On Tue, 2022-03-15 at 20:48 +0800, Tonghao Zhang wrote:
> On Tue, Mar 15, 2022 at 5:59 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> >
> > On 3/14/22 3:15 PM, xiangxia.m.yue@xxxxxxxxx wrote:
> > [...]
> > > include/linux/netdevice.h | 3 +++
> > > include/linux/rtnetlink.h | 1 +
> > > net/core/dev.c | 31 +++++++++++++++++++++++++++++--
> > > net/sched/act_skbedit.c | 6 +++++-
> > > 4 files changed, 38 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > > index 0d994710b335..f33fb2d6712a 100644
> > > --- a/include/linux/netdevice.h
> > > +++ b/include/linux/netdevice.h
> > > @@ -3065,6 +3065,9 @@ struct softnet_data {
> > > struct {
> > > u16 recursion;
> > > u8 more;
> > > +#ifdef CONFIG_NET_EGRESS
> > > + u8 skip_txqueue;
> > > +#endif
> > > } xmit;
> > > #ifdef CONFIG_RPS
> > > /* input_queue_head should be written by cpu owning this struct,
> > > diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
> > > index 7f970b16da3a..ae2c6a3cec5d 100644
> > > --- a/include/linux/rtnetlink.h
> > > +++ b/include/linux/rtnetlink.h
> > > @@ -100,6 +100,7 @@ void net_dec_ingress_queue(void);
> > > #ifdef CONFIG_NET_EGRESS
> > > void net_inc_egress_queue(void);
> > > void net_dec_egress_queue(void);
> > > +void netdev_xmit_skip_txqueue(bool skip);
> > > #endif
> > >
> > > void rtnetlink_init(void);
> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 75bab5b0dbae..8e83b7099977 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -3908,6 +3908,25 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
> > >
> > > return skb;
> > > }
> > > +
> > > +static struct netdev_queue *
> > > +netdev_tx_queue_mapping(struct net_device *dev, struct sk_buff *skb)
> > > +{
> > > + int qm = skb_get_queue_mapping(skb);
> > > +
> > > + return netdev_get_tx_queue(dev, netdev_cap_txqueue(dev, qm));
> > > +}
> > > +
> > > +static bool netdev_xmit_txqueue_skipped(void)
> > > +{
> > > + return __this_cpu_read(softnet_data.xmit.skip_txqueue);
> > > +}
> > > +
> > > +void netdev_xmit_skip_txqueue(bool skip)
> > > +{
> > > + __this_cpu_write(softnet_data.xmit.skip_txqueue, skip);
> > > +}
> > > +EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue);
> > > #endif /* CONFIG_NET_EGRESS */
> > >
> > > #ifdef CONFIG_XPS
> > > @@ -4078,7 +4097,7 @@ struct netdev_queue *netdev_core_pick_tx(struct net_device *dev,
> > > static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> > > {
> > > struct net_device *dev = skb->dev;
> > > - struct netdev_queue *txq;
> > > + struct netdev_queue *txq = NULL;
> > > struct Qdisc *q;
> > > int rc = -ENOMEM;
> > > bool again = false;
> > > @@ -4106,11 +4125,17 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> > > if (!skb)
> > > goto out;
> > > }
> > > +
> > > + netdev_xmit_skip_txqueue(false);
> > > +
> > > nf_skip_egress(skb, true);
> > > skb = sch_handle_egress(skb, &rc, dev);
> > > if (!skb)
> > > goto out;
> > > nf_skip_egress(skb, false);
> > > +
> > > + if (netdev_xmit_txqueue_skipped())
> > > + txq = netdev_tx_queue_mapping(dev, skb);
> > > }
> > > #endif
> > > /* If device/qdisc don't need skb->dst, release it right now while
> > > @@ -4121,7 +4146,9 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> > > else
> > > skb_dst_force(skb);
> > >
> > > - txq = netdev_core_pick_tx(dev, skb, sb_dev);
> > > + if (likely(!txq))
> >
> > nit: Drop likely(). If the feature is used from sch_handle_egress(), then this would always be the case.
> Hi Daniel
> I think in most case, we don't use skbedit queue_mapping in the
> sch_handle_egress() , so I add likely in fast path.
> > > + txq = netdev_core_pick_tx(dev, skb, sb_dev);
> > > +
> > > q = rcu_dereference_bh(txq->qdisc);
> >
> > How will the `netdev_xmit_skip_txqueue(true)` be usable from BPF side (see bpf_convert_ctx_access() ->
> > queue_mapping)?
> Good questions, In other patch, I introduce the
> bpf_netdev_skip_txqueue, so we can use netdev_xmit_skip_txqueue in bpf
> side
@Daniel: are you ok with the above explaination?
Thanks!
Paolo
