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//go:build linux
// +build linux
// Network utility functions.
package netutils
import (
"net"
"os"
"github.com/docker/docker/libnetwork/ns"
"github.com/docker/docker/libnetwork/resolvconf"
"github.com/docker/docker/libnetwork/types"
"github.com/pkg/errors"
"github.com/vishvananda/netlink"
)
var networkGetRoutesFct func(netlink.Link, int) ([]netlink.Route, error)
// CheckRouteOverlaps checks whether the passed network overlaps with any existing routes
func CheckRouteOverlaps(toCheck *net.IPNet) error {
networkGetRoutesFct := networkGetRoutesFct
if networkGetRoutesFct == nil {
networkGetRoutesFct = ns.NlHandle().RouteList
}
networks, err := networkGetRoutesFct(nil, netlink.FAMILY_V4)
if err != nil {
return err
}
for _, network := range networks {
if network.Dst != nil && network.Scope == netlink.SCOPE_LINK && NetworkOverlaps(toCheck, network.Dst) {
return ErrNetworkOverlaps
}
}
return nil
}
// GenerateIfaceName returns an interface name using the passed in
// prefix and the length of random bytes. The api ensures that the
// there are is no interface which exists with that name.
func GenerateIfaceName(nlh *netlink.Handle, prefix string, len int) (string, error) {
linkByName := netlink.LinkByName
if nlh != nil {
linkByName = nlh.LinkByName
}
for i := 0; i < 3; i++ {
name, err := GenerateRandomName(prefix, len)
if err != nil {
return "", err
}
_, err = linkByName(name)
if err != nil {
if errors.As(err, &netlink.LinkNotFoundError{}) {
return name, nil
}
return "", err
}
}
return "", types.InternalErrorf("could not generate interface name")
}
// FindAvailableNetwork returns a network from the passed list which does not
// overlap with existing interfaces in the system
func FindAvailableNetwork(list []*net.IPNet) (*net.IPNet, error) {
// We don't check for an error here, because we don't really care if we
// can't read /etc/resolv.conf. So instead we skip the append if resolvConf
// is nil. It either doesn't exist, or we can't read it for some reason.
var nameservers []string
if rc, err := os.ReadFile(resolvconf.Path()); err == nil {
nameservers = resolvconf.GetNameserversAsCIDR(rc)
}
for _, nw := range list {
if err := CheckNameserverOverlaps(nameservers, nw); err == nil {
if err := CheckRouteOverlaps(nw); err == nil {
return nw, nil
}
}
}
return nil, errors.New("no available network")
}
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