<html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> </head> <body> <div name="messageBodySection"> <div>Hello,</div> <div>As advised, I checked the TCP timestamp and found that the RX HW timestamp appears to be replaced by the TCP timestamp in LROed packets. This is a very weird bug...</div> <div> </div> <div>[port 0] RX HW timestamp: 0x00001208f2a8d6c7, TCP timestamp: 0x669efc3b6a269469 (tsval: 1721695291, tsecr: 1780913257) (not LROed) [port 0] RX HW timestamp: 0x669efc3b6a26946a, TCP timestamp: 0x669efc3b6a26946a (tsval: 1721695291, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x669efc3b6a26946a, TCP timestamp: 0x669efc3b6a26946a (tsval: 1721695291, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x669efc3b6a26946a, TCP timestamp: 0x669efc3b6a26946a (tsval: 1721695291, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x00001208f2b05907, TCP timestamp: 0x669efc3b6a26946a (tsval: 1721695291, tsecr: 1780913258) (not LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946a, TCP timestamp: 0x669efc3c6a26946a (tsval: 1721695292, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946a, TCP timestamp: 0x669efc3c6a26946a (tsval: 1721695292, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946a, TCP timestamp: 0x669efc3c6a26946a (tsval: 1721695292, tsecr: 1780913258) (LROed) [port 0] RX HW timestamp: 0x00001208f2b8f191, TCP timestamp: 0x669efc3c6a26946a (tsval: 1721695292, tsecr: 1780913258) (not LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946b, TCP timestamp: 0x669efc3c6a26946b (tsval: 1721695292, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946b, TCP timestamp: 0x669efc3c6a26946b (tsval: 1721695292, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x669efc3c6a26946b, TCP timestamp: 0x669efc3c6a26946b (tsval: 1721695292, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x00001208f2c0689b, TCP timestamp: 0x669efc3c6a26946b (tsval: 1721695292, tsecr: 1780913259) (not LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946b, TCP timestamp: 0x669efc3d6a26946b (tsval: 1721695293, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946b, TCP timestamp: 0x669efc3d6a26946b (tsval: 1721695293, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946b, TCP timestamp: 0x669efc3d6a26946b (tsval: 1721695293, tsecr: 1780913259) (LROed) [port 0] RX HW timestamp: 0x00001208f2c83627, TCP timestamp: 0x669efc3d6a26946b (tsval: 1721695293, tsecr: 1780913259) (not LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946c, TCP timestamp: 0x669efc3d6a26946c (tsval: 1721695293, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946c, TCP timestamp: 0x669efc3d6a26946c (tsval: 1721695293, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x669efc3d6a26946c, TCP timestamp: 0x669efc3d6a26946c (tsval: 1721695293, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x00001208f2cfa33b, TCP timestamp: 0x669efc3d6a26946c (tsval: 1721695293, tsecr: 1780913260) (not LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946c, TCP timestamp: 0x669efc3e6a26946c (tsval: 1721695294, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946c, TCP timestamp: 0x669efc3e6a26946c (tsval: 1721695294, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946c, TCP timestamp: 0x669efc3e6a26946c (tsval: 1721695294, tsecr: 1780913260) (LROed) [port 0] RX HW timestamp: 0x00001208f2d8605d, TCP timestamp: 0x669efc3e6a26946c (tsval: 1721695294, tsecr: 1780913260) (not LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946d, TCP timestamp: 0x669efc3e6a26946d (tsval: 1721695294, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946d, TCP timestamp: 0x669efc3e6a26946d (tsval: 