wtschueller
commented
1 year ago I reviewed the old records I compiled during migration from 5.4 to 5.10. Regarding the packet corruption, my memorization was not quite correct. Corruption occurred for udp packets larger than 4K, not 2K as probably said.
My first test is against kernel 5.10.17 and on the same hardware.
I applied your first patch (larger maxmtu, default threshold).
I compiled bcmgenet as a module and insmod the patched module at runtime.
The following code sends packets slightly above 4K to show the corruption problem.
# only temporarily increase mtu, avoids losing headless connection
sudo ip link set dev eth0 mtu 8000
sudo ethtool -K eth0 tx on
#
# wireshark receives this udp packet with 2 nonzero bytes at 0x1028
dd if=/dev/zero bs=4100 count=1 |netcat -u 169.254.1.1 65000 -q 1
#
# icmp is not affected
ping 169.254.1.1 -c 1 -M do -v -s 4100 -p 0
#
# now repeat without crc offload
sudo ethtool -K eth0 tx off
#
# wireshark receives this udp packet with all zeros as expected
dd if=/dev/zero bs=4100 count=1 |netcat -u 169.254.1.1 65000 -q 1
#
# icmp is not affected
ping 169.254.1.1 -c 1 -M do -v -s 4100 -p 0
#
# back to surely stable state
sudo ip link set dev eth0 mtu 1500My stress test goes like this:
for ((MTU=8192; MTU>2000; ((MTU=MTU-4)) )) do sudo ifconfig eth0 mtu ${MTU} ; ifconfig eth0 ; dd if=/dev/zero bs=65536 count=10 |netcat -u 169.254.1.1 65000 -q 1; doneeth0 freezes as soon as the last packet of the fragments reach approx. 2K and I see the well known time-out with dmesg.
I think I can trigger it even with equally sized packets, I just takes longer.
So this one would be a blocker even for jumbo frame support up to 3840 bytes.
Next steps:
- check for the freeze with other hardware (CM4)
- apply the second patch (increase RBUF_PKT_RDY_THLD) and test rx side.
Simi4
cdalvaro
6by9
Describe the bug
From #5419 (closed PR) where someone had proposed a total hack to increase the max packet length.
Queried on net-dev https://www.spinics.net/lists/netdev/msg919558.html https://www.spinics.net/lists/netdev/msg925029.html So Florian is going to have a little look into it.
Opening new issue to track anything that comes back from it.
Steps to reproduce the behaviour
Current max packet size only allows standard ethernet 1500 byte MTU (+ VLAN headers).
Device (s)
Raspberry Pi 4 Mod. B, Raspberry Pi 400, Raspberry Pi CM4, Raspberry Pi CM4 Lite
System
All kernels to current (6.5)
Logs
No response
Additional context
No response