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server.go
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server.go
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package server
import (
"context"
"log"
"net"
"time"
"github.com/markpash/pcpd/internal/messages"
"github.com/markpash/pcpd/internal/server/config"
"inet.af/netaddr"
)
// We need to keep a record of when the server started for epoch time
var startTime = time.Now()
func Start(ctx context.Context, cfg config.Config) error {
listenPCP := func(network string, laddr netaddr.IP) (*net.UDPConn, error) {
return net.ListenUDP(network, &net.UDPAddr{
IP: laddr.IPAddr().IP,
Port: 5351,
})
}
var (
conn4 *net.UDPConn
conn6 *net.UDPConn
)
incoming := make(chan messages.Request)
defer close(incoming)
if cfg.IPv4 {
conn4, err := listenPCP("udp4", netaddr.MustParseIP("0.0.0.0"))
if err != nil {
return err
}
go readRequests(ctx, conn4, incoming)
}
if cfg.IPv6 {
conn6, err := listenPCP("udp6", netaddr.MustParseIP("::"))
if err != nil {
return err
}
go readRequests(ctx, conn6, incoming)
}
for {
select {
case <-ctx.Done():
return nil
case msg := <-incoming:
conn := conn6
if msg.ClientIP.Unmap().Is4() {
conn = conn4
}
log.Printf("%+v", msg)
// Skipping requests that aren't Announce or Map for now
if msg.Operation != messages.Announce && msg.Operation != messages.Map {
continue
}
response := processRequest(msg)
_, err := conn.WriteTo(response.MarshalBinary(), msg.ClientIP.Unmap().IPAddr())
if err != nil {
continue
}
}
}
}
func readRequests(ctx context.Context, conn *net.UDPConn, c chan<- messages.Request) {
buf := make([]byte, 1100)
for {
select {
case <-ctx.Done():
return
default:
n, from, err := conn.ReadFrom(buf)
if err != nil {
continue
}
var msg messages.Request
if err := msg.UnmarshalBinary(buf[:n]); err != nil {
continue
}
src, ok := netaddr.FromStdIP(from.(*net.UDPAddr).IP)
if !ok {
continue
}
if msg.ClientIP != src {
continue
}
c <- msg
}
}
}
func processRequest(req messages.Request) messages.Response {
switch req.Operation {
case messages.Map:
return processMapRequest(req)
default:
return messages.Response{
Operation: messages.Announce,
Result: messages.Success,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
}
}
}
// processMapRequest is a somewhat opinionated way to process Map requests
// May not be totally RFC compliant, TODO.
func processMapRequest(req messages.Request) messages.Response {
proto := req.OpInfo.GetProtocol()
iPort := req.OpInfo.GetInternalPort()
if req.Lifetime != 0 {
// We don't support protocols that aren't TCP/UDP/ALL
if proto != messages.TCP && proto != messages.UDP && proto != 0 {
return messages.Response{
Operation: messages.Map,
Result: messages.UnsuppProtocol,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
}
// Specific protocol and specific port
if proto != 0 && iPort != 0 {
// Create mapping TODO
createMapping()
return messages.Response{
Operation: messages.Map,
Result: messages.Success,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
}
// Specific protocol and all ports
if proto != 0 && iPort == 0 {
// Let's not support this mode just yet
return messages.Response{
Operation: messages.Map,
Result: messages.UnsuppProtocol,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
}
// All protocols and all ports
if proto == 0 && iPort == 0 {
// Let's not support this mode just yet
return messages.Response{
Operation: messages.Map,
Result: messages.UnsuppProtocol,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
}
// All protocols and specific port is a malformed request
return messages.Response{
Operation: messages.Map,
Result: messages.MalformedRequest,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
} else { // Delete a mapping
return messages.Response{
Operation: messages.Map,
Result: messages.Success,
Lifetime: 0,
Epoch: uint32(time.Since(startTime).Seconds()),
OpInfo: req.OpInfo,
}
}
}
type mapping struct{}
// TODO make this actually create a mapping
func createMapping() (mapping, error) {
return mapping{}, nil
}