datapath: test for netlink_set_err returning void
[cascardo/ovs.git] / acinclude.m4
1 # -*- autoconf -*-
2
3 # Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
4 #
5 # Licensed under the Apache License, Version 2.0 (the "License");
6 # you may not use this file except in compliance with the License.
7 # You may obtain a copy of the License at:
8 #
9 #     http://www.apache.org/licenses/LICENSE-2.0
10 #
11 # Unless required by applicable law or agreed to in writing, software
12 # distributed under the License is distributed on an "AS IS" BASIS,
13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 # See the License for the specific language governing permissions and
15 # limitations under the License.
16
17 dnl OVS_ENABLE_WERROR
18 AC_DEFUN([OVS_ENABLE_WERROR],
19   [AC_ARG_ENABLE(
20      [Werror],
21      [AC_HELP_STRING([--enable-Werror], [Add -Werror to CFLAGS])],
22      [], [enable_Werror=no])
23    AC_CONFIG_COMMANDS_PRE(
24      [if test "X$enable_Werror" = Xyes; then
25         OVS_CFLAGS="$OVS_CFLAGS -Werror"
26       fi])])
27
28 dnl OVS_CHECK_LINUX
29 dnl
30 dnl Configure linux kernel source tree 
31 AC_DEFUN([OVS_CHECK_LINUX], [
32   AC_ARG_WITH([linux],
33               [AC_HELP_STRING([--with-linux=/path/to/linux],
34                               [Specify the Linux kernel build directory])])
35   AC_ARG_WITH([linux-source],
36               [AC_HELP_STRING([--with-linux-source=/path/to/linux-source],
37                               [Specify the Linux kernel source directory
38                                (usually figured out automatically from build
39                                directory)])])
40
41   # Deprecated equivalents to --with-linux, --with-linux-source.
42   AC_ARG_WITH([l26])
43   AC_ARG_WITH([l26-source])
44
45   if test X"$with_linux" != X; then
46     KBUILD=$with_linux
47   elif test X"$with_l26" != X; then
48     KBUILD=$with_l26
49     AC_MSG_WARN([--with-l26 is deprecated, please use --with-linux instead])
50   else
51     KBUILD=
52   fi
53
54   if test X"$KBUILD" != X; then
55     if test X"$with_linux_source" != X; then
56       KSRC=$with_linux_source
57     elif test X"$with_l26_source" != X; then
58       KSRC=$with_l26_source
59       AC_MSG_WARN([--with-l26-source is deprecated, please use --with-linux-source instead])
60     else
61       KSRC=
62     fi
63   elif test X"$with_linux_source" != X || test X"$with_l26_source" != X; then
64     AC_MSG_ERROR([Linux source directory may not be specified without Linux build directory])
65   fi
66
67   if test -n "$KBUILD"; then
68     KBUILD=`eval echo "$KBUILD"`
69     case $KBUILD in
70         /*) ;;
71         *) KBUILD=`pwd`/$KBUILD ;;
72     esac
73
74     # The build directory is what the user provided.
75     # Make sure that it exists.
76     AC_MSG_CHECKING([for Linux build directory])
77     if test -d "$KBUILD"; then
78         AC_MSG_RESULT([$KBUILD])
79         AC_SUBST(KBUILD)
80     else
81         AC_MSG_RESULT([no])
82         AC_ERROR([source dir $KBUILD doesn't exist])
83     fi
84
85     # Debian breaks kernel headers into "source" header and "build" headers.
86     # We want the source headers, but $KBUILD gives us the "build" headers.
87     # Use heuristics to find the source headers.
88     AC_MSG_CHECKING([for Linux source directory])
89     if test -n "$KSRC"; then
90       KSRC=`eval echo "$KSRC"`
91       case $KSRC in
92           /*) ;;
93           *) KSRC=`pwd`/$KSRC ;;
94       esac
95       if test ! -e $KSRC/include/linux/kernel.h; then
96         AC_MSG_ERROR([$KSRC is not a kernel source directory])
97       fi
98     else
99       KSRC=$KBUILD
100       if test ! -e $KSRC/include/linux/kernel.h; then
101         # Debian kernel build Makefiles tend to include a line of the form:
102         # MAKEARGS := -C /usr/src/linux-headers-3.2.0-1-common O=/usr/src/linux-headers-3.2.0-1-486
103         # First try to extract the source directory from this line.
104         KSRC=`sed -n 's/.*-C \([[^ ]]*\).*/\1/p' "$KBUILD"/Makefile`
105         if test ! -e "$KSRC"/include/linux/kernel.h; then
106           # Didn't work.  Fall back to name-based heuristics that used to work.
