Re: [dpdk-dev] [PATCH v5 5/6] ethdev: unify MTU checks

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 10/9/2021 12:43 PM, lihuisong (C) wrote:
> Hi, Ferruh
> 
> 在 2021/10/8 0:56, Ferruh Yigit 写道:
>> Both 'rte_eth_dev_configure()' & 'rte_eth_dev_set_mtu()' sets MTU but
>> have slightly different checks. Like one checks min MTU against
>> RTE_ETHER_MIN_MTU and other RTE_ETHER_MIN_LEN.
>>
>> Checks moved into common function to unify the checks. Also this has
>> benefit to have common error logs.
>>
>> Suggested-by: Huisong Li <lihuisong@huawei.com>
>> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
>> ---
>>   lib/ethdev/rte_ethdev.c | 82 ++++++++++++++++++++++++++---------------
>>   lib/ethdev/rte_ethdev.h |  2 +-
>>   2 files changed, 54 insertions(+), 30 deletions(-)
>>
>> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
>> index c2b624aba1a0..0a6e952722ae 100644
>> --- a/lib/ethdev/rte_ethdev.c
>> +++ b/lib/ethdev/rte_ethdev.c
>> @@ -1336,6 +1336,47 @@ eth_dev_get_overhead_len(uint32_t max_rx_pktlen, uint16_t max_mtu)
>>       return overhead_len;
>>   }
>> +/* rte_eth_dev_info_get() should be called prior to this function */
>> +static int
>> +eth_dev_validate_mtu(uint16_t port_id, struct rte_eth_dev_info *dev_info,
>> +        uint16_t mtu)
>> +{
>> +    uint16_t overhead_len;
>> +    uint32_t frame_size;
>> +
>> +    if (mtu < dev_info->min_mtu) {
>> +        RTE_ETHDEV_LOG(ERR,
>> +            "MTU (%u) < device min MTU (%u) for port_id %u\n",
>> +            mtu, dev_info->min_mtu, port_id);
>> +        return -EINVAL;
>> +    }
>> +    if (mtu > dev_info->max_mtu) {
>> +        RTE_ETHDEV_LOG(ERR,
>> +            "MTU (%u) > device max MTU (%u) for port_id %u\n",
>> +            mtu, dev_info->max_mtu, port_id);
>> +        return -EINVAL;
>> +    }
>> +
>> +    overhead_len = eth_dev_get_overhead_len(dev_info->max_rx_pktlen,
>> +            dev_info->max_mtu);
>> +    frame_size = mtu + overhead_len;
>> +    if (frame_size < RTE_ETHER_MIN_LEN) {
>> +        RTE_ETHDEV_LOG(ERR,
>> +            "Frame size (%u) < min frame size (%u) for port_id %u\n",
>> +            frame_size, RTE_ETHER_MIN_LEN, port_id);
>> +        return -EINVAL;
>> +    }
>> +
>> +    if (frame_size > dev_info->max_rx_pktlen) {
>> +        RTE_ETHDEV_LOG(ERR,
>> +            "Frame size (%u) > device max frame size (%u) for port_id %u\n",
>> +            frame_size, dev_info->max_rx_pktlen, port_id);
>> +        return -EINVAL;
>> +    }
> 
> This function is used to verify the MTU. So "frame_size" is redundant.
> 

Yes it is redundant for the drivers that both announce 'max_rx_pktlen' & 'max_mtu',
but stil some drivers doesn't announce the 'max_mtu' values and default value
'UINT16_MAX' is set by ethdev, specially virtual drivers.
That is why I kept both to be in safe side.

> As modified by this patch, dev_info->min_mtu is calculated based on RTE_ETHER_MIN_LEN.
> 

And for the min check, for the default 'min_mtu' check is redundant, but for the cases
driver sets "min_mtu < (RTE_ETHER_MIN_LEN - overhead_len)" second check becomes
different limit. I don't know if this happens at all in practice but I think it
doesn't hurt to have both checks to be on safe side.

