Provided by: libnet-interface-perl_1.012-3build1_amd64 
NAME
Net::Interface::Developer - api, notes, hints
DESCRIPTION
This contains development notes and API documentation for the Net::Interface module. It is
hoped that others will help fill in the missing pieces for OS's and address families that
are currently unsupported.
ARCHITECTURE
Net::Interface gathers information about the network interfaces in an OS independent
fashion by first attempting to use "getifaddrs" if "getifaddrs" is not supported on the OS
it falls back to using system "ioctl's" and the "ifreq, in6_ifreq, lifreq" structures
defined on the local host. Linux differs somewhat since ipV6 information is available only
directly from the kernel on older versions where "getifaddrs" is not available. The
"ifreq" and friends information is used to generate a "getifaddrs" response.
Herein lies the need for continued development by the opensource community. Many OS's
have peculiar "ioctl" variants and SIOC's variants that require unique code solutions. I'm
sure that all of them are not presently included.
Net::Interface is built in 5 layers, listed below from the base up.
description: files code
1) AF_xxx families: ni_af_inetcommon.c (C)
Code modules for AF families. Currently supported are AF_INET, AF_INET6. There is partial
support for AF_LINK and AF_PACKET for retrieval of MAC address from the interface where it
is needed. Where the code is reasonably universal for a particular address family and the
methods used to retrieve the information from the OS, it resides in an af_xxxx.c file.
2) IFREQ families: ni_xx_ifreq.c (C)
Code modules for IFREQ families. Currently supported are:
• "ifreq" ni_ifreq.c
Provides support for retrieval of ipV4 information. The structure "ifreq" does not
provide enough space to return data about socket address families larger than "struct
sockaddr". All known operating systems support this flavor of data retrieval. ni_ifreq.c
makes use of calls to ni_af_inet.c
• "in6_ifreq" ni_in6_ifreq.c
Provides support for retrieval of both ipV4 and ipV6 information. "in6_ifreq" uses
"struct sockaddr_storage" rather than the smaller "struct sockaddr" that is used in
"ifreq". This code modules support variants of the BSD operating system and a few
others. ni_in6_ifreq makes use of calls to ni_af_inetcommon.c
• "lifreq" ni_lifreq.c
Provides support for retrieval of both ipV4 and ipV6 information. "lifreq" has a custom
format unique to the SUN operating systems. Pretty much everything in it, while similar
to the two previous code modules, is custom.
• "linuxproc" ni_linuxproc.c
Provides support for retrieval of both ipV4 and ipV6 information. "linuxproc" uses
calls to ni_af_inet.c to get ipV4 information int "getifaddrs" format and custom code to
collect similarly formatted ipV6 information directly from the /proc file system. It
then performs a merge on these two data sets to put them into proper order and add fake
AF_LINK or AF_PACKET records to provide "getifaddrs" compatiable access to the MAC
address through the returned "struct ifaddrs" array.
3) "getifaddrs" ni_getifaddrs.c (C)
The "getifaddrs" code module contains the decision mechanism for how data is retrieved for
a particular build of Net::Interface. At build time, portions of the code are #ifdef'd
in/out depending on the availabiltiy of resource from the underlying OS. In addition, at
run time, if the system does not have native "getifaddrs" then a decision tree is used
depending on the response to calls for data to the various code modules described in
section 2).
4) Sub-system Interface.xs (PERLXS)
This file asks for the data about the interfaces with a generic call to "getifaddrs". The
data returned resides in memory allocated by the OS and must be freed or a memory leak
will result as it is not tracked by Perl's garbage collector. "Interface.xs" moves the
interface data from allocated memory to Perl managed memory where it can be reclaimed by
the garbage collection mechanism if/when the user space program turns it loose. This
eliminates the need for a "close" operation to free the OS's allocated memory.
5) User space Interface.pm (Perl)
DATA FLOW BLOCK DIAGRAM
The pure perl portion of this module performs most of the presentation operations for the
user that are published in the API for Net::Interface.
*\ \ \ | / / /*
* user space *
*************************
^ Net::Interface
| Architecture Block Diagram
v
*************************
* Interface.pm *
*************************
|
*************************
* Interface.xs *
*************************
|
************************* *************************
* system getifaddrs * * ni_getifreqs *
* via *<-if missing ->* via *
* (ni_getifaddrer.c) * * (ni_ifreq.c) *
************************* * (ni_lifreq.c) *
* (ni_in6_ifreq.c) *
* (ni_linuxproc.c) *
*************************
|
*************************
* (ni_af_inetcommon.c) *
*************************
DEVELOPER API
Access to the pieces of code in the block diagram above are available through a developer
API. These codes snippets from Interfaces.xs describe the access.
