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

  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 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 | 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(-)
  

Abhishek Chauhan wrote:
> 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 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 | 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.

There are multiple applications of this information aside from
bridging. I'd drop that and instead rewrite the existing. Something
like

"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..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;

This patch adds too much verbose commentary, repeated multiple times,
for such a small change. Keep only the comment in skbuff.h.

>  	/*
>  	 * 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;

Search for all occurrences of skb->tstamp getting initialized from
sockc.transmit_time. af_packet.c has three such cases.

>  	skb_setup_tx_timestamp(skb, sockc.tsflags);
>  
>  	if (unlikely(extra_len == 4))
> -- 
> 2.25.1
>
  

On 3/1/2024 10:45 AM, Willem de Bruijn wrote:
> Abhishek Chauhan wrote:
>> 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 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 | 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.
> 
> There are multiple applications of this information aside from
> bridging. I'd drop that and instead rewrite the existing. Something
> like
> 
> "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."
> 

Will make the changes accordingly. 

>>   *	@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;
> 
> This patch adds too much verbose commentary, repeated multiple times,
> for such a small change. Keep only the comment in skbuff.h.
> 

Got it. I was thinking of the same. I will make the change. 

>>  	/*
>>  	 * 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;
> 
> Search for all occurrences of skb->tstamp getting initialized from
> sockc.transmit_time. af_packet.c has three such cases.
> 

Let me check and add at every instance. 

>>  	skb_setup_tx_timestamp(skb, sockc.tsflags);
>>  
>>  	if (unlikely(extra_len == 4))
>> -- 
>> 2.25.1
>>
> 
>