syscall: add SendmsgN for BSD variants, Linux and Solaris

SendmsgN is an alternate version Sendmsg that also returns
the number of bytes transferred, instead of just the error.

Update #7645

LGTM=aram, iant
R=iant, aram, bradfitz
CC=golang-codereviews
https://golang.org/cl/81210043

src/pkg/syscall/syscall_bsd.go

@@ -389,15 +389,20 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
 	return
 }
 
-//sys	sendmsg(s int, msg *Msghdr, flags int) (err error)
+//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 
 func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
+	_, err = SendmsgN(fd, p, oob, to, flags)
+	return
+}
+
+func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
 	var ptr unsafe.Pointer
 	var salen _Socklen
 	if to != nil {
 		ptr, salen, err = to.sockaddr()
 		if err != nil {
-			return
+			return 0, err
 		}
 	}
 	var msg Msghdr
@@ -420,10 +425,13 @@ func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
 	}
 	msg.Iov = &iov
 	msg.Iovlen = 1
-	if err = sendmsg(fd, &msg, flags); err != nil {
-		return
+	if n, err = sendmsg(fd, &msg, flags); err != nil {
+		return 0, err
 	}
-	return
+	if len(oob) > 0 && len(p) == 0 {
+		n = 0
+	}
+	return n, nil
 }
 
 //sys	kevent(kq int, change unsafe.Pointer, nchange int, event unsafe.Pointer, nevent int, timeout *Timespec) (n int, err error)

src/pkg/syscall/syscall_linux.go

@@ -527,13 +527,18 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
 }
 
 func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
+	_, err = SendmsgN(fd, p, oob, to, flags)
+	return
+}
+
+func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
 	var ptr unsafe.Pointer
 	var salen _Socklen
 	if to != nil {
 		var err error
 		ptr, salen, err = to.sockaddr()
 		if err != nil {
-			return err
+			return 0, err
 		}
 	}
 	var msg Msghdr
@@ -556,10 +561,13 @@ func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
 	}
 	msg.Iov = &iov
 	msg.Iovlen = 1
-	if err = sendmsg(fd, &msg, flags); err != nil {
-		return
+	if n, err = sendmsg(fd, &msg, flags); err != nil {
+		return 0, err
 	}
-	return
+	if len(oob) > 0 && len(p) == 0 {
+		n = 0
+	}
+	return n, nil
 }
 
 // BindToDevice binds the socket associated with fd to device.

src/pkg/syscall/syscall_linux_386.go

@@ -284,8 +284,8 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 	return
 }
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, e := socketcall(_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags), 0, 0, 0)
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	n, e := socketcall(_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags), 0, 0, 0)
 	if e != 0 {
 		err = e
 	}

src/pkg/syscall/syscall_linux_amd64.go

@@ -53,7 +53,7 @@ package syscall
 //sys	recvfrom(fd int, p []byte, flags int, from *RawSockaddrAny, fromlen *_Socklen) (n int, err error)
 //sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
 //sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
-//sys	sendmsg(s int, msg *Msghdr, flags int) (err error)
+//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 //sys	mmap(addr uintptr, length uintptr, prot int, flags int, fd int, offset int64) (xaddr uintptr, err error)
 
 func Getpagesize() int { return 4096 }

src/pkg/syscall/syscall_linux_arm.go

@@ -42,7 +42,7 @@ func Seek(fd int, offset int64, whence int) (newoffset int64, err error)
 //sys	sendto(s int, buf []byte, flags int, to unsafe.Pointer, addrlen _Socklen) (err error)
 //sysnb	socketpair(domain int, typ int, flags int, fd *[2]int32) (err error)
 //sys	recvmsg(s int, msg *Msghdr, flags int) (n int, err error)
-//sys	sendmsg(s int, msg *Msghdr, flags int) (err error)
+//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error)
 
 // 64-bit file system and 32-bit uid calls
 // (16-bit uid calls are not always supported in newer kernels)

src/pkg/syscall/syscall_solaris.go

@@ -380,14 +380,19 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
 	return
 }
 
-//sys	sendmsg(s int, msg *Msghdr, flags int) (err error) = libsocket.sendmsg
 func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
+	_, err = SendmsgN(fd, p, oob, to, flags)
+	return
+}
+
+//sys	sendmsg(s int, msg *Msghdr, flags int) (n int, err error) = libsocket.sendmsg
+func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error) {
 	var ptr unsafe.Pointer
 	var salen _Socklen
 	if to != nil {
 		ptr, salen, err = to.sockaddr()
 		if err != nil {
-			return err
+			return 0, err
 		}
 	}
 	var msg Msghdr
@@ -409,7 +414,13 @@ func Sendmsg(fd int, p, oob []byte, to Sockaddr, flags int) (err error) {
 	}
 	msg.Iov = &iov
 	msg.Iovlen = 1
-	return sendmsg(fd, &msg, flags)
+	if n, err = sendmsg(fd, &msg, flags); err != nil {
+		return 0, err
+	}
+	if len(oob) > 0 && len(p) == 0 {
+		n = 0
+	}
+	return n, nil
 }
 
 /*

src/pkg/syscall/zsyscall_darwin_386.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_darwin_amd64.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_dragonfly_386.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_dragonfly_amd64.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_freebsd_386.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_freebsd_amd64.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_freebsd_arm.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_linux_amd64.go

@@ -1909,8 +1909,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_linux_arm.go

@@ -1529,8 +1529,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_netbsd_386.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_netbsd_amd64.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_netbsd_arm.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_openbsd_386.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_openbsd_amd64.go

@@ -185,8 +185,9 @@ func recvmsg(s int, msg *Msghdr, flags int) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := Syscall(SYS_SENDMSG, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags))
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}

src/pkg/syscall/zsyscall_solaris_amd64.go

@@ -126,8 +126,9 @@ func accept(s int, rsa *RawSockaddrAny, addrlen *_Socklen) (fd int, err error) {
 	return
 }
 
-func sendmsg(s int, msg *Msghdr, flags int) (err error) {
-	_, _, e1 := sysvicall6(procsendmsg.Addr(), 3, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags), 0, 0, 0)
+func sendmsg(s int, msg *Msghdr, flags int) (n int, err error) {
+	r0, _, e1 := sysvicall6(procsendmsg.Addr(), 3, uintptr(s), uintptr(unsafe.Pointer(msg)), uintptr(flags), 0, 0, 0)
+	n = int(r0)
 	if e1 != 0 {
 		err = e1
 	}