Adding security groups :lock:
diff --git a/openstack/networking/v2/extensions/security/doc.go b/openstack/networking/v2/extensions/security/doc.go
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+// Package security contains functionality to work with security group and
+// security group rules Neutron resources.
+//
+// Security groups and security group rules allows administrators and tenants
+// the ability to specify the type of traffic and direction (ingress/egress)
+// that is allowed to pass through a port. A security group is a container for
+// security group rules.
+//
+// When a port is created in Networking it is associated with a security group.
+// If a security group is not specified the port is associated with a 'default'
+// security group. By default, this group drops all ingress traffic and allows
+// all egress. Rules can be added to this group in order to change the behaviour.
+//
+// The basic characteristics of Neutron Security Groups are:
+//
+// For ingress traffic (to an instance)
+// - Only traffic matched with security group rules are allowed.
+// - When there is no rule defined, all traffic are dropped.
+//
+// For egress traffic (from an instance)
+// - Only traffic matched with security group rules are allowed.
+// - When there is no rule defined, all egress traffic are dropped.
+// - When a new security group is created, rules to allow all egress traffic
+// are automatically added.
+//
+// "default security group" is defined for each tenant.
+// - For the default security group a rule which allows intercommunication
+// among hosts associated with the default security group is defined by default.
+// - As a result, all egress traffic and intercommunication in the default
+// group are allowed and all ingress from outside of the default group is
+// dropped by default (in the default security group).
+package security