void
__developer(ref)
SV *ref
ALIAS:
d_ni_ifreq = NI_IFREQ
d_ni_lifreq = NI_LIFREQ
d_ni_in6_ifreq = NI_IN6_IFREQ
d_ni_linuxproc = NI_LINUXPROC
PREINIT:
char * process;
int er = ni_developer(ix);
and.....
void
gifaddrs_base(ref)
SV * ref
ALIAS:
# base = 0
gifa_ifreq = NI_IFREQ
gifa_lifreq = NI_LIFREQ
gifa_in6_ifreq = NI_IN6_IFREQ
gifa_linuxproc = NI_LINUXPROC
PREINIT:
struct ifaddrs * ifap;
int rv;
CODE:
if ((rv = ni_getifaddrs(&ifap,ix)) == -1) {
printf("failed PUNT!\n");
XSRETURN_EMPTY;
Both function sets result in a printed description to the terminal window to facilitate
code creation and debug. Currently the ref is unused. It is expected that future
development will modify or add to function access.
# test.pl for developer
#
use strict;
use Net::Interface;
# to call OS native getifaddrs if present
print "\nifreq\n"; gifaddrs_base Net::Interface();
# to call ni_linuxproc fallback getifaddrs
print "\nlxp\n"; gifa_linuxproc Net::Interface();
# to call ni_linuxproc ifreq emulation
print "\nglxp\n"; d_ni_linuxproc Net::Interface();
See: test.pl.developer
DEVELOPER API DESCRIPTION
If you have gotten this far, it is time to read some of the code. AF_familes and
IFREQ_families are accessed through constuctor structs found at the bottom of each of the
ni_af_xxx and ni_xx_ifreq source files. Their vectoring components are described in
"ni_func.h" near the bottom and in "ni_util.c" in the section labeled constructor
registration the essence of which is described here.
struct ni_ifconf_flavor * ni_ifcf_get(enum ni_FLAVOR type)
struct ni_ifconf_flavor * ni_safe_ifcf_get(enum ni_FLAVOR type);
nifp = ni_ifcf_get(NI_IFREQ);
Returns a pointer "nifp" to the structure for a particular flavor of ifreq. If a flavor is
unsupported on a particular architecture a NULL is returned by the first invocation and
NI_IFREQ by the second. Currently supported flavors are:
enum ni_FLAVOR {
NI_NULL, reserved for the getifaddrs base system call
NI_IFREQ,
NI_LIFREQ,
NI_IN6_IFREQ,
NI_LINUXPROC
};
struct ni_ifconf_flavor {
enum ni_FLAVOR ni_type;
int (*gifaddrs)
int siocgifindex;
int siocsifaddr;
int siocgifaddr;
int siocdifaddr;
int siocaifaddr;
int siocsifdstaddr;
int siocgifdstaddr;
int siocsifflags;
int siocgifflags;
int siocsifmtu;
int siocgifmtu;
int siocsifbrdaddr;
int siocgifbrdaddr;
int siocsifnetmask;
int siocgifnetmask;
int siocsifmetric;
int siocgifmetric;
int ifr_offset;
void (*fifaddrs) howto free ifaddrs
int (*refreshifr) howto refresh ifreq
void * (*getifreqs) howto get ifreq
int (*developer) developer access
struct ni_ifconf_flavor * ni_ifcf_next;
};
MACROS
NI_PRINT_MAC(u_char * hex_mac_string);
printf statement for terminal output of the form
XX:XX:XX:XX:XX:XX:XX:XX
NI_MAC_NOT_ZERO(u_char * hex_mac_string)
if( NI_MAC_NOT_ZERO(macp))
do something
NI_PRINT_IPV6(struct sin6_addr);
Takes an agrument of the form sockaddr_in6.sin6_addr and prints
XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX
FUNCTIONS
int ni_clos_reopn_dgrm(int fd, int af)
Closes and then opens an "ioctl" socket of type SOCK_DGRAM and returns the socket
value. If the socket value is NEGATIVE, no close is attempted an the call is
equivalent to:
socket(af,SOCK_DGRAM,0)
void ni_gifa_free(struct ifaddrs * ifap, int flavor)
Use the appropriate free memory function call depending on the flavor of the
getifaddrs function that returned the ifaddrs structure list.
int nifreq_gifaddrs(struct ifaddrs **ifap, struct ni_ifconf_flavor *nifp)
Our semi-standard version of "getifaddrs" used by OS's that provide "ifreq" and
"in6_ifreq".
