[net PATCH] octeontx2-pf: Recalculate UDP checksum for ptp 1-step sync packet

[net PATCH] octeontx2-pf: Recalculate UDP checksum for ptp 1-step sync packet

[Sai Krishna]

From: Geetha sowjanya <gakula@marvell.com>

When checksum offload is disabled in the driver via ethtool,
the PTP 1-step sync packets contain incorrect checksum, since
the stack calculates the checksum before driver updates
PTP timestamp field in the packet. This results in PTP packets
getting dropped at the other end. This patch fixes the issue by
re-calculating the UDP checksum after updating PTP
timestamp field in the driver.

Fixes: 2958d17a8984 ("octeontx2-pf: Add support for ptp 1-step mode on CN10K silicon")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
---
 .../marvell/octeontx2/nic/otx2_txrx.c         | 78 ++++++++++++++-----
 1 file changed, 59 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
index ef10aef3cda0..67345a3e2bba 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
@@ -10,6 +10,7 @@
 #include <net/tso.h>
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
+#include <net/ip6_checksum.h>
 
 #include "otx2_reg.h"
 #include "otx2_common.h"
@@ -699,7 +700,7 @@ static void otx2_sqe_add_ext(struct otx2_nic *pfvf, struct otx2_snd_queue *sq,
 
 static void otx2_sqe_add_mem(struct otx2_snd_queue *sq, int *offset,
 			     int alg, u64 iova, int ptp_offset,
-			     u64 base_ns, int udp_csum)
+			     u64 base_ns, bool udp_csum_crt)
 {
 	struct nix_sqe_mem_s *mem;
 
@@ -711,7 +712,7 @@ static void otx2_sqe_add_mem(struct otx2_snd_queue *sq, int *offset,
 
 	if (ptp_offset) {
 		mem->start_offset = ptp_offset;
-		mem->udp_csum_crt = udp_csum;
+		mem->udp_csum_crt = !!udp_csum_crt;
 		mem->base_ns = base_ns;
 		mem->step_type = 1;
 	}
@@ -986,10 +987,11 @@ static bool otx2_validate_network_transport(struct sk_buff *skb)
 	return false;
 }
 
-static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, int *udp_csum)
+static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, bool *udp_csum_crt)
 {
 	struct ethhdr *eth = (struct ethhdr *)(skb->data);
 	u16 nix_offload_hlen = 0, inner_vhlen = 0;
+	bool udp_hdr_present = false, is_sync;
 	u8 *data = skb->data, *msgtype;
 	__be16 proto = eth->h_proto;
 	int network_depth = 0;
@@ -1029,45 +1031,83 @@ static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, int *udp_csum)
 		if (!otx2_validate_network_transport(skb))
 			return false;
 
-		*udp_csum = 1;
 		*offset = nix_offload_hlen + skb_transport_offset(skb) +
 			  sizeof(struct udphdr);
+		udp_hdr_present = true;
+
 	}
 
 	msgtype = data + *offset;
-
 	/* Check PTP messageId is SYNC or not */
-	return (*msgtype & 0xf) == 0;
+	is_sync =  ((*msgtype & 0xf) == 0) ? true : false;
+	if (is_sync) {
+		if (udp_hdr_present)
+			*udp_csum_crt = true;
+	} else {
+		*offset = 0;
+	}
+
+	return is_sync;
 }
 
 static void otx2_set_txtstamp(struct otx2_nic *pfvf, struct sk_buff *skb,
 			      struct otx2_snd_queue *sq, int *offset)
 {
+	struct ethhdr	*eth = (struct ethhdr *)(skb->data);
 	struct ptpv2_tstamp *origin_tstamp;
-	int ptp_offset = 0, udp_csum = 0;
+	bool udp_csum_crt = false;
+	unsigned int udphoff;
 	struct timespec64 ts;
+	int ptp_offset = 0;
+	__wsum skb_csum;
 	u64 iova;
 
