// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package netstack

import (
	"net"
	"sort"
	"syscall/zx"
	"syscall/zx/dispatch"
	"syscall/zx/fidl"
	"syscall/zx/zxwait"

	"syslog"

	"netstack/fidlconv"
	"netstack/link"
	"netstack/link/eth"
	"netstack/routes"

	"fidl/fuchsia/hardware/ethernet"
	fidlnet "fidl/fuchsia/net"
	"fidl/fuchsia/net/dhcp"
	"fidl/fuchsia/net/stack"
	"fidl/fuchsia/netstack"

	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/header"
	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
	tcpipstack "gvisor.dev/gvisor/pkg/tcpip/stack"
)

const zeroIpAddr = header.IPv4Any

type netstackImpl struct {
	ns                *Netstack
	dhcpClientService dhcp.ClientService
}

// interfaces2ListToInterfacesList converts a NetInterface2 list into a
// NetInterface one.
func interfaces2ListToInterfacesList(ifs2 []netstack.NetInterface2) []netstack.NetInterface {
	ifs := make([]netstack.NetInterface, 0, len(ifs2))
	for _, e2 := range ifs2 {
		ifs = append(ifs, netstack.NetInterface{
			Id:        e2.Id,
			Flags:     e2.Flags,
			Features:  e2.Features,
			Name:      e2.Name,
			Addr:      e2.Addr,
			Netmask:   e2.Netmask,
			Broadaddr: e2.Broadaddr,
			Hwaddr:    e2.Hwaddr,
			Ipv6addrs: e2.Ipv6addrs,
		})
	}
	return ifs
}

func (ns *Netstack) getNetInterfaces2() []netstack.NetInterface2 {
	nicInfos := ns.stack.NICInfo()
	interfaces := make([]netstack.NetInterface2, 0, len(nicInfos))
	for _, nicInfo := range nicInfos {
		ifs := nicInfo.Context.(*ifState)

		var ipv6addrs []fidlnet.Subnet
		for _, address := range nicInfo.ProtocolAddresses {
			if address.Protocol == ipv6.ProtocolNumber {
				ipv6addrs = append(ipv6addrs, fidlnet.Subnet{
					Addr:      fidlconv.ToNetIpAddress(address.AddressWithPrefix.Address),
					PrefixLen: uint8(address.AddressWithPrefix.PrefixLen),
				})
			}
		}

		netInterface := netstack.NetInterface2{
			Id:        uint32(ifs.nicid),
			Flags:     ifs.getFlags(),
			Metric:    uint32(ifs.mu.metric),
			Name:      nicInfo.Name,
			Hwaddr:    []uint8(ifs.endpoint.LinkAddress()[:]),
			Ipv6addrs: ipv6addrs,
		}

		if ifs.endpoint.Capabilities()&tcpipstack.CapabilityLoopback != 0 {
			netInterface.Features |= ethernet.InfoFeatureLoopback
		}

		if client, ok := ifs.controller.(*eth.Client); ok {
			netInterface.Features |= client.Info.Features
		}

		// Upstream reuses ErrNoLinkAddress to indicate no address can be found for the requested NIC and
		// network protocol.
		if addrWithPrefix, err := ifs.ns.stack.GetMainNICAddress(ifs.nicid, ipv4.ProtocolNumber); err != nil {
			syslog.Warnf("failed to call stack.GetMainNICAddress(_): %s", err)
		} else {
			if addrWithPrefix == (tcpip.AddressWithPrefix{}) {
				addrWithPrefix = tcpip.AddressWithPrefix{Address: zeroIpAddr, PrefixLen: 0}
			}
			mask := net.CIDRMask(addrWithPrefix.PrefixLen, len(addrWithPrefix.Address)*8)
			broadaddr := []byte(addrWithPrefix.Address)
			for i := range broadaddr {
				broadaddr[i] |= ^mask[i]
			}
			netInterface.Addr = fidlconv.ToNetIpAddress(addrWithPrefix.Address)
			netInterface.Netmask = fidlconv.ToNetIpAddress(tcpip.Address(mask))
			netInterface.Broadaddr = fidlconv.ToNetIpAddress(tcpip.Address(broadaddr))
		}

