status-go/vendor/github.com/koron/go-ssdp/advertise.go

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package ssdp
import (
"bufio"
"bytes"
"fmt"
"io"
"net"
"net/http"
"sync"
)
type message struct {
to net.Addr
data []byte
}
// Advertiser is a server to advertise a service.
type Advertiser struct {
st string
usn string
location string
server string
maxAge int
conn *multicastConn
ch chan *message
wg sync.WaitGroup
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wgS sync.WaitGroup
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}
// Advertise starts advertisement of service.
func Advertise(st, usn, location, server string, maxAge int) (*Advertiser, error) {
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conn, err := multicastListen(recvAddrResolver)
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if err != nil {
return nil, err
}
logf("SSDP advertise on: %s", conn.LocalAddr().String())
a := &Advertiser{
st: st,
usn: usn,
location: location,
server: server,
maxAge: maxAge,
conn: conn,
ch: make(chan *message),
}
a.wg.Add(2)
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a.wgS.Add(1)
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go func() {
a.sendMain()
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a.wgS.Done()
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a.wg.Done()
}()
go func() {
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a.recvMain()
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a.wg.Done()
}()
return a, nil
}
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func (a *Advertiser) recvMain() error {
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err := a.conn.readPackets(0, func(addr net.Addr, data []byte) error {
if err := a.handleRaw(addr, data); err != nil {
logf("failed to handle message: %s", err)
}
return nil
})
if err != nil && err != io.EOF {
return err
}
return nil
}
func (a *Advertiser) sendMain() error {
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for msg := range a.ch {
_, err := a.conn.WriteTo(msg.data, msg.to)
if err != nil {
if nerr, ok := err.(net.Error); !ok || !nerr.Temporary() {
logf("failed to send: %s", err)
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}
}
}
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return nil
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}
func (a *Advertiser) handleRaw(from net.Addr, raw []byte) error {
if !bytes.HasPrefix(raw, []byte("M-SEARCH ")) {
// unexpected method.
return nil
}
req, err := http.ReadRequest(bufio.NewReader(bytes.NewReader(raw)))
if err != nil {
return err
}
var (
man = req.Header.Get("MAN")
st = req.Header.Get("ST")
)
if man != `"ssdp:discover"` {
return fmt.Errorf("unexpected MAN: %s", man)
}
if st != All && st != RootDevice && st != a.st {
// skip when ST is not matched/expected.
return nil
}
logf("received M-SEARCH MAN=%s ST=%s from %s", man, st, from.String())
// build and send a response.
msg, err := buildOK(a.st, a.usn, a.location, a.server, a.maxAge)
if err != nil {
return err
}
a.ch <- &message{to: from, data: msg}
return nil
}
func buildOK(st, usn, location, server string, maxAge int) ([]byte, error) {
b := new(bytes.Buffer)
// FIXME: error should be checked.
b.WriteString("HTTP/1.1 200 OK\r\n")
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fmt.Fprintf(b, "EXT: \r\n")
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fmt.Fprintf(b, "ST: %s\r\n", st)
fmt.Fprintf(b, "USN: %s\r\n", usn)
if location != "" {
fmt.Fprintf(b, "LOCATION: %s\r\n", location)
}
if server != "" {
fmt.Fprintf(b, "SERVER: %s\r\n", server)
}
fmt.Fprintf(b, "CACHE-CONTROL: max-age=%d\r\n", maxAge)
b.WriteString("\r\n")
return b.Bytes(), nil
}
// Close stops advertisement.
func (a *Advertiser) Close() error {
if a.conn != nil {
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// closing order is very important. be careful to change:
// stop sending loop by closing the channel and wait it.
close(a.ch)
a.wgS.Wait()
// stop receiving loop by closing the connection.
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a.conn.Close()
a.wg.Wait()
a.conn = nil
}
return nil
}
// Alive announces ssdp:alive message.
func (a *Advertiser) Alive() error {
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addr, err := multicastSendAddr()
if err != nil {
return err
}
msg, err := buildAlive(addr, a.st, a.usn, a.location, a.server,
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a.maxAge)
if err != nil {
return err
}
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a.ch <- &message{to: addr, data: msg}
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logf("sent alive")
return nil
}
// Bye announces ssdp:byebye message.
func (a *Advertiser) Bye() error {
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addr, err := multicastSendAddr()
if err != nil {
return err
}
msg, err := buildBye(addr, a.st, a.usn)
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if err != nil {
return err
}
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a.ch <- &message{to: addr, data: msg}
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logf("sent bye")
return nil
}