138 lines
3.1 KiB
C++
138 lines
3.1 KiB
C++
/*
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* \brief Utilities for handling server-side session policies
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* \author Norman Feske
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* \date 2011-09-13
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*/
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/*
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* Copyright (C) 2011-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__OS__SESSION_POLICY_H_
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#define _INCLUDE__OS__SESSION_POLICY_H_
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#include <util/arg_string.h>
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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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}
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class Genode::Session_label
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{
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public:
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enum { MAX_LEN = 128 };
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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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};
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/**
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* Query server-side policy for a session request
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*/
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class Genode::Session_policy : public Xml_node
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{
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public:
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/**
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* Exception type
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*/
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class No_policy_defined { };
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private:
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/**
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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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/**
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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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{
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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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for (int i = 0;; i++, policy = policy.next()) {
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if (!policy.has_type("policy"))
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continue;
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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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if (!_label_matches(label, policy_label)
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|| strlen(policy_label) < label_len)
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continue;
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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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if (best_match != -1)
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return config()->xml_node().sub_node(best_match);
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throw No_policy_defined();
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}
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public:
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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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*
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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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*
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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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*/
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explicit Session_policy(Session_label const &label)
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: Xml_node(_query_policy(label)) { }
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};
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#endif /* _INCLUDE__OS__SESSION_POLICY_H_ */
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