AdGuardHome/internal/next/dnssvc/dnssvc.go

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// Package dnssvc contains the AdGuard Home DNS service.
//
// TODO(a.garipov): Define, if all methods of a *Service should work with a nil
// receiver.
package dnssvc
import (
"context"
"fmt"
"net"
"net/netip"
"sync/atomic"
"time"
"github.com/AdguardTeam/AdGuardHome/internal/next/agh"
// TODO(a.garipov): Add a “dnsproxy proxy” package to shield us from changes
// and replacement of module dnsproxy.
"github.com/AdguardTeam/dnsproxy/proxy"
"github.com/AdguardTeam/dnsproxy/upstream"
)
// Service is the AdGuard Home DNS service. A nil *Service is a valid
// [agh.Service] that does nothing.
//
// TODO(a.garipov): Consider saving a [*proxy.Config] instance for those
// fields that are only used in [New] and [Service.Config].
type Service struct {
proxy *proxy.Proxy
bootstraps []string
upstreams []string
dns64Prefixes []netip.Prefix
upsTimeout time.Duration
running atomic.Bool
bootstrapPreferIPv6 bool
useDNS64 bool
}
// New returns a new properly initialized *Service. If c is nil, svc is a nil
// *Service that does nothing. The fields of c must not be modified after
// calling New.
func New(c *Config) (svc *Service, err error) {
if c == nil {
return nil, nil
}
svc = &Service{
bootstraps: c.BootstrapServers,
upstreams: c.UpstreamServers,
dns64Prefixes: c.DNS64Prefixes,
upsTimeout: c.UpstreamTimeout,
bootstrapPreferIPv6: c.BootstrapPreferIPv6,
useDNS64: c.UseDNS64,
}
upstreams, err := addressesToUpstreams(
c.UpstreamServers,
c.BootstrapServers,
c.UpstreamTimeout,
c.BootstrapPreferIPv6,
)
if err != nil {
return nil, fmt.Errorf("converting upstreams: %w", err)
}
svc.proxy = &proxy.Proxy{
Config: proxy.Config{
UDPListenAddr: udpAddrs(c.Addresses),
TCPListenAddr: tcpAddrs(c.Addresses),
UpstreamConfig: &proxy.UpstreamConfig{
Upstreams: upstreams,
},
UseDNS64: c.UseDNS64,
DNS64Prefs: c.DNS64Prefixes,
},
}
err = svc.proxy.Init()
if err != nil {
return nil, fmt.Errorf("proxy: %w", err)
}
return svc, nil
}
// addressesToUpstreams is a wrapper around [upstream.AddressToUpstream]. It
// accepts a slice of addresses and other upstream parameters, and returns a
// slice of upstreams.
func addressesToUpstreams(
upsStrs []string,
bootstraps []string,
timeout time.Duration,
preferIPv6 bool,
) (upstreams []upstream.Upstream, err error) {
upstreams = make([]upstream.Upstream, len(upsStrs))
for i, upsStr := range upsStrs {
upstreams[i], err = upstream.AddressToUpstream(upsStr, &upstream.Options{
Bootstrap: bootstraps,
Timeout: timeout,
PreferIPv6: preferIPv6,
})
if err != nil {
return nil, fmt.Errorf("upstream at index %d: %w", i, err)
}
}
return upstreams, nil
}
// tcpAddrs converts []netip.AddrPort into []*net.TCPAddr.
func tcpAddrs(addrPorts []netip.AddrPort) (tcpAddrs []*net.TCPAddr) {
if addrPorts == nil {
return nil
}
tcpAddrs = make([]*net.TCPAddr, len(addrPorts))
for i, a := range addrPorts {
tcpAddrs[i] = net.TCPAddrFromAddrPort(a)
}
return tcpAddrs
}
// udpAddrs converts []netip.AddrPort into []*net.UDPAddr.
func udpAddrs(addrPorts []netip.AddrPort) (udpAddrs []*net.UDPAddr) {
if addrPorts == nil {
return nil
}
udpAddrs = make([]*net.UDPAddr, len(addrPorts))
for i, a := range addrPorts {
udpAddrs[i] = net.UDPAddrFromAddrPort(a)
}
return udpAddrs
}
// type check
var _ agh.Service = (*Service)(nil)
// Start implements the [agh.Service] interface for *Service. svc may be nil.
// After Start exits, all DNS servers have tried to start, but there is no
// guarantee that they did. Errors from the servers are written to the log.
func (svc *Service) Start() (err error) {
if svc == nil {
return nil
}
defer func() {
// TODO(a.garipov): [proxy.Proxy.Start] doesn't actually have any way to
// tell when all servers are actually up, so at best this is merely an
// assumption.
svc.running.Store(err == nil)
}()
return svc.proxy.Start()
}
// Shutdown implements the [agh.Service] interface for *Service. svc may be
// nil.
func (svc *Service) Shutdown(ctx context.Context) (err error) {
if svc == nil {
return nil
}
return svc.proxy.Stop()
}
// Config returns the current configuration of the web service. Config must not
// be called simultaneously with Start. If svc was initialized with ":0"
// addresses, addrs will not return the actual bound ports until Start is
// finished.
func (svc *Service) Config() (c *Config) {
// TODO(a.garipov): Do we need to get the TCP addresses separately?
var addrs []netip.AddrPort
if svc.running.Load() {
udpAddrs := svc.proxy.Addrs(proxy.ProtoUDP)
addrs = make([]netip.AddrPort, len(udpAddrs))
for i, a := range udpAddrs {
addrs[i] = a.(*net.UDPAddr).AddrPort()
}
} else {
conf := svc.proxy.Config
udpAddrs := conf.UDPListenAddr
addrs = make([]netip.AddrPort, len(udpAddrs))
for i, a := range udpAddrs {
addrs[i] = a.AddrPort()
}
}
c = &Config{
Addresses: addrs,
BootstrapServers: svc.bootstraps,
UpstreamServers: svc.upstreams,
DNS64Prefixes: svc.dns64Prefixes,
UpstreamTimeout: svc.upsTimeout,
BootstrapPreferIPv6: svc.bootstrapPreferIPv6,
UseDNS64: svc.useDNS64,
}
return c
}