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libmaxminddb(3) libmaxminddb(3)
NAME
libmaxminddb - a library for working with MaxMind DB files
SYNOPSIS
#include <maxminddb.h>
int MMDB_open(
const char *const filename,
uint32_t flags,
MMDB_s *const mmdb);
void MMDB_close(MMDB_s *const mmdb);
MMDB_lookup_result_s MMDB_lookup_string(
MMDB_s *const mmdb,
const char *const ipstr,
int *const gai_error,
int *const mmdb_error);
MMDB_lookup_result_s MMDB_lookup_sockaddr(
MMDB_s *const mmdb,
const struct sockaddr *const
sockaddr,
int *const mmdb_error);
int MMDB_get_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
...);
int int MMDB_vget_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
va_list va_path);
int MMDB_aget_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
const char *const *const path);
int MMDB_get_entry_data_list(
MMDB_entry_s *start,
MMDB_entry_data_list_s **const entry_data_list);
void MMDB_free_entry_data_list(
MMDB_entry_data_list_s *const entry_data_list);
int MMDB_get_metadata_as_entry_data_list(
MMDB_s *const mmdb,
MMDB_entry_data_list_s **const entry_data_list);
int MMDB_dump_entry_data_list(
FILE *const stream,
MMDB_entry_data_list_s *const entry_data_list,
int indent);
int MMDB_read_node(
MMDB_s *const mmdb,
uint32_t node_number,
MMDB_search_node_s *const node);
const char *MMDB_lib_version(void);
const char *MMDB_strerror(int error_code);
typedef struct MMDB_lookup_result_s {
bool found_entry;
MMDB_entry_s entry;
uint16_t netmask;
} MMDB_lookup_result_s;
typedef struct MMDB_entry_data_s {
bool has_data;
union {
uint32_t pointer;
const char *utf8_string;
double double_value;
const uint8_t *bytes;
uint16_t uint16;
uint32_t uint32;
int32_t int32;
uint64_t uint64;
{mmdb_uint128_t or uint8_t[16]} uint128;
bool boolean;
float float_value;
};
...
uint32_t data_size;
uint32_t type;
} MMDB_entry_data_s;
typedef struct MMDB_entry_data_list_s {
MMDB_entry_data_s entry_data;
struct MMDB_entry_data_list_s *next;
} MMDB_entry_data_list_s;
DESCRIPTION
The libmaxminddb library provides functions for working MaxMind DB
files. See http://maxmind.github.io/MaxMind-DB/ for the MaxMind DB
format specification. The database and results are all represented by
different data structures. Databases are opened by calling
MMDB_open(). You can look up IP addresses as a string with
MMDB_lookup_string() or as a pointer to a sockaddr structure with
MMDB_lookup_sockaddr().
If the lookup finds the IP address in the database, it returns a
MMDB_lookup_result_s structure. If that structure indicates that the
database has data for the IP, there are a number of functions that can
be used to fetch that data. These include MMDB_get_value() and
MMDB_get_entry_data_list(). See the function documentation below for
more details.
When you are done with the database handle you should call
MMDB_close().
All publicly visible functions, structures, and macros begin with
"MMDB_".
DATA STRUCTURES
All data structures exported by this library's maxminddb.h header are
typedef'd in the form typedef struct foo_s { ... } foo_s so you can
refer to them without the struct prefix.
This library provides the following data structures:
MMDB_s
This is the handle for a MaxMind DB file. We only document some of
this structure's fields intended for public use. All other fields are
subject to change and are intended only for internal use.
typedef struct MMDB_s {
uint32_t flags;
const char *filename;
...
MMDB_metadata_s metadata;
} MMDB_s;
o uint32_t flags - the flags this database was opened with. See the
MMDB_open() documentation for more details.
o const char *filename - the name of the file which was opened, as
passed to MMDB_open().
o MMDB_metadata_s metadata - the metadata for the database.
