AdGuardHome/dhcpd/router_adv.go

240 lines
5.5 KiB
Go

package dhcpd
import (
"encoding/binary"
"fmt"
"net"
"sync/atomic"
"time"
"github.com/AdguardTeam/golibs/log"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv6"
)
type raCtx struct {
raAllowSlaac bool // send RA packets without MO flags
raSlaacOnly bool // send RA packets with MO flags
ipAddr net.IP // source IP address (link-local-unicast)
dnsIPAddr net.IP // IP address for DNS Server option
prefixIPAddr net.IP // IP address for Prefix option
ifaceName string
iface *net.Interface
packetSendPeriod time.Duration // how often RA packets are sent
conn *icmp.PacketConn // ICMPv6 socket
stop atomic.Value // stop the packet sending loop
}
type icmpv6RA struct {
managedAddressConfiguration bool
otherConfiguration bool
prefix net.IP
prefixLen int
sourceLinkLayerAddress net.HardwareAddr
recursiveDNSServer net.IP
mtu uint32
}
// Create an ICMPv6.RouterAdvertisement packet with all necessary options.
//
// ICMPv6:
// type[1]
// code[1]
// chksum[2]
// body (RouterAdvertisement):
// Cur Hop Limit[1]
// Flags[1]: MO......
// Router Lifetime[2]
// Reachable Time[4]
// Retrans Timer[4]
// Option=Prefix Information(3):
// Type[1]
// Length * 8bytes[1]
// Prefix Length[1]
// Flags[1]: LA......
// Valid Lifetime[4]
// Preferred Lifetime[4]
// Reserved[4]
// Prefix[16]
// Option=MTU(5):
// Type[1]
// Length * 8bytes[1]
// Reserved[2]
// MTU[4]
// Option=Source link-layer address(1):
// Link-Layer Address[6]
// Option=Recursive DNS Server(25):
// Type[1]
// Length * 8bytes[1]
// Reserved[2]
// Lifetime[4]
// Addresses of IPv6 Recursive DNS Servers[16]
func createICMPv6RAPacket(params icmpv6RA) []byte {
data := make([]byte, 88)
i := 0
// ICMPv6:
data[i] = 134 // type
data[i+1] = 0 // code
data[i+2] = 0 // chksum
data[i+3] = 0
i += 4
// RouterAdvertisement:
data[i] = 64 // Cur Hop Limit[1]
i++
data[i] = 0 // Flags[1]: MO......
if params.managedAddressConfiguration {
data[i] |= 0x80
}
if params.otherConfiguration {
data[i] |= 0x40
}
i++
binary.BigEndian.PutUint16(data[i:], 1800) // Router Lifetime[2]
i += 2
binary.BigEndian.PutUint32(data[i:], 0) // Reachable Time[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 0) // Retrans Timer[4]
i += 4
// Option=Prefix Information:
data[i] = 3 // Type
data[i+1] = 4 // Length
i += 2
data[i] = byte(params.prefixLen) // Prefix Length[1]
i++
data[i] = 0xc0 // Flags[1]
i++
binary.BigEndian.PutUint32(data[i:], 3600) // Valid Lifetime[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 3600) // Preferred Lifetime[4]
i += 4
binary.BigEndian.PutUint32(data[i:], 0) // Reserved[4]
i += 4
copy(data[i:], params.prefix[:8]) // Prefix[16]
binary.BigEndian.PutUint32(data[i+8:], 0)
binary.BigEndian.PutUint32(data[i+12:], 0)
i += 16
// Option=MTU:
data[i] = 5 // Type
data[i+1] = 1 // Length
i += 2
binary.BigEndian.PutUint16(data[i:], 0) // Reserved[2]
i += 2
binary.BigEndian.PutUint32(data[i:], params.mtu) // MTU[4]
i += 4
// Option=Source link-layer address:
data[i] = 1 // Type
data[i+1] = 1 // Length
i += 2
copy(data[i:], params.sourceLinkLayerAddress) // Link-Layer Address[6]
i += 6
// Option=Recursive DNS Server:
data[i] = 25 // Type
data[i+1] = 3 // Length
i += 2
binary.BigEndian.PutUint16(data[i:], 0) // Reserved[2]
i += 2
binary.BigEndian.PutUint32(data[i:], 3600) // Lifetime[4]
i += 4
copy(data[i:], params.recursiveDNSServer) // Addresses of IPv6 Recursive DNS Servers[16]
return data
}
// Init - initialize RA module
func (ra *raCtx) Init() error {
ra.stop.Store(0)
ra.conn = nil
if !(ra.raAllowSlaac || ra.raSlaacOnly) {
return nil
}
log.Debug("DHCPv6 RA: source IP address: %s DNS IP address: %s",
ra.ipAddr, ra.dnsIPAddr)
params := icmpv6RA{
managedAddressConfiguration: !ra.raSlaacOnly,
otherConfiguration: !ra.raSlaacOnly,
mtu: uint32(ra.iface.MTU),
prefixLen: 64,
recursiveDNSServer: ra.dnsIPAddr,
sourceLinkLayerAddress: ra.iface.HardwareAddr,
}
params.prefix = make([]byte, 16)
copy(params.prefix, ra.prefixIPAddr[:8]) // /64
data := createICMPv6RAPacket(params)
var err error
ipAndScope := ra.ipAddr.String() + "%" + ra.ifaceName
ra.conn, err = icmp.ListenPacket("ip6:ipv6-icmp", ipAndScope)
if err != nil {
return fmt.Errorf("DHCPv6 RA: icmp.ListenPacket: %s", err)
}
success := false
defer func() {
if !success {
ra.Close()
}
}()
con6 := ra.conn.IPv6PacketConn()
if err := con6.SetHopLimit(255); err != nil {
return fmt.Errorf("DHCPv6 RA: SetHopLimit: %s", err)
}
if err := con6.SetMulticastHopLimit(255); err != nil {
return fmt.Errorf("DHCPv6 RA: SetMulticastHopLimit: %s", err)
}
msg := &ipv6.ControlMessage{
HopLimit: 255,
Src: ra.ipAddr,
IfIndex: ra.iface.Index,
}
addr := &net.UDPAddr{
IP: net.ParseIP("ff02::1"),
}
go func() {
log.Debug("DHCPv6 RA: starting to send periodic RouterAdvertisement packets")
for ra.stop.Load() == 0 {
_, err = con6.WriteTo(data, msg, addr)
if err != nil {
log.Error("DHCPv6 RA: WriteTo: %s", err)
}
time.Sleep(ra.packetSendPeriod)
}
log.Debug("DHCPv6 RA: loop exit")
}()
success = true
return nil
}
// Close - close module
func (ra *raCtx) Close() {
log.Debug("DHCPv6 RA: closing")
ra.stop.Store(1)
if ra.conn != nil {
ra.conn.Close()
}
}