What was the motivation for adding the IPV6_V6ONLY flag?

Posted by Jeremy Friesner on Stack Overflow See other posts from Stack Overflow or by Jeremy Friesner
Published on 2010-04-22T19:11:37Z Indexed on 2010/04/22 19:13 UTC
Read the original article Hit count: 196

Filed under:

IPv6

|

setsockopt

|

networking

In IPv6 networking, the IPV6_V6ONLY flag is used to ensure that a socket will only use IPv6, and in particular that IPv4-to-IPv6 mapping won't be used for that socket. On many OS's, the IPV6_V6ONLY is not set by default, but on some OS's (e.g. Windows 7), it is set by default.

My question is: What was the motivation for introducing this flag? Is there something about IPv4-to-IPv6 mapping that was causing problems, and thus people needed a way to disable it? It would seem to me that if someone didn't want to use IPv4-to-IPv6 mapping, they could simply not specify a IPv4-mapped IPv6 address. What am I missing here?

© Stack Overflow or respective owner

Related posts about IPv6

IPV6 auto configuration not working

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
In Windows 7, my computer can automatically get a IPV6 global address and use IPV6 network, but in Ubuntu Natty, I can't find out how to let stateless configuration work. My network is a university campus network,so I don't need tunnels. I think if one thing can silently and successfully be accomplished… >>> More
Fritz!Box IPv6-Address different than IPv6-Prefix

as seen on Server Fault - Search for 'Server Fault'
In my Fritzbox it states the following: IPv6-Adresse: 2a02:8070:600::14b6:c7******, Gültigkeit: 100465/86065s IPv6-Präfix: 2a02:8070:62c:3200::/56, Gültigkeit: 100464/86064s I am not able to connect to IPv6 Addresses from computers configured by the fritzbox, because they get an address with prefix… >>> More
Static IPv6 address advertising and IPv6 autoconfig in Debian/Ubuntu

as seen on Server Fault - Search for 'Server Fault'
I have a network that advertises IPv6 addresses through IPv6 autoconfig. To allow DNS lookups and to have fancy IP addresses, we setup "static" IPv6 addresses through /etc/network/interfaces: auto eth0 iface eth0 inet dhcp iface eth0 inet6 static address a:b:c:d:e::f netmask 64 Whenever… >>> More
HTG Explains: Are You Using IPv6 Yet? Should You Even Care?

as seen on How to geek - Search for 'How to geek'
IPv6 is extremely important for the long-term health of the Internet. But is your Internet service provider providing IPv6 connectivity yet? Does your home network support it? Should you even care if you’re using IPv6 yet? Switching from IPv4 to IPv6 will give the Internet a much larger pool… >>> More
Debian, 6rd tunnel, and connection troubles

as seen on Server Fault - Search for 'Server Fault'
Long story short I am having issues with IPv6 using a 6rd tunnel with my ISP, charter business. They offer a 6rd tunnel that I think I have properly set up, but the server doesn’t reply to every ipv6 request. When the server has the network interfaces idle with no traffic for about 10 minutes, then… >>> More

Related posts about setsockopt

setsockopt (sys/socket.h)

as seen on Stack Overflow - Search for 'Stack Overflow'
The prototype for setsockopt is: int setsockopt(int socket, int level, int option_name, const void *option_value, socklen_t option_len); Are the following all correct ? Which are not ? a.) int buffsize = 50000; setsockopt(s, SOL_SOCKET, SO_RCVBUF, (char *)&buffsize, sizeof(buffsize)); b.) int… >>> More
setsockopt EOPNOTSUPP (Operation not supported)

as seen on Server Fault - Search for 'Server Fault'
When I strace my MySQL process, I keep finding the same error over and over: setsockopt(240, SOL_IP, IP_TOS, [8], 4) = -1 EOPNOTSUPP (Operation not supported) futex(0x87ab944, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0x87ab940, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 1}) = 1 futex(0x87ab260, FUTEX_WAKE_PRIVATE… >>> More
FTP not listing files behind firewall (setsockopt (ignored): Permission denied)

as seen on Server Fault - Search for 'Server Fault'
We are developing a Magento application that has a module that works with FTP. Today we deployed this on the testing environment which is setup in the following way: Gateway server which has the following iptables rules: # iptables -L -n -v Chain INPUT (policy ACCEPT 2 packets, 130 bytes) pkts… >>> More
setsockopt TCP_NODELAY question on Windows Mobile

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all, I have a problem on Windows Mobile 6.0. I would like to create a TCP connection which does not use the Nagle algorithm, so it sends my data when I call "send" function, and does not buffer calls, having too small amount of data. I tried the following: BOOL b = TRUE; setsockopt(socketfd… >>> More
What was the motivation for adding the IPV6_V6ONLY flag?

as seen on Stack Overflow - Search for 'Stack Overflow'
In IPv6 networking, the IPV6_V6ONLY flag is used to ensure that a socket will only use IPv6, and in particular that IPv4-to-IPv6 mapping won't be used for that socket. On many OS's, the IPV6_V6ONLY is not set by default, but on some OS's (e.g. Windows 7), it is set by default. My question is: What… >>> More