eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
1–10 of 35 posts
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#2I think of that as the opposite - an IPv6 socket pretending to be IPv4 in order to route to an IPv4 endpoint.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#3In a similar fashion, I once saw a python script that called out to a one-page C program that read a .csv dump (probably from SQLServer) and blew away the upper byte of each character, demoting it to ASCII.
Once I understood what was afoot, I was sad that someone had worked so hard when python's open() call supports an 'encoding' argument for just these occasions.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#4In a similar fashion, I once saw a python script that called out to a one-page C program that read a .csv dump (probably from SQLServer) and blew away the upper byte of each character, demoting it to ASCII. Once I understood what was afoot, I was sad that someone had worked so hard when python's open() call supports an 'encoding' argument for just these occasions.
Reminds me of a time where someone stored the md5 hash of a password as a string by throwing away all non-ascii bytes; so roughly half the bytes.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#5In a similar fashion, I once saw a python script that called out to a one-page C program that read a .csv dump (probably from SQLServer) and blew away the upper byte of each character, demoting it to ASCII. Once I understood what was afoot, I was sad that someone had worked so hard when python's open() call supports an 'encoding' argument for just these occasions.
Reminds me of a time where someone stored the md5 hash of a password as a string by throwing away all non-ascii bytes; so roughly half the bytes.
I've seen something similar, but it depended on whether plain `char` is signed or unsigned, which is highly platform-dependent.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#6In a similar fashion, I once saw a python script that called out to a one-page C program that read a .csv dump (probably from SQLServer) and blew away the upper byte of each character, demoting it to ASCII. Once I understood what was afoot, I was sad that someone had worked so hard when python's open() call supports an 'encoding' argument for just these occasions.
that's the first thing i ever uploaded anywhere! fixtxt.exe on simtel.net
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#7If you think that's wild, just wait until you learn about 6to4 [1] (not to be confused with 6over4 [2] ...)
TL;DR: Given a globally unique IPv4 address, you can create automatic tunneling IPv6 networks with the IPv4 address embedded into the IPv6 address space.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#8pretty cool seeing all the stuff people do to make networks talk, honestly makes me wonder - you think stuff like this sticks around because of habit or just taking shortcuts sometimes
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#9I learnt this when using net.ListenTCP in Go, if you use lsof to show the network type, it would be IPv6. But it could also handle IPv4 requests.
Re: eBPF Mystery: When is IPv4 not IPv4? When it's pretending to be IPv6
#10If you think that's wild, just wait until you learn about 6to4 [1] (not to be confused with 6over4 [2] ...) TL;DR: Given a globally unique IPv4 address, you can create automatic tunneling IPv6 networks with the IPv4 address embedded into the IPv6 address space. [1] https://en.wikipedia.org/wiki/6to4 [2] https://en.wikipedia.org/wiki/6over4
And for a short while, it was the most common use of IPv6 on the public Internet! Now largely dead and gone.