MMDB_metadata_s and MMDB_description_s
This structure can be retrieved from the MMDB_s structure. It contains
the metadata read from the database file. Note that you may find it
more convenient to access this metadata by calling
MMDB_get_metadata_as_entry_data_list() instead.
typedef struct MMDB_metadata_s {
uint32_t node_count;
uint16_t record_size;
uint16_t ip_version;
const char *database_type;
struct {
size_t count;
const char **names;
} languages;
uint16_t binary_format_major_version;
uint16_t binary_format_minor_version;
uint64_t build_epoch;
struct {
size_t count;
MMDB_description_s **descriptions;
} description;
} MMDB_metadata_s;
typedef struct MMDB_description_s {
const char *language;
const char *description;
} MMDB_description_s;
These structures should be mostly self-explanatory.
The ip_version member should always be 4 or 6. The
binary_format_major_version should always be 2.
There is no requirement that the database metadata include languages or
descriptions, so the count for these parts of the metadata can be zero.
All of the other MMDB_metadata_s fields should be populated.
MMDB_lookup_result_s
This structure is returned as the result of looking up an IP address.
typedef struct MMDB_lookup_result_s {
bool found_entry;
MMDB_entry_s entry;
uint16_t netmask;
} MMDB_lookup_result_s;
If the found_entry member is false then the other members of this
structure do not contain meaningful values. Always check that
found_entry is true first.
The entry member is used to look up the data associated with the IP
address.
The netmask member tells you what subnet the IP address belongs to in
this database. For example, if you look up the address 1.1.1.1 in an
IPv4 database and the returned netmask is 16, then the address is part
of the 1.1.1.0/16 subnet.
MMDB_result_s
You don't really need to dig around in this structure. You'll get this
from a MMDB_lookup_result_s structure and pass it to various functions.
MMDB_entry_data_s
This structure is used to return a single data section entry for an IP.
These entries can in turn point to other entries, as is the case for
things like maps and arrays. Some members of this structure are not
documented as they are only for internal use.
typedef struct MMDB_entry_data_s {
bool has_data;
union {
uint32_t pointer;
const char *utf8_string;
double double_value;
const uint8_t *bytes;
uint16_t uint16;
uint32_t uint32;
int32_t int32;
uint64_t uint64;
{mmdb_uint128_t or uint8_t[16]} uint128;
bool boolean;
float float_value;
};
...
uint32_t data_size;
uint32_t type;
} MMDB_entry_data_s;
The has_data member is true if data was found for a given lookup. See
MMDB_get_value() for more details. If this member is false then none
of the other values in the structure are meaningful.
The union at the beginning of the structure defines the actual data.
To determine which union member is populated you should look at the
type member. The pointer member of the union should never be populated
in any data returned by the API. Pointers should always be resolved
internally.
The data_size member is only relevant for utf8_string and bytes data.
utf8_string is not null terminated and data_size must be used to
determine its length.
The type member can be compared to one of the MMDB_DTYPE_* macros.
128-bit Integers
The handling of uint128 data depends on how your platform supports
128-bit integers, if it does so at all. With GCC 4.4 and 4.5 we can
write unsigned int __attribute__ ((__mode__ (TI))). With newer
versions of GCC (4.6+) and clang (3.2+) we can simply write "unsigned
__int128".
In order to work around these differences, this library defines an
mmdb_uint128_t type. This type is defined in the maxminddb.h header so
you can use it in your own code.
With older compilers, we can't use an integer so we instead use a 16
byte array of uint8_t values. This is the raw data from the database.
This library provides a public macro MMDB_UINT128_IS_BYTE_ARRAY macro.
If this is true (1), then uint128 values are returned as a byte array,
if it is false then they are returned as a mmdb_uint128_t integer.
Data Type Macros
This library provides a macro for every data type defined by the
MaxMind DB spec.
o MMDB_DATA_TYPE_UTF8_STRING
o MMDB_DATA_TYPE_DOUBLE
o MMDB_DATA_TYPE_BYTES
o MMDB_DATA_TYPE_UINT16
o MMDB_DATA_TYPE_UINT32
o MMDB_DATA_TYPE_MAP
o MMDB_DATA_TYPE_INT32
o MMDB_DATA_TYPE_UINT64
o MMDB_DATA_TYPE_UINT128
o MMDB_DATA_TYPE_ARRAY
o MMDB_DATA_TYPE_BOOLEAN
o MMDB_DATA_TYPE_FLOAT
There are also a few types that are for internal use only:
o MMDB_DATA_TYPE_EXTENDED
o MMDB_DATA_TYPE_POINTER
o MMDB_DATA_TYPE_CONTAINER
o MMDB_DATA_TYPE_END_MARKER
If you see one of these in returned data then something has gone very
wrong. The database is damaged or was generated incorrectly or there
is a bug in the libmaxminddb code.
