On Wed, Mar 02, 2022 at 12:30:14PM -0800, Eric Dumazet wrote:
> On Wed, Mar 2, 2022 at 11:56 AM Martin KaFai Lau <kafai@xxxxxx> wrote:
> >
> > The previous patches handled the delivery_time in the ingress path
> > before the routing decision is made. This patch can postpone clearing
> > delivery_time in a skb until knowing it is delivered locally and also
> > set the (rcv) timestamp if needed. This patch moves the
> > skb_clear_delivery_time() from dev.c to ip_local_deliver_finish()
> > and ip6_input_finish().
> >
> > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> > ---
> > net/core/dev.c | 8 ++------
> > net/ipv4/ip_input.c | 1 +
> > net/ipv6/ip6_input.c | 1 +
> > 3 files changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 0fc02cf32476..3ff686cc8c84 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -5193,10 +5193,8 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
> > goto out;
> > }
> >
> > - if (skb_skip_tc_classify(skb)) {
> > - skb_clear_delivery_time(skb);
> > + if (skb_skip_tc_classify(skb))
> > goto skip_classify;
> > - }
> >
> > if (pfmemalloc)
> > goto skip_taps;
> > @@ -5225,14 +5223,12 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc,
> > goto another_round;
> > if (!skb)
> > goto out;
> > - skb_clear_delivery_time(skb);
> >
> > nf_skip_egress(skb, false);
> > if (nf_ingress(skb, &pt_prev, &ret, orig_dev) < 0)
> > goto out;
> > - } else
> > + }
> > #endif
> > - skb_clear_delivery_time(skb);
> > skb_reset_redirect(skb);
> > skip_classify:
> > if (pfmemalloc && !skb_pfmemalloc_protocol(skb))
> > diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> > index d94f9f7e60c3..95f7bb052784 100644
> > --- a/net/ipv4/ip_input.c
> > +++ b/net/ipv4/ip_input.c
> > @@ -226,6 +226,7 @@ void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int protocol)
> >
> > static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
> > {
> > + skb_clear_delivery_time(skb);
> > __skb_pull(skb, skb_network_header_len(skb));
> >
> > rcu_read_lock();
> > diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
> > index d4b1e2c5aa76..5b5ea35635f9 100644
> > --- a/net/ipv6/ip6_input.c
> > +++ b/net/ipv6/ip6_input.c
> > @@ -459,6 +459,7 @@ void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
> >
> > static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
> > {
> > + skb_clear_delivery_time(skb);
> > rcu_read_lock();
> > ip6_protocol_deliver_rcu(net, skb, 0, false);
> > rcu_read_unlock();
> > --
> > 2.30.2
> >
>
> It is not clear to me why we need to clear tstamp if packet is locally
> delivered ?
It does not clear the rx tstamp in skb->tstamp.
It only clears the EDT in skb->tstamp when the skb
is transmitted out of a local tcp_sock and then loop back from egress
to ingress through virtual interface like veth.
>
> TCP stack is using tstamp for incoming packets (look for
> TCP_SKB_CB(skb)->has_rxtstamp)
skb_clear_delivery_time() will put ktime_get_real() back to skb->tstamp
so that the receiving tcp_sock can use it.
