From 716b0cd3b4de062085aae5661f8e208bf3ce6628 Mon Sep 17 00:00:00 2001 From: Phil Estes Date: Tue, 10 Mar 2015 10:22:29 -0400 Subject: [PATCH] Add warning for --dns flag set to localhost addresses. We should warn users who use the `--dns` command line option to point DNS to a localhost address, either IPv4 or IPv6. Unless they have specifically set up the container as a DNS server or are using --net=host (which is why this should be allowed, but warned on because those are pretty unique cases) a localhost address as a resolver will not reach what they might expect (e.g. expecting it will hit localhost on the Docker daemon/host). Added a test for the message, and fixed up tests to separate stdout and stderr that were using `--dns=127.0.0.1` to test the options. Docker-DCO-1.1-Signed-off-by: Phil Estes (github: estesp) --- networkfs/resolvconf/resolvconf.go | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/networkfs/resolvconf/resolvconf.go b/networkfs/resolvconf/resolvconf.go index d88074f..61f92d9 100644 --- a/networkfs/resolvconf/resolvconf.go +++ b/networkfs/resolvconf/resolvconf.go @@ -23,11 +23,13 @@ var ( // 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})` + ipLocalhost = `((127\.([0-9]{1,3}.){2}[0-9]{1,3})|(::1))` - localhostRegexp = regexp.MustCompile(`(?m)^nameserver\s+((127\.([0-9]{1,3}.){2}[0-9]{1,3})|(::1))\s*\n*`) - nsIPv6Regexp = regexp.MustCompile(`(?m)^nameserver\s+` + ipv6Address + `\s*\n*`) - nsRegexp = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`) - searchRegexp = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`) + localhostIPRegexp = regexp.MustCompile(ipLocalhost) + localhostNSRegexp = regexp.MustCompile(`(?m)^nameserver\s+` + ipLocalhost + `\s*\n*`) + nsIPv6Regexp = regexp.MustCompile(`(?m)^nameserver\s+` + ipv6Address + `\s*\n*`) + nsRegexp = regexp.MustCompile(`^\s*nameserver\s*((` + ipv4Address + `)|(` + ipv6Address + `))\s*$`) + searchRegexp = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`) ) var lastModified struct { @@ -87,7 +89,7 @@ func GetLastModified() ([]byte, string) { // It also returns a boolean to notify the caller if changes were made at all func FilterResolvDns(resolvConf []byte, ipv6Enabled bool) ([]byte, bool) { changed := false - cleanedResolvConf := localhostRegexp.ReplaceAll(resolvConf, []byte{}) + cleanedResolvConf := localhostNSRegexp.ReplaceAll(resolvConf, []byte{}) // if IPv6 is not enabled, also clean out any IPv6 address nameserver if !ipv6Enabled { cleanedResolvConf = nsIPv6Regexp.ReplaceAll(cleanedResolvConf, []byte{}) @@ -124,6 +126,13 @@ func getLines(input []byte, commentMarker []byte) [][]byte { return output } +// returns true if the IP string matches the localhost IP regular expression. +// Used for determining if nameserver settings are being passed which are +// localhost addresses +func IsLocalhost(ip string) bool { + return localhostIPRegexp.MatchString(ip) +} + // GetNameservers returns nameservers (if any) listed in /etc/resolv.conf func GetNameservers(resolvConf []byte) []string { nameservers := []string{}