4 ms·

>how can you fit >32 bits of data (IPv6) into 32 bit data structures (IPv4: struct s_addr)? By using nat46 on ISP's routers.

throw0101c 2y ago
>> how can you fit >32 bits of data (IPv6) into 32 bit data structures (IPv4: struct s_addr)? > By using nat46 on ISP's routers. I do not understand. In Ye Olde Times a system would call gethostbyname() and this send out a DNS packet asking for the IP address. Of course DNS record returned would be an A record, which is where your first problem is: A records are fixed at 32-bits (RFC 1035 § 3.4.1). So your first task is to create a new record type and update every DNS server and client to support the longer addresses. Of course the longer address has to fit into the data structures of the OS you called gethostbyname() from, but gethostbyname() is set to use particular data structures. So now you have to update all the client DNS code to support the new, longer addresses. Further, gethostbyname() had no way to specify an address type (like if you wanted the IPv4 address(es) or the IPng one(s)): * https://man.freebsd.org/cgi/man.cgi?query=gethostbyname&manpath=FreeBSD+1.0-RELEASE https://man.freebsd.org/cgi/man.cgi?query=gethostbyname&manp... The the returned data structures only allowed for one type of address type, so you either got IPv4 or IPng. So if you wanted to be able to specify the record/address type to query, a new API had to be created. Luckily the next step, setting up a socket() and connect()ing is less of a burden, because that API already supported different protocols: * https://man.freebsd.org/cgi/man.cgi?query=socket&manpath=FreeBSD+1.0-RELEASE https://man.freebsd.org/cgi/man.cgi?query=socket&manpath=Fre... But if you have a host that support IPng, but its upstream router does not, how does it support a packet with a longer source address a shorter destination address get through? Do you send IPv4 packets with embedded IPng packets with-in them to translation relays perhaps? How is this any different IPv6 transition mechanisms like Teredo?
- aboardRat4 2y ago
  Your isp dns converts the AAAA record to AA record with the ipv4 of it's own (only router) configured dualstack machine, that machine does cgnat46 and visits the ipv6 only server. If software has hardcoded ipv6 addresses, this is much harder to solve, but I don't think this is really an issue, because hardcoded ipv6 addresses appear very seldom.
  - Dylan16807 2y ago
    Assuming you mean nat46, your description is a bit off. The NAT box doesn't have a single ipv4, it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. But that means it has to intercept all DNS requests and doesn't work with anything it didn't intercept, which seems far from ideal.
    - aboardRat4 2y ago
      >it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. But those don't have to be globally routable. >it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. This wasn't really a problem until doh/dot became a thing. But even nowadays doh and dot are provided by whom? By google and cloudflare who are tls-mitm'ing half of the internet anyway. Moreover most ISPs intercept dns to display those "please enter your phone number to verify your identity" screens anyway. >far from ideal. No more imperfect than NAT. Idealism is what is killing ipv6.
      - Dylan16807 2y ago
        If I'm going to run single stack locally I'm going to use IPv6 and a stateless converter for IPv4.
        aboardRat4 2y ago
        Which means that servers have zero incentive to convert to ipv6. All this cgnat46 setup is not in the name of end users, because they will always adapt somehow, as reels have a huge force of attraction. It is to make sure that service providers can deploy ipv6-only _servers_ and not bother that 60 percent of their target audience will be unavailable. The issue with the ipv6 internet is not the end users, they are paying, so the ISPs will always adapt to their needs, or the users themselves will buy new equipment in the worst case, it's the service providers who stop being profitable by going ipv6-only.

throw0101c 2y ago

>> how can you fit >32 bits of data (IPv6) into 32 bit data structures (IPv4: struct s_addr)? > By using nat46 on ISP's routers. I do not understand. In Ye Olde Times a system would call gethostbyname() and this send out a DNS packet asking for the IP address. Of course DNS record returned would be an A record, which is where your first problem is: A records are fixed at 32-bits (RFC 1035 § 3.4.1). So your first task is to create a new record type and update every DNS server and client to support the longer addresses. Of course the longer address has to fit into the data structures of the OS you called gethostbyname() from, but gethostbyname() is set to use particular data structures. So now you have to update all the client DNS code to support the new, longer addresses. Further, gethostbyname() had no way to specify an address type (like if you wanted the IPv4 address(es) or the IPng one(s)): * https://man.freebsd.org/cgi/man.cgi?query=gethostbyname&manpath=FreeBSD+1.0-RELEASE https://man.freebsd.org/cgi/man.cgi?query=gethostbyname&manp... The the returned data structures only allowed for one type of address type, so you either got IPv4 or IPng. So if you wanted to be able to specify the record/address type to query, a new API had to be created. Luckily the next step, setting up a socket() and connect()ing is less of a burden, because that API already supported different protocols: * https://man.freebsd.org/cgi/man.cgi?query=socket&manpath=FreeBSD+1.0-RELEASE https://man.freebsd.org/cgi/man.cgi?query=socket&manpath=Fre... But if you have a host that support IPng, but its upstream router does not, how does it support a packet with a longer source address a shorter destination address get through? Do you send IPv4 packets with embedded IPng packets with-in them to translation relays perhaps? How is this any different IPv6 transition mechanisms like Teredo?

aboardRat4 2y ago
Your isp dns converts the AAAA record to AA record with the ipv4 of it's own (only router) configured dualstack machine, that machine does cgnat46 and visits the ipv6 only server. If software has hardcoded ipv6 addresses, this is much harder to solve, but I don't think this is really an issue, because hardcoded ipv6 addresses appear very seldom.
- Dylan16807 2y ago
  Assuming you mean nat46, your description is a bit off. The NAT box doesn't have a single ipv4, it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. But that means it has to intercept all DNS requests and doesn't work with anything it didn't intercept, which seems far from ideal.
  - aboardRat4 2y ago
    >it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. But those don't have to be globally routable. >it needs a big pile of ipv4 addresses to dynamically allocate whenever a new AAAA record comes through. This wasn't really a problem until doh/dot became a thing. But even nowadays doh and dot are provided by whom? By google and cloudflare who are tls-mitm'ing half of the internet anyway. Moreover most ISPs intercept dns to display those "please enter your phone number to verify your identity" screens anyway. >far from ideal. No more imperfect than NAT. Idealism is what is killing ipv6.
    - Dylan16807 2y ago
      If I'm going to run single stack locally I'm going to use IPv6 and a stateless converter for IPv4.
      - aboardRat4 2y ago
        Which means that servers have zero incentive to convert to ipv6. All this cgnat46 setup is not in the name of end users, because they will always adapt somehow, as reels have a huge force of attraction. It is to make sure that service providers can deploy ipv6-only _servers_ and not bother that 60 percent of their target audience will be unavailable. The issue with the ipv6 internet is not the end users, they are paying, so the ISPs will always adapt to their needs, or the users themselves will buy new equipment in the worst case, it's the service providers who stop being profitable by going ipv6-only.