 	if (unlikely(!skb_shinfo(skb)->gso_size &&
 		     (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))) {
-		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC)) {
-			if (otx2_ptp_is_sync(skb, &ptp_offset, &udp_csum)) {
-				origin_tstamp = (struct ptpv2_tstamp *)
-						((u8 *)skb->data + ptp_offset +
-						 PTP_SYNC_SEC_OFFSET);
-				ts = ns_to_timespec64(pfvf->ptp->tstamp);
-				origin_tstamp->seconds_msb = htons((ts.tv_sec >> 32) & 0xffff);
-				origin_tstamp->seconds_lsb = htonl(ts.tv_sec & 0xffffffff);
-				origin_tstamp->nanoseconds = htonl(ts.tv_nsec);
-				/* Point to correction field in PTP packet */
-				ptp_offset += 8;
+		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC &&
+			     otx2_ptp_is_sync(skb, &ptp_offset, &udp_csum_crt))) {
+			origin_tstamp = (struct ptpv2_tstamp *)
+					((u8 *)skb->data + ptp_offset +
+					 PTP_SYNC_SEC_OFFSET);
+			ts = ns_to_timespec64(pfvf->ptp->tstamp);
+			origin_tstamp->seconds_msb = htons((ts.tv_sec >> 32) & 0xffff);
+			origin_tstamp->seconds_lsb = htonl(ts.tv_sec & 0xffffffff);
+			origin_tstamp->nanoseconds = htonl(ts.tv_nsec);
+			/* Point to correction field in PTP packet */
+			ptp_offset += 8;
+
+			/* When user disables hw checksum, stack calculates the csum,
+			 * but it does not cover ptp timestamp which is added later.
+			 * Recalculate the checksum manually considering the timestamp.
+			 */
+			if (udp_csum_crt) {
+				struct udphdr *uh = udp_hdr(skb);
+
+				if (skb->ip_summed != CHECKSUM_PARTIAL && uh->check != 0) {
+					udphoff = skb_transport_offset(skb);
+					uh->check = 0;
+					skb_csum = skb_checksum(skb, udphoff, skb->len - udphoff,
+								0);
+					if (ntohs(eth->h_proto) == ETH_P_IPV6)
+						uh->check = csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+									    &ipv6_hdr(skb)->daddr,
+									    skb->len - udphoff,
+									    ipv6_hdr(skb)->nexthdr,
+									    skb_csum);
+					else
+						uh->check = csum_tcpudp_magic(ip_hdr(skb)->saddr,
+									      ip_hdr(skb)->daddr,
+									      skb->len - udphoff,
+									      IPPROTO_UDP,
+									      skb_csum);
+				}
 			}
 		} else {
 			skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 		}
 		iova = sq->timestamps->iova + (sq->head * sizeof(u64));
 		otx2_sqe_add_mem(sq, offset, NIX_SENDMEMALG_E_SETTSTMP, iova,
-				 ptp_offset, pfvf->ptp->base_ns, udp_csum);
+				 ptp_offset, pfvf->ptp->base_ns, udp_csum_crt);
 	} else {
 		skb_tx_timestamp(skb);
 	}
-- 
2.25.1

Re: [net PATCH] octeontx2-pf: Recalculate UDP checksum for ptp 1-step sync packet

[Paolo Abeni]

