From: Stephen Hemminger <stephen@networkplumber.org>
To: Francesco Mancino <francesco.mancino@tutus.se>
Cc: dev@dpdk.org
Subject: Re: [PATCH v7] net/tap: Allow jumbo frames
Date: Mon, 8 Aug 2022 09:42:26 -0700 [thread overview]
Message-ID: <20220808094226.4775124e@hermes.local> (raw)
In-Reply-To: <93cbc18c-fcc4-d34d-4419-5268513f7b87@tutus.se>
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:[~2022-08-08 16:42 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 [this message]
2022-08-09 7:57 ` Francesco Mancino
2023-01-19 14:50 ` Ferruh Yigit
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