syscall: add Accept4 for freebsd

Update #7186
Update #7428

LGTM=r, bradfitz
R=golang-codereviews, rsc, minux.ma, r, bradfitz
CC=golang-codereviews
https://golang.org/cl/68880043

src/pkg/syscall/syscall_freebsd.go

@@ -103,6 +103,24 @@ func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
 	return setsockopt(fd, level, opt, unsafe.Pointer(mreq), unsafe.Sizeof(*mreq))
 }
 
+func Accept4(fd, flags int) (nfd int, sa Sockaddr, err error) {
+	var rsa RawSockaddrAny
+	var len _Socklen = SizeofSockaddrAny
+	nfd, err = accept4(fd, &rsa, &len, flags)
+	if err != nil {
+		return
+	}
+	if len > SizeofSockaddrAny {
+		panic("RawSockaddrAny too small")
+	}
+	sa, err = anyToSockaddr(&rsa)
+	if err != nil {
+		Close(nfd)
+		nfd = 0
+	}
+	return
+}
+
 /*
  * Exposed directly
  */
@@ -191,6 +209,7 @@ func SetsockoptIPMreqn(fd, level, opt int, mreq *IPMreqn) (err error) {
 //sys   munmap(addr uintptr, length uintptr) (err error)
 //sys	readlen(fd int, buf *byte, nbuf int) (n int, err error) = SYS_READ
 //sys	writelen(fd int, buf *byte, nbuf int) (n int, err error) = SYS_WRITE
+//sys	accept4(fd int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (nfd int, err error)
 
 /*
  * Unimplemented

src/pkg/syscall/zsyscall_freebsd_386.go

@@ -1301,3 +1301,14 @@ func writelen(fd int, buf *byte, nbuf int) (n int, err error) {
 	}
 	return
 }
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func accept4(fd int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (nfd int, err error) {
+	r0, _, e1 := Syscall6(SYS_ACCEPT4, uintptr(fd), uintptr(unsafe.Pointer(rsa)), uintptr(unsafe.Pointer(addrlen)), uintptr(flags), 0, 0)
+	nfd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

src/pkg/syscall/zsyscall_freebsd_amd64.go

@@ -1301,3 +1301,14 @@ func writelen(fd int, buf *byte, nbuf int) (n int, err error) {
 	}
 	return
 }
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func accept4(fd int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (nfd int, err error) {
+	r0, _, e1 := Syscall6(SYS_ACCEPT4, uintptr(fd), uintptr(unsafe.Pointer(rsa)), uintptr(unsafe.Pointer(addrlen)), uintptr(flags), 0, 0)
+	nfd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}

src/pkg/syscall/zsyscall_freebsd_arm.go

@@ -1301,3 +1301,14 @@ func writelen(fd int, buf *byte, nbuf int) (n int, err error) {
 	}
 	return
 }
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
+func accept4(fd int, rsa *RawSockaddrAny, addrlen *_Socklen, flags int) (nfd int, err error) {
+	r0, _, e1 := Syscall6(SYS_ACCEPT4, uintptr(fd), uintptr(unsafe.Pointer(rsa)), uintptr(unsafe.Pointer(addrlen)), uintptr(flags), 0, 0)
+	nfd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}