Date: Mon, 7 May 2007 07:52:32 -0700 (PDT) From: Mehul Vora <mehul_freebsd@yahoo.com> To: freebsd-net@freebsd.org Subject: Problem with "rt_check" routine. Message-ID: <93263.30264.qm@web63604.mail.re1.yahoo.com>
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Hi,
Current implementation (Version 6.2) of rt_check() routine defined in route.c is not completely MPSAFE. I found an issue when i started routing with "directisr" enabled. For the first rcvd packet this function initializes rt_gateway of the passed rt_entry. This is done by calling "rtalloc1" routine. But "rt_check" function doesnt hold any lock while calling this function. So incase if we have multiple instances of "ip_input - netisr" running than more than one thread can call this routine which may lead to some corruption, in my case it leads to a dead lock. Problem doesn't happen if before sending heavy traffic a single packet of same kind is sent. But if initially itself heavy traffic is sent than this happens immediately. I have fixed this and it works well after it. Workaround patch for this issue is attached here with. Probably we need to define a macro in route.h for the hardcoded values in the patch. Can any one confirm this ?
Thanks,
Mehul.
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--0-15606975-1178549552=:30264
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Content-Description: 206142780-rt_check.patch.txt
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1260a1261
> try_again:
1280a1282,1289
>
> if(rt0->rt_flags & 0x80000000U){
> /*This rt is under process...*/
> RT_UNLOCK(rt);
> RT_UNLOCK(rt0);
> goto try_again;
> }
>
1281a1291
> rt0->rt_flags |= 0x80000000U;
1288a1299
> rt0->rt_flags &= (~0x80000000U);
--0-15606975-1178549552=:30264--
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