107           case `echo "$KBUILD" | sed 's,/*$,,'` in # (
108             */build)
109               KSRC=`echo "$KBUILD" | sed 's,/build/*$,/source,'`
110               ;; # (
111             *)
112               KSRC=`(cd $KBUILD && pwd -P) | sed 's,-[[^-]]*$,-common,'`
113               ;;
114           esac
115         fi
116       fi
117       if test ! -e "$KSRC"/include/linux/kernel.h; then
118         AC_MSG_ERROR([cannot find source directory (please use --with-linux-source)])
119       fi
120     fi
121     AC_MSG_RESULT([$KSRC])
122
123     AC_MSG_CHECKING([for kernel version])
124     version=`sed -n 's/^VERSION = //p' "$KSRC/Makefile"`
125     patchlevel=`sed -n 's/^PATCHLEVEL = //p' "$KSRC/Makefile"`
126     sublevel=`sed -n 's/^SUBLEVEL = //p' "$KSRC/Makefile"`
127     if test X"$version" = X || test X"$patchlevel" = X; then
128        AC_ERROR([cannot determine kernel version])
129     elif test X"$sublevel" = X; then
130        kversion=$version.$patchlevel
131     else
132        kversion=$version.$patchlevel.$sublevel
133     fi
134     AC_MSG_RESULT([$kversion])
135
136     if test "$version" -ge 4; then
137        if test "$version" = 4 && test "$patchlevel" -le 3; then
138           : # Linux 4.x
139        else
140           AC_ERROR([Linux kernel in $KBUILD is version $kversion, but version newer than 4.3.x is not supported (please refer to the FAQ for advice)])
141        fi
142     elif test "$version" = 3; then
143        : # Linux 3.x
144     else
145        if test "$version" -le 1 || test "$patchlevel" -le 5 || test "$sublevel" -le 31; then
146          AC_ERROR([Linux kernel in $KBUILD is version $kversion, but version 2.6.32 or later is required])
147        else
148          : # Linux 2.6.x
149        fi
150     fi
151     if (test ! -e "$KBUILD"/include/linux/version.h && \
152         test ! -e "$KBUILD"/include/generated/uapi/linux/version.h)|| \
153        (test ! -e "$KBUILD"/include/linux/autoconf.h && \
154         test ! -e "$KBUILD"/include/generated/autoconf.h); then
155         AC_MSG_ERROR([Linux kernel source in $KBUILD is not configured])
156     fi
157     OVS_CHECK_LINUX_COMPAT
158   fi
159   AM_CONDITIONAL(LINUX_ENABLED, test -n "$KBUILD")
160 ])
161
162 dnl OVS_CHECK_DPDK
163 dnl
164 dnl Configure DPDK source tree
165 AC_DEFUN([OVS_CHECK_DPDK], [
166   AC_ARG_WITH([dpdk],
167               [AC_HELP_STRING([--with-dpdk=/path/to/dpdk],
168                               [Specify the DPDK build directory])])
169
170   if test X"$with_dpdk" != X; then
171     RTE_SDK=$with_dpdk
172
173     DPDK_INCLUDE=$RTE_SDK/include
174     DPDK_LIB_DIR=$RTE_SDK/lib
175     DPDK_LIB="-ldpdk"
176     DPDK_EXTRA_LIB=""
177     RTE_SDK_FULL=`readlink -f $RTE_SDK`
178
179     AC_COMPILE_IFELSE(
180       [AC_LANG_PROGRAM([#include <$RTE_SDK_FULL/include/rte_config.h>
181 #if !RTE_LIBRTE_VHOST_USER
182 #error
183 #endif], [])],
184                     [], [AC_DEFINE([VHOST_CUSE], [1], [DPDK vhost-cuse support enabled, vhost-user disabled.])
185                          DPDK_EXTRA_LIB="-lfuse"])
186
187     ovs_save_CFLAGS="$CFLAGS"
188     ovs_save_LDFLAGS="$LDFLAGS"
189     LDFLAGS="$LDFLAGS -L$DPDK_LIB_DIR"
190     CFLAGS="$CFLAGS -I$DPDK_INCLUDE"
191
192     # On some systems we have to add -ldl to link with dpdk
193     #
194     # This code, at first, tries to link without -ldl (""),
195     # then adds it and tries again.
196     # Before each attempt the search cache must be unset,
197     # otherwise autoconf will stick with the old result
198
199     found=false
200     save_LIBS=$LIBS
201     for extras in "" "-ldl"; do
202         LIBS="$DPDK_LIB $extras $save_LIBS $DPDK_EXTRA_LIB"
203         AC_LINK_IFELSE(
204            [AC_LANG_PROGRAM([#include <rte_config.h>
205                              #include <rte_eal.h>],
206                             [int rte_argc; char ** rte_argv;
207                              rte_eal_init(rte_argc, rte_argv);])],
208            [found=true])
209         if $found; then
210             break
211         fi
212     done
213     if $found; then :; else
214         AC_MSG_ERROR([cannot link with dpdk])
215     fi
216     CFLAGS="$ovs_save_CFLAGS"
217     LDFLAGS="$ovs_save_LDFLAGS"
218     OVS_LDFLAGS="$OVS_LDFLAGS -L$DPDK_LIB_DIR"
219     OVS_CFLAGS="$OVS_CFLAGS -I$DPDK_INCLUDE"
220     OVS_ENABLE_OPTION([-mssse3])
221
222     # DPDK pmd drivers are not linked unless --whole-archive is used.
223     #
224     # This happens because the rest of the DPDK code doesn't use any symbol in
225     # the pmd driver objects, and the drivers register themselves using an
226     # __attribute__((constructor)) function.
227     #
228     # These options are specified inside a single -Wl directive to prevent
229     # autotools from reordering them.
230     DPDK_vswitchd_LDFLAGS=-Wl,--whole-archive,$DPDK_LIB,--no-whole-archive
231     AC_SUBST([DPDK_vswitchd_LDFLAGS])
232     AC_DEFINE([DPDK_NETDEV], [1], [System uses the DPDK module.])
233
234   else
235     RTE_SDK=
236   fi
237
238   AM_CONDITIONAL([DPDK_NETDEV], test -n "$RTE_SDK")
239 ])
240
241 dnl OVS_GREP_IFELSE(FILE, REGEX, [IF-MATCH], [IF-NO-MATCH])
242 dnl
243 dnl Greps FILE for REGEX.  If it matches, runs IF-MATCH, otherwise IF-NO-MATCH.
244 dnl If IF-MATCH is empty then it defines to OVS_DEFINE(HAVE_<REGEX>), with
245 dnl <REGEX> translated to uppercase.
246 AC_DEFUN([OVS_GREP_IFELSE], [
247   AC_MSG_CHECKING([whether $2 matches in $1])
248   if test -f $1; then
249     grep '$2' $1 >/dev/null 2>&1
250     status=$?
