-- Damjan > On 7 Nov 2018, at 19:36, Coulson, Ken <kcoul...@ciena.com> wrote: > > Latest comments inline in yellow below. > > > From: Damjan Marion <dmar...@me.com <mailto:dmar...@me.com>> > Date: Wednesday, November 7, 2018 at 7:34 AM > To: "Coulson, Ken" <kcoul...@ciena.com <mailto:kcoul...@ciena.com>> > Cc: "vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io>" <vpp-dev@lists.fd.io > <mailto:vpp-dev@lists.fd.io>> > Subject: Re: [**EXTERNAL**] [vpp-dev] TAP v1/v2 API questions > > > -- > Damjan > > >> On 7 Nov 2018, at 16:01, Coulson, Ken <kcoul...@ciena.com >> <mailto:kcoul...@ciena.com>> wrote: >> >> Our normal pattern for forwarding plane entities is create/modify/delete, >> the TAP v1 API fit nicely with that. >> The desire is to support changing the interface after it's created without >> deleting and re-creating to avoid as much potential traffic disruption as >> possible. >> An example is MTU (which neither v1 or v2 support). The desired maximum MTU >> may not be known at creation time or may change depending on routing so a >> modify capability seems appropriate. > > VPP have universal API (hw_interface_set_mtu ) for setting MTU on all > interfaces. > So the intent is that from cli the following would set mtu? > ‘set interface mtu 2000 tap0’ does not generate any errors but does not > appear to do anything. ‘ifconfig tap0’ still shows default mtu of 1500.
TAP interface have 2 ends, one is on VPP another one is in linux. that API/CLI sets MTU in VPP->linux direction. In opposite direction you need to use linux tools to set MTU for linux->VPP direction. We may consider sending netlink message to kernel asking for different MTU on remote side, but i'm not sure if that is right thing to do or not, as MTU in theory can bi different on each end.... > > >> So be specific on your questions, want to control MTU and admin/link >> enable/disable, would like to know link status without polling. > > VPP have universal API (sw_interface_set_flags ) for setting link and admin > states. > You can subscribe to interface events with want_interface_events API to be > notified on change. > I’ll give this a try. > > >> >> DPDK TAP PMD (and vHost PMD) provide the same APIs as physical devices using >> the rte_eth_dev_*() functions allowing the next layer of code to very >> similar for physical and virtual devices. > > In some cases we run vPP without DPDK, DPDK is just one device driver option > for VPP. > Good reason! I hadn’t considered that. > > >> DPDK TAP PMD supports MTU, > > see above > > >> jumbo frames > > we support jumbo frames with tapv2. > Do you have some cli examples? I have tried with stock vpp and > as the mtu set does not appear to work I’m unclear how jumbos would work. See above... You can manually change MTU on linux side with "ifconfig" or "ip link". -- Damjan
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