>> +
>> +    return 0;
>> +}
>> +
>>   int
>>   rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
>>                 const struct rte_eth_conf *dev_conf)
>> @@ -1463,26 +1504,13 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
>>           goto rollback;
>>       }
>> -    /*
>> -     * Check that the maximum RX packet length is supported by the
>> -     * configured device.
>> -     */
>>       if (dev_conf->rxmode.mtu == 0)
>>           dev->data->dev_conf.rxmode.mtu = RTE_ETHER_MTU;
>> -    max_rx_pktlen = dev->data->dev_conf.rxmode.mtu + overhead_len;
>> -    if (max_rx_pktlen > dev_info.max_rx_pktlen) {
>> -        RTE_ETHDEV_LOG(ERR,
>> -            "Ethdev port_id=%u max_rx_pktlen %u > max valid value %u\n",
>> -            port_id, max_rx_pktlen, dev_info.max_rx_pktlen);
>> -        ret = -EINVAL;
>> -        goto rollback;
>> -    } else if (max_rx_pktlen < RTE_ETHER_MIN_LEN) {
>> -        RTE_ETHDEV_LOG(ERR,
>> -            "Ethdev port_id=%u max_rx_pktlen %u < min valid value %u\n",
>> -            port_id, max_rx_pktlen, RTE_ETHER_MIN_LEN);
>> -        ret = -EINVAL;
>> +
>> +    ret = eth_dev_validate_mtu(port_id, &dev_info,
>> +            dev->data->dev_conf.rxmode.mtu);
>> +    if (ret != 0)
>>           goto rollback;
>> -    }
>>       dev->data->mtu = dev->data->dev_conf.rxmode.mtu;
>> @@ -1491,6 +1519,9 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
>>        * size is supported by the configured device.
>>        */
>>       if (dev_conf->rxmode.offloads & DEV_RX_OFFLOAD_TCP_LRO) {
>> +        overhead_len = eth_dev_get_overhead_len(dev_info.max_rx_pktlen,
>> +                dev_info.max_mtu);
>> +        max_rx_pktlen = dev->data->dev_conf.rxmode.mtu + overhead_len;
>>           if (dev_conf->rxmode.max_lro_pkt_size == 0)
>>               dev->data->dev_conf.rxmode.max_lro_pkt_size = max_rx_pktlen;
>>           ret = eth_dev_check_lro_pkt_size(port_id,
>> @@ -3437,7 +3468,8 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
>>       dev_info->rx_desc_lim = lim;
>>       dev_info->tx_desc_lim = lim;
>>       dev_info->device = dev->device;
>> -    dev_info->min_mtu = RTE_ETHER_MIN_MTU;
>> +    dev_info->min_mtu = RTE_ETHER_MIN_LEN - RTE_ETHER_HDR_LEN -
>> +        RTE_ETHER_CRC_LEN;
> I suggest that the adjustment to the minimum mtu size is also explicitly reflected in the commit log.

ack, I will

>>       dev_info->max_mtu = UINT16_MAX;
>>       RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->dev_infos_get, -ENOTSUP);
>> @@ -3643,21 +3675,13 @@ rte_eth_dev_set_mtu(uint16_t port_id, uint16_t mtu)
>>        * which relies on dev->dev_ops->dev_infos_get.
>>        */
>>       if (*dev->dev_ops->dev_infos_get != NULL) {
>> -        uint16_t overhead_len;
>> -        uint32_t frame_size;
>> -
>>           ret = rte_eth_dev_info_get(port_id, &dev_info);
>>           if (ret != 0)
>>               return ret;
>> -        if (mtu < dev_info.min_mtu || mtu > dev_info.max_mtu)
>> -            return -EINVAL;
>> -
>> -        overhead_len = eth_dev_get_overhead_len(dev_info.max_rx_pktlen,
>> -                dev_info.max_mtu);
>> -        frame_size = mtu + overhead_len;
>> -        if (mtu < RTE_ETHER_MIN_MTU || frame_size > dev_info.max_rx_pktlen)
>> -            return -EINVAL;
>> +        ret = eth_dev_validate_mtu(port_id, &dev_info, mtu);
>> +        if (ret != 0)
>> +            return ret;
>>       }
>>       ret = (*dev->dev_ops->mtu_set)(dev, mtu);
>> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
>> index 4d0f956a4b28..50e124ff631f 100644
>> --- a/lib/ethdev/rte_ethdev.h
>> +++ b/lib/ethdev/rte_ethdev.h
>> @@ -3056,7 +3056,7 @@ int rte_eth_macaddr_get(uint16_t port_id, struct rte_ether_addr *mac_addr);
>>    *  };
>>    *
>>    * device = dev->device
>> - * min_mtu = RTE_ETHER_MIN_MTU
>> + * min_mtu = RTE_ETHER_MIN_LEN - RTE_ETHER_HDR_LEN - RTE_ETHER_CRC_LEN
>>    * max_mtu = UINT16_MAX
>>    *
>>    * The following fields will be populated if support for dev_infos_get()