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Jakub reported that ASSERT_EQ(cpu, i) in so_incoming_cpu.c seems to
fire somewhat randomly.
# # RUN so_incoming_cpu.before_reuseport.test3 ...
# # so_incoming_cpu.c:191:test3:Expected cpu (32) == i (0)
# # test3: Test terminated by assertion
# # FAIL so_incoming_cpu.before_reuseport.test3
# not ok 3 so_incoming_cpu.before_reuseport.test3
When the test failed, not-yet-accepted CLOSE_WAIT sockets received
SYN with a "challenging" SEQ number, which was sent from an unexpected
CPU that did not create the receiver.
The test basically does:
1. for each cpu:
1-1. create a server
1-2. set SO_INCOMING_CPU
2. for each cpu:
2-1. set cpu affinity
2-2. create some clients
2-3. let clients connect() to the server on the same cpu
2-4. close() clients
3. for each server:
3-1. accept() all child sockets
3-2. check if all children have the same SO_INCOMING_CPU with the server
The root cause was the close() in 2-4. and net.ipv4.tcp_tw_reuse.
In a loop of 2., close() changed the client state to FIN_WAIT_2, and
the peer transitioned to CLOSE_WAIT.
In another loop of 2., connect() happened to select the same port of
the FIN_WAIT_2 socket, and it was reused as the default value of
net.ipv4.tcp_tw_reuse is 2.
As a result, the new client sent SYN to the CLOSE_WAIT socket from
a different CPU, and the receiver's sk_incoming_cpu was overwritten
with unexpected CPU ID.
Also, the SYN had a different SEQ number, so the CLOSE_WAIT socket
responded with Challenge ACK. The new client properly returned RST
and effectively killed the CLOSE_WAIT socket.
This way, all clients were created successfully, but the error was
detected later by 3-2., ASSERT_EQ(cpu, i).
To avoid the failure, let's make sure that (i) the number of clients
is less than the number of available ports and (ii) such reuse never
happens.
Fixes:
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| .. | ||
| accounting | ||
| arch | ||
| bootconfig | ||
| bpf | ||
| build | ||
| certs | ||
| cgroup | ||
| counter | ||
| crypto | ||
| debugging | ||
| edid | ||
| firewire | ||
| firmware | ||
| gpio | ||
| hv | ||
| iio | ||
| include | ||
| kvm/kvm_stat | ||
| laptop | ||
| leds | ||
| lib | ||
| memory-model | ||
| mm | ||
| net/ynl | ||
| objtool | ||
| pci | ||
| pcmcia | ||
| perf | ||
| power | ||
| rcu | ||
| scripts | ||
| spi | ||
| testing | ||
| thermal | ||
| time | ||
| tracing | ||
| usb | ||
| verification | ||
| virtio | ||
| wmi | ||
| workqueue | ||
| Makefile | ||