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Message-ID: <Y3+wbPhEAyPIUpbM@t14s.localdomain> Date: Thu, 24 Nov 2022 14:57:00 -0300 From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com> To: Firo Yang <firo.yang@...e.com> Cc: vyasevich@...il.com, nhorman@...driver.com, mkubecek@...e.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, linux-sctp@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, firogm@...il.com Subject: Re: [PATCH 1/1] sctp: sysctl: referring the correct net namespace On Thu, Nov 24, 2022 at 02:29:38PM +0800, Firo Yang wrote: > The 11/23/2022 10:00, Marcelo Ricardo Leitner wrote: > > On Wed, Nov 23, 2022 at 05:44:06PM +0800, Firo Yang wrote: > > > Recently, a customer reported that from their container whose > > > net namespace is different to the host's init_net, they can't set > > > the container's net.sctp.rto_max to any value smaller than > > > init_net.sctp.rto_min. > > > > > > For instance, > > > Host: > > > sudo sysctl net.sctp.rto_min > > > net.sctp.rto_min = 1000 > > > > > > Container: > > > echo 100 > /mnt/proc-net/sctp/rto_min > > > echo 400 > /mnt/proc-net/sctp/rto_max > > > echo: write error: Invalid argument > > > > > > This is caused by the check made from this'commit 4f3fdf3bc59c > > > ("sctp: add check rto_min and rto_max in sysctl")' > > > When validating the input value, it's always referring the boundary > > > value set for the init_net namespace. > > > > > > Having container's rto_max smaller than host's init_net.sctp.rto_min > > > does make sense. Considering that the rto between two containers on the > > > same host is very likely smaller than it for two hosts. > > > > Makes sense. And also, here, it is not using the init_net as > > boundaries for the values themselves. I mean, rto_min in init_net > > won't be the minimum allowed for rto_min in other netns. Ditto for > > rto_max. > > > > More below. > > > > > > > > So to fix this problem, just referring the boundary value from the net > > > namespace where the new input value came from shold be enough. > > > > > > Signed-off-by: Firo Yang <firo.yang@...e.com> > > > --- > > > net/sctp/sysctl.c | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c > > > index b46a416787ec..e167df4dc60b 100644 > > > --- a/net/sctp/sysctl.c > > > +++ b/net/sctp/sysctl.c > > > @@ -429,6 +429,9 @@ static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write, > > > else > > > tbl.data = &net->sctp.rto_min; > > > > > > + if (net != &init_net) > > > + max = net->sctp.rto_max; > > > > This also affects other sysctls: > > > > $ grep -e procname -e extra sysctl.c | grep -B1 extra.*init_net > > .extra1 = SYSCTL_ONE, > > .extra2 = &init_net.sctp.rto_max > > .procname = "rto_max", > > .extra1 = &init_net.sctp.rto_min, > > -- > > .extra1 = SYSCTL_ZERO, > > .extra2 = &init_net.sctp.ps_retrans, > > .procname = "ps_retrans", > > .extra1 = &init_net.sctp.pf_retrans, > > > > And apparently, SCTP is the only one doing such dynamic limits. At > > least in networking. > > > > While the issue you reported is fixable this way, for ps/pf_retrans, > > it is not, as it is using proc_dointvec_minmax() and it will simply > > consume those values (with no netns translation). > > > > So what about patching sctp_sysctl_net_register() instead, to update > > these pointers during netns creation? Right after where it update the > > 'data' one in there: > > > > for (i = 0; table[i].data; i++) > > table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp; > > Thanks Marcelo. It's better. So you mean something like the following? Yes, > > --- a/net/sctp/sysctl.c > +++ b/net/sctp/sysctl.c > @@ -586,6 +586,11 @@ int sctp_sysctl_net_register(struct net *net) > for (i = 0; table[i].data; i++) > table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp; > > +#define SCTP_RTO_MIN_IDX 1 > +#define SCTP_RTO_MAX_IDX 2 But these should be together with the sysctl table definition, so we don't forget to update it later on if needed. > + table[SCTP_RTO_MIN_IDX].extra2 = &net->sctp.rto_max; > + table[SCTP_RTO_MAX_IDX].extra1 = &net->sctp.rto_min; And also the ps/pf_retrans. :-) > + > net->sctp.sysctl_header = register_net_sysctl(net, "net/sctp", table); > if (net->sctp.sysctl_header == NULL) { > kfree(table); > > > > > > Thanks, > > Marcelo > > > > > + > > > ret = proc_dointvec(&tbl, write, buffer, lenp, ppos); > > > if (write && ret == 0) { > > > if (new_value > max || new_value < min) > > > @@ -457,6 +460,9 @@ static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write, > > > else > > > tbl.data = &net->sctp.rto_max; > > > > > > + if (net != &init_net) > > > + min = net->sctp.rto_min; > > > + > > > ret = proc_dointvec(&tbl, write, buffer, lenp, ppos); > > > if (write && ret == 0) { > > > if (new_value > max || new_value < min) > > > -- > > > 2.26.2 > > >
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