251     case $status in
252       0) 
253         AC_MSG_RESULT([yes])
254         m4_if([$3], [], [OVS_DEFINE([HAVE_]m4_toupper([$2]))], [$3])
255         ;;
256       1) 
257         AC_MSG_RESULT([no])
258         $4
259         ;;
260       *) 
261         AC_MSG_ERROR([grep exited with status $status])
262         ;;
263     esac
264   else
265     AC_MSG_RESULT([file not found])
266     $4
267   fi
268 ])
269
270 dnl OVS_FIND_FIELD_IFELSE(FILE, STRUCTURE, REGEX, [IF-MATCH], [IF-NO-MATCH])
271 dnl
272 dnl Looks for STRUCTURE in FILE. If it is found, greps for REGEX within the
273 dnl structure definition. If this is successful, runs IF-MATCH, otherwise
274 dnl IF_NO_MATCH. If IF-MATCH is empty then it defines to
275 dnl OVS_DEFINE(HAVE_<STRUCTURE>_WITH_<REGEX>), with <STRUCTURE> and <REGEX>
276 dnl translated to uppercase.
277 AC_DEFUN([OVS_FIND_FIELD_IFELSE], [
278   AC_MSG_CHECKING([whether $2 has member $3 in $1])
279   if test -f $1; then
280     awk '/$2.{/,/^}/' $1 2>/dev/null | grep '$3' >/dev/null
281     status=$?
282     case $status in
283       0)
284         AC_MSG_RESULT([yes])
285         m4_if([$4], [], [OVS_DEFINE([HAVE_]m4_toupper([$2])[_WITH_]m4_toupper([$3]))], [$4])
286         ;;
287       1)
288         AC_MSG_RESULT([no])
289         $5
290         ;;
291       *)
292         AC_MSG_ERROR([grep exited with status $status])
293         ;;
294     esac
295   else
296     AC_MSG_RESULT([file not found])
297     $5
298   fi
299 ])
300
301 dnl OVS_DEFINE(NAME)
302 dnl
303 dnl Defines NAME to 1 in kcompat.h.
304 AC_DEFUN([OVS_DEFINE], [
305   echo '#define $1 1' >> datapath/linux/kcompat.h.new
306 ])
307
308 dnl OVS_CHECK_LINUX_COMPAT
309 dnl
310 dnl Runs various Autoconf checks on the Linux 2.6 kernel source in
311 dnl the directory in $KBUILD.
312 AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
313   rm -f datapath/linux/kcompat.h.new
314   mkdir -p datapath/linux
315   : > datapath/linux/kcompat.h.new
316
317   echo '#include <linux/version.h>
318 #ifndef RHEL_RELEASE_CODE
319 #define RHEL_RELEASE_CODE 0
320 #define RHEL_RELEASE_VERSION(a, b) 0
321 #endif' >> datapath/linux/kcompat.h.new
322
323   OVS_GREP_IFELSE([$KSRC/arch/x86/include/asm/checksum_32.h], [src_err,],
324                   [OVS_DEFINE([HAVE_CSUM_COPY_DBG])])
325
326   OVS_GREP_IFELSE([$KSRC/include/net/addrconf.h], [ipv6_dst_lookup.*net],
327                   [OVS_DEFINE([HAVE_IPV6_DST_LOOKUP_NET])])
328   OVS_GREP_IFELSE([$KSRC/include/net/addrconf.h], [ipv6_stub])
329
330   OVS_GREP_IFELSE([$KSRC/include/linux/err.h], [ERR_CAST])
331   OVS_GREP_IFELSE([$KSRC/include/linux/err.h], [IS_ERR_OR_NULL])
332
333   OVS_GREP_IFELSE([$KSRC/include/linux/etherdevice.h], [eth_hw_addr_random])
334   OVS_GREP_IFELSE([$KSRC/include/linux/etherdevice.h], [ether_addr_copy])
335
336   OVS_GREP_IFELSE([$KSRC/include/uapi/linux/if_link.h], [IFLA_GENEVE_TOS])
337   OVS_GREP_IFELSE([$KSRC/include/uapi/linux/if_link.h], [rtnl_link_stats64])
338   OVS_GREP_IFELSE([$KSRC/include/linux/if_link.h], [rtnl_link_stats64])
339   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [vlan_set_encap_proto])
340   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [vlan_hwaccel_push_inside])
341
342   OVS_GREP_IFELSE([$KSRC/include/linux/in.h], [ipv4_is_multicast])
343   OVS_GREP_IFELSE([$KSRC/include/linux/in.h], [proto_ports_offset])
344   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [__ip_select_ident.*dst_entry],
345                   [OVS_DEFINE([HAVE_IP_SELECT_IDENT_USING_DST_ENTRY])])
346   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [__ip_select_ident.*net],
347                   [OVS_DEFINE([HAVE_IP_SELECT_IDENT_USING_NET])])
348
349   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [inet_get_local_port_range.*net],
350                   [OVS_DEFINE([HAVE_INET_GET_LOCAL_PORT_RANGE_USING_NET])])
351   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [ip_do_fragment])
352   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [ip_is_fragment])
353   OVS_GREP_IFELSE([$KSRC/include/net/ip.h], [ip_skb_dst_mtu])
354   OVS_GREP_IFELSE([$KSRC/include/net/inet_frag.h], [hashfn.*const],
355                   [OVS_DEFINE([HAVE_INET_FRAGS_CONST])])
356   OVS_GREP_IFELSE([$KSRC/include/net/dst_metadata.h], [metadata_dst])
357
358   OVS_GREP_IFELSE([$KSRC/include/linux/net.h], [sock_create_kern.*net],
359                   [OVS_DEFINE([HAVE_SOCK_CREATE_KERN_NET])])
360   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [dev_disable_lro])
361   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [dev_get_stats])
362   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [dev_get_by_index_rcu])
363   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [dev_recursion_level])
364   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [__skb_gso_segment])
365   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [can_checksum_protocol])
366   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [ndo_get_iflink])
367   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [netdev_features_t])
368   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [pcpu_sw_netstats])
369   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [netdev_rx_handler_register])
