On 09.08.2018 11:38, Lam, Tiago wrote:
Hi Ilya,
On 09/08/2018 09:27, Ilya Maximets wrote:
Hmm. I found that this series modifies only dpdk related components
and doesn't pay any attention to others.
dp_packet API was modified to respect the segmented packets, but
there are many places, where code uses packet data directly using
only dp_packet_data() pointer and dp_packet_size().
For example, at least following functions will read the wrong memory
and probably generate segfault:
No, that's not correct. Actually, this has been explained back in June
[1], where Eelco raised the same concerns. There, I replied with:
"This series takes the approach of not allocating new mbufs in
`DPBUF_DPDK` dp_packets. This is to avoid the case where a
dp_packet_put() call, for example, allocates two mbufs to create enough
space, and returns a pointer to the data which isn't contiguous in
memory (because it is spread across two mbufs). Most of the code in OvS
that uses the dp_packet API relies on the assumption that memory
returned is contiguous in memory."
But please do refer to the link for a full explanation. In fact, if that
was the case most of the tests in system-traffic would fail, and that
would show a flaw in the design.
Now, obviously this doesn't mean that in the odd case something may have
slip through the cracks, but all the tests that have been run so far
have given enough confidence.
Tiago.
[1] https://mail.openvswitch.org/pipermail/ovs-dev/2018-June/348502.html
I don't understand what you're talking about.
Just look at the following case:
1. Applying following patch, just to be sure:
---
diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
index 0c42268..bc995bc 100644
--- a/lib/netdev-linux.c
+++ b/lib/netdev-linux.c
@@ -1433,6 +1433,11 @@ netdev_linux_tap_batch_send(struct netdev *netdev_,
ssize_t retval;
int error;
+ if (packet->mbuf.nb_segs > 1) {
+ VLOG_ERR_RL(&rl,
+ "Sending multiseg mbuf as a plain data. nb_segs: %d",
+ packet->mbuf.nb_segs);
+ }
do {
retval = write(netdev->tap_fd, dp_packet_data(packet), size);
error = retval < 0 ? errno : 0;
---
2. Configure OVS:
./bin/ovs-vsctl set Open_vSwitch . other_config:dpdk-multi-seg-mbufs=true
3. Create one bridge with datapath_type "netdev", add one vhostuserclient
port "vhost1" like this:
# ovs-vsctl show
Bridge "ovsdpdk_br0"
Port "vhost1"
Interface "vhost1"
type: dpdkvhostuserclient
options: {vhost-server-path="/vhost1.sock"}
Port "ovsdpdk_br0"
Interface "ovsdpdk_br0"
type: internal
4. Start VM.
5. Set up on host:
# ovs-vsctl set interface vhost1 mtu_request=9000
# ovs-vsctl set interface ovsdpdk_br0 mtu_request=9000
# ifconfig ovsdpdk_br0 192.168.114.20 netmask 255.255.255.0
6. Set up inside VM:
# ifconfig eth0 192.168.114.10 netmask 255.255.255.0 mtu 9000
7. Try to scp large file from VM to Host:
# scp file [email protected]:./
file 13% 2112KB 434.8KB/s - *stalled*
At the same time in tcpdump on the host side:
14:17:51.162168 IP (tos 0x8, ttl 64, id 30567, offset 0, flags [DF], proto TCP
(6), length 9000)
192.168.114.10.43648 > 192.168.114.20.ssh: Flags [.], cksum 0xc831 (incorrect
-> 0x1be9), seq 480:9428, ack 761, win 256, options [nop,nop,TS val 216598 ecr
1685821578], length 8948
14:17:51.582171 IP (tos 0x8, ttl 64, id 30568, offset 0, flags [DF], proto TCP
(6), length 9000)
192.168.114.10.43648 > 192.168.114.20.ssh: Flags [.], cksum 0xc807 (incorrect
-> 0x980f), seq 480:9428, ack 761, win 256, options [nop,nop,TS val 216640 ecr
1685821578], length 8948
14:17:52.422175 IP (tos 0x8, ttl 64, id 30569, offset 0, flags [DF], proto TCP
(6), length 9000)
192.168.114.10.43648 > 192.168.114.20.ssh: Flags [.], cksum 0xc7b3 (incorrect
-> 0x1b6b), seq 480:9428, ack 761, win 256, options [nop,nop,TS val 216724 ecr
1685821578], length 8948
14:17:54.115128 IP (tos 0x8, ttl 64, id 30570, offset 0, flags [DF], proto TCP
(6), length 9000)
192.168.114.10.43648 > 192.168.114.20.ssh: Flags [.], cksum 0xc70b (incorrect
-> 0x9713), seq 480:9428, ack 761, win 256, options [nop,nop,TS val 216892 ecr
1685821578], length 8948
And in OVS log:
2018-08-09T11:17:50Z|00002|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 4
2018-08-09T11:17:50Z|00003|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 5
2018-08-09T11:17:50Z|00004|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 4
2018-08-09T11:17:50Z|00005|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 5
2018-08-09T11:17:50Z|00006|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 5
2018-08-09T11:17:51Z|00007|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 5
2018-08-09T11:17:51Z|00008|netdev_linux(pmd8)|ERR|Sending multiseg mbuf as a
plain data. nb_segs: 5
SCP never finished because of corrupted data.
Same test works fine if other_config:dpdk-multi-seg-mbufs=false.
Best regards, Ilya Maximets.
