netdev - RE: [PATCH net-next v18 06/13] rtase: Implement .ndo_start

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Message-ID: <7f1ff93c4f7d4fc9bdefbb646c18acc1@realtek.com>
Date: Mon, 13 May 2024 03:43:52 +0000
From: Justin Lai <justinlai0215@...ltek.com>
To: Andrew Lunn <andrew@...n.ch>
CC: "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net"
	<davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "horms@...nel.org" <horms@...nel.org>,
        Ping-Ke Shih <pkshih@...ltek.com>, Larry Chiu <larry.chiu@...ltek.com>
Subject: RE: [PATCH net-next v18 06/13] rtase: Implement .ndo_start_xmit function

> 
> > +static u32 rtase_tx_csum(struct sk_buff *skb, const struct net_device
> > +*dev) {
> > +     u32 csum_cmd = 0;
> > +     u8 ip_protocol;
> > +
> > +     switch (vlan_get_protocol(skb)) {
> > +     case htons(ETH_P_IP):
> > +             csum_cmd = RTASE_TX_IPCS_C;
> > +             ip_protocol = ip_hdr(skb)->protocol;
> > +             break;
> > +
> > +     case htons(ETH_P_IPV6):
> > +             csum_cmd = RTASE_TX_IPV6F_C;
> > +             ip_protocol = ipv6_hdr(skb)->nexthdr;
> > +             break;
> > +
> > +     default:
> > +             ip_protocol = IPPROTO_RAW;
> > +             break;
> > +     }
> > +
> > +     if (ip_protocol == IPPROTO_TCP)
> > +             csum_cmd |= RTASE_TX_TCPCS_C;
> > +     else if (ip_protocol == IPPROTO_UDP)
> > +             csum_cmd |= RTASE_TX_UDPCS_C;
> > +     else
> > +             WARN_ON_ONCE(1);
> 
> I'm not so sure about this WARN_ON_ONCE(). It looks like if i send a custom
> packet which is not IPv4 or IPv6 it will fire. There are other protocols then IP.
> Connecting to an Ethernet switch using DSA tags would be a good example. So
> i don't think you want this warning.
> 
>       Andrew

Hi Andrew,
The condition for entering this function is checksum_partial, which requires
hardware to help calculate the checksum, so protocols that are not supported
by the hardware will issue warn_on_once.