370   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [net_device_extended])
371   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [rx_handler_func_t.*pskb],
372                   [OVS_DEFINE([HAVE_RX_HANDLER_PSKB])])
373   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [netif_needs_gso.*net_device],
374                   [OVS_DEFINE([HAVE_NETIF_NEEDS_GSO_NETDEV])])
375   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [udp_offload])
376   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [udp_offload.*uoff],
377                   [OVS_DEFINE([HAVE_UDP_OFFLOAD_ARG_UOFF])])
378   OVS_GREP_IFELSE([$KSRC/include/linux/netdevice.h], [gro_remcsum])
379
380   OVS_GREP_IFELSE([$KSRC/include/linux/netfilter.h], [nf_hook_state])
381   OVS_GREP_IFELSE([$KSRC/include/linux/netfilter.h], [nf_register_net_hook])
382   OVS_GREP_IFELSE([$KSRC/include/linux/netfilter.h], [nf_hookfn.*nf_hook_ops],
383                   [OVS_DEFINE([HAVE_NF_HOOKFN_ARG_OPS])])
384
385   OVS_GREP_IFELSE([$KSRC/include/net/netfilter/nf_conntrack.h],
386                   [tmpl_alloc.*conntrack_zone],
387                   [OVS_DEFINE([HAVE_NF_CT_TMPL_ALLOC_TAKES_STRUCT_ZONE])])
388
389   OVS_GREP_IFELSE([$KSRC/include/linux/random.h], [prandom_u32])
390   OVS_GREP_IFELSE([$KSRC/include/linux/random.h], [prandom_u32_max])
391
392   OVS_GREP_IFELSE([$KSRC/include/net/rtnetlink.h], [get_link_net])
393   OVS_GREP_IFELSE([$KSRC/include/net/rtnetlink.h], [name_assign_type])
394   OVS_GREP_IFELSE([$KSRC/include/net/rtnetlink.h], [rtnl_create_link.*src_net],
395                   [OVS_DEFINE([HAVE_RTNL_CREATE_LINK_SRC_NET])])
396   OVS_GREP_IFELSE([$KSRC/include/net/net_namespace.h], [possible_net_t])
397
398   OVS_GREP_IFELSE([$KSRC/include/linux/rcupdate.h], [rcu_read_lock_held], [],
399                   [OVS_GREP_IFELSE([$KSRC/include/linux/rtnetlink.h],
400                                    [rcu_read_lock_held])])
401   OVS_GREP_IFELSE([$KSRC/include/linux/rtnetlink.h], [lockdep_rtnl_is_held])
402   
403   # Check for the proto_data_valid member in struct sk_buff.  The [^@]
404   # is necessary because some versions of this header remove the
405   # member but retain the kerneldoc comment that describes it (which
406   # starts with @).  The brackets must be doubled because of m4
407   # quoting rules.
408   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [[[^@]]proto_data_valid],
409                   [OVS_DEFINE([HAVE_PROTO_DATA_VALID])])
410   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_checksum_start_offset])
411   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [inner_protocol])
412   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [inner_mac_header])
413   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [inner_network_header])
414   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [kfree_skb_list])
415   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_scrub_packet.*xnet],
416                   [OVS_DEFINE([HAVE_SKB_SCRUB_PACKET_XNET])])
417   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [rxhash])
418   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [u16.*rxhash],
419                   [OVS_DEFINE([HAVE_U16_RXHASH])])
420   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_dst(],
421                   [OVS_DEFINE([HAVE_SKB_DST_ACCESSOR_FUNCS])])
422   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], 
423                   [skb_copy_from_linear_data_offset])
424   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h],
425                   [skb_reset_tail_pointer])
426   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_cow_head])
427   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_transport_header],
428                   [OVS_DEFINE([HAVE_SKBUFF_HEADER_HELPERS])])
429   OVS_GREP_IFELSE([$KSRC/include/linux/icmpv6.h], [icmp6_hdr],
430                   [OVS_DEFINE([HAVE_ICMP6_HDR])])
431   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_warn_if_lro],
432                   [OVS_DEFINE([HAVE_SKB_WARN_LRO])])
433   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [consume_skb])
434   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_frag_page])
435   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_has_frag_list])
436   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [__skb_fill_page_desc])
437   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_reset_mac_len])
438   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_unclone])
439   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_orphan_frags])
440   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_get_hash])
441   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_clear_hash])
442   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [int.skb_zerocopy(],
443                   [OVS_DEFINE([HAVE_SKB_ZEROCOPY])])
444   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [u8.*l4_rxhash],
445                   [OVS_DEFINE([HAVE_L4_RXHASH])])
446   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_ensure_writable])
447   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_vlan_pop])
448   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [skb_vlan_push])
