[dpdk-dev] [PATCH v3] net/tap: perform proto field update for tun only

[Varghese, Vipin]

HI Keith,

Thanks for pointing out, please find my answer and update below

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> > +			/*
> > +			 * TUN and TAP are created with IFF_NO_PI disabled.
> > +			 * For TUN PMD this mandatory as fields are used by
> > +			 * Kernel tun.c to determine whether its IP or non IP
> > +			 * packets.
> > +			 *
> > +			 * The logic fetches the first byte of data from mbuf
> > +			 * then compares whether its v4 or v6. If first byte
> > +			 * is 4 or 6, then protocol field is updated.
> > +			 */
> > +			char *buff_data = rte_pktmbuf_mtod(seg, void *);
> > +			j = (*buff_data & 0xf0);
> > +			pi.proto = (j == 0x40) ? 0x0008 :
> > 				(j == 0x60) ? 0xdd86 : 0x00;
> 
> Warning Will Robinson: Magic numbers :-)
> 
> Can we use the correct values here ETHERTYPE_IPV6 and ETHERTYPE_IP and
> then use htons() on the values please.

Earlier I refrained from doing this assuming htnos comparison is done for each packet leading to extra cycles. So updated the comments with explanation for logic explanation and readability. 

But I am ok to in co-operate the idea of using MACRO with htnos. I have used ETHER_TYPE_IPv4 and ETHER_TYPE_IPv6 which does not require extra include. The changes are available in v4 version.

> 
> > +		}


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