moby/libnetwork/drivers/bridge/setup_verify_linux.go

package bridge

import (
	"fmt"
	"strings"

	"github.com/docker/docker/libnetwork/ns"
	"github.com/vishvananda/netlink"
)

// setupVerifyAndReconcileIPv4 checks what IPv4 addresses the given i interface has
// and ensures that they match the passed network config.
func setupVerifyAndReconcileIPv4(config *networkConfiguration, i *bridgeInterface) error {
	// Fetch a slice of IPv4 addresses and a slice of IPv6 addresses from the bridge.
	addrsv4, err := i.addresses(netlink.FAMILY_V4)
	if err != nil {
		return fmt.Errorf("Failed to verify ip addresses: %v", err)
	}

	addrv4, _ := selectIPv4Address(addrsv4, config.AddressIPv4)

	// Verify that the bridge has an IPv4 address.
	if !config.Internal && addrv4.IPNet == nil {
		return &ErrNoIPAddr{}
	}

	// Verify that the bridge IPv4 address matches the requested configuration.
	if config.AddressIPv4 != nil && addrv4.IPNet != nil && !addrv4.IP.Equal(config.AddressIPv4.IP) {
		return &IPv4AddrNoMatchError{IP: addrv4.IP, CfgIP: config.AddressIPv4.IP}
	}

	return nil
}

func bridgeInterfaceExists(name string) (bool, error) {
	nlh := ns.NlHandle()
	link, err := nlh.LinkByName(name)
	if err != nil {
		if strings.Contains(err.Error(), "Link not found") {
			return false, nil
		}
		return false, fmt.Errorf("failed to check bridge interface existence: %v", err)
	}

	if link.Type() == "bridge" {
		return true, nil
	}
	return false, fmt.Errorf("existing interface %s is not a bridge", name)
}