Net::Interface::Developer api, notes, hints
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.
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.
getifaddrs
ioctl's
ifreq, in6_ifreq, lifreq
ifreq
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.
ioctl
Net::Interface is built in 5 layers, listed below from the base up.
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.
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
struct sockaddr
in6_ifreq ni_in6_ifreq.c
in6_ifreq
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
struct sockaddr_storage
lifreq ni_lifreq.c
lifreq
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
linuxproc
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.
struct ifaddrs
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).
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.
Interface.xs
close
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) * *************************
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 developement 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
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.
ni_func.h
ni_util.c
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:
nifp
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; };
printf statement for terminal output of the form XX:XX:XX:XX:XX:XX:XX:XX
if( NI_MAC_NOT_ZERO(macp)) do something
Takes an agrument of the form sockaddr_in6.sin6_addr and prints XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX
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)
Use the appropriate free memory function call depending on the flavor of the getifaddrs function that returned the ifaddrs structure list.
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...
Extracts information about the type of ipV6 address. The returned value may be passed to the NEXT function call to print.
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
Print information about an ipV6 address for each bit present in type.
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" } };
Returns the size of the above table.
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
Allocate memory of for size and copy contents from memp. Returns NULL on error and sets errno to ENOMEM.
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));
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));
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 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.
1 POD Error
The following errors were encountered while parsing the POD:
You forgot a '=back' before '=head1'
To install Net::Interface, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Net::Interface
CPAN shell
perl -MCPAN -e shell install Net::Interface
For more information on module installation, please visit the detailed CPAN module installation guide.