dns.h

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#ifndef CVMFS_NETWORK_DNS_H_
#define CVMFS_NETWORK_DNS_H_

#include <stdint.h>

#include <cstdio>
#include <ctime>
#include <map>
#include <set>
#include <string>
#include <vector>

#include "duplex_cares.h"
#include "gtest/gtest_prod.h"
#include "util/atomic.h"
#include "util/prng.h"
#include "util/single_copy.h"

namespace dns {

enum Failures {
  kFailOk = 0,
  kFailInvalidResolvers,
  kFailTimeout,
  kFailInvalidHost,
  kFailUnknownHost,   
  kFailMalformed,
  kFailNoAddress,     
  kFailNotYetResolved,
  kFailOther,

  kFailNumEntries
};


enum IpPreference {
  // use system default, currently unused and mapped to IPv4
  kIpPreferSystem = 0,
  kIpPreferV4,
  kIpPreferV6,
};

inline const char *Code2Ascii(const Failures error) {
  const char *texts[kFailNumEntries + 1];
  texts[0] = "OK";
  texts[1] = "invalid resolver addresses";
  texts[2] = "DNS query timeout";
  texts[3] = "invalid host name to resolve";
  texts[4] = "unknown host name";
  texts[5] = "malformed DNS request";
  texts[6] = "no IP address for host";
  texts[7] = "internal error, not yet resolved";
  texts[8] = "unknown name resolving error";
  texts[9] = "no text";
  return texts[error];
}


std::string ExtractHost(const std::string &url);
std::string ExtractPort(const std::string &url);
std::string RewriteUrl(const std::string &url, const std::string &ip);
std::string StripIp(const std::string &decorated_ip);
std::string AddDefaultScheme(const std::string &proxy);


class Host {
  FRIEND_TEST(T_Dns, HostEquivalent);
  FRIEND_TEST(T_Dns, HostExpired);
  FRIEND_TEST(T_Dns, HostValid);
  FRIEND_TEST(T_Dns, HostExtendDeadline);
  FRIEND_TEST(T_Dns, HostBestAddresses);
  friend class Resolver;

 public:
  static Host ExtendDeadline(const Host &original, unsigned seconds_from_now);
  Host();
  Host(const Host &other);
  Host &operator= (const Host &other);
  bool IsEquivalent(const Host &other) const;
  bool IsExpired() const;
  bool IsValid() const;

  time_t deadline() const { return deadline_; }
  int64_t id() const { return id_; }
  bool HasIpv4() const { return !ipv4_addresses_.empty(); }
  bool HasIpv6() const { return !ipv6_addresses_.empty(); }
  const std::set<std::string> &ipv4_addresses() const {
    return ipv4_addresses_;
  }
  const std::set<std::string> &ipv6_addresses() const {
    return ipv6_addresses_;
  }
  const std::set<std::string> &ViewBestAddresses(IpPreference preference) const;
  const std::string &name() const { return name_; }
  Failures status() const { return status_; }

 private:
  void CopyFrom(const Host &other);

  static atomic_int64 global_id_;

  time_t deadline_;

  int64_t id_;

  std::set<std::string> ipv4_addresses_;

  std::set<std::string> ipv6_addresses_;

  std::string name_;

  Failures status_;
};


class Resolver : SingleCopy {
 public:
  static const unsigned kDefaultMinTtl = 60;

  static const unsigned kDefaultMaxTtl = 84600;

  Resolver(const bool ipv4_only,
           const unsigned retries,
           const unsigned timeout_ms);
  virtual ~Resolver() { }

  virtual bool SetResolvers(const std::vector<std::string> &resolvers) = 0;
  virtual bool SetSearchDomains(const std::vector<std::string> &domains) = 0;
  virtual void SetSystemResolvers() = 0;
  virtual void SetSystemSearchDomains() = 0;
  Host Resolve(const std::string &name);
  void ResolveMany(const std::vector<std::string> &names,
                   std::vector<Host> *hosts);

  const std::vector<std::string> &domains() const { return domains_; }
  bool ipv4_only() const { return ipv4_only_; }
  const std::vector<std::string> &resolvers() const { return resolvers_; }
  unsigned retries() const { return retries_; }
  unsigned timeout_ms() const { return timeout_ms_; }
  void set_throttle(const unsigned throttle) { throttle_ = throttle; }
  unsigned throttle() const { return throttle_; }
  void set_min_ttl(unsigned seconds) { min_ttl_ = seconds; }
  unsigned min_ttl() const { return min_ttl_; }
  void set_max_ttl(unsigned seconds) { max_ttl_ = seconds; }
  unsigned max_ttl() const { return max_ttl_; }

