Preventing ng_callout() timeouts to trigger packet queuing

[Karim Fodil-Lemelin]

Hi,

Below is a revised patch for this issue. It accounts for nodes or hooks 
that explicitly need to be queuing:

@@ -3632,7 +3632,12 @@ ng_callout(struct callout *c, node_p node, hook_p 
hook, int ticks,
         if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
                 return (ENOMEM);

-       item->el_flags |= NGQF_WRITER;
+       if ((node->nd_flags & NGF_FORCE_WRITER) ||
+           (hook && (hook->hk_flags & HK_FORCE_WRITER)))
+         item->el_flags |= NGQF_WRITER;
+       else
+         item->el_flags |= NGQF_READER;
+
         NG_NODE_REF(node);              /* and one for the item */
         NGI_SET_NODE(item, node);
         if (hook) {

Regards,

Karim.

On 09/04/2014 3:16 PM, Karim Fodil-Lemelin wrote:
> Hi List,
>
> I'm calling out to the general wisdom ... I have seen an issue in 
> netgraph where, if called, a callout routine registered by 
> ng_callout() will trigger packet queuing inside the worklist of 
> netgraph since ng_callout() makes my node suddenly a WRITER node 
> (therefore non reentrant) for the duration of the call.
>
> So as soon as the callout function returns, all following packets will 
> get directly passed to the node again and when the ngintr thread gets 
> executed then only then will I get the queued packets. This introduces 
> out of order packets in the flow. I am using the current patch below 
> to solve the issue and I am wondering if there is anything wrong with 
> it (and maybe contribute back :):
>
>
> @@ -3632,7 +3632,7 @@ ng_callout(struct callout *c, node_p node, 
> hook_p hook, int ticks,
>         if ((item = ng_alloc_item(NGQF_FN, NG_NOFLAGS)) == NULL)
>                 return (ENOMEM);
>
> -       item->el_flags |= NGQF_WRITER;
> +       item->el_flags = NGQF_READER;
>         NG_NODE_REF(node);              /* and one for the item */
>         NGI_SET_NODE(item, node);
>         if (hook) {
>
>
> Best regards,
>
> Karim.
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