// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package tcpip

import (
	"math"
	"sync/atomic"

	"gvisor.dev/gvisor/pkg/sync"
)

// PacketOverheadFactor is used to multiply the value provided by the user on a
// SetSockOpt for setting the send/receive buffer sizes sockets.
const PacketOverheadFactor = 2

// SocketOptionsHandler holds methods that help define endpoint specific
// behavior for socket level socket options. These must be implemented by
// endpoints to get notified when socket level options are set.
type SocketOptionsHandler interface {
	// OnReuseAddressSet is invoked when SO_REUSEADDR is set for an endpoint.
	OnReuseAddressSet(v bool)

	// OnReusePortSet is invoked when SO_REUSEPORT is set for an endpoint.
	OnReusePortSet(v bool)

	// OnKeepAliveSet is invoked when SO_KEEPALIVE is set for an endpoint.
	OnKeepAliveSet(v bool)

	// OnDelayOptionSet is invoked when TCP_NODELAY is set for an endpoint.
	// Note that v will be the inverse of TCP_NODELAY option.
	OnDelayOptionSet(v bool)

	// OnCorkOptionSet is invoked when TCP_CORK is set for an endpoint.
	OnCorkOptionSet(v bool)

	// LastError is invoked when SO_ERROR is read for an endpoint.
	LastError() *Error

	// UpdateLastError updates the endpoint specific last error field.
	UpdateLastError(err *Error)

	// HasNIC is invoked to check if the NIC is valid for SO_BINDTODEVICE.
	HasNIC(v int32) bool

	// GetSendBufferSize is invoked to get the SO_SNDBUFSIZE.
	GetSendBufferSize() (int64, *Error)

	// IsUnixSocket is invoked to check if the socket is of unix domain.
	IsUnixSocket() bool
}

// DefaultSocketOptionsHandler is an embeddable type that implements no-op
// implementations for SocketOptionsHandler methods.
type DefaultSocketOptionsHandler struct{}

var _ SocketOptionsHandler = (*DefaultSocketOptionsHandler)(nil)

// OnReuseAddressSet implements SocketOptionsHandler.OnReuseAddressSet.
func (*DefaultSocketOptionsHandler) OnReuseAddressSet(bool) {}

// OnReusePortSet implements SocketOptionsHandler.OnReusePortSet.
func (*DefaultSocketOptionsHandler) OnReusePortSet(bool) {}

// OnKeepAliveSet implements SocketOptionsHandler.OnKeepAliveSet.
func (*DefaultSocketOptionsHandler) OnKeepAliveSet(bool) {}

// OnDelayOptionSet implements SocketOptionsHandler.OnDelayOptionSet.
func (*DefaultSocketOptionsHandler) OnDelayOptionSet(bool) {}

// OnCorkOptionSet implements SocketOptionsHandler.OnCorkOptionSet.
func (*DefaultSocketOptionsHandler) OnCorkOptionSet(bool) {}

// LastError implements SocketOptionsHandler.LastError.
func (*DefaultSocketOptionsHandler) LastError() *Error {
	return nil
}

// UpdateLastError implements SocketOptionsHandler.UpdateLastError.
func (*DefaultSocketOptionsHandler) UpdateLastError(*Error) {}

// HasNIC implements SocketOptionsHandler.HasNIC.
func (*DefaultSocketOptionsHandler) HasNIC(int32) bool {
	return false
}

// GetSendBufferSize implements SocketOptionsHandler.GetSendBufferSize.
func (*DefaultSocketOptionsHandler) GetSendBufferSize() (int64, *Error) {
	return 0, nil
}

// IsUnixSocket implements SocketOptionsHandler.IsUnixSocket.
func (*DefaultSocketOptionsHandler) IsUnixSocket() bool {
	return false
}

// StackHandler holds methods to access the stack options. These must be
// implemented by the stack.
type StackHandler interface {
	// Option allows retrieving stack wide options.
	Option(option interface{}) *Error

	// TransportProtocolOption allows retrieving individual protocol level
	// option values.
	TransportProtocolOption(proto TransportProtocolNumber, option GettableTransportProtocolOption) *Error
}

// SocketOptions contains all the variables which store values for SOL_SOCKET,
// SOL_IP, SOL_IPV6 and SOL_TCP level options.
//
// +stateify savable
type SocketOptions struct {
	handler SocketOptionsHandler

	// StackHandler is initialized at the creation time and will not change.
	stackHandler StackHandler `state:"manual"`

	// These fields are accessed and modified using atomic operations.

