IMHO, "The path MTU is set to the active slave device, not the bonding
master."
Can we set PMTU to bonding master when path MTU is set to the active
slave device?
If not appropriate, you can ignore it.
Best Regards!
Zhu Yanjun
On 01/06/2016 03:06 PM, Wengang Wang wrote:
Hi Yanjun,
Thanks for your review.
Master MTU is same as that for slaves.
Maybe fixing in bonding driver is a good idea, but I don't find a good
place to do that.
Let's go through the simplified follow:
...
1) Fragmentation.
--This is is done is against the bonding master device(device MTU
and path MTU)
2) bond_start_xmit
3) ipoib_start_xmit(slaves are IPoIB interfaces)
For the first send
1) fragment size is 7000(in my case)
2) bond_start_xmit its self is fine
3) ipoib_start_xmit sees the packet size 7000 is larger than the
internal limit 2044, drops the packet and try to update PMTU.
without the patch, it tried update PMTU on slave device(no changes
to master).
the seconds send comes, since no changes happen on bonding
master(PMTU), the fragment size is still 7000 and the behavior is just
the same as the first send.
With the patch, the bonding master PMTU is changed to 2044 after the
first send(hopefully), for the seconds send the fragment size is set
to 2044.
To fix in bonding code, I don't find where we can.
thanks,
wengang
在 2016年01月06日 14:19, zhuyj 写道:
IMHO, this should fix in bonding driver because the active slave mtu
should be the same with the master.
bonding master's mtu is changed to path MTU, then slave dev's MTU
should be changed, too.
Zhu Yanjun
On 01/06/2016 01:49 PM, Wengang Wang wrote:
A problem is found that we are looking for route basing a bonding
device and
deal with path MTU there: The path MTU is set to the active slave
device, not
the bonding master.
The patch tries to fix the issue by letting build_skb_flow_key()
take care
of the transition of device index from bonding slave to the master.
Signed-off-by: Wengang Wang <wen.gang.w...@oracle.com>
---
net/ipv4/route.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 85f184e..3053f10 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -523,11 +523,20 @@ static void build_skb_flow_key(struct flowi4
*fl4, const struct sk_buff *skb,
const struct sock *sk)
{
const struct iphdr *iph = ip_hdr(skb);
- int oif = skb->dev->ifindex;
+ int oif;
+ struct net_device *master = NULL;
+
u8 tos = RT_TOS(iph->tos);
u8 prot = iph->protocol;
u32 mark = skb->mark;
+ if (skb->dev->flags & IFF_SLAVE)
+ master = netdev_master_upper_dev_get(skb->dev);
+ if (master)
+ oif = master->ifindex;
+ else
+ oif = skb->dev->ifindex;
+
__build_flow_key(fl4, sk, iph, oif, tos, prot, mark, 0);
}
--
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