From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>
Cc: dev@dpdk.org, konstantin.ananyev@intel.com,
sugesh.chandran@intel.com, bruce.richardson@intel.com,
jianfeng.tan@intel.com, helin.zhang@intel.com,
adrien.mazarguil@6wind.com, stephen@networkplumber.org,
dprovan@bivio.net, xiao.w.wang@intel.com
Subject: Re: [dpdk-dev] [PATCH v2 12/12] virtio: add Tso support
Date: Thu, 13 Oct 2016 23:29:35 +0800 [thread overview]
Message-ID: <20161013152935.GZ16751@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <57FFA50C.6030805@6wind.com>
On Thu, Oct 13, 2016 at 05:15:24PM +0200, Olivier MATZ wrote:
>
>
> On 10/13/2016 05:01 PM, Yuanhan Liu wrote:
> >On Thu, Oct 13, 2016 at 04:52:25PM +0200, Olivier MATZ wrote:
> >>
> >>
> >>On 10/13/2016 04:16 PM, Yuanhan Liu wrote:
> >>>On Thu, Oct 13, 2016 at 04:02:49PM +0200, Olivier MATZ wrote:
> >>>>
> >>>>
> >>>>On 10/13/2016 10:18 AM, Yuanhan Liu wrote:
> >>>>>On Mon, Oct 03, 2016 at 11:00:23AM +0200, Olivier Matz wrote:
> >>>>>>+/* When doing TSO, the IP length is not included in the pseudo header
> >>>>>>+ * checksum of the packet given to the PMD, but for virtio it is
> >>>>>>+ * expected.
> >>>>>>+ */
> >>>>>>+static void
> >>>>>>+virtio_tso_fix_cksum(struct rte_mbuf *m)
> >>>>>>+{
> >>>>>>+ /* common case: header is not fragmented */
> >>>>>>+ if (likely(rte_pktmbuf_data_len(m) >= m->l2_len + m->l3_len +
> >>>>>>+ m->l4_len)) {
> >>>>>...
> >>>>>>+ /* replace it in the packet */
> >>>>>>+ th->cksum = new_cksum;
> >>>>>>+ } else {
> >>>>>...
> >>>>>>+ /* replace it in the packet */
> >>>>>>+ *rte_pktmbuf_mtod_offset(m, uint8_t *,
> >>>>>>+ m->l2_len + m->l3_len + 16) = new_cksum.u8[0];
> >>>>>>+ *rte_pktmbuf_mtod_offset(m, uint8_t *,
> >>>>>>+ m->l2_len + m->l3_len + 17) = new_cksum.u8[1];
> >>>>>>+ }
> >>>>>
> >>>>>The tcp header will always be in the mbuf, right? Otherwise, you can't
> >>>>>update the cksum field here. What's the point of introducing the "else
> >>>>>clause" then?
> >>>>
> >>>>Sorry, I don't see the problem you're pointing out here.
> >>>>
> >>>>What I want to solve here is to support the cases where the mbuf is
> >>>>segmented in the middle of the network header (which is probably a rare
> >>>>case).
> >>>
> >>>How it's gonna segmented?
> >>
> >>The mbuf is given by the application. So if the application generates a
> >>segmented mbuf, it should work.
> >>
> >>This could happen for instance if the application uses mbuf clones to share
> >>the IP/TCP/data part of the mbuf and prepend a specific Ethernet/vlan for
> >>different destination.
> >>
> >>
> >>>>In the "else" part, I only access the mbuf byte by byte using the
> >>>>rte_pktmbuf_mtod_offset() accessor. An alternative would have been to copy
> >>>>the header in a linear buffer, fix the checksum, then copy it again in the
> >>>>packet, but there is no mbuf helpers to do these copies for now.
> >>>
> >>>In the "else" clause, the ip header is still in the mbuf, right?
> >>>Why do you have to access it the way like:
> >>>
> >>> ip_version = *rte_pktmbuf_mtod_offset(m, uint8_t *,
> >>> m->l2_len) >> 4;
> >>>
> >>>Why can't you just use
> >>>
> >>> iph = rte_pktmbuf_mtod_offset(m, struct ipv4_hdr *, m->l2_len);
> >>> iph->version_ihl ....;
> >>
> >>AFAIK, there is no requirement that each network header has to be contiguous
> >>in a mbuf segment.
> >>
> >>Of course, a split in the middle of a network header probably never
> >>happens... but we never knows, as it is not forbidden. I think the code
> >>should be robust enough to avoid accesses to wrong addresses.
> >>
> >>Hope it's clear enough :)
> >
> >Thanks, but not really. Maybe let me ask this way: what wrong would
> >happen if we use
> > iph = rte_pktmbuf_mtod_offset(m, struct ipv4_hdr *, m->l2_len);
> >to access the IP header? Is it about the endian?
>
> If you have a packet split like this:
>
> mbuf segment 1 mbuf segment 2
> ---------------------------- ------------------------------
> | Ethernet header | IP hea| |der | TCP header | data
> ---------------------------- ------------------------------
> ^
> iph
Thanks, that's clear. How could you be able to access the tcp header
from the first mbuf then? I mean, how is the following code supposed
to work?
prev_cksum.u8[0] = *rte_pktmbuf_mtod_offset(m, uint8_t *,
m->l2_len + m->l3_len + 16);
> The IP header is not contiguous. So accessing to the end of the structure
> will access to a wrong location.
>
> >One more question is do you have any case to trigger the "else" clause?
>
> No, but I think it may happen.
A piece of untest code is not trusted though ...
