github.com/jfrazelle/docker@v1.1.2-0.20210712172922-bf78e25fe508/libnetwork/netutils/utils_linux.go (about)

     1  // +build linux
     2  // Network utility functions.
     3  
     4  package netutils
     5  
     6  import (
     7  	"fmt"
     8  	"net"
     9  	"strings"
    10  
    11  	"github.com/docker/docker/libnetwork/ipamutils"
    12  	"github.com/docker/docker/libnetwork/ns"
    13  	"github.com/docker/docker/libnetwork/osl"
    14  	"github.com/docker/docker/libnetwork/resolvconf"
    15  	"github.com/docker/docker/libnetwork/types"
    16  	"github.com/pkg/errors"
    17  	"github.com/vishvananda/netlink"
    18  )
    19  
    20  var (
    21  	networkGetRoutesFct func(netlink.Link, int) ([]netlink.Route, error)
    22  )
    23  
    24  // CheckRouteOverlaps checks whether the passed network overlaps with any existing routes
    25  func CheckRouteOverlaps(toCheck *net.IPNet) error {
    26  	if networkGetRoutesFct == nil {
    27  		networkGetRoutesFct = ns.NlHandle().RouteList
    28  	}
    29  	networks, err := networkGetRoutesFct(nil, netlink.FAMILY_V4)
    30  	if err != nil {
    31  		return err
    32  	}
    33  	for _, network := range networks {
    34  		if network.Dst != nil && NetworkOverlaps(toCheck, network.Dst) {
    35  			return ErrNetworkOverlaps
    36  		}
    37  	}
    38  	return nil
    39  }
    40  
    41  // GenerateIfaceName returns an interface name using the passed in
    42  // prefix and the length of random bytes. The api ensures that the
    43  // there are is no interface which exists with that name.
    44  func GenerateIfaceName(nlh *netlink.Handle, prefix string, len int) (string, error) {
    45  	linkByName := netlink.LinkByName
    46  	if nlh != nil {
    47  		linkByName = nlh.LinkByName
    48  	}
    49  	for i := 0; i < 3; i++ {
    50  		name, err := GenerateRandomName(prefix, len)
    51  		if err != nil {
    52  			continue
    53  		}
    54  		_, err = linkByName(name)
    55  		if err != nil {
    56  			if strings.Contains(err.Error(), "not found") {
    57  				return name, nil
    58  			}
    59  			return "", err
    60  		}
    61  	}
    62  	return "", types.InternalErrorf("could not generate interface name")
    63  }
    64  
    65  // ElectInterfaceAddresses looks for an interface on the OS with the
    66  // specified name and returns returns all its IPv4 and IPv6 addresses in CIDR notation.
    67  // If a failure in retrieving the addresses or no IPv4 address is found, an error is returned.
    68  // If the interface does not exist, it chooses from a predefined
    69  // list the first IPv4 address which does not conflict with other
    70  // interfaces on the system.
    71  func ElectInterfaceAddresses(name string) ([]*net.IPNet, []*net.IPNet, error) {
    72  	var v4Nets, v6Nets []*net.IPNet
    73  
    74  	defer osl.InitOSContext()()
    75  
    76  	link, _ := ns.NlHandle().LinkByName(name)
    77  	if link != nil {
    78  		v4addr, err := ns.NlHandle().AddrList(link, netlink.FAMILY_V4)
    79  		if err != nil {
    80  			return nil, nil, err
    81  		}
    82  		v6addr, err := ns.NlHandle().AddrList(link, netlink.FAMILY_V6)
    83  		if err != nil {
    84  			return nil, nil, err
    85  		}
    86  		for _, nlAddr := range v4addr {
    87  			v4Nets = append(v4Nets, nlAddr.IPNet)
    88  		}
    89  		for _, nlAddr := range v6addr {
    90  			v6Nets = append(v6Nets, nlAddr.IPNet)
    91  		}
    92  	}
    93  
    94  	if link == nil || len(v4Nets) == 0 {
    95  		// Choose from predefined local scope networks
    96  		v4Net, err := FindAvailableNetwork(ipamutils.PredefinedLocalScopeDefaultNetworks)
    97  		if err != nil {
    98  			return nil, nil, errors.Wrapf(err, "PredefinedLocalScopeDefaultNetworks List: %+v",
    99  				ipamutils.PredefinedLocalScopeDefaultNetworks)
   100  		}
   101  		v4Nets = append(v4Nets, v4Net)
   102  	}
   103  
   104  	return v4Nets, v6Nets, nil
   105  }
   106  
   107  // FindAvailableNetwork returns a network from the passed list which does not
   108  // overlap with existing interfaces in the system
   109  func FindAvailableNetwork(list []*net.IPNet) (*net.IPNet, error) {
   110  	// We don't check for an error here, because we don't really care if we
   111  	// can't read /etc/resolv.conf. So instead we skip the append if resolvConf
   112  	// is nil. It either doesn't exist, or we can't read it for some reason.
   113  	var nameservers []string
   114  	if rc, err := resolvconf.Get(); err == nil {
   115  		nameservers = resolvconf.GetNameserversAsCIDR(rc.Content)
   116  	}
   117  	for _, nw := range list {
   118  		if err := CheckNameserverOverlaps(nameservers, nw); err == nil {
   119  			if err := CheckRouteOverlaps(nw); err == nil {
   120  				return nw, nil
   121  			}
   122  		}
   123  	}
   124  	return nil, fmt.Errorf("no available network")
   125  }