449
450   OVS_GREP_IFELSE([$KSRC/include/linux/types.h], [bool],
451                   [OVS_DEFINE([HAVE_BOOL_TYPE])])
452   OVS_GREP_IFELSE([$KSRC/include/linux/types.h], [__wsum],
453                   [OVS_DEFINE([HAVE_CSUM_TYPES])])
454   OVS_GREP_IFELSE([$KSRC/include/uapi/linux/types.h], [__wsum],
455                   [OVS_DEFINE([HAVE_CSUM_TYPES])])
456
457   OVS_GREP_IFELSE([$KSRC/include/net/checksum.h], [csum_replace4])
458   OVS_GREP_IFELSE([$KSRC/include/net/checksum.h], [csum_unfold])
459
460   OVS_GREP_IFELSE([$KSRC/include/net/dst.h], [dst_discard_sk])
461
462   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [genl_has_listeners])
463   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [mcgrp_offset])
464   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [parallel_ops])
465   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [genlmsg_new_unicast])
466   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [netlink_has_listeners(net->genl_sock],
467                   [OVS_DEFINE([HAVE_GENL_HAS_LISTENERS_TAKES_NET])])
468   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [genlmsg_parse])
469   OVS_GREP_IFELSE([$KSRC/include/net/genetlink.h], [genl_notify.*family],
470                   [OVS_DEFINE([HAVE_GENL_NOTIFY_TAKES_FAMILY])])
471
472   OVS_FIND_FIELD_IFELSE([$KSRC/include/net/genetlink.h],
473                         [genl_multicast_group], [id])
474   OVS_GREP_IFELSE([$KSRC/include/net/geneve.h], [geneve_hdr])
475
476   OVS_GREP_IFELSE([$KSRC/include/net/gre.h], [gre_cisco_register])
477   OVS_GREP_IFELSE([$KSRC/include/net/gre.h], [gre_handle_offloads])
478   OVS_GREP_IFELSE([$KSRC/include/net/ipv6.h], [IP6_FH_F_SKIP_RH])
479   OVS_GREP_IFELSE([$KSRC/include/net/ipv6.h], [ip6_local_out_sk])
480   OVS_GREP_IFELSE([$KSRC/include/net/ipv6.h], [__ipv6_addr_jhash])
481   OVS_GREP_IFELSE([$KSRC/include/net/ip6_fib.h], [rt6i.*u.dst],
482                   [OVS_DEFINE([HAVE_RT6INFO_DST_UNION])])
483   OVS_GREP_IFELSE([$KSRC/include/net/ip6_route.h], [ip6_frag.*sock],
484                   [OVS_DEFINE([HAVE_IP_FRAGMENT_TAKES_SOCK])])
485
486   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_get_be16])
487   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_put_be16])
488   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_put_be32])
489   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_put_be64])
490   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_put_in_addr])
491   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_find_nested])
492   OVS_GREP_IFELSE([$KSRC/include/net/netlink.h], [nla_is_last])
493   OVS_GREP_IFELSE([$KSRC/include/linux/netlink.h], [void.*netlink_set_err],
494                   [OVS_DEFINE([HAVE_VOID_NETLINK_SET_ERR])])
495
496   OVS_GREP_IFELSE([$KSRC/include/net/sctp/checksum.h], [sctp_compute_cksum])
497
498   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [ADD_ALL_VLANS_CMD],
499                   [OVS_DEFINE([HAVE_VLAN_BUG_WORKAROUND])])
500   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [vlan_insert_tag_set_proto])
501   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [__vlan_insert_tag])
502   OVS_GREP_IFELSE([$KSRC/include/linux/if_vlan.h], [vlan_get_protocol])
503
504   OVS_GREP_IFELSE([$KSRC/include/linux/u64_stats_sync.h], [u64_stats_fetch_begin_irq])
505
506   OVS_GREP_IFELSE([$KSRC/include/linux/openvswitch.h], [openvswitch_handle_frame_hook],
507                   [OVS_DEFINE([HAVE_RHEL_OVS_HOOK])])
508   OVS_GREP_IFELSE([$KSRC/include/net/vxlan.h], [struct vxlan_metadata],
509                   [OVS_DEFINE([HAVE_VXLAN_METADATA])])
510   OVS_GREP_IFELSE([$KSRC/include/net/vxlan.h], [VXLAN_HF_RCO])
511   OVS_GREP_IFELSE([$KSRC/include/net/udp.h], [udp_flow_src_port],
512                   [OVS_GREP_IFELSE([$KSRC/include/net/udp.h], [inet_get_local_port_range(net],
513                                    [OVS_DEFINE([HAVE_UDP_FLOW_SRC_PORT])])])
514   OVS_GREP_IFELSE([$KSRC/include/net/udp.h], [udp_v4_check])
515   OVS_GREP_IFELSE([$KSRC/include/net/udp.h], [udp_set_csum])
516   OVS_GREP_IFELSE([$KSRC/include/net/udp_tunnel.h], [udp_tunnel_gro_complete])
517   OVS_GREP_IFELSE([$KSRC/include/net/udp_tunnel.h], [ipv6_v6only],
518                   [OVS_DEFINE([HAVE_UDP_TUNNEL_IPV6])])
519
520   OVS_GREP_IFELSE([$KSRC/include/linux/skbuff.h], [ignore_df],
521                   [OVS_DEFINE([HAVE_IGNORE_DF_RENAME])])
522   OVS_GREP_IFELSE([$KSRC/include/uapi/linux/netdevice.h], [NET_NAME_UNKNOWN],
523                   [OVS_DEFINE([HAVE_NET_NAME_UNKNOWN])])
524
525   OVS_GREP_IFELSE([$KSRC/include/linux/utsrelease.h], [el6],
526                   [OVS_DEFINE([HAVE_RHEL6_PER_CPU])])
527
528   if test "$version" = 4 && test "$patchlevel" -le 2; then
529         OVS_DEFINE([OVS_FRAGMENT_BACKPORT])
530   elif test "$version" = 3 && test "$patchlevel" -ge 10; then
531         OVS_DEFINE([OVS_FRAGMENT_BACKPORT])
532   fi
533
534   if cmp -s datapath/linux/kcompat.h.new \
535             datapath/linux/kcompat.h >/dev/null 2>&1; then
536     rm datapath/linux/kcompat.h.new
537   else
538     mv datapath/linux/kcompat.h.new datapath/linux/kcompat.h
539   fi
540 ])
541
542 dnl Checks for net/if_packet.h.
