forked from google/cloudprober
/
udp.go
136 lines (125 loc) · 3.73 KB
/
udp.go
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// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/*
Package udp implements a UDP server. It listens on a
given port and echos whatever it receives. This is used for the UDP probe.
*/
package udp
import (
"context"
"io"
"net"
"github.com/google/cloudprober/logger"
"github.com/google/cloudprober/metrics"
configpb "github.com/google/cloudprober/servers/udp/proto"
)
const (
// recv socket buffer size - we want to use a large value here, preferably
// the maximum allowed by the OS. 425984 is the max value in
// Container-Optimized OS version 9592.90.0.
readBufSize = 425984
)
// Server implements a basic UDP server.
type Server struct {
c *configpb.ServerConf
conn *net.UDPConn
l *logger.Logger
}
// New returns an UDP server.
func New(initCtx context.Context, c *configpb.ServerConf, l *logger.Logger) (*Server, error) {
conn, err := Listen(int(c.GetPort()), l)
if err != nil {
return nil, err
}
go func() {
<-initCtx.Done()
conn.Close()
}()
return &Server{
c: c,
conn: conn,
l: l,
}, nil
}
// Listen opens a UDP socket on the given port. It also attempts to set recv
// buffer to a large value so that we can have many outstanding UDP messages.
// Listen is exported only because it's used by udp probe tests.
func Listen(port int, l *logger.Logger) (*net.UDPConn, error) {
conn, err := net.ListenUDP("udp", &net.UDPAddr{Port: port})
if err != nil {
return nil, err
}
if err = conn.SetReadBuffer(readBufSize); err != nil {
// Non-fatal error if we are not able to set read socket buffer.
l.Errorf("Error setting UDP socket %v read buffer to %d: %s. Continuing...",
conn.LocalAddr(), readBufSize, err)
}
return conn, nil
}
// Start starts the UDP server. It returns only when context is canceled.
func (s *Server) Start(ctx context.Context, dataChan chan<- *metrics.EventMetrics) error {
switch s.c.GetType() {
case configpb.ServerConf_ECHO:
s.l.Infof("Starting UDP ECHO server on port %d", int(s.c.GetPort()))
for {
select {
case <-ctx.Done():
return s.conn.Close()
default:
}
readAndEcho(s.conn, s.l)
}
case configpb.ServerConf_DISCARD:
s.l.Infof("Starting UDP DISCARD server on port %d", int(s.c.GetPort()))
for {
select {
case <-ctx.Done():
return s.conn.Close()
default:
}
readAndDiscard(s.conn, s.l)
}
}
return nil
}
func readAndEcho(conn *net.UDPConn, l *logger.Logger) {
// TODO(manugarg): We read and echo back only 4098 bytes. We should look at raising this
// limit or making it configurable. Also of note, ReadFromUDP reads a single UDP datagram
// (up to the max size of 64K-sizeof(UDPHdr)) and discards the rest.
buf := make([]byte, 4098)
len, addr, err := conn.ReadFromUDP(buf)
if err != nil {
l.Errorf("ReadFromUDP: %v", err)
return
}
n, err := conn.WriteToUDP(buf[:len], addr)
if err == io.EOF {
return
}
if err != nil {
l.Errorf("WriteToUDP: %v", err)
return
}
if n < len {
l.Warningf("Reply truncated! Got %v bytes but only sent %v bytes", len, n)
}
}
// listenAndServeDiscard launches an UDP discard server listening on port.
func readAndDiscard(conn *net.UDPConn, l *logger.Logger) {
buf := make([]byte, 4098)
_, _, err := conn.ReadFromUDP(buf)
if err != nil {
l.Errorf("ReadFromUDP: %v", err)
}
}