pasta: add IPv6 --map-guest-addr

Signed-off-by: Jan Rodák <hony.com@seznam.cz>

Author: Honny1

common/libnetwork/pasta/pasta_linux.go

@@ -36,6 +36,10 @@ const (
 	// mapGuestAddrIpv4 static ip used as forwarder address inside the netns to reach the host,
 	// given this is a "link local" ip it should be very unlikely that it causes conflicts.
 	mapGuestAddrIpv4 = "169.254.1.2"
+
+	// mapGuestAddrIpv6 static ip used as IPv6 forwarder address inside the netns to reach the host,
+	// pasta uses this to provide a routable source for inbound IPv6 connections forwarded via pesto.
+	mapGuestAddrIpv6 = "fc00::1"
 )
 
 type SetupOptions struct {
@@ -77,12 +81,12 @@ func Setup(opts *SetupOptions) (*SetupResult, error) {
 				// cannot hard require it yet. Once we are confident that the update is most distros we can remove it.
 				if exitErr.ExitCode() == 1 &&
 					strings.Contains(string(out), "unrecognized option '"+mapGuestAddrOpt) &&
-					len(mapGuestAddrIPs) == 1 && mapGuestAddrIPs[0] == mapGuestAddrIpv4 {
-					// we did add the default --map-guest-addr option, if users set something different we want
+					len(mapGuestAddrIPs) == 2 && mapGuestAddrIPs[0] == mapGuestAddrIpv4 && mapGuestAddrIPs[1] == mapGuestAddrIpv6 {
+					// we did add the default --map-guest-addr options, if users set something different we want
 					// to get to the error below. We have to unset mapGuestAddrIPs here to avoid a infinite loop.
 					mapGuestAddrIPs = nil
-					// Trim off last two args which are --map-guest-addr 169.254.1.2.
-					cmdArgs = cmdArgs[:len(cmdArgs)-2]
+					// Trim off last four args which are --map-guest-addr 169.254.1.2 --map-guest-addr fc00::1.
+					cmdArgs = cmdArgs[:len(cmdArgs)-4]
 					continue
 				}
 				return nil, fmt.Errorf("pasta failed with exit code %d:\n%s",
@@ -271,8 +275,8 @@ func createPastaArgs(opts *SetupOptions) ([]string, []string, []string, error) {
 	if len(mapGuestAddrIPs) == 0 {
 		// the user did not request custom --map-guest-addr so add our own so that we can use this
 		// for our own host.containers.internal host entry.
-		cmdArgs = append(cmdArgs, mapGuestAddrOpt, mapGuestAddrIpv4)
-		mapGuestAddrIPs = append(mapGuestAddrIPs, mapGuestAddrIpv4)
+		cmdArgs = append(cmdArgs, mapGuestAddrOpt, mapGuestAddrIpv4, mapGuestAddrOpt, mapGuestAddrIpv6)
+		mapGuestAddrIPs = append(mapGuestAddrIPs, mapGuestAddrIpv4, mapGuestAddrIpv6)
 	}
 
 	return cmdArgs, dnsForwardIPs, mapGuestAddrIPs, nil