Merge branch 'ptp-Add-generic-helper-functions'

Kurt Kanzenbach says:

====================
ptp: Add generic helper functions

in order to reduce code duplication (and cut'n'paste errors) in the ptp code of
DSA, Ethernet and Phy drivers, create helper functions and move them to
ptp_classify. This way all drivers can share the same implementation.

This is version four and contains bugfixes. Implemented as discussed [1] [2]
[3] [4].

Previous versions can be found here:

 * https://lkml.kernel.org/netdev/20200723074946.14253-1-kurt@linutronix.de/
 * https://lkml.kernel.org/netdev/20200727090601.6500-1-kurt@linutronix.de/
 * https://lkml.kernel.org/netdev/20200730080048.32553-1-kurt@linutronix.de/

Thanks,
Kurt

Changes sinve v3:

 * Coding style issues (Richard Cochran, Petr Machata)
 * Add better documentation (Grygorii Strashko)
 * Fix cpts code (Grygorii Strashko)
 * Use ntohs() for TI code (Grygorii Strashko)
 * Add tags

Changes since v2:

 * Make ptp_parse_header() work in all scenarios (Russell King)
 * Fix msgtype offset for ptp v1 packets

Changes since v1:

 * Fix Kconfig (Richard Cochran)
 * Include more drivers (Richard Cochran)

[1] - https://lkml.kernel.org/netdev/20200713140112.GB27934@hoboy/
[2] - https://lkml.kernel.org/netdev/20200720142146.GB16001@hoboy/
[3] - https://lkml.kernel.org/netdev/20200723074946.14253-1-kurt@linutronix.de/
[4] - https://lkml.kernel.org/netdev/20200729100257.GX1551@shell.armlinux.org.uk/
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/hwtstamp.c

@@ -211,49 +211,20 @@ int mv88e6xxx_port_hwtstamp_get(struct dsa_switch *ds, int port,
 		-EFAULT : 0;
 }
 
-/* Get the start of the PTP header in this skb */
-static u8 *parse_ptp_header(struct sk_buff *skb, unsigned int type)
-{
-	u8 *data = skb_mac_header(skb);
-	unsigned int offset = 0;
-
-	if (type & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (type & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return NULL;
-	}
-
-	/* Ensure that the entire header is present in this packet. */
-	if (skb->len + ETH_HLEN < offset + 34)
-		return NULL;
-
-	return data + offset;
-}
-
 /* Returns a pointer to the PTP header if the caller should time stamp,
  * or NULL if the caller should not.
  */
-static u8 *mv88e6xxx_should_tstamp(struct mv88e6xxx_chip *chip, int port,
-				   struct sk_buff *skb, unsigned int type)
+static struct ptp_header *mv88e6xxx_should_tstamp(struct mv88e6xxx_chip *chip,
+						  int port, struct sk_buff *skb,
+						  unsigned int type)
 {
 	struct mv88e6xxx_port_hwtstamp *ps = &chip->port_hwtstamp[port];
-	u8 *hdr;
+	struct ptp_header *hdr;
 
 	if (!chip->info->ptp_support)
 		return NULL;
 
-	hdr = parse_ptp_header(skb, type);
+	hdr = ptp_parse_header(skb, type);
 	if (!hdr)
 		return NULL;
 
@@ -275,12 +246,11 @@ static int mv88e6xxx_ts_valid(u16 status)
 static int seq_match(struct sk_buff *skb, u16 ts_seqid)
 {
 	unsigned int type = SKB_PTP_TYPE(skb);
-	u8 *hdr = parse_ptp_header(skb, type);
-	__be16 *seqid;
+	struct ptp_header *hdr;
 
-	seqid = (__be16 *)(hdr + OFF_PTP_SEQUENCE_ID);
+	hdr = ptp_parse_header(skb, type);
 
-	return ts_seqid == ntohs(*seqid);
+	return ts_seqid == ntohs(hdr->sequence_id);
 }
 
 static void mv88e6xxx_get_rxts(struct mv88e6xxx_chip *chip,
@@ -357,9 +327,9 @@ static void mv88e6xxx_rxtstamp_work(struct mv88e6xxx_chip *chip,
 				   &ps->rx_queue2);
 }
 
-static int is_pdelay_resp(u8 *msgtype)
+static int is_pdelay_resp(const struct ptp_header *hdr)
 {
-	return (*msgtype & 0xf) == 3;
+	return (hdr->tsmt & 0xf) == 3;
 }
 
 bool mv88e6xxx_port_rxtstamp(struct dsa_switch *ds, int port,
@@ -367,7 +337,7 @@ bool mv88e6xxx_port_rxtstamp(struct dsa_switch *ds, int port,
 {
 	struct mv88e6xxx_port_hwtstamp *ps;
 	struct mv88e6xxx_chip *chip;
-	u8 *hdr;
+	struct ptp_header *hdr;
 
 	chip = ds->priv;
 	ps = &chip->port_hwtstamp[port];
@@ -503,8 +473,7 @@ bool mv88e6xxx_port_txtstamp(struct dsa_switch *ds, int port,
 {
 	struct mv88e6xxx_chip *chip = ds->priv;
 	struct mv88e6xxx_port_hwtstamp *ps = &chip->port_hwtstamp[port];
-	__be16 *seq_ptr;
-	u8 *hdr;
+	struct ptp_header *hdr;
 
 	if (!(skb_shinfo(clone)->tx_flags & SKBTX_HW_TSTAMP))
 		return false;
@@ -513,15 +482,13 @@ bool mv88e6xxx_port_txtstamp(struct dsa_switch *ds, int port,
 	if (!hdr)
 		return false;
 
-	seq_ptr = (__be16 *)(hdr + OFF_PTP_SEQUENCE_ID);
-
 	if (test_and_set_bit_lock(MV88E6XXX_HWTSTAMP_TX_IN_PROGRESS,
 				  &ps->state))
 		return false;
 
 	ps->tx_skb = clone;
 	ps->tx_tstamp_start = jiffies;
-	ps->tx_seq_id = be16_to_cpup(seq_ptr);
+	ps->tx_seq_id = be16_to_cpu(hdr->sequence_id);
 
 	ptp_schedule_worker(chip->ptp_clock, 0);
 	return true;

drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c

@@ -314,11 +314,9 @@ static int mlxsw_sp_ptp_parse(struct sk_buff *skb,
 			      u8 *p_message_type,
 			      u16 *p_sequence_id)
 {
-	unsigned int offset = 0;
 	unsigned int ptp_class;
-	u8 *data;
+	struct ptp_header *hdr;
 
-	data = skb_mac_header(skb);
 	ptp_class = ptp_classify_raw(skb);
 
 	switch (ptp_class & PTP_CLASS_VMASK) {
@@ -329,30 +327,14 @@ static int mlxsw_sp_ptp_parse(struct sk_buff *skb,
 		return -ERANGE;
 	}
 
-	if (ptp_class & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (ptp_class & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return -ERANGE;
-	}
-
-	/* PTP header is 34 bytes. */
-	if (skb->len < offset + 34)
+	hdr = ptp_parse_header(skb, ptp_class);
+	if (!hdr)
 		return -EINVAL;
 
-	*p_message_type = data[offset] & 0x0f;
-	*p_domain_number = data[offset + 4];
-	*p_sequence_id = (u16)(data[offset + 30]) << 8 | data[offset + 31];
+	*p_message_type	 = ptp_get_msgtype(hdr, ptp_class);
+	*p_domain_number = hdr->domain_number;
+	*p_sequence_id	 = be16_to_cpu(hdr->sequence_id);
+
 	return 0;
 }
 

drivers/net/ethernet/ti/am65-cpts.c

@@ -748,42 +748,23 @@ EXPORT_SYMBOL_GPL(am65_cpts_rx_enable);
 static int am65_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
 {
 	unsigned int ptp_class = ptp_classify_raw(skb);
-	u8 *msgtype, *data = skb->data;
-	unsigned int offset = 0;
-	__be16 *seqid;
+	struct ptp_header *hdr;
+	u8 msgtype;
+	u16 seqid;
 
 	if (ptp_class == PTP_CLASS_NONE)
 		return 0;
 
-	if (ptp_class & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (ptp_class & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return 0;
-	}
-
-	if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
+	hdr = ptp_parse_header(skb, ptp_class);
+	if (!hdr)
 		return 0;
 
-	if (unlikely(ptp_class & PTP_CLASS_V1))
-		msgtype = data + offset + OFF_PTP_CONTROL;
-	else
-		msgtype = data + offset;
+	msgtype = ptp_get_msgtype(hdr, ptp_class);
+	seqid	= ntohs(hdr->sequence_id);
 
-	seqid = (__be16 *)(data + offset + OFF_PTP_SEQUENCE_ID);
-	*mtype_seqid = (*msgtype << AM65_CPTS_EVENT_1_MESSAGE_TYPE_SHIFT) &
+	*mtype_seqid  = (msgtype << AM65_CPTS_EVENT_1_MESSAGE_TYPE_SHIFT) &
 			AM65_CPTS_EVENT_1_MESSAGE_TYPE_MASK;
-	*mtype_seqid |= (ntohs(*seqid) & AM65_CPTS_EVENT_1_SEQUENCE_ID_MASK);
+	*mtype_seqid |= (seqid & AM65_CPTS_EVENT_1_SEQUENCE_ID_MASK);
 
 	return 1;
 }

drivers/net/ethernet/ti/cpts.c

@@ -446,41 +446,22 @@ static const struct ptp_clock_info cpts_info = {
 static int cpts_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
 {
 	unsigned int ptp_class = ptp_classify_raw(skb);
-	u8 *msgtype, *data = skb->data;
-	unsigned int offset = 0;
-	u16 *seqid;
+	struct ptp_header *hdr;
+	u8 msgtype;
+	u16 seqid;
 
 	if (ptp_class == PTP_CLASS_NONE)
 		return 0;
 
-	if (ptp_class & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (ptp_class & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return 0;
-	}
-
-	if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
+	hdr = ptp_parse_header(skb, ptp_class);
+	if (!hdr)
 		return 0;
 
-	if (unlikely(ptp_class & PTP_CLASS_V1))
-		msgtype = data + offset + OFF_PTP_CONTROL;
-	else
-		msgtype = data + offset;
+	msgtype = ptp_get_msgtype(hdr, ptp_class);
+	seqid	= ntohs(hdr->sequence_id);
 
-	seqid = (u16 *)(data + offset + OFF_PTP_SEQUENCE_ID);
-	*mtype_seqid = (*msgtype & MESSAGE_TYPE_MASK) << MESSAGE_TYPE_SHIFT;
-	*mtype_seqid |= (ntohs(*seqid) & SEQUENCE_ID_MASK) << SEQUENCE_ID_SHIFT;
+	*mtype_seqid  = (msgtype & MESSAGE_TYPE_MASK) << MESSAGE_TYPE_SHIFT;
+	*mtype_seqid |= (seqid & SEQUENCE_ID_MASK) << SEQUENCE_ID_SHIFT;
 
 	return 1;
 }
@@ -528,6 +509,11 @@ void cpts_rx_timestamp(struct cpts *cpts, struct sk_buff *skb)
 	int ret;
 	u64 ns;
 
+	/* cpts_rx_timestamp() is called before eth_type_trans(), so
+	 * skb MAC Hdr properties are not configured yet. Hence need to
+	 * reset skb MAC header here
+	 */
+	skb_reset_mac_header(skb);
 	ret = cpts_skb_get_mtype_seqid(skb, &skb_cb->skb_mtype_seqid);
 	if (!ret)
 		return;

drivers/net/phy/dp83640.c

@@ -798,51 +798,32 @@ static int decode_evnt(struct dp83640_private *dp83640,
 	return parsed;
 }
 
