net: remove allocation from UDPConn.WriteTo

Duplicate some code to avoid an interface.

name                  old time/op    new time/op    delta
WriteToReadFromUDP-8    6.38µs ±20%    5.59µs ±10%  -12.38%  (p=0.001 n=10+9)

name                  old alloc/op   new alloc/op   delta
WriteToReadFromUDP-8     64.0B ± 0%     32.0B ± 0%  -50.00%  (p=0.000 n=10+10)

name                  old allocs/op  new allocs/op  delta
WriteToReadFromUDP-8      2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=10+10)

Windows is temporarily stubbed out.

Updates #43451

Change-Id: Ied15ff92268c652cf445836e0446025eaeb60cc9
Reviewed-on: https://go-review.googlesource.com/c/go/+/331489
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Trust: Damien Neil <dneil@google.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

9 files changed, 220 insertions, 34 deletions

diff --git a/api/next.txt b/api/next.txt
index e69de29bb2..8d2ee73f79 100644
--- a/api/next.txt
+++ b/api/next.txt
@@ -0,0 +1,52 @@
+pkg syscall (darwin-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (darwin-amd64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (darwin-amd64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (darwin-amd64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-386), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-386), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-386-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-386-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-amd64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-amd64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-amd64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-arm), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-arm), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (freebsd-arm-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (freebsd-arm-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-386), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-386), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-386-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-386-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-amd64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-amd64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-amd64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-arm), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-arm), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (linux-arm-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (linux-arm-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-386), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-386), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-386-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-386-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-amd64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-amd64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-amd64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-arm), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-arm), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-arm-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-arm-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-arm64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-arm64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (netbsd-arm64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (netbsd-arm64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (openbsd-386), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (openbsd-386), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (openbsd-386-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (openbsd-386-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (openbsd-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (openbsd-amd64), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
+pkg syscall (openbsd-amd64-cgo), func SendtoInet4(int, []uint8, int, SockaddrInet4) error
+pkg syscall (openbsd-amd64-cgo), func SendtoInet6(int, []uint8, int, SockaddrInet6) error
diff --git a/src/internal/poll/fd_unix.go b/src/internal/poll/fd_unix.go
index 3b17cd22b0..51d15f6abc 100644
--- a/src/internal/poll/fd_unix.go
+++ b/src/internal/poll/fd_unix.go
@@ -327,6 +327,58 @@ func (fd *FD) Pwrite(p []byte, off int64) (int, error) {
 	}
 }
 
+// WriteToInet4 wraps the sendto network call for IPv4 addresses.
+func (fd *FD) WriteToInet4(p []byte, sa syscall.SockaddrInet4) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if err := fd.pd.prepareWrite(fd.isFile); err != nil {
+		return 0, err
+	}
+	for {
+		err := syscall.SendtoInet4(fd.Sysfd, p, 0, sa)
+		if err == syscall.EINTR {
+			continue
+		}
+		if err == syscall.EAGAIN && fd.pd.pollable() {
+			if err = fd.pd.waitWrite(fd.isFile); err == nil {
+				continue
+			}
+		}
+		if err != nil {
+			return 0, err
+		}
+		return len(p), nil
+	}
+}
+
+// WriteToInet6 wraps the sendto network call for IPv6 addresses.
+func (fd *FD) WriteToInet6(p []byte, sa syscall.SockaddrInet6) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if err := fd.pd.prepareWrite(fd.isFile); err != nil {
+		return 0, err
+	}
+	for {
+		err := syscall.SendtoInet6(fd.Sysfd, p, 0, sa)
+		if err == syscall.EINTR {
+			continue
+		}
+		if err == syscall.EAGAIN && fd.pd.pollable() {
+			if err = fd.pd.waitWrite(fd.isFile); err == nil {
+				continue
+			}
+		}
+		if err != nil {
+			return 0, err
+		}
+		return len(p), nil
+	}
+}
+
 // WriteTo wraps the sendto network call.
 func (fd *FD) WriteTo(p []byte, sa syscall.Sockaddr) (int, error) {
 	if err := fd.writeLock(); err != nil {
diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
index 4a5169527c..3dada32985 100644
--- a/src/internal/poll/fd_windows.go
+++ b/src/internal/poll/fd_windows.go
@@ -791,6 +791,16 @@ func (fd *FD) WriteTo(buf []byte, sa syscall.Sockaddr) (int, error) {
 	return ntotal, nil
 }
 
