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os: generalize Session_label, Session_policy
The utilities in os/session_policy.h used to be tailored for the matching of session arguments against a server-side policy configuration. However, the policy-matching part is useful in other situations, too. This patch removes the tight coupling with the session-argument parsing (via Arg_string) and the hard-wired use of 'Genode::config()'. To make the utilities more versatile, the 'Session_label' has become a 'Genode::String' (at the time when we originally introduced the 'Session_label', there was no 'Genode::String'). The parsing of the session arguments happens in the constructor of this special 'String'. The constructor of 'Session_policy' now takes a 'Genode::String' as argument. So it can be used with the 'Session_label' but also with other 'String' types. Furthermore, the implicit use of 'Genode::config()' can be overridden by explicitly specifying the config node as an argument.
This commit is contained in:
Norman Feske
Christian Helmuth
parent
1f941d1c87
commit
dce6e14e3e
@ -18,38 +18,33 @@
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#include <os/config.h>
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namespace Genode {
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class Session_label;
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class Session_policy;
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struct Session_label;
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class Session_policy;
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}
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class Genode::Session_label
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struct Genode::Session_label : String<128>
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{
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public:
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Session_label() { }
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enum { MAX_LEN = 128 };
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/**
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* Constructor
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*
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* \param args session arguments as null-terminated string
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*
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* The constructor extracts the label from the supplied session-argument
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* string.
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*/
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explicit Session_label(char const *args)
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{
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typedef String<128> String;
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private:
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char _buf[MAX_LEN];
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public:
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Session_label() { _buf[0] = 0; }
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/**
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* Constructor
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*
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* \param args session arguments as null-terminated string
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*/
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explicit Session_label(char const *args)
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{
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Arg_string::find_arg(args, "label").string(_buf, sizeof(_buf),
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"<undefined>");
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}
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char const *string() const { return _buf; }
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char buf[String::capacity()];
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Arg_string::find_arg(args, "label").string(buf, sizeof(buf),
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"<undefined>");
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*static_cast<String *>(this) = String(buf);
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}
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};
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@ -71,41 +66,43 @@ class Genode::Session_policy : public Xml_node
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* Returns true if the start of the label matches the specified
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* match string
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*/
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static bool _label_matches(Session_label const &label, char const *match) {
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return strcmp(label.string(), match, strlen(match)) == 0; }
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static bool _label_matches(char const *label, char const *match) {
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return strcmp(label, match, strlen(match)) == 0; }
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/**
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* Query session policy from session label
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*/
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static Xml_node _query_policy(Session_label const &label)
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static Xml_node _query_policy(char const *label, Xml_node config)
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{
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/* find index of policy node that matches best */
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int best_match = -1;
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try {
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unsigned label_len = 0;
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Xml_node policy = config()->xml_node().sub_node();
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/*
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* Find policy node that matches best
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*/
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Xml_node best_match("<none/>");
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for (int i = 0;; i++, policy = policy.next()) {
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unsigned label_len = 0;
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if (!policy.has_type("policy"))
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continue;
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/*
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* Functor to be applied to each policy node
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*/
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auto lambda = [&] (Xml_node policy) {
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/* label attribute from policy node */
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char policy_label[Session_label::MAX_LEN];
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policy.attribute("label").value(policy_label,
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sizeof(policy_label));
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/* label attribute from policy node */
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char policy_label[Session_label::capacity()];
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policy.attribute("label").value(policy_label,
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sizeof(policy_label));
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if (!_label_matches(label, policy_label)
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|| strlen(policy_label) < label_len)
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continue;
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if (!_label_matches(label, policy_label)
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|| strlen(policy_label) < label_len)
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return;
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label_len = strlen(policy_label);
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best_match = i;
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}
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} catch (...) { }
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label_len = strlen(policy_label);
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best_match = policy;
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};
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if (best_match != -1)
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return config()->xml_node().sub_node(best_match);
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config.for_each_sub_node("policy", lambda);
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if (!best_match.has_type("none"))
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return best_match;
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throw No_policy_defined();
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}
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@ -115,23 +112,28 @@ class Genode::Session_policy : public Xml_node
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/**
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* Constructor
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*
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* \param args session arguments
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* \param label label used as the selector of a policy
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* \param config XML node that contains the policies as sub nodes,
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* using the component's top-level config node by
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* default
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*
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* \throw No_policy_defined if the server configuration has no
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* policy defined for the session
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* request
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* \throw No_policy_defined the server configuration has no
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* policy defined for the specified label
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*
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* On construction, the 'Session_policy' looks up the 'policy' XML
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* node that matches the label provided as argument. The
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* server-side policies are defined in one or more policy subnodes
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* of the server's 'config' node. Each policy node has a label
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* attribute. If the policy label matches the first part of the
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* label delivered as session argument, the policy matches. If
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* multiple policies match, the one with the largest label is
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* selected.
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* On construction, the 'Session_policy' looks up the 'policy' XML node
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* that matches the label provided as argument. The server-side
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* policies are defined in one or more policy subnodes of the server's
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* 'config' node. Each policy node has a label attribute. If the policy
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* label matches the first part of the label as delivered as session
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* argument, the policy matches. If multiple policies match, the one
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* with the longest label is selected.
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*/
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explicit Session_policy(Session_label const &label)
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: Xml_node(_query_policy(label)) { }
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template <size_t N>
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explicit Session_policy(String<N> const &label,
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Xml_node config = Genode::config()->xml_node())
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:
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Xml_node(_query_policy(label.string(), config))
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{ }
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};
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#endif /* _INCLUDE__OS__SESSION_POLICY_H_ */
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@ -69,7 +69,7 @@ class Session : public Session_list::Element
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* Append label separator to match selectors with a trailing
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* separator.
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*/
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char label[Genode::Session_label::MAX_LEN + 4];
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char label[Genode::Session_label::capacity() + 4];
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Genode::snprintf(label, sizeof(label), "%s ->", _label.string());
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return Genode::strcmp(label, selector,
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Genode::strlen(selector)) == 0;
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