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 17:16:46 +0100
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Vladimir Oltean <olteanv@...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 Mon, Jan 24, 2022 at 06:05:37PM +0200, Vladimir Oltean wrote:
> 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?
>

Sure will fix in v8.

> > +
> >  #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
> > 
> 

-- 
	Ansuel