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

  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@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(-)
  

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@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)