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dissect.go
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dissect.go
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// SPDX-License-Identifier: Apache-2.0
// Copyright Authors of Cilium
package monitor
import (
"encoding/hex"
"fmt"
"net"
"strconv"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/cilium/cilium/pkg/lock"
"github.com/cilium/cilium/pkg/logging"
"github.com/cilium/cilium/pkg/logging/logfields"
)
type DisplayFormat bool
const (
DisplayLabel DisplayFormat = false
DisplayNumeric DisplayFormat = true
)
type parserCache struct {
eth layers.Ethernet
ip4 layers.IPv4
ip6 layers.IPv6
icmp4 layers.ICMPv4
icmp6 layers.ICMPv6
tcp layers.TCP
udp layers.UDP
sctp layers.SCTP
decoded []gopacket.LayerType
}
var (
cache *parserCache
dissectLock lock.Mutex
parser *gopacket.DecodingLayerParser
log = logging.DefaultLogger.WithField(logfields.LogSubsys, "monitor")
)
// getParser must be called with dissectLock held
func initParser() {
if cache == nil {
log.Info("Initializing dissection cache...")
cache = &parserCache{
decoded: []gopacket.LayerType{},
}
parser = gopacket.NewDecodingLayerParser(
layers.LayerTypeEthernet,
&cache.eth, &cache.ip4, &cache.ip6,
&cache.icmp4, &cache.icmp6, &cache.tcp, &cache.udp,
&cache.sctp)
}
}
func getTCPInfo() string {
info := ""
addTCPFlag := func(flag, new string) string {
if flag == "" {
return new
}
return flag + ", " + new
}
if cache.tcp.SYN {
info = addTCPFlag(info, "SYN")
}
if cache.tcp.ACK {
info = addTCPFlag(info, "ACK")
}
if cache.tcp.RST {
info = addTCPFlag(info, "RST")
}
if cache.tcp.FIN {
info = addTCPFlag(info, "FIN")
}
return info
}
// ConnectionInfo contains tuple information and icmp code for a connection
type ConnectionInfo struct {
SrcIP net.IP
DstIP net.IP
SrcPort uint16
DstPort uint16
Proto string
IcmpCode string
}
// getConnectionInfoFromCache assume dissectLock is obtained at the caller and data is already
// parsed to cache.decoded
func getConnectionInfoFromCache() (c *ConnectionInfo, hasIP, hasEth bool) {
c = &ConnectionInfo{}
for _, typ := range cache.decoded {
switch typ {
case layers.LayerTypeEthernet:
hasEth = true
case layers.LayerTypeIPv4:
hasIP = true
c.SrcIP, c.DstIP = cache.ip4.SrcIP, cache.ip4.DstIP
case layers.LayerTypeIPv6:
hasIP = true
c.SrcIP, c.DstIP = cache.ip6.SrcIP, cache.ip6.DstIP
case layers.LayerTypeTCP:
c.Proto = "tcp"
c.SrcPort, c.DstPort = uint16(cache.tcp.SrcPort), uint16(cache.tcp.DstPort)
case layers.LayerTypeUDP:
c.Proto = "udp"
c.SrcPort, c.DstPort = uint16(cache.udp.SrcPort), uint16(cache.udp.DstPort)
case layers.LayerTypeSCTP:
c.Proto = "sctp"
c.SrcPort, c.DstPort = uint16(cache.sctp.SrcPort), uint16(cache.sctp.DstPort)
case layers.LayerTypeIPSecAH:
c.Proto = "IPsecAH"
case layers.LayerTypeIPSecESP:
c.Proto = "IPsecESP"
case layers.LayerTypeICMPv4:
c.Proto = "icmp"
c.IcmpCode = cache.icmp4.TypeCode.String()
case layers.LayerTypeICMPv6:
c.Proto = "icmp"
c.IcmpCode = cache.icmp6.TypeCode.String()
}
}
return c, hasIP, hasEth
}
// GetConnectionInfo returns the ConnectionInfo structure from data
func GetConnectionInfo(data []byte) *ConnectionInfo {
dissectLock.Lock()
defer dissectLock.Unlock()
initParser()
parser.DecodeLayers(data, &cache.decoded)
c, _, _ := getConnectionInfoFromCache()
return c
}
// GetConnectionSummary decodes the data into layers and returns a connection
// summary in the format:
//
// - sIP:sPort -> dIP:dPort, e.g. 1.1.1.1:2000 -> 2.2.2.2:80
// - sIP -> dIP icmpCode, 1.1.1.1 -> 2.2.2.2 echo-request
func GetConnectionSummary(data []byte) string {
dissectLock.Lock()
defer dissectLock.Unlock()
initParser()
parser.DecodeLayers(data, &cache.decoded)
c, hasIP, hasEth := getConnectionInfoFromCache()
srcIP, dstIP := c.SrcIP, c.DstIP
srcPort, dstPort := strconv.Itoa(int(c.SrcPort)), strconv.Itoa(int(c.DstPort))
