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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 <unordered_map>
#include <chrono>
#include "shrpx_dual_dns_resolver.h"
using namespace nghttp2;
namespace shrpx {
struct DNSQuery {
DNSQuery(std::string_view 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.
std::string_view 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.
std::chrono::steady_clock::time_point 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::unordered_map<std::string_view, 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 // !defined(SHRPX_DNS_TRACKER_H)