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[Bug 1889943] Re: Improper TCP/IP packet splitting on e1000e/vmxnet3
|
From: |
Patrick Magauran |
|
Subject: |
[Bug 1889943] Re: Improper TCP/IP packet splitting on e1000e/vmxnet3 |
|
Date: |
Sun, 02 Aug 2020 15:59:10 -0000 |
Some more clarifications:
It appears the QEMU does turn on the vnet_hdr flag of the tap interface in most
cases, not just host-only networks. My previous assumption was due to the way
the libvirt manages it, only setting it if the virtio interface is used.
Still, for software fragmentation implementations, ip fragmentation
should be a last resort.
I have also confirmed a suspicion that the current implementation of sw
fragmentation will not work with IPV6. It creates malformed packets as
ipv6 requires a different setup of headers to fragment. Thanks to the
many redundancies in the network stack, the packets eventually arrive at
the host server correctly formed, but we should not rely on this fact.
** Description changed:
+ Update: The sw implementation of fragmentation also creates malformed
+ IPv6 packets when their size is above the MTU. See comment #3
+
Problem Description:
- When using a tap interface and the guest sends a TCP packet that would need
to be segmented, it is fragmented using IP fragmentation. The host does not
reassemble the IP fragments and forwards them to the next hop. This causes
issues on certain ISPs, which seemingly reject IP fragments(Verizon Fios).
- This issue occurs on the e1000e and vmxnet3 NIC models, and possibly others.
It does not occur on the virtio(which passes the entire packet through to the
host w/o fragmentation or segmentation) or the e1000 model().
+ When using a tap interface and the guest sends a TCP packet that would need
to be segmented, it is fragmented using IP fragmentation. The host does not
reassemble the IP fragments and forwards them to the next hop. This causes
issues on certain ISPs, which seemingly reject IP fragments(Verizon Fios).
+ This issue occurs on the e1000e and vmxnet3 NIC models, and possibly others.
It does not occur on the virtio(which passes the entire packet through to the
host w/o fragmentation or segmentation) or the e1000 model().
Test scenario:
Setup a tap and network bridge using the directions here:
https://gist.github.com/extremecoders-re/e8fd8a67a515fee0c873dcafc81d811c
Boot the machine into any modern guest(a Fedora 31 live iso was used for
testing)
Begin a wireshark capture on the host machine
On the host(or another machine on the network) run: npx http-echo-server(See
https://github.com/watson/http-echo-server)
On the guest run
Curl -d “Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas
venenatis viverra ipsum, ac tincidunt est rhoncus eu. Suspendisse vehicula
congue ante, non rhoncus elit tempus vitae. Duis ac leo massa. Donec rutrum
condimentum turpis nec ultricies. Duis laoreet elit eu arcu pulvinar, vitae
congue neque mattis. Mauris sed ante nunc. Vestibulum vitae urna a tellus
maximus sagittis. Vivamus luctus pellentesque neque, vel tempor purus porta ut.
Phasellus at quam bibendum, fermentum libero sit amet, ullamcorper mauris. In
rutrum sit amet dui id maximus. Ut lectus ligula, hendrerit nec aliquam non,
finibus a turpis. Proin scelerisque convallis ante, et pharetra elit. Donec
nunc nisl, viverra vitae dui at, posuere rhoncus nibh. Mauris in massa quis
neque posuere placerat quis quis massa. Donec quis lacus ligula. Donec mollis
vel nisi eget elementum. Nam id magna porta nunc consectetur efficitur ac quis
lorem. Cras faucibus vel ex porttitor mattis. Praesent in mattis tortor. In
venenatis convallis quam, in posuere nibh. Proin non dignissim massa. Cras at
mi ut lorem tristique fringilla. Nulla ac quam condimentum metus tincidunt
vulputate ut at leo. Nunc pellentesque, nunc vel rhoncus condimentum, arcu sem
molestie augue, in suscipit mauris odio mollis odio. Integer hendrerit lectus a
leo facilisis, in accumsan urna maximus. Nam nec odio volutpat, varius est id,
tempus libero. Vestibulum lobortis tortor quam, ac scelerisque urna rhoncus in.
Etiam tempor, est sit amet vulputate molestie, urna neque sodales leo, sit amet
blandit risus felis sed est. Nulla eu eros nec tortor dapibus maximus faucibus
ut erat. Ut pharetra tempor massa in bibendum. Interdum et malesuada fames ac
ante ipsum primis in faucibus. Etiam mattis molestie felis eu efficitur. Morbi
tincidunt consectetur diam tincidunt feugiat. Morbi euismod ut lorem finibus
pellentesque. Aliquam eu porta ex. Aliquam cursus, orci sit amet volutpat
egestas, est est pulvinar erat, sed luctus nisl ligula eget justo vestibulum.”
<ECHOSERVERIP:PORT>
2000 bytes of Lorem Ipsum taken from https://www.lipsum.com/
Compare results from an e1000, a virtio, and a e1000e card:
+--------+-----------+---------+------------+
| Model | Fragment | Segment | Wire Size |
+--------+-----------+---------+------------+
| e1000e | Yes | NO | 1484 + 621 |
+--------+-----------+---------+------------+
| e1000 | No | Yes | 1516 + 620 |
+--------+-----------+---------+------------+
| Virtio | NO | NO | 2068 |
+--------+-----------+---------+------------+
Expected Results:
TCP Segment to proper size OR pass full size to host and let the host split
if necessary.