On Mon, 2023-02-20 at 17:50 +0530, Sai Krishna wrote:
> From: Geetha sowjanya <gakula@marvell.com>
> 
> When checksum offload is disabled in the driver via ethtool,
> the PTP 1-step sync packets contain incorrect checksum, since
> the stack calculates the checksum before driver updates
> PTP timestamp field in the packet. This results in PTP packets
> getting dropped at the other end. This patch fixes the issue by
> re-calculating the UDP checksum after updating PTP
> timestamp field in the driver.
> 
> Fixes: 2958d17a8984 ("octeontx2-pf: Add support for ptp 1-step mode on CN10K silicon")
> Signed-off-by: Geetha sowjanya <gakula@marvell.com>
> Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
> Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
> Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
> ---
>  .../marvell/octeontx2/nic/otx2_txrx.c         | 78 ++++++++++++++-----
>  1 file changed, 59 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> index ef10aef3cda0..67345a3e2bba 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> @@ -10,6 +10,7 @@
>  #include <net/tso.h>
>  #include <linux/bpf.h>
>  #include <linux/bpf_trace.h>
> +#include <net/ip6_checksum.h>
>  
>  #include "otx2_reg.h"
>  #include "otx2_common.h"
> @@ -699,7 +700,7 @@ static void otx2_sqe_add_ext(struct otx2_nic *pfvf, struct otx2_snd_queue *sq,
>  
>  static void otx2_sqe_add_mem(struct otx2_snd_queue *sq, int *offset,
>  			     int alg, u64 iova, int ptp_offset,
> -			     u64 base_ns, int udp_csum)
> +			     u64 base_ns, bool udp_csum_crt)
>  {
>  	struct nix_sqe_mem_s *mem;
>  
> @@ -711,7 +712,7 @@ static void otx2_sqe_add_mem(struct otx2_snd_queue *sq, int *offset,
>  
>  	if (ptp_offset) {
>  		mem->start_offset = ptp_offset;
> -		mem->udp_csum_crt = udp_csum;
> +		mem->udp_csum_crt = !!udp_csum_crt;
>  		mem->base_ns = base_ns;
>  		mem->step_type = 1;
>  	}
> @@ -986,10 +987,11 @@ static bool otx2_validate_network_transport(struct sk_buff *skb)
>  	return false;
>  }
>  
> -static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, int *udp_csum)
> +static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, bool *udp_csum_crt)
>  {
>  	struct ethhdr *eth = (struct ethhdr *)(skb->data);
>  	u16 nix_offload_hlen = 0, inner_vhlen = 0;
> +	bool udp_hdr_present = false, is_sync;
>  	u8 *data = skb->data, *msgtype;
>  	__be16 proto = eth->h_proto;
>  	int network_depth = 0;
> @@ -1029,45 +1031,83 @@ static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, int *udp_csum)
>  		if (!otx2_validate_network_transport(skb))
>  			return false;
>  
> -		*udp_csum = 1;
>  		*offset = nix_offload_hlen + skb_transport_offset(skb) +
>  			  sizeof(struct udphdr);
> +		udp_hdr_present = true;
> +
>  	}
>  
>  	msgtype = data + *offset;
> -
>  	/* Check PTP messageId is SYNC or not */
> -	return (*msgtype & 0xf) == 0;
> +	is_sync =  ((*msgtype & 0xf) == 0) ? true : false;

the above could be:

	is_sync = !(*msgtype & 0xf);

possibly more readable.

> +	if (is_sync) {
> +		if (udp_hdr_present)
> +			*udp_csum_crt = true;

or:
		*udp_csum_crt = udp_hdr_present;

that will make the code more compact.