543 AC_DEFUN([OVS_CHECK_IF_PACKET],
544   [AC_CHECK_HEADER([net/if_packet.h],
545                    [HAVE_IF_PACKET=yes],
546                    [HAVE_IF_PACKET=no])
547    AM_CONDITIONAL([HAVE_IF_PACKET], [test "$HAVE_IF_PACKET" = yes])
548    if test "$HAVE_IF_PACKET" = yes; then
549       AC_DEFINE([HAVE_IF_PACKET], [1],
550                 [Define to 1 if net/if_packet.h is available.])
551    fi])
552
553 dnl Checks for net/if_dl.h.
554 dnl
555 dnl (We use this as a proxy for checking whether we're building on FreeBSD
556 dnl or NetBSD.)
557 AC_DEFUN([OVS_CHECK_IF_DL],
558   [AC_CHECK_HEADER([net/if_dl.h],
559                    [HAVE_IF_DL=yes],
560                    [HAVE_IF_DL=no])
561    AM_CONDITIONAL([HAVE_IF_DL], [test "$HAVE_IF_DL" = yes])
562    if test "$HAVE_IF_DL" = yes; then
563       AC_DEFINE([HAVE_IF_DL], [1],
564                 [Define to 1 if net/if_dl.h is available.])
565
566       # On these platforms we use libpcap to access network devices.
567       AC_SEARCH_LIBS([pcap_open_live], [pcap])
568    fi])
569
570 dnl Checks for buggy strtok_r.
571 dnl
572 dnl Some versions of glibc 2.7 has a bug in strtok_r when compiling
573 dnl with optimization that can cause segfaults:
574 dnl
575 dnl http://sources.redhat.com/bugzilla/show_bug.cgi?id=5614.
576 AC_DEFUN([OVS_CHECK_STRTOK_R],
577   [AC_CACHE_CHECK(
578      [whether strtok_r macro segfaults on some inputs],
579      [ovs_cv_strtok_r_bug],
580      [AC_RUN_IFELSE(
581         [AC_LANG_PROGRAM([#include <stdio.h>
582                           #include <string.h>
583                          ],
584                          [[#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
585                            /* Assume bug is present, because relatively minor
586                               changes in compiler settings (e.g. optimization
587                               level) can make it crop up. */
588                            return 1;
589                            #else
590                            char string[] = ":::";
591                            char *save_ptr = (char *) 0xc0ffee;
592                            char *token1, *token2;
593                            token1 = strtok_r(string, ":", &save_ptr);
594                            token2 = strtok_r(NULL, ":", &save_ptr);
595                            freopen ("/dev/null", "w", stdout);
596                            printf ("%s %s\n", token1, token2);
597                            return 0;
598                            #endif
599                           ]])],
600         [ovs_cv_strtok_r_bug=no],
601         [ovs_cv_strtok_r_bug=yes],
602         [ovs_cv_strtok_r_bug=yes])])
603    if test $ovs_cv_strtok_r_bug = yes; then
604      AC_DEFINE([HAVE_STRTOK_R_BUG], [1],
605                [Define if strtok_r macro segfaults on some inputs])
606    fi
607 ])
608
609 dnl ----------------------------------------------------------------------
610 dnl These macros are from GNU PSPP, with the following original license:
611 dnl Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
612 dnl This file is free software; the Free Software Foundation
613 dnl gives unlimited permission to copy and/or distribute it,
614 dnl with or without modifications, as long as this notice is preserved.
615
616 AC_DEFUN([_OVS_CHECK_CC_OPTION], [dnl
617   m4_define([ovs_cv_name], [ovs_cv_[]m4_translit([$1], [-=], [__])])dnl
618   AC_CACHE_CHECK([whether $CC accepts $1], [ovs_cv_name], 
619     [ovs_save_CFLAGS="$CFLAGS"
620      dnl Include -Werror in the compiler options, because without -Werror
621      dnl clang's GCC-compatible compiler driver does not return a failure
622      dnl exit status even though it complains about options it does not
623      dnl understand.
624      dnl
625      dnl Also, check stderr as gcc exits with status 0 for options
626      dnl rejected at getopt level.
627      dnl    % touch /tmp/a.c
628      dnl    % gcc -g -c -Werror -Qunused-arguments /tmp/a.c; echo $?
629      dnl    gcc: unrecognized option '-Qunused-arguments'
630      dnl    0
631      dnl    %
632      CFLAGS="$CFLAGS $WERROR $1"
633      AC_COMPILE_IFELSE([AC_LANG_PROGRAM(,)], [if test -s conftest.err && grep "unrecognized option" conftest.err; then ovs_cv_name[]=no; else ovs_cv_name[]=yes; fi], [ovs_cv_name[]=no])
634      CFLAGS="$ovs_save_CFLAGS"])
635   if test $ovs_cv_name = yes; then
636     m4_if([$2], [], [:], [$2])
637   else
638     m4_if([$3], [], [:], [$3])
639   fi
640 ])
641
642 dnl OVS_CHECK_WERROR
643 dnl
644 dnl Check whether the C compiler accepts -Werror.
645 dnl Sets $WERROR to "-Werror", if so, and otherwise to the empty string.
646 AC_DEFUN([OVS_CHECK_WERROR],
647   [WERROR=
648    _OVS_CHECK_CC_OPTION([-Werror], [WERROR=-Werror])])
649
650 dnl OVS_CHECK_CC_OPTION([OPTION], [ACTION-IF-ACCEPTED], [ACTION-IF-REJECTED])
651 dnl Check whether the given C compiler OPTION is accepted.
652 dnl If so, execute ACTION-IF-ACCEPTED, otherwise ACTION-IF-REJECTED.
