Subject: [RFC PATCH] bonding: Do not tx-balance some IPv6 packets on ALB/TLB bonds

From: Vlad Yasevich <[email-masked]>
Date: Fri, 18 Jul 2008 15:38:03 -0400

[ 
  Resending...
  This one seems to have gotten lost in the shuffle, and I'd like hear
  opinions on whether this is the right approach and if anyone else
  has solved this issue.
]

I've been trying to configure IPv6 on ALB and TLB bonds and have found
that there is a 50-50 chance that IPv6 doesn't configure a global address
on such bond.  After further investigation, it appears that DAD probes are
tx-balanced between the bond members.  When the DAD probe is sent on the
secondary device, it ends up arriving back on the primary, since that interface
is also in the multicast group.  As a result, we get a false positive duplicate
address and fail to configure a global IPv6 address.  The easy solution seems
to be to not tx-balance DAD problems.  Also, we should probably not balance
all-note-mulicasts as well since they are the equivalent of IPv4 broadcasts.

-vlad
---

IPv6 all-node-multicasts and DAD probes should not be tx-balanced
on ALB/TLB bonds.  The all-node-multicast is an equivalent to IPv4
broadcasts.  DAD probes have to be sent only on the primary so that
we don't get false-positive detections.

Signed-off-by: Vlad Yasevich <[email-masked]>
---
 drivers/net/bonding/bond_alb.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 5a67372..684440c 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -38,6 +38,7 @@
 #include <linux/in.h>
 #include <net/ipx.h>
 #include <net/arp.h>
+#include <net/ipv6.h>
 #include <asm/byteorder.h>
 #include "bonding.h"
 #include "bond_alb.h"
@@ -81,6 +82,7 @@
 #define RLB_PROMISC_TIMEOUT	10*ALB_TIMER_TICKS_PER_SEC
 
 static const u8 mac_bcast[ETH_ALEN] = {0xff,0xff,0xff,0xff,0xff,0xff};
+static const u8 mac_v6_allmcast[ETH_ALEN] = {0x33,0x33,0x00,0x00,0x00,0x01};
 static const int alb_delta_in_ticks = HZ / ALB_TIMER_TICKS_PER_SEC;
 
 #pragma pack(1)
@@ -1288,6 +1290,7 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
 	u32 hash_index = 0;
 	const u8 *hash_start = NULL;
 	int res = 1;
+	struct ipv6hdr *ip6hdr;
 
 	skb_reset_mac_header(skb);
 	eth_data = eth_hdr(skb);
@@ -1317,11 +1320,32 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
 	}
 		break;
 	case ETH_P_IPV6:
+		/* IPv6 doesn't really use broadcast mac address, but leave
+		 * that here just in case.
+		 */
 		if (memcmp(eth_data->h_dest, mac_bcast, ETH_ALEN) == 0) {
 			do_tx_balance = 0;
 			break;
 		}
 
+		/* IPv6 uses all-nodes multicast as an equivalent to
+		 * broadcasts in IPv4.
+		 */
+		if (memcmp(eth_data->h_dest, mac_v6_allmcast, ETH_ALEN) == 0) {
+			do_tx_balance = 0;
+			break;
+		}
+
+		/* Additianally, DAD probes should not be tx-balanced as that
+		 * will lead to false positives for duplicate addresses and
+		 * prevent address configuration from working.
+		 */
+		ip6hdr = ipv6_hdr(skb);
+		if (ipv6_addr_any(&ip6hdr->saddr)) {
+			do_tx_balance = 0;
+			break;
+		}
+
 		hash_start = (char *)&(ipv6_hdr(skb)->daddr);
 		hash_size = sizeof(ipv6_hdr(skb)->daddr);
 		break;
-- 
1.5.3.5

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