syscall: add Accept4 and SOCK_{CLOEXEC,NONBLOCK} on dragonfly

This change just picks a few constants from DragonfFly BSD 4.6 kernel
and doesn't synchronize all the existing constants with the latest
DragonFly BSD kernels.

Updates #14222.

Change-Id: Ie107a8bee1a09393b3b42b6f82489532f5d13290
Reviewed-on: https://go-review.googlesource.com/40894Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/syscall/syscall_dragonfly.go

@@ -92,6 +92,24 @@ func Pwrite(fd int, p []byte, offset int64) (n int, err error) {
 	return extpwrite(fd, p, 0, offset)
 }
 
+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
+}
+
 func Getfsstat(buf []Statfs_t, flags int) (n int, err error) {
 	var _p0 unsafe.Pointer
 	var bufsize uintptr
@@ -192,6 +210,7 @@ func Getfsstat(buf []Statfs_t, flags int) (n int, 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/syscall/zerrors_dragonfly_amd64.go

@@ -1094,8 +1094,10 @@ const (
 	SIOCSLIFPHYADDR                   = 0x8118694a
 	SIOCSLOWAT                        = 0x80047302
 	SIOCSPGRP                         = 0x80047308
+	SOCK_CLOEXEC                      = 0x10000000
 	SOCK_DGRAM                        = 0x2
 	SOCK_MAXADDRLEN                   = 0xff
+	SOCK_NONBLOCK                     = 0x20000000
 	SOCK_RAW                          = 0x3
 	SOCK_RDM                          = 0x4
 	SOCK_SEQPACKET                    = 0x5

src/syscall/zsyscall_dragonfly_amd64.go

@@ -1287,3 +1287,14 @@ 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 = errnoErr(e1)
+	}
+	return
+}

src/syscall/zsysnum_dragonfly_amd64.go

@@ -301,4 +301,5 @@ const (
 	SYS_LPATHCONF              = 533 // { int lpathconf(char *path, int name); }
 	SYS_VMM_GUEST_CTL          = 534 // { int vmm_guest_ctl(int op, struct vmm_guest_options *options); }
 	SYS_VMM_GUEST_SYNC_ADDR    = 535 // { int vmm_guest_sync_addr(long *dstaddr, long *srcaddr); }
+	SYS_ACCEPT4                = 541 // { int accept4(int s, caddr_t name, int *anamelen, int flags); }
 )