syscall, net: use sendfile on Solaris

Updates #5847.

Change-Id: Ic93f2e5f9a6aa3bd49cf75b16474ec5e897d17e1
Reviewed-on: https://go-review.googlesource.com/7940Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/net/sendfile_solaris.go

+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// sendFile copies the contents of r to c using the sendfile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
+	// Solaris uses 0 as the "until EOF" value. If you pass in more bytes than the
+	// file contains, it will loop back to the beginning ad nauseam until it's sent
+	// exactly the number of bytes told to. As such, we need to know exactly how many
+	// bytes to send.
+	var remain int64 = 0
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		remain, r = lr.N, lr.R
+		if remain <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if remain == 0 {
+		fi, err := f.Stat()
+		if err != nil {
+			return 0, err, false
+		}
+
+		remain = fi.Size()
+	}
+
+	// The other quirk with Solaris's sendfile implementation is that it doesn't
+	// use the current position of the file -- if you pass it offset 0, it starts
+	// from offset 0. There's no way to tell it "start from current position", so
+	// we have to manage that explicitly.
+	pos, err := f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return 0, err, false
+	}
+
+	if err := c.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer c.writeUnlock()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		pos1 := pos
+		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
+		if n > 0 {
+			pos += int64(n)
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN {
+			if err1 = c.pd.WaitWrite(); err1 == nil {
+				continue
+			}
+		}
+		if err1 == syscall.EINTR {
+			continue
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = err1
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}

src/net/sendfile_stub.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin nacl netbsd openbsd solaris
+// +build darwin nacl netbsd openbsd
 
 package net
 

src/syscall/syscall_solaris.go

@@ -473,6 +473,7 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
 //sys	Rename(from string, to string) (err error)
 //sys	Rmdir(path string) (err error)
 //sys	Seek(fd int, offset int64, whence int) (newoffset int64, err error) = lseek
+//sys	sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) = libsendfile.sendfile
 //sysnb	Setegid(egid int) (err error)
 //sysnb	Seteuid(euid int) (err error)
 //sysnb	Setgid(gid int) (err error)

src/syscall/syscall_solaris_amd64.go

@@ -30,8 +30,3 @@ func (iov *Iovec) SetLen(length int) {
 func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }
-
-func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
-	// TODO(aram): implement this, see issue 5847.
-	panic("unimplemented")
-}

src/syscall/zsyscall_solaris_amd64.go

@@ -51,6 +51,7 @@ import "unsafe"
 //go:cgo_import_dynamic libc_Rename rename "libc.so"
 //go:cgo_import_dynamic libc_Rmdir rmdir "libc.so"
 //go:cgo_import_dynamic libc_lseek lseek "libc.so"
+//go:cgo_import_dynamic libc_sendfile sendfile "libsendfile.so"
 //go:cgo_import_dynamic libc_Setegid setegid "libc.so"
 //go:cgo_import_dynamic libc_Seteuid seteuid "libc.so"
 //go:cgo_import_dynamic libc_Setgid setgid "libc.so"
@@ -132,6 +133,7 @@ import "unsafe"
 //go:linkname libc_Rename libc_Rename
 //go:linkname libc_Rmdir libc_Rmdir
 //go:linkname libc_lseek libc_lseek
+//go:linkname libc_sendfile libc_sendfile
 //go:linkname libc_Setegid libc_Setegid
 //go:linkname libc_Seteuid libc_Seteuid
 //go:linkname libc_Setgid libc_Setgid
@@ -216,6 +218,7 @@ var (
 	libc_Rename,
 	libc_Rmdir,
 	libc_lseek,
+	libc_sendfile,
 	libc_Setegid,
 	libc_Seteuid,
 	libc_Setgid,
@@ -742,6 +745,15 @@ func Seek(fd int, offset int64, whence int) (newoffset int64, err error) {
 	return
 }
 
+func sendfile(outfd int, infd int, offset *int64, count int) (written int, err error) {
+	r0, _, e1 := sysvicall6(uintptr(unsafe.Pointer(&libc_sendfile)), 4, uintptr(outfd), uintptr(infd), uintptr(unsafe.Pointer(offset)), uintptr(count), 0, 0)
+	written = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func Setegid(egid int) (err error) {
 	_, _, e1 := rawSysvicall6(uintptr(unsafe.Pointer(&libc_Setegid)), 1, uintptr(egid), 0, 0, 0, 0, 0)
 	if e1 != 0 {