* [PATCH] : bug fix in multipath drr code.
@ 2005-05-23 12:26 pravin
2005-05-23 23:22 ` Herbert Xu
0 siblings, 1 reply; 6+ messages in thread
From: pravin @ 2005-05-23 12:26 UTC (permalink / raw)
To: netdev; +Cc: David S. Miller, Herbert Xu
[-- Attachment #1: Type: text/plain, Size: 786 bytes --]
hi
AFAIU, there is a race condition in multipath_drr code,
these code paths try to access & change last_selection variable
without any synchronization.
Please correct me if I am wrong.
Code Path - 1
__ip_route_output_key(...)
{
...
calls drr_select_route
if(FLOWI_FLAG_MULTIPATHOLDROUTE set){
check last_selection.
return last_selection //so it can return NULL pointer
}
....
}
Code Path - 2
rt_secret_rebuild()
{
.....
rt_run_flush(..);
->rt_free(rth);
-> multipath_remove(rt)
->drr_remove()
reset last_selection.
....
}
Attached patch also fixes bug in function drr_init ::
multipath_alg_register(..) is called with wrong algorithm ID.
Regards
Pravin.
[-- Attachment #2: multipath-last_selection-race-fix.patch --]
[-- Type: text/x-patch, Size: 1913 bytes --]
Signed-off by: Pravin B. Shelar <pravins@calsoftinc.com>
Index: linux-2.6.12-rc4/net/ipv4/multipath_drr.c
===================================================================
--- linux-2.6.12-rc4.orig/net/ipv4/multipath_drr.c 2005-05-06 22:20:31.000000000 -0700
+++ linux-2.6.12-rc4/net/ipv4/multipath_drr.c 2005-05-22 06:41:39.000000000 -0700
@@ -145,11 +145,13 @@
int cur_min_devidx = -1;
/* if necessary and possible utilize the old alternative */
- if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
- last_selection != NULL) {
- result = last_selection;
- *rp = result;
- return;
+ if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 ) {
+ struct rtable *last_result = last_selection;
+ if(last_result != NULL &&
+ multipath_comparekeys(&last_result->fl, flp)) {
+ *rp = last_result;
+ return;
+ }
}
/* 1. make sure all alt. nexthops have the same GC related data */
@@ -244,7 +246,7 @@
if (err)
return err;
- err = multipath_alg_register(&drr_ops, IP_MP_ALG_RR);
+ err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR);
if (err)
goto fail;
Index: linux-2.6.12-rc4/net/ipv4/multipath_rr.c
===================================================================
--- linux-2.6.12-rc4.orig/net/ipv4/multipath_rr.c 2005-05-06 22:20:31.000000000 -0700
+++ linux-2.6.12-rc4/net/ipv4/multipath_rr.c 2005-05-22 06:41:20.000000000 -0700
@@ -64,10 +64,13 @@
int min_use = -1;
/* if necessary and possible utilize the old alternative */
- if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
- last_used != NULL) {
- result = last_used;
- goto out;
+ if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 ) {
+ struct rtable *last_result = last_used;
+ if(last_result != NULL &&
+ multipath_comparekeys(&last_result->fl, flp)) {
+ result = last_result;
+ goto out;
+ }
}
/* 1. make sure all alt. nexthops have the same GC related data
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] : bug fix in multipath drr code. 2005-05-23 12:26 [PATCH] : bug fix in multipath drr code pravin @ 2005-05-23 23:22 ` Herbert Xu 2005-05-24 6:46 ` pravin b shelar 0 siblings, 1 reply; 6+ messages in thread From: Herbert Xu @ 2005-05-23 23:22 UTC (permalink / raw) To: pravin; +Cc: netdev, David S. Miller On Mon, May 23, 2005 at 05:56:39PM +0530, pravin wrote: > AFAIU, there is a race condition in multipath_drr code, > these code paths try to access & change last_selection variable > without any synchronization. Yes you're right. > Index: linux-2.6.12-rc4/net/ipv4/multipath_drr.c > =================================================================== > --- linux-2.6.12-rc4.orig/net/ipv4/multipath_drr.c 2005-05-06 22:20:31.000000000 -0700 > +++ linux-2.6.12-rc4/net/ipv4/multipath_drr.c 2005-05-22 06:41:39.000000000 -0700 > @@ -145,11 +145,13 @@ > int cur_min_devidx = -1; > > /* if necessary and possible utilize the old alternative */ > - if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 && > - last_selection != NULL) { > - result = last_selection; > - *rp = result; > - return; > + if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 ) { > + struct rtable *last_result = last_selection; > + if(last_result != NULL && > + multipath_comparekeys(&last_result->fl, flp)) { > + *rp = last_result; > + return; > + } > } You don't need all this code. All you need to do is do result = last_selection before the if condition and then check result in the if condition instead of last_selection. The multipath_comparekeys isn't necessary either. