Re: [Netconsole-devel] Protocol notes

[<li...@ho...>]

> I was considering it, but it adds a lot of complexity for what seems to
> be very little gain.  In the end I think the solution I came up with is
> cleaner.  Having a header end pointer so we can add new header fields in
> the future might be a good idea, though.

How about IP-style options?

> I was thinking about having a flags field in the header to denote that
> sequence numbers are lost -- one bit to indicate "my own sequence numbers
> have been reset" (START OF STREAM - typically issued when starting a new
> boot loader level) and one bit to indicate "I don't know where you are in
> your stream."

Okay, so we have a SYN bit and (the inverse of) an ACK bit.
Oh, above you've suggested a data pointer.

The UDP header gives us two port numbers and a checksum.

We already have two 32-bit byte checksums.

Remind me again why we don't just use TCP?

    0                   1                   2                   3   
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Source Port          |       Destination Port        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence Number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Acknowledgment Number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Data |           |U|A|P|R|S|F|                               |
   | Offset| Reserved  |R|C|S|S|Y|I|            Window             |
   |       |           |G|K|H|T|N|N|                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Checksum            |         Urgent Pointer        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

> I don't know if this is a feasible option, mostly because I worry about
> it requiring too much state at the server (which could cause restart
> problems.)

It does require that the server ping on startup.  It can back off dead
clients pretty severely after a while.  They're supposed to send packets
themselves on startup.