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412 lines
10 KiB
412 lines
10 KiB
// SIP Message Library
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package sip
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import (
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"bytes"
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"errors"
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"fmt"
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"log"
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"net"
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"strconv"
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"strings"
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)
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type Headers map[string]string
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// Msg represents a SIP message. This can either be a request or a response.
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// These fields are never nil unless otherwise specified.
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type Msg struct {
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// Special non-SIP fields.
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SourceAddr *net.UDPAddr // Set by transport layer as received address
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// Fields that aren't headers.
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IsResponse bool // This is a response (like 404 Not Found)
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Method string // Indicates type of request (if request)
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Request *URI // dest URI (nil if response)
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Status int // Indicates happiness of response (if response)
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Phrase string // Explains happiness of response (if response)
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Payload string // Stuff that comes after two line breaks
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// Mandatory headers.
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Via *Via // Linked list of agents traversed (must have one)
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Route *Addr // Used for goose routing and loose routing
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RecordRoute *Addr // Used for loose routing
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From *Addr // Logical sender of message
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To *Addr // Logical destination of message
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CallID string // Identifies call from invite to bye
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CSeq int // Counter for network packet ordering
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CSeqMethod string // Helps with matching to orig message
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// Convenience headers.
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MaxForwards int // 0 has context specific meaning
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MinExpires int // Registrars need this when responding
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Expires int // Seconds registration should expire
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Paid *Addr // P-Asserted-Identity or nil (used for PSTN ANI)
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Rpid *Addr // Remote-Party-Id or nil
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Contact *Addr // Where we send response packets or nil
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// All the other headers (never nil)
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Headers Headers
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}
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func (msg *Msg) String() string {
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if msg == nil {
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return ""
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}
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var b bytes.Buffer
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if err := msg.Append(&b); err != nil {
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log.Println("Bad SIP message!", err)
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return ""
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}
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return b.String()
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}
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// Parses a SIP message into a data structure. This takes ~70 µs on average.
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func ParseMsg(packet string) (msg *Msg, err error) {
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msg = new(Msg)
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if packet == "" {
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return nil, errors.New("Empty msg")
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}
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if n := strings.Index(packet, "\r\n\r\n"); n > 0 {
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packet, msg.Payload = packet[0:n], packet[n+4:]
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}
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lines := strings.Split(packet, "\r\n")
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if lines == nil || len(lines) < 2 {
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return nil, errors.New("Too few lines")
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}
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var k, v string
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var okVia, okTo, okFrom, okCallID, okComputer bool
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err = msg.parseFirstLine(lines[0])
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if err != nil {
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return nil, err
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}
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hdrs := lines[1:]
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msg.Headers = make(map[string]string, len(hdrs))
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msg.MaxForwards = 70
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viap := &msg.Via
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contactp := &msg.Contact
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routep := &msg.Route
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rroutep := &msg.RecordRoute
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for _, hdr := range hdrs {
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if hdr == "" {
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continue
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}
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if hdr[0] == ' ' || hdr[0] == '\t' {
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v = strings.Trim(hdr, "\t ") // Line continuation.
