>>>>> On Mon, 10 Apr 2006 11:29:34 -0600,
>>>>> Kristine Adamson <[EMAIL PROTECTED]> said:
> I have a question about a stack's behavior when the IPV6_DONTFRAG socket
> option has been set for a UDP or RAW socket, and a packet is too large to
> be sent out from the stack. RFC 3542 (Advanced Sockets Application
> Program Interface (API) for IPv6) seems to state the following about what
> the stack should do in this case:
> "When the data size is larger than the MTU of the outgoing interface,
> the packet will be discarded. Applications can know the result by
> enabling the IPV6_RECVPATHMTU option described below and receiving
> the corresponding ancillary data items. An additional error EMSGSIZE
> may also be returned in some implementations. Note, however, that
> some other implementations might not be able to return this
> additional error when sending a message."
> Is the stack also supposed to create an ICMPv6 Packet Too Big message to
> send up to the application?
Not at least when I wrote the above text. Our (BSD's) implementation
does not send the local ICMPv6 error message up to the application,
for that matter.
> In a multiprocessing environment, don't
> applications like Ping and Traceroute need more information that what is
> in the ip6_mtuinfo structure in order to determine if the IPV6_PATHMTU
> information was sent as a response to one of their outbound packets or
> not?
That might be a useful feature, but I personally suspect how effective
it is in practice. First, I think the use of IPV6_DONTFRAG (+
IPV6_PATHMTU) is very rare, especially the case where multiple
processes enable this option and send large packets to the same
destination. Secondly, since the application enabling this option is
generally expected to keep track of the transmission history in some
way, the application would be able to use the information returned via
IPV6_PATHMTU appropriately, whether or not it was caused by itself.
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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