linux-kernel - Re: [RFC PATCH v7 06/16] net: dsa: tag_qca: add define for handling mgmt Ethernet packet

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Date:   Mon, 24 Jan 2022 18:05:37 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [RFC PATCH v7 06/16] net: dsa: tag_qca: add define for handling
 mgmt Ethernet packet

On Sun, Jan 23, 2022 at 02:33:27AM +0100, Ansuel Smith wrote:
> Add all the required define to prepare support for mgmt read/write in
> Ethernet packet. Any packet of this type has to be dropped as the only
> use of these special packet is receive ack for an mgmt write request or
> receive data for an mgmt read request.
> A struct is used that emulates the Ethernet header but is used for a
> different purpose.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>  include/linux/dsa/tag_qca.h | 44 +++++++++++++++++++++++++++++++++++++
>  net/dsa/tag_qca.c           | 13 ++++++++---
>  2 files changed, 54 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/dsa/tag_qca.h b/include/linux/dsa/tag_qca.h
> index c02d2d39ff4a..1a02f695f3a3 100644
> --- a/include/linux/dsa/tag_qca.h
> +++ b/include/linux/dsa/tag_qca.h
> @@ -12,10 +12,54 @@
>  #define QCA_HDR_RECV_FRAME_IS_TAGGED	BIT(3)
>  #define QCA_HDR_RECV_SOURCE_PORT	GENMASK(2, 0)
>  
> +/* Packet type for recv */
> +#define QCA_HDR_RECV_TYPE_NORMAL	0x0
> +#define QCA_HDR_RECV_TYPE_MIB		0x1
> +#define QCA_HDR_RECV_TYPE_RW_REG_ACK	0x2
> +
>  #define QCA_HDR_XMIT_VERSION		GENMASK(15, 14)
>  #define QCA_HDR_XMIT_PRIORITY		GENMASK(13, 11)
>  #define QCA_HDR_XMIT_CONTROL		GENMASK(10, 8)
>  #define QCA_HDR_XMIT_FROM_CPU		BIT(7)
>  #define QCA_HDR_XMIT_DP_BIT		GENMASK(6, 0)
>  
> +/* Packet type for xmit */
> +#define QCA_HDR_XMIT_TYPE_NORMAL	0x0
> +#define QCA_HDR_XMIT_TYPE_RW_REG	0x1
> +
> +/* Check code for a valid mgmt packet. Switch will ignore the packet
> + * with this wrong.
> + */
> +#define QCA_HDR_MGMT_CHECK_CODE_VAL	0x5
> +
> +/* Specific define for in-band MDIO read/write with Ethernet packet */
> +#define QCA_HDR_MGMT_SEQ_LEN		4 /* 4 byte for the seq */
> +#define QCA_HDR_MGMT_COMMAND_LEN	4 /* 4 byte for the command */
> +#define QCA_HDR_MGMT_DATA1_LEN		4 /* First 4 byte for the mdio data */
> +#define QCA_HDR_MGMT_HEADER_LEN		(QCA_HDR_MGMT_SEQ_LEN + \
> +					QCA_HDR_MGMT_COMMAND_LEN + \
> +					QCA_HDR_MGMT_DATA1_LEN)
> +
> +#define QCA_HDR_MGMT_DATA2_LEN		12 /* Other 12 byte for the mdio data */
> +#define QCA_HDR_MGMT_PADDING_LEN	34 /* Padding to reach the min Ethernet packet */
> +
> +#define QCA_HDR_MGMT_PKG_LEN		(QCA_HDR_MGMT_HEADER_LEN + \
> +					QCA_HDR_LEN + \
> +					QCA_HDR_MGMT_DATA2_LEN + \
> +					QCA_HDR_MGMT_PADDING_LEN)

s/PKG/PKT/

> +
> +#define QCA_HDR_MGMT_SEQ_NUM		GENMASK(31, 0)  /* 63, 32 */
> +#define QCA_HDR_MGMT_CHECK_CODE		GENMASK(31, 29) /* 31, 29 */
> +#define QCA_HDR_MGMT_CMD		BIT(28)		/* 28 */
> +#define QCA_HDR_MGMT_LENGTH		GENMASK(23, 20) /* 23, 20 */
> +#define QCA_HDR_MGMT_ADDR		GENMASK(18, 0)  /* 18, 0 */
> +
> +/* Special struct emulating a Ethernet header */
> +struct mgmt_ethhdr {
> +	u32 command;		/* command bit 31:0 */
> +	u32 seq;		/* seq 63:32 */
> +	u32 mdio_data;		/* first 4byte mdio */
> +	__be16 hdr;		/* qca hdr */
> +} __packed;

Could you name this something a bit more specific, like qca_mgmt_ethhdr?

> +
>  #endif /* __TAG_QCA_H */
> diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c
> index f8df49d5956f..c57d6e1a0c0c 100644
> --- a/net/dsa/tag_qca.c
> +++ b/net/dsa/tag_qca.c
> @@ -32,10 +32,10 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
>  
>  static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
>  {
> -	u8 ver;
> -	u16  hdr;
> -	int port;
> +	u16 hdr, pk_type;
>  	__be16 *phdr;
> +	int port;
> +	u8 ver;
>  
>  	if (unlikely(!pskb_may_pull(skb, QCA_HDR_LEN)))
>  		return NULL;
> @@ -48,6 +48,13 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
>  	if (unlikely(ver != QCA_HDR_VERSION))
>  		return NULL;
>  
> +	/* Get pk type */
> +	pk_type = FIELD_GET(QCA_HDR_RECV_TYPE, hdr);
> +
> +	/* Ethernet MDIO read/write packet */
> +	if (pk_type == QCA_HDR_RECV_TYPE_RW_REG_ACK)
> +		return NULL;
> +
>  	/* Remove QCA tag and recalculate checksum */
>  	skb_pull_rcsum(skb, QCA_HDR_LEN);
>  	dsa_strip_etype_header(skb, QCA_HDR_LEN);
> -- 
> 2.33.1
>