Pointer Values and MMDB_close()
The utf8_string, bytes, and (maybe) the uint128 members of this
structure are all pointers directly into the database's data section.
This can either be a malloc'd or mmap'd block of memory. In either
case, these pointers will become invalid after MMDB_close() is called.
If you need to refer to this data after that time you should copy the
data with an appropriate function (strdup, memcpy, etc.).
MMDB_entry_data_list_s
This structure encapsulates a linked list of MMDB_entry_data_s
structures.
typedef struct MMDB_entry_data_list_s {
MMDB_entry_data_s entry_data;
struct MMDB_entry_data_list_s *next;
} MMDB_entry_data_list_s;
This structure lets you look at entire map or array data entry by
iterating over the linked list.
MMDB_search_node_s
This structure encapsulates the two records in a search node. This is
really only useful if you want to write code that iterates over the
entire search tree as opposed to looking up a specific IP address.
typedef struct MMDB_search_node_s {
uint64_t left_record;
uint64_t right_record;
} MMDB_search_node_s;
STATUS CODES
This library returns (or populates) status codes for many functions.
These status codes are:
o MMDB_SUCCESS - everything worked
o MMDB_FILE_OPEN_ERROR - there was an error trying to open the MaxMind
DB file.
o MMDB_IO_ERROR - an IO operation failed. Check errno for more
details.
o MMDB_CORRUPT_SEARCH_TREE_ERROR - looking up an IP address in the
search tree gave us an impossible result. The database is damaged or
was generated incorrectly or there is a bug in the libmaxminddb code.
o MMDB_INVALID_METADATA_ERROR - something in the database is wrong.
This includes missing metadata keys as well as impossible values
(like an ip_version of 7).
o MMDB_UNKNOWN_DATABASE_FORMAT_ERROR - The database metadata indicates
that it's major version is not 2. This library can only handle major
version 2.
o MMDB_OUT_OF_MEMORY_ERROR - a memory allocation call (malloc, etc.)
failed.
o MMDB_INVALID_DATA_ERROR - an entry in the data section contains
invalid data. For example, a uint16 field is claiming to be more
than 2 bytes long. The database is probably damaged or was generated
incorrectly.
o MMDB_INVALID_LOOKUP_PATH_ERROR - The lookup path passed to
MMDB_get_value, MMDB_vget_value, or MMDB_aget_value contains an array
offset that is negative integer or an integer larger than LONG_MAX.
o MMDB_LOOKUP_PATH_DOES_NOT_MATCH_DATA_ERROR - The lookup path passed
to MMDB_get_value,MMDB_vget_value, or MMDB_aget_value does not match
the data structure for the entry. There are number of reasons this
can happen. The lookup path could include a key not in a map. The
lookup path could include an array index larger than an array. It
can also happen when the path expect to find a map or array where
none exist.
All status codes should be treated as int values.
MMDB_strerror()
const char *MMDB_strerror(int error_code)
This function takes a status code and returns an English string
explaining the status.
FUNCTIONS
This library provides the following exported functions:
MMDB_open()
int MMDB_open(
const char *const filename,
uint32_t flags,
MMDB_s *const mmdb);
This function opens a handle to a MaxMind DB file. Its return value is
a status code as defined above. Always check this call's return value.
MMDB_s mmdb;
int status =
MMDB_open("/path/to/file.mmdb", MMDB_MODE_MMAP, &mmdb);
if (MMDB_SUCCESS != status) { ... }
...
MMDB_close(&mmdb);
The MMDB_s structure you pass in can be on the stack or allocated from
the heap. However, if the open is successful it will contain
heap-allocated data, so you need to close it with MMDB_close(). If the
status returned is not MMDB_SUCCESS then this library makes sure that
all allocated memory is freed before returning.
