try to fix tests on travis-ci (no ipv6?)

ci/test-03-forbidden.pl

@@ -60,7 +60,7 @@ $cmd7->stderr_is_eq("fping: specify only one of c, l\n");
 my $cmd8 = Test::Command->new(cmd => "fping -b 65509 127.0.0.1");
 $cmd8->exit_is_num(1);
 $cmd8->stdout_is_eq("");
-$cmd8->stderr_is_eq("fping: data size 65509 not valid, must be between 0 and 65508\n");
+$cmd8->stderr_is_eq("fping: data size 65509 not valid, must be lower than 65508\n");
 
 # fping -B 0.9
 my $cmd9 = Test::Command->new(cmd => "fping -B 0.9 127.0.0.1");

ci/test-09-option-r-t.pl

@@ -1,6 +1,7 @@
 #!/usr/bin/perl -w
 
 use Test::Command tests => 18;
+use Test::More;
 
 #  -R         random bytes
 #  -r n       number of retries (default 3)
@@ -17,12 +18,14 @@ $cmd->stdout_is_eq("");
 $cmd->stderr_like(qr{127\.0\.0\.1 : xmt/rcv/%loss = 3/3/0%.*});
 }
 
-# fping6 -R
-{
-my $cmd = Test::Command->new(cmd => "fping6 -q -R -c3 -p100 ::1");
-$cmd->exit_is_num(0);
-$cmd->stdout_is_eq("");
-$cmd->stderr_like(qr{::1 : xmt/rcv/%loss = 3/3/0%.*});
+SKIP: {
+    if(system("/sbin/ifconfig | grep inet6") != 0) {
+        skip 'No IPv6 on this host', 3;
+    }
+    my $cmd = Test::Command->new(cmd => "fping6 -q -R -c3 -p100 ::1");
+    $cmd->exit_is_num(0);
+    $cmd->stdout_is_eq("");
+    $cmd->stderr_like(qr{::1 : xmt/rcv/%loss = 3/3/0%.*});
 }
 
 # fping -r tested in test-4-options-a-b.pl
@@ -82,11 +85,14 @@ $cmd->stderr_is_eq("");
 }
 
 # fping6 -S
-{
-my $cmd = Test::Command->new(cmd => "fping6 -S ::1 ::1");
-$cmd->exit_is_num(0);
-$cmd->stdout_is_eq("::1 is alive\n");
-$cmd->stderr_is_eq("");
+SKIP: {
+    if(system("/sbin/ifconfig | grep inet6") != 0) {
+        skip 'No IPv6 on this host', 3;
+    }
+    my $cmd = Test::Command->new(cmd => "fping6 -S ::1 ::1");
+    $cmd->exit_is_num(0);
+    $cmd->stdout_is_eq("::1 is alive\n");
+    $cmd->stderr_is_eq("");
 }
 
 # fping -t tested in test-4-options-a-b.pl

ci/test-14-ping-internet-hosts.pl

@@ -42,11 +42,14 @@ $cmd->stderr_is_eq("");
 }
 
 # fping6 -A -n
-{
-my $cmd = Test::Command->new(cmd => "fping6 -n -A 2001:4860:4860::8888");
-$cmd->exit_is_num(0);
-$cmd->stdout_is_eq("google-public-dns-a.google.com (2001:4860:4860::8888) is alive\n");
-$cmd->stderr_is_eq("");
+SKIP: {
+    if(system("/sbin/ifconfig | grep inet6") != 0) {
+        skip 'No IPv6 on this host', 3;
+    }
+    my $cmd = Test::Command->new(cmd => "fping6 -n -A 2001:4860:4860::8888");
+    $cmd->exit_is_num(0);
+    $cmd->stdout_is_eq("google-public-dns-a.google.com (2001:4860:4860::8888) is alive\n");
+    $cmd->stderr_is_eq("");
 }
 
 # fping -m