Configuration changes that did not work:
Disable host, guest, router firewalls
Different Hosts
Different Physical NICs
Libvirt based NAT/Routed modes
Fedora 32 vs 31
Qemu 4.2.0 vs github commit d74824cf7c8b352f9045e949dc636c7207a41eee
System Information:
lsb_release -rd
Description: Fedora release 32 (Thirty Two)
Release: 32
uname -a
Linux pats-laptop-linux 5.7.10-201.fc32.x86_64 #1 SMP Thu Jul 23 00:58:39 UTC
2020 x86_64 x86_64 x86_64 GNU/Linux
I can provide additional logs, debug info, etc. if needed.
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https://bugs.launchpad.net/bugs/1889943
Title:
Improper TCP/IP packet splitting on e1000e/vmxnet3
Status in QEMU:
New
Bug description:
Update: The sw implementation of fragmentation also creates malformed
IPv6 packets when their size is above the MTU. See comment #3
Problem Description:
When using a tap interface and the guest sends a TCP packet that would need
to be segmented, it is fragmented using IP fragmentation. The host does not
reassemble the IP fragments and forwards them to the next hop. This causes
issues on certain ISPs, which seemingly reject IP fragments(Verizon Fios).
This issue occurs on the e1000e and vmxnet3 NIC models, and possibly others.
It does not occur on the virtio(which passes the entire packet through to the
host w/o fragmentation or segmentation) or the e1000 model().
Test scenario:
Setup a tap and network bridge using the directions here:
https://gist.github.com/extremecoders-re/e8fd8a67a515fee0c873dcafc81d811c
Boot the machine into any modern guest(a Fedora 31 live iso was used for
testing)
Begin a wireshark capture on the host machine
On the host(or another machine on the network) run: npx http-echo-server(See
https://github.com/watson/http-echo-server)
On the guest run
Curl -d “Lorem ipsum dolor sit amet, consectetur adipiscing elit. Maecenas
venenatis viverra ipsum, ac tincidunt est rhoncus eu. Suspendisse vehicula
congue ante, non rhoncus elit tempus vitae. Duis ac leo massa. Donec rutrum
condimentum turpis nec ultricies. Duis laoreet elit eu arcu pulvinar, vitae
congue neque mattis. Mauris sed ante nunc. Vestibulum vitae urna a tellus
maximus sagittis. Vivamus luctus pellentesque neque, vel tempor purus porta ut.
Phasellus at quam bibendum, fermentum libero sit amet, ullamcorper mauris. In
rutrum sit amet dui id maximus. Ut lectus ligula, hendrerit nec aliquam non,
finibus a turpis. Proin scelerisque convallis ante, et pharetra elit. Donec
nunc nisl, viverra vitae dui at, posuere rhoncus nibh. Mauris in massa quis
neque posuere placerat quis quis massa. Donec quis lacus ligula. Donec mollis
vel nisi eget elementum. Nam id magna porta nunc consectetur efficitur ac quis
lorem. Cras faucibus vel ex porttitor mattis. Praesent in mattis tortor. In
venenatis convallis quam, in posuere nibh. Proin non dignissim massa. Cras at
mi ut lorem tristique fringilla. Nulla ac quam condimentum metus tincidunt
vulputate ut at leo. Nunc pellentesque, nunc vel rhoncus condimentum, arcu sem
molestie augue, in suscipit mauris odio mollis odio. Integer hendrerit lectus a
leo facilisis, in accumsan urna maximus. Nam nec odio volutpat, varius est id,
tempus libero. Vestibulum lobortis tortor quam, ac scelerisque urna rhoncus in.
Etiam tempor, est sit amet vulputate molestie, urna neque sodales leo, sit amet
blandit risus felis sed est. Nulla eu eros nec tortor dapibus maximus faucibus
ut erat. Ut pharetra tempor massa in bibendum. Interdum et malesuada fames ac
ante ipsum primis in faucibus. Etiam mattis molestie felis eu efficitur. Morbi
tincidunt consectetur diam tincidunt feugiat. Morbi euismod ut lorem finibus
pellentesque. Aliquam eu porta ex. Aliquam cursus, orci sit amet volutpat
egestas, est est pulvinar erat, sed luctus nisl ligula eget justo vestibulum.”
<ECHOSERVERIP:PORT>
2000 bytes of Lorem Ipsum taken from https://www.lipsum.com/
Compare results from an e1000, a virtio, and a e1000e card:
+--------+-----------+---------+------------+
| Model | Fragment | Segment | Wire Size |
+--------+-----------+---------+------------+
| e1000e | Yes | NO | 1484 + 621 |
+--------+-----------+---------+------------+
| e1000 | No | Yes | 1516 + 620 |
+--------+-----------+---------+------------+
| Virtio | NO | NO | 2068 |
+--------+-----------+---------+------------+
Expected Results:
TCP Segment to proper size OR pass full size to host and let the host split
if necessary.
Configuration changes that did not work:
Disable host, guest, router firewalls
Different Hosts
Different Physical NICs
Libvirt based NAT/Routed modes
Fedora 32 vs 31
Qemu 4.2.0 vs github commit d74824cf7c8b352f9045e949dc636c7207a41eee
System Information:
lsb_release -rd
Description: Fedora release 32 (Thirty Two)
Release: 32
uname -a
Linux pats-laptop-linux 5.7.10-201.fc32.x86_64 #1 SMP Thu Jul 23 00:58:39 UTC
2020 x86_64 x86_64 x86_64 GNU/Linux
I can provide additional logs, debug info, etc. if needed.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1889943/+subscriptions