653 AC_DEFUN([OVS_CHECK_CC_OPTION],
654   [AC_REQUIRE([OVS_CHECK_WERROR])
655    _OVS_CHECK_CC_OPTION([$1], [$2], [$3])])
656
657 dnl OVS_ENABLE_OPTION([OPTION])
658 dnl Check whether the given C compiler OPTION is accepted.
659 dnl If so, add it to WARNING_FLAGS.
660 dnl Example: OVS_ENABLE_OPTION([-Wdeclaration-after-statement])
661 AC_DEFUN([OVS_ENABLE_OPTION], 
662   [OVS_CHECK_CC_OPTION([$1], [WARNING_FLAGS="$WARNING_FLAGS $1"])
663    AC_SUBST([WARNING_FLAGS])])
664
665 dnl OVS_CONDITIONAL_CC_OPTION([OPTION], [CONDITIONAL])
666 dnl Check whether the given C compiler OPTION is accepted.
667 dnl If so, enable the given Automake CONDITIONAL.
668
669 dnl Example: OVS_CONDITIONAL_CC_OPTION([-Wno-unused], [HAVE_WNO_UNUSED])
670 AC_DEFUN([OVS_CONDITIONAL_CC_OPTION],
671   [OVS_CHECK_CC_OPTION(
672     [$1], [ovs_have_cc_option=yes], [ovs_have_cc_option=no])
673    AM_CONDITIONAL([$2], [test $ovs_have_cc_option = yes])])
674 dnl ----------------------------------------------------------------------
675
676 dnl Check for too-old XenServer.
677 AC_DEFUN([OVS_CHECK_XENSERVER_VERSION],
678   [AC_CACHE_CHECK([XenServer release], [ovs_cv_xsversion],
679     [if test -e /etc/redhat-release; then
680        ovs_cv_xsversion=`sed -n 's/^XenServer DDK release \([[^-]]*\)-.*/\1/p' /etc/redhat-release`
681      fi
682      if test -z "$ovs_cv_xsversion"; then
683        ovs_cv_xsversion=none
684      fi])
685   case $ovs_cv_xsversion in
686     none)
687       ;;
688
689     [[1-9]][[0-9]]* |                    dnl XenServer 10 or later
690     [[6-9]]* |                           dnl XenServer 6 or later
691     5.[[7-9]]* |                         dnl XenServer 5.7 or later
692     5.6.[[1-9]][[0-9]][[0-9]][[0-9]]* |  dnl XenServer 5.6.1000 or later
693     5.6.[[2-9]][[0-9]][[0-9]]* |         dnl XenServer 5.6.200 or later
694     5.6.1[[0-9]][[0-9]])                 dnl Xenserver 5.6.100 or later
695       ;;
696
697     *)
698       AC_MSG_ERROR([This appears to be XenServer $ovs_cv_xsversion, but only XenServer 5.6.100 or later is supported.  (If you are really using a supported version of XenServer, you may override this error message by specifying 'ovs_cv_xsversion=5.6.100' on the "configure" command line.)])
699       ;;
700   esac])
701
702 dnl OVS_MAKE_HAS_IF([if-true], [if-false])
703 dnl
704 dnl Checks whether make has the GNU make $(if condition,then,else) extension.
705 dnl Runs 'if-true' if so, 'if-false' otherwise.
706 AC_DEFUN([OVS_CHECK_MAKE_IF],
707   [AC_CACHE_CHECK(
708      [whether ${MAKE-make} has GNU make \$(if) extension],
709      [ovs_cv_gnu_make_if],
710      [cat <<'EOF' > conftest.mk
711 conftest.out:
712         echo $(if x,y,z) > conftest.out
713 .PHONY: all
714 EOF
715       rm -f conftest.out
716       AS_ECHO(["$as_me:$LINENO: invoking ${MAKE-make} -f conftest.mk all:"]) >&AS_MESSAGE_LOG_FD 2>&1
717       ${MAKE-make} -f conftest.mk conftest.out >&AS_MESSAGE_LOG_FD 2>&1
718       AS_ECHO(["$as_me:$LINENO: conftest.out contains:"]) >&AS_MESSAGE_LOG_FD 2>&1
719       cat conftest.out >&AS_MESSAGE_LOG_FD 2>&1
720       result=`cat conftest.out`
721       rm -f conftest.mk conftest.out
722       if test "X$result" = "Xy"; then
723         ovs_cv_gnu_make_if=yes
724       else
725         ovs_cv_gnu_make_if=no
726       fi])])
727
728 dnl OVS_CHECK_GNU_MAKE
729 dnl
730 dnl Checks whether make is GNU make (because Linux kernel Makefiles
731 dnl only work with GNU make).
732 AC_DEFUN([OVS_CHECK_GNU_MAKE],
733   [AC_CACHE_CHECK(
734      [whether ${MAKE-make} is GNU make],
735      [ovs_cv_gnu_make],
736      [rm -f conftest.out
737       AS_ECHO(["$as_me:$LINENO: invoking ${MAKE-make} --version:"]) >&AS_MESSAGE_LOG_FD 2>&1
738       ${MAKE-make} --version >conftest.out 2>&1
739       cat conftest.out >&AS_MESSAGE_LOG_FD 2>&1
740       result=`cat conftest.out`
741       rm -f conftest.mk conftest.out
742
743       case $result in # (
744         GNU*) ovs_cv_gnu_make=yes ;; # (
745         *) ovs_cv_gnu_make=no ;;
746       esac])
747    AM_CONDITIONAL([GNU_MAKE], [test $ovs_cv_gnu_make = yes])])
748
749 dnl OVS_CHECK_SPARSE_TARGET
750 dnl
751 dnl The "cgcc" script from "sparse" isn't very good at detecting the
752 dnl target for which the code is being built.  This helps it out.
