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// Copyright 2019 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.
// This file contains various Targets.
package iptables
import (
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
)
// AcceptTarget accepts packets.
type AcceptTarget struct{}
// Action implements Target.Action.
func (AcceptTarget) Action(packet tcpip.PacketBuffer, filter IPHeaderFilter) (RuleVerdict, string) {
return RuleAccept, ""
}
// DropTarget drops packets.
type DropTarget struct{}
// Action implements Target.Action.
func (DropTarget) Action(packet tcpip.PacketBuffer, filter IPHeaderFilter) (RuleVerdict, string) {
return RuleDrop, ""
}
// ErrorTarget logs an error and drops the packet. It represents a target that
// should be unreachable.
type ErrorTarget struct{}
// Action implements Target.Action.
func (ErrorTarget) Action(packet tcpip.PacketBuffer, filter IPHeaderFilter) (RuleVerdict, string) {
log.Debugf("ErrorTarget triggered.")
return RuleDrop, ""
}
// UserChainTarget marks a rule as the beginning of a user chain.
type UserChainTarget struct {
Name string
}
// Action implements Target.Action.
func (UserChainTarget) Action(tcpip.PacketBuffer, IPHeaderFilter) (RuleVerdict, string) {
panic("UserChainTarget should never be called.")
}
// ReturnTarget returns from the current chain. If the chain is a built-in, the
// hook's underflow should be called.
type ReturnTarget struct{}
// Action implements Target.Action.
func (ReturnTarget) Action(tcpip.PacketBuffer, IPHeaderFilter) (RuleVerdict, string) {
return RuleReturn, ""
}
// RedirectTarget redirects the packet by modifying the destination port/IP.
// Min and Max values for IP and Ports in the struct indicate the range of
// values which can be used to redirect.
type RedirectTarget struct {
// Flags to check if the redirect is for address or ports.
Flags uint32
// Min address used to redirect.
MinIP tcpip.Address
// Max address used to redirect.
MaxIP tcpip.Address
// Min port used to redirect.
MinPort uint16
// Max port used to redirect.
MaxPort uint16
}
// Action implements Target.Action.
func (rt RedirectTarget) Action(pkt tcpip.PacketBuffer, filter IPHeaderFilter) (RuleVerdict, string) {
headerView := pkt.Data.First()
// Network header should be set.
netHeader := header.IPv4(headerView)
if netHeader == nil {
return RuleDrop, ""
}
// TODO(gvisor.dev/issue/170): Check Flags in RedirectTarget if
// we need to change dest address (for OUTPUT chain) or ports.
hlen := int(netHeader.HeaderLength())
switch protocol := filter.Protocol; protocol {
case header.UDPProtocolNumber:
udp := header.UDP(headerView[hlen:])
udp.SetDestinationPort(rt.MinPort)
case header.TCPProtocolNumber:
// TODO(gvisor.dev/issue/170): Need to recompute checksum
// and implement nat connection tracking to support TCP.
tcp := header.TCP(headerView[hlen:])
tcp.SetDestinationPort(rt.MinPort)
default:
return RuleDrop, ""
}
return RuleAccept, ""
}
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