6575856624
By splitting Session_policy into two classes, we make it more flexible. Originally, the constructor accepted solely an args string, which made it unusable for situations where we already have extracted the session label (e.g., stored in the session meta data of a server). Now, the extraction of the label from the args string is performed by the new Session_label class instead, which, in turn, can be passed to the constructor of Session_policy. This change causes a minor API change. The following code Session_policy policy(session_args); Must be turned into Session_label label(session_args); Session_policy policy(label);
133 lines
3.1 KiB
C++
133 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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{
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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 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 attribtute 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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* note 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. The if 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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}
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#endif /* _INCLUDE__OS__SESSION_POLICY_H_ */
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