	// broadcastEnabled determines whether datagram sockets are allowed to
	// send packets to a broadcast address.
	broadcastEnabled uint32

	// passCredEnabled determines whether SCM_CREDENTIALS socket control
	// messages are enabled.
	passCredEnabled uint32

	// noChecksumEnabled determines whether UDP checksum is disabled while
	// transmitting for this socket.
	noChecksumEnabled uint32

	// reuseAddressEnabled determines whether Bind() should allow reuse of
	// local address.
	reuseAddressEnabled uint32

	// reusePortEnabled determines whether to permit multiple sockets to be
	// bound to an identical socket address.
	reusePortEnabled uint32

	// keepAliveEnabled determines whether TCP keepalive is enabled for this
	// socket.
	keepAliveEnabled uint32

	// multicastLoopEnabled determines whether multicast packets sent over a
	// non-loopback interface will be looped back.
	multicastLoopEnabled uint32

	// receiveTOSEnabled is used to specify if the TOS ancillary message is
	// passed with incoming packets.
	receiveTOSEnabled uint32

	// receiveTClassEnabled is used to specify if the IPV6_TCLASS ancillary
	// message is passed with incoming packets.
	receiveTClassEnabled uint32

	// receivePacketInfoEnabled is used to specify if more inforamtion is
	// provided with incoming packets such as interface index and address.
	receivePacketInfoEnabled uint32

	// hdrIncludeEnabled is used to indicate for a raw endpoint that all packets
	// being written have an IP header and the endpoint should not attach an IP
	// header.
	hdrIncludedEnabled uint32

	// v6OnlyEnabled is used to determine whether an IPv6 socket is to be
	// restricted to sending and receiving IPv6 packets only.
	v6OnlyEnabled uint32

	// quickAckEnabled is used to represent the value of TCP_QUICKACK option.
	// It currently does not have any effect on the TCP endpoint.
	quickAckEnabled uint32

	// delayOptionEnabled is used to specify if data should be sent out immediately
	// by the transport protocol. For TCP, it determines if the Nagle algorithm
	// is on or off.
	delayOptionEnabled uint32

	// corkOptionEnabled is used to specify if data should be held until segments
	// are full by the TCP transport protocol.
	corkOptionEnabled uint32

	// receiveOriginalDstAddress is used to specify if the original destination of
	// the incoming packet should be returned as an ancillary message.
	receiveOriginalDstAddress uint32

	// recvErrEnabled determines whether extended reliable error message passing
	// is enabled.
	recvErrEnabled uint32

	// errQueue is the per-socket error queue. It is protected by errQueueMu.
	errQueueMu sync.Mutex `state:"nosave"`
	errQueue   sockErrorList

	// bindToDevice determines the device to which the socket is bound.
	bindToDevice int32

	// sendBufferSize determines the send buffer size for this socket.
	sendBufferSize int64

	// mu protects the access to the below fields.
	mu sync.Mutex `state:"nosave"`

	// linger determines the amount of time the socket should linger before
	// close. We currently implement this option for TCP socket only.
	linger LingerOption
}

// InitHandler initializes the handler. This must be called before using the
// socket options utility.
func (so *SocketOptions) InitHandler(handler SocketOptionsHandler, stack StackHandler) {
	so.handler = handler
	so.stackHandler = stack
}

func storeAtomicBool(addr *uint32, v bool) {
	var val uint32
	if v {
		val = 1
	}
	atomic.StoreUint32(addr, val)
}

// SetLastError sets the last error for a socket.
func (so *SocketOptions) SetLastError(err *Error) {
	so.handler.UpdateLastError(err)
}

// GetBroadcast gets value for SO_BROADCAST option.
func (so *SocketOptions) GetBroadcast() bool {
	return atomic.LoadUint32(&so.broadcastEnabled) != 0
}

// SetBroadcast sets value for SO_BROADCAST option.
func (so *SocketOptions) SetBroadcast(v bool) {
	storeAtomicBool(&so.broadcastEnabled, v)
}

