loc_discover_latest

Name

loc_discover_latest_version - Find out when the latest database has been published

Synopsis

#include <libloc/database.h>
#include <libloc/resolv.h>

int loc_discover_latest_version(struct loc_ctx* ctx, unsigned int version,
        time_t* t);

Description

A new IPFire Location Database is being published every day. Whenever that happens, the time it has been created is being published in the DNS, as a TXT record of \_v1.\_db.location.ipfire.org, where 1 is the version of the format.

loc_discover_latest_version() looks it up, and stores the time in t. If it is not newer than what loc_database_new(3) says the database has been created at, there is no need to download anything. This is how location(1) checks for updates, which saves downloading the database when nothing has changed.

version is the version of the database format, which is LOC_DATABASE_VERSION_LATEST for databases that have been created by this version of libloc.

The lookup uses the resolver of the system (see resolver(3)). libloc does not check DNSSEC signatures itself, which is up to the resolver. The answer only tells whether it is worth downloading anything; a database that has been downloaded must still be checked with loc_database_verify(3).

Return Value

Zero is returned on success. On error, a negative error number (see errno(3)) is returned: -EAGAIN if the DNS could not be reached and it is worth trying again later, -ENOENT if there is no such record, -EBADMSG if the answer could not be understood, or -EIO for any other problem. errno itself is not being set.

Example

time_t t = 0;

int r = loc_discover_latest_version(ctx, LOC_DATABASE_VERSION_LATEST, &t);
if (r == 0 && t > loc_database_created_at(db))
        printf("There is a new database\n");

Authors

Michael Tremer