From: Brad Peters <bpeters@redhat.com>
Date: Wed, 27 Aug 2008 17:12:58 -0400
Subject: [net] ibmveth: cluster membership problems
Message-id: 20080827211258.2328.51933.sendpatchset@squad5-lp1.lab.bos.redhat.com
O-Subject: [PATCH RHEL5.3 bz460379] Cluster membership problem with RHEL 5.2
Bugzilla: 460379
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>
RH-Acked-by: David Howells <dhowells@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=460379

Description:
===========
A two node cluster was configured using two LPARs on a p520 System P machine
using RHEL 5.1 and manual fencing. Both nodes were able to establish quorum and
a cluster.

Using a RHEl5.2 install and the same configuration, the nodes were unable to establish quarum.

The patch fixes a ibmveth bug where bad UDP checksums are being transmitted
when checksum offloading is enabled

RHEL Version Found:
================
RHEL 5.2

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1442223

Upstream Status:
================
Committed:
http://marc.info/?l=linux-netdev&m=121982996130142&w=2

Test Status:
============
This was tested on a -104 kernel, showing
both nodes joined the cluster successfully:

Cluster Status for test_01 @ Mon Aug 18 08:03:07 2008
Member Status: Quorate

 Member Name                             ID   Status
 ------ ----                             ---- ------
 idsc1.ltc.austin.ibm.com                    1 Online, Local
 idsc2.ltc.austin.ibm.com                    2 Online

wireshark trace shows the receipt of udp packets from the other node containing
valid checksums.

===============================================================

Brad Peters 1-978-392-1000 x 23183
IBM on-site partner.

Proposed Patch:
===============
This patch is based on 2.6.18-104.el5

diff --git a/drivers/net/ibmveth.c b/drivers/net/ibmveth.c
index 25b59ae..3c40c46 100644
--- a/drivers/net/ibmveth.c
+++ b/drivers/net/ibmveth.c
@@ -846,8 +846,6 @@ static int ibmveth_start_xmit(struct sk_buff *skb, struct net_device *netdev)
 	unsigned int tx_map_failed = 0;
 
 	desc.fields.flags_len = IBMVETH_BUF_VALID | skb->len;
-	desc.fields.address = dma_map_single(&adapter->vdev->dev, skb->data,
-					     skb->len, DMA_TO_DEVICE);
 
 	if (skb->ip_summed == CHECKSUM_HW &&
 	    skb->nh.iph->protocol != IPPROTO_TCP && skb_checksum_help(skb, 0)) {
@@ -866,6 +864,8 @@ static int ibmveth_start_xmit(struct sk_buff *skb, struct net_device *netdev)
 		buf[1] = 0;
 	}
 
+	desc.fields.address = dma_map_single(&adapter->vdev->dev, skb->data,
+					     skb->len, DMA_TO_DEVICE);
 	if (dma_mapping_error(desc.fields.address)) {
 		ibmveth_error_printk("tx: unable to map xmit buffer\n");
 		tx_map_failed++;