/
bpf.go
183 lines (146 loc) · 4.34 KB
/
bpf.go
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package qianmo
import (
"fmt"
"reflect"
"strconv"
"strings"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"golang.org/x/net/bpf"
)
var jumpTests = map[bpf.JumpTest]string{
bpf.JumpEqual: "JumpEqual",
bpf.JumpNotEqual: "JumpNotEqual",
bpf.JumpGreaterThan: "JumpGreaterThan",
bpf.JumpLessThan: "JumpLessThan",
bpf.JumpGreaterOrEqual: "JumpGreaterOrEqual",
bpf.JumpLessOrEqual: "JumpLessOrEqual",
bpf.JumpBitsSet: "JumpBitsSet",
bpf.JumpBitsNotSet: "JumpBitsNotSet",
}
// ParseTcpdumpFitlerData parses tcpdump filter to bpf.RawInstruction.
// Example:
// tcpdump -i eth0 -dd 'tcp and port 80'
func ParseTcpdumpFitlerData(data string) (raws []bpf.RawInstruction) {
lines := strings.Split(data, "\n")
for _, line := range lines {
line = strings.TrimSpace(line)
if line == "" {
continue
}
line = strings.TrimPrefix(line, "{")
line = strings.TrimSuffix(line, " },")
items := strings.Split(line, ",")
// assert len(items) == 4
raw := bpf.RawInstruction{
Op: uint16(s2int(items[0])),
Jt: uint8(s2int(items[1])),
Jf: uint8(s2int(items[2])),
K: uint32(s2int(items[3])),
}
raws = append(raws, raw)
}
return raws
}
// ParseTcpdumpFitlerExpr parses tcpdump filter to bpf.RawInstruction.
func ParseTcpdumpFitlerExpr(linkType layers.LinkType, expr string) (raws []bpf.RawInstruction, err error) {
insts, err := pcap.CompileBPFFilter(linkType, 1, expr)
if err != nil {
return nil, err
}
raws = make([]bpf.RawInstruction, 0, len(insts))
for _, inst := range insts {
raws = append(raws, bpf.RawInstruction{
Op: inst.Code,
Jt: inst.Jt,
Jf: inst.Jf,
K: inst.K,
})
}
return raws, nil
}
// CreateInstructionsFromData creates bpf.Instruction from tcpdump filter.
func CreateInstructionsFromData(data string) string {
raws := ParseTcpdumpFitlerData(data)
insts, _ := bpf.Disassemble(raws)
var filter = "var filter = []bpf.Instruction {\n"
var instStrs = make([]string, 0, len(insts))
for _, inst := range insts {
instStr := createInstruction(inst)
instStrs = append(instStrs, instStr)
filter += fmt.Sprintf("\t%s,\n", instStr)
}
filter += "}"
return filter
}
// CreateInstructionsFromExpr creates bpf.Instruction from tcpdump filter expression.
func CreateInstructionsFromExpr(linkType layers.LinkType, expr string) string {
raws, _ := ParseTcpdumpFitlerExpr(linkType, expr)
return CreateInstructionsFromRaws(raws)
}
// CreateInstructionsFromRaws creates bpf.Instruction from bpf.RawInstruction.
func CreateInstructionsFromRaws(raws []bpf.RawInstruction) string {
insts, _ := bpf.Disassemble(raws)
var filter = "var filter = []bpf.Instruction {\n"
var instStrs = make([]string, 0, len(insts))
for _, inst := range insts {
instStr := createInstruction(inst)
instStrs = append(instStrs, instStr)
filter += fmt.Sprintf("\t%s,\n", instStr)
}
filter += "}"
return filter
}
// createInstruction creates bpf.Instruction from bpf.RawInstruction.
func createInstruction(s bpf.Instruction) string {
v := reflect.ValueOf(s)
// 打印typename
t := v.Type()
str := fmt.Sprintf("bpf.%s{", t.Name())
var comment string
// 遍历结构体字段
for i := 0; i < v.NumField(); i++ {
// 获取每个字段的结构体Field
f := t.Field(i)
val := v.Field(i).Interface()
// 拼接字段名和值到字符串
if f.Name == "SkipTrue" || f.Name == "SkipFalse" {
if v, ok := val.(uint8); ok && v == 0 {
continue
}
}
// 拼接字段名和值到字符串
if t.Name() == "JumpIf" && f.Name == "Val" {
if v, ok := val.(uint32); ok && v > 15 {
comment += fmt.Sprintf(" %d = 0x%x,", val, val)
}
}
if t.Name() == "JumpIf" && f.Name == "Cond" {
if v, ok := val.(bpf.JumpTest); ok {
str += fmt.Sprintf("%s: bpf.%s,", f.Name, jumpTests[bpf.JumpTest(v)])
continue
}
}
if t.Name() == "RetConstant" && f.Name == "Val" {
str += fmt.Sprintf("%s: 0x%x,", f.Name, val)
continue
}
str += fmt.Sprintf("%s: %v,", f.Name, val)
}
str = strings.TrimSuffix(str, ",")
str += fmt.Sprintf("}")
if comment != "" {
comment = strings.TrimSuffix(comment, ",")
str += fmt.Sprintf(" // %s", comment)
}
return str
}
func s2int(s string) int {
s = strings.TrimSpace(s)
if strings.HasPrefix(s, "0x") {
result, _ := strconv.ParseInt(s, 0, 64)
return int(result)
}
result, _ := strconv.ParseInt(s, 10, 64)
return int(result)
}