+// WriteTo wraps the sendto network call for IPv4.
+func (fd *FD) WriteToInet4(buf []byte, sa syscall.SockaddrInet4) (int, error) {
+	return fd.WriteTo(buf, &sa)
+}
+
+// WriteTo wraps the sendto network call for IPv6.
+func (fd *FD) WriteToInet6(buf []byte, sa syscall.SockaddrInet6) (int, error) {
+	return fd.WriteTo(buf, &sa)
+}
+
 // Call ConnectEx. This doesn't need any locking, since it is only
 // called when the descriptor is first created. This is here rather
 // than in the net package so that it can use fd.wop.
diff --git a/src/net/fd_posix.go b/src/net/fd_posix.go
index 4703ff33a1..a0675b2072 100644
--- a/src/net/fd_posix.go
+++ b/src/net/fd_posix.go
@@ -82,6 +82,18 @@ func (fd *netFD) writeTo(p []byte, sa syscall.Sockaddr) (n int, err error) {
 	return n, wrapSyscallError(writeToSyscallName, err)
 }
 
+func (fd *netFD) writeToInet4(p []byte, sa syscall.SockaddrInet4) (n int, err error) {
+	n, err = fd.pfd.WriteToInet4(p, sa)
+	runtime.KeepAlive(fd)
+	return n, wrapSyscallError(writeToSyscallName, err)
+}
+
+func (fd *netFD) writeToInet6(p []byte, sa syscall.SockaddrInet6) (n int, err error) {
+	n, err = fd.pfd.WriteToInet6(p, sa)
+	runtime.KeepAlive(fd)
+	return n, wrapSyscallError(writeToSyscallName, err)
+}
+
 func (fd *netFD) writeMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oobn int, err error) {
 	n, oobn, err = fd.pfd.WriteMsg(p, oob, sa)
 	runtime.KeepAlive(fd)
diff --git a/src/net/ipsock_posix.go b/src/net/ipsock_posix.go
index c51c227401..50003ac446 100644
--- a/src/net/ipsock_posix.go
+++ b/src/net/ipsock_posix.go
@@ -142,42 +142,58 @@ func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, soty
 	return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlFn)
 }
 
+func ipToSockaddrInet4(ip IP, port int) (syscall.SockaddrInet4, error) {
+	if len(ip) == 0 {
+		ip = IPv4zero
+	}
+	ip4 := ip.To4()
+	if ip4 == nil {
+		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
+	}
+	sa := syscall.SockaddrInet4{Port: port}
+	copy(sa.Addr[:], ip4)
+	return sa, nil
+}
+
+func ipToSockaddrInet6(ip IP, port int, zone string) (syscall.SockaddrInet6, error) {
+	// In general, an IP wildcard address, which is either
+	// "0.0.0.0" or "::", means the entire IP addressing
+	// space. For some historical reason, it is used to
+	// specify "any available address" on some operations
+	// of IP node.
+	//
+	// When the IP node supports IPv4-mapped IPv6 address,
+	// we allow a listener to listen to the wildcard
+	// address of both IP addressing spaces by specifying
+	// IPv6 wildcard address.
+	if len(ip) == 0 || ip.Equal(IPv4zero) {
+		ip = IPv6zero
+	}
+	// We accept any IPv6 address including IPv4-mapped
+	// IPv6 address.
+	ip6 := ip.To16()
+	if ip6 == nil {
+		return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
+	}
+	sa := syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
+	copy(sa.Addr[:], ip6)
+	return sa, nil
+}
+
 func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
 	switch family {
 	case syscall.AF_INET:
-		if len(ip) == 0 {
-			ip = IPv4zero
-		}
-		ip4 := ip.To4()
-		if ip4 == nil {
-			return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
+		sa, err := ipToSockaddrInet4(ip, port)
+		if err != nil {
+			return nil, err
 		}
-		sa := &syscall.SockaddrInet4{Port: port}
-		copy(sa.Addr[:], ip4)
-		return sa, nil
+		return &sa, nil
 	case syscall.AF_INET6:
-		// In general, an IP wildcard address, which is either
-		// "0.0.0.0" or "::", means the entire IP addressing
-		// space. For some historical reason, it is used to
-		// specify "any available address" on some operations
-		// of IP node.
-		//
-		// When the IP node supports IPv4-mapped IPv6 address,
-		// we allow a listener to listen to the wildcard
-		// address of both IP addressing spaces by specifying
-		// IPv6 wildcard address.
-		if len(ip) == 0 || ip.Equal(IPv4zero) {
-			ip = IPv6zero
-		}
-		// We accept any IPv6 address including IPv4-mapped
-		// IPv6 address.
-		ip6 := ip.To16()
-		if ip6 == nil {
-			return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
+		sa, err := ipToSockaddrInet6(ip, port, zone)
+		if err != nil {
+			return nil, err
 		}
-		sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
-		copy(sa.Addr[:], ip6)
-		return sa, nil
+		return &sa, nil
 	}
 	return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
 }
diff --git a/src/net/net_fake.go b/src/net/net_fake.go
index 74fc1da6fd..feb51968dd 100644
--- a/src/net/net_fake.go
+++ b/src/net/net_fake.go
@@ -276,6 +276,14 @@ func (fd *netFD) writeTo(p []byte, sa syscall.Sockaddr) (n int, err error) {
 	return 0, syscall.ENOSYS
 }
 