 protected:
  virtual void DoResolve(const std::vector<std::string> &names,
                         const std::vector<bool> &skip,
                         std::vector<std::vector<std::string> > *ipv4_addresses,
                         std::vector<std::vector<std::string> > *ipv6_addresses,
                         std::vector<Failures> *failures,
                         std::vector<unsigned> *ttls,
                         std::vector<std::string> *fqdns) = 0;
  bool IsIpv4Address(const std::string &address);
  bool IsIpv6Address(const std::string &address);

  std::vector<std::string> domains_;

  bool ipv4_only_;

  std::vector<std::string> resolvers_;

  unsigned retries_;

  unsigned timeout_ms_;

  unsigned throttle_;

  unsigned min_ttl_;

  unsigned max_ttl_;

  Prng prng_;
};


class CaresResolver : public Resolver {
  friend class NormalResolver;
 public:
  static const unsigned kMaxAddresses = 16;

  static CaresResolver *Create(const bool ipv4_only,
                               const unsigned retries,
                               const unsigned timeout_ms);
  virtual ~CaresResolver();

  virtual bool SetResolvers(const std::vector<std::string> &resolvers);
  virtual bool SetSearchDomains(const std::vector<std::string> &domains);
  virtual void SetSystemResolvers();
  virtual void SetSystemSearchDomains();

 protected:
  CaresResolver(const bool ipv4_only,
                const unsigned retries,
                const unsigned timeout_ms);
  virtual void DoResolve(const std::vector<std::string> &names,
                         const std::vector<bool> &skip,
                         std::vector<std::vector<std::string> > *ipv4_addresses,
                         std::vector<std::vector<std::string> > *ipv6_addresses,
                         std::vector<Failures> *failures,
                         std::vector<unsigned> *ttls,
                         std::vector<std::string> *fqdns);

 private:
  void WaitOnCares();
  ares_channel *channel_;
  char *lookup_options_;
  std::vector<std::string> system_resolvers_;
  std::vector<std::string> system_domains_;
};


class HostfileResolver : public Resolver {
  friend class NormalResolver;
 public:
  static HostfileResolver *Create(const std::string &path, bool ipv4_only);
  virtual ~HostfileResolver();

  virtual bool SetResolvers(const std::vector<std::string> & /* resolvers */) {
    return true;
  }
  virtual bool SetSearchDomains(const std::vector<std::string> &domains);
  virtual void SetSystemResolvers() { }
  virtual void SetSystemSearchDomains();

 protected:
  explicit HostfileResolver(const bool ipv4_only);
  virtual void DoResolve(const std::vector<std::string> &names,
                         const std::vector<bool> &skip,
                         std::vector<std::vector<std::string> > *ipv4_addresses,
                         std::vector<std::vector<std::string> > *ipv6_addresses,
                         std::vector<Failures> *failures,
                         std::vector<unsigned> *ttls,
                         std::vector<std::string> *fqdns);

 private:
  struct HostEntry {
    std::vector<std::string> ipv4_addresses;
    std::vector<std::string> ipv6_addresses;
  };
  static const int kIpMaxLength = 45;
  static const int kHostnameMaxLength = 253;
  void ParseHostFile();
  std::map<std::string, HostEntry> host_map_;

  FILE *fhosts_;
};


class NormalResolver : public Resolver {
  FRIEND_TEST(T_Dns, NormalResolverConstruct);

 public:
  static NormalResolver *Create(const bool ipv4_only,
                                const unsigned retries,
                                const unsigned timeout_ms);
  virtual bool SetResolvers(const std::vector<std::string> &resolvers);
  virtual bool SetSearchDomains(const std::vector<std::string> &domains);
  virtual void SetSystemResolvers();
  virtual void SetSystemSearchDomains();
  virtual ~NormalResolver();

 protected:
  virtual void DoResolve(const std::vector<std::string> &names,
                         const std::vector<bool> &skip,
                         std::vector<std::vector<std::string> > *ipv4_addresses,
                         std::vector<std::vector<std::string> > *ipv6_addresses,
                         std::vector<Failures> *failures,
                         std::vector<unsigned> *ttls,
                         std::vector<std::string> *fqdns);
  NormalResolver();

 private:
  CaresResolver *cares_resolver_;
  HostfileResolver *hostfile_resolver_;
};

}  // namespace dns

#endif  // CVMFS_NETWORK_DNS_H_