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author | 2022-03-02 11:55:25 -0800 | |
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committer | 2022-03-03 14:38:48 +0000 | |
commit | a1ac9c8acec1605c6b43af418f79facafdced680 (patch) | |
tree | cf89b2e7b2f5f92400c51eee74558c64674d5207 /include/linux/skbuff.h | |
parent | Merge branch 'dsa-unicast-filtering' (diff) | |
download | linux-a1ac9c8acec1605c6b43af418f79facafdced680.tar.gz linux-a1ac9c8acec1605c6b43af418f79facafdced680.tar.bz2 linux-a1ac9c8acec1605c6b43af418f79facafdced680.zip |
net: Add skb->mono_delivery_time to distinguish mono delivery_time from (rcv) timestamp
skb->tstamp was first used as the (rcv) timestamp.
The major usage is to report it to the user (e.g. SO_TIMESTAMP).
Later, skb->tstamp is also set as the (future) delivery_time (e.g. EDT in TCP)
during egress and used by the qdisc (e.g. sch_fq) to make decision on when
the skb can be passed to the dev.
Currently, there is no way to tell skb->tstamp having the (rcv) timestamp
or the delivery_time, so it is always reset to 0 whenever forwarded
between egress and ingress.
While it makes sense to always clear the (rcv) timestamp in skb->tstamp
to avoid confusing sch_fq that expects the delivery_time, it is a
performance issue [0] to clear the delivery_time if the skb finally
egress to a fq@phy-dev. For example, when forwarding from egress to
ingress and then finally back to egress:
tcp-sender => veth@netns => veth@hostns => fq@eth0@hostns
^ ^
reset rest
This patch adds one bit skb->mono_delivery_time to flag the skb->tstamp
is storing the mono delivery_time (EDT) instead of the (rcv) timestamp.
The current use case is to keep the TCP mono delivery_time (EDT) and
to be used with sch_fq. A latter patch will also allow tc-bpf@ingress
to read and change the mono delivery_time.
In the future, another bit (e.g. skb->user_delivery_time) can be added
for the SCM_TXTIME where the clock base is tracked by sk->sk_clockid.
[ This patch is a prep work. The following patches will
get the other parts of the stack ready first. Then another patch
after that will finally set the skb->mono_delivery_time. ]
skb_set_delivery_time() function is added. It is used by the tcp_output.c
and during ip[6] fragmentation to assign the delivery_time to
the skb->tstamp and also set the skb->mono_delivery_time.
A note on the change in ip_send_unicast_reply() in ip_output.c.
It is only used by TCP to send reset/ack out of a ctl_sk.
Like the new skb_set_delivery_time(), this patch sets
the skb->mono_delivery_time to 0 for now as a place
holder. It will be enabled in a latter patch.
A similar case in tcp_ipv6 can be done with
skb_set_delivery_time() in tcp_v6_send_response().
[0] (slide 22): https://linuxplumbersconf.org/event/11/contributions/953/attachments/867/1658/LPC_2021_BPF_Datapath_Extensions.pdf
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
-rw-r--r-- | include/linux/skbuff.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index d67941f78b92..803ffa63dea6 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -795,6 +795,10 @@ typedef unsigned char *sk_buff_data_t; * @dst_pending_confirm: need to confirm neighbour * @decrypted: Decrypted SKB * @slow_gro: state present at GRO time, slower prepare step required + * @mono_delivery_time: When set, skb->tstamp has the + * delivery_time in mono clock base (i.e. EDT). Otherwise, the + * skb->tstamp has the (rcv) timestamp at ingress and + * delivery_time at egress. * @napi_id: id of the NAPI struct this skb came from * @sender_cpu: (aka @napi_id) source CPU in XPS * @secmark: security marking @@ -965,6 +969,7 @@ struct sk_buff { __u8 decrypted:1; #endif __u8 slow_gro:1; + __u8 mono_delivery_time:1; #ifdef CONFIG_NET_SCHED __u16 tc_index; /* traffic control index */ @@ -3983,6 +3988,14 @@ static inline ktime_t net_timedelta(ktime_t t) return ktime_sub(ktime_get_real(), t); } +static inline void skb_set_delivery_time(struct sk_buff *skb, ktime_t kt, + bool mono) +{ + skb->tstamp = kt; + /* Setting mono_delivery_time will be enabled later */ + skb->mono_delivery_time = 0; +} + static inline u8 skb_metadata_len(const struct sk_buff *skb) { return skb_shinfo(skb)->meta_len; |