[ovs-dev] [PATCH v4] gre: Rename fallback devices to avoid udev's interference

[Yifeng Sun]

Hi Greg,

Sure, thanks for the review. I will work on it.

Yifeng

On Mon, Sep 17, 2018 at 8:49 AM Gregory Rose <gvrose8192 at gmail.com> wrote:

> On 9/15/2018 9:24 PM, Yifeng Sun wrote:
> > On certain kernel versions, when openvswitch kernel module creates
> > a gre0 interface, the kernel’s gre module will jump out and compete
> > to control the gre0 interface. This will cause the failure of
> > openvswitch kernel module loading.
> >
> > This fix renames fallback devices by adding a prefix "ovs-".
> >
> > Signed-off-by: Yifeng Sun <pkusunyifeng at gmail.com>
> > VMware Issue: #2162866
> > ---
> > Please backport this patch to upstream OVS down to 2.9, thanks.
> >
> > v1->v2: Added sanity check for device names, thanks Justin.
> > v2->v3: Fix an indent error.
> > v3->v4: Fix by code review, also fix a potenial bug.
> >
> >   datapath/linux/compat/ip6_gre.c    | 5 +++--
> >   datapath/linux/compat/ip6_tunnel.c | 6 +++---
> >   datapath/linux/compat/ip_gre.c     | 2 +-
> >   datapath/linux/compat/ip_tunnel.c  | 7 +++----
> >   4 files changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/datapath/linux/compat/ip6_gre.c
> b/datapath/linux/compat/ip6_gre.c
> > index 00dbefc9b099..182785273c6f 100644
> > --- a/datapath/linux/compat/ip6_gre.c
> > +++ b/datapath/linux/compat/ip6_gre.c
> > @@ -377,7 +377,7 @@ static struct ip6_tnl *ip6gre_tunnel_locate(struct
> net *net,
> >       if (parms->name[0])
> >               strlcpy(name, parms->name, IFNAMSIZ);
> >       else
> > -             strcpy(name, "ip6gre%d");
> > +             strlcpy(name, "ovs-ip6gre%d", IFNAMSIZ);
> >
> >       dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN,
> >                          ip6gre_tunnel_setup);
> > @@ -1712,7 +1712,8 @@ static int __net_init ip6gre_init_net(struct net
> *net)
> >       struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
> >       int err;
> >
> > -     ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip6_tnl),
> "ip6gre0",
> > +     ign->fb_tunnel_dev = alloc_netdev(sizeof(struct ip6_tnl),
> > +                                       "ovs-ip6gre0",
> >                                         NET_NAME_UNKNOWN,
> >                                         ip6gre_tunnel_setup);
> >       if (!ign->fb_tunnel_dev) {
> > diff --git a/datapath/linux/compat/ip6_tunnel.c
> b/datapath/linux/compat/ip6_tunnel.c
> > index 56fd8b4dd342..9f4bae7dd3d1 100644
> > --- a/datapath/linux/compat/ip6_tunnel.c
> > +++ b/datapath/linux/compat/ip6_tunnel.c
> > @@ -355,7 +355,7 @@ static struct ip6_tnl *ip6_tnl_create(struct net
> *net, struct __ip6_tnl_parm *p)
> >       if (p->name[0])
> >               strlcpy(name, p->name, IFNAMSIZ);
> >       else
> > -             sprintf(name, "ip6tnl%%d");
> > +             strlcpy(name, "ovs-ip6tnl%d", IFNAMSIZ);
> >
> >       dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN,
> >                          ip6_tnl_dev_setup);
> > @@ -1410,7 +1410,7 @@ ip6_tnl_parm_to_user(struct ip6_tnl_parm *u, const
> struct __ip6_tnl_parm *p)
> >    *     %SIOCCHGTUNNEL: change tunnel parameters to those given
> >    *     %SIOCDELTUNNEL: delete tunnel
> >    *
> > - *   The fallback device "ip6tnl0", created during module
> > + *   The fallback device "ovs-ip6tnl0", created during module
> >    *   initialization, can be used for creating other tunnel devices.
> >    *
> >    * Return:
> > @@ -2093,7 +2093,7 @@ static int __net_init ip6_tnl_init_net(struct net
> *net)
> >       ip6n->tnls[1] = ip6n->tnls_r_l;
> >
> >       err = -ENOMEM;
> > -     ip6n->fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6tnl0",
> > +     ip6n->fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl),
> "ovs-ip6tnl0",
> >                                       NET_NAME_UNKNOWN,
> ip6_tnl_dev_setup);
> >
> >       if (!ip6n->fb_tnl_dev)
> > diff --git a/datapath/linux/compat/ip_gre.c
> b/datapath/linux/compat/ip_gre.c
> > index 05132ba9494a..b7322c58e420 100644
> > --- a/datapath/linux/compat/ip_gre.c
> > +++ b/datapath/linux/compat/ip_gre.c
> > @@ -1463,7 +1463,7 @@ static struct pernet_operations erspan_net_ops = {
> >
> >   static int __net_init ipgre_tap_init_net(struct net *net)
> >   {
> > -     return ip_tunnel_init_net(net, gre_tap_net_id, &ipgre_tap_ops,
> "gretap0");
> > +     return ip_tunnel_init_net(net, gre_tap_net_id, &ipgre_tap_ops,
> "ovs-gretap0");
> >   }
> >
> >   static void __net_exit ipgre_tap_exit_net(struct net *net)
> > diff --git a/datapath/linux/compat/ip_tunnel.c
> b/datapath/linux/compat/ip_tunnel.c
> > index d16e60fbfef0..ae5d5a058663 100644
> > --- a/datapath/linux/compat/ip_tunnel.c
> > +++ b/datapath/linux/compat/ip_tunnel.c
> > @@ -130,12 +130,11 @@ static struct net_device
> *__ip_tunnel_create(struct net *net,
> >       if (parms->name[0])
> >               strlcpy(name, parms->name, IFNAMSIZ);
> >       else {
> > -             if (strlen(ops->kind) > (IFNAMSIZ - 3)) {
> > +             err = snprintf(name, IFNAMSIZ - 3, "ovs-%s%%d", ops->kind);
> > +             if (err >= IFNAMSIZ - 3)
> >                       err = -E2BIG;
> > +             if (err < 0)
> >                       goto failed;
> > -             }
> > -             strlcpy(name, ops->kind, IFNAMSIZ);
> > -             strncat(name, "%d", 2);
> >       }
> >
> >       ASSERT_RTNL();
>
> Thanks Yifeng for all your work on this.
>
> This looks OK but I'm not sure the additional protections against a
> device name being too long are
> really needed.  I think in all cases the parms->name will be filled out
> since OVS is the only user.
> Have you tested whether the else code path will ever be entered?
> Sometimes kernel code gets
> into our backports even though it would never be executed within the
> context of OVS.  It would
> be good to check this.
>
> Thanks,
>
> - Greg
>