-#define DP83640_PACKET_HASH_OFFSET	20
 #define DP83640_PACKET_HASH_LEN		10
 
 static int match(struct sk_buff *skb, unsigned int type, struct rxts *rxts)
 {
-	unsigned int offset = 0;
-	u8 *msgtype, *data = skb_mac_header(skb);
-	__be16 *seqid;
+	struct ptp_header *hdr;
+	u8 msgtype;
+	u16 seqid;
 	u16 hash;
 
 	/* check sequenceID, messageType, 12 bit hash of offset 20-29 */
 
-	if (type & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (type & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
+	hdr = ptp_parse_header(skb, type);
+	if (!hdr)
 		return 0;
-	}
 
-	if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
-		return 0;
+	msgtype = ptp_get_msgtype(hdr, type);
 
-	if (unlikely(type & PTP_CLASS_V1))
-		msgtype = data + offset + OFF_PTP_CONTROL;
-	else
-		msgtype = data + offset;
-	if (rxts->msgtype != (*msgtype & 0xf))
+	if (rxts->msgtype != (msgtype & 0xf))
 		return 0;
 
-	seqid = (__be16 *)(data + offset + OFF_PTP_SEQUENCE_ID);
-	if (rxts->seqid != ntohs(*seqid))
+	seqid = be16_to_cpu(hdr->sequence_id);
+	if (rxts->seqid != seqid)
 		return 0;
 
 	hash = ether_crc(DP83640_PACKET_HASH_LEN,
-			 data + offset + DP83640_PACKET_HASH_OFFSET) >> 20;
+			 (unsigned char *)&hdr->source_port_identity) >> 20;
 	if (rxts->hash != hash)
 		return 0;
 
@@ -982,35 +963,16 @@ static void decode_status_frame(struct dp83640_private *dp83640,
 
 static int is_sync(struct sk_buff *skb, int type)
 {
-	u8 *data = skb->data, *msgtype;
-	unsigned int offset = 0;
-
-	if (type & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (type & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return 0;
-	}
-
-	if (type & PTP_CLASS_V1)
-		offset += OFF_PTP_CONTROL;
+	struct ptp_header *hdr;
+	u8 msgtype;
 
-	if (skb->len < offset + 1)
+	hdr = ptp_parse_header(skb, type);
+	if (!hdr)
 		return 0;
 
-	msgtype = data + offset;
+	msgtype = ptp_get_msgtype(hdr, type);
 
-	return (*msgtype & 0xf) == 0;
+	return (msgtype & 0xf) == 0;
 }
 
 static void dp83640_free_clocks(void)

drivers/ptp/ptp_ines.c

@@ -93,9 +93,6 @@ MODULE_LICENSE("GPL");
 #define TC_E2E_PTP_V2		2
 #define TC_P2P_PTP_V2		3
 
-#define OFF_PTP_CLOCK_ID	20
-#define OFF_PTP_PORT_NUM	28
-
 #define PHY_SPEED_10		0
 #define PHY_SPEED_100		1
 #define PHY_SPEED_1000		2
@@ -443,57 +440,41 @@ static void ines_link_state(struct mii_timestamper *mii_ts,
 static bool ines_match(struct sk_buff *skb, unsigned int ptp_class,
 		       struct ines_timestamp *ts, struct device *dev)
 {
-	u8 *msgtype, *data = skb_mac_header(skb);
-	unsigned int offset = 0;
-	__be16 *portn, *seqid;
-	__be64 *clkid;
+	struct ptp_header *hdr;
+	u16 portn, seqid;
+	u8 msgtype;
+	u64 clkid;
 
 	if (unlikely(ptp_class & PTP_CLASS_V1))
 		return false;
 
-	if (ptp_class & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
-
-	switch (ptp_class & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return false;
-	}
-
-	if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
+	hdr = ptp_parse_header(skb, ptp_class);
+	if (!hdr)
 		return false;
 
-	msgtype = data + offset;
-	clkid = (__be64 *)(data + offset + OFF_PTP_CLOCK_ID);
-	portn = (__be16 *)(data + offset + OFF_PTP_PORT_NUM);
-	seqid = (__be16 *)(data + offset + OFF_PTP_SEQUENCE_ID);
+	msgtype = ptp_get_msgtype(hdr, ptp_class);
+	clkid = be64_to_cpup((__be64 *)&hdr->source_port_identity.clock_identity.id[0]);
+	portn = be16_to_cpu(hdr->source_port_identity.port_number);
+	seqid = be16_to_cpu(hdr->sequence_id);
 
-	if (tag_to_msgtype(ts->tag & 0x7) != (*msgtype & 0xf)) {
+	if (tag_to_msgtype(ts->tag & 0x7) != msgtype) {
 		dev_dbg(dev, "msgtype mismatch ts %hhu != skb %hhu\n",
-			  tag_to_msgtype(ts->tag & 0x7), *msgtype & 0xf);
+			tag_to_msgtype(ts->tag & 0x7), msgtype);
 		return false;
 	}
-	if (cpu_to_be64(ts->clkid) != *clkid) {
+	if (ts->clkid != clkid) {
 		dev_dbg(dev, "clkid mismatch ts %llx != skb %llx\n",
-			  cpu_to_be64(ts->clkid), *clkid);
+			ts->clkid, clkid);
 		return false;
 	}
-	if (ts->portnum != ntohs(*portn)) {
+	if (ts->portnum != portn) {
 		dev_dbg(dev, "portn mismatch ts %hu != skb %hu\n",
-			  ts->portnum, ntohs(*portn));
+			ts->portnum, portn);
 		return false;
 	}
-	if (ts->seqid != ntohs(*seqid)) {
+	if (ts->seqid != seqid) {
 		dev_dbg(dev, "seqid mismatch ts %hu != skb %hu\n",
-			  ts->seqid, ntohs(*seqid));
+			ts->seqid, seqid);
 		return false;
 	}
 
@@ -694,35 +675,16 @@ static void ines_txtstamp_work(struct work_struct *work)
 
 static bool is_sync_pdelay_resp(struct sk_buff *skb, int type)
 {
-	u8 *data = skb->data, *msgtype;
-	unsigned int offset = 0;
-
-	if (type & PTP_CLASS_VLAN)
-		offset += VLAN_HLEN;
+	struct ptp_header *hdr;
+	u8 msgtype;
 
-	switch (type & PTP_CLASS_PMASK) {
-	case PTP_CLASS_IPV4:
-		offset += ETH_HLEN + IPV4_HLEN(data + offset) + UDP_HLEN;
-		break;
-	case PTP_CLASS_IPV6:
-		offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
-		break;
-	case PTP_CLASS_L2:
-		offset += ETH_HLEN;
-		break;
-	default:
-		return 0;
-	}
-
-	if (type & PTP_CLASS_V1)
-		offset += OFF_PTP_CONTROL;
-
-	if (skb->len < offset + 1)
-		return 0;
+	hdr = ptp_parse_header(skb, type);
+	if (!hdr)
+		return false;
 
-	msgtype = data + offset;
+	msgtype = ptp_get_msgtype(hdr, type);
 
-	switch ((*msgtype & 0xf)) {
+	switch ((msgtype & 0xf)) {
 	case SYNC:
 	case PDELAY_RESP:
 		return true;

include/linux/ptp_classify.h

@@ -36,7 +36,6 @@
 
 #define OFF_PTP_SOURCE_UUID	22 /* PTPv1 only */
 #define OFF_PTP_SEQUENCE_ID	30
-#define OFF_PTP_CONTROL		32 /* PTPv1 only */
 
 /* Below defines should actually be removed at some point in time. */
 #define IP6_HLEN	40
@@ -44,6 +43,30 @@
 #define OFF_IHL		14
 #define IPV4_HLEN(data) (((struct iphdr *)(data + OFF_IHL))->ihl << 2)
 