The flags currently provided are:
o MMDB_MODE_MMAP - open the database with mmap().
Passing in other values for flags may yield unpredictable results. In
the future we may add additional flags that you can bitwise-or together
with the mode, as well as additional modes.
You can also pass 0 as the flags value in which case the database will
be opened with the default flags. However, these defaults may change
in future releases. The current default is MMDB_MODE_MMAP.
MMDB_close()
void MMDB_close(MMDB_s *const mmdb);
This frees any allocated or mmap'd memory that is held from the MMDB_s
structure. It does not free the memory allocated for the structure
itself! If you allocated the structure from the heap then you are
responsible for freeing it.
MMDB_lookup_string()
MMDB_lookup_result_s MMDB_lookup_string(
MMDB_s *const mmdb,
const char *const ipstr,
int *const gai_error,
int *const mmdb_error);
This function looks up an IP address that is passed in as a
null-terminated string. Internally it calls getaddrinfo() to resolve
the address into a binary form. It then calls MMDB_lookup_sockaddr()
to look the address up in the database. If you have already resolved
an address you can call MMDB_lookup_sockaddr() directly, rather than
resolving the address twice.
int gai_error, mmdb_error;
MMDB_lookup_result_s result =
MMDB_lookup_string(mmdb, "1.2.3.4", &gai_error, &mmdb_error);
if (0 != gai_error) { ... }
if (MMDB_SUCCESS != mmdb_error) { ... }
if (result.found_entry) { ... }
This function always returns an MMDB_lookup_result_s structure, but you
should also check the gai_error and mmdb_error parameters. If either
of these indicates an error then the returned structure is meaningless.
If no error occurred you still need to make sure that the found_entry
member in the returned result is true. If it's not, this means that
the IP address does not have an entry in the database.
This function will work with IPv4 addresses even when the database
contains data for both IPv4 and IPv6 addresses. The IPv4 address will
be looked up as '::xxx.xxx.xxx.xxx' rather than being remapped to the
::ffff:xxx.xxx.xxx.xxx block allocated for IPv4-mapped IPv6 addresses.
If you pass an IPv6 address to a database with only IPv4 data then the
found_entry member will be false, but the mmdb_error status will still
be MMDB_SUCCESS.
MMDB_lookup_sockaddr()
MMDB_lookup_result_s MMDB_lookup_sockaddr(
MMDB_s *const mmdb,
const struct sockaddr *const
sockaddr,
int *const mmdb_error);
This function looks up an IP address that has already been resolved by
getaddrinfo().
Other than not calling getaddrinfo() itself, this function is identical
to the MMDB_lookup_string() function.
int mmdb_error;
MMDB_lookup_result_s result =
MMDB_lookup_sockaddr(mmdb, address->ai_addr, &mmdb_error);
if (MMDB_SUCCESS != mmdb_error) { ... }
if (result.found_entry) { ... }
Data Lookup Functions
There are three functions for looking up data associated with an IP
address.
int MMDB_get_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
...);
int int MMDB_vget_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
va_list va_path);
int MMDB_aget_value(
MMDB_entry_s *const start,
MMDB_entry_data_s *const entry_data,
const char *const *const path);
The three functions allow three slightly different calling styles, but
they all do the same thing.
The first parameter is an MMDB_entry_s value. In most cases this will
come from the MMDB_lookup_result_s value returned by
MMDB_lookup_string() or MMDB_lookup_sockaddr().
The second parameter is a reference to an MMDB_entry_data_s structure.
This will be populated with the data that is being looked up, if any is
found. If nothing is found, then the has_data member of this structure
will be false. If has_data is true then you can look at the data_type
member.