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] : bug fix in multipath drr code. 2005-05-23 23:22 ` Herbert Xu @ 2005-05-24 6:46 ` pravin b shelar 2005-05-24 7:11 ` Herbert Xu 0 siblings, 1 reply; 6+ messages in thread From: pravin b shelar @ 2005-05-24 6:46 UTC (permalink / raw) To: Herbert Xu; +Cc: netdev, David S. Miller Herbert Xu wrote: >On Mon, May 23, 2005 at 05:56:39PM +0530, pravin wrote: > > >> /* if necessary and possible utilize the old alternative */ >>- if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 && >>- last_selection != NULL) { >>- result = last_selection; >>- *rp = result; >>- return; >>+ if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 ) { >>+ struct rtable *last_result = last_selection; >>+ if(last_result != NULL && >>+ multipath_comparekeys(&last_result->fl, flp)) { >>+ *rp = last_result; >>+ return; >>+ } >> } >> >> > >You don't need all this code. All you need to do is do >result = last_selection before the if condition and then >check result in the if condition instead of last_selection. > >The multipath_comparekeys isn't necessary either. > > > In concurrent invocations of drr_select_route() last_selection will change to different route. So in that case we can not use last_selection route on basis of FLOWI_FLAG_MULTIPATHOLDROUTE flag only, since old route might be totally different due another invocation of same function. So, I think multipath_comparekeys is necessary. Please correct me if I am wrong. Regards, Pravin. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] : bug fix in multipath drr code. 2005-05-24 6:46 ` pravin b shelar @ 2005-05-24 7:11 ` Herbert Xu 2005-05-24 9:57 ` pravin b shelar 0 siblings, 1 reply; 6+ messages in thread From: Herbert Xu @ 2005-05-24 7:11 UTC (permalink / raw) To: pravin b shelar; +Cc: netdev, David S. Miller On Tue, May 24, 2005 at 12:16:38PM +0530, pravin b shelar wrote: > > >The multipath_comparekeys isn't necessary either. > > In concurrent invocations of drr_select_route() last_selection will > change to different route. > So in that case we can not use last_selection route on basis of > FLOWI_FLAG_MULTIPATHOLDROUTE flag only, since old > route might be totally different due another invocation of same function. > So, I think multipath_comparekeys is necessary. Indeed. In fact this whole MULTIPATHOLDROUTE thing can't possibly work at all. I'd suggest that it be removed. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] : bug fix in multipath drr code. 2005-05-24 7:11 ` Herbert Xu @ 2005-05-24 9:57 ` pravin b shelar 2005-05-26 22:13 ` David S. Miller 0 siblings, 1 reply; 6+ messages in thread From: pravin b shelar @ 2005-05-24 9:57 UTC (permalink / raw) To: Herbert Xu; +Cc: netdev, David S. Miller [-- Attachment #1: Type: text/plain, Size: 379 bytes --] Herbert Xu wrote: >On Tue, May 24, 2005 at 12:16:38PM +0530, pravin b shelar wrote: > > >In fact this whole MULTIPATHOLDROUTE thing can't possibly >work at all. I'd suggest that it be removed. > > So I think we should ignore MULTIPATHOLDROUTE flag in drr and rr multipath algorithms as done in random multipath algorithm. Attached patch does same thing. Regards, Pravin. [-- Attachment #2: multipath-drr_rr-last_use-fix.patch --] [-- Type: text/x-patch, Size: 3512 bytes --] Signed-off by: Pravin B. Shelar <pravins@calsoftinc.com> Index: linux-2.6.12-rc4/include/net/route.h =================================================================== --- linux-2.6.12-rc4.orig/include/net/route.h 2005-05-06 22:20:31.000000000 -0700 +++ linux-2.6.12-rc4/include/net/route.h 2005-05-24 