package dns-server

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Module Dns_trieSource

Prefix tree data structure for domain names

The key is a Domain_name, whereas the value may be any resource record. The representation is a tree, where the edges are domain name labels, and the nodes carry a resource map. Some special treatment is applied for zones, which must have a start of authority entry and a set of name servers. End of authority, also known as delegation, is supported. Aliases (canonical names, CNAME records) are also supported.

The data structure tries to preserve invariants recommended by the domain name system, such as that for any name there may either be an alias or any other record, there must be a SOA record, and multiple NS records for an authoritative zone, a resource type must have entries of the given type (no NS record for A type, the ttl for all resource records of a rrset is the same.

Abstract trie type

Sourcetype t

The type of the trie.

Sourceval pp : t Fmt.t

pp ppf t pretty prints t to ppf.

Sourceval empty : t

empty is the empty trie.

Sourceval equal : t -> t -> bool

equal a b compares a with b.

Operations to modify the trie

Sourceval insert_map : Dns.Rr_map.t Domain_name.Map.t -> t -> t

insert_map m t inserts all elements of the domain name map m into t, potentially existing are unioned with Dns.Rr_map.unionee.

Sourceval replace_map : Dns.Rr_map.t Domain_name.Map.t -> t -> t

replace_map m t replaces in the trie t all existing bindings of the domain name map m with the provided map.

Sourceval remove_map : Dns.Rr_map.t Domain_name.Map.t -> t -> t

remove_map m t removes all elements of the domain name map m from t.

Sourceval insert : 'a Domain_name.t -> 'b Dns.Rr_map.key -> 'b -> t -> t

insert n k v t inserts k, v under n in t. Existing entries are unioneed with Dns.Rr_map.union_rr.

Sourceval replace : 'a Domain_name.t -> 'b Dns.Rr_map.key -> 'b -> t -> t

replace n k v t inserts k, v under n in t. Existing entries are replaced.

Sourceval remove : 'a Domain_name.t -> 'b Dns.Rr_map.key -> 'b -> t -> t

remove k ty v t removes ty, v from t at k. Beware, this may lead to a t where the initially mentioned invariants are violated.

Sourceval remove_ty : 'a Domain_name.t -> 'b Dns.Rr_map.key -> t -> t

remove_ty k ty t removes ty from t at k. Beware, this may lead to a t where the initially mentioned invariants are violated.

Sourceval remove_all : 'a Domain_name.t -> t -> t

remove_all k t removes all entries of k in t. Beware, this may lead to a t where the initially mentioned invariants are violated.

Sourceval remove_zone : 'a Domain_name.t -> t -> t

remove_zone name t remove the zone name from t, retaining subzones (entries with Soa records). This removes as well any delegations.

Checking invariants

Sourcetype zone_check = [
  1. | `Missing_soa of [ `raw ] Domain_name.t
  2. | `Cname_other of [ `raw ] Domain_name.t
  3. | `Bad_ttl of [ `raw ] Domain_name.t * Dns.Rr_map.b
  4. | `Empty of [ `raw ] Domain_name.t * Dns.Rr_map.k
  5. | `Missing_address of [ `host ] Domain_name.t
  6. | `Soa_not_a_host of [ `raw ] Domain_name.t * string
]
Sourceval pp_zone_check : zone_check Fmt.t

pp_err ppf err pretty prints the error err.

Sourceval check : t -> (unit, zone_check) result

check t checks all invariants.

Lookup

Sourcetype e = [
  1. | `Delegation of [ `raw ] Domain_name.t * (int32 * Domain_name.Host_set.t)
  2. | `EmptyNonTerminal of [ `raw ] Domain_name.t * Dns.Soa.t
  3. | `NotAuthoritative
  4. | `NotFound of [ `raw ] Domain_name.t * Dns.Soa.t
]

The type of lookup errors.

Sourceval pp_e : e Fmt.t

pp_e ppf e pretty-prints e on ppf.

Sourceval zone : 'a Domain_name.t -> t -> ([ `raw ] Domain_name.t * Dns.Soa.t, e) result

zone k t returns either the zone and soa for k in t, or an error.

Sourceval lookup_with_cname : 'a Domain_name.t -> 'b Dns.Rr_map.key -> t -> (Dns.Rr_map.b * ([ `raw ] Domain_name.t * int32 * Domain_name.Host_set.t), e) result

lookup_with_cname k ty t finds k, ty in t. It either returns the found resource record set and authority information, a cname alias and authority information, or an error.

Sourceval lookup : 'a Domain_name.t -> 'b Dns.Rr_map.key -> t -> ('b, e) result

lookup k ty t finds k, ty in t, which may lead to an error.

Sourceval lookup_any : 'a Domain_name.t -> t -> (Dns.Rr_map.t * ([ `raw ] Domain_name.t * int32 * Domain_name.Host_set.t), e) result

lookup_any k t looks up all resource records of k in t, and returns that and the authority information.

Sourceval lookup_glue : 'a Domain_name.t -> t -> (int32 * Ipaddr.V4.Set.t) option * (int32 * Ipaddr.V6.Set.t) option

lookup_glue k t finds glue records (A, AAAA) for k in t. It ignores potential DNS invariants, e.g. that there is no surrounding zone.

Sourceval entries : 'a Domain_name.t -> t -> (Dns.Soa.t * Dns.Rr_map.t Domain_name.Map.t, e) result

entries name t returns either the SOA and all entries for the requested name, or an error.

Sourceval fold : 'a Dns.Rr_map.key -> t -> ([ `raw ] Domain_name.t -> 'a -> 'b -> 'b) -> 'b -> 'b

fold key t f acc calls f with dname value acc element in t.

Sourceval diff : 'a Domain_name.t -> Dns.Soa.t -> old:t -> t -> (Dns.Soa.t * [ `Empty | `Full of Dns.Name_rr_map.t | `Difference of Dns.Soa.t * Dns.Name_rr_map.t * Dns.Name_rr_map.t ], [> `Msg of string ]) result

diff zone soa ~old trie computes the difference of zone in old and trie, and returns either `Empty if soa is equal or newer than the one in trie, `Full (the same as entries) if zone is not present in old, or `Difference (old_soa, deleted, added). Best used with IXFR. An error occurs if zone is not present in trie.