753 AC_DEFUN([OVS_CHECK_SPARSE_TARGET],
754   [AC_CACHE_CHECK(
755     [target hint for cgcc],
756     [ac_cv_sparse_target],
757     [AS_CASE([`$CC -dumpmachine 2>/dev/null`],
758        [i?86-* | athlon-*], [ac_cv_sparse_target=x86],
759        [x86_64-*], [ac_cv_sparse_target=x86_64],
760        [ac_cv_sparse_target=other])])
761    AS_CASE([$ac_cv_sparse_target],
762      [x86], [SPARSEFLAGS= CGCCFLAGS=-target=i86],
763      [x86_64], [SPARSEFLAGS=-m64 CGCCFLAGS=-target=x86_64],
764      [SPARSEFLAGS= CGCCFLAGS=])
765    AC_SUBST([SPARSEFLAGS])
766    AC_SUBST([CGCCFLAGS])])
767
768 dnl OVS_SPARSE_EXTRA_INCLUDES
769 dnl
770 dnl The cgcc script from "sparse" does not search gcc's default
771 dnl search path. Get the default search path from GCC and pass
772 dnl them to sparse.
773 AC_DEFUN([OVS_SPARSE_EXTRA_INCLUDES],
774     AC_SUBST([SPARSE_EXTRA_INCLUDES],
775            [`$CC -v -E - </dev/null 2>&1 >/dev/null | sed -n -e '/^#include.*search.*starts.*here:/,/^End.*of.*search.*list\./s/^ \(.*\)/-I \1/p' |grep -v /usr/lib | grep -x -v '\-I /usr/include' | tr \\\n ' ' `] ))
776
777 dnl OVS_ENABLE_SPARSE
778 AC_DEFUN([OVS_ENABLE_SPARSE],
779   [AC_REQUIRE([OVS_CHECK_SPARSE_TARGET])
780    AC_REQUIRE([OVS_CHECK_MAKE_IF])
781    AC_REQUIRE([OVS_SPARSE_EXTRA_INCLUDES])
782    : ${SPARSE=sparse}
783    AC_SUBST([SPARSE])
784    AC_CONFIG_COMMANDS_PRE(
785      [if test $ovs_cv_gnu_make_if = yes; then
786         CC='$(if $(C),env REAL_CC="'"$CC"'" CHECK="$(SPARSE) -I $(top_srcdir)/include/sparse $(SPARSEFLAGS) $(SPARSE_EXTRA_INCLUDES) " cgcc $(CGCCFLAGS),'"$CC"')'
787       fi])])
788
789 dnl OVS_PTHREAD_SET_NAME
790 dnl
791 dnl This checks for three known variants of pthreads functions for setting
792 dnl the name of the current thread:
793 dnl
794 dnl   glibc: int pthread_setname_np(pthread_t, const char *name);
795 dnl   NetBSD: int pthread_setname_np(pthread_t, const char *format, void *arg);
796 dnl   FreeBSD: int pthread_set_name_np(pthread_t, const char *name);
797 dnl
798 dnl For glibc and FreeBSD, the arguments are just a thread and its name.  For
799 dnl NetBSD, 'format' is a printf() format string and 'arg' is an argument to
800 dnl provide to it.
801 dnl
802 dnl This macro defines:
803 dnl
804 dnl    glibc: HAVE_GLIBC_PTHREAD_SETNAME_NP
805 dnl    NetBSD: HAVE_NETBSD_PTHREAD_SETNAME_NP
806 dnl    FreeBSD: HAVE_PTHREAD_SET_NAME_NP
807 AC_DEFUN([OVS_CHECK_PTHREAD_SET_NAME],
808   [AC_CHECK_FUNCS([pthread_set_name_np])
809    if test $ac_cv_func_pthread_set_name_np != yes; then
810      AC_CACHE_CHECK(
811        [for pthread_setname_np() variant],
812        [ovs_cv_pthread_setname_np],
813        [AC_LINK_IFELSE(
814          [AC_LANG_PROGRAM([#include <pthread.h>
815   ], [pthread_setname_np(pthread_self(), "name");])],
816          [ovs_cv_pthread_setname_np=glibc],
817          [AC_LINK_IFELSE(
818            [AC_LANG_PROGRAM([#include <pthread.h>
819 ], [pthread_setname_np(pthread_self(), "%s", "name");])],
820            [ovs_cv_pthread_setname_np=netbsd],
821            [ovs_cv_pthread_setname_np=none])])])
822      case $ovs_cv_pthread_setname_np in # (
823        glibc)
824           AC_DEFINE(
825             [HAVE_GLIBC_PTHREAD_SETNAME_NP], [1],
826             [Define to 1 if pthread_setname_np() is available and takes 2 parameters (like glibc).])
827           ;; # (
828        netbsd)
829           AC_DEFINE(
830             [HAVE_NETBSD_PTHREAD_SETNAME_NP], [1],
831             [Define to 1 if pthread_setname_np() is available and takes 3 parameters (like NetBSD).])
832           ;;
833      esac
834    fi])
835
836 dnl OVS_CHECK_LINUX_HOST.
837 dnl
838 dnl Checks whether we're building for a Linux host, based on the presence of
839 dnl the __linux__ preprocessor symbol, and sets up an Automake conditional
840 dnl LINUX based on the result.
841 AC_DEFUN([OVS_CHECK_LINUX_HOST],
842   [AC_CACHE_CHECK(
843      [whether __linux__ is defined],
844      [ovs_cv_linux],
845      [AC_COMPILE_IFELSE(
846         [AC_LANG_PROGRAM([enum { LINUX = __linux__};], [])],
847         [ovs_cv_linux=true],
848         [ovs_cv_linux=false])])
849    AM_CONDITIONAL([LINUX], [$ovs_cv_linux])])