Messages in this thread | | | Date | Wed, 11 Jun 2008 16:52:55 -0700 (PDT) | Subject | Re: [TCP]: TCP_DEFER_ACCEPT causes leak sockets | From | David Miller <> |
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From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> Date: Wed, 11 Jun 2008 17:57:18 +0400
> Major issue is that tcp_defer_accept_check() manipulates with not locked > listening socket. And from all that I know it is impossible to take > the lock in this context. > > Also I see no accounting for those sockets. With this patch any server, which > set deferred accept, can be flooded with sockets until memory exhausts. > I did not test and would be glad to be mistaken. > > > Issue with locking can be solved by adding a separate spinlock for > manipulations with accept_queue. Apparently, accounting and killing > sockets, which become stale after closing listening socket and > are going to be alive for up to 65535 seconds, also goes under this lock. > > Frankly, cost looks too high for this feature. > > Hiding from accept() sockets with only out-of-order data only > is the only thing which is impossible with old approach. Is this really > so valuable? My opinion: no, this is nothing but a new loophole > to consume memory without control.
Yes, we discussed the locking issue over past few days. See the thread: "stuck localhost TCP connections, v2.6.26-rc3+"
More and more, the arguments are mounting to completely revert the established code path changes, and frankly that is likely what I am going to do by the end of today.
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