dotcloud/docker

package bridge

import (
    "context"
    "errors"
    "fmt"
    "os"
    "path/filepath"
    "syscall"

    "github.com/containerd/log"
    "github.com/docker/docker/libnetwork/netutils"
    "github.com/vishvananda/netlink"
)

// SetupDevice create a new bridge interface/
func setupDevice(config *networkConfiguration, i *bridgeInterface) error {
    // We only attempt to create the bridge when the requested device name is
    // the default one. The default bridge name can be overridden with the
    // DOCKER_TEST_CREATE_DEFAULT_BRIDGE env var. It should be used only for
    // test purpose.
    var defaultBridgeName string
    if defaultBridgeName = os.Getenv("DOCKER_TEST_CREATE_DEFAULT_BRIDGE"); defaultBridgeName == "" {
        defaultBridgeName = DefaultBridgeName
    }
    if config.BridgeName != defaultBridgeName && config.DefaultBridge {
        return NonDefaultBridgeExistError(config.BridgeName)
    }

    // Set the bridgeInterface netlink.Bridge.
    i.Link = &netlink.Bridge{
        LinkAttrs: netlink.LinkAttrs{
            Name: config.BridgeName,
        },
    }

    // Set the bridge's MAC address. Requires kernel version 3.3 or up.
    hwAddr := netutils.GenerateRandomMAC()
    i.Link.Attrs().HardwareAddr = hwAddr
    log.G(context.TODO()).Debugf("Setting bridge mac address to %s", hwAddr)

    if err := i.nlh.LinkAdd(i.Link); err != nil {
        log.G(context.TODO()).WithError(err).Errorf("Failed to create bridge %s via netlink", config.BridgeName)
        return err
    }

    return nil
}

func setupMTU(config *networkConfiguration, i *bridgeInterface) error {
    if err := i.nlh.LinkSetMTU(i.Link, config.Mtu); err != nil {
        // Before Linux v4.17, bridges couldn't be configured "manually" with an MTU greater than 1500, although it
        // could be autoconfigured with such a value when interfaces were added to the bridge. In that case, the
        // bridge MTU would be set automatically by the kernel to the lowest MTU of all interfaces attached. To keep
        // compatibility with older kernels, we need to discard -EINVAL.
        // TODO(aker): remove this once we drop support for CentOS/RHEL 7.
        if config.Mtu > 1500 && config.Mtu <= 0xFFFF && errors.Is(err, syscall.EINVAL) {
            return nil
        }
        log.G(context.TODO()).WithError(err).Errorf("Failed to set bridge MTU %s via netlink", config.BridgeName)
        return err
    }
    return nil
}

func setupDefaultSysctl(config *networkConfiguration, i *bridgeInterface) error {
    // Disable IPv6 router advertisements originating on the bridge
    sysPath := filepath.Join("/proc/sys/net/ipv6/conf/", config.BridgeName, "accept_ra")
    if _, err := os.Stat(sysPath); err != nil {
        log.G(context.TODO()).
            WithField("bridge", config.BridgeName).
            WithField("syspath", sysPath).
            Info("failed to read ipv6 net.ipv6.conf.<bridge>.accept_ra")
        return nil
    }
    if err := os.WriteFile(sysPath, []byte{'0', '\n'}, 0o644); err != nil {
        log.G(context.TODO()).WithError(err).Warn("unable to disable IPv6 router advertisement")
    }
    return nil
}

// SetupDeviceUp ups the given bridge interface.
func setupDeviceUp(config *networkConfiguration, i *bridgeInterface) error {
    err := i.nlh.LinkSetUp(i.Link)
    if err != nil {
        return fmt.Errorf("Failed to set link up for %s: %v", config.BridgeName, err)
    }

    // Attempt to update the bridge interface to refresh the flags status,
    // ignoring any failure to do so.
    if lnk, err := i.nlh.LinkByName(config.BridgeName); err == nil {
        i.Link = lnk
    } else {
        log.G(context.TODO()).Warnf("Failed to retrieve link for interface (%s): %v", config.BridgeName, err)
    }
    return nil
}