Make networking code reusable

To prevent code duplication when creating new network backends move
reusable code into a separate internal package.

This allows all network backends to use the same code as long as they
implement the new NetUtil interface.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

1 files changed, 70 insertions, 0 deletions

diff --git a/libpod/network/internal/util/ip.go b/libpod/network/internal/util/ip.go
new file mode 100644
index 000000000..7fe35d3d4
--- /dev/null
+++ b/libpod/network/internal/util/ip.go
@@ -0,0 +1,70 @@
+package util
+
+import (
+	"crypto/rand"
+	"net"
+
+	"github.com/pkg/errors"
+)
+
+func incByte(subnet *net.IPNet, idx int, shift uint) error {
+	if idx < 0 {
+		return errors.New("no more subnets left")
+	}
+	if subnet.IP[idx] == 255 {
+		subnet.IP[idx] = 0
+		return incByte(subnet, idx-1, 0)
+	}
+	subnet.IP[idx] += 1 << shift
+	return nil
+}
+
+// NextSubnet returns subnet incremented by 1
+func NextSubnet(subnet *net.IPNet) (*net.IPNet, error) {
+	newSubnet := &net.IPNet{
+		IP:   subnet.IP,
+		Mask: subnet.Mask,
+	}
+	ones, bits := newSubnet.Mask.Size()
+	if ones == 0 {
+		return nil, errors.Errorf("%s has only one subnet", subnet.String())
+	}
+	zeroes := uint(bits - ones)
+	shift := zeroes % 8
+	idx := ones/8 - 1
+	if idx < 0 {
+		idx = 0
+	}
+	if err := incByte(newSubnet, idx, shift); err != nil {
+		return nil, err
+	}
+	return newSubnet, nil
+}
+
+func NetworkIntersectsWithNetworks(n *net.IPNet, networklist []*net.IPNet) bool {
+	for _, nw := range networklist {
+		if networkIntersect(n, nw) {
+			return true
+		}
+	}
+	return false
+}
+
+func networkIntersect(n1, n2 *net.IPNet) bool {
+	return n2.Contains(n1.IP) || n1.Contains(n2.IP)
+}
+
+// getRandomIPv6Subnet returns a random internal ipv6 subnet as described in RFC3879.
+func getRandomIPv6Subnet() (net.IPNet, error) {
+	ip := make(net.IP, 8, net.IPv6len)
+	// read 8 random bytes
+	_, err := rand.Read(ip)
+	if err != nil {
+		return net.IPNet{}, nil
+	}
+	// first byte must be FD as per RFC3879
+	ip[0] = 0xfd
+	// add 8 zero bytes
+	ip = append(ip, make([]byte, 8)...)
+	return net.IPNet{IP: ip, Mask: net.CIDRMask(64, 128)}, nil
+}