This module provides bindings to GNU ADNS, a domain name resolver library written in C. Its source code, among other things, is available at http://www.gnu.org/software/adns/.

You will most likely not need this module directly; Network.DNS provides a much nicer interface from the Haskell world; this module contains mostly marshaling code.

Original definition:

    typedef struct {
      int len;
      union {
        struct sockaddr sa;
        struct sockaddr_in inet;
      } addr;
    } adns_rr_addr;

Note: Anything but sockaddr_in will cause peek to call fail, when marshaling this structure. poke is not defined.

Similar to adnsInit, but reads the resolver configuration from a string rather than from /etc/resolv.conf. Supported are the usual commands: nameserver, search, domain, sortlist, and options.

Additionally, these non-standard commands may be used:

• clearnameservers: Clears the list of nameservers.
• include filename: The specified file will be read.

Find out which file descriptors ADNS is interested in and when it would like to be able to time things out. This is in a form suitable for use with poll.

On entry, fds should point to at least *nfds_io structs. ADNS will fill up to that many structs with information for poll, and record in *nfds_io how many entries it actually used. If the array is too small, *nfds_io will be set to the number required and adnsBeforePoll will return eRANGE.

You may call adnsBeforePoll with fds==nullPtr and *nfds_io==0, in which case ADNS will fill in the number of fds that it might be interested in into *nfds_io and return either 0 (if it is not interested in any fds) or eRANGE (if it is).

Note that (unless now is 0) ADNS may acquire additional fds from one call to the next, so you must put adns_beforepoll in a loop, rather than assuming that the second call (with the buffer size requested by the first) will not return eRANGE.

ADNS only ever sets PollIn, PollOut and PollPri in its Pollfd structs, and only ever looks at those bits. PollPri is required to detect TCP Urgent Data (which should not be used by a DNS server) so that ADNS can know that the TCP stream is now useless.

In any case, *timeout_io should be a timeout value as for poll, which ADNS will modify downwards as required. If the caller does not plan to block, then *timeout_io should be 0 on entry. Alternatively, timeout_io may be 0.

adnsBeforePoll will return 0 on success, and will not fail for any reason other than the fds buffer being too small (ERANGE).

This call will never actually do any I/O. If you supply the current time it will not change the fds that ADNS is using or the timeouts it wants.

In any case this call won't block.

Map a Status code to a human-readable error description. For example:

    *ADNS> adnsStrerror sNXDOMAIN >>= print
    "No such domain"

Use this function with great care: It will crash the process when called with a status code that ADNS doesn't know about. So use it only to print values you got from the resolver!