		interfaces = append(interfaces, netInterface)
	}

	return interfaces
}

func (ifs *ifState) getFlags() uint32 {
	var flags uint32
	ifs.mu.Lock()
	if ifs.mu.state == link.StateStarted {
		flags |= netstack.NetInterfaceFlagUp
	}
	if ifs.mu.dhcp.enabled {
		flags |= netstack.NetInterfaceFlagDhcp
	}
	ifs.mu.Unlock()
	return flags
}

func (ns *Netstack) getInterfaces2() []netstack.NetInterface2 {
	out := ns.getNetInterfaces2()

	sort.Slice(out, func(i, j int) bool {
		return out[i].Id < out[j].Id
	})

	return out
}

// GetInterfaces2 returns a list of interfaces.
// TODO(NET-2078): Move this to GetInterfaces once Chromium stops using
// netstack.fidl.
func (ni *netstackImpl) GetInterfaces2(fidl.Context) ([]netstack.NetInterface2, error) {
	return ni.ns.getInterfaces2(), nil
}

// GetInterfaces is a deprecated version that returns a list of interfaces in a
// format that Chromium supports. The new version is GetInterfaces2 which
// eventually will be renamed once Chromium is not using netstack.fidl anymore
// and this deprecated version can be removed.
func (ni *netstackImpl) GetInterfaces(fidl.Context) ([]netstack.NetInterface, error) {
	// Get the new interface list and convert to the old one.
	return interfaces2ListToInterfacesList(ni.ns.getInterfaces2()), nil
}

// TODO(NET-2078): Move this to GetRouteTable once Chromium stops using
// netstack.fidl.
func (ni *netstackImpl) GetRouteTable2(fidl.Context) ([]netstack.RouteTableEntry2, error) {
	return nsToRouteTable2(ni.ns.GetExtendedRouteTable()), nil
}

// GetRouteTable is a deprecated version that returns the route table in a
// format that Chromium supports. The new version is GetRouteTable2 which will
// eventually be renamed once Chromium is not using netstack.fidl anymore and
// this deprecated version can be removed.
func (ni *netstackImpl) GetRouteTable(fidl.Context) ([]netstack.RouteTableEntry, error) {
	rt2 := nsToRouteTable2(ni.ns.GetExtendedRouteTable())
	rt := make([]netstack.RouteTableEntry, 0, len(rt2))
	for _, r2 := range rt2 {
		var gateway fidlnet.IpAddress
		if r2.Gateway != nil {
			gateway = *r2.Gateway
		} else {
			gateway = fidlconv.ToNetIpAddress(zeroIpAddr)
		}
		rt = append(rt, netstack.RouteTableEntry{
			Destination: r2.Destination,
			Netmask:     r2.Netmask,
			Gateway:     gateway,
			Nicid:       r2.Nicid,
		})
	}
	return rt, nil
}

func nsToRouteTable2(table []routes.ExtendedRoute) []netstack.RouteTableEntry2 {
	out := make([]netstack.RouteTableEntry2, 0, len(table))
	for _, e := range table {
		var gatewayPtr *fidlnet.IpAddress
		if len(e.Route.Gateway) != 0 {
			gateway := fidlconv.ToNetIpAddress(e.Route.Gateway)
			gatewayPtr = &gateway
		}
		out = append(out, netstack.RouteTableEntry2{
			Destination: fidlconv.ToNetIpAddress(e.Route.Destination.ID()),
			Netmask:     fidlconv.ToNetIpAddress(tcpip.Address(e.Route.Destination.Mask())),
			Gateway:     gatewayPtr,
			Nicid:       uint32(e.Route.NIC),
			Metric:      uint32(e.Metric),
		})
	}
	return out
}

func routeToNs(r netstack.RouteTableEntry2) tcpip.Route {
	prefixLen, _ := net.IPMask(fidlconv.ToTCPIPAddress(r.Netmask)).Size()
	route := tcpip.Route{
		Destination: fidlconv.ToTCPIPSubnet(fidlnet.Subnet{
			Addr:      r.Destination,
			PrefixLen: uint8(prefixLen),
		}),
		NIC: tcpip.NICID(r.Nicid),
	}
	if g := r.Gateway; g != nil {
		route.Gateway = fidlconv.ToTCPIPAddress(*g)
	}
	return route
}

