Merge pull request #10541 from Luap99/fix-10158

add ipv6 nameservers only when the container has ipv6 enabled

libpod/container_internal_linux.go

@@ -1668,17 +1668,16 @@ func (c *Container) generateResolvConf() (string, error) {
 		return "", err
 	}
 
-	// Ensure that the container's /etc/resolv.conf is compatible with its
-	// network configuration.
-	// TODO: set ipv6 enable bool more sanely
-	resolv, err := resolvconf.FilterResolvDNS(contents, true, c.config.CreateNetNS)
-	if err != nil {
-		return "", errors.Wrapf(err, "error parsing host resolv.conf")
-	}
-
+	ipv6 := false
 	// Check if CNI gave back and DNS servers for us to add in
 	cniResponse := c.state.NetworkStatus
 	for _, i := range cniResponse {
+		for _, ip := range i.IPs {
+			// Note: only using To16() does not work since it also returns a vaild ip for ipv4
+			if ip.Address.IP.To4() == nil && ip.Address.IP.To16() != nil {
+				ipv6 = true
+			}
+		}
 		if i.DNS.Nameservers != nil {
 			cniNameServers = append(cniNameServers, i.DNS.Nameservers...)
 			logrus.Debugf("adding nameserver(s) from cni response of '%q'", i.DNS.Nameservers)
@@ -1689,6 +1688,25 @@ func (c *Container) generateResolvConf() (string, error) {
 		}
 	}
 
+	if c.config.NetMode.IsSlirp4netns() {
+		ctrNetworkSlipOpts := []string{}
+		if c.config.NetworkOptions != nil {
+			ctrNetworkSlipOpts = append(ctrNetworkSlipOpts, c.config.NetworkOptions["slirp4netns"]...)
+		}
+		slirpOpts, err := parseSlirp4netnsNetworkOptions(c.runtime, ctrNetworkSlipOpts)
+		if err != nil {
+			return "", err
+		}
+		ipv6 = slirpOpts.enableIPv6
+	}
+
+	// Ensure that the container's /etc/resolv.conf is compatible with its
+	// network configuration.
+	resolv, err := resolvconf.FilterResolvDNS(contents, ipv6, c.config.CreateNetNS)
+	if err != nil {
+		return "", errors.Wrapf(err, "error parsing host resolv.conf")
+	}
+
 	dns := make([]net.IP, 0, len(c.runtime.config.Containers.DNSServers))
 	for _, i := range c.runtime.config.Containers.DNSServers {
 		result := net.ParseIP(i)

test/system/500-networking.bats

@@ -329,4 +329,62 @@ load helpers
     run_podman network rm -f $mynetname
 }
 
+@test "podman ipv6 in /etc/resolv.conf" {
+    ipv6_regex='([0-9A-Fa-f]{0,4}:){2,7}([0-9A-Fa-f]{0,4})(%\w+)?'
+
+    # Make sure to read the correct /etc/resolv.conf file in case of systemd-resolved.
+    resolve_file=$(readlink -f /etc/resolv.conf)
+    if [[ "$resolve_file" == "/run/systemd/resolve/stub-resolv.conf" ]]; then
+        resolve_file="/run/systemd/resolve/resolv.conf"
+    fi
+
+    # If the host doesn't have an ipv6 in resolv.conf skip this test.
+    # We should never modify resolv.conf on the host.
+    if ! grep -E "$ipv6_regex" "$resolve_file"; then
+        skip "This test needs an ipv6 nameserver in $resolve_file"
+    fi
+
+    # ipv4 slirp
+    run_podman run --rm --network slirp4netns:enable_ipv6=false $IMAGE cat /etc/resolv.conf
+    if grep -E "$ipv6_regex" <<< $output; then
+        die "resolv.conf contains a ipv6 nameserver"
+    fi
+
+    # ipv6 slirp
+    run_podman run --rm --network slirp4netns:enable_ipv6=true $IMAGE cat /etc/resolv.conf
+    # "is" does not like the ipv6 regex
+    if ! grep -E "$ipv6_regex" <<< $output; then
+        die "resolv.conf does not contain a ipv6 nameserver"
+    fi
+
+    # ipv4 cni
+    local mysubnet=$(random_rfc1918_subnet)
+    local netname=testnet-$(random_string 10)
+
+    run_podman network create --subnet $mysubnet.0/24 $netname
+    is "$output" ".*/cni/net.d/$netname.conflist" "output of 'network create'"
+
+    run_podman run --rm --network $netname $IMAGE cat /etc/resolv.conf
+    if grep -E "$ipv6_regex" <<< $output; then
+        die "resolv.conf contains a ipv6 nameserver"
+    fi
+
+    run_podman network rm -f $netname
+
+    # ipv6 cni
+    mysubnet=fd00:4:4:4:4::/64
+    netname=testnet-$(random_string 10)
+
+    run_podman network create --subnet $mysubnet $netname
+    is "$output" ".*/cni/net.d/$netname.conflist" "output of 'network create'"
+
+    run_podman run --rm --network $netname $IMAGE cat /etc/resolv.conf
+    # "is" does not like the ipv6 regex
+    if ! grep -E "$ipv6_regex" <<< $output; then
+        die "resolv.conf does not contain a ipv6 nameserver"
+    fi
+
+    run_podman network rm -f $netname
+}
+
 # vim: filetype=sh