[linux-cifs-client] RE: SYN_RECV flood

Nick Millington Nick.Millington at sonos.com
Fri Jun 25 23:45:29 GMT 2004


I have reproduced the SYN flood problem here as one of the symptoms of
the problem I sent mail about last week with multiple connections to a
CIFS server from different users.  The infinite loop that I described in
the mail titled "signals sent to cifsd threads" attempts to open a TCP
connection to the file server on each iteration of the loop, which
causes the SYN flood.
 
The root of the problem here was that SIGKILL was being sent to the
cifsd thread, which caused EINTR to be returned from sock_recvmsg.
Since EINTR wasn't handled, the signal remained pending forever, causing
the infinite loop.  Steve French's checkins over the last week address
the two cases I knew of where the SIGKILL would be inappropriately sent,
and it looks like he also fixed it so cifsd handles EINTR without going
into an infinite loop.  
 
I haven't picked up Steve's fixes yet but I had roughly equivalent fixes
here that resolved my SYN flood issues.  So I should think his fixes
will make your problem go away too.
 
Nick
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