Improve detection of IPv6 flowlabel support (Linux only).

We check at configure-time to see if IPV6_FLOWLABEL_MGR is defined
in <linux/in.6>, if it is we set a HAVE_FLOWLABEL CPP symbol to
turn on conditional compilation of the support for this feature.

configure.ac

@@ -63,4 +63,21 @@ if test "x$iperf3_cv_header_tcp_congestion" = "xyes"; then
     AC_DEFINE([HAVE_TCP_CONGESTION], [1], [Have TCP_CONGESTION sockopt.])
 fi
 
+# Check for IPv6 flowlabel support (believed to be Linux only)
+# We check for IPV6_FLOWLABEL_MGR in <linux/in6.h> even though we
+# don't use that file directly (we have our own stripped-down
+# copy, see src/flowlabel.h for more details).
+AC_CACHE_CHECK([IPv6 flowlabel support],
+[iperf3_cv_header_flowlabel],
+AC_EGREP_CPP(yes,
+[#include <sys/types.h>
+#include <linux/in6.h>
+#ifdef IPV6_FLOWLABEL_MGR
+  yes
+#endif
+],iperf3_cv_header_flowlabel=yes,iperf3_cv_header_flowlabel=no))
+if test "x$iperf3_cv_header_flowlabel" = "xyes"; then
+    AC_DEFINE([HAVE_FLOWLABEL], [1], [Have IPv6 flowlabel support.])
+fi
+
 AC_OUTPUT([Makefile src/Makefile examples/Makefile])

src/iperf_api.c

@@ -562,7 +562,9 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
         {"version4", no_argument, NULL, '4'},
         {"version6", no_argument, NULL, '6'},
         {"tos", required_argument, NULL, 'S'},
+#if defined(HAVE_FLOWLABEL)
         {"flowlabel", required_argument, NULL, 'L'},
+#endif /* HAVE_FLOWLABEL */
         {"zerocopy", no_argument, NULL, 'Z'},
         {"omit", required_argument, NULL, 'O'},
         {"file", required_argument, NULL, 'F'},
@@ -735,17 +737,17 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
 		client_flag = 1;
                 break;
             case 'L':
-#if defined(linux)
+#if defined(HAVE_FLOWLABEL)
                 test->settings->flowlabel = strtol(optarg, NULL, 0);
 		if (test->settings->flowlabel < 1 || test->settings->flowlabel > 0xfffff) {
                     i_errno = IESETFLOW;
                     return -1;
 		}
 		client_flag = 1;
-#else /* linux */
+#else /* HAVE_FLOWLABEL */
                 i_errno = IEUNIMP;
                 return -1;
-#endif /* linux */
+#endif /* HAVE_FLOWLABEL */
                 break;
             case 'Z':
                 if (!has_sendfile()) {

src/iperf_tcp.c

@@ -26,9 +26,9 @@
 #include "iperf_tcp.h"
 #include "net.h"
 
-#if defined(linux)
+#if defined(HAVE_FLOWLABEL)
 #include "flowlabel.h"
-#endif
+#endif /* HAVE_FLOWLABEL */
 
 /* iperf_tcp_recv
  *
@@ -361,7 +361,7 @@ iperf_tcp_connect(struct iperf_test *test)
 	}
 	printf("SO_SNDBUF is %u\n", opt);
     }
-#if defined(linux)
+#if defined(HAVE_FLOWLABEL)
     if (test->settings->flowlabel) {
         if (server_res->ai_addr->sa_family != AF_INET6) {
 	    saved_errno = errno;
@@ -404,7 +404,7 @@ iperf_tcp_connect(struct iperf_test *test)
             } 
 	}
     }
-#endif
+#endif /* HAVE_FLOWLABEL */
 
 #if defined(linux) && defined(TCP_CONGESTION)
     if (test->congestion) {

src/locale.c

@@ -114,9 +114,9 @@ const char usage_longstr[] = "Usage: iperf [-s|-c host] [options]\n"
                            "  -4, --version4            only use IPv4\n"
                            "  -6, --version6            only use IPv6\n"
                            "  -S, --tos N               set the IP 'type of service'\n"
-#if defined(linux)
+#if defined(HAVE_FLOWLABEL)
                            "  -L, --flowlabel N         set the IPv6 flow label (only supported on Linux)\n"
-#endif
+#endif /* HAVE_FLOWLABEL */
                            "  -Z, --zerocopy            use a 'zero copy' method of sending data\n"
                            "  -O, --omit N              omit the first n seconds\n"
                            "  -T, --title str           prefix every output line with this string\n"