selftests/bpf: fix compilation error for flow_dissector.c

When building the tools/testing/selftest/bpf subdirectory,
(running both a local directory "make" and a
"make -C tools/testing/selftests/bpf") I keep hitting the
following compilation error:

prog_tests/flow_dissector.c: In function ‘create_tap’:
prog_tests/flow_dissector.c:150:38: error: ‘IFF_NAPI’ undeclared (first
use in this function)
   .ifr_flags = IFF_TAP | IFF_NO_PI | IFF_NAPI | IFF_NAPI_FRAGS,
                                      ^
prog_tests/flow_dissector.c:150:38: note: each undeclared identifier is
reported only once for each function it appears in
prog_tests/flow_dissector.c:150:49: error: ‘IFF_NAPI_FRAGS’ undeclared

Adding include/uapi/linux/if_tun.h to tools/include/uapi/linux
resolves the problem and ensures the compilation of the file
does not depend on having up-to-date kernel headers locally.
Signed-off-by: NAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/include/uapi/linux/if_tun.h

+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ *  Universal TUN/TAP device driver.
+ *  Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *  GNU General Public License for more details.
+ */
+
+#ifndef _UAPI__IF_TUN_H
+#define _UAPI__IF_TUN_H
+
+#include <linux/types.h>
+#include <linux/if_ether.h>
+#include <linux/filter.h>
+
+/* Read queue size */
+#define TUN_READQ_SIZE	500
+/* TUN device type flags: deprecated. Use IFF_TUN/IFF_TAP instead. */
+#define TUN_TUN_DEV 	IFF_TUN
+#define TUN_TAP_DEV	IFF_TAP
+#define TUN_TYPE_MASK   0x000f
+
+/* Ioctl defines */
+#define TUNSETNOCSUM  _IOW('T', 200, int) 
+#define TUNSETDEBUG   _IOW('T', 201, int) 
+#define TUNSETIFF     _IOW('T', 202, int) 
+#define TUNSETPERSIST _IOW('T', 203, int) 
+#define TUNSETOWNER   _IOW('T', 204, int)
+#define TUNSETLINK    _IOW('T', 205, int)
+#define TUNSETGROUP   _IOW('T', 206, int)
+#define TUNGETFEATURES _IOR('T', 207, unsigned int)
+#define TUNSETOFFLOAD  _IOW('T', 208, unsigned int)
+#define TUNSETTXFILTER _IOW('T', 209, unsigned int)
+#define TUNGETIFF      _IOR('T', 210, unsigned int)
+#define TUNGETSNDBUF   _IOR('T', 211, int)
+#define TUNSETSNDBUF   _IOW('T', 212, int)
+#define TUNATTACHFILTER _IOW('T', 213, struct sock_fprog)
+#define TUNDETACHFILTER _IOW('T', 214, struct sock_fprog)
+#define TUNGETVNETHDRSZ _IOR('T', 215, int)
+#define TUNSETVNETHDRSZ _IOW('T', 216, int)
+#define TUNSETQUEUE  _IOW('T', 217, int)
+#define TUNSETIFINDEX	_IOW('T', 218, unsigned int)
+#define TUNGETFILTER _IOR('T', 219, struct sock_fprog)
+#define TUNSETVNETLE _IOW('T', 220, int)
+#define TUNGETVNETLE _IOR('T', 221, int)
+/* The TUNSETVNETBE and TUNGETVNETBE ioctls are for cross-endian support on
+ * little-endian hosts. Not all kernel configurations support them, but all
+ * configurations that support SET also support GET.
+ */
+#define TUNSETVNETBE _IOW('T', 222, int)
+#define TUNGETVNETBE _IOR('T', 223, int)
+#define TUNSETSTEERINGEBPF _IOR('T', 224, int)
+#define TUNSETFILTEREBPF _IOR('T', 225, int)
+#define TUNSETCARRIER _IOW('T', 226, int)
+#define TUNGETDEVNETNS _IO('T', 227)
+
+/* TUNSETIFF ifr flags */
+#define IFF_TUN		0x0001
+#define IFF_TAP		0x0002
+#define IFF_NAPI	0x0010
+#define IFF_NAPI_FRAGS	0x0020
+#define IFF_NO_PI	0x1000
+/* This flag has no real effect */
+#define IFF_ONE_QUEUE	0x2000
+#define IFF_VNET_HDR	0x4000
+#define IFF_TUN_EXCL	0x8000
+#define IFF_MULTI_QUEUE 0x0100
+#define IFF_ATTACH_QUEUE 0x0200
+#define IFF_DETACH_QUEUE 0x0400
+/* read-only flag */
+#define IFF_PERSIST	0x0800
+#define IFF_NOFILTER	0x1000
+
+/* Socket options */
+#define TUN_TX_TIMESTAMP 1
+
+/* Features for GSO (TUNSETOFFLOAD). */
+#define TUN_F_CSUM	0x01	/* You can hand me unchecksummed packets. */
+#define TUN_F_TSO4	0x02	/* I can handle TSO for IPv4 packets */
+#define TUN_F_TSO6	0x04	/* I can handle TSO for IPv6 packets */
+#define TUN_F_TSO_ECN	0x08	/* I can handle TSO with ECN bits. */
+#define TUN_F_UFO	0x10	/* I can handle UFO packets */
+
+/* Protocol info prepended to the packets (when IFF_NO_PI is not set) */
+#define TUN_PKT_STRIP	0x0001
+struct tun_pi {
+	__u16  flags;
+	__be16 proto;
+};
+
+/*
+ * Filter spec (used for SETXXFILTER ioctls)
+ * This stuff is applicable only to the TAP (Ethernet) devices.
+ * If the count is zero the filter is disabled and the driver accepts
+ * all packets (promisc mode).
+ * If the filter is enabled in order to accept broadcast packets
+ * broadcast addr must be explicitly included in the addr list.
+ */
+#define TUN_FLT_ALLMULTI 0x0001 /* Accept all multicast packets */
+struct tun_filter {
+	__u16  flags; /* TUN_FLT_ flags see above */
+	__u16  count; /* Number of addresses */
+	__u8   addr[0][ETH_ALEN];
+};
+
+#endif /* _UAPI__IF_TUN_H */