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router_dns.go
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router_dns.go
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package route
import (
"context"
"errors"
"net/netip"
"strings"
"time"
"github.com/sagernet/sing-box/adapter"
"github.com/sagernet/sing-dns"
"github.com/sagernet/sing/common/cache"
E "github.com/sagernet/sing/common/exceptions"
F "github.com/sagernet/sing/common/format"
M "github.com/sagernet/sing/common/metadata"
mDNS "github.com/miekg/dns"
)
type DNSReverseMapping struct {
cache *cache.LruCache[netip.Addr, string]
}
func NewDNSReverseMapping() *DNSReverseMapping {
return &DNSReverseMapping{
cache: cache.New[netip.Addr, string](),
}
}
func (m *DNSReverseMapping) Save(address netip.Addr, domain string, ttl int) {
m.cache.StoreWithExpire(address, domain, time.Now().Add(time.Duration(ttl)*time.Second))
}
func (m *DNSReverseMapping) Query(address netip.Addr) (string, bool) {
domain, loaded := m.cache.Load(address)
return domain, loaded
}
func (r *Router) matchDNS(ctx context.Context, allowFakeIP bool, index int, isAddressQuery bool) (context.Context, dns.Transport, dns.DomainStrategy, adapter.DNSRule, int) {
metadata := adapter.ContextFrom(ctx)
if metadata == nil {
panic("no context")
}
if index < len(r.dnsRules) {
dnsRules := r.dnsRules
if index != -1 {
dnsRules = dnsRules[index+1:]
}
for currentRuleIndex, rule := range dnsRules {
if rule.WithAddressLimit() && !isAddressQuery {
continue
}
metadata.ResetRuleCache()
if rule.Match(metadata) {
detour := rule.Outbound()
transport, loaded := r.transportMap[detour]
if !loaded {
r.dnsLogger.ErrorContext(ctx, "transport not found: ", detour)
continue
}
_, isFakeIP := transport.(adapter.FakeIPTransport)
if isFakeIP && !allowFakeIP {
continue
}
ruleIndex := currentRuleIndex
if index != -1 {
ruleIndex += index + 1
}
r.dnsLogger.DebugContext(ctx, "match[", ruleIndex, "] ", rule.String(), " => ", detour)
if isFakeIP || rule.DisableCache() {
ctx = dns.ContextWithDisableCache(ctx, true)
}
if rewriteTTL := rule.RewriteTTL(); rewriteTTL != nil {
ctx = dns.ContextWithRewriteTTL(ctx, *rewriteTTL)
}
if clientSubnet := rule.ClientSubnet(); clientSubnet != nil {
ctx = dns.ContextWithClientSubnet(ctx, *clientSubnet)
}
if domainStrategy, dsLoaded := r.transportDomainStrategy[transport]; dsLoaded {
return ctx, transport, domainStrategy, rule, ruleIndex
} else {
return ctx, transport, r.defaultDomainStrategy, rule, ruleIndex
}
}
}
}
if domainStrategy, dsLoaded := r.transportDomainStrategy[r.defaultTransport]; dsLoaded {
return ctx, r.defaultTransport, domainStrategy, nil, -1
} else {
return ctx, r.defaultTransport, r.defaultDomainStrategy, nil, -1
}
}
func (r *Router) Exchange(ctx context.Context, message *mDNS.Msg) (*mDNS.Msg, error) {
if len(message.Question) > 0 {
r.dnsLogger.DebugContext(ctx, "exchange ", formatQuestion(message.Question[0].String()))
}
var (
response *mDNS.Msg
cached bool
transport dns.Transport
err error
)
response, cached = r.dnsClient.ExchangeCache(ctx, message)
if !cached {
var metadata *adapter.InboundContext
ctx, metadata = adapter.ExtendContext(ctx)
metadata.Destination = M.Socksaddr{}
if len(message.Question) > 0 {
metadata.QueryType = message.Question[0].Qtype
switch metadata.QueryType {
case mDNS.TypeA:
metadata.IPVersion = 4
case mDNS.TypeAAAA:
metadata.IPVersion = 6
}
metadata.Domain = fqdnToDomain(message.Question[0].Name)
}
var (
strategy dns.DomainStrategy
rule adapter.DNSRule
ruleIndex int
)
ruleIndex = -1
for {
var (
dnsCtx context.Context
addressLimit bool
)
dnsCtx, transport, strategy, rule, ruleIndex = r.matchDNS(ctx, true, ruleIndex, isAddressQuery(message))
dnsCtx = adapter.OverrideContext(dnsCtx)
if rule != nil && rule.WithAddressLimit() {
addressLimit = true
response, err = r.dnsClient.ExchangeWithResponseCheck(dnsCtx, transport, message, strategy, func(response *mDNS.Msg) bool {
addresses, addrErr := dns.MessageToAddresses(response)
if addrErr != nil {
return false
}
metadata.DestinationAddresses = addresses
return rule.MatchAddressLimit(metadata)
})
} else {
addressLimit = false
