fix(pasta): assign a fixed IPv6 address, gateway, and DNS to the netns

hack/integration-ipv6.sh

@@ -15,11 +15,17 @@ echo "hello ipv6" >${tmp}/index.html
 busybox httpd -f -p "[${parent_ipv6}]:8080" -h "${tmp}" &
 pid=$!
 
-$ROOTLESSKIT \
-	--net=slirp4netns \
-	--ipv6 \
-	sh -euc "sleep 3; exec curl -fsSL http://[${parent_ipv6}]:8080"
+cleanup() {
+	kill -9 $pid || true
+	sudo ip link del ${parent_dummy} || true
+	rm -rf ${tmp}
+}
+trap cleanup EXIT
 
-kill -9 $pid || true
-sudo ip link del ${parent_dummy}
-rm -rf ${tmp}
+for net in 'slirp4netns' 'pasta'
+do
+	$ROOTLESSKIT \
+		--net=${net} \
+		--ipv6 \
+		sh -euc "sleep 3; exec curl -fsSL http://[${parent_ipv6}]:8080"
+done

pkg/network/iputils/iputils.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"math"
+	"math/big"
 	"net"
 )
 
@@ -21,3 +22,18 @@ func AddIPInt(ip net.IP, i int) (net.IP, error) {
 	binary.BigEndian.PutUint32(res, uint32(resInt64))
 	return res, nil
 }
+
+func AddIPInt6(ip net.IP, i int) (net.IP, error) {
+	ip6 := ip.To16()
+	if ip.To4() != nil || ip6 == nil {
+		return nil, fmt.Errorf("expected IPv6 address, got %s", ip.String())
+	}
+	b := new(big.Int).SetBytes(ip6)
+	b.Add(b, big.NewInt(int64(i)))
+	if b.Sign() < 0 || b.BitLen() > 128 {
+		return nil, fmt.Errorf("%s + %d overflows", ip.String(), i)
+	}
+	res := make(net.IP, net.IPv6len)
+	b.FillBytes(res)
+	return res, nil
+}

pkg/network/iputils/iputils_test.go

@@ -49,3 +49,58 @@ func TestAddIPInt(t *testing.T) {
 		}
 	}
 }
+
+func TestAddIPInt6(t *testing.T) {
+	type testCase struct {
+		s        string
+		i        int
+		expected string
+	}
+	testCases := []testCase{
+		{
+			"fd00::",
+			0x2,
+			"fd00::2",
+		},
+		{
+			"fd00::",
+			0x100,
+			"fd00::100",
+		},
+		{
+			"fd00::ffff",
+			0x1,
+			"fd00::1:0",
+		},
+		{
+			"ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff",
+			0x1,
+			"",
+		},
+		{
+			"10.0.2.0",
+			100,
+			"",
+		},
+	}
+	for i, tc := range testCases {
+		ip := net.ParseIP(tc.s)
+		if ip == nil {
+			t.Fatalf("invalid IP: %q", tc.s)
+		}
+		gotIP, err := AddIPInt6(ip, tc.i)
+		if tc.expected == "" {
+			if err == nil {
+				t.Fatalf("#%d: expected error, got no error", i)
+			}
+		} else {
+			if err != nil {
+				t.Fatalf("#%d: expected no error, got %q", i, err)
+			}
+			got := gotIP.String()
+			if got != tc.expected {
+				t.Fatalf("#%d: expected %q, got %q", i, tc.expected, got)
+			}
+		}
+	}
+}

pkg/network/pasta/pasta.go

@@ -76,6 +76,10 @@ func NewParentDriver(logWriter io.Writer, binary string, mtu int, ipnet *net.IPN
 			return nil, err
 		}
 	}
+	_, ipnet6, err := net.ParseCIDR("fd00::/64")
+	if err != nil {
+		return nil, err
+	}
 
 	if ifname == "" {
 		ifname = "tap0"
@@ -95,6 +99,7 @@ func NewParentDriver(logWriter io.Writer, binary string, mtu int, ipnet *net.IPN
 		binary:                 binary,
 		mtu:                    mtu,
 		ipnet:                  ipnet,
+		ipnet6:                 ipnet6,
 		disableHostLoopback:    disableHostLoopback,
 		enableIPv6:             enableIPv6,
 		ifname:                 ifname,
@@ -109,6 +114,7 @@ type parentDriver struct {
 	binary                 string
 	mtu                    int
 	ipnet                  *net.IPNet
+	ipnet6                 *net.IPNet
 	disableHostLoopback    bool
 	enableIPv6             bool
 	ifname                 string
@@ -170,7 +176,23 @@ func (d *parentDriver) ConfigureNetwork(childPID int, stateDir, detachedNetNSPat
 	if d.disableHostLoopback {
 		opts = append(opts, "--no-map-gw", "--tcp-ns=none", "--udp-ns=none")
 	}
-	if !d.enableIPv6 {
+	if d.enableIPv6 {
+		// 0x100, so that the address is rendered as fd00::100
+		address, err := iputils.AddIPInt6(d.ipnet6.IP, 0x100)
+		if err != nil {
+			return nil, common.Seq(cleanups), err
+		}
+		gateway, err := iputils.AddIPInt6(d.ipnet6.IP, 2)
+		if err != nil {
+			return nil, common.Seq(cleanups), err
+		}
+		dns, err := iputils.AddIPInt6(d.ipnet6.IP, 3)
+		if err != nil {
+			return nil, common.Seq(cleanups), err
+		}
+		opts = append(opts, "--address="+address.String(), "--gateway="+gateway.String(),
+			"--dns-forward="+dns.String())
+	} else {
 		opts = append(opts, "--ipv4-only")
 	}
 	if d.implicitPortForwarding {