 1. It looks for localhost (127.*|::1) entries in the provided
+//    resolv.conf, removing local nameserver entries, and, if the resulting
+//    cleaned config has no defined nameservers left, adds default DNS entries
+// 2. Given the caller provides the enable/disable state of IPv6, the filter
+//    code will remove all IPv6 nameservers if it is not enabled for containers
+//
+func FilterResolvDNS(resolvConf []byte, ipv6Enabled bool) (*File, error) {
+	cleanedResolvConf := localhostNSRegexp.ReplaceAll(resolvConf, []byte{})
+	// if IPv6 is not enabled, also clean out any IPv6 address nameserver
+	if !ipv6Enabled {
+		cleanedResolvConf = nsIPv6Regexp.ReplaceAll(cleanedResolvConf, []byte{})
+	}
+	// if the resulting resolvConf has no more nameservers defined, add appropriate
+	// default DNS servers for IPv4 and (optionally) IPv6
+	if len(GetNameservers(cleanedResolvConf)) == 0 {
+		logrus.Infof("No non-localhost DNS nameservers are left in resolv.conf. Using default external servers: %v", defaultIPv4Dns)
+		dns := defaultIPv4Dns
+		if ipv6Enabled {
+			logrus.Infof("IPv6 enabled; Adding default IPv6 external servers: %v", defaultIPv6Dns)
+			dns = append(dns, defaultIPv6Dns...)
+		}
+		cleanedResolvConf = append(cleanedResolvConf, []byte("\n"+strings.Join(dns, "\n"))...)
+	}
+	hash, err := ioutils.HashData(bytes.NewReader(cleanedResolvConf))
+	if err != nil {
+		return nil, err
+	}
+	return &File{Content: cleanedResolvConf, Hash: hash}, nil
+}
+
+// getLines parses input into lines and strips away comments.
+func getLines(input []byte, commentMarker []byte) [][]byte {
+	lines := bytes.Split(input, []byte("\n"))
+	var output [][]byte
+	for _, currentLine := range lines {
+		var commentIndex = bytes.Index(currentLine, commentMarker)
+		if commentIndex == -1 {
+			output = append(output, currentLine)
+		} else {
+			output = append(output, currentLine[:commentIndex])
+		}
+	}
+	return output
+}
+
+// GetNameservers returns nameservers (if any) listed in /etc/resolv.conf
+func GetNameservers(resolvConf []byte) []string {
+	nameservers := []string{}
+	for _, line := range getLines(resolvConf, []byte("#")) {
+		ns := nsRegexp.FindSubmatch(line)
+		if len(ns) > 0 {
+			nameservers = append(nameservers, string(ns[1]))
+		}
+	}
+	return nameservers
+}
+
+// GetNameserversAsCIDR returns nameservers (if any) listed in
+// /etc/resolv.conf as CIDR blocks (e.g., "1.2.3.4/32")
+// This function's output is intended for net.ParseCIDR
+func GetNameserversAsCIDR(resolvConf []byte) []string {
+	nameservers := []string{}
+	for _, nameserver := range GetNameservers(resolvConf) {
+		var address string
+		// If IPv6, strip zone if present
+		if strings.Contains(nameserver, ":") {
+			address = strings.Split(nameserver, "%")[0] + "/128"
+		} else {
+			address = nameserver + "/32"
+		}
+		nameservers = append(nameservers, address)
+	}
+	return nameservers
+}
+
+// GetSearchDomains returns search domains (if any) listed in /etc/resolv.conf
+// If more than one search line is encountered, only the contents of the last
+// one is returned.
+func GetSearchDomains(resolvConf []byte) []string {
+	domains := []string{}
+	for _, line := range getLines(resolvConf, []byte("#")) {
+		match := searchRegexp.FindSubmatch(line)
+		if match == nil {
+			continue
+		}
+		domains = strings.Fields(string(match[1]))
+	}
+	return domains
+}
+
+// GetOptions returns options (if any) listed in /etc/resolv.conf
+// If more than one options line is encountered, only the contents of the last
+// one is returned.
+func GetOptions(resolvConf []byte) []string {
+	options := []string{}
+	for _, line := range getLines(resolvConf, []byte("#")) {
+		match := optionsRegexp.FindSubmatch(line)
+		if match == nil {
+			continue
+		}
+		options = strings.Fields(string(match[1]))
+	}
+	return options
+}
+
+// Build writes a configuration file to path containing a "nameserver" entry
+// for every element in dns, a "search" entry for every element in
+// dnsSearch, and an "options" entry for every element in dnsOptions.
+func Build(path string, dns, dnsSearch, dnsOptions []string) (*File, error) {
+	content := bytes.NewBuffer(nil)
+	if len(dnsSearch) > 0 {
+		if searchString := strings.Join(dnsSearch, " "); strings.Trim(searchString, " ") != "." {
+			if _, err := content.WriteString("search " + searchString + "\n"); err != nil {
+				return nil, err
+			}
+		}
+	}
+	for _, dns := range dns {
+		if _, err := content.WriteString("nameserver " + dns + "\n"); err != nil {
+			return nil, err
+		}
+	}
+	if len(dnsOptions) > 0 {
+		if optsString := strings.Join(dnsOptions, " "); strings.Trim(optsString, " ") != "" {
+			if _, err := content.WriteString("options " + optsString + "\n"); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	hash, err := ioutils.HashData(bytes.NewReader(content.Bytes()))
+	if err != nil {
+		return nil, err
+	}
+
+	return &File{Content: content.Bytes(), Hash: hash}, ioutil.WriteFile(path, content.Bytes(), 0644)
+}