type routeTableTransactionImpl struct {
	ni *netstackImpl
}

func (i *routeTableTransactionImpl) AddRoute(_ fidl.Context, r netstack.RouteTableEntry2) (int32, error) {
	err := i.ni.ns.AddRoute(routeToNs(r), routes.Metric(r.Metric), false /* not dynamic */)
	if err != nil {
		return int32(zx.ErrInvalidArgs), err
	}
	return int32(zx.ErrOk), nil
}

func (i *routeTableTransactionImpl) DelRoute(_ fidl.Context, r netstack.RouteTableEntry2) (int32, error) {
	err := i.ni.ns.DelRoute(routeToNs(r))
	if err != nil {
		return int32(zx.ErrInvalidArgs), err
	}
	return int32(zx.ErrOk), nil
}

func (ni *netstackImpl) StartRouteTableTransaction(_ fidl.Context, req netstack.RouteTableTransactionWithCtxInterfaceRequest) (int32, error) {
	{
		ni.ns.mu.Lock()
		defer ni.ns.mu.Unlock()

		if ni.ns.mu.transactionRequest != nil {
			oldChannel := ni.ns.mu.transactionRequest.Channel
			observed, _ := zxwait.Wait(zx.Handle(oldChannel), 0, 0)
			// If the channel is neither readable nor writable, there is no
			// data left to be processed (not readable) and we can't return
			// any more results (not writable).  It's not enough to only
			// look at peerclosed because the peer can close the channel
			// while it still has data in its buffers.
			if observed&(zx.SignalChannelReadable|zx.SignalChannelWritable) == 0 {
				ni.ns.mu.transactionRequest = nil
			}
		}
		if ni.ns.mu.transactionRequest != nil {
			return int32(zx.ErrShouldWait), nil
		}
		ni.ns.mu.transactionRequest = &req
	}
	var routeTableService netstack.RouteTableTransactionService
	transaction := netstack.RouteTableTransactionWithCtxStub{Impl: &routeTableTransactionImpl{ni: ni}}
	// We don't use the error handler to free the channel because it's
	// possible that the peer closes the channel before our service has
	// finished processing.
	c := req.Channel
	_, err := routeTableService.AddToDispatcher(&transaction, c, ni.ns.dispatcher, nil)
	if err != nil {
		return int32(zx.ErrShouldWait), err
	}
	return int32(zx.ErrOk), err
}

// Add address to the given network interface.
func (ni *netstackImpl) SetInterfaceAddress(_ fidl.Context, nicid uint32, address fidlnet.IpAddress, prefixLen uint8) (netstack.NetErr, error) {
	protocolAddr := toProtocolAddr(stack.InterfaceAddress{
		IpAddress: address,
		PrefixLen: prefixLen,
	})
	if protocolAddr.AddressWithPrefix.PrefixLen > 8*len(protocolAddr.AddressWithPrefix.Address) {
		return netstack.NetErr{Status: netstack.StatusParseError, Message: "prefix length exceeds address length"}, nil
	}

	found, err := ni.ns.addInterfaceAddress(tcpip.NICID(nicid), protocolAddr)
	if err != nil {
		return netstack.NetErr{Status: netstack.StatusUnknownError, Message: err.Error()}, nil
	}
	if !found {
		return netstack.NetErr{Status: netstack.StatusUnknownInterface}, nil
	}
	return netstack.NetErr{Status: netstack.StatusOk}, nil
}

func (ni *netstackImpl) RemoveInterfaceAddress(_ fidl.Context, nicid uint32, address fidlnet.IpAddress, prefixLen uint8) (netstack.NetErr, error) {
	protocolAddr := toProtocolAddr(stack.InterfaceAddress{
		IpAddress: address,
		PrefixLen: prefixLen,
	})
	if protocolAddr.AddressWithPrefix.PrefixLen > 8*len(protocolAddr.AddressWithPrefix.Address) {
		return netstack.NetErr{Status: netstack.StatusParseError, Message: "prefix length exceeds address length"}, nil
	}

	found, err := ni.ns.removeInterfaceAddress(tcpip.NICID(nicid), protocolAddr)
	if err != nil {
		return netstack.NetErr{Status: netstack.StatusUnknownError, Message: err.Error()}, nil
	}
	if !found {
		return netstack.NetErr{Status: netstack.StatusUnknownInterface}, nil
	}
	return netstack.NetErr{Status: netstack.StatusOk}, nil
}

