summaryrefslogtreecommitdiff
path: root/net/ipv4/ip_output.c
diff options
context:
space:
mode:
authorMartin KaFai Lau <kafai@fb.com>2022-03-02 11:55:25 -0800
committerDavid S. Miller <davem@davemloft.net>2022-03-03 14:38:48 +0000
commita1ac9c8acec1605c6b43af418f79facafdced680 (patch)
treecf89b2e7b2f5f92400c51eee74558c64674d5207 /net/ipv4/ip_output.c
parent6fb8661c8f97bb062d2ecc7a57591d38e6c4f8c8 (diff)
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 'net/ipv4/ip_output.c')
-rw-r--r--net/ipv4/ip_output.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 6df3545c891d..a9588e0c82c5 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -761,6 +761,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
{
struct iphdr *iph;
struct sk_buff *skb2;
+ bool mono_delivery_time = skb->mono_delivery_time;
struct rtable *rt = skb_rtable(skb);
unsigned int mtu, hlen, ll_rs;
struct ip_fraglist_iter iter;
@@ -852,7 +853,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
}
}
- skb->tstamp = tstamp;
+ skb_set_delivery_time(skb, tstamp, mono_delivery_time);
err = output(net, sk, skb);
if (!err)
@@ -908,7 +909,7 @@ slow_path:
/*
* Put this fragment into the sending queue.
*/
- skb2->tstamp = tstamp;
+ skb_set_delivery_time(skb2, tstamp, mono_delivery_time);
err = output(net, sk, skb2);
if (err)
goto fail;
@@ -1727,6 +1728,8 @@ void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
arg->csumoffset) = csum_fold(csum_add(nskb->csum,
arg->csum));
nskb->ip_summed = CHECKSUM_NONE;
+ /* Setting mono_delivery_time will be enabled later */
+ nskb->mono_delivery_time = 0;
ip_push_pending_frames(sk, &fl4);
}
out: