Date: Thu, 19 Jan 2017 14:51:27 +0100 From: Vincenzo Maffione <v.maffione@gmail.com> To: David Belle-Isle <dbelleisle@gmail.com> Cc: "freebsd-net@freebsd.org" <net@freebsd.org> Subject: Re: Netmap TX with no impact to host Message-ID: <CA%2B_eA9hEu4ArD6n%2BTrYyCp0h9cp0e5j8rUw_WhuVcW_Vhnjhtg@mail.gmail.com> In-Reply-To: <CAN56noxYyL_Pc_YBoiXcRi-nV5M9k8TOgMEhfE1YYZd1MV9%2BHQ@mail.gmail.com> References: <CAN56nowNx9%2BtpGLbheBoGV==upV=WWmJ4Z8jbH9kprSxb4-0_g@mail.gmail.com> <CA%2B_eA9hausF0N0y7Ff005thOWYREEau4YvJDyT5nC7kK64JhVQ@mail.gmail.com> <CAN56noxYyL_Pc_YBoiXcRi-nV5M9k8TOgMEhfE1YYZd1MV9%2BHQ@mail.gmail.com>
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You're welcome! I know it's a bit difficult to notice, but this is written in the very last sentence of the netmap(4) man page. Cheers, Vincenzo 2017-01-19 13:50 GMT+01:00 David Belle-Isle <dbelleisle@gmail.com>: > Oh! Thank you soooo much! I was missing the last part about the checksum > offloadings and TSO. I disabled them and everything is working perfectly > now! Thank you so much!! > > On Thu, Jan 19, 2017 at 6:00 AM, Vincenzo Maffione <v.maffione@gmail.com> > wrote: > >> Hi, >> Before answering to the question, some important disclaimers. >> >> If you are using FreeBSD-12-current, please be aware that there are IFLIB >> developments in progress that affect em devices. Unfortunately, at the >> moment netmap does not work on em/lem/igb devices because of the switch to >> IFLIB at this commit https://github.com/freebsd/fre >> ebsd/commit/4bf01b136dfa554a57f25559e7a848bf32206c66. Netmap on em works >> correctly right before this commit. >> >> If you are using FreeBSD-11 versions, be aware that netmap in emulated >> mode is broken in those versions. I have the fix for that, but it is not in >> the released code. If you need it, I can give you a patch. Btw, can anyone >> point me at the procedure to push this fix to the relevant release/stable >> branches? >> If you use em devices with DEV_NETMAP enabled, emulated mode is not used, >> so it will work. If you use interfaces without DEV_NETMAP support, emulated >> netmap is used and you are affected by the broken code. >> >> Regarding your question: >> You can build a netmap program that does what you want: >> (1) transmit packets on em0 at high rates using netmap >> (2) let the host stack transmit packets on em0 >> (3) let packets received on em0 to find their way to the host stack. >> >> In netmap it is possible to open just a subset of the TX rings and/or a >> subset of the RX rings. >> In your case you need to open all the TX hw rings (to acheve (1)) and the >> RX host ring (a.k.a. RX sw ring) to achieve (2). >> You achieve (3) by simply not opening the RX hw rings. >> To implement this you need two calls to nm_open() (similarly to what >> bridge does): >> >> pa = nm_open("netmap:em0/T, NULL, 0, NULL); /* open all TX hw rings */ >> pb = nm_open("netmap:em0^/R, NULL, NM_OPEN_NO_MMAP, pa); /* open only RX >> host ring */ >> >> Then you can use "pa" to transmit packets on the hw TX rings (1). >> To implement (2), you have two options: >> (A) your application moves packets from the host RX ring (pb) to the hw >> TX rings (pa). In the end this is the logic of the "bridge" program does, >> so you could start from there. >> (B) you use "transparent mode" in the host->nic direction: applications >> marks with the NS_FORWARD flag the host RX ring slots right before they >> released to the kernel, and the kernel with take care of forward them to >> the TX ring for you. However, be aware this mode is still experimental, and >> not well tested yet. >> >> Regarding the use of bridge, the correct command line for what you want >> to do (forward all packets between host stack and NIC, in both directions) >> is: >> >> # bridge netmap:em0 >> >> However, to let TCP/UDP traffic go correctly, you need to disable tso and >> checksum offloadings on em0, since netmap will not program the NIC to >> perform those offloadings. This is also valid for your custom program above. >> >> Cheers, >> Vincenzo >> >> 2017-01-19 2:51 GMT+01:00 David Belle-Isle <dbelleisle@gmail.com>: >> >>> Hi, >>> >>> I'm trying to open a netmap descriptor to an interface to send packets. >>> However, I don't want to prevent the host to send and receive data >>> (transparent). I don't think this should be hard but I can't figure out >>> how >>> to do this. >>> >>> I tried to run the bridge example in the FreeBSD distribution but even >>> that >>> I can't get to run without stopping the host's networking completely. I >>> tried running ./bridge em0 em0 which, if I understand correctly should >>> open >>> the NIC and host rings and pass the traffic through. As soon as I start >>> it >>> all the networking stops. >>> >>> I tried testing in a VMware VM and on bare-metal with em cards and got >>> the >>> same results with both. >>> >>> Can someone help me? >>> >>> Thanks, >>> >>> David >>> _______________________________________________ >>> freebsd-net@freebsd.org mailing list >>> https://lists.freebsd.org/mailman/listinfo/freebsd-net >>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >> >> >> >> -- >> Vincenzo Maffione >> > > -- Vincenzo Maffione
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