The final parameter is a lookup path. The path consists of a set of
strings representing either map keys (e.g, "city") or array indexes
(e.g., "0", "1") to use in the lookup. This allow you to navigate a
complex data structure. For example, given this example:
{
"names": {
"en": "Germany",
"de": "Deutschland"
},
"cities": [ "Berlin", "Frankfurt" ]
}
We could look up the English name with this code:
MMDB_lookup_result_s result =
MMDB_lookup_sockaddr(mmdb, address->ai_addr, &mmdb_error);
MMDB_entry_data_s entry_data;
int status =
MMDB_get_value(&result.entry, &entry_data,
"names", "en", NULL);
if (MMDB_SUCCESS != status) { ... }
if (entry_data.has_data) { ... }
If we wanted to find the first city the lookup path would be
"cities", "0". If you don't provide a lookup path at all, you'll get
the entry which corresponds to the top level map. The lookup path must
always end with NULL, regardless of which function you call.
The MMDB_get_value function takes a variable number of arguments. All
of the arguments after the MMDB_entry_data_s * structure pointer are
the lookup path. The last argument must be NULL.
The MMDB_vget_value function accepts a va_list as the lookup path. The
last element retrieved by va_arg() must be NULL.
Finally, the MMDB_aget_value accepts an array of strings as the lookup
path. The last member of this array must be NULL.
If you want to get all of the entry data at once you can call
MMDB_get_entry_data_list() instead.
For each of the three functions, the return value is a status code as
defined above.
MMDB_get_entry_data_list()
int MMDB_get_entry_data_list(
MMDB_entry_s *start,
MMDB_entry_data_list_s **const entry_data_list);
This function allows you to get all of the data for a complex data
structure at once, rather than looking up each piece using repeated
calls to MMDB_get_value().
MMDB_lookup_result_s result =
MMDB_lookup_sockaddr(mmdb, address->ai_addr, &mmdb_error);
MMDB_entry_data_list_s *entry_data_list, *first;
int status =
MMDB_get_entry_data_list(&result.entry, &entry_data_list);
if (MMDB_SUCCESS != status) { ... }
// save this so we can free this data later
first = entry_data_list;
while (1) {
MMDB_entry_data_list_s *next = entry_data_list = entry_data_list->next;
if (NULL == next) {
break;
}
switch (next->entry_data.type) {
case MMDB_DATA_TYPE_MAP: { ... }
case MMDB_DATA_TYPE_UTF8_STRING: { ... }
...
}
}
MMDB_free_entry_data_list(first);
It's up to you to interpret the entry_data_list data structure. The
list is linked in a depth-first traversal. Let's use this structure as
an example:
{
"names": {
"en": "Germany",
"de": "Deutschland"
},
"cities": [ "Berlin", "Frankfurt" ]
}
The list will consist of the following items:
1. MAP - top level map
2. UTF8_STRING - "names" key
3. MAP - map for "names" key
4. UTF8_STRING - "en" key
5. UTF8_STRING - value for "en" key
6. UTF8_STRING - "de" key
7. UTF8_STRING - value for "de" key
8. UTF8_STRING - "cities" key
9. ARRAY - value for "cities" key
10. UTF8_STRING - array[0]
11. UTF8_STRING - array[1]
The return value of the function is a status code as defined above.
MMDB_free_entry_data_list()
void MMDB_free_entry_data_list(
MMDB_entry_data_list_s *const entry_data_list);
The MMDB_get_entry_data_list() and
MMDB_get_metadata_as_entry_data_list() functions will allocate the
linked list structure from the heap. Call this function to free the
MMDB_entry_data_list_s structure.
MMDB_get_metadata_as_entry_data_list()
int MMDB_get_metadata_as_entry_data_list(
MMDB_s *const mmdb,
MMDB_entry_data_list_s **const entry_data_list);
This function allows you to retrieve the database metadata as a linked
list of MMDB_entry_data_list_s structures. This can be a more
convenient way to deal with the metadata than using the metadata
structure directly.
MMDB_entry_data_list_s *entry_data_list, *first;
int status =
MMDB_get_metadata_as_entry_data_list(mmdb, &entry_data_list);
if (MMDB_SUCCESS != status) { ... }
first = entry_data_list;
... // do something with the data
MMDB_free_entry_data_list(first);
The return value of the function is a status code as defined above.
MMDB_dump_entry_data_list()
int MMDB_dump_entry_data_list(
FILE *const stream,
MMDB_entry_data_list_s *const entry_data_list,
int indent);
This function takes a linked list of MMDB_entry_data_list_s structures
and stringifies it to the given stream. The indent parameter is the
starting indent level for the generated output. It is incremented for
nested data structures (maps, array, etc.).
