scoutfs: add portscan test

Signed-off-by: Zach Brown <zab@versity.com>

tests/golden/portscan

@@ -0,0 +1,3 @@
+== make sure unknown disconnect doesn't shut down server
+should be leader: 1
+should still be leader: 1

tests/sequence

@@ -65,4 +65,5 @@ block-stale-reads.sh
 freed-list-wedge.sh
 inode-deletion.sh
 renameat2-noreplace.sh
+portscan.sh
 xfstests.sh

tests/tests/portscan.sh

@@ -0,0 +1,31 @@
+#
+# Make sure the server ignores connections that aren't participating.
+#
+
+t_require_commands nc
+
+echo "== make sure unknown disconnect doesn't shut down server"
+# get server addr [1] and port [1]
+sv=$(t_server_nr)
+addrs=($(grep "peer 0.0.0.0" $(t_debugfs_path $sv)/connections |  \
+	awk -F"[: ]" '{print $2,$3}'))
+
+# verify that the server is leader and record its term
+echo "should be leader: $(cat $(t_sysfs_path $sv)/quorum/is_leader)"
+before=$(awk '($1 == "term") { print $2 }' < $(t_sysfs_path $sv)/quorum/status)
+
+# send junk
+echo "  " | nc ${addrs[0]} ${addrs[1]}
+
+# make sure the server is still leader with the same term
+echo "should still be leader: $(cat $(t_sysfs_path $sv)/quorum/is_leader)"
+after=$(awk '($1 == "term") { print $2 }' < $(t_sysfs_path $sv)/quorum/status)
+
+if [ -z "$before" -o -z "$after" ]; then
+	echo "couldn't find terms: before '$before', or after '$after'"
+fi
+if [ "$before" != "$after" ]; then
+	echo "term before $before != term after $after"
+fi
+
+t_pass