--yliu
next prev parent reply other threads:[~2016-10-13 15:28 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-21 8:08 [dpdk-dev] [PATCH 00/12] net/virtio: add offload support Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 01/12] virtio: move device initialization in a function Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 02/12] virtio: setup and start cq in configure callback Olivier Matz
2016-07-21 21:15 ` Stephen Hemminger
2016-07-22 7:54 ` Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 03/12] virtio: reinitialize the device " Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 04/12] mbuf: add function to calculate a checksum Olivier Matz
2016-07-21 10:51 ` Ananyev, Konstantin
2016-07-21 16:26 ` Don Provan
2016-07-21 16:46 ` Olivier Matz
2016-07-22 8:24 ` Olivier Matz
2016-08-29 14:52 ` Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 05/12] mbuf: add new Rx checksum mbuf flags Olivier Matz
2016-07-21 21:22 ` Stephen Hemminger
2016-07-22 8:03 ` Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 06/12] app/testpmd: fix checksum stats in csum engine Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 07/12] mbuf: new flag for LRO Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 08/12] app/testpmd: display lro segment size Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 09/12] virtio: add Rx checksum offload support Olivier Matz
2016-07-27 9:52 ` Wang, Xiao W
2016-07-21 8:08 ` [dpdk-dev] [PATCH 10/12] virtio: add Tx " Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 11/12] virtio: add Lro support Olivier Matz
2016-07-21 8:08 ` [dpdk-dev] [PATCH 12/12] virtio: add Tso support Olivier Matz
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 00/12] net/virtio: add offload support Olivier Matz
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 01/12] virtio: move device initialization in a function Olivier Matz
2016-10-11 12:30 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 02/12] virtio: setup and start cq in configure callback Olivier Matz
2016-10-11 12:47 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 03/12] virtio: reinitialize the device " Olivier Matz
2016-10-11 13:13 ` Maxime Coquelin
2016-10-12 14:41 ` Yuanhan Liu
2016-10-12 16:01 ` Olivier MATZ
2016-10-13 7:54 ` Yuanhan Liu
2016-10-13 13:57 ` Olivier MATZ
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 04/12] net: add function to calculate a checksum in a mbuf Olivier Matz
2016-10-11 13:25 ` Maxime Coquelin
2016-10-11 13:33 ` Olivier MATZ
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 05/12] mbuf: add new Rx checksum mbuf flags Olivier Matz
2016-10-11 13:43 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 06/12] app/testpmd: fix checksum stats in csum engine Olivier Matz
2016-10-11 13:46 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 07/12] mbuf: new flag for LRO Olivier Matz
2016-10-11 13:48 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 08/12] app/testpmd: display lro segment size Olivier Matz
2016-10-11 13:49 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 09/12] virtio: add Rx checksum offload support Olivier Matz
2016-10-03 12:51 ` Maxime Coquelin
2016-10-05 11:56 ` Olivier Matz
2016-10-05 13:27 ` Maxime Coquelin
2016-10-05 13:30 ` Olivier Matz
2016-10-12 13:02 ` Yuanhan Liu
2016-10-12 15:55 ` Olivier MATZ
2016-10-11 14:04 ` Maxime Coquelin
2016-10-11 14:29 ` Olivier MATZ
2016-10-11 14:36 ` Maxime Coquelin
2016-10-11 14:49 ` Olivier MATZ
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 10/12] virtio: add Tx " Olivier Matz
2016-10-07 7:25 ` Maxime Coquelin
2016-10-07 16:36 ` Olivier Matz
2016-10-13 8:38 ` Yuanhan Liu
2016-10-13 13:58 ` Olivier MATZ
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 11/12] virtio: add Lro support Olivier Matz
2016-10-11 14:21 ` Maxime Coquelin
2016-10-03 9:00 ` [dpdk-dev] [PATCH v2 12/12] virtio: add Tso support Olivier Matz
2016-10-13 8:18 ` Yuanhan Liu
2016-10-13 14:02 ` Olivier MATZ
2016-10-13 14:16 ` Yuanhan Liu
2016-10-13 14:52 ` Olivier MATZ
2016-10-13 15:01 ` Yuanhan Liu
2016-10-13 15:15 ` Olivier MATZ
2016-10-13 15:29 ` Yuanhan Liu [this message]
2016-10-13 15:45 ` Olivier Matz
2016-10-13 16:01 ` Yuanhan Liu
2016-10-13 15:04 ` Yuanhan Liu
2016-10-13 23:33 ` Stephen Hemminger
2016-10-18 14:07 ` Olivier Matz
2016-10-11 11:35 ` [dpdk-dev] [PATCH v2 00/12] net/virtio: add offload support Yuanhan Liu
2016-10-11 12:14 ` Olivier MATZ
2016-10-11 15:37 ` Yuanhan Liu
2016-10-13 14:15 ` [dpdk-dev] [PATCH v3 " Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 01/12] net/virtio: move device initialization in a function Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 02/12] net/virtio: setup and start cq in configure callback Olivier Matz
2016-11-02 1:38 ` Yao, Lei A
2016-11-08 14:58 ` Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 03/12] net/virtio: reinitialize the device " Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 04/12] net: add function to calculate a checksum in a mbuf Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 05/12] mbuf: add new Rx checksum mbuf flags Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 06/12] app/testpmd: adapt checksum stats in csum engine Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 07/12] mbuf: new flag for LRO Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 08/12] app/testpmd: display lro segment size Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 09/12] net/virtio: add Rx checksum offload support Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 10/12] net/virtio: add Tx " Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 11/12] net/virtio: add Lro support Olivier Matz
2016-10-13 14:16 ` [dpdk-dev] [PATCH v3 12/12] net/virtio: add Tso support Olivier Matz
2016-10-13 16:05 ` Yuanhan Liu
2016-10-13 18:50 ` Thomas Monjalon
2016-10-13 19:58 ` Olivier Matz
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