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From: Abhishek Chauhan <quic_abchauha@quicinc.com>
To: "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Andrew Halaney <ahalaney@redhat.com>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Martin KaFai Lau <martin.lau@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>
Cc: kernel@quicinc.com
Subject: [PATCH net-next v4] net: Re-use and set mono_delivery_time bit for userspace tstamp packets
Date: Fri,  1 Mar 2024 12:13:48 -0800
Message-Id: <20240301201348.2815102-1-quic_abchauha@quicinc.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

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@quicinc.com>
---
Changes since v3
- Setting mono_delivery_time at all instances where the skb->tstamp is 
  initialized with sockcm.transmit_time as reviewed by Willem
- Removed repetitive comments from all the sources file and limited only
  to skbuff.h as suggested by Willem
- Re-phrased the comment explanation in skbuff.h and made it much simpler 
  and generic as suggested by Willem 

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@fb.com/
- 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@quicinc.com/ 

 include/linux/skbuff.h | 6 +++---
 net/ipv4/ip_output.c   | 1 +
 net/ipv4/raw.c         | 1 +
 net/ipv6/ip6_output.c  | 2 +-
 net/ipv6/raw.c         | 2 +-
 net/packet/af_packet.c | 4 +++-
 6 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2dde34c29203..4726298d4ed4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -817,9 +817,9 @@ typedef unsigned char *sk_buff_data_t;
  *	@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.
+ *		delivery_time in mono clock base (i.e., EDT) or a clock base chosen
+ *		by SO_TXTIME. If zero, skb->tstamp has the (rcv) timestamp at
+ *		ingress.
  *	@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..ff1df64c5697 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1455,6 +1455,7 @@ 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;
+	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..c4c29fc5b73f 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -353,6 +353,7 @@ 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;
+	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..2fc1d03dc07d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1922,7 +1922,7 @@ 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;
-
+	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..13f54f8eea35 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -616,7 +616,7 @@ 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;
-
+	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..0db31ca4982d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2057,7 +2057,7 @@ 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;
-
+	skb->mono_delivery_time = !!skb->tstamp;
 	skb_setup_tx_timestamp(skb, sockc.tsflags);
 
 	if (unlikely(extra_len == 4))
@@ -2586,6 +2586,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
 	skb->priority = READ_ONCE(po->sk.sk_priority);
 	skb->mark = READ_ONCE(po->sk.sk_mark);
 	skb->tstamp = sockc->transmit_time;
+	skb->mono_delivery_time = !!skb->tstamp;
 	skb_setup_tx_timestamp(skb, sockc->tsflags);
 	skb_zcopy_set_nouarg(skb, ph.raw);
 
@@ -3064,6 +3065,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	skb->priority = READ_ONCE(sk->sk_priority);
 	skb->mark = sockc.mark;
 	skb->tstamp = sockc.transmit_time;
+	skb->mono_delivery_time = !!skb->tstamp;
 
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;
-- 
2.25.1