* RE: [PATCH net] igc: only strip RX timestamp header from first buffer
2026-08-25 23:55 [PATCH net] igc: only strip RX timestamp header from first buffer Paul Moses
@ 2026-08-26 12:51 ` Loktionov, Aleksandr
2026-08-27 15:14 ` Maciej Fijalkowski
2026-09-02 8:44 ` Dahan, AvigailX
2 siblings, 0 replies; 4+ messages in thread
From: Loktionov, Aleksandr @ 2026-08-26 12:51 UTC (permalink / raw)
To: Paul Moses, intel-wired-lan@lists.osuosl.org
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Nguyen, Anthony L, Kitszel, Przemyslaw, andrew+netdev@lunn.ch,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, Fijalkowski, Maciej, andre.guedes@intel.com,
vedang.patel@intel.com, jithu.joseph@intel.com,
richardcochran@gmail.com, tkusters@aweta.nl,
stable@vger.kernel.org
> -----Original Message-----
> From: Paul Moses <p@1g4.org>
> Sent: Wednesday, August 26, 2026 1:56 AM
> To: intel-wired-lan@lists.osuosl.org
> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Nguyen,
> Anthony L <anthony.l.nguyen@intel.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@intel.com>; andrew+netdev@lunn.ch;
> davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; Fijalkowski, Maciej <maciej.fijalkowski@intel.com>;
> andre.guedes@intel.com; vedang.patel@intel.com;
> jithu.joseph@intel.com; richardcochran@gmail.com; tkusters@aweta.nl;
> stable@vger.kernel.org
> Subject: [PATCH net] igc: only strip RX timestamp header from first
> buffer
>
> igc_clean_rx_irq() strips IGC_TS_HDR_LEN whenever a descriptor reports
> IGC_RXDADV_STAT_TSIP. For multi-buffer packets, continuation
> descriptors
> retain TSIP even though the inline timestamp is present only in the
> first
> RX buffer.
>
> Subtracting the header length from each continuation buffer truncates
> jumbo packets by 16 bytes per continuation and leaves the packet
> length
> larger than the received data.
>
> Only consume the timestamp header when skb is NULL, which identifies
> the
> first buffer of a new packet. An skb carried in rx_ring->skb remains
> non-NULL when packet assembly resumes in a later NAPI poll.
>
> Link: https://lore.kernel.org/all/20260625-igb-rx-ts-fix-v3-1-
> 99b3efa08dca@aweta.nl/
> Fixes: e1ed4f92a625 ("igc: Refactor Rx timestamp handling")
> Cc: stable@vger.kernel.org
> Signed-off-by: Paul Moses <p@1g4.org>
> ---
> #
> # REPRO
> #
> # Receiver: igc / enp1s0 / 10.0.5.175
> # Sender: RTL8125B / enP4p65s0 / 10.0.5.165
>
> # Both hosts
> sudo ip link set dev enp1s0 mtu 9000
> sudo ip link set dev enP4p65s0 mtu 9000
>
> # Baseline: RX timestamping off
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> # Enable RX timestamping only
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 1
>
> # Receiver
> sudo timeout 20 tcpdump -ni enp1s0 -s 0 -w /tmp/igc-jumbo.pcap \
> 'icmp and host 10.0.5.165'
>
> # Sender
> ping -n -M do -c 5 -W 2 -s 8972 10.0.5.175
> # 0/5 received
>
> # Receiver
> sudo tcpdump -nn -e -vvv -r /tmp/igc-jumbo.pcap
> # length 8950
> # [total length 9000 > length 8936] (invalid)
> # wrong icmp cksum
>
> # Expected Ethernet length: 9014
> # Captured length: 8950
> # Loss: 64 = 4 continuation buffers * 16 bytes
>
> # Disable RX timestamping again
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> ---
>
> drivers/net/ethernet/intel/igc/igc_main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
> b/drivers/net/ethernet/intel/igc/igc_main.c
> index 1fb5f3cbe93c..41b293dc10c3 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2639,7 +2639,8 @@ static int igc_clean_rx_irq(struct igc_q_vector
> *q_vector, const int budget)
>
> pktbuf = page_address(rx_buffer->page) + rx_buffer-
> >page_offset;
>
> - if (igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> + if (!skb &&
> + igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> ctx.rx_ts = pktbuf;
> pkt_offset = IGC_TS_HDR_LEN;
> size -= IGC_TS_HDR_LEN;
> --
> 2.55.GIT
>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH net] igc: only strip RX timestamp header from first buffer
2026-08-25 23:55 [PATCH net] igc: only strip RX timestamp header from first buffer Paul Moses
2026-08-26 12:51 ` Loktionov, Aleksandr
@ 2026-08-27 15:14 ` Maciej Fijalkowski
2026-09-02 8:44 ` Dahan, AvigailX
2 siblings, 0 replies; 4+ messages in thread
From: Maciej Fijalkowski @ 2026-08-27 15:14 UTC (permalink / raw)
To: Paul Moses
Cc: intel-wired-lan, netdev, linux-kernel, anthony.l.nguyen,
przemyslaw.kitszel, andrew+netdev, davem, edumazet, kuba, pabeni,
andre.guedes, vedang.patel, jithu.joseph, richardcochran,
tkusters, stable
On Tue, Aug 25, 2026 at 11:55:40PM +0000, Paul Moses wrote:
> igc_clean_rx_irq() strips IGC_TS_HDR_LEN whenever a descriptor reports
> IGC_RXDADV_STAT_TSIP. For multi-buffer packets, continuation descriptors
> retain TSIP even though the inline timestamp is present only in the first
> RX buffer.
