go.net/ipv4: simplify ancillary helpers
This CL reduces unnecessary allocations in ancillary helper
functions. Also clarifies documentation on ControlMessage,
ControlFlags.
benchmark old allocs new allocs delta
BenchmarkReadWriteNetUDP-2 6 6 0.00%
BenchmarkReadWriteIPv4UDP-2 17 15 -11.76%
R=dave
CC=golang-dev
https://golang.org/cl/9232050
diff --git a/ipv4/control_linux.go b/ipv4/control_linux.go
index cf2dcf0..fa7630f 100644
--- a/ipv4/control_linux.go
+++ b/ipv4/control_linux.go
@@ -5,7 +5,6 @@
package ipv4
import (
- "net"
"os"
"syscall"
"unsafe"
@@ -16,8 +15,8 @@
const pktinfo = FlagSrc | FlagDst | FlagInterface
func setControlMessage(fd int, opt *rawOpt, cf ControlFlags, on bool) error {
- opt.lock()
- defer opt.unlock()
+ opt.Lock()
+ defer opt.Unlock()
if cf&FlagTTL != 0 {
if err := setIPv4ReceiveTTL(fd, on); err != nil {
return err
@@ -42,35 +41,43 @@
}
func newControlMessage(opt *rawOpt) (oob []byte) {
- opt.lock()
- defer opt.unlock()
+ opt.Lock()
+ defer opt.Unlock()
+ l, off := 0, 0
if opt.isset(FlagTTL) {
- b := make([]byte, syscall.CmsgSpace(1))
- cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
- cmsg.Level = ianaProtocolIP
- cmsg.Type = syscall.IP_RECVTTL
- cmsg.SetLen(syscall.CmsgLen(1))
- oob = append(oob, b...)
+ l += syscall.CmsgSpace(1)
}
if opt.isset(pktinfo) {
- b := make([]byte, syscall.CmsgSpace(syscall.SizeofInet4Pktinfo))
- cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
- cmsg.Level = ianaProtocolIP
- cmsg.Type = syscall.IP_PKTINFO
- cmsg.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
- oob = append(oob, b...)
+ l += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
+ }
+ if l > 0 {
+ oob = make([]byte, l)
+ if opt.isset(FlagTTL) {
+ m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
+ m.Level = ianaProtocolIP
+ m.Type = syscall.IP_RECVTTL
+ m.SetLen(syscall.CmsgLen(1))
+ off += syscall.CmsgSpace(1)
+ }
+ if opt.isset(pktinfo) {
+ m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
+ m.Level = ianaProtocolIP
+ m.Type = syscall.IP_PKTINFO
+ m.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
+ off += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
+ }
}
return
}
func parseControlMessage(b []byte) (*ControlMessage, error) {
+ if len(b) == 0 {
+ return nil, nil
+ }
cmsgs, err := syscall.ParseSocketControlMessage(b)
if err != nil {
return nil, os.NewSyscallError("parse socket control message", err)
}
- if len(b) == 0 {
- return nil, nil
- }
cm := &ControlMessage{}
for _, m := range cmsgs {
if m.Header.Level != ianaProtocolIP {
@@ -82,7 +89,7 @@
case syscall.IP_PKTINFO:
pi := (*syscall.Inet4Pktinfo)(unsafe.Pointer(&m.Data[0]))
cm.IfIndex = int(pi.Ifindex)
- cm.Dst = net.IPv4(pi.Addr[0], pi.Addr[1], pi.Addr[2], pi.Addr[3])
+ cm.Dst = pi.Addr[:]
}
}
return cm, nil
@@ -92,25 +99,28 @@
if cm == nil {
return
}
- pi := &syscall.Inet4Pktinfo{}
+ l, off := 0, 0
pion := false
- if ip := cm.Src.To4(); ip != nil {
- copy(pi.Spec_dst[:], ip[:net.IPv4len])
+ if cm.Src.To4() != nil || cm.IfIndex != 0 {
pion = true
+ l += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
}
- if cm.IfIndex != 0 {
- pi.Ifindex = int32(cm.IfIndex)
- pion = true
- }
- if pion {
- b := make([]byte, syscall.CmsgSpace(syscall.SizeofInet4Pktinfo))
- cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
- cmsg.Level = ianaProtocolIP
- cmsg.Type = syscall.IP_PKTINFO
- cmsg.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
- data := b[syscall.CmsgLen(0):]
- copy(data[:syscall.SizeofInet4Pktinfo], (*[syscall.SizeofInet4Pktinfo]byte)(unsafe.Pointer(pi))[:syscall.SizeofInet4Pktinfo])
- oob = append(oob, b...)
+ if l > 0 {
+ oob = make([]byte, l)
+ if pion {
+ m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
+ m.Level = ianaProtocolIP
+ m.Type = syscall.IP_PKTINFO
+ m.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
+ pi := (*syscall.Inet4Pktinfo)(unsafe.Pointer(&oob[off+syscall.CmsgLen(0)]))
+ if ip := cm.Src.To4(); ip != nil {
+ copy(pi.Addr[:], ip)
+ }
+ if cm.IfIndex != 0 {
+ pi.Ifindex = int32(cm.IfIndex)
+ }
+ off += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
+ }
}
return
}
