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117 lines
3.0 KiB
117 lines
3.0 KiB
// SIP Transport Layer. Responsible for serializing messages to/from
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// your network.
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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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"flag"
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"net"
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"time"
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)
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var (
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tracing = flag.Bool("tracing", true, "Enable SIP message tracing")
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timestampTagging = flag.Bool("timestampTagging", false, "Add microsecond timestamps to Via tags")
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)
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// Transport sends and receives SIP messages over UDP with stateless routing.
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type Transport struct {
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// Channel to which received SIP messages and errors are published.
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C chan *Msg
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E chan error
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// Underlying UDP socket.
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Sock *net.UDPConn
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// When you send an outbound request (not a response) you have to set the via
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// tag: ``msg.Via = tp.Via.Copy().Branch().SetNext(msg.Via)``. The details of
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// the branch parameter... are tricky.
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Via *Via
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// Contact that gets put in outbound SIP messages.
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Contact *Addr
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}
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// Creates a new stateless network mechanism for transmitting and receiving SIP
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// signalling messages.
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//
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// contact is a SIP address, e.g. "<sip:1.2.3.4>", that tells how to bind
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// sockets. If contact.Uri.Port is 0, it'll be mutated with a randomly selected
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// port. This value is also used for contact headers which tell other
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// user-agents where to send responses and hence should only contain an IP or
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// canonical address.
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func NewTransport(contact *Addr) (tp *Transport, err error) {
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saddr := net.JoinHostPort(contact.Uri.Host, portstr(contact.Uri.Port))
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c, err := net.ListenPacket("udp", saddr)
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if err != nil {
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return nil, err
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}
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sock := c.(*net.UDPConn)
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addr := c.LocalAddr().(*net.UDPAddr)
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contact = contact.Copy()
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contact.Next = nil
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contact.Uri.Port = uint16(addr.Port)
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contact.Uri.Params["transport"] = "udp"
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tp = &Transport{
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C: make(chan *Msg, 32),
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E: make(chan error, 1),
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Sock: sock,
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Contact: contact,
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Via: &Via{
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Host: addr.IP.String(),
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Port: uint16(addr.Port),
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},
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}
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go ReceiveMessages(contact, sock, tp.C, tp.E)
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return
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}
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// Sends a SIP message.
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func (tp *Transport) Send(msg *Msg) error {
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msg, hostport, err := RouteMessage(tp.Via, tp.Contact, msg)
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if err != nil {
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return err
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}
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addr, err := net.ResolveUDPAddr("udp", hostport)
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if err != nil {
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return err
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}
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if msg.MaxForwards > 0 {
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msg.MaxForwards--
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}
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ts := time.Now()
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addTimestamp(msg, ts)
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var b bytes.Buffer
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msg.Append(&b)
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if *tracing {
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trace("send", b.String(), addr, ts)
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}
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_, err = tp.Sock.WriteTo(b.Bytes(), addr)
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if err != nil {
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return err
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}
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return nil
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}
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// Checks if message is acceptable, otherwise sets msg.Error and returns false.
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func (tp *Transport) sanityCheck(msg *Msg) error {
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if msg.MaxForwards <= 0 {
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tp.Send(NewResponse(msg, StatusTooManyHops))
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return errors.New("Froot loop detected")
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}
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if msg.IsResponse {
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if msg.Status >= 700 {
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tp.Send(NewResponse(msg, StatusBadRequest))
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return errors.New("Crazy status number")
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}
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} else {
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if msg.CSeqMethod == "" || msg.CSeqMethod != msg.Method {
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tp.Send(NewResponse(msg, StatusBadRequest))
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return errors.New("Bad CSeq")
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}
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}
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return nil
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}
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