Re: DoS attack against TCP services

[christos%zoulas.com@localhost (Christos Zoulas)]

On Mar 12, 12:20pm, hannken%eis.cs.tu-bs.de@localhost ("J. Hannken-Illjes") wrote:
-- Subject: Re: DoS attack against TCP services

| Now we have a deadlock, softlck/0 waits for the mutex and therefore
| callouts will no longer be processed and ciss holds the mutex and waits
| for a callout through cv_timedwait.

Thanks for looking into it! Part of the ciss_ioctl_vol() (the pdid part)
does things with XS_CTL_POLL so that it does not involve any mutexes. It
would be simple to change the ldid part to do the same. Should we do that?

| Taking a closer look at the poll loop from sys/dev/ic/ciss.c:537 ... this
| code looks wrong in many aspects:
| 
| - Sleeping up to 60 seconds in a function used by a callout is wrong.

Yes, but many disk drivers seem to violate that. How do we fix this?
Making a separate thread that updates statistics for each driver seems
suboptimal?

| - Examining variables here we get: tick =3D 10000, etick =3D 16000,
|   tohz =3D 6000 and i =3D 5999999.  As tick is constant (us per hz)
|   this loop might run for 5999999*60 seconds!

I committed a fix for this. Now it should only sleep up to 60 seconds.

christos