The stream must be a file handle (stdout, etc). If your platform
provides something like the GNU open_memstream() you can use that to
capture the output as a string.
The output is formatted in a JSON-ish fashion, but values are marked
with their data type (except for maps and arrays which are shown with
"{}" and "[]" respectively).
The specific output format may change in future releases, so you should
not rely on the specific formatting produced by this function. It is
intended to be used to show data to users in a readable way and for
debugging purposes.
The return value of the function is a status code as defined above.
MMDB_read_node()
int MMDB_read_node(
MMDB_s *const mmdb,
uint32_t node_number,
MMDB_search_node_s *const node);
This reads a specific node in the search tree. The third argument is a
reference to an MMDB_search_node_s structure that will be populated by
this function.
The return value is a status code. If you pass a node_number that is
greater than the number of nodes in the database, this function will
return MMDB_INVALID_NODE_NUMBER_ERROR, otherwise it will return
MMDB_SUCCESS.
MMDB_lib_version()
const char *MMDB_lib_version(void)
This function returns the library version as a string, something like
"2.0.0".
EXAMPLE
#include <maxminddb.h>
int main(int argc, char **argv)
{
MMDB_s mmdb;
int status = MMDB_open(fname, MMDB_MODE_MMAP, &mmdb);
if (MMDB_SUCCESS != status) {
fprintf(stderr, "\n Can't open %s - %s\n",
fname, MMDB_strerror(status));
if (MMDB_IO_ERROR == status) {
fprintf(stderr, " IO error: %s\n", strerror(errno));
}
exit(1);
}
int gai_error, mmdb_error;
MMDB_lookup_result_s result =
MMDB_lookup_string(mmdb, ipstr, &gai_error, &mmdb_error);
if (0 != gai_error) {
fprintf(stderr,
"\n Error from getaddrinfo for %s - %s\n\n",
ipstr, gai_strerror(gai_error));
exit(2);
}
if (MMDB_SUCCESS != mmdb_error) {
fprintf(stderr,
"\n Got an error from libmaxminddb: %s\n\n",
MMDB_strerror(mmdb_error));
exit(3);
}
MMDB_entry_data_list_s *entry_data_list = NULL;
int exit_code = 0;
if (result.found_entry) {
int status = MMDB_get_entry_data_list(&result.entry,
&entry_data_list);
if (MMDB_SUCCESS != status) {
fprintf(
stderr,
"Got an error looking up the entry data - %s\n",
MMDB_strerror(status));
exit_code = 4;
goto end;
}
if (NULL != entry_data_list) {
MMDB_dump_entry_data_list(stdout, entry_data_list, 2);
}
} else {
fprintf(
stderr,
"\n No entry for this IP address (%s) was found\n\n",
ip_address);
exit_code = 5;
}
end:
MMDB_free_entry_data_list(entry_data_list);
MMDB_close(&mmdb);
exit(exit_code);
}
THREAD SAFETY
This library is thread safe when compiled and linked with a thread-safe
malloc and free implementation.
INSTALLATION AND SOURCE
You can download the latest release of libmaxminddb from GitHub
(https://github.com/maxmind/libmaxminddb/releases).
Our GitHub repo (https://github.com/maxmind/libmaxminddb) is publicly
available. Please fork it!
BUG REPORTS AND PULL REQUESTS
Please report all issues to our GitHub issue tracker
(https://github.com/maxmind/libmaxminddb/issues). We welcome bug
reports and pull requests. Please note that pull requests are greatly
preferred over patches.
AUTHORS
This library was written by Boris Zentner (bzentner@maxmind.com) and
Dave Rolsky (drolsky@maxmind.com).
COPYRIGHT AND LICENSE
Copyright 2013-2014 MaxMind, Inc.
Licensed under the Apache License, Version 2.0 (the "License"); you may
not use this file except in compliance with the License. You may
obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied. See the License for the specific language governing
permissions and limitations under the License.
SEE ALSO
mmdblookup(1)
libmaxminddb(3)