golang实现ping命令

// taken from http://golang.org/src/pkg/net/ipraw_test.go

package ping

import ( "bytes" "errors" "net" "os" "time" )

const ( icmpv4EchoRequest = 8 icmpv4EchoReply = 0 icmpv6EchoRequest = 128 icmpv6EchoReply = 129 )

type icmpMessage struct { Type int // type Code int // code Checksum int // checksum Body icmpMessageBody // body }

type icmpMessageBody interface { Len() int Marshal() ([]byte, error) }

// Marshal returns the binary enconding of the ICMP echo request or // reply message m. func (m *icmpMessage) Marshal() ([]byte, error) { b := []byte{byte(m.Type), byte(m.Code), 0, 0} if m.Body != nil && m.Body.Len() != 0 { mb, err := m.Body.Marshal() if err != nil { return nil, err } b = append(b, mb...) } switch m.Type { case icmpv6EchoRequest, icmpv6EchoReply: return b, nil } csumcv := len(b) - 1 // checksum coverage s := uint32(0) for i := 0; i < csumcv; i += 2 { s += uint32(b[i+1])<<8 | uint32(b[i]) } if csumcv&1 == 0 { s += uint32(b[csumcv]) } s = s>>16 + s&0xffff s = s + s>>16 // Place checksum back in header; using ^= avoids the // assumption the checksum bytes are zero. b[2] ^= byte(^s & 0xff) b[3] ^= byte(^s >> 8) return b, nil }

// parseICMPMessage parses b as an ICMP message. func parseICMPMessage(b []byte) (*icmpMessage, error) { msglen := len(b) if msglen < 4 { return nil, errors.New("message too short") } m := &icmpMessage{Type: int(b[0]), Code: int(b[1]), Checksum: int(b[2])<<8 | int(b[3])} if msglen > 4 { var err error switch m.Type { case icmpv4EchoRequest, icmpv4EchoReply, icmpv6EchoRequest, icmpv6EchoReply: m.Body, err = parseICMPEcho(b[4:]) if err != nil { return nil, err } } } return m, nil }

// imcpEcho represenets an ICMP echo request or reply message body. type icmpEcho struct { ID int // identifier Seq int // sequence number Data []byte // data }

func (p *icmpEcho) Len() int { if p == nil { return 0 } return 4 + len(p.Data) }

// Marshal returns the binary enconding of the ICMP echo request or // reply message body p. func (p *icmpEcho) Marshal() ([]byte, error) { b := make([]byte, 4+len(p.Data)) b[0], b[1] = byte(p.ID>>8), byte(p.ID&0xff) b[2], b[3] = byte(p.Seq>>8), byte(p.Seq&0xff) copy(b[4:], p.Data) return b, nil }

// parseICMPEcho parses b as an ICMP echo request or reply message body. func parseICMPEcho(b []byte) (*icmpEcho, error) { bodylen := len(b) p := &icmpEcho{ID: int(b[0])<<8 | int(b[1]), Seq: int(b[2])<<8 | int(b[3])} if bodylen > 4 { p.Data = make([]byte, bodylen-4) copy(p.Data, b[4:]) } return p, nil }

func Ping(address string, timeout int) (alive bool) { err := Pinger(address, timeout) alive = err == nil return }

func Pinger(address string, timeout int) (err error) { c, err := net.Dial("ip4:icmp", address) if err != nil { return } c.SetDeadline(time.Now().Add(time.Duration(timeout) * time.Second)) defer c.Close()

typ := icmpv4EchoRequest xid, xseq := os.Getpid()&0xffff, 1 wb, err := (&icmpMessage{ Type: typ, Code: 0, Body: &icmpEcho{ ID: xid, Seq: xseq, Data: bytes.Repeat([]byte("Go Go Gadget Ping!!!"), 3), }, }).Marshal() if err != nil { return } if _, err = c.Write(wb); err != nil { return } var m *icmpMessage rb := make([]byte, 20+len(wb)) for { if _, err = c.Read(rb); err != nil { return } rb = ipv4Payload(rb) if m, err = parseICMPMessage(rb); err != nil { return } switch m.Type { case icmpv4EchoRequest, icmpv6EchoRequest: continue } break } return }

func ipv4Payload(b []byte) []byte { if len(b) < 20 { return b } hdrlen := int(b[0]&0x0f) << 2 return b[hdrlen:] }