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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.
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) (RuleVerdict, int) {
return RuleAccept, 0
}
// DropTarget drops packets.
type DropTarget struct{}
// Action implements Target.Action.
func (DropTarget) Action(packet tcpip.PacketBuffer) (RuleVerdict, int) {
return RuleDrop, 0
}
// 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) (RuleVerdict, int) {
log.Debugf("ErrorTarget triggered.")
return RuleDrop, 0
}
// 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) (RuleVerdict, int) {
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) (RuleVerdict, int) {
return RuleReturn, 0
}
// 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 {
// TODO(gvisor.dev/issue/170): Other flags need to be added after
// we support them.
// RangeProtoSpecified flag indicates single port is specified to
// redirect.
RangeProtoSpecified bool
// 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.
// TODO(gvisor.dev/issue/170): Parse headers without copying. The current
// implementation only works for PREROUTING and calls pkt.Clone(), neither
// of which should be the case.
func (rt RedirectTarget) Action(pkt tcpip.PacketBuffer) (RuleVerdict, int) {
newPkt := pkt.Clone()
// Set network header.
headerView := newPkt.Data.First()
netHeader := header.IPv4(headerView)
newPkt.NetworkHeader = headerView[:header.IPv4MinimumSize]
hlen := int(netHeader.HeaderLength())
tlen := int(netHeader.TotalLength())
newPkt.Data.TrimFront(hlen)
newPkt.Data.CapLength(tlen - hlen)
// TODO(gvisor.dev/issue/170): Change destination address to
// loopback or interface address on which the packet was
// received.
// TODO(gvisor.dev/issue/170): Check Flags in RedirectTarget if
// we need to change dest address (for OUTPUT chain) or ports.
switch protocol := netHeader.TransportProtocol(); protocol {
case header.UDPProtocolNumber:
var udpHeader header.UDP
if newPkt.TransportHeader != nil {
udpHeader = header.UDP(newPkt.TransportHeader)
} else {
if len(pkt.Data.First()) < header.UDPMinimumSize {
return RuleDrop, 0
}
udpHeader = header.UDP(newPkt.Data.First())
}
udpHeader.SetDestinationPort(rt.MinPort)
case header.TCPProtocolNumber:
var tcpHeader header.TCP
if newPkt.TransportHeader != nil {
tcpHeader = header.TCP(newPkt.TransportHeader)
} else {
if len(pkt.Data.First()) < header.TCPMinimumSize {
return RuleDrop, 0
}
tcpHeader = header.TCP(newPkt.TransportHeader)
}
// TODO(gvisor.dev/issue/170): Need to recompute checksum
// and implement nat connection tracking to support TCP.
tcpHeader.SetDestinationPort(rt.MinPort)
default:
return RuleDrop, 0
}
return RuleAccept, 0
}
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