Path MTU discovery fixes and improvements (#3109)

- Existing option `WIREGUARD_MTU` , if set, disables PMTUD and is used
- New option `PMTUD_ICMP_ADDRESSES=1.1.1.1,8.8.8.8` and `PMTUD_TCP_ADDRESSES=1.1.1.1:443,8.8.8.8:443`
- ICMP PMTUD now targets external-by-default IP addresses
- New TCP PMTUD (binary search only) as a second MTU confirmation and fallback mechanism.
- Force set TCP MSS to MTU - IP header - TCP base header - "magic 20 bytes" 🎆
- Fix #3108

internal/pmtud/tcp/mocks_test.go

@@ -0,0 +1,80 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/pmtud/tcp (interfaces: Logger)
+
+// Package tcp is a generated GoMock package.
+package tcp
+
+import (
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+)
+
+// MockLogger is a mock of Logger interface.
+type MockLogger struct {
+	ctrl     *gomock.Controller
+	recorder *MockLoggerMockRecorder
+}
+
+// MockLoggerMockRecorder is the mock recorder for MockLogger.
+type MockLoggerMockRecorder struct {
+	mock *MockLogger
+}
+
+// NewMockLogger creates a new mock instance.
+func NewMockLogger(ctrl *gomock.Controller) *MockLogger {
+	mock := &MockLogger{ctrl: ctrl}
+	mock.recorder = &MockLoggerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockLogger) EXPECT() *MockLoggerMockRecorder {
+	return m.recorder
+}
+
+// Debug mocks base method.
+func (m *MockLogger) Debug(arg0 string) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Debug", arg0)
+}
+
+// Debug indicates an expected call of Debug.
+func (mr *MockLoggerMockRecorder) Debug(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debug", reflect.TypeOf((*MockLogger)(nil).Debug), arg0)
+}
+
+// Debugf mocks base method.
+func (m *MockLogger) Debugf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Debugf", varargs...)
+}
+
+// Debugf indicates an expected call of Debugf.
+func (mr *MockLoggerMockRecorder) Debugf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Debugf", reflect.TypeOf((*MockLogger)(nil).Debugf), varargs...)
+}
+
+// Warnf mocks base method.
+func (m *MockLogger) Warnf(arg0 string, arg1 ...interface{}) {
+	m.ctrl.T.Helper()
+	varargs := []interface{}{arg0}
+	for _, a := range arg1 {
+		varargs = append(varargs, a)
+	}
+	m.ctrl.Call(m, "Warnf", varargs...)
+}
+
+// Warnf indicates an expected call of Warnf.
+func (mr *MockLoggerMockRecorder) Warnf(arg0 interface{}, arg1 ...interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]interface{}{arg0}, arg1...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Warnf", reflect.TypeOf((*MockLogger)(nil).Warnf), varargs...)
+}