1721695294, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x669efc3e6a26946d, TCP timestamp: 0x669efc3e6a26946d (tsval: 1721695294, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x00001208f2dfd977, TCP timestamp: 0x669efc3f6a26946d (tsval: 1721695295, tsecr: 1780913261) (not LROed) [port 0] RX HW timestamp: 0x669efc3f6a26946d, TCP timestamp: 0x669efc3f6a26946d (tsval: 1721695295, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x669efc3f6a26946d, TCP timestamp: 0x669efc3f6a26946d (tsval: 1721695295, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x669efc3f6a26946d, TCP timestamp: 0x669efc3f6a26946d (tsval: 1721695295, tsecr: 1780913261) (LROed) [port 0] RX HW timestamp: 0x00001208f2e78fab, TCP timestamp: 0x669efc3f6a26946d (tsval: 1721695295, tsecr: 1780913261) (not LROed)</div> </div> <div name="messageSignatureSection"> <div>Sincerely,</div> <div>Junghan Yoon</div> </div> <div name="messageReplySection">On Jul 24, 2025, 5:40 PM +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: <blockquote type="cite">On Thu, 24 Jul 2025, Yoon Junghan wrote: <blockquote type="cite" style="border-left-color: grey; border-left-width: thin; border-left-style: solid; margin: 5px 5px;padding-left: 10px;">I found the key difference: when TCP timestamps (RFC 7323) are enabled on the TCP sender, the RX HW timestamp of LROed packets on the DPDK PMD on middlebox machine becomes inconsistent or invalid. Is there a known limitation or erratum in the mlx5 driver or CX7 firmware regarding this? </blockquote> Very interesting observation. So did you have TCP timestamps enabled on those sender NICs that match the receiver NICs that would fail to do HW timestamp and did you have it disabled on links where HW timestamp was OK on receiver? But in the case of LRO on such NICs that have wrong HW timestamp, is the TCP timestamp option present in a LROed packet and does it have accurate value? Regarding erratum, - I have to confess I'm not an expert in this particular driver. May be they have some official documentation regarding this somewhere. Thank you. <blockquote type="cite" style="border-left-color: grey; border-left-width: thin; border-left-style: solid; margin: 5px 5px;padding-left: 10px;"> Sincerely, Junghan Yoon On Jul 24, 2025, 12:26 AM +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: On Thu, 24 Jul 2025, Yoon Junghan wrote: I'm not sure I did well. All interface show the same result. current settings: tx_type 0 rx_filter 0 But that should mean.. no timestamping? 1) May be also check 'sudo ethtool -T <ifname>'. 2) May be try to enable 'sudo hwstamp_ctl -i <ifname> -r 1'. Thank you. Sincerely, Junghan Yoon On 2025년 7월 23일 PM 11:19 +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: On Wed, 23 Jul 2025, Yoon Junghan wrote: I isolated port 1 using -a option for EAL parameter and got the similar result. Note that port 1 becomes port 0 in this time. [port 0] RX HW timestamp: 0x3eac4214bc574368 (LROed) [port 0] RX HW timestamp: 0x3eac4214bc574368 (LROed) [port 0] RX HW timestamp: 0x3eac4214bc574368 (LROed) [port 0] RX HW timestamp: 0x3eac4214bc574368 (LROed) [port 0] RX HW timestamp: 0x00042819272fad (not LROed) [port 0] RX HW timestamp: 0x000428192e6e77 (not LROed) [port 0] RX HW timestamp: 0x000428192e7f01 (not LROed) [port 0] RX HW timestamp: 0x000428192e833d (not LROed) FYI, I have 4 CX-7 on the same machine. (eth0 = port 0, ... eth3 = port 3 in DPDK) pci@0000:16:00.0 eth0 network MT2910 Family [ConnectX-7] pci@0000:40:00.0 eth1 network MT2910 Family [ConnectX-7] pci@0000:6a:00.0 eth2 network MT2910 Family [ConnectX-7] pci@0000:94:00.0 eth3 network MT2910 Family [ConnectX-7] Among them, only the first CX-7 shows consistent timestamp regardless of LRO. Does 'sudo hwstamp_ctl -i <ifname>' show consistent results across all the NICs? Thank you. Sincerely, Junghan Yoon On 2025년 7월 23일 PM 10:28 +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: On Wed, 23 Jul 2025, Yoon Junghan wrote: Thank you for quick response. 