[PATCH v2 2/3] examples/l3fwd: relax the Offload requirement

[Konstantin Ananyev]

13.10.2023 05:27, Trevor Tao пишет:
> Now the port Rx offload mode is set to RTE_ETH_RX_OFFLOAD_CHECKSUM
> by default, but some hw and/or virtual interface does not support
> the offload mode presupposed, e.g., some virtio interfaces in
> the cloud may only partly support RTE_ETH_RX_OFFLOAD_UDP_CKSUM/
> RTE_ETH_RX_OFFLOAD_TCP_CKSUM,
> but not RTE_ETH_RX_OFFLOAD_IPV4_CKSUM, and the error msg here:
> 
> Ethdev port_id=0 requested Rx offloads 0xe does not match Rx offloads
> capabilities 0x201d in rte_eth_dev_configure()
> 
> So to enable the l3fwd running in that environment, the Rx mode requirement
> can be relaxed to reflect the hardware feature reality here, and the l3fwd
> can run smoothly then.
> A warning msg would be provided to user in case it happens here.
> 
> On the other side, enabling the software cksum check in case missing the
> hw support.
> 
> The relax action for rx cksum offload is just enabled when relax_rx_mode is
> true which is false by default.
> 
> Signed-off-by: Trevor Tao <taozj888 at 163.com>
> ---
>   examples/l3fwd/l3fwd.h     | 12 ++++++++++--
>   examples/l3fwd/l3fwd_em.h  |  2 +-
>   examples/l3fwd/l3fwd_lpm.h |  2 +-
>   examples/l3fwd/main.c      | 14 ++++++++++++++
>   4 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/examples/l3fwd/l3fwd.h b/examples/l3fwd/l3fwd.h
> index b55855c932..fd98ad3373 100644
> --- a/examples/l3fwd/l3fwd.h
> +++ b/examples/l3fwd/l3fwd.h
> @@ -159,7 +159,7 @@ send_single_packet(struct lcore_conf *qconf,
>   
>   #ifdef DO_RFC_1812_CHECKS
>   static inline int
> -is_valid_ipv4_pkt(struct rte_ipv4_hdr *pkt, uint32_t link_len)
> +is_valid_ipv4_pkt(struct rte_ipv4_hdr *pkt, uint32_t link_len, uint64_t ol_flags)
>   {
>   	/* From http://www.rfc-editor.org/rfc/rfc1812.txt section 5.2.2 */
>   	/*
> @@ -170,7 +170,15 @@ is_valid_ipv4_pkt(struct rte_ipv4_hdr *pkt, uint32_t link_len)
>   		return -1;
>   
>   	/* 2. The IP checksum must be correct. */
> -	/* this is checked in H/W */
> +	/* if this is not checked in H/W, check it. */
> +	if ((ol_flags & RTE_ETH_RX_OFFLOAD_IPV4_CKSUM) == 0) {

That looks like a wrong flag, I think it should be:
if ((ol_flags & RTE_MBUF_F_RX_IP_CKSUM_MASK) == RTE_MBUF_F_RX_IP_CKSUM_NONE)

Which makes me wonder was that piece of code ever tested properly?


> +		uint16_t actual_cksum, expected_cksum;
> +		actual_cksum = pkt->hdr_checksum;
> +		pkt->hdr_checksum = 0;
> +		expected_cksum = rte_ipv4_cksum(pkt);
> +		if (actual_cksum != expected_cksum)
> +			return -2;
> +	}

Actually, while looking at it another thing stroke me, when HW ip cksum
is enabled, shouldn't we check that it is a valid one?
I.E:
if (ol_flags & RTE_MBUF_F_RX_L4_CKSUM_MASK) == RTE_MBUF_F_RX_L4_CKSUM_BAD)
   return -2;


>   
>   	/*
>   	 * 3. The IP version number must be 4. If the version number is not 4
> diff --git a/examples/l3fwd/l3fwd_em.h b/examples/l3fwd/l3fwd_em.h
> index 7d051fc076..1fee2e2e6c 100644
> --- a/examples/l3fwd/l3fwd_em.h
> +++ b/examples/l3fwd/l3fwd_em.h
> @@ -20,7 +20,7 @@ l3fwd_em_handle_ipv4(struct rte_mbuf *m, uint16_t portid,
>   
>   #ifdef DO_RFC_1812_CHECKS
>   	/* Check to make sure the packet is valid (RFC1812) */
> -	if (is_valid_ipv4_pkt(ipv4_hdr, m->pkt_len) < 0) {
> +	if (is_valid_ipv4_pkt(ipv4_hdr, m->pkt_len, m->ol_flags) < 0) {
>   		rte_pktmbuf_free(m);
>   		return BAD_PORT;
>   	}
> diff --git a/examples/l3fwd/l3fwd_lpm.h b/examples/l3fwd/l3fwd_lpm.h
> index c61b969584..4ee61e8d88 100644
> --- a/examples/l3fwd/l3fwd_lpm.h
> +++ b/examples/l3fwd/l3fwd_lpm.h
> @@ -22,7 +22,7 @@ l3fwd_lpm_simple_forward(struct rte_mbuf *m, uint16_t portid,
>   
>   #ifdef DO_RFC_1812_CHECKS
>   		/* Check to make sure the packet is valid (RFC1812) */
> -		if (is_valid_ipv4_pkt(ipv4_hdr, m->pkt_len) < 0) {
> +		if (is_valid_ipv4_pkt(ipv4_hdr, m->pkt_len, m->ol_flags) < 0) {
>   			rte_pktmbuf_free(m);
>   			return;
>   		}
> diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
> index 89ad546a5e..2b815375a9 100644
> --- a/examples/l3fwd/main.c
> +++ b/examples/l3fwd/main.c
> @@ -1285,6 +1285,20 @@ l3fwd_poll_resource_setup(void)
>   				local_port_conf.rx_adv_conf.rss_conf.rss_hf);
>   		}
>   
> +		/* relax the rx offload requirement */
> +		if ((local_port_conf.rxmode.offloads & dev_info.rx_offload_capa) !=
> +			local_port_conf.rxmode.offloads) {
> +			printf("Port %u requested Rx offloads 0x%"PRIx64" does not"
> +				" match Rx offloads capabilities 0x%"PRIx64"\n",
> +				portid, local_port_conf.rxmode.offloads,
> +				dev_info.rx_offload_capa);
> +			if (relax_rx_mode) {
> +				local_port_conf.rxmode.offloads &= dev_info.rx_offload_capa;
> +				printf("warning: modified the rx offload to 0x%"PRIx64" based on device"
> +				" capability\n", local_port_conf.rxmode.offloads);
> +			}
> +		}
> +

Still not sure it is a good thing to disable L4 cksum offload.
We definetly don't need it for LPM fwd, for EM/ACL - it is an open 
question, as we do lookup on L4 ports too...
If we don't need it completely, why to request it after all?


>   		ret = rte_eth_dev_configure(portid, nb_rx_queue,
>   					(uint16_t)n_tx_queue, &local_port_conf);
>   		if (ret < 0)