124 lines
2.8 KiB
Go
124 lines
2.8 KiB
Go
package requestdecorator
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
"net"
|
|
"sort"
|
|
"strings"
|
|
"time"
|
|
|
|
"github.com/miekg/dns"
|
|
"github.com/patrickmn/go-cache"
|
|
"github.com/traefik/traefik/v2/pkg/log"
|
|
)
|
|
|
|
type cnameResolv struct {
|
|
TTL time.Duration
|
|
Record string
|
|
}
|
|
|
|
type byTTL []*cnameResolv
|
|
|
|
func (a byTTL) Len() int { return len(a) }
|
|
func (a byTTL) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
|
|
func (a byTTL) Less(i, j int) bool { return a[i].TTL > a[j].TTL }
|
|
|
|
// Resolver used for host resolver.
|
|
type Resolver struct {
|
|
CnameFlattening bool
|
|
ResolvConfig string
|
|
ResolvDepth int
|
|
cache *cache.Cache
|
|
}
|
|
|
|
// CNAMEFlatten check if CNAME record exists, flatten if possible.
|
|
func (hr *Resolver) CNAMEFlatten(ctx context.Context, host string) string {
|
|
if hr.cache == nil {
|
|
hr.cache = cache.New(30*time.Minute, 5*time.Minute)
|
|
}
|
|
|
|
result := host
|
|
request := host
|
|
|
|
value, found := hr.cache.Get(host)
|
|
if found {
|
|
return value.(string)
|
|
}
|
|
|
|
logger := log.FromContext(ctx)
|
|
cacheDuration := 0 * time.Second
|
|
for depth := 0; depth < hr.ResolvDepth; depth++ {
|
|
resolv, err := cnameResolve(ctx, request, hr.ResolvConfig)
|
|
if err != nil {
|
|
logger.Error(err)
|
|
break
|
|
}
|
|
if resolv == nil {
|
|
break
|
|
}
|
|
|
|
result = resolv.Record
|
|
if depth == 0 {
|
|
cacheDuration = resolv.TTL
|
|
}
|
|
request = resolv.Record
|
|
}
|
|
|
|
if err := hr.cache.Add(host, result, cacheDuration); err != nil {
|
|
logger.Error(err)
|
|
}
|
|
|
|
return result
|
|
}
|
|
|
|
// cnameResolve resolves CNAME if exists, and return with the highest TTL.
|
|
func cnameResolve(ctx context.Context, host, resolvPath string) (*cnameResolv, error) {
|
|
config, err := dns.ClientConfigFromFile(resolvPath)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("invalid resolver configuration file: %s", resolvPath)
|
|
}
|
|
|
|
client := &dns.Client{Timeout: 30 * time.Second}
|
|
|
|
m := &dns.Msg{}
|
|
m.SetQuestion(dns.Fqdn(host), dns.TypeCNAME)
|
|
|
|
var result []*cnameResolv
|
|
for _, server := range config.Servers {
|
|
tempRecord, err := getRecord(client, m, server, config.Port)
|
|
if err != nil {
|
|
log.FromContext(ctx).Errorf("Failed to resolve host %s: %v", host, err)
|
|
continue
|
|
}
|
|
result = append(result, tempRecord)
|
|
}
|
|
|
|
if len(result) == 0 {
|
|
return nil, nil
|
|
}
|
|
|
|
sort.Sort(byTTL(result))
|
|
return result[0], nil
|
|
}
|
|
|
|
func getRecord(client *dns.Client, msg *dns.Msg, server, port string) (*cnameResolv, error) {
|
|
resp, _, err := client.Exchange(msg, net.JoinHostPort(server, port))
|
|
if err != nil {
|
|
return nil, fmt.Errorf("exchange error for server %s: %w", server, err)
|
|
}
|
|
|
|
if resp == nil || len(resp.Answer) == 0 {
|
|
return nil, fmt.Errorf("empty answer for server %s", server)
|
|
}
|
|
|
|
rr, ok := resp.Answer[0].(*dns.CNAME)
|
|
if !ok {
|
|
return nil, fmt.Errorf("invalid response type for server %s", server)
|
|
}
|
|
|
|
return &cnameResolv{
|
|
TTL: time.Duration(rr.Hdr.Ttl) * time.Second,
|
|
Record: strings.TrimSuffix(rr.Target, "."),
|
|
}, nil
|
|
}
|