/
plugin_get_set_payload_size.go
66 lines (58 loc) · 1.75 KB
/
plugin_get_set_payload_size.go
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package main
import "github.com/miekg/dns"
type PluginGetSetPayloadSize struct{}
func (plugin *PluginGetSetPayloadSize) Name() string {
return "get_set_payload_size"
}
func (plugin *PluginGetSetPayloadSize) Description() string {
return "Adjusts the maximum payload size advertised in queries sent to upstream servers."
}
func (plugin *PluginGetSetPayloadSize) Init(proxy *Proxy) error {
return nil
}
func (plugin *PluginGetSetPayloadSize) Drop() error {
return nil
}
func (plugin *PluginGetSetPayloadSize) Reload() error {
return nil
}
func (plugin *PluginGetSetPayloadSize) Eval(pluginsState *PluginsState, msg *dns.Msg) error {
pluginsState.originalMaxPayloadSize = 512 - ResponseOverhead
edns0 := msg.IsEdns0()
dnssec := false
if edns0 != nil {
pluginsState.maxUnencryptedUDPSafePayloadSize = int(edns0.UDPSize())
pluginsState.originalMaxPayloadSize = Max(
pluginsState.maxUnencryptedUDPSafePayloadSize-ResponseOverhead,
pluginsState.originalMaxPayloadSize,
)
dnssec = edns0.Do()
}
var options *[]dns.EDNS0
pluginsState.dnssec = dnssec
pluginsState.maxPayloadSize = Min(
MaxDNSUDPPacketSize-ResponseOverhead,
Max(pluginsState.originalMaxPayloadSize, pluginsState.maxPayloadSize),
)
if pluginsState.maxPayloadSize > 512 {
extra2 := []dns.RR{}
for _, extra := range msg.Extra {
if extra.Header().Rrtype != dns.TypeOPT {
extra2 = append(extra2, extra)
} else if xoptions := &extra.(*dns.OPT).Option; len(*xoptions) > 0 && options == nil {
options = xoptions
}
}
msg.Extra = extra2
msg.SetEdns0(uint16(pluginsState.maxPayloadSize), dnssec)
if options != nil {
for _, extra := range msg.Extra {
if extra.Header().Rrtype == dns.TypeOPT {
extra.(*dns.OPT).Option = *options
break
}
}
}
}
return nil
}