On Fri, May 26, 2023 at 05:29:58PM +0300, Vitaliy Makkoveev wrote:
> On Wed, May 17, 2023 at 01:02:58PM +0300, Vitaliy Makkoveev wrote:
> > mrt_rtwalk_mfcsysctl() performs read-only access to protected data, so
> > rtable_walk() could be called with shared netlock.
> >
>
> Regardless on sysctl(2) unlocking backout, the netlock around
> mrt_sysctl_mfc() could be relaxed to shared netlock.
IP multicast is far from MP ready. As a usual workaround I use
exclusive netlock or shared netlock plus kernel lock.
Whenever I have to call something with multicast from a section
that has only shared netlock, I grab the kenrel lock.
So using only NET_LOCK_SHARED() for reading multicast data does not
seem enough.
Look at the way ip_input_if() calls ip_mforward(). Maybe we should
start making ip_mroute.c MP safe. Unfortunately I have no test
environment for that.
bluhm
> > Index: sys/netinet/ip_input.c
> > ===================================================================
> > RCS file: /cvs/src/sys/netinet/ip_input.c,v
> > retrieving revision 1.384
> > diff -u -p -r1.384 ip_input.c
> > --- sys/netinet/ip_input.c 16 May 2023 19:36:00 -0000 1.384
> > +++ sys/netinet/ip_input.c 17 May 2023 09:59:16 -0000
> > @@ -1712,10 +1712,7 @@ ip_sysctl(int *name, u_int namelen, void
> > case IPCTL_MRTMFC:
> > if (newp)
> > return (EPERM);
> > - NET_LOCK();
> > - error = mrt_sysctl_mfc(oldp, oldlenp);
> > - NET_UNLOCK();
> > - return (error);
> > + return (mrt_sysctl_mfc(oldp, oldlenp));
> > case IPCTL_MRTVIF:
> > if (newp)
> > return (EPERM);
> > Index: sys/netinet/ip_mroute.c
> > ===================================================================
> > RCS file: /cvs/src/sys/netinet/ip_mroute.c,v
> > retrieving revision 1.138
> > diff -u -p -r1.138 ip_mroute.c
> > --- sys/netinet/ip_mroute.c 19 Apr 2023 20:03:51 -0000 1.138
> > +++ sys/netinet/ip_mroute.c 17 May 2023 09:59:16 -0000
> > @@ -479,10 +479,12 @@ mrt_sysctl_mfc(void *oldp, size_t *oldle
> > msa.msa_len = *oldlenp;
> > msa.msa_needed = 0;
> >
> > + NET_LOCK_SHARED();
> > for (rtableid = 0; rtableid <= RT_TABLEID_MAX; rtableid++) {
> > rtable_walk(rtableid, AF_INET, NULL, mrt_rtwalk_mfcsysctl,
> > &msa);
> > }
> > + NET_UNLOCK_SHARED();
> >
> > if (msa.msa_minfos != NULL && msa.msa_needed > 0 &&
> > (error = copyout(msa.msa_minfos, oldp, msa.msa_needed)) != 0) {
> >
