pages-server/server/dns/dns.go
Moritz Marquardt 18d09a163c Use hashicorp's LRU cache for DNS & certificates
DNS caching is also limited to 30 seconds now instead of 5 minutes
2024-04-18 19:07:34 +02:00

77 lines
2 KiB
Go

package dns
import (
"github.com/hashicorp/golang-lru/v2"
"net"
"strings"
"time"
)
type lookupCacheEntry struct {
cachedName string
timestamp time.Time
}
var lookupCacheValidity = 30 * time.Second
var lookupCache *lru.Cache[string, lookupCacheEntry]
var defaultPagesRepo = "pages"
// GetTargetFromDNS searches for CNAME or TXT entries on the request domain ending with MainDomainSuffix.
// If everything is fine, it returns the target data.
func GetTargetFromDNS(domain, mainDomainSuffix, firstDefaultBranch string) (targetOwner, targetRepo, targetBranch string) {
// Get CNAME or TXT
var cname string
var err error
if lookupCache == nil {
lookupCache, err = lru.New[string, lookupCacheEntry](4096)
if err != nil {
panic(err) // This should only happen if 4096 < 0 at the time of writing, which should be reason enough to panic.
}
}
if entry, ok := lookupCache.Get(domain); ok && time.Now().Before(entry.timestamp.Add(lookupCacheValidity)) {
cname = entry.cachedName
} else {
cname, err = net.LookupCNAME(domain)
cname = strings.TrimSuffix(cname, ".")
if err != nil || !strings.HasSuffix(cname, mainDomainSuffix) {
cname = ""
// TODO: check if the A record matches!
names, err := net.LookupTXT(domain)
if err == nil {
for _, name := range names {
name = strings.TrimSuffix(strings.TrimSpace(name), ".")
if strings.HasSuffix(name, mainDomainSuffix) {
cname = name
break
}
}
}
}
_ = lookupCache.Add(domain, lookupCacheEntry{
cname,
time.Now(),
})
}
if cname == "" {
return
}
cnameParts := strings.Split(strings.TrimSuffix(cname, mainDomainSuffix), ".")
targetOwner = cnameParts[len(cnameParts)-1]
if len(cnameParts) > 1 {
targetRepo = cnameParts[len(cnameParts)-2]
}
if len(cnameParts) > 2 {
targetBranch = cnameParts[len(cnameParts)-3]
}
if targetRepo == "" {
targetRepo = defaultPagesRepo
}
if targetBranch == "" && targetRepo != defaultPagesRepo {
targetBranch = firstDefaultBranch
}
// if targetBranch is still empty, the caller must find the default branch
return
}