[OpenAFS-devel] rx -nojumbo bug issue

[Jeffrey Altman]

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Avinesh Kumar wrote:
> Hi,
> 
> I was looking at the delta rx-allow-jumbogram-disabling-really-20080822.
> The code changes as suggested in rx_user.c, I don't believe that it
> would help.
> 
>      pp->maxDgramPackets =
>      MIN(rxi_nDgramPackets,
> -        rxi_AdjustDgramPackets(RX_MAX_FRAGS, pp->ifMTU));
> +        rxi_AdjustDgramPackets(rxi_nSendFrags, pp->ifMTU));
>      pp->ifDgramPackets =
>      MIN(rxi_nDgramPackets,
> -        rxi_AdjustDgramPackets(RX_MAX_FRAGS, pp->ifMTU));
> +        rxi_AdjustDgramPackets(rxi_nSendFrags, pp->ifMTU));
>      pp->maxDgramPackets = 1;
>      /* Initialize slow start parameters */
>      pp->MTU = MIN(pp->natMTU, pp->maxMTU);
> 
> First of all maxDgramPackets/ifDgramPackets would get minimum of 
> rxi_nDgramPackets
> and the return value of rxi_AdjustDgramPackets(). When -nojumbo is
> specified, rxi_nDgramPackets
> would be set to 1 and so will maxDgramPackets/ifDgramPackets; even if
> rxi_AdjustDgramPackets()
> suggests that it would fit more rx_packets.
> 
> I believe rxi_AdjustDgramPackets() just tells number of rx_packet that
> can be packed together (jumbogram)
> given the MTU and has no side-effects.
> 
> Also, just after these calculations, we are explicitly setting
>     pp->maxDgramPackets = 1;
> 
> Let me know if I am wrong. I am not sure of the significance of
> maxDgramPackets/ifDgramPackets,
> can anyone shed some light on this.
> 
> - Avinesh

Avinesh:

Without DELTA rx-allow-jumbogram-disabling-really-20080822 -nojumbo only
prevented the use of jumbograms in one direction.

I believe the portion that you are missing is that -nojumbo should not
only prevent me from sending jumbograms to you but that it should also
prevent you from sending jumbograms to me (even if you are not using
-nojumbo).   The number of datagrams you are permitted to send is
determined by the peer->ifDgramPackets value.

Jeffrey Altman

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