[PATCH net-next v3] net: Re-use and set mono_delivery_time bit for userspace tstamp packets

From: Abhishek Chauhan
Date: Thu Feb 29 2024 - 21:06:21 EST

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Bridge driver today has no support to forward the userspace timestamp
packets and ends up resetting the timestamp. ETF qdisc checks the
packet coming from userspace and encounters to be 0 thereby dropping
time sensitive packets. These changes will allow userspace timestamps
packets to be forwarded from the bridge to NIC drivers.

Setting the same bit (mono_delivery_time) to avoid dropping of
userspace tstamp packets in the forwarding path.

Existing functionality of mono_delivery_time remains unaltered here,
instead just extended with userspace tstamp support for bridge
forwarding path.

Signed-off-by: Abhishek Chauhan <quic_abchauha@xxxxxxxxxxx>
---
Changes since v2
- Updated the commit subject and message.
- Took care of few comments from Willem to re-use mono_delivery_time
with comments and documentations in the header and source file.
- Took care of comment from Andrew on the typo in the comment.
- Existing self-test test cases are executed to make sure existing
implementation is not impacted as stated by Paolo.(so_txtime.sh).
- Internal validation of UDP packets using iperf/so_priority/so_txtime
with MQPRIO + ETF offload is executed as well.
- Test case is included below

Test 1 :- FQ + ETF (SW path)

[root@ecbldauto-lvarm04-lnx ~]# ./so_txtime.sh
[ 280.640551] q->last time is 1707955476143297550
[ 283.338947] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
[ 284.078429] IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready

SO_TXTIME ipv4 clock monotonic
payload:a delay:109 expected:0 (us)

SO_TXTIME ipv6 clock monotonic
payload:a delay:140 expected:0 (us)

SO_TXTIME ipv6 clock monotonic
payload:a delay:12739 expected:10000 (us)

SO_TXTIME ipv4 clock monotonic
payload:a delay:10054 expected:10000 (us)
payload:b delay:20043 expected:20000 (us)

SO_TXTIME ipv6 clock monotonic
payload:b delay:20078 expected:20000 (us)
payload:a delay:20177 expected:20000 (us)

SO_TXTIME ipv4 clock tai
send: pkt a at -1707955482913ms dropped: invalid txtime
[ 287.070504] now is set to 1707955482913404839
[ 287.070509] tx time from SKB is 0
/so_txtime: recv: timeout: Resource temporarily unavailable

SO_TXTIME ipv6 clock tai
send: pkt a at 0ms dropped: invalid txtime
[ 287.070510] q->last time is 0
[ 287.420590] now is set to 1707955483263491298
[ 287.420596] tx time from SKB is 1707955483263454527
/so_txtime: recv: timeout: Resource temporarily unavailable

SO_TXTIME ipv6 clock tai
[ 287.420597] q->last time is 0
[ 287.700598] now is set to 1707955483543498954
[ 287.700604] tx time from SKB is 1707955483553463173
payload:a delay:9655 expected:10000 (us)

SO_TXTIME ipv4 clock tai
[ 287.700605] q->last time is 0
[ 288.100532] now is set to 1707955483943432391
[ 288.100537] tx time from SKB is 1707955483953413016
payload:a delay:9668 expected:10000 (us)[ 288.100538] q->last time is 1707955483553463173

[ 288.100546] now is set to 1707955483943446975
[ 288.100547] tx time from SKB is 1707955483963413016
payload:b delay:20484 expected:20000 (us)

SO_TXTIME ipv6 clock tai
[ 288.100547] q->last time is 1707955483553463173
[ 288.440582] now is set to 1707955484283482495
[ 288.440587] tx time from SKB is 1707955484303452808
payload:b delay:9648 expected:10000 (us)[ 288.440588] q->last time is 1707955483963413016

[ 288.440598] now is set to 1707955484283499370
payload:a delay:22037 expected:20000 (us)
[ 288.440599] tx time from SKB is 1707955484293452808
OK. All tests passed

Test case 2 (MQPRIO + ETF HW offload)

[root@ecbldauto-lvarm04-lnx ~]# tc qdisc add dev eth0 handle 100: parent root mqprio num_tc 4 \
map 0 2 1 3 3 2 2 2 2 2 2 2 2 2 2 2 \
queues 1@0 1@1 1@2 1@3\
hw 0
[root@ecbldauto-lvarm04-lnx ~]#
tc qdisc replace dev eth0 parent 100:4 etf \
clockid CLOCK_TAI delta 40000 offload skip_sock_check
[ 89.145838] qcom-ethqos 23040000.ethernet eth0: enabled ETF for Queue test log 3, number of queues 4, qopt enable 1, tbs queue bit 1
[ 89.145846] qcom-ethqos 23040000.ethernet eth0: enabled ETF for Queue 3

[root@ecbldauto-lvarm04-lnx ~]# ./a.out -4 -c tai -S 192.168.1.1 -D 192.168.1.2 a,1,b,2

SO_TXTIME ipv4 clock tai

glob_tstat = 1707955395256170394
[ 199.623650] now is set to 1707955395256215810
[ 199.623655] tx time from SKB is 1707955395257170394
[ 199.623656] q->last time is 0
[ 199.623663] now is set to 1707955395256230029
[ 199.623664] tx time from SKB is 1707955395258170394
[ 199.623665] q->last time is 0
[ 199.624589] qcom-ethqos 23040000.ethernet eth0: emac ethqos tx_xmit : lauching tbs packet at 1707955395 sec and 257170394 nsec
[ 199.625573] qcom-ethqos 23040000.ethernet eth0: emac ethqos tx_xmit : lauching tbs packet at 1707955395 sec and 258170394 nsec

