forked from greenpau/cni-plugins
/
dest_nat_rewrite.go
188 lines (162 loc) · 4.26 KB
/
dest_nat_rewrite.go
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package utils
import (
"fmt"
"github.com/google/nftables"
"github.com/google/nftables/binaryutil"
"github.com/google/nftables/expr"
"golang.org/x/sys/unix"
"net"
)
// AddDestinationNatRewriteRules destination rewrite rule for the traffic
// arriving on a specific port.
func AddDestinationNatRewriteRules(opts map[string]interface{}) error {
v := opts["version"].(string)
tableName := opts["table"].(string)
chainName := opts["chain"].(string)
bridgeIntfName := opts["bridge_interface"].(string)
addr := opts["ip_address"].(net.IPNet)
pm := opts["port_mapping"].(MappingEntry)
conn, err := initNftConn()
if err != nil {
return err
}
tb := &nftables.Table{
Name: tableName,
}
if v == "4" {
tb.Family = nftables.TableFamilyIPv4
} else {
tb.Family = nftables.TableFamilyIPv6
}
ch := &nftables.Chain{
Name: chainName,
Table: tb,
}
r := &nftables.Rule{
Table: tb,
Chain: ch,
Exprs: []expr.Any{},
}
// counter packets 0 bytes 0
r.Exprs = append(r.Exprs, &expr.Counter{})
// match all interface but the interface
r.Exprs = append(r.Exprs, &expr.Meta{
Key: expr.MetaKeyIIFNAME,
Register: 1,
})
r.Exprs = append(r.Exprs, &expr.Cmp{
//Op: expr.CmpOpEq,
Op: expr.CmpOpNeq,
Register: 1,
Data: EncodeInterfaceName(bridgeIntfName),
})
// tcp dport <RCV_PORT_NUM>
r.Exprs = append(r.Exprs, &expr.Meta{
Key: expr.MetaKeyL4PROTO,
Register: 1,
})
switch pm.Protocol {
case "tcp":
r.Exprs = append(r.Exprs, &expr.Cmp{
Op: expr.CmpOpEq,
Register: 1,
Data: []byte{unix.IPPROTO_TCP},
})
case "udp":
r.Exprs = append(r.Exprs, &expr.Cmp{
Op: expr.CmpOpEq,
Register: 1,
Data: []byte{unix.IPPROTO_UDP},
})
default:
return fmt.Errorf("unsupported protocol: %s", pm.Protocol)
}
// [ payload load 2b @ transport header + 2 => reg 1 ]
r.Exprs = append(r.Exprs, &expr.Payload{
DestRegister: 1,
Base: expr.PayloadBaseTransportHeader,
Offset: 2, // TODO
Len: 2, // TODO
})
// [ cmp eq reg 1 0x0000e60f ]
r.Exprs = append(r.Exprs, &expr.Cmp{
Op: expr.CmpOpEq,
Register: 1,
Data: binaryutil.BigEndian.PutUint16(uint16(pm.HostPort)),
})
if v == "4" {
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 1,
Data: addr.IP.To4(),
})
} else {
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 1,
Data: addr.IP.To16(),
})
}
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 2,
Data: binaryutil.BigEndian.PutUint16(uint16(pm.ContainerPort)),
})
// ip daddr set <IP_ADDRESS>
if v == "4" {
// [ immediate reg 1 0x6600580a ]
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 1,
Data: addr.IP.To4(),
})
// [ payload write reg 1 => 4b @ network header + 16 csum_type 1 csum_off 10 csum_flags 0x1 ]
r.Exprs = append(r.Exprs, &expr.Payload{
OperationType: expr.PayloadWrite,
SourceRegister: 1,
Base: expr.PayloadBaseNetworkHeader,
Offset: 16,
Len: 4,
CsumType: expr.CsumTypeInet,
CsumOffset: 10,
CsumFlags: unix.NFT_PAYLOAD_L4CSUM_PSEUDOHDR,
})
} else {
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 1,
Data: addr.IP.To16(),
})
r.Exprs = append(r.Exprs, &expr.Payload{
OperationType: expr.PayloadWrite,
SourceRegister: 1,
Base: expr.PayloadBaseNetworkHeader,
Offset: 24,
Len: 16,
CsumType: expr.CsumTypeInet,
CsumOffset: 10,
CsumFlags: unix.NFT_PAYLOAD_L4CSUM_PSEUDOHDR,
})
}
// tcp dport set <MAPPED_PORT_NUM>
r.Exprs = append(r.Exprs, &expr.Immediate{
Register: 1,
Data: binaryutil.BigEndian.PutUint16(uint16(pm.ContainerPort)),
})
// [ payload write reg 1 => 2b @ transport header + 2 csum_type 1 csum_off 16 csum_flags 0x0 ]
r.Exprs = append(r.Exprs, &expr.Payload{
OperationType: expr.PayloadWrite,
SourceRegister: 1,
Base: expr.PayloadBaseTransportHeader,
Offset: 2,
Len: 2,
CsumType: expr.CsumTypeInet,
CsumOffset: 16,
CsumFlags: unix.NFT_PAYLOAD_CSUM_NONE,
})
// return
// [ immediate reg 0 return ]
r.Exprs = append(r.Exprs, &expr.Verdict{
Kind: expr.VerdictReturn,
})
conn.AddRule(r)
if err := conn.Flush(); err != nil {
return err
}
return nil
}