/**
* Generate (compute) a transaction ID for this SIP message.
* @return A string containing the concatenation of various
* portions of the From,To,Via and RequestURI portions
* of this message as specified in RFC 2543:
* All responses to a request contain the same values in
* the Call-ID, CSeq, To, and From fields
* (with the possible addition of a tag in the To field
* (section 10.43)). This allows responses to be matched with requests.
* Incorporates a bug fix for a bug sent in by Gordon Ledgard of
* IPera for generating transactionIDs when no port is present in the
* via header.
* Incorporates a bug fix for a bug report sent in by Chris Mills
* of Nortel Networks (converts to lower case when returning the
* transaction identifier).
*
*@return a string that can be used as a transaction identifier
* for this message. This can be used for matching responses and
* requests (i.e. an outgoing request and its matching response have
* the same computed transaction identifier).
*/
func (this *SIPMessage) GetTransactionId() string {
var topVia *header.Via
if this.GetViaHeaders().Len() > 0 {
topVia = this.GetViaHeaders().Front().Value.(*header.Via)
}
// Have specified a branch Identifier so we can use it to identify
// the transaction. BranchId is not case sensitive.
// Branch Id prefix is not case sensitive.
if topVia != nil && topVia.GetBranch() != "" &&
strings.Contains(strings.ToUpper(topVia.GetBranch()),
strings.ToUpper(header.SIPConstants_BRANCH_MAGIC_COOKIE)) {
// Bis 09 compatible branch assignment algorithm.
// implies that the branch id can be used as a transaction
// identifier.
return strings.ToLower(topVia.GetBranch())
} else {
// Old style client so construct the transaction identifier
// from various fields of the request.
var retval bytes.Buffer
from := this.GetFrom().(*header.From)
to := this.GetTo().(*header.To)
hpFrom := from.GetUserAtHostPort()
retval.WriteString(hpFrom + ":")
if from.HasTag() {
retval.WriteString(from.GetTag() + ":")
}
hpTo := to.GetUserAtHostPort()
retval.WriteString(hpTo + ":")
cid := this.callIdHeader.GetCallId()
retval.WriteString(cid + ":")
retval.WriteRune(rune(this.cSeqHeader.GetSequenceNumber()))
retval.WriteString(":" + this.cSeqHeader.GetMethod())
if topVia != nil {
retval.WriteString(":" + topVia.GetSentBy().String())
if !topVia.GetSentBy().HasPort() {
retval.WriteString(":")
retval.WriteRune(5060)
}
}
hc := ToHexString([]byte(strings.ToLower(retval.String())))
if len(hc) < 32 {
return hc
} else {
return hc[len(hc)-32 : len(hc)]
}
}
// Convert to lower case -- bug fix as a result of a bug report
// from Chris Mills of Nortel Networks.
}