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} else {
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if i := strings.Index(hdr, ": "); i > 0 {
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k, v = hdr[0:i], hdr[i+2:]
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k = strings.Trim(k, " \t")
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v = strings.Trim(v, " \t")
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k = uncompactHeader(k)
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if k == "" || v == "" {
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log.Println("Blank header found:", hdr)
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}
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} else {
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log.Println("Header missing delimiter:", hdr)
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continue
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}
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}
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switch strings.ToLower(k) {
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case "call-id":
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okCallID = true
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msg.CallID = v
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case "via":
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okVia = true
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*viap, err = ParseVia(v)
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if err != nil {
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return nil, errors.New("Bad Via header: " + err.Error())
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} else {
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viap = &(*viap).Next
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}
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case "to":
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okTo = true
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msg.To, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad To header: " + err.Error())
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}
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case "from":
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okFrom = true
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msg.From, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad From header: " + err.Error())
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}
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case "contact":
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*contactp, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad Contact header: " + err.Error())
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} else {
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contactp = &(*contactp).Last().Next
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}
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case "cseq":
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okComputer = false
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if n := strings.Index(v, " "); n > 0 {
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sseq, method := v[0:n], v[n+1:]
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if seq, err := strconv.Atoi(sseq); err == nil {
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msg.CSeq, msg.CSeqMethod = seq, method
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okComputer = true
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}
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}
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if !okComputer {
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return nil, errors.New("Bad CSeq Header")
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}
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case "content-length":
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if cl, err := strconv.Atoi(v); err == nil {
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if cl != len(msg.Payload) {
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return nil, errors.New(fmt.Sprintf(
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"Content-Length (%d) differs from payload length (%d)",
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cl, len(msg.Payload)))
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}
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} else {
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return nil, errors.New("Bad Content-Length header")
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}
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case "expires":
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if cl, err := strconv.Atoi(v); err == nil && cl >= 0 {
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msg.Expires = cl
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} else {
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return nil, errors.New("Bad Expires header")
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}
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case "min-expires":
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if cl, err := strconv.Atoi(v); err == nil && cl > 0 {
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msg.MinExpires = cl
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} else {
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return nil, errors.New("Bad Min-Expires header")
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}
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case "max-forwards":
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if cl, err := strconv.Atoi(v); err == nil && cl > 0 {
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msg.MaxForwards = cl
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} else {
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return nil, errors.New("Bad Max-Forwards header")
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}
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case "route":
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*routep, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad Route header: " + err.Error())
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} else {
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routep = &(*routep).Last().Next
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}
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case "record-route":
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*rroutep, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad Record-Route header: " + err.Error())
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} else {
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rroutep = &(*rroutep).Last().Next
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}
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case "p-asserted-identity":
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msg.Paid, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad P-Asserted-Identity header: " + err.Error())
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}
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case "remote-party-id":
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msg.Rpid, err = ParseAddr(v)
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if err != nil {
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return nil, errors.New("Bad Remote-Party-ID header: " + err.Error())
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}
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default:
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msg.Headers[k] = v
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}
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}
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if !okVia || !okTo || !okFrom || !okCallID || !okComputer {
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return nil, errors.New("Missing mandatory headers")
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}
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return
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}
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func (msg *Msg) Copy() *Msg {
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if msg == nil {
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return nil
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}
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res := new(Msg)
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*res = *msg
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res.To = msg.To.Copy()
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res.From = msg.From.Copy()
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res.Via = msg.Via.Copy()
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res.Paid = msg.Paid.Copy()
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res.Rpid = msg.Rpid.Copy()
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res.Route = msg.Route.Copy()
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res.Request = msg.Request.Copy()
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res.Contact = msg.Contact.Copy()
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res.RecordRoute = msg.RecordRoute.Copy()
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res.Headers = make(map[string]string, len(msg.Headers))
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for k, v := range msg.Headers {
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res.Headers[k] = v
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}
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return res
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}
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// i turn a sip message back into a packet
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func (msg *Msg) Append(b *bytes.Buffer) error {
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if !msg.IsResponse {
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if msg.Method == "" {
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return errors.New("Msg.Method not set")
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}
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if msg.Request == nil {
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return errors.New("msg.Request not set")
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}
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b.WriteString(msg.Method)
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b.WriteString(" ")
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msg.Request.Append(b)
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b.WriteString(" SIP/2.0\r\n")
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} else {
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if msg.Status < 100 {
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return errors.New("Msg.Status < 100")
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}
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if msg.Status >= 700 {
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return errors.New("Msg.Status >= 700")
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}
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if msg.Phrase == "" {
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msg.Phrase = Phrase(msg.Status)
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}
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b.WriteString("SIP/2.0 ")
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b.WriteString(strconv.Itoa(msg.Status))
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b.WriteString(" ")
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b.WriteString(msg.Phrase)
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b.WriteString("\r\n")
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}
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if msg.Via == nil {
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return errors.New("Need moar Via headers")
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}
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for viap := msg.Via; viap != nil; viap = viap.Next {
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b.WriteString("Via: ")
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if err := viap.Append(b); err != nil {
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return err
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}
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b.WriteString("\r\n")
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}
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if msg.Route != nil {
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b.WriteString("Route: ")
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if err := msg.Route.Append(b); err != nil {
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return err
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}
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b.WriteString("\r\n")
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}
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if msg.RecordRoute != nil {
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b.WriteString("Record-Route: ")
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if err := msg.RecordRoute.Append(b); err != nil {
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return err
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}
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b.WriteString("\r\n")
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}
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if msg.MaxForwards < 0 {
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return errors.New("MaxForwards is less than 0!!")