+struct clock_identity {
+	u8 id[8];
+} __packed;
+
+struct port_identity {
+	struct clock_identity	clock_identity;
+	__be16			port_number;
+} __packed;
+
+struct ptp_header {
+	u8			tsmt;  /* transportSpecific | messageType */
+	u8			ver;   /* reserved          | versionPTP  */
+	__be16			message_length;
+	u8			domain_number;
+	u8			reserved1;
+	u8			flag_field[2];
+	__be64			correction;
+	__be32			reserved2;
+	struct port_identity	source_port_identity;
+	__be16			sequence_id;
+	u8			control;
+	u8			log_message_interval;
+} __packed;
+
 #if defined(CONFIG_NET_PTP_CLASSIFY)
 /**
  * ptp_classify_raw - classify a PTP packet
@@ -57,6 +80,46 @@
  */
 unsigned int ptp_classify_raw(const struct sk_buff *skb);
 
+/**
+ * ptp_parse_header - Get pointer to the PTP v2 header
+ * @skb: packet buffer
+ * @type: type of the packet (see ptp_classify_raw())
+ *
+ * This function takes care of the VLAN, UDP, IPv4 and IPv6 headers. The length
+ * is checked.
+ *
+ * Note, internally skb_mac_header() is used. Make sure that the @skb is
+ * initialized accordingly.
+ *
+ * Return: Pointer to the ptp v2 header or NULL if not found
+ */
+struct ptp_header *ptp_parse_header(struct sk_buff *skb, unsigned int type);
+
+/**
+ * ptp_get_msgtype - Extract ptp message type from given header
+ * @hdr: ptp header
+ * @type: type of the packet (see ptp_classify_raw())
+ *
+ * This function returns the message type for a given ptp header. It takes care
+ * of the different ptp header versions (v1 or v2).
+ *
+ * Return: The message type
+ */
+static inline u8 ptp_get_msgtype(const struct ptp_header *hdr,
+				 unsigned int type)
+{
+	u8 msgtype;
+
+	if (unlikely(type & PTP_CLASS_V1)) {
+		/* msg type is located at the control field for ptp v1 */
+		msgtype = hdr->control;
+	} else {
+		msgtype = hdr->tsmt & 0x0f;
+	}
+
+	return msgtype;
+}
+
 void __init ptp_classifier_init(void);
 #else
 static inline void ptp_classifier_init(void)
@@ -66,5 +129,10 @@ static inline unsigned int ptp_classify_raw(struct sk_buff *skb)
 {
 	return PTP_CLASS_NONE;
 }
+static inline struct ptp_header *ptp_parse_header(struct sk_buff *skb,
+						  unsigned int type)
+{
+	return NULL;
+}
 #endif
 #endif /* _PTP_CLASSIFY_H_ */

net/core/ptp_classifier.c

@@ -107,6 +107,36 @@ unsigned int ptp_classify_raw(const struct sk_buff *skb)
 }
 EXPORT_SYMBOL_GPL(ptp_classify_raw);
 
+struct ptp_header *ptp_parse_header(struct sk_buff *skb, unsigned int type)
+{
+	u8 *ptr = skb_mac_header(skb);
+
+	if (type & PTP_CLASS_VLAN)
+		ptr += VLAN_HLEN;
+
+	switch (type & PTP_CLASS_PMASK) {
+	case PTP_CLASS_IPV4:
+		ptr += IPV4_HLEN(ptr) + UDP_HLEN;
+		break;
+	case PTP_CLASS_IPV6:
+		ptr += IP6_HLEN + UDP_HLEN;
+		break;
+	case PTP_CLASS_L2:
+		break;
+	default:
+		return NULL;
+	}
+
+	ptr += ETH_HLEN;
+
+	/* Ensure that the entire header is present in this packet. */
+	if (ptr + sizeof(struct ptp_header) > skb->data + skb->len)
+		return NULL;
+
+	return (struct ptp_header *)ptr;
+}
+EXPORT_SYMBOL_GPL(ptp_parse_header);
+
 void __init ptp_classifier_init(void)
 {
 	static struct sock_filter ptp_filter[] __initdata = {