AdGuardHome/internal/dhcpsvc/v4.go

114 lines
3.2 KiB
Go

package dhcpsvc
import (
"fmt"
"net"
"net/netip"
"time"
"github.com/google/gopacket/layers"
)
// IPv4Config is the interface-specific configuration for DHCPv4.
type IPv4Config struct {
// GatewayIP is the IPv4 address of the network's gateway. It is used as
// the default gateway for DHCP clients and also used in calculating the
// network-specific broadcast address.
GatewayIP netip.Addr
// SubnetMask is the IPv4 subnet mask of the network. It should be a valid
// IPv4 CIDR (i.e. all 1s followed by all 0s).
SubnetMask netip.Addr
// RangeStart is the first address in the range to assign to DHCP clients.
RangeStart netip.Addr
// RangeEnd is the last address in the range to assign to DHCP clients.
RangeEnd netip.Addr
// Options is the list of DHCP options to send to DHCP clients.
Options layers.DHCPOptions
// LeaseDuration is the TTL of a DHCP lease.
LeaseDuration time.Duration
// Enabled is the state of the DHCPv4 service, whether it is enabled or not
// on the specific interface.
Enabled bool
}
// validate returns an error in conf if any.
func (conf *IPv4Config) validate() (err error) {
switch {
case conf == nil:
return errNilConfig
case !conf.Enabled:
return nil
case !conf.GatewayIP.Is4():
return mustBeErr("gateway ip", "be a valid ipv4", conf.GatewayIP)
case !conf.SubnetMask.Is4():
return mustBeErr("subnet mask", "be a valid ipv4 cidr mask", conf.SubnetMask)
case !conf.RangeStart.Is4():
return mustBeErr("range start", "be a valid ipv4", conf.RangeStart)
case !conf.RangeEnd.Is4():
return mustBeErr("range end", "be a valid ipv4", conf.RangeEnd)
case conf.LeaseDuration <= 0:
return mustBeErr("lease duration", "be less than %d", conf.LeaseDuration)
default:
return nil
}
}
// iface4 is a DHCP interface for IPv4 address family.
type iface4 struct {
// gateway is the IP address of the network gateway.
gateway netip.Addr
// subnet is the network subnet.
subnet netip.Prefix
// addrSpace is the IPv4 address space allocated for leasing.
addrSpace ipRange
// name is the name of the interface.
name string
// TODO(e.burkov): Add options.
// leaseTTL is the time-to-live of dynamic leases on this interface.
leaseTTL time.Duration
}
// newIface4 creates a new DHCP interface for IPv4 address family with the given
// configuration. It returns an error if the given configuration can't be used.
func newIface4(name string, conf *IPv4Config) (i *iface4, err error) {
if !conf.Enabled {
return nil, nil
}
maskLen, _ := net.IPMask(conf.SubnetMask.AsSlice()).Size()
subnet := netip.PrefixFrom(conf.GatewayIP, maskLen)
switch {
case !subnet.Contains(conf.RangeStart):
return nil, fmt.Errorf("range start %s is not within %s", conf.RangeStart, subnet)
case !subnet.Contains(conf.RangeEnd):
return nil, fmt.Errorf("range end %s is not within %s", conf.RangeEnd, subnet)
}
addrSpace, err := newIPRange(conf.RangeStart, conf.RangeEnd)
if err != nil {
return nil, err
} else if addrSpace.contains(conf.GatewayIP) {
return nil, fmt.Errorf("gateway ip %s in the ip range %s", conf.GatewayIP, addrSpace)
}
return &iface4{
name: name,
gateway: conf.GatewayIP,
subnet: subnet,
addrSpace: addrSpace,
leaseTTL: conf.LeaseDuration,
}, nil
}