1) They are different NICs. Not in the same board. Separate adapters in different PCIe slots. 2) My DPDK app uses 4 separate ports; port 0, port 1, port 2, and port 3. They are all on different boards. Thus, they are running at the same time. Excellent. I apologise for one more dumb question, but does isolating the very specific NIC (so that DPDK does not grab the other ones) that is known to give strange timestamps, result in the same/unexpected behaviour? Just to make sure. Thank you. Sincerely, Junghan Yoon On 2025년 7월 23일 PM 10:09 +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: Hello, On Wed, 23 Jul 2025, Yoon Junghan wrote: Hello, As advised, I tested hardware timestamps with LRO enabled on our ConnectX-7 NICs. However, the timestamps of LROed packets still show inconsistent and abnormally large gaps from normal packets. Interestingly, I found this issue does not appear on all CX-7 NICs. Even with identical DPDK code, firmware version (28.43.2566), and hardware models from the same manufacturer, only specific NICs exhibit this inconsistency. I have confirmed that: * All NICs use the same driver and firmware version. * All NICs are of the same model (MCX75310AAS-NEA_Ax). 1) Do the two "NICs" ('port 0' and 'port 1' from below printout) represent two different ports/PFs of the same physical 'board'/'adapter card' in fact? 2) If (1) is true, were the results obtained by running the application on both ports simultaneously (both managed by the DPDK at the same time)? (just to clarify, -- I'm confused by the fact that the NIC driver itself seems to invoke 'rte_mbuf_dyn_rx_timestamp_register' for each new RxQ rather than call it once and then look-up and reuse the existing offsets for more ports/queue ). Thank you. * The issue occurs only when LRO is enabled together with RX hardware timestamping. * Disabling LRO eliminates the issue. I would appreciate any insight into how this behavior can occur on only some ports despite same software and hardware setup. Below is my code snippet. ```c /*----------------------------------------------------------------------------*/ static inline int is_timestamp_enabled(struct rte_mbuf *mbuf) { static uint64_t timestamp_rx_dynflag = 0; int timestamp_rx_dynflag_offset; if (!timestamp_rx_dynflag) { timestamp_rx_dynflag_offset = rte_mbuf_dynflag_lookup(RTE_MBUF_DYNFLAG_RX_TIMESTAMP_NAME, NULL); if (timestamp_rx_dynflag_offset < 0) { return 0; } timestamp_rx_dynflag = RTE_BIT64(timestamp_rx_dynflag_offset); } return mbuf->ol_flags & timestamp_rx_dynflag; } /*----------------------------------------------------------------------------*/ static inline rte_mbuf_timestamp_t * get_timestamp(struct rte_mbuf *mbuf) { static int timestamp_dynfield_offset = -1; if (timestamp_dynfield_offset < 0) { timestamp_dynfield_offset = rte_mbuf_dynfield_lookup(RTE_MBUF_DYNFIELD_TIMESTAMP_NAME, NULL); if (timestamp_dynfield_offset < 0) { return 0; } } return RTE_MBUF_DYNFIELD(mbuf, timestamp_dynfield_offset, rte_mbuf_timestamp_t *); } /*----------------------------------------------------------------------------*/ static inline rte_mbuf_timestamp_t * get_rx_hw_timestamp(struct rte_mbuf *pkt) { if (!is_timestamp_enabled(pkt)) { printf("rx_hw_timestamp not enabled in mbuf!