// GetPassCred gets value for SO_PASSCRED option.
func (so *SocketOptions) GetPassCred() bool {
	return atomic.LoadUint32(&so.passCredEnabled) != 0
}

// SetPassCred sets value for SO_PASSCRED option.
func (so *SocketOptions) SetPassCred(v bool) {
	storeAtomicBool(&so.passCredEnabled, v)
}

// GetNoChecksum gets value for SO_NO_CHECK option.
func (so *SocketOptions) GetNoChecksum() bool {
	return atomic.LoadUint32(&so.noChecksumEnabled) != 0
}

// SetNoChecksum sets value for SO_NO_CHECK option.
func (so *SocketOptions) SetNoChecksum(v bool) {
	storeAtomicBool(&so.noChecksumEnabled, v)
}

// GetReuseAddress gets value for SO_REUSEADDR option.
func (so *SocketOptions) GetReuseAddress() bool {
	return atomic.LoadUint32(&so.reuseAddressEnabled) != 0
}

// SetReuseAddress sets value for SO_REUSEADDR option.
func (so *SocketOptions) SetReuseAddress(v bool) {
	storeAtomicBool(&so.reuseAddressEnabled, v)
	so.handler.OnReuseAddressSet(v)
}

// GetReusePort gets value for SO_REUSEPORT option.
func (so *SocketOptions) GetReusePort() bool {
	return atomic.LoadUint32(&so.reusePortEnabled) != 0
}

// SetReusePort sets value for SO_REUSEPORT option.
func (so *SocketOptions) SetReusePort(v bool) {
	storeAtomicBool(&so.reusePortEnabled, v)
	so.handler.OnReusePortSet(v)
}

// GetKeepAlive gets value for SO_KEEPALIVE option.
func (so *SocketOptions) GetKeepAlive() bool {
	return atomic.LoadUint32(&so.keepAliveEnabled) != 0
}

// SetKeepAlive sets value for SO_KEEPALIVE option.
func (so *SocketOptions) SetKeepAlive(v bool) {
	storeAtomicBool(&so.keepAliveEnabled, v)
	so.handler.OnKeepAliveSet(v)
}

// GetMulticastLoop gets value for IP_MULTICAST_LOOP option.
func (so *SocketOptions) GetMulticastLoop() bool {
	return atomic.LoadUint32(&so.multicastLoopEnabled) != 0
}

// SetMulticastLoop sets value for IP_MULTICAST_LOOP option.
func (so *SocketOptions) SetMulticastLoop(v bool) {
	storeAtomicBool(&so.multicastLoopEnabled, v)
}

// GetReceiveTOS gets value for IP_RECVTOS option.
func (so *SocketOptions) GetReceiveTOS() bool {
	return atomic.LoadUint32(&so.receiveTOSEnabled) != 0
}

// SetReceiveTOS sets value for IP_RECVTOS option.
func (so *SocketOptions) SetReceiveTOS(v bool) {
	storeAtomicBool(&so.receiveTOSEnabled, v)
}

// GetReceiveTClass gets value for IPV6_RECVTCLASS option.
func (so *SocketOptions) GetReceiveTClass() bool {
	return atomic.LoadUint32(&so.receiveTClassEnabled) != 0
}

// SetReceiveTClass sets value for IPV6_RECVTCLASS option.
func (so *SocketOptions) SetReceiveTClass(v bool) {
	storeAtomicBool(&so.receiveTClassEnabled, v)
}

// GetReceivePacketInfo gets value for IP_PKTINFO option.
func (so *SocketOptions) GetReceivePacketInfo() bool {
	return atomic.LoadUint32(&so.receivePacketInfoEnabled) != 0
}

// SetReceivePacketInfo sets value for IP_PKTINFO option.
func (so *SocketOptions) SetReceivePacketInfo(v bool) {
	storeAtomicBool(&so.receivePacketInfoEnabled, v)
}

// GetHeaderIncluded gets value for IP_HDRINCL option.
func (so *SocketOptions) GetHeaderIncluded() bool {
	return atomic.LoadUint32(&so.hdrIncludedEnabled) != 0
}

// SetHeaderIncluded sets value for IP_HDRINCL option.
func (so *SocketOptions) SetHeaderIncluded(v bool) {
	storeAtomicBool(&so.hdrIncludedEnabled, v)
}