// SetInterfaceMetric changes the metric for an interface and updates all
// routes tracking that interface metric. This takes the lock.
func (ni *netstackImpl) SetInterfaceMetric(_ fidl.Context, nicid uint32, metric uint32) (result netstack.NetErr, err error) {
	syslog.Infof("update interface metric for NIC %d to metric=%d", nicid, metric)

	nic := tcpip.NICID(nicid)
	m := routes.Metric(metric)

	nicInfo, ok := ni.ns.stack.NICInfo()[nic]
	if !ok {
		return netstack.NetErr{Status: netstack.StatusUnknownInterface}, nil
	}

	ifState := nicInfo.Context.(*ifState)
	ifState.updateMetric(m)

	ni.ns.routeTable.UpdateMetricByInterface(nic, m)
	ni.ns.stack.SetRouteTable(ni.ns.routeTable.GetNetstackTable())
	return netstack.NetErr{Status: netstack.StatusOk}, nil
}

func (ni *netstackImpl) BridgeInterfaces(_ fidl.Context, nicids []uint32) (netstack.NetErr, uint32, error) {
	nics := make([]tcpip.NICID, len(nicids))
	for i, n := range nicids {
		nics[i] = tcpip.NICID(n)
	}
	ifs, err := ni.ns.Bridge(nics)
	if err != nil {
		return netstack.NetErr{Status: netstack.StatusUnknownError, Message: err.Error()}, 0, nil
	}
	return netstack.NetErr{Status: netstack.StatusOk}, uint32(ifs.nicid), nil
}

func (ni *netstackImpl) SetInterfaceStatus(_ fidl.Context, nicid uint32, enabled bool) error {
	nicInfo, ok := ni.ns.stack.NICInfo()[tcpip.NICID(nicid)]
	if !ok {
		// Returning a non-nil error here would close the channel to the client.
		return nil
	}
	ifs := nicInfo.Context.(*ifState)

	var err error
	var op string
	if enabled {
		err = ifs.controller.Up()
		op = "Up()"
	} else {
		err = ifs.controller.Down()
		op = "Down()"
	}

	if err != nil {
		syslog.Infof("(NIC %d).controller.%s = %s", nicid, op, err)
	}
	return nil
}

func (ni *netstackImpl) GetDhcpClient(ctx fidl.Context, id uint32, request dhcp.ClientWithCtxInterfaceRequest) (netstack.NetstackGetDhcpClientResult, error) {
	var result netstack.NetstackGetDhcpClientResult
	nicid := tcpip.NICID(id)
	if _, ok := ni.ns.stack.NICInfo()[nicid]; !ok {
		result.SetErr(int32(zx.ErrNotFound))
		return result, nil
	}
	d, ok := dispatch.GetDispatcher(ctx)
	if !ok {
		panic("no dispatcher on FIDL context")
	}
	s := &dhcp.ClientWithCtxStub{Impl: &clientImpl{ns: ni.ns, nicid: nicid}}
	if _, err := ni.dhcpClientService.BindingSet.AddToDispatcher(s, request.Channel, d, nil); err != nil {
		result.SetErr(int32(zx.ErrInternal))
		return result, nil
	}
	result.SetResponse(netstack.NetstackGetDhcpClientResponse{})
	return result, nil
}

func (ns *netstackImpl) AddEthernetDevice(_ fidl.Context, topological_path string, interfaceConfig netstack.InterfaceConfig, device ethernet.DeviceWithCtxInterface) (uint32, error) {
	ifs, err := ns.ns.addEth(topological_path, interfaceConfig, &device)
	if err != nil {
		return 0, err
	}
	return uint32(ifs.nicid), err
}