02:37:10.000000000 -0700 @@ -181,9 +181,6 @@ memcpy(&fl, &(*rp)->fl, sizeof(fl)); fl.fl_ip_sport = sport; fl.fl_ip_dport = dport; -#if defined(CONFIG_IP_ROUTE_MULTIPATH_CACHED) - fl.flags |= FLOWI_FLAG_MULTIPATHOLDROUTE; -#endif ip_rt_put(*rp); *rp = NULL; return ip_route_output_flow(rp, &fl, sk, 0); Index: linux-2.6.12-rc4/net/ipv4/multipath_drr.c =================================================================== --- linux-2.6.12-rc4.orig/net/ipv4/multipath_drr.c 2005-05-06 22:20:31.000000000 -0700 +++ linux-2.6.12-rc4/net/ipv4/multipath_drr.c 2005-05-24 02:37:10.000000000 -0700 @@ -57,7 +57,6 @@ static struct multipath_device state[MULTIPATH_MAX_DEVICECANDIDATES]; static DEFINE_SPINLOCK(state_lock); -static struct rtable *last_selection = NULL; static int inline __multipath_findslot(void) { @@ -111,11 +110,6 @@ .notifier_call = drr_dev_event, }; -static void drr_remove(struct rtable *rt) -{ - if (last_selection == rt) - last_selection = NULL; -} static void drr_safe_inc(atomic_t *usecount) { @@ -144,14 +138,6 @@ int devidx = -1; int cur_min_devidx = -1; - /* if necessary and possible utilize the old alternative */ - if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 && - last_selection != NULL) { - result = last_selection; - *rp = result; - return; - } - /* 1. make sure all alt. nexthops have the same GC related data */ /* 2. determine the new candidate to be returned */ result = NULL; @@ -229,12 +215,10 @@ } *rp = result; - last_selection = result; } static struct ip_mp_alg_ops drr_ops = { .mp_alg_select_route = drr_select_route, - .mp_alg_remove = drr_remove, }; static int __init drr_init(void) @@ -244,7 +228,7 @@ if (err) return err; - err = multipath_alg_register(&drr_ops, IP_MP_ALG_RR); + err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR); if (err) goto fail; Index: linux-2.6.12-rc4/net/ipv4/multipath_rr.c =================================================================== --- linux-2.6.12-rc4.orig/net/ipv4/multipath_rr.c 2005-05-06 22:20:31.000000000 -0700 +++ linux-2.6.12-rc4/net/ipv4/multipath_rr.c 2005-05-24 02:37:10.000000000 -0700 @@ -47,29 +47,12 @@ #include <net/checksum.h> #include <net/ip_mp_alg.h> -#define MULTIPATH_MAX_CANDIDATES 40 - -static struct rtable* last_used = NULL; - -static void rr_remove(struct rtable *rt) -{ - if (last_used == rt) - last_used = NULL; -} - static void rr_select_route(const struct flowi *flp, struct rtable *first, struct rtable **rp) { struct rtable *nh, *result, *min_use_cand = NULL; int min_use = -1; - /* if necessary and possible utilize the old alternative */ - if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 && - last_used != NULL) { - result = last_used; - goto out; - } - /* 1. make sure all alt. nexthops have the same GC related data * 2. determine the new candidate to be returned */ @@ -90,15 +73,12 @@ if (!result) result = first; -out: - last_used = result; result->u.dst.__use++; *rp = result; } static struct ip_mp_alg_ops rr_ops = { .mp_alg_select_route = rr_select_route, - .mp_alg_remove = rr_remove, }; static int __init rr_init(void) ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] : bug fix in multipath drr code. 2005-05-24 9:57 ` pravin b shelar @ 2005-05-26 22:13 ` David S. Miller 0 siblings, 0 replies; 6+ messages in thread From: David S. Miller @ 2005-05-26 22:13 UTC (permalink / raw) To: pravins; +Cc: herbert, netdev From: pravin b shelar <pravins@calsoftinc.com> Date: Tue, 24 May 2005 15:27:16 +0530 > So I think we should ignore MULTIPATHOLDROUTE flag > in drr and rr multipath algorithms as done in random multipath algorithm. > > Attached patch does same thing. I've applied this patch, thanks. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2005-05-26 22:13 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2005-05-23 12:26 [PATCH] : bug fix in multipath drr code pravin 2005-05-23 23:22 ` Herbert Xu 2005-05-24 6:46 ` pravin b shelar 2005-05-24 7:11 ` Herbert Xu 2005-05-24 9:57 ` pravin b shelar 2005-05-26 22:13 ` David S. Miller
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