// GetV6Only gets value for IPV6_V6ONLY option.
func (so *SocketOptions) GetV6Only() bool {
	return atomic.LoadUint32(&so.v6OnlyEnabled) != 0
}

// SetV6Only sets value for IPV6_V6ONLY option.
//
// Preconditions: the backing TCP or UDP endpoint must be in initial state.
func (so *SocketOptions) SetV6Only(v bool) {
	storeAtomicBool(&so.v6OnlyEnabled, v)
}

// GetQuickAck gets value for TCP_QUICKACK option.
func (so *SocketOptions) GetQuickAck() bool {
	return atomic.LoadUint32(&so.quickAckEnabled) != 0
}

// SetQuickAck sets value for TCP_QUICKACK option.
func (so *SocketOptions) SetQuickAck(v bool) {
	storeAtomicBool(&so.quickAckEnabled, v)
}

// GetDelayOption gets inverted value for TCP_NODELAY option.
func (so *SocketOptions) GetDelayOption() bool {
	return atomic.LoadUint32(&so.delayOptionEnabled) != 0
}

// SetDelayOption sets inverted value for TCP_NODELAY option.
func (so *SocketOptions) SetDelayOption(v bool) {
	storeAtomicBool(&so.delayOptionEnabled, v)
	so.handler.OnDelayOptionSet(v)
}

// GetCorkOption gets value for TCP_CORK option.
func (so *SocketOptions) GetCorkOption() bool {
	return atomic.LoadUint32(&so.corkOptionEnabled) != 0
}

// SetCorkOption sets value for TCP_CORK option.
func (so *SocketOptions) SetCorkOption(v bool) {
	storeAtomicBool(&so.corkOptionEnabled, v)
	so.handler.OnCorkOptionSet(v)
}

// GetReceiveOriginalDstAddress gets value for IP(V6)_RECVORIGDSTADDR option.
func (so *SocketOptions) GetReceiveOriginalDstAddress() bool {
	return atomic.LoadUint32(&so.receiveOriginalDstAddress) != 0
}

// SetReceiveOriginalDstAddress sets value for IP(V6)_RECVORIGDSTADDR option.
func (so *SocketOptions) SetReceiveOriginalDstAddress(v bool) {
	storeAtomicBool(&so.receiveOriginalDstAddress, v)
}

// GetRecvError gets value for IP*_RECVERR option.
func (so *SocketOptions) GetRecvError() bool {
	return atomic.LoadUint32(&so.recvErrEnabled) != 0
}

// SetRecvError sets value for IP*_RECVERR option.
func (so *SocketOptions) SetRecvError(v bool) {
	storeAtomicBool(&so.recvErrEnabled, v)
	if !v {
		so.pruneErrQueue()
	}
}

// GetLastError gets value for SO_ERROR option.
func (so *SocketOptions) GetLastError() *Error {
	return so.handler.LastError()
}

// GetOutOfBandInline gets value for SO_OOBINLINE option.
func (*SocketOptions) GetOutOfBandInline() bool {
	return true
}

// SetOutOfBandInline sets value for SO_OOBINLINE option. We currently do not
// support disabling this option.
func (*SocketOptions) SetOutOfBandInline(bool) {}

// GetLinger gets value for SO_LINGER option.
func (so *SocketOptions) GetLinger() LingerOption {
	so.mu.Lock()
	linger := so.linger
	so.mu.Unlock()
	return linger
}

// SetLinger sets value for SO_LINGER option.
func (so *SocketOptions) SetLinger(linger LingerOption) {
	so.mu.Lock()
	so.linger = linger
	so.mu.Unlock()
}

// SockErrOrigin represents the constants for error origin.
type SockErrOrigin uint8

const (
	// SockExtErrorOriginNone represents an unknown error origin.
	SockExtErrorOriginNone SockErrOrigin = iota

	// SockExtErrorOriginLocal indicates a local error.
	SockExtErrorOriginLocal

	// SockExtErrorOriginICMP indicates an IPv4 ICMP error.
	SockExtErrorOriginICMP

	// SockExtErrorOriginICMP6 indicates an IPv6 ICMP error.
	SockExtErrorOriginICMP6
)

// IsICMPErr indicates if the error originated from an ICMP error.
func (origin SockErrOrigin) IsICMPErr() bool {
	return origin == SockExtErrorOriginICMP || origin == SockExtErrorOriginICMP6
}