icmpCode, proto := c.IcmpCode, c.Proto
switch {
case icmpCode != "":
return fmt.Sprintf("%s -> %s %s", srcIP, dstIP, icmpCode)
case proto != "":
var s string
if proto == "esp" {
s = proto
} else {
s = fmt.Sprintf("%s -> %s %s",
net.JoinHostPort(srcIP.String(), srcPort),
net.JoinHostPort(dstIP.String(), dstPort),
proto)
}
if proto == "tcp" {
s += " " + getTCPInfo()
}
return s
case hasIP:
return fmt.Sprintf("%s -> %s", srcIP, dstIP)
case hasEth:
return fmt.Sprintf("%s -> %s %s", cache.eth.SrcMAC, cache.eth.DstMAC, cache.eth.EthernetType.String())
}
return "[unknown]"
}
// Dissect parses and prints the provided data if dissect is set to true,
// otherwise the data is printed as HEX output
func Dissect(dissect bool, data []byte) {
if dissect {
dissectLock.Lock()
defer dissectLock.Unlock()
initParser()
err := parser.DecodeLayers(data, &cache.decoded)
for _, typ := range cache.decoded {
switch typ {
case layers.LayerTypeEthernet:
fmt.Println(gopacket.LayerString(&cache.eth))
case layers.LayerTypeIPv4:
fmt.Println(gopacket.LayerString(&cache.ip4))
case layers.LayerTypeIPv6:
fmt.Println(gopacket.LayerString(&cache.ip6))
case layers.LayerTypeTCP:
fmt.Println(gopacket.LayerString(&cache.tcp))
case layers.LayerTypeUDP:
fmt.Println(gopacket.LayerString(&cache.udp))
case layers.LayerTypeSCTP:
fmt.Println(gopacket.LayerString(&cache.sctp))
case layers.LayerTypeICMPv4:
fmt.Println(gopacket.LayerString(&cache.icmp4))
case layers.LayerTypeICMPv6:
fmt.Println(gopacket.LayerString(&cache.icmp6))
default:
fmt.Println("Unknown layer")
}
}
if parser.Truncated {
fmt.Println(" Packet has been truncated")
}
if err != nil {
fmt.Println(" Failed to decode layer:", err)
}
} else {
fmt.Print(hex.Dump(data))
}
}
// Flow contains source and destination
type Flow struct {
Src string `json:"src"`
Dst string `json:"dst"`
}
// DissectSummary bundles decoded layers into json-marshallable message
type DissectSummary struct {
Ethernet string `json:"ethernet,omitempty"`
IPv4 string `json:"ipv4,omitempty"`
IPv6 string `json:"ipv6,omitempty"`
TCP string `json:"tcp,omitempty"`
UDP string `json:"udp,omitempty"`
SCTP string `json:"sctp,omitempty"`
ICMPv4 string `json:"icmpv4,omitempty"`
ICMPv6 string `json:"icmpv6,omitempty"`
L2 *Flow `json:"l2,omitempty"`
L3 *Flow `json:"l3,omitempty"`
L4 *Flow `json:"l4,omitempty"`
}
// GetDissectSummary returns DissectSummary created from data
func GetDissectSummary(data []byte) *DissectSummary {
dissectLock.Lock()
defer dissectLock.Unlock()
initParser()
parser.DecodeLayers(data, &cache.decoded)
ret := &DissectSummary{}
for _, typ := range cache.decoded {
switch typ {
case layers.LayerTypeEthernet:
ret.Ethernet = gopacket.LayerString(&cache.eth)
src, dst := cache.eth.LinkFlow().Endpoints()
ret.L2 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeIPv4:
ret.IPv4 = gopacket.LayerString(&cache.ip4)
src, dst := cache.ip4.NetworkFlow().Endpoints()
ret.L3 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeIPv6:
ret.IPv6 = gopacket.LayerString(&cache.ip6)
src, dst := cache.ip6.NetworkFlow().Endpoints()
ret.L3 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeTCP:
ret.TCP = gopacket.LayerString(&cache.tcp)
src, dst := cache.tcp.TransportFlow().Endpoints()
ret.L4 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeUDP:
ret.UDP = gopacket.LayerString(&cache.udp)
src, dst := cache.udp.TransportFlow().Endpoints()
ret.L4 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeSCTP:
ret.SCTP = gopacket.LayerString(&cache.sctp)
src, dst := cache.sctp.TransportFlow().Endpoints()
ret.L4 = &Flow{Src: src.String(), Dst: dst.String()}
case layers.LayerTypeICMPv4:
ret.ICMPv4 = gopacket.LayerString(&cache.icmp4)
case layers.LayerTypeICMPv6:
ret.ICMPv6 = gopacket.LayerString(&cache.icmp6)
}
}
return ret
}