"Brian Utterback" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> David Schwartz wrote: >> "Brian Utterback" <[EMAIL PROTECTED]> wrote in message >> news:[EMAIL PROTECTED] >> >>> David Schwartz wrote: >> I am saying the default presumption is that it must be that way but >> that particular protocols can override it. That's effectively what SHOULD >> means in a general description -- done that way unless the specifics of >> some particular case justify doing otherwise. > Oh? Do you know of any OS that does this? Sure, I do. All of Linux's kernel request/response UDP protocols work this way, including NFS-over-UDP. > Given a multi-homed system, the OS will respond with the same IP address > in the source address that > was used as the destination address in the request, without application > support when using UDP, no matter which of the possibly many destination > addresses were used? I know Solaris doesn't, and truthfully, I don't > see how it could possibly be done. If the OS implements a UDP request/response protocol, it should ensure the source address of the reply is the destination address of the request unless the protocol specifies otherwise. Most OS implementations of UDP request/reply protocols *DO* do this. You are asking about both OSes and applications in a confusing way that seems to be based on the misunderstanding that I'm saying the kernel should somehow make an application do the right thing. I'm saying whatever implements the request/response protocol over UDP should do the right thing, which in most cases is the application, not the kernel. > The application can do it, if it can determine the destination address. Which it can, unless the OS is broken. Do we agree that an OS that makes it difficult or impossible for an application to determine the destination address of a received UDP datagram is broken? > As I pointed out, only Bootps, SNMP and NTP are doing this, at least on > Solaris. What do you think the OS has to do with what the applications that provide these services do? > Linux, Solaris and other OS's now have a way to get the > destination address via the socket, but that is a very new feature, and > not generally used. Of course, now that it is available, more might use > it, and it would have been unreasonable had the UDP standard demanded it, > but it did not, and as such UDP protocols have traditionally included > methods to work around it. I'm not sure I understand what you think the point of this is. Is it that bad design in the past somehow justifies bad design now? The source and destination IP addresses are not internal protocol details -- they're always already visible at the application level. DS _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