\n"); return NULL; } return get_timestamp(pkt); } ``` My DPDK application prints logs as below. ```c /* parse HW timestamp */ rte_mbuf_timestamp_t *rx_timestamp = get_rx_hw_timestamp(pkt); printf("[port %d] RX HW timestamp: %#016lx %s\n", pctx->port_id, *rx_timestamp, pkt->ol_flags & PKT_RX_LRO ? "(LROed)" : "(not LROed)"); ``` Below are observations from two CX-7 ports under identical conditions. Normal NIC (port 0): [port 0] RX HW timestamp: 0x00007dcd2d185b (LROed) [port 0] RX HW timestamp: 0x00007dcd2d1911 (LROed) [port 0] RX HW timestamp: 0x00007dcd2d19c9 (LROed) [port 0] RX HW timestamp: 0x00007dcd2d37ca (LROed) [port 0] RX HW timestamp: 0x00007dcd2d4cb3 (not LROed) [port 0] RX HW timestamp: 0x00007dcd2d4cb3 (not LROed) [port 0] RX HW timestamp: 0x00007dcd30e019 (not LROed) [port 0] RX HW timestamp: 0x00007dcd3280bb (not LROed) Erroneous NIC (port 1): Below is erroneous NIC's timestamp. [port 1] RX HW timestamp: 0x3e6eef91bc19f0fd (LROed) [port 1] RX HW timestamp: 0x3e6eef91bc19f0fd (LROed) [port 1] RX HW timestamp: 0x3e6eef91bc19f0fd (LROed) [port 1] RX HW timestamp: 0x3e6eef91bc19f0fd (LROed) [port 1] RX HW timestamp: 0x000080691b7557 (not LROed) [port 1] RX HW timestamp: 0x000080691e2311 (not LROed) [port 1] RX HW timestamp: 0x00008069357553 (not LROed) [port 1] RX HW timestamp: 0x0000806936e8c1 (not LROed) As shown above, non-LRO packets consistently have normal hardware timestamps on both NICs. However, on port 1, all LROed packets return a fixed, invalid timestamp (0x3e6eef91bc19f0fd), which is clearly inconsistent. I have also confirmed that other dynfields (rather than dynfield[1] and dynfield[2]) are unused. Sincerely, Junghan Yoon On Jul 22, 2025, 5:31 PM +0900, Ivan Malov <ivan.malov@arknetworks.am>, wrote: Hello, On Tue, 22 Jul 2025, Yoon Junghan wrote: Hello, I'm currently using DPDK 20.11 with a ConnectX-7 NIC, and I'm trying to retrieve RX hardware timestamps using `rte_mbuf_dyn_rx_timestamp_register()`. Does the application invoke 'rte_mbuf_dyn_rx_timestamp_register' on its own? If yes, consider to replace this with invocations of APIs [1] (with field name [2]) and [3] (with flag name [4]). For an example, please refer to [5] and [6]. This is because, as per [7], the driver in question might 'register' the field and the flag on its own, in response to 'DEV_RX_OFFLOAD_TIMESTAMP' request, so, the user application should look up the field/flag, not 'register' it afresh. If this does not help, then consider to clarify whether the timestamps are accurate (and whether the flag is seen in the mbufs) when LRO is not enabled. [1] https://doc.dpdk.org/api-20.11/rte__mbuf__dyn_8h.html#a6adf9b352a83e7d521fd6aa04e305b1c [2] https://doc.dpdk.org/api-20.11/rte__mbuf__dyn_8h.html#a5159b2d34fa801d171ed0ccce451121b [3] https://doc.dpdk.org/api-20.11/rte__mbuf__dyn_8h.html#a89d835027034f76a27eb2afe7987ae35 [4] https://doc.dpdk.org/api-20.11/rte__mbuf__dyn_8h.html#a831d7066c7193788351797a65186848a [5] https://github.com/DPDK/dpdk/blob/d69724b1dcc69784bcef00b96597469b7f6e6207/app/test-pmd/util.c#L44 [6] https://github.com/DPDK/dpdk/blob/d69724b1dcc69784bcef00b96597469b7f6e6207/app/test-pmd/util.c#L60 [7] https://github.com/DPDK/dpdk/blob/d69724b1dcc69784bcef00b96597469b7f6e6207/drivers/net/mlx5/mlx5_rxq.c#L1743 Thank you. When LRO is enabled, I notice that LROed mbufs seem to share identical timestamp values, and the timestamps are unexpectedly large or inconsistent. This raises the question of whether LRO is interfering with the correctness of the RX HW timestamps. I’d appreciate any clarification on whether HW RX timestamping is reliable when LRO is enabled on this platform, or if LRO should be just disabled for accurate per-packet timestamping. Sincerely, Junghan Yoon </blockquote> </blockquote> </div> </body> </html>