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} else if msg.MaxForwards == 0 {
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b.WriteString("Max-Forwards: 70\r\n")
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} else {
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b.WriteString("Max-Forwards: ")
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b.WriteString(strconv.Itoa(msg.MaxForwards))
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b.WriteString("\r\n")
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}
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b.WriteString("From: ")
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msg.From.Append(b)
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b.WriteString("\r\n")
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b.WriteString("To: ")
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msg.To.Append(b)
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b.WriteString("\r\n")
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if msg.CallID == "" {
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return errors.New("CallID is blank")
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}
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b.WriteString("Call-ID: ")
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b.WriteString(msg.CallID)
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b.WriteString("\r\n")
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if msg.CSeq < 0 || msg.CSeqMethod == "" {
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return errors.New("Bad CSeq")
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}
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b.WriteString("CSeq: ")
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b.WriteString(strconv.Itoa(msg.CSeq))
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b.WriteString(" ")
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b.WriteString(msg.CSeqMethod)
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b.WriteString("\r\n")
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if msg.Contact != nil {
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b.WriteString("Contact: ")
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msg.Contact.Append(b)
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b.WriteString("\r\n")
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}
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// Expires is allowed to be 0 for for REGISTER stuff.
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if msg.Expires > 0 ||
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msg.Method == "REGISTER" || msg.CSeqMethod == "REGISTER" {
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b.WriteString("Expires: ")
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b.WriteString(strconv.Itoa(msg.Expires))
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b.WriteString("\r\n")
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}
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if msg.MinExpires > 0 {
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b.WriteString("Min-Expires: ")
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b.WriteString(strconv.Itoa(msg.MinExpires))
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b.WriteString("\r\n")
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}
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if msg.Headers != nil {
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for k, v := range msg.Headers {
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if k == "" || v == "" {
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return errors.New("Header blank")
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}
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b.WriteString(k)
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b.WriteString(": ")
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b.WriteString(v)
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b.WriteString("\r\n")
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}
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}
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if msg.Paid != nil {
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b.WriteString("P-Asserted-Identity: ")
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msg.Paid.Append(b)
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b.WriteString("\r\n")
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}
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if msg.Rpid != nil {
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b.WriteString("Remote-Party-ID: ")
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msg.Rpid.Append(b)
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b.WriteString("\r\n")
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}
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b.WriteString("Content-Length: ")
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b.WriteString(strconv.Itoa(len(msg.Payload)))
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b.WriteString("\r\n\r\n")
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b.WriteString(msg.Payload)
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return nil
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}
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func (msg *Msg) parseFirstLine(s string) error {
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i := strings.Index(s, "SIP/2.0")
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if i == -1 {
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return errors.New("Not a SIP message")
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} else if i == 0 {
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msg.IsResponse = true
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toks := strings.SplitN(s, " ", 3)
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if len(toks) < 2 {
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return errors.New("Bad response status line")
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}
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s, err := strconv.Atoi(toks[1])
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if err != nil {
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return errors.New("Bad response status code")
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}
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msg.Status = s
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if len(toks) == 3 {
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msg.Phrase = toks[2]
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} else {
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msg.Phrase = Phrase(msg.Status)
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}
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} else {
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j := strings.Index(s, " ")
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msg.Method = s[:j]
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msg.Request = new(URI)
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r, err := ParseURI(s[j+1 : i-1])
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msg.Request = r
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if err != nil {
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return err
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}
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}
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return nil
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}
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