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libnetwork: forward unknown PTR queries externally

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PTR queries with domain names unknown to us are not necessarily invalid.
Act like a well-behaved middlebox and fall back to forwarding
externally, same as we do with the other query types.

Signed-off-by: Cory Snider <csnider@mirantis.com>
This commit is contained in:
Cory Snider 2023-01-06 20:11:15 -05:00
parent 8f5a9a741b
commit faaa4fdf18
1 changed files with 13 additions and 16 deletions
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29
libnetwork/resolver.go
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@ -293,26 +293,23 @@ func (r *resolver) handleIPQuery(query *dns.Msg, ipType int) (*dns.Msg, error) {
}
func (r *resolver) handlePTRQuery(query *dns.Msg) (*dns.Msg, error) {
var (
parts []string
ptr = query.Question[0].Name
)
if strings.HasSuffix(ptr, ptrIPv4domain) {
parts = strings.Split(ptr, ptrIPv4domain)
} else if strings.HasSuffix(ptr, ptrIPv6domain) {
parts = strings.Split(ptr, ptrIPv6domain)
} else {
return nil, fmt.Errorf("invalid PTR query, %v", ptr)
ptr := query.Question[0].Name
name, after, found := strings.Cut(ptr, ptrIPv4domain)
if !found || after != "" {
name, after, found = strings.Cut(ptr, ptrIPv6domain)
}
host := r.backend.ResolveIP(parts[0])
if len(host) == 0 {
if !found || after != "" {
// Not a known IPv4 or IPv6 PTR domain.
// Maybe the external DNS servers know what to do with the query?
return nil, nil
}
logrus.Debugf("[resolver] lookup for IP %s: name %s", parts[0], host)
host := r.backend.ResolveIP(name)
if host == "" {
return nil, nil
}
logrus.Debugf("[resolver] lookup for IP %s: name %s", name, host)
fqdn := dns.Fqdn(host)
resp := new(dns.Msg)