Thu, Jan 21, 2016 at 06:32:58AM CET, wen.gang.w...@oracle.com wrote:
>In a bonding setting, we determines fragment size according to MTU and
>PMTU associated to the bonding master. If the slave finds the fragment
>size is too big, it drops the fragment and calls ip_rt_update_pmtu(),
>passing _skb_ and _pmtu_, trying to update the path MTU.
>Problem is that the target device that function ip_rt_update_pmtu actually
>tries to update is the slave (skb->dev), not the master. Thus since no
>PMTU change happens on master, the fragment size for later packets doesn't
>change so all later fragments/packets are dropped too.
>
>The fix is letting build_skb_flow_key() take care of the transition of
>device index from bonding slave to the master. That makes the master become
>the target device that ip_rt_update_pmtu tries to update PMTU to.
>
>Signed-off-by: Wengang Wang <wen.gang.w...@oracle.com>
>---
> net/ipv4/route.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
>diff --git a/net/ipv4/route.c b/net/ipv4/route.c
>index 85f184e..7e766b5 100644
>--- a/net/ipv4/route.c
>+++ b/net/ipv4/route.c
>@@ -524,10 +524,19 @@ static void build_skb_flow_key(struct flowi4 *fl4, const
>struct sk_buff *skb,
> {
> const struct iphdr *iph = ip_hdr(skb);
> int oif = skb->dev->ifindex;
>+ struct net_device *master;
> u8 tos = RT_TOS(iph->tos);
> u8 prot = iph->protocol;
> u32 mark = skb->mark;
>
>+ if (netif_is_bond_slave(skb->dev)) {
>+ rcu_read_lock();
>+ master = netdev_master_upper_dev_get_rcu(skb->dev);
>+ if (master)
>+ oif = master->ifindex;
>+ rcu_read_unlock();
>+ }
This is certainly not correct as it should not be bond-specific but
rather generic. Note that you may have bond over bond or bridge over
bond or other scenarios, which this patch ignores.
