From: Francesco Mancino <francesco.mancino@tutus.se>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: dev@dpdk.org
Subject: Re: [PATCH v7] net/tap: Allow jumbo frames
Date: Tue, 9 Aug 2022 09:57:41 +0200 [thread overview]
Message-ID: <52178e78-b630-3f97-9a3f-b2356ff426c9@tutus.se> (raw)
In-Reply-To: <20220808094226.4775124e@hermes.local>
Interesting, did not know about that attribute.
Tested some tap devices on my machine and get a maxmtu value close to
max uint16, way bigger than RTE_ETHER_MAX_JUMBO_FRAME_LEN.
I do not know if will have time to code and test using netlink to set this limit,
for the time being i think RTE_ETHER_MAX_JUMBO_FRAME_LEN is better than the previous limit.
On 2022-08-08 18:42, Stephen Hemminger wrote:
> On Mon, 8 Aug 2022 17:38:21 +0200
> Francesco Mancino <francesco.mancino@tutus.se> wrote:
>
>> Thank you for the feedback.
>>
>> I am sorry for the email spam, it was a learning process.
>>
>> I am not sure what results we would get by querying the MTU
>> before configuring it, since we can (and do) set the MTU using
>> SIOCSIFMTU.
>>
>> On 2022-08-08 17:03, Stephen Hemminger wrote:
>>> On Mon, 8 Aug 2022 16:49:44 +0200
>>> Francesco Mancino <francesco.mancino@tutus.se> wrote:
>>>
>>>> eth_dev_validate_mtu, introduced in 990912e676e, validates configured
>>>> MTU plus overhead against max_rx_pktlen.
>>>> Since TAP is a virtual device, it should support as big MTU as possible.
>>>>
>>>> Signed-off-by: Francesco Mancino <francesco.mancino@tutus.se>
>>> dev_info->min_rx_bufsize = 0;
>>>
>>>
>>> Thanks for your patience.
>>>
>>> Since tap is built on top of an existing kernel network device a more
>>> complete solution would be to query the kernel device to find out what
>>> its MTU is.
>>>
>>> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
>>>
>>
>
> There is an attribute IFLA_MAX_MTU reported by devices over netlink.
>
> $ ip -d li show dev enp2s0
> 2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq state UP mode DEFAULT group default qlen 1000
> link/ether d8:5e:d3:06:5d:13 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 9194 addrgenmode none numtxqueues 1 numrxqueues 1 gso_max_size 64000 gso_max_segs 64 gro_max_size 65536 parentbus pci parentdev 0000:02:00.0
>
> Notice maxmtu of 9194 reported.
>
> Tap device already has a netlink infrastructure
>
next prev parent reply other threads:[~2022-08-09 7:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-08 9:31 [PATCH] " Francesco Mancino
2022-08-08 14:41 ` Stephen Hemminger
2022-08-08 14:49 ` [PATCH v7] " Francesco Mancino
2022-08-08 15:03 ` Stephen Hemminger
2022-08-08 15:38 ` Francesco Mancino
2022-08-08 16:42 ` Stephen Hemminger
2022-08-09 7:57 ` Francesco Mancino [this message]
2023-01-19 14:50 ` Ferruh Yigit
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