// SockError represents a queue entry in the per-socket error queue.
//
// +stateify savable
type SockError struct {
	sockErrorEntry

	// Err is the error caused by the errant packet.
	Err *Error
	// ErrOrigin indicates the error origin.
	ErrOrigin SockErrOrigin
	// ErrType is the type in the ICMP header.
	ErrType uint8
	// ErrCode is the code in the ICMP header.
	ErrCode uint8
	// ErrInfo is additional info about the error.
	ErrInfo uint32

	// Payload is the errant packet's payload.
	Payload []byte
	// Dst is the original destination address of the errant packet.
	Dst FullAddress
	// Offender is the original sender address of the errant packet.
	Offender FullAddress
	// NetProto is the network protocol being used to transmit the packet.
	NetProto NetworkProtocolNumber
}

// pruneErrQueue resets the queue.
func (so *SocketOptions) pruneErrQueue() {
	so.errQueueMu.Lock()
	so.errQueue.Reset()
	so.errQueueMu.Unlock()
}

// DequeueErr dequeues a socket extended error from the error queue and returns
// it. Returns nil if queue is empty.
func (so *SocketOptions) DequeueErr() *SockError {
	so.errQueueMu.Lock()
	defer so.errQueueMu.Unlock()

	err := so.errQueue.Front()
	if err != nil {
		so.errQueue.Remove(err)
	}
	return err
}

// PeekErr returns the error in the front of the error queue. Returns nil if
// the error queue is empty.
func (so *SocketOptions) PeekErr() *SockError {
	so.errQueueMu.Lock()
	defer so.errQueueMu.Unlock()
	return so.errQueue.Front()
}

// QueueErr inserts the error at the back of the error queue.
//
// Preconditions: so.GetRecvError() == true.
func (so *SocketOptions) QueueErr(err *SockError) {
	so.errQueueMu.Lock()
	defer so.errQueueMu.Unlock()
	so.errQueue.PushBack(err)
}

// QueueLocalErr queues a local error onto the local queue.
func (so *SocketOptions) QueueLocalErr(err *Error, net NetworkProtocolNumber, info uint32, dst FullAddress, payload []byte) {
	so.QueueErr(&SockError{
		Err:       err,
		ErrOrigin: SockExtErrorOriginLocal,
		ErrInfo:   info,
		Payload:   payload,
		Dst:       dst,
		NetProto:  net,
	})
}

// GetBindToDevice gets value for SO_BINDTODEVICE option.
func (so *SocketOptions) GetBindToDevice() int32 {
	return atomic.LoadInt32(&so.bindToDevice)
}

// SetBindToDevice sets value for SO_BINDTODEVICE option.
func (so *SocketOptions) SetBindToDevice(bindToDevice int32) *Error {
	if !so.handler.HasNIC(bindToDevice) {
		return ErrUnknownDevice
	}

	atomic.StoreInt32(&so.bindToDevice, bindToDevice)
	return nil
}

// GetSendBufferSize gets value for SO_SNDBUF option.
func (so *SocketOptions) GetSendBufferSize() (int64, *Error) {
	if so.handler.IsUnixSocket() {
		return so.handler.GetSendBufferSize()
	}
	return atomic.LoadInt64(&so.sendBufferSize), nil
}

// SetSendBufferSize sets value for SO_SNDBUF option. notify indicates if the
// stack handler should be invoked to set the send buffer size.
func (so *SocketOptions) SetSendBufferSize(sendBufferSize int64, notify bool, getBufferLimits GetSendBufferLimits) {
	v := sendBufferSize
	ss := getBufferLimits(so.stackHandler)

	if notify {
		// TODO(b/176170271): Notify waiters after size has grown.
		// Make sure the send buffer size is within the min and max
		// allowed.
		min := int64(ss.Min)
		max := int64(ss.Max)
		// Validate the send buffer size with min and max values.
		// Multiply it by factor of 2.
		if v > max {
			v = max
		}

		if v < math.MaxInt32/PacketOverheadFactor {
			v *= PacketOverheadFactor
			if v < min {
				v = min
			}
		} else {
			v = math.MaxInt32
		}
	}
	atomic.StoreInt64(&so.sendBufferSize, v)
}