octeontx2-pf: Recalculate UDP checksum for ptp 1-step sync packet

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 <[e-mail]>
Signed-off-by: Hariprasad Kelam <[e-mail]>
Signed-off-by: Sunil Kovvuri Goutham <[e-mail]>
Signed-off-by: Sai Krishna <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c

···
 #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"
···
 
 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;
 
···
 
 	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;
 	}
···
 	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;
···
 		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);
+	if (is_sync)
+		*udp_csum_crt = udp_hdr_present;
+	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);
 	}