From 433ba582f7c72636066ec92679a325b7ee15297c Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Mon, 1 Nov 2021 13:23:39 -0700
Subject: [PATCH] net: optimize WriteToUDPAddrPort
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See the recent change optimizing WriteMsgUDPAddrPort
for an explanation of why this change includes copy/paste/modify
instead of implementing WriteToUDP using WriteToUDPAddrPort.

name                          old time/op    new time/op    delta
WriteToReadFromUDPAddrPort-8    5.02µs ± 3%    4.71µs ± 2%   -6.31%  (p=0.000 n=15+14)

name                          old alloc/op   new alloc/op   delta
WriteToReadFromUDPAddrPort-8     68.0B ± 0%      4.0B ± 0%  -94.12%  (p=0.000 n=15+15)

name                          old allocs/op  new allocs/op  delta
WriteToReadFromUDPAddrPort-8      3.00 ± 0%      1.00 ± 0%  -66.67%  (p=0.000 n=15+15)

Change-Id: I301715e774de07eb6ccb4e329ccf2e554609abc1
Reviewed-on: https://go-review.googlesource.com/c/go/+/360599
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---
 src/net/udpsock.go       | 13 ++++++++-----
 src/net/udpsock_plan9.go |  4 ++++
 src/net/udpsock_posix.go | 26 ++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/src/net/udpsock.go b/src/net/udpsock.go
index 0d563fd4f5..a829789a1b 100644
--- a/src/net/udpsock.go
+++ b/src/net/udpsock.go
@@ -207,11 +207,14 @@ func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
 
 // WriteToUDPAddrPort acts like WriteTo but takes a netip.AddrPort.
 func (c *UDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error) {
-	// TODO(bradfitz): make this efficient, making the internal net package
-	// type throughout be netip.Addr and only converting to the net.IP slice
-	// version at the edge. But for now (2021-10-20), this is a wrapper around
-	// the old way.
-	return c.WriteToUDP(b, UDPAddrFromAddrPort(addr))
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	n, err := c.writeToAddrPort(b, addr)
+	if err != nil {
+		err = &OpError{Op: "write", Net: c.fd.net, Source: c.fd.laddr, Addr: addrPortUDPAddr{addr}, Err: err}
+	}
+	return n, err
 }
 
 // WriteTo implements the PacketConn WriteTo method.
diff --git a/src/net/udpsock_plan9.go b/src/net/udpsock_plan9.go
index ac5afa2281..dfb81a8d0c 100644
--- a/src/net/udpsock_plan9.go
+++ b/src/net/udpsock_plan9.go
@@ -53,6 +53,10 @@ func (c *UDPConn) writeTo(b []byte, addr *UDPAddr) (int, error) {
 	return len(b), nil
 }
 
+func (c *UDPConn) writeToAddrPort(b []byte, addr netip.AddrPort) (int, error) {
+	return c.writeTo(b, UDPAddrFromAddrPort(addr)) // TODO: optimize instead of allocating
+}
+
 func (c *UDPConn) writeMsg(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
 	return 0, 0, syscall.EPLAN9
 }
diff --git a/src/net/udpsock_posix.go b/src/net/udpsock_posix.go
index 646687d148..718d11e60f 100644
--- a/src/net/udpsock_posix.go
+++ b/src/net/udpsock_posix.go
@@ -109,6 +109,32 @@ func (c *UDPConn) writeTo(b []byte, addr *UDPAddr) (int, error) {
 	}
 }
 
+func (c *UDPConn) writeToAddrPort(b []byte, addr netip.AddrPort) (int, error) {
+	if c.fd.isConnected {
+		return 0, ErrWriteToConnected
+	}
+	if !addr.IsValid() {
+		return 0, errMissingAddress
+	}
+
+	switch c.fd.family {
+	case syscall.AF_INET:
+		sa, err := addrPortToSockaddrInet4(addr)
+		if err != nil {
+			return 0, err
+		}
+		return c.fd.writeToInet4(b, sa)
+	case syscall.AF_INET6:
+		sa, err := addrPortToSockaddrInet6(addr)
+		if err != nil {
+			return 0, err
+		}
+		return c.fd.writeToInet6(b, sa)
+	default:
+		return 0, &AddrError{Err: "invalid address family", Addr: addr.Addr().String()}
+	}
+}
+
 func (c *UDPConn) writeMsg(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
 	if c.fd.isConnected && addr != nil {
 		return 0, 0, ErrWriteToConnected