On 12/31/17 9:15 AM, Ido Schimmel wrote:
> By default, IPv6 deletes nexthops from a multipath route when the
> nexthop device is put administratively down. This differs from IPv4
> where the nexthops are kept, but marked with the RTNH_F_DEAD flag. A
> multipath route is flushed when all of its nexthops become dead.
>
> Align IPv6 with IPv4 and have it conform to the same guidelines.
>
> In case the multipath route needs to be flushed, its siblings are
> flushed one by one. Otherwise, the nexthops are marked with the
> appropriate flags and the tree walker is instructed to skip all the
> siblings.
>
> As explained in previous patches, care is taken to update the sernum of
> the affected tree nodes, so as to prevent the use of wrong dst entries.
>
> Signed-off-by: Ido Schimmel <ido...@mellanox.com>
> ---
> net/ipv6/route.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 46 insertions(+), 7 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index ab95e07b5e74..9b142eb83f3c 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -3486,8 +3486,10 @@ static int fib6_ifup(struct rt6_info *rt, void *p_arg)
> const struct arg_netdev_event *arg = p_arg;
> const struct net *net = dev_net(arg->dev);
>
> - if (rt != net->ipv6.ip6_null_entry && rt->dst.dev == arg->dev)
> + if (rt != net->ipv6.ip6_null_entry && rt->dst.dev == arg->dev) {
> rt->rt6i_nh_flags &= ~arg->nh_flags;
> + fib6_update_sernum_upto_root(dev_net(rt->dst.dev), rt);
> + }
>
> return 0;
> }
> @@ -3528,6 +3530,35 @@ static void rt6_multipath_flush(struct rt6_info *rt)
> iter->should_flush = 1;
> }
>
> +static unsigned int rt6_multipath_dead_count(const struct rt6_info *rt,
> + const struct net_device *down_dev)
> +{
> + struct rt6_info *iter;
> + unsigned int dead = 0;
> +
> + if (rt->dst.dev == down_dev || rt->rt6i_nh_flags & RTNH_F_DEAD)
> + dead++;
> + list_for_each_entry(iter, &rt->rt6i_siblings, rt6i_siblings)
> + if (iter->dst.dev == down_dev ||
> + iter->rt6i_nh_flags & RTNH_F_DEAD)
> + dead++;
> +
> + return dead;
> +}
> +
> +static void rt6_multipath_nh_flags_set(struct rt6_info *rt,
> + const struct net_device *dev,
> + unsigned int nh_flags)
> +{
> + struct rt6_info *iter;
> +
> + if (rt->dst.dev == dev)
> + rt->rt6i_nh_flags |= nh_flags;
> + list_for_each_entry(iter, &rt->rt6i_siblings, rt6i_siblings)
> + if (iter->dst.dev == dev)
> + iter->rt6i_nh_flags |= nh_flags;
> +}
> +
> /* called with write lock held for table with rt */
> static int fib6_ifdown(struct rt6_info *rt, void *p_arg)
> {
> @@ -3550,13 +3581,21 @@ static int fib6_ifdown(struct rt6_info *rt, void
> *p_arg)
> }
> return -2;
> case NETDEV_DOWN:
> - if (rt->dst.dev != dev)
> - break;
> - if (rt->rt6i_nsiblings == 0 ||
> - !rt->rt6i_idev->cnf.ignore_routes_with_linkdown)
> + if (rt->should_flush)
> return -1;
> - rt->rt6i_nh_flags |= (RTNH_F_DEAD | RTNH_F_LINKDOWN);
> - break;
> + if (!rt->rt6i_nsiblings)
> + return rt->dst.dev == dev ? -1 : 0;
> + if (rt6_multipath_uses_dev(rt, dev)) {
> + if (rt->rt6i_nsiblings + 1 ==
> + rt6_multipath_dead_count(rt, dev)) {
I'd prefer a tmp variable to make that line more readable and still
within the 80 column guideline.
unsigned int count;
count = rt6_multipath_dead_count(rt, dev);
if (rt->rt6i_nsiblings + 1 == count) {
> + rt6_multipath_flush(rt);
> + return -1;
> + }
> + rt6_multipath_nh_flags_set(rt, dev, RTNH_F_DEAD |
> + RTNH_F_LINKDOWN);
> + fib6_update_sernum(rt);
> + }
> + return -2;
> case NETDEV_CHANGE:
> if (rt->dst.dev != dev ||
> rt->rt6i_flags & (RTF_LOCAL | RTF_ANYCAST))
>
