Re: want opinions on possible glitch in 2.4 network error reporti ng

[Chris Friesen <cfriesen@nortelnetworks.com>]

"Richard B. Johnson" wrote:
> 
> On Thu, 7 Feb 2002, Perches, Joe wrote:
> [SNIPPED..]
> > > That is correct UDP behaviour
> >
> > Do you think this is the correct PacketSocket/RAW behaviour?
> 
> Yes.
> 
> > How does one guarantee a send/sendto/write?
> > -
> 
> Easy, you use send() or write(). These work on stream protocol TCP/IP
> where there is a "connection". Connectionless protocols, i.e., UDP are
> not guaranteed to do anything useful -- but, because of their speed,
> they can be useful with some help from user-mode code.

Is there any syscall that can guarantee that a single packet has been sent out
over the wire?  Suppose I want to broadcast an ARP packet.  If I make a packet
socket and call sendto() on it, I want a guarantee that the packet will make it
out onto the wire, or the sendto() should fail.

UDP failing I can understand (kind of, anyway) but for raw sockets, packet
sockets, etc. I think there should be at least some kind of mechanism to bypass
all the congestion controls and either shove the packet onto the device's tx
buffer or return a failure code.

The possibility of random dropping of packets in the kernel means that an
infinite loop on sendto() will chew up the entire machine even if you've only
got a 10Mbit/s link.  This seems just wrong.

Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10  
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com