Get the ipv6 address from a interface

Hello,
i need a function that returns the ipv6 address from a given interface
name. For ipv4 i use this one:
def get_ip_address(ifname):
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
return socket.inet_ntoa(fcntl.ioctl(
s.fileno(),
0x8915, # SIOCGIFADDR
struct.pack('256s', ifname[:15])
)[20:24])

which works great. But i am not enough into python to port that to
ipv6. It has to work under linux only. Any help is appreciated.

Greets,
Kai

In article
<86176ef7-c2e0-4c5d-b883-d91672e3eb0b@w40g2000yqd.googlegroups.com>,
Kai Timmer <email@kait.de> wrote:

> Hello,
> i need a function that returns the ipv6 address from a given interface
> name. For ipv4 i use this one:
> def get_ip_address(ifname):
> s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
> return socket.inet_ntoa(fcntl.ioctl(
> s.fileno(),
> 0x8915, # SIOCGIFADDR
> struct.pack('256s', ifname[:15])
> )[20:24])
>
> which works great. But i am not enough into python to port that to
> ipv6. It has to work under linux only. Any help is appreciated.

I'm not 100% sure what you're trying to do, but the above is horribly
non-portable. You probably want to be looking at socket.getpeername() and
socket.getsockname().

In general, concepts like "the address of an interface" are difficult. In
many OS's, a given interface may have multiple addresses. This is
especially true in IPv6 where you've have both link local and global
unicast addresses on the same interface.

Can you back up a few steps and describe what it is that you're trying to
do, i.e. the use case?

> I'm not 100% sure what you're trying to do, but the above is horribly
> non-portable. You probably want to be looking at socket.getpeername() and
> socket.getsockname().

This only works if you are actually connected. I think he wants to find
out the local address without actually connecting.

> In general, concepts like "the address of an interface" are difficult. In
> many OS's, a given interface may have multiple addresses. This is
> especially true in IPv6 where you've have both link local and global
> unicast addresses on the same interface.

In Linux, you can only have one IPv4 address per interface (and you have
to use alias interfaces, such as eth0:0, to assign multiple addresses
to a physical link).

For IPv6 and Linux, you are right.

>
> Can you back up a few steps and describe what it is that you're trying to
> do, i.e. the use case?

I guess he wants to do the equivalent of ifconfig.

Regards,
Martin

> which works great. But i am not enough into python to port that to
> ipv6. It has to work under linux only. Any help is appreciated.

Not sure how universal this is, but I would read /proc/net/if_inet6.
At least, that's what ifconfig does, and it seems to work fine.

martin@mira:~$ cat /proc/net/if_inet6
fe80000000000000000000004d804137 1c 40 20 80 sixxs
fe80000000000000020d61fffe543e15 02 40 20 80 sis
00000000000000000000000000000001 01 80 10 80 lo
200106f809000a850000000000000002 1c 40 00 80 sixxs

Regards,
Martin

> In Linux, you can only have one IPv4 address per interface (and you
> have to use alias interfaces, such as eth0:0, to assign multiple
> addresses to a physical link).

that's actually not correct, use the "ip" tool (iproute2 package) to see
how easily you can have several addresses to a single interface.
ip addr add 1.1.1.1/24 dev eth0
ip addr add 2.2.2.1/24 dev eth0

the need for alias interfaces has been removed, a long time ago (AFAIK
even before the 2.4 kernel).

--
дамјан ( http://softver.org.mk/damjan/ )

In theory, there is no difference between theory and practice.
But, in practice, there is.