SMB server listener stops after a SYN-ACK flood
Data from the customer indicates the server was exiting after the TCP 3-way handshake. As such this is an
ECONNABORTED (error # 130 - see customers notes below.) Rather than try to restart for any
ksocket_accept() error returned, it's probably safer to only try to restart if the server exits due to this one error.
Good news, I spoke to the tester who was running the nessus test and he said that he has seen the
ksocket_accept fail before. (we have added some logging to the
smb_server_listener so it will print something in the log when the ksocket_socket accept fails).
He was able to cause the
smb_server_listener thread to exit when running a performance test. The return code from
ksocket_accept is 130.
I checked mdb and the confirmed that the following thread is not running anymore:
ffffff0030d9fc40 fffffffffbc2e3c0 0 0 60 ffffff07273785f0 PC: _resume_from_idle+0xf4 THREAD: smb_thread_entry_point() stack pointer for thread ffffff0030d9fc40: ffffff0030d9f900 [ ffffff0030d9f900 _resume_from_idle+0xf4() ] swtch+0x145() cv_wait+0x61() cv_wait_sig_swap_core+0x2aa() cv_wait_sig_swap+0x18() so_acceptq_dequeue_locked+0x63() so_acceptq_dequeue+0x40() so_accept+0x9a() socket_accept+0x22() ksocket_accept+0x116() smb_server_listener+0x12d() smb_thread_entry_point+0x51() thread_start+8()
The test involves simulating very high SMB2 tree connections ( 20,000 per second) using SwiftTest. It doesn’t happen every time, but if we run it 2-3 times we will see the issue.
Updated by Gordon Ross 5 months ago
The fix restarts the listener in the case of an ECONNABORTED which results from TCP SYN-ACK flood. Previously, if the listener exited due to this it would not restart.
Testing: Simulate SYN/ACK flood (and SwiftTest at the customer)
Fix in production since mid 2016
Updated by Electric Monk 5 months ago
- Status changed from In Progress to Closed
- % Done changed from 0 to 100
commit 41bd85101cd90603ab3220d835461fe851a81fed Author: kcrowenex <email@example.com> Date: 2019-05-19T23:21:13.000Z 10969 SMB server listener stops after a SYN-ACK flood Reviewed by: Gordon Ross <firstname.lastname@example.org> Reviewed by: Matt Barden <email@example.com> Approved by: Joshua M. Clulow <firstname.lastname@example.org>