* ropers wrote: > Hiya, > > I only recently learned that when addressing an Internet server/host > by IPv4 address, it is possible to not use the standard dotted decimal > notation (abc.def.uvw.xyz) but instead use any of a number of > alternative formats; for example it is possible to specify the IP > address in all-decimal dword format, or as an octal or hexadecimal > number, etc.
it actually took me by surprise. I named my package build machines 4.2, 4.3, etc., for obvious reasons, but when I tried to ping them '$ ping 4.2' I was really surprised about the smart-ass stupidity someone fiddled into ping... > > If this is news to you, and if you have a bit of time to waste, you > could read a bit more here: > http://www.reddit.com/comments/6usfd/case_study_is_php_embarrasingly_slower_than_java/c04xgjf > http://www.pc-help.org/obscure.htm > > Now, I was really surprised to learn of all of this, as this info is > hardly ever mentioned everywhere, and it seems to me that even many > fairly seasoned IT people aren't aware of these possibilities. E.g. > the http://www.3com.com/other/pdfs/infra/corpinfo/en_US/501302.pdf > that's linked from the OpenBSD FAQ also doesn't mention these > alternative notations at all. > > So I wonder: > > Does anyone know whether these alternative notations > (dword/octal/hexadecimal...) are officially *supposed* to work? Or is > it more of an accident that they do? Are there any RFCs on this? (A > cursory search didn't turn up anything that seemed appropriate.) > Presumably it's a matter of the TCP/IP stack that they do work? But it > seems not all tools appear to do support this; e.g. I couldn't find a > way to look up 2172650943 with whois or host, but ping and ftp work > fine, as does the traditional notation 129.128.5.191. Firefox however > appears to work fine with dword/all-decimal IPv4 addresses, as does > lynx. So I wonder what's expected behaviour here, and whether the > tools that don't work with alternate notations should work? Also, does > all of this have implications for pf.conf? A bit of googling told me > that black hats sometimes try to use these alternate notations to get > around restrictions. > > Thanks and regards, > --ropers