+func (fd *netFD) writeToInet4(p []byte, sa syscall.SockaddrInet4) (n int, err error) {
+	return 0, syscall.ENOSYS
+}
+
+func (fd *netFD) writeToInet6(p []byte, sa syscall.SockaddrInet6) (n int, err error) {
+	return 0, syscall.ENOSYS
+}
+
 func (fd *netFD) writeMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oobn int, err error) {
 	return 0, 0, syscall.ENOSYS
 }
diff --git a/src/net/udpsock_posix.go b/src/net/udpsock_posix.go
index 96fb373ce7..b71be09217 100644
--- a/src/net/udpsock_posix.go
+++ b/src/net/udpsock_posix.go
@@ -76,11 +76,23 @@ func (c *UDPConn) writeTo(b []byte, addr *UDPAddr) (int, error) {
 	if addr == nil {
 		return 0, errMissingAddress
 	}
-	sa, err := addr.sockaddr(c.fd.family)
-	if err != nil {
-		return 0, err
+
+	switch c.fd.family {
+	case syscall.AF_INET:
+		sa, err := ipToSockaddrInet4(addr.IP, addr.Port)
+		if err != nil {
+			return 0, err
+		}
+		return c.fd.writeToInet4(b, sa)
+	case syscall.AF_INET6:
+		sa, err := ipToSockaddrInet6(addr.IP, addr.Port, addr.Zone)
+		if err != nil {
+			return 0, err
+		}
+		return c.fd.writeToInet6(b, sa)
+	default:
+		return 0, &AddrError{Err: "invalid address family", Addr: addr.IP.String()}
 	}
-	return c.fd.writeTo(b, sa)
 }
 
 func (c *UDPConn) writeMsg(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
diff --git a/src/syscall/net_js.go b/src/syscall/net_js.go
index ed462025bb..17799148bd 100644
--- a/src/syscall/net_js.go
+++ b/src/syscall/net_js.go
@@ -96,6 +96,14 @@ func Sendto(fd int, p []byte, flags int, to Sockaddr) error {
 	return ENOSYS
 }
 
+func SendtoInet4(fd int, p []byte, flags int, to SockaddrInet4) error {
+	return ENOSYS
+}
+
+func SendtoInet6(fd int, p []byte, flags int, to SockaddrInet6) error {
+	return ENOSYS
+}
+
 func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn, recvflags int, from Sockaddr, err error) {
 	return 0, 0, 0, nil, ENOSYS
 }
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index 5b405b99b4..60aeae14de 100644
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -292,6 +292,22 @@ func Recvfrom(fd int, p []byte, flags int) (n int, from Sockaddr, err error) {
 	return
 }
 
+func SendtoInet4(fd int, p []byte, flags int, to SockaddrInet4) (err error) {
+	ptr, n, err := to.sockaddr()
+	if err != nil {
+		return err
+	}
+	return sendto(fd, p, flags, ptr, n)
+}
+
+func SendtoInet6(fd int, p []byte, flags int, to SockaddrInet6) (err error) {
+	ptr, n, err := to.sockaddr()
+	if err != nil {
+		return err
+	}
+	return sendto(fd, p, flags, ptr, n)
+}
+
 func Sendto(fd int, p []byte, flags int, to Sockaddr) (err error) {
 	ptr, n, err := to.sockaddr()
 	if err != nil {