Copy queries prior to packing them in resolvers (#290)

* Copy queries prior to packing them in resolvers

* Fix race in quic restart logic

* Remove bad lock

dnsclient.go

@@ -65,6 +65,9 @@ func NewDNSClient(id, endpoint, network string, opt DNSClientOptions) (*DNSClien
 
 // Resolve a DNS query.
 func (d *DNSClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+	// Packing a message is not always a read-only operation, make a copy
+	q = q.Copy()
+
 	logger(d.id, q, ci).WithFields(logrus.Fields{
 		"resolver": d.endpoint,
 		"protocol": d.net,

dohclient.go

@@ -101,6 +101,9 @@ func NewDoHClient(id, endpoint string, opt DoHClientOptions) (*DoHClient, error)
 
 // Resolve a DNS query.
 func (d *DoHClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+	// Packing a message is not always a read-only operation, make a copy
+	q = q.Copy()
+
 	logger(d.id, q, ci).WithFields(logrus.Fields{
 		"resolver": d.endpoint,
 		"protocol": "doh",

dotclient.go

@@ -71,6 +71,9 @@ func NewDoTClient(id, endpoint string, opt DoTClientOptions) (*DoTClient, error)
 
 // Resolve a DNS query.
 func (d *DoTClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+	// Packing a message is not always a read-only operation, make a copy
+	q = q.Copy()
+
 	logger(d.id, q, ci).WithFields(logrus.Fields{
 		"resolver": d.endpoint,
 		"protocol": "dot",

dtlsclient.go

@@ -93,6 +93,9 @@ func NewDTLSClient(id, endpoint string, opt DTLSClientOptions) (*DTLSClient, err
 
 // Resolve a DNS query.
 func (d *DTLSClient) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
+	// Packing a message is not always a read-only operation, make a copy
+	q = q.Copy()
+
 	logger(d.id, q, ci).WithFields(logrus.Fields{
 		"resolver": d.endpoint,
 		"protocol": "dtls",