(speaking in scope where IPv4 and IPv6 addresses are likely to appear
in the same position of the /proc 'file')
If you want to print addresses as the classical IPv4 presentation says,
and then use colon to separate port number from address, the IPv6 will
give you a "nasty" surprise:
eth0 Link encap:Ethernet HWaddr 00:00:F8:75:7B:3B
inet addr:194.252.70.2 Bcast:194.252.70.255 Mask:255.255.255.0
inet6 addr: 3ffe:2610:2:fe00:200:f8ff:fe75:7b3b/64 Scope:Global
inet6 addr: fe80::200:f8ff:fe75:7b3b/10 Scope:Link
So be damn carefull where you present them with 'standard' encodings.
$ cat /proc/net/tcp
sl local_address rem_address st tx_queue rx_queue tr tm->when
0: 0246FCC2:03FB 44FFFBC2:0016 01 00000000:00000000 00:00000000
1: 0246FCC2:0016 F347FCC2:03FE 01 00000000:00000000 00:00000000
...
$ cat /proc/net/tcp6
sl local_address remote_address ...
0: 0000000000000000FFFF00000246FCC2:0019 0000000000000000FFFF0000197B59C0:C799
...
$ netstat -n
Active Internet connections (including servers)
Proto Recv-Q Send-Q Local Address Foreign Address
tcp 0 0 194.252.70.2:1019 194.251.255.68:22
tcp 0 0 194.252.70.2:22 194.252.71.243:1022
tcp 0 0 ::ffff:194.252.70.2:25 ::ffff:128.214.248:1325
> There is no question in my mind - printing out IPv4 addresses as hex
> "integers" is wrong. It has always been wrong, and it's wrong now. It
> happens to be very simple, which is the excuse for doing it, but it's
> still wrong.
Standard (although deprecated) mode to present IPv4 addresses
in email is also: (unsigned 32-bit integer)
[#3271312898]
I still hold an opinion that cleanest form is to present them
as arrays of hex-encoded bytes. They may look like hex-encoded
integers to the uninformed, but that is not the intention.
I don't mind the different encodings when there is no change
of mistakes, but with NFS running over IPv6 we will definitely
get into these issues sooner or latter. There I want it to
be as unambiguous as possible!
> Linus
/Matti Aarnio <matti.aarnio@sonera.fi>
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