>
> Subtracting the header length from each continuation buffer truncates
> jumbo packets by 16 bytes per continuation and leaves the packet length
> larger than the received data.
>
> Only consume the timestamp header when skb is NULL, which identifies the
> first buffer of a new packet. An skb carried in rx_ring->skb remains
> non-NULL when packet assembly resumes in a later NAPI poll.
>
> Link: https://lore.kernel.org/all/20260625-igb-rx-ts-fix-v3-1-99b3efa08dca@aweta.nl/
> Fixes: e1ed4f92a625 ("igc: Refactor Rx timestamp handling")
> Cc: stable@vger.kernel.org
> Signed-off-by: Paul Moses <p@1g4.org>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> ---
> #
> # REPRO
> #
> # Receiver: igc / enp1s0 / 10.0.5.175
> # Sender: RTL8125B / enP4p65s0 / 10.0.5.165
>
> # Both hosts
> sudo ip link set dev enp1s0 mtu 9000
> sudo ip link set dev enP4p65s0 mtu 9000
>
> # Baseline: RX timestamping off
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> # Enable RX timestamping only
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 1
>
> # Receiver
> sudo timeout 20 tcpdump -ni enp1s0 -s 0 -w /tmp/igc-jumbo.pcap \
> 'icmp and host 10.0.5.165'
>
> # Sender
> ping -n -M do -c 5 -W 2 -s 8972 10.0.5.175
> # 0/5 received
>
> # Receiver
> sudo tcpdump -nn -e -vvv -r /tmp/igc-jumbo.pcap
> # length 8950
> # [total length 9000 > length 8936] (invalid)
> # wrong icmp cksum
>
> # Expected Ethernet length: 9014
> # Captured length: 8950
> # Loss: 64 = 4 continuation buffers * 16 bytes
>
> # Disable RX timestamping again
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> ---
>
> drivers/net/ethernet/intel/igc/igc_main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 1fb5f3cbe93c..41b293dc10c3 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -2639,7 +2639,8 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
>
> pktbuf = page_address(rx_buffer->page) + rx_buffer->page_offset;
>
> - if (igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> + if (!skb &&
> + igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> ctx.rx_ts = pktbuf;
> pkt_offset = IGC_TS_HDR_LEN;
> size -= IGC_TS_HDR_LEN;
> --
> 2.55.GIT
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH net] igc: only strip RX timestamp header from first buffer
2026-08-25 23:55 [PATCH net] igc: only strip RX timestamp header from first buffer Paul Moses
2026-08-26 12:51 ` Loktionov, Aleksandr
2026-08-27 15:14 ` Maciej Fijalkowski
@ 2026-09-02 8:44 ` Dahan, AvigailX
2 siblings, 0 replies; 4+ messages in thread
From: Dahan, AvigailX @ 2026-09-02 8:44 UTC (permalink / raw)
To: Paul Moses, intel-wired-lan
Cc: netdev, linux-kernel, anthony.l.nguyen, przemyslaw.kitszel,
andrew+netdev, davem, edumazet, kuba, pabeni, maciej.fijalkowski,
andre.guedes, vedang.patel, jithu.joseph, richardcochran,
tkusters, stable
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On 26/08/2026 2:55, Paul Moses wrote:
> igc_clean_rx_irq() strips IGC_TS_HDR_LEN whenever a descriptor reports
> IGC_RXDADV_STAT_TSIP. For multi-buffer packets, continuation descriptors
> retain TSIP even though the inline timestamp is present only in the first
> RX buffer.
>
> Subtracting the header length from each continuation buffer truncates
> jumbo packets by 16 bytes per continuation and leaves the packet length
> larger than the received data.
>
> Only consume the timestamp header when skb is NULL, which identifies the
> first buffer of a new packet. An skb carried in rx_ring->skb remains
> non-NULL when packet assembly resumes in a later NAPI poll.
>
> Link:https://lore.kernel.org/all/20260625-igb-rx-ts-fix-v3-1-99b3efa08dca@aweta.nl/
> Fixes: e1ed4f92a625 ("igc: Refactor Rx timestamp handling")
> Cc:stable@vger.kernel.org
> Signed-off-by: Paul Moses<p@1g4.org>
> ---
> #
> # REPRO
> #
> # Receiver: igc / enp1s0 / 10.0.5.175
> # Sender: RTL8125B / enP4p65s0 / 10.0.5.165
>
> # Both hosts
> sudo ip link set dev enp1s0 mtu 9000
> sudo ip link set dev enP4p65s0 mtu 9000
>
> # Baseline: RX timestamping off
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> # Enable RX timestamping only
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 1
>
> # Receiver
> sudo timeout 20 tcpdump -ni enp1s0 -s 0 -w /tmp/igc-jumbo.pcap \
> 'icmp and host 10.0.5.165'
>
> # Sender
> ping -n -M do -c 5 -W 2 -s 8972 10.0.5.175
> # 0/5 received
>
> # Receiver
> sudo tcpdump -nn -e -vvv -r /tmp/igc-jumbo.pcap
> # length 8950
> # [total length 9000 > length 8936] (invalid)
> # wrong icmp cksum
>
> # Expected Ethernet length: 9014
> # Captured length: 8950
> # Loss: 64 = 4 continuation buffers * 16 bytes
>
> # Disable RX timestamping again
> sudo hwstamp_ctl -i enp1s0 -t 0 -r 0
> ping -n -M do -c 5 -s 8972 10.0.5.175
> # 5/5 received
>
> ---
>
> drivers/net/ethernet/intel/igc/igc_main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
Tested-by: Avigail Dahan <avigailx.dahan@intel.com>
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