> +	} else {
> +		*offset = 0;
> +	}
> +
> +	return is_sync;
>  }
>  
>  static void otx2_set_txtstamp(struct otx2_nic *pfvf, struct sk_buff *skb,
>  			      struct otx2_snd_queue *sq, int *offset)
>  {
> +	struct ethhdr	*eth = (struct ethhdr *)(skb->data);
>  	struct ptpv2_tstamp *origin_tstamp;
> -	int ptp_offset = 0, udp_csum = 0;
> +	bool udp_csum_crt = false;
> +	unsigned int udphoff;
>  	struct timespec64 ts;
> +	int ptp_offset = 0;
> +	__wsum skb_csum;
>  	u64 iova;
>  
>  	if (unlikely(!skb_shinfo(skb)->gso_size &&
>  		     (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))) {
> -		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC)) {
> -			if (otx2_ptp_is_sync(skb, &ptp_offset, &udp_csum)) {
> -				origin_tstamp = (struct ptpv2_tstamp *)
> -						((u8 *)skb->data + ptp_offset +
> -						 PTP_SYNC_SEC_OFFSET);
> -				ts = ns_to_timespec64(pfvf->ptp->tstamp);
> -				origin_tstamp->seconds_msb = htons((ts.tv_sec >> 32) & 0xffff);
> -				origin_tstamp->seconds_lsb = htonl(ts.tv_sec & 0xffffffff);
> -				origin_tstamp->nanoseconds = htonl(ts.tv_nsec);
> -				/* Point to correction field in PTP packet */
> -				ptp_offset += 8;
> +		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC &&
> +			     otx2_ptp_is_sync(skb, &ptp_offset, &udp_csum_crt))) {
> +			origin_tstamp = (struct ptpv2_tstamp *)
> +					((u8 *)skb->data + ptp_offset +
> +					 PTP_SYNC_SEC_OFFSET);
> +			ts = ns_to_timespec64(pfvf->ptp->tstamp);
> +			origin_tstamp->seconds_msb = htons((ts.tv_sec >> 32) & 0xffff);
> +			origin_tstamp->seconds_lsb = htonl(ts.tv_sec & 0xffffffff);
> +			origin_tstamp->nanoseconds = htonl(ts.tv_nsec);
> +			/* Point to correction field in PTP packet */
> +			ptp_offset += 8;
> +
> +			/* When user disables hw checksum, stack calculates the csum,
> +			 * but it does not cover ptp timestamp which is added later.
> +			 * Recalculate the checksum manually considering the timestamp.
> +			 */
> +			if (udp_csum_crt) {
> +				struct udphdr *uh = udp_hdr(skb);
> +
> +				if (skb->ip_summed != CHECKSUM_PARTIAL && uh->check != 0) {
> +					udphoff = skb_transport_offset(skb);
> +					uh->check = 0;
> +					skb_csum = skb_checksum(skb, udphoff, skb->len - udphoff,
> +								0);
> +					if (ntohs(eth->h_proto) == ETH_P_IPV6)
> +						uh->check = csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +									    &ipv6_hdr(skb)->daddr,
> +									    skb->len - udphoff,
> +									    ipv6_hdr(skb)->nexthdr,
> +									    skb_csum);
> +					else
> +						uh->check = csum_tcpudp_magic(ip_hdr(skb)->saddr,
> +									      ip_hdr(skb)->daddr,
> +									      skb->len - udphoff,
> +									      IPPROTO_UDP,
> +									      skb_csum);

Have you considered incremental csum updates instead? Possibly the code
could be simpler and likely faster - not sure if the latter part is
relevant in this case.

Cheers,

Paolo

Re: [net PATCH] octeontx2-pf: Recalculate UDP checksum for ptp 1-step sync packet

[Sai Krishna Gajula]

Hi Paolo,

Please see the responses inline.

