+ do_esp_policy $ns $me $remote $lnet $rnet
+}
+
+# add policies with different netmasks, to make sure kernel carries
+# the policies contained within new netmask over when search tree is
+# re-built.
+# peer netns that are supposed to be encapsulated via esp have addresses
+# in the 10.0.1.0/24 and 10.0.2.0/24 subnets, respectively.
+#
+# Adding a policy for '10.0.1.0/23' will make it necessary to
+# alter the prefix of 10.0.1.0 subnet.
+# In case new prefix overlaps with existing node, the node and all
+# policies it carries need to be merged with the existing one(s).
+#
+# Do that here.
+do_overlap()
+{
+ local ns=$1
+
+ # adds new nodes to tree (neither network exists yet in policy database).
+ ip -net $ns xfrm policy add src 10.1.0.0/24 dst 10.0.0.0/24 dir fwd priority 200 action block
+
+ # adds a new node in the 10.0.0.0/24 tree (dst node exists).
+ ip -net $ns xfrm policy add src 10.2.0.0/24 dst 10.0.0.0/24 dir fwd priority 200 action block
+
+ # adds a 10.2.0.0/23 node, but for different dst.
+ ip -net $ns xfrm policy add src 10.2.0.0/23 dst 10.0.1.0/24 dir fwd priority 200 action block
+
+ # dst now overlaps with the 10.0.1.0/24 ESP policy in fwd.
+ # kernel must 'promote' existing one (10.0.0.0/24) to 10.0.0.0/23.
+ # But 10.0.0.0/23 also includes existing 10.0.1.0/24, so that node
+ # also has to be merged too, including source-sorted subtrees.
+ # old:
+ # 10.0.0.0/24 (node 1 in dst tree of the bin)
+ # 10.1.0.0/24 (node in src tree of dst node 1)
+ # 10.2.0.0/24 (node in src tree of dst node 1)
+ # 10.0.1.0/24 (node 2 in dst tree of the bin)
+ # 10.0.2.0/24 (node in src tree of dst node 2)
+ # 10.2.0.0/24 (node in src tree of dst node 2)
+ #
+ # The next 'policy add' adds dst '10.0.0.0/23', which means
+ # that dst node 1 and dst node 2 have to be merged including
+ # the sub-tree. As no duplicates are allowed, policies in
+ # the two '10.0.2.0/24' are also merged.
+ #
+ # after the 'add', internal search tree should look like this:
+ # 10.0.0.0/23 (node in dst tree of bin)
+ # 10.0.2.0/24 (node in src tree of dst node)
+ # 10.1.0.0/24 (node in src tree of dst node)
+ # 10.2.0.0/24 (node in src tree of dst node)
+ #
+ # 10.0.0.0/24 and 10.0.1.0/24 nodes have been merged as 10.0.0.0/23.
+ ip -net $ns xfrm policy add src 10.1.0.0/24 dst 10.0.0.0/23 dir fwd priority 200 action block