Get the ipv6 address from a interface

[Kai Timmer]

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

 

[Roy Smith]

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?

 

[Martin v. Löwis]

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

 

[Martin v. Löwis]

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

 

[Дамјан ГеоргиевÑки]

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).