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