response, err = r.dnsClient.Exchange(dnsCtx, transport, message, strategy)
}
var rejected bool
if err != nil {
if errors.Is(err, dns.ErrResponseRejectedCached) {
rejected = true
r.dnsLogger.DebugContext(ctx, E.Cause(err, "response rejected for ", formatQuestion(message.Question[0].String())), " (cached)")
} else if errors.Is(err, dns.ErrResponseRejected) {
rejected = true
r.dnsLogger.DebugContext(ctx, E.Cause(err, "response rejected for ", formatQuestion(message.Question[0].String())))
} else if len(message.Question) > 0 {
r.dnsLogger.ErrorContext(ctx, E.Cause(err, "exchange failed for ", formatQuestion(message.Question[0].String())))
} else {
r.dnsLogger.ErrorContext(ctx, E.Cause(err, "exchange failed for <empty query>"))
}
}
if addressLimit && rejected {
continue
}
break
}
}
if err != nil {
return nil, err
}
if r.dnsReverseMapping != nil && len(message.Question) > 0 && response != nil && len(response.Answer) > 0 {
if _, isFakeIP := transport.(adapter.FakeIPTransport); !isFakeIP {
for _, answer := range response.Answer {
switch record := answer.(type) {
case *mDNS.A:
r.dnsReverseMapping.Save(M.AddrFromIP(record.A), fqdnToDomain(record.Hdr.Name), int(record.Hdr.Ttl))
case *mDNS.AAAA:
r.dnsReverseMapping.Save(M.AddrFromIP(record.AAAA), fqdnToDomain(record.Hdr.Name), int(record.Hdr.Ttl))
}
}
}
}
return response, nil
}
func (r *Router) Lookup(ctx context.Context, domain string, strategy dns.DomainStrategy) ([]netip.Addr, error) {
var (
responseAddrs []netip.Addr
cached bool
err error
)
responseAddrs, cached = r.dnsClient.LookupCache(ctx, domain, strategy)
if cached {
if len(responseAddrs) == 0 {
return nil, dns.RCodeNameError
}
return responseAddrs, nil
}
r.dnsLogger.DebugContext(ctx, "lookup domain ", domain)
ctx, metadata := adapter.ExtendContext(ctx)
metadata.Destination = M.Socksaddr{}
metadata.Domain = domain
var (
transport dns.Transport
transportStrategy dns.DomainStrategy
rule adapter.DNSRule
ruleIndex int
)
ruleIndex = -1
for {
var (
dnsCtx context.Context
addressLimit bool
)
dnsCtx, transport, transportStrategy, rule, ruleIndex = r.matchDNS(ctx, false, ruleIndex, true)
dnsCtx = adapter.OverrideContext(dnsCtx)
if strategy == dns.DomainStrategyAsIS {
strategy = transportStrategy
}
if rule != nil && rule.WithAddressLimit() {
addressLimit = true
responseAddrs, err = r.dnsClient.LookupWithResponseCheck(dnsCtx, transport, domain, strategy, func(responseAddrs []netip.Addr) bool {
metadata.DestinationAddresses = responseAddrs
return rule.MatchAddressLimit(metadata)
})
} else {
addressLimit = false
responseAddrs, err = r.dnsClient.Lookup(dnsCtx, transport, domain, strategy)
}
if err != nil {
if errors.Is(err, dns.ErrResponseRejectedCached) {
r.dnsLogger.DebugContext(ctx, "response rejected for ", domain, " (cached)")
} else if errors.Is(err, dns.ErrResponseRejected) {
r.dnsLogger.DebugContext(ctx, "response rejected for ", domain)
} else {
r.dnsLogger.ErrorContext(ctx, E.Cause(err, "lookup failed for ", domain))
}
} else if len(responseAddrs) == 0 {
r.dnsLogger.ErrorContext(ctx, "lookup failed for ", domain, ": empty result")
err = dns.RCodeNameError
}
if !addressLimit || err == nil {
break
}
}
if len(responseAddrs) > 0 {
r.dnsLogger.InfoContext(ctx, "lookup succeed for ", domain, ": ", strings.Join(F.MapToString(responseAddrs), " "))
}
return responseAddrs, err
}
func (r *Router) LookupDefault(ctx context.Context, domain string) ([]netip.Addr, error) {
return r.Lookup(ctx, domain, dns.DomainStrategyAsIS)
}
func (r *Router) ClearDNSCache() {
r.dnsClient.ClearCache()
if r.platformInterface != nil {
r.platformInterface.ClearDNSCache()
}
}
func isAddressQuery(message *mDNS.Msg) bool {
for _, question := range message.Question {
if question.Qtype == mDNS.TypeA || question.Qtype == mDNS.TypeAAAA || question.Qtype == mDNS.TypeHTTPS {
return true
}
}
return false
}
func fqdnToDomain(fqdn string) string {
if mDNS.IsFqdn(fqdn) {
return fqdn[:len(fqdn)-1]
}
return fqdn
}
func formatQuestion(string string) string {
if strings.HasPrefix(string, ";") {
string = string[1:]
}
string = strings.ReplaceAll(string, "\t", " ")
for strings.Contains(string, " ") {
string = strings.ReplaceAll(string, " ", " ")
}
return string
}