[Codel] [PATCH net-next] fq_codel: report congestion notification at enqueue time

[David Miller]

From: Eric Dumazet <eric.dumazet at gmail.com>
Date: Fri, 29 Jun 2012 07:50:08 +0200

> Hmm, problem is the sender thinks the packet was queued for
> transmission.
> 
>         ret = macvlan_queue_xmit(skb, dev);
>         if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN)) {
>                 struct macvlan_pcpu_stats *pcpu_stats;
> 
>                 pcpu_stats = this_cpu_ptr(vlan->pcpu_stats);
>                 u64_stats_update_begin(&pcpu_stats->syncp);
>                 pcpu_stats->tx_packets++;
>                 pcpu_stats->tx_bytes += len;
>                 u64_stats_update_end(&pcpu_stats->syncp);
>         } else {
>                 this_cpu_inc(vlan->pcpu_stats->tx_dropped);
>         }

Ok, that is the meaning this has taken on.  Same test exists in
vlan_dev.c and this test used to be present also in the ipip.h macros
some time ago.

Nobody really does anything special with this value, except to
translate it to a zero 0 when propagating back to sockets.

The only thing it guards is the selection of which statistic to
increment.

For all practical purposes it is treated as NET_XMIT_SUCCESS except in
one location, pktgen, where it causes the errors counter to increment.

Looking this over, I'd say we should just get rid of it.