> -----Original Message-----
> From: Paolo Abeni <pabeni@redhat.com>
> Sent: Tuesday, February 21, 2023 5:10 PM
> To: Sai Krishna Gajula <saikrishnag@marvell.com>; davem@davemloft.net;
> edumazet@google.com; kuba@kernel.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; Sunil Kovvuri Goutham <sgoutham@marvell.com>;
> Geethasowjanya Akula <gakula@marvell.com>; richardcochran@gmail.com
> Cc: Hariprasad Kelam <hkelam@marvell.com>
> Subject: Re: [net PATCH] octeontx2-pf: Recalculate UDP checksum for
> ptp 1-step sync packet
> 
> On Mon, 2023-02-20 at 17:50 +0530, Sai Krishna wrote:
> > From: Geetha sowjanya <gakula@marvell.com>
> >
> > When checksum offload is disabled in the driver via ethtool, the PTP
> > 1-step sync packets contain incorrect checksum, since the stack
> > calculates the checksum before driver updates PTP timestamp field in
> > the packet. This results in PTP packets getting dropped at the other
> > end. This patch fixes the issue by re-calculating the UDP checksum
> > after updating PTP timestamp field in the driver.
> >
> > Fixes: 2958d17a8984 ("octeontx2-pf: Add support for ptp 1-step mode on
> > CN10K silicon")
> > Signed-off-by: Geetha sowjanya <gakula@marvell.com>
> > Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
> > Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
> > Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
> > ---
> >  .../marvell/octeontx2/nic/otx2_txrx.c         | 78 ++++++++++++++-----
> >  1 file changed, 59 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > index ef10aef3cda0..67345a3e2bba 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > @@ -10,6 +10,7 @@
> >  #include <net/tso.h>
> >  #include <linux/bpf.h>
> >  #include <linux/bpf_trace.h>
> > +#include <net/ip6_checksum.h>
> >
> >  #include "otx2_reg.h"
> >  #include "otx2_common.h"
> > @@ -699,7 +700,7 @@ static void otx2_sqe_add_ext(struct otx2_nic
> > *pfvf, struct otx2_snd_queue *sq,
> >
> >  static void otx2_sqe_add_mem(struct otx2_snd_queue *sq, int *offset,
> >  			     int alg, u64 iova, int ptp_offset,
> > -			     u64 base_ns, int udp_csum)
> > +			     u64 base_ns, bool udp_csum_crt)
> >  {
> >  	struct nix_sqe_mem_s *mem;
> >
> > @@ -711,7 +712,7 @@ static void otx2_sqe_add_mem(struct
> otx2_snd_queue
> > *sq, int *offset,
> >
> >  	if (ptp_offset) {
> >  		mem->start_offset = ptp_offset;
> > -		mem->udp_csum_crt = udp_csum;
> > +		mem->udp_csum_crt = !!udp_csum_crt;
> >  		mem->base_ns = base_ns;
> >  		mem->step_type = 1;
> >  	}
> > @@ -986,10 +987,11 @@ static bool
> otx2_validate_network_transport(struct sk_buff *skb)
> >  	return false;
> >  }
> >
> > -static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, int
> > *udp_csum)
> > +static bool otx2_ptp_is_sync(struct sk_buff *skb, int *offset, bool
> > +*udp_csum_crt)
> >  {
> >  	struct ethhdr *eth = (struct ethhdr *)(skb->data);
> >  	u16 nix_offload_hlen = 0, inner_vhlen = 0;
> > +	bool udp_hdr_present = false, is_sync;
> >  	u8 *data = skb->data, *msgtype;
> >  	__be16 proto = eth->h_proto;
> >  	int network_depth = 0;
> > @@ -1029,45 +1031,83 @@ static bool otx2_ptp_is_sync(struct sk_buff
> *skb, int *offset, int *udp_csum)
> >  		if (!otx2_validate_network_transport(skb))
> >  			return false;
> >
> > -		*udp_csum = 1;
> >  		*offset = nix_offload_hlen + skb_transport_offset(skb) +
> >  			  sizeof(struct udphdr);
> > +		udp_hdr_present = true;
> > +
> >  	}
> >
> >  	msgtype = data + *offset;
> > -
> >  	/* Check PTP messageId is SYNC or not */
> > -	return (*msgtype & 0xf) == 0;
> > +	is_sync =  ((*msgtype & 0xf) == 0) ? true : false;
> 
> the above could be:
> 
> 	is_sync = !(*msgtype & 0xf);
> 

I will make changes and submit v2 patch.

> possibly more readable.
> 
> > +	if (is_sync) {
> > +		if (udp_hdr_present)
> > +			*udp_csum_crt = true;
> 
> or:
> 		*udp_csum_crt = udp_hdr_present;
> 
> that will make the code more compact.
> 

I will make changes and submit v2 patch.

