Re: [dpdk-dev] [PATCH v10 3/5] net: add a helper for making RARP packet

[Olivier Matz <olivier.matz@6wind.com>]

Hi Xiao,

Please find few comments below.

On Wed, Jan 10, 2018 at 09:23:54AM +0800, Xiao Wang wrote:
> Suggested-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_net/Makefile            |  1 +
>  lib/librte_net/rte_arp.c           | 42 ++++++++++++++++++++++++++++++++++++++
>  lib/librte_net/rte_arp.h           | 17 +++++++++++++++
>  lib/librte_net/rte_net_version.map |  6 ++++++
>  4 files changed, 66 insertions(+)
>  create mode 100644 lib/librte_net/rte_arp.c
> 
> diff --git a/lib/librte_net/Makefile b/lib/librte_net/Makefile
> index 5e8a76b68..ab290c382 100644
> --- a/lib/librte_net/Makefile
> +++ b/lib/librte_net/Makefile
> @@ -13,6 +13,7 @@ LIBABIVER := 1
>  
>  SRCS-$(CONFIG_RTE_LIBRTE_NET) := rte_net.c
>  SRCS-$(CONFIG_RTE_LIBRTE_NET) += rte_net_crc.c
> +SRCS-$(CONFIG_RTE_LIBRTE_NET) += rte_arp.c
>  
>  # install includes
>  SYMLINK-$(CONFIG_RTE_LIBRTE_NET)-include := rte_ip.h rte_tcp.h rte_udp.h rte_esp.h
> diff --git a/lib/librte_net/rte_arp.c b/lib/librte_net/rte_arp.c
> new file mode 100644
> index 000000000..d7223b044
> --- /dev/null
> +++ b/lib/librte_net/rte_arp.c
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2018 Intel Corporation
> + */
> +
> +#include <arpa/inet.h>
> +
> +#include <rte_arp.h>
> +
> +#define RARP_PKT_SIZE	64
> +int
> +rte_net_make_rarp_packet(struct rte_mbuf *mbuf, const struct ether_addr *mac)
> +{
> +	struct ether_hdr *eth_hdr;
> +	struct arp_hdr *rarp;
> +
> +	if (mbuf->buf_len < RARP_PKT_SIZE)
> +		return -1;
> +
> +	/* Ethernet header. */
> +	eth_hdr = rte_pktmbuf_mtod(mbuf, struct ether_hdr *);
> +	memset(eth_hdr->d_addr.addr_bytes, 0xff, ETHER_ADDR_LEN);
> +	ether_addr_copy(mac, &eth_hdr->s_addr);
> +	eth_hdr->ether_type = htons(ETHER_TYPE_RARP);
> +
> +	/* RARP header. */
> +	rarp = (struct arp_hdr *)(eth_hdr + 1);
> +	rarp->arp_hrd = htons(ARP_HRD_ETHER);
> +	rarp->arp_pro = htons(ETHER_TYPE_IPv4);
> +	rarp->arp_hln = ETHER_ADDR_LEN;
> +	rarp->arp_pln = 4;
> +	rarp->arp_op  = htons(ARP_OP_REVREQUEST);
> +
> +	ether_addr_copy(mac, &rarp->arp_data.arp_sha);
> +	ether_addr_copy(mac, &rarp->arp_data.arp_tha);
> +	memset(&rarp->arp_data.arp_sip, 0x00, 4);
> +	memset(&rarp->arp_data.arp_tip, 0x00, 4);
> +
> +	mbuf->data_len = RARP_PKT_SIZE;
> +	mbuf->pkt_len = RARP_PKT_SIZE;
> +
> +	return 0;
> +}

You don't check that there is enough tailroom to write the packet data.
Also, nothing verifies that the mbuf passed to the function is empty.
I suggest to do the allocation in this function, what do you think?

You can also use rte_pktmbuf_append() to check for the tailroom and
update data_len/pkt_len:

	m = rte_pktmbuf_alloc();
	if (m == NULL)
		return NULL;
	eth_hdr = rte_pktmbuf_append(m, RARP_PKT_SIZE);
	if (eth_hdr == NULL) {
		m_freem(m);
		return NULL;
	}
	eth_hdr->... = ...;
	...
	rarp = (struct arp_hdr *)(eth_hdr + 1);
	rarp->... = ...;
	...

	return m;