NOTE: all calls to "getifaddrs" return -1 on failure and and the FLAVOR as enumerated
above on success.
i.e. NI_NULL for the native getifaddrs, NI_IFREQ, NI_LINUXPROC, etc...
uint32_t ni_ipv6addr_gettype(struct in6_addr * in6p)
Extracts information about the type of ipV6 address. The returned value may be passed
to the NEXT function call to print.
int ni_lx_map2scope(int lscope)
This function maps Linux style scope bits to their RFC-2373 equivalent.
scope flags rfc-2373
0 reserved
1 node-local (aka loopback, interface-local)
2 link-local
3 unassigned
4 unassigned
5 site-local
6 unassigned
7 unassigned
8 organization-local
9 unassigned
A unassigned
B unassigned
C unassigned
D unassigned
E global scope
F reserved
Linux rfc-2372
0x0000 0xe GLOBAL
0x0010u 0x1 NODELOCAL, LOOPBACK, INTERFACELOCAL
0x0020u 0x2 LINKLOCAL
0x0040u 0x5 SITELOCAL
void ni_linux_scope2txt(uint32_t type)
Print information about an ipV6 address for each bit present in "type".
const ni_iff_t ni_lx_type2txt[] = {
{ IPV6_ADDR_ANY, "unknown" },
{ IPV6_ADDR_UNICAST, "unicast" },
{ IPV6_ADDR_MULTICAST, "multicast" },
{ IPV6_ADDR_ANYCAST, "anycast" },
{ IPV6_ADDR_LOOPBACK, "loopback" },
{ IPV6_ADDR_LINKLOCAL, "link-local" },
{ IPV6_ADDR_SITELOCAL, "site-local" },
{ IPV6_ADDR_COMPATv4, "compat-v4" },
{ IPV6_ADDR_SCOPE_MASK, "scope-mask" },
{ IPV6_ADDR_MAPPED, "mapped" },
{ IPV6_ADDR_RESERVED, "reserved" },
{ IPV6_ADDR_ULUA, "uniq-lcl-unicast" },
{ IPV6_ADDR_6TO4, "6to4" },
{ IPV6_ADDR_6BONE, "6bone" },
{ IPV6_ADDR_AGU, "global-unicast" },
{ IPV6_ADDR_UNSPECIFIED, "unspecified" },
{ IPV6_ADDR_SOLICITED_NODE, "solicited-node" },
{ IPV6_ADDR_ISATAP, "ISATAP" },
{ IPV6_ADDR_PRODUCTIVE, "productive" },
{ IPV6_ADDR_6TO4_MICROSOFT, "6to4-ms" },
{ IPV6_ADDR_TEREDO, "teredo" },
{ IPV6_ADDR_ORCHID, "orchid" },
{ IPV6_ADDR_NON_ROUTE_DOC, "non-routeable-doc" }
};
int ni_sizeof_type2txt()
Returns the size of the above table.
u_int ni_get_scopeid(struct sockaddr_in6 * sin6)
On systems using KAME, this function extracts and returns the scope from field 2 of
the ipV6 address and sets fields 2,3 to zero. On all other systems it returns
sin6->sin6_scopeid
scope flags rfc-2373
0 reserved
1 node-local
2 link-local
3 unassigned
4 unassigned
5 site-local
6 unassigned
7 unassigned
8 organization-local
9 unassigned
A unassigned
B unassigned
C unassigned
D unassigned
E global scope
F reserved
void * ni_memdup(void *memp, int size)
Allocate memory of for size and copy contents from memp. Returns NULL on error and
sets errno to ENOMEM.
void ni_plen2mask(void * in_addr, int plen, int sizeofaddr)
Create a NETMASK string from a prefix length
For ipV4: ni_plen2mask(&in_addr, cidr, sizeof(struct in_addr));
For ipV6: ni_plen2mask(&in6_addr, cidr, sizeof(struct in6_addr));
int ni_prefix(void * ap, int len, int size)
Calculated the prefix length for a NETMASK where *ap points to the binary
representation of the NETMASK and size is the number of bytes in the mask.
For ipV4: ni_prefix(&in_addr,sizeof(struct in_addr));
For ipV6: ni_prefix(&in6_addr,sizeof(struct(in6_addr));
int ni_refresh_ifreq(int fd, struct ifconf *ifc, void **oifr, void **olifr, struct
ni_ifconf_flavor * nifp)
Some OS lose scope on the particular device/addr handle when certain ioctl's are
performed. This function refreshs the ifconf chain and positions the pointers in the
exact same spot with fresh scope.
See ni_in6_ifreq.c and ni_af_net6.c for usage. Search for the string refreshifr. Code
snippit looks like:
nifp->refreshir
COPYRIGHT
Copyright 2008-2009 - Michael Robinton
This program is free software; you can redistribute it and/or modify it under the terms of
the GNU General Public License as published by the Free Software Foundation; either
version 2, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License in the file named "Copying" for more details.
You should also have received a copy of the GNU General Public License along with this
program in the file named "Copying". If not, write to the
Free Software Foundation, Inc.
59 Temple Place, Suite 330
Boston, MA 02111-1307, USA
or visit their web page on the internet at:
http://www.gnu.org/copyleft/gpl.html.