> > +	} else {
> > +		*offset = 0;
> > +	}
> > +
> > +	return is_sync;
> >  }
> >
> >  static void otx2_set_txtstamp(struct otx2_nic *pfvf, struct sk_buff *skb,
> >  			      struct otx2_snd_queue *sq, int *offset)  {
> > +	struct ethhdr	*eth = (struct ethhdr *)(skb->data);
> >  	struct ptpv2_tstamp *origin_tstamp;
> > -	int ptp_offset = 0, udp_csum = 0;
> > +	bool udp_csum_crt = false;
> > +	unsigned int udphoff;
> >  	struct timespec64 ts;
> > +	int ptp_offset = 0;
> > +	__wsum skb_csum;
> >  	u64 iova;
> >
> >  	if (unlikely(!skb_shinfo(skb)->gso_size &&
> >  		     (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))) {
> > -		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC)) {
> > -			if (otx2_ptp_is_sync(skb, &ptp_offset, &udp_csum)) {
> > -				origin_tstamp = (struct ptpv2_tstamp *)
> > -						((u8 *)skb->data + ptp_offset
> +
> > -						 PTP_SYNC_SEC_OFFSET);
> > -				ts = ns_to_timespec64(pfvf->ptp->tstamp);
> > -				origin_tstamp->seconds_msb =
> htons((ts.tv_sec >> 32) & 0xffff);
> > -				origin_tstamp->seconds_lsb = htonl(ts.tv_sec
> & 0xffffffff);
> > -				origin_tstamp->nanoseconds =
> htonl(ts.tv_nsec);
> > -				/* Point to correction field in PTP packet */
> > -				ptp_offset += 8;
> > +		if (unlikely(pfvf->flags & OTX2_FLAG_PTP_ONESTEP_SYNC &&
> > +			     otx2_ptp_is_sync(skb, &ptp_offset,
> &udp_csum_crt))) {
> > +			origin_tstamp = (struct ptpv2_tstamp *)
> > +					((u8 *)skb->data + ptp_offset +
> > +					 PTP_SYNC_SEC_OFFSET);
> > +			ts = ns_to_timespec64(pfvf->ptp->tstamp);
> > +			origin_tstamp->seconds_msb = htons((ts.tv_sec >>
> 32) & 0xffff);
> > +			origin_tstamp->seconds_lsb = htonl(ts.tv_sec &
> 0xffffffff);
> > +			origin_tstamp->nanoseconds = htonl(ts.tv_nsec);
> > +			/* Point to correction field in PTP packet */
> > +			ptp_offset += 8;
> > +
> > +			/* When user disables hw checksum, stack calculates
> the csum,
> > +			 * but it does not cover ptp timestamp which is added
> later.
> > +			 * Recalculate the checksum manually considering the
> timestamp.
> > +			 */
> > +			if (udp_csum_crt) {
> > +				struct udphdr *uh = udp_hdr(skb);
> > +
> > +				if (skb->ip_summed != CHECKSUM_PARTIAL
> && uh->check != 0) {
> > +					udphoff = skb_transport_offset(skb);
> > +					uh->check = 0;
> > +					skb_csum = skb_checksum(skb,
> udphoff, skb->len - udphoff,
> > +								0);
> > +					if (ntohs(eth->h_proto) ==
> ETH_P_IPV6)
> > +						uh->check =
> csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> > +
> &ipv6_hdr(skb)->daddr,
> > +
> skb->len - udphoff,
> > +
> ipv6_hdr(skb)->nexthdr,
> > +
> skb_csum);
> > +					else
> > +						uh->check =
> csum_tcpudp_magic(ip_hdr(skb)->saddr,
> > +
> ip_hdr(skb)->daddr,
> > +
> skb->len - udphoff,
> > +
> IPPROTO_UDP,
> > +
> skb_csum);
> 
> Have you considered incremental csum updates instead? Possibly the code
> could be simpler and likely faster - not sure if the latter part is relevant in this
> case.
>

We don't expect any significant performance improvement with this for PTP sync packets.
So we didn't consider incremental csum updates.

Thanks,
Sai 

> Cheers,
> 
> Paolo