AdGuardHome/internal/dhcpsvc/v6.go

173 lines
4.8 KiB
Go

package dhcpsvc
import (
"context"
"fmt"
"log/slog"
"net/netip"
"slices"
"time"
"github.com/AdguardTeam/golibs/errors"
"github.com/AdguardTeam/golibs/netutil"
"github.com/google/gopacket/layers"
)
// IPv6Config is the interface-specific configuration for DHCPv6.
type IPv6Config struct {
// RangeStart is the first address in the range to assign to DHCP clients.
RangeStart netip.Addr
// Options is the list of DHCP options to send to DHCP clients. The options
// with zero length are treated as deletions of the corresponding options,
// either implicit or explicit.
Options layers.DHCPv6Options
// LeaseDuration is the TTL of a DHCP lease.
LeaseDuration time.Duration
// RASlaacOnly defines whether the DHCP clients should only use SLAAC for
// address assignment.
RASLAACOnly bool
// RAAllowSlaac defines whether the DHCP clients may use SLAAC for address
// assignment.
RAAllowSLAAC bool
// Enabled is the state of the DHCPv6 service, whether it is enabled or not
// on the specific interface.
Enabled bool
}
// validate returns an error in conf if any.
func (c *IPv6Config) validate() (err error) {
if c == nil {
return errNilConfig
} else if !c.Enabled {
return nil
}
var errs []error
if !c.RangeStart.Is6() {
err = fmt.Errorf("range start %s should be a valid ipv6", c.RangeStart)
errs = append(errs, err)
}
if c.LeaseDuration <= 0 {
err = fmt.Errorf("lease duration %s must be positive", c.LeaseDuration)
errs = append(errs, err)
}
return errors.Join(errs...)
}
// dhcpInterfaceV6 is a DHCP interface for IPv6 address family.
type dhcpInterfaceV6 struct {
// common is the common part of any network interface within the DHCP
// server.
common *netInterface
// rangeStart is the first IP address in the range.
rangeStart netip.Addr
// implicitOpts are the DHCPv6 options listed in RFC 8415 (and others) and
// initialized with default values. It must not have intersections with
// explicitOpts.
implicitOpts layers.DHCPv6Options
// explicitOpts are the user-configured options. It must not have
// intersections with implicitOpts.
explicitOpts layers.DHCPv6Options
// raSLAACOnly defines if DHCP should send ICMPv6.RA packets without MO
// flags.
raSLAACOnly bool
// raAllowSLAAC defines if DHCP should send ICMPv6.RA packets with MO flags.
raAllowSLAAC bool
}
// newDHCPInterfaceV6 creates a new DHCP interface for IPv6 address family with
// the given configuration.
//
// TODO(e.burkov): Validate properly.
func newDHCPInterfaceV6(
ctx context.Context,
l *slog.Logger,
name string,
conf *IPv6Config,
) (i *dhcpInterfaceV6) {
l = l.With(keyInterface, name, keyFamily, netutil.AddrFamilyIPv6)
if !conf.Enabled {
l.DebugContext(ctx, "disabled")
return nil
}
i = &dhcpInterfaceV6{
rangeStart: conf.RangeStart,
common: newNetInterface(name, l, conf.LeaseDuration),
raSLAACOnly: conf.RASLAACOnly,
raAllowSLAAC: conf.RAAllowSLAAC,
}
i.implicitOpts, i.explicitOpts = conf.options(ctx, l)
return i
}
// dhcpInterfacesV6 is a slice of network interfaces of IPv6 address family.
type dhcpInterfacesV6 []*dhcpInterfaceV6
// find returns the first network interface within ifaces containing ip. It
// returns false if there is no such interface.
func (ifaces dhcpInterfacesV6) find(ip netip.Addr) (iface6 *netInterface, ok bool) {
// prefLen is the length of prefix to match ip against.
//
// TODO(e.burkov): DHCPv6 inherits the weird behavior of legacy
// implementation where the allocated range constrained by the first address
// and the first address with last byte set to 0xff. Proper prefixes should
// be used instead.
const prefLen = netutil.IPv6BitLen - 8
i := slices.IndexFunc(ifaces, func(iface *dhcpInterfaceV6) (contains bool) {
return !ip.Less(iface.rangeStart) &&
netip.PrefixFrom(iface.rangeStart, prefLen).Contains(ip)
})
if i < 0 {
return nil, false
}
return ifaces[i].common, true
}
// options returns the implicit and explicit options for the interface. The two
// lists are disjoint and the implicit options are initialized with default
// values.
//
// TODO(e.burkov): Add implicit options according to RFC.
func (c *IPv6Config) options(ctx context.Context, l *slog.Logger) (imp, exp layers.DHCPv6Options) {
// Set default values of host configuration parameters listed in RFC 8415.
imp = layers.DHCPv6Options{}
slices.SortFunc(imp, compareV6OptionCodes)
// Set values for explicitly configured options.
for _, e := range c.Options {
i, found := slices.BinarySearchFunc(imp, e, compareV6OptionCodes)
if found {
imp = slices.Delete(imp, i, i+1)
}
exp = append(exp, e)
}
l.DebugContext(ctx, "options", "implicit", imp, "explicit", exp)
return imp, exp
}
// compareV6OptionCodes compares option codes of a and b.
func compareV6OptionCodes(a, b layers.DHCPv6Option) (res int) {
return int(a.Code) - int(b.Code)
}