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+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2016 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef SHRPX_DNS_TRACKER_H
+#define SHRPX_DNS_TRACKER_H
+
+#include "shrpx.h"
+
+#include <map>
+
+#include "shrpx_dual_dns_resolver.h"
+
+using namespace nghttp2;
+
+namespace shrpx {
+
+struct DNSQuery {
+ DNSQuery(StringRef host, CompleteCb cb)
+ : host(std::move(host)),
+ cb(std::move(cb)),
+ dlnext(nullptr),
+ dlprev(nullptr),
+ status(DNSResolverStatus::IDLE),
+ in_qlist(false) {}
+
+ // Host name we lookup for.
+ StringRef host;
+ // Callback function called when name lookup finished. This
+ // callback is not called if name lookup finishes within
+ // DNSTracker::resolve().
+ CompleteCb cb;
+ DNSQuery *dlnext, *dlprev;
+ DNSResolverStatus status;
+ // true if this object is in linked list ResolverEntry::qlist.
+ bool in_qlist;
+};
+
+struct ResolverEntry {
+ // Host name this entry lookups for.
+ ImmutableString host;
+ // DNS resolver. Only non-nullptr if status is
+ // DNSResolverStatus::RUNNING.
+ std::unique_ptr<DualDNSResolver> resolv;
+ // DNSQuery interested in this name lookup result. The result is
+ // notified to them all.
+ DList<DNSQuery> qlist;
+ // Use the same enum with DNSResolverStatus
+ DNSResolverStatus status;
+ // result and its expiry time
+ Address result;
+ // time point when cached result expires.
+ ev_tstamp expiry;
+};
+
+class DNSTracker {
+public:
+ DNSTracker(struct ev_loop *loop, int family);
+ ~DNSTracker();
+
+ // Lookups host name described in |dnsq|. If name lookup finishes
+ // within this function (either it came from /etc/hosts, host name
+ // is numeric, lookup result is cached, etc), it returns
+ // DNSResolverStatus::OK or DNSResolverStatus::ERROR. If lookup is
+ // successful, DNSResolverStatus::OK is returned, and |result| is
+ // filled. If lookup failed, DNSResolverStatus::ERROR is returned.
+ // If name lookup is being done background, it returns
+ // DNSResolverStatus::RUNNING. Its completion is notified by
+ // calling dnsq->cb.
+ DNSResolverStatus resolve(Address *result, DNSQuery *dnsq);
+ // Cancels name lookup requested by |dnsq|.
+ void cancel(DNSQuery *dnsq);
+ // Removes expired entries from ents_.
+ void gc();
+ // Starts GC timer.
+ void start_gc_timer();
+
+private:
+ ResolverEntry make_entry(std::unique_ptr<DualDNSResolver> resolv,
+ ImmutableString host, DNSResolverStatus status,
+ const Address *result);
+
+ void update_entry(ResolverEntry &ent, std::unique_ptr<DualDNSResolver> resolv,
+ DNSResolverStatus status, const Address *result);
+
+ void add_to_qlist(ResolverEntry &ent, DNSQuery *dnsq);
+
+ std::map<StringRef, ResolverEntry> ents_;
+ // Periodically iterates ents_, and removes expired entries to avoid
+ // excessive use of memory. Since only backend API can potentially
+ // increase memory consumption, interval could be very long.
+ ev_timer gc_timer_;
+ struct ev_loop *loop_;
+ // IP version preference.
+ int family_;
+};
+
+} // namespace shrpx
+
+#endif // SHRPX_DNS_TRACKER_H