Changes since v1
- Changed the commit subject as i am modifying the mono_delivery_time
bit with clockid_delivery_time.
- Took care of suggestion mentioned by Willem to use the same bit for
userspace delivery time as there are no conflicts between TCP and
SCM_TXTIME, because explicit cmsg makes no sense for TCP and only
RAW and DGRAM sockets interprets it.
- Clear explaination of why this is needed mentioned below and this
is extending the work done by Martin for mono_delivery_time
https://patchwork.kernel.org/project/netdevbpf/patch/20220302195525.3480280-1-kafai@xxxxxx/
- Version 1 patch can be referenced with below link which states
the exact problem with tc-etf and discussions which took place
https://lore.kernel.org/all/20240215215632.2899370-1-quic_abchauha@xxxxxxxxxxx/

include/linux/skbuff.h | 4 ++++
net/ipv4/ip_output.c | 7 +++++++
net/ipv4/raw.c | 7 +++++++
net/ipv6/ip6_output.c | 8 +++++++-
net/ipv6/raw.c | 8 +++++++-
net/packet/af_packet.c | 8 +++++++-
6 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2dde34c29203..58586d56b19f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -820,6 +820,10 @@ typedef unsigned char *sk_buff_data_t;
* delivery_time in mono clock base (i.e. EDT). Otherwise, the
* skb->tstamp has the (rcv) timestamp at ingress and
* delivery_time at egress.
+ * This bit is also set for tstamp coming from userspace which
+ * acts as an information in the bridge forwarding path to avoid
+ * resetting the tstamp value when user sets the timestamp using
+ * SO_TXTIME sockopts.
* @napi_id: id of the NAPI struct this skb came from
* @sender_cpu: (aka @napi_id) source CPU in XPS
* @alloc_cpu: CPU which did the skb allocation.
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 5b5a0adb927f..4ae6aea8f8d6 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1455,6 +1455,13 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
skb->priority = (cork->tos != -1) ? cork->priority: READ_ONCE(sk->sk_priority);
skb->mark = cork->mark;
skb->tstamp = cork->transmit_time;
+ /* Timestamp coming from userspace using CMSG is stored as part
+ * of transmit_time as part of cork. To ensure bridge does not
+ * drop the tstamp in the forwarding path.We are reusing bit
+ * mono_delivery_time to avoid reset of tstamp in bridge
+ * forwarding path.
+ */
+ skb->mono_delivery_time = !!skb->tstamp;
/*
* Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
* on dst refcount
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index aea89326c697..6e67c0203be8 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -353,6 +353,13 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
skb->priority = READ_ONCE(sk->sk_priority);
skb->mark = sockc->mark;
skb->tstamp = sockc->transmit_time;
+ /* Timestamp coming from userspace using CMSG is stored as part
+ * of transmit_time as part of sockcmcookie. To ensure bridge does not
+ * drop the tstamp in the forwarding path. We are reusing bit
+ * mono_delivery_time to avoid reset of tstamp in bridge
+ * forwarding path.
+ */
+ skb->mono_delivery_time = !!skb->tstamp;
skb_dst_set(skb, &rt->dst);
*rtp = NULL;

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a722a43dd668..f5b5e13a920f 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1922,7 +1922,13 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
skb->priority = READ_ONCE(sk->sk_priority);
skb->mark = cork->base.mark;
skb->tstamp = cork->base.transmit_time;
-
+ /* Timestamp coming from userspace using CMSG is stored as part
+ * of transmit_time as part of cork. To ensure bridge does not
+ * drop the tstamp in the forwarding path. We are reusing bit
+ * mono_delivery_time to avoid reset of tstamp in bridge
+ * forwarding path.
+ */
+ skb->mono_delivery_time = !!skb->tstamp;
ip6_cork_steal_dst(skb, cork);
IP6_INC_STATS(net, rt->rt6i_idev, IPSTATS_MIB_OUTREQUESTS);
if (proto == IPPROTO_ICMPV6) {
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 03dbb874c363..d2e2a1ec3de4 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -616,7 +616,13 @@ static int rawv6_send_hdrinc(struct sock *sk, struct msghdr *msg, int length,
skb->priority = READ_ONCE(sk->sk_priority);
skb->mark = sockc->mark;
skb->tstamp = sockc->transmit_time;
-
+ /* Timestamp coming from userspace using CMSG is stored as part
+ * of transmit_time as part of sockcmcookie. To ensure bridge does not
+ * drop the tstamp in the forwarding path.We are reusing bit
+ * mono_delivery_time to avoid reset of tstamp in bridge
+ * forwarding path.
+ */
+ skb->mono_delivery_time = !!skb->tstamp;
skb_put(skb, length);
skb_reset_network_header(skb);
iph = ipv6_hdr(skb);
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c9bbc2686690..949e936b5786 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2057,7 +2057,13 @@ static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg,
skb->priority = READ_ONCE(sk->sk_priority);
skb->mark = READ_ONCE(sk->sk_mark);
skb->tstamp = sockc.transmit_time;
-
+ /* Timestamp coming from userspace using CMSG is stored as part
+ * of transmit_time as part of sockcmcookie. To ensure bridge does not
+ * drop the tstamp in the forwarding path. We are reusing bit
+ * mono_delivery_time to avoid reset of tstamp in bridge
+ * forwarding path.
+ */
+ skb->mono_delivery_time = !!skb->tstamp;
skb_setup_tx_timestamp(skb, sockc.tsflags);

if (unlikely(extra_len == 4))
--
2.25.1

Next message: Kunwu Chan: "Re: [PATCH] nfs: use KMEM_CACHE() to create nfs_commit_data cache"
Previous message: Chao Yu: "Re: [PATCH] f2fs: introduce SEGS_TO_BLKS/BLKS_TO_SEGS for cleanup"
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