Date: Mon, 26 Sep 2022 11:21:19 -0600 From: Kim Shrier <kim@westryn.net> To: Vincenzo Maffione <vmaffione@freebsd.org> Cc: "net@freebsd.org" <net@freebsd.org>, Giuseppe Lettieri <giuseppe.lettieri@unipi.it> Subject: Re: Forwarding packets to the host stack in net map lb app Message-ID: <DBB84FA5-B7AF-40F1-A76D-FDE50E608686@westryn.net> In-Reply-To: <CA%2B_eA9jkCYAfTeXho4fNTsqwSCXmxwCuvxkQV3BD_uz9XAAv4w@mail.gmail.com> References: <CB07794F-4719-4C1D-B64C-05C8335D329F@westryn.net> <CA%2B_eA9jkCYAfTeXho4fNTsqwSCXmxwCuvxkQV3BD_uz9XAAv4w@mail.gmail.com>
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Thanks for your input. In the interim, I have actually implemented your second (harder) option = and it appears to be working quite well. I am still testing but it does = look promising. Kim > On Sep 26, 2022, at 10:05 AM, Vincenzo Maffione = <vmaffione@freebsd.org> wrote: >=20 > I think you could avoid any modifications to lb(8) and take advantage = of the "multiple pipe groups" feature. > You open two groups,=20 > # lb -i netmap:em0/R -p mon:$N -p fwd:$M [...] > Each group receives all the packets arriving on the RX (NIC) rings of = em0. (I'm pretty sure) this happens without packet copies, i.e. by = swapping netmap slots. >=20 > The first group (mon) is for your existing monitor process. The second = one (fwd) would be used for a separate process that handles the host = stack: > - It reads from fwd:$M pipes, selecting only the RX packets that = should be forwarded to the host stack. Selected packets will be = forwarded to netmap:em0^/T. All the other packets are just dropped. > - it forwards all traffic from netmap:em0^/R to netmap:em0/T (e.g. = from the em0 host RX ring to the em0 TX rings). Keep in mind that lb = does not touch em0 TX rings, so there would not be conflicts. In any = case, it is good practice to have lb only open RX rings (netmap:em0/R). > This second process can probably be a modified version of the netmap = bridge, although you have asymmetric three-party forwarding here (fwd/R = --> netmap:em0^T, netmap:em0^/R --> netmap:em0/T). >=20 > The alternative (harder) option would be to actually modify lb(8). You = should probably: > - open netmap:em0^/R and netmap:em0*/T with separate nmport_open() = calls > - parse the packet before pkt_hdr_hash() to select the RX packets = that you need to forward to the host TX ring, and modify the forwarding = logic to perform this task. > - modify the logic of the lb poll() loop so that it also performs the = forwarding from host RX rings to NIC TX rings > I'm not sure that you would